tty: Don't include tty_buffer.h in tty.h

There's no need to include linux/tty_buffer.h in linux/tty.h.
Move the include into tty_buffer.c that is actually using it.

Signed-off-by: Ilpo Järvinen <ilpo.jarvinen@linux.intel.com>
Link: https://lore.kernel.org/r/20240215111538.1920-1-ilpo.jarvinen@linux.intel.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

tty: add new helper function tty_get_tiocm

There is no in-kernel function to get the status register of a tty device
like the TIOCMGET ioctl returns to userspace. Create a new function,
tty_get_tiocm(), to obtain the status register that other portions of the
kernel can call if they need this information, and move the existing
internal tty_tiocmget() function to use this interface.

Signed-off-by: Florian Eckert <fe@dev.tdt.de>
Reviewed-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Link: https://lore.kernel.org/r/20231127110311.3583957-2-fe@dev.tdt.de
Signed-off-by: Lee Jones <lee@kernel.org>

tty: core: the rest to u8

There are still last minor users in the tty core that still reference
characters by the 'char' type. Switch them to u8.

Signed-off-by: "Jiri Slaby (SUSE)" <jirislaby@kernel.org>
Link: https://lore.kernel.org/r/20231206073712.17776-6-jirislaby@kernel.org
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

tty: make tty_operations::send_xchar accept u8 char

tty_operations::send_xchar is one of the last users of 'char' type for
characters in the tty layer. Convert it to u8 now.

Signed-off-by: "Jiri Slaby (SUSE)" <jirislaby@kernel.org>
Cc: Karsten Keil <isdn@linux-pingi.de>
Cc: Ulf Hansson <ulf.hansson@linaro.org>
Cc: Marcel Holtmann <marcel@holtmann.org>
Cc: Johan Hedberg <johan.hedberg@gmail.com>
Cc: Luiz Augusto von Dentz <luiz.dentz@gmail.com>
Cc: netdev@vger.kernel.org
Cc: linux-mmc@vger.kernel.org
Cc: linux-bluetooth@vger.kernel.org
Reviewed-by: Geert Uytterhoeven <geert@linux-m68k.org>
Link: https://lore.kernel.org/r/20231206073712.17776-5-jirislaby@kernel.org
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

tty: make tty const in tty_get_baud_rate()

After commit 87888fb9ac0c ("tty: Remove baudrate dead code & make
ktermios params const"), the 'tty' parameter is only read in
tty_get_baud_rate(). Therefore, we can make 'tty' accepted in the
function 'const' for clarity.

The "the terminal bit flags may be updated." part of the
tty_get_baud_rate()'s kernel-doc is dropped as it is no longer true.
Because of the same commit above. And it was misplaced anyway.

Signed-off-by: "Jiri Slaby (SUSE)" <jirislaby@kernel.org>
Cc: Ilpo Järvinen <ilpo.jarvinen@linux.intel.com>
Reviewed-by: Ilpo Järvinen <ilpo.jarvinen@linux.intel.com>
Link: https://lore.kernel.org/r/20231127123713.14504-1-jirislaby@kernel.org
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

tty: move locking docs out of Returns for functions in tty.h

Both tty_kref_get() and tty_get_baud_rate() note about locking in their
Return kernel-doc clause. Extract this info into a separate "Locking"
paragraph -- the same as we do for other tty functions.

Signed-off-by: "Jiri Slaby (SUSE)" <jirislaby@kernel.org>
Suggested-by: Ilpo Järvinen <ilpo.jarvinen@linux.intel.com>
Reviewed-by: Ilpo Järvinen <ilpo.jarvinen@linux.intel.com>
Link: https://lore.kernel.org/r/20231121092258.9334-5-jirislaby@kernel.org
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

tty: fix kernel-doc for functions in tty.h

tty_kref_get() is already included in Documentation, but is not properly
formatted. Fix this.

tty_get_baud_rate() is neither properly formatted, nor is included. Fix
both.

Signed-off-by: "Jiri Slaby (SUSE)" <jirislaby@kernel.org>
Link: https://lore.kernel.org/r/20230919085156.1578-10-jirislaby@kernel.org
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

tty: switch tty_{,un}throttle_safe() to return a bool

They return 0 or 1 -- a boolean value, so make it clear than noone
should expect negative or other values.

Signed-off-by: "Jiri Slaby (SUSE)" <jirislaby@kernel.org>
Link: https://lore.kernel.org/r/20230919085156.1578-7-jirislaby@kernel.org
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

tty: shrink the size of struct tty_struct by 40 bytes

It's been a long time since anyone has looked at what struct tty_struct
looks like in memory, turns out there was a ton of holes.

So move things around a bit, change one variable (closing) from being an
int to a bool (it is only being tested for 0/1), and we end up saving 40
bytes per structure overall on x86-64 systems.

Before this patch:
/* size: 696, cachelines: 11, members: 37 */
/* sum members: 665, holes: 8, sum holes: 31 */
/* forced alignments: 2, forced holes: 1, sum forced holes: 4 */
/* last cacheline: 56 bytes */

After this change:
/* size: 656, cachelines: 11, members: 37 */
/* sum members: 654, holes: 1, sum holes: 2 */
/* forced alignments: 2 */
/* last cacheline: 16 bytes */

Cc: Jiri Slaby <jirislaby@kernel.org>
Link: https://lore.kernel.org/r/2023082519-cobbler-unholy-8d1f@gregkh
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

tty: make tty_class a static const structure

Now that the driver core allows for struct class to be in read-only
memory, move the tty_class structure to be declared at build time
placing it into read-only memory, instead of having to be dynamically
allocated at boot time.

Cc: "Ilpo Järvinen" <ilpo.jarvinen@linux.intel.com>
Reviewed-by: Jiri Slaby <jirislaby@kernel.org>
Link: https://lore.kernel.org/r/2023040250-landowner-unfitted-11f4@gregkh
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

tty: Convert hw_stopped in tty_struct to bool

hw_stopped in tty_struct is used like bool, convert the variable type
to bool.

Signed-off-by: Ilpo Järvinen <ilpo.jarvinen@linux.intel.com>
Acked-by: Ulf Hansson <ulf.hansson@linaro.org> # For MMC
Link: https://lore.kernel.org/r/20230309082035.14880-9-ilpo.jarvinen@linux.intel.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

tty: Return bool from tty_termios_hw_change()

Change tty_termios_hw_change() to return bool.

Reviewed-by: Jiri Slaby <jirislaby@kernel.org>
Reviewed-by: Johan Hovold <johan@kernel.org>
Signed-off-by: Ilpo Järvinen <ilpo.jarvinen@linux.intel.com>
Link: https://lore.kernel.org/r/20230117090358.4796-11-ilpo.jarvinen@linux.intel.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

tty: remove TTY_MAGIC

According to Greg, in the context of magic numbers as defined in
magic-number.rst, "the tty layer should not need this and I'll gladly
take patches"

Acked-by: Jiri Slaby <jirislaby@kernel.org>
Signed-off-by: Ahelenia Ziemiańska <nabijaczleweli@nabijaczleweli.xyz>
Ref: https://lore.kernel.org/linux-doc/YyMlovoskUcHLEb7@kroah.com/
Link: https://lore.kernel.org/r/476d024cd6b04160a5de381ea2b9856b60088cbd.1663288066.git.nabijaczleweli@nabijaczleweli.xyz
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

tty: Make tty_termios_copy_hw() old ktermios const

There should be no reason to adjust old ktermios which is going to get
discarded anyway.

Reviewed-by: Andy Shevchenko <andy.shevchenko@gmail.com>
Signed-off-by: Ilpo Järvinen <ilpo.jarvinen@linux.intel.com>
Link: https://lore.kernel.org/r/20220816115739.10928-5-ilpo.jarvinen@linux.intel.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

tty: Remove baudrate dead code & make ktermios params const

With the architectures currently in-tree, either:
1) CBAUDEX is zero
2) The earlier BOTHER if check covers cbaud < 1 case
3) All CBAUD bits are covered by the baud_table

Thus, the check for cbaud being out-of-range for CBAUDEX case cannot
ever be true.

The ktermios parameters can now be made const.

Reviewed-by: Andy Shevchenko <andy.shevchenko@gmail.com>
Signed-off-by: Ilpo Järvinen <ilpo.jarvinen@linux.intel.com>
Link: https://lore.kernel.org/r/20220816115739.10928-2-ilpo.jarvinen@linux.intel.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

tty: reformat tty_struct::flags into kernel-doc

Move the partial tty_struct::flags documentation from tty_ldisc to the
tty.h header and combine it with the one-liners present there. Convert
all those to kernel-doc. This way, we can simply reference the
documentation in Documentation while the text is still along the
definitions.

Signed-off-by: Jiri Slaby <jslaby@suse.cz>
Link: https://lore.kernel.org/r/20211126081611.11001-10-jslaby@suse.cz
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

tty: finish kernel-doc of tty_struct members

There are already pieces of kernel-doc documentation for struct
tty_struct in tty.h. Finish the documentation for the members which were
undocumented yet.

It also includes tuning the already existing pieces like flow and ctrl,
especially adding highlights to them.

Signed-off-by: Jiri Slaby <jslaby@suse.cz>
Link: https://lore.kernel.org/r/20211126081611.11001-2-jslaby@suse.cz
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

tty: remove file from n_tty_ioctl_helper

After the previous patch, there are no users of 'file' in
n_tty_ioctl_helper. So remove it also from there.

Cc: Marcel Holtmann <marcel@holtmann.org>
Cc: Johan Hedberg <johan.hedberg@gmail.com>
Cc: Luiz Augusto von Dentz <luiz.dentz@gmail.com>
Cc: Paul Mackerras <paulus@samba.org>
Cc: "David S. Miller" <davem@davemloft.net>
Cc: Jakub Kicinski <kuba@kernel.org>
Cc: Krzysztof Kozlowski <krzysztof.kozlowski@canonical.com>
Acked-by: Krzysztof Kozlowski <krzysztof.kozlowski@canonical.com>
Signed-off-by: Jiri Slaby <jslaby@suse.cz>
Link: https://lore.kernel.org/r/20210914091134.17426-6-jslaby@suse.cz
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

tty: remove file from tty_mode_ioctl

The only user of 'file' parameter in tty_mode_ioctl is a BUG_ON check.
Provided it never crashed for anyone, it's an overkill to pass the
parameter to tty_mode_ioctl only for this check.

If we wanted to check 'file' there, we should handle it in more graceful
way anyway. Not by a BUG == crash.

Cc: Wolfgang Grandegger <wg@grandegger.com>
Cc: Marc Kleine-Budde <mkl@pengutronix.de>
Cc: "David S. Miller" <davem@davemloft.net>
Cc: Jakub Kicinski <kuba@kernel.org>
Cc: Andreas Koensgen <ajk@comnets.uni-bremen.de>
Cc: Paul Mackerras <paulus@samba.org>
Acked-by: Marc Kleine-Budde <mkl@pengutronix.de>
Signed-off-by: Jiri Slaby <jslaby@suse.cz>
Link: https://lore.kernel.org/r/20210914091134.17426-5-jslaby@suse.cz
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

tty: remove extern from functions in tty headers

After the recent headers cleanup, some function declarations still have
extern before them. It is superfluous (for function declarations), so
remove extern from those which still have it.

This unifies them with the rest of the files.

Signed-off-by: Jiri Slaby <jslaby@suse.cz>
Link: https://lore.kernel.org/r/20210914091134.17426-3-jslaby@suse.cz
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

tty: move tty_port to new tty_port.h

tty.h is long enough already. And I am slowly adding kernel-doc
documentation, so it grows to unmaintainable long mess. To avoid this,
split tty.h further into tty_port.h and move there tty_port-related
declarations and function prototypes (those implemented in tty_port.c).

Signed-off-by: Jiri Slaby <jslaby@suse.cz>
Link: https://lore.kernel.org/r/20210723103147.18250-8-jslaby@suse.cz
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

tty: move tty_buffer definitions to new tty_buffer.h

tty.h is large enough currently. And I am slowly adding kernel-doc
documentation, so it grows to unmaintainable long mess. To avoid this,
split tty.h further into tty_buffer.h and move there tty_buffer-related
declarations and function prototypes.

Note that many of the tty_buffer.c function prototypes reside now in
tty_flip.h. But we cannot move struct tty_buffer & friends because:
* tty_insert_flip_char() in tty_flip.h needs both struct tty_port and
struct tty_buffer defined.
* struct tty_port in tty_port.h needs struct tty_buffer defined.

So if we moved struct tty_buffer to tty_flip.h too, tty_flip.h would
need tty_port.h and that would need tty_flip.h (to have tty_buffer)
again. Hence we introduce new header tty_buffer.h here to break this
circular dependency.

Signed-off-by: Jiri Slaby <jslaby@suse.cz>
Link: https://lore.kernel.org/r/20210723103147.18250-7-jslaby@suse.cz
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

tty: move tty_ldisc_receive_buf to tty_flip.h

It's the only remaining tty_buffer.c prototype residing in tty.h. Move
it along others to tty_flip.h.

Signed-off-by: Jiri Slaby <jslaby@suse.cz>
Link: https://lore.kernel.org/r/20210723103147.18250-6-jslaby@suse.cz
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

tty: move ldisc prototypes to tty_ldisc.h

We already have tty_ldisc.h, so cleanup tty.h a bit by moving out
tty_ldisc-related function prototypes and a variable into tty_ldisc.h.
They are implemented in tty_ldisc.c anyway.

Signed-off-by: Jiri Slaby <jslaby@suse.cz>
Link: https://lore.kernel.org/r/20210723103147.18250-4-jslaby@suse.cz
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

tty: move tty_driver related prototypes to tty_driver.h

We already have tty_driver.h, so cleanup tty.h a bit by moving out
tty_driver-related function prototypes into tty_driver.h.

Note that tty.h already includes tty_driver.h.

Signed-off-by: Jiri Slaby <jslaby@suse.cz>
Link: https://lore.kernel.org/r/20210723103147.18250-2-jslaby@suse.cz
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

tty: make tty_get_{char,frame}_size available

Many tty drivers contain code to compute bits count depending on termios
cflags. So extract this code from serial core to two separate tty helper
functions:
* tty_get_char_size -- only size of a character, without flags,
* tty_get_frame_size -- complete size of a frame including flags.

In the next patch, calls to these new functions replace many copies of
this code.

Note that we accept only cflag as a parameter. That's because some
callers like pch_uart_startup or sunsab_console_setup don't have at hand
termios which we could pass around.

Cc: Joe Perches <joe@perches.com>
Cc: Johan Hovold <johan@kernel.org>
Reviewed-by: Andy Shevchenko <andy.shevchenko@gmail.com>
Signed-off-by: Jiri Slaby <jslaby@suse.cz>
Link: https://lore.kernel.org/r/20210610090247.2593-1-jslaby@suse.cz
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

tty: remove unused tty_throttle

The last user was removed in commit e91e52e42814 (n_tty: Fix stuck
throttled driver) in 2013. So remove exported tty_throttle completely.

Signed-off-by: Jiri Slaby <jslaby@suse.cz>
Link: https://lore.kernel.org/r/20210510065923.5112-1-jslaby@suse.cz
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

tty: make tty_operations::chars_in_buffer return uint

tty_operations::chars_in_buffer is another hook which is expected to
return values >= 0. So make it explicit by the return type too -- use
unsigned int.

Signed-off-by: Jiri Slaby <jslaby@suse.cz>
Acked-By: Anton Ivanov <anton.ivanov@cambridgegreys.com>
Acked-by: David Sterba <dsterba@suse.com>
Cc: Jeff Dike <jdike@addtoit.com>
Cc: Richard Weinberger <richard@nod.at>
Cc: Arnd Bergmann <arnd@arndb.de>
Cc: Samuel Iglesias Gonsalvez <siglesias@igalia.com>
Cc: Jens Taprogge <jens.taprogge@taprogge.org>
Cc: Karsten Keil <isdn@linux-pingi.de>
Cc: Ulf Hansson <ulf.hansson@linaro.org>
Cc: "David S. Miller" <davem@davemloft.net>
Cc: Jakub Kicinski <kuba@kernel.org>
Cc: Heiko Carstens <hca@linux.ibm.com>
Cc: Vasily Gorbik <gor@linux.ibm.com>
Cc: Christian Borntraeger <borntraeger@de.ibm.com>
Cc: David Lin <dtwlin@gmail.com>
Cc: Johan Hovold <johan@kernel.org>
Cc: Alex Elder <elder@kernel.org>
Cc: Jiri Kosina <jikos@kernel.org>
Cc: Shawn Guo <shawnguo@kernel.org>
Cc: Sascha Hauer <s.hauer@pengutronix.de>
Cc: Oliver Neukum <oneukum@suse.com>
Cc: Felipe Balbi <balbi@kernel.org>
Cc: Mathias Nyman <mathias.nyman@intel.com>
Cc: Marcel Holtmann <marcel@holtmann.org>
Cc: Johan Hedberg <johan.hedberg@gmail.com>
Cc: Luiz Augusto von Dentz <luiz.dentz@gmail.com>
Link: https://lore.kernel.org/r/20210505091928.22010-27-jslaby@suse.cz
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

tty: make tty_operations::write_room return uint

Line disciplines expect a positive value or zero returned from
tty->ops->write_room (invoked by tty_write_room). So make this
assumption explicit by using unsigned int as a return value. Both of
tty->ops->write_room and tty_write_room.

Signed-off-by: Jiri Slaby <jslaby@suse.cz>
Acked-by: Laurentiu Tudor <laurentiu.tudor@nxp.com>
Acked-by: Alex Elder <elder@linaro.org>
Acked-by: Max Filippov <jcmvbkbc@gmail.com> # xtensa
Acked-by: David Sterba <dsterba@suse.com>
Acked-By: Anton Ivanov <anton.ivanov@cambridgegreys.com>
Acked-by: Geert Uytterhoeven <geert@linux-m68k.org>
Cc: Richard Henderson <rth@twiddle.net>
Cc: Ivan Kokshaysky <ink@jurassic.park.msu.ru>
Cc: Matt Turner <mattst88@gmail.com>
Cc: "James E.J. Bottomley" <James.Bottomley@HansenPartnership.com>
Cc: Helge Deller <deller@gmx.de>
Cc: Jeff Dike <jdike@addtoit.com>
Cc: Richard Weinberger <richard@nod.at>
Cc: Chris Zankel <chris@zankel.net>
Cc: Arnd Bergmann <arnd@arndb.de>
Cc: Samuel Iglesias Gonsalvez <siglesias@igalia.com>
Cc: Jens Taprogge <jens.taprogge@taprogge.org>
Cc: Karsten Keil <isdn@linux-pingi.de>
Cc: Scott Branden <scott.branden@broadcom.com>
Cc: Ulf Hansson <ulf.hansson@linaro.org>
Cc: "David S. Miller" <davem@davemloft.net>
Cc: Jakub Kicinski <kuba@kernel.org>
Cc: Heiko Carstens <hca@linux.ibm.com>
Cc: Vasily Gorbik <gor@linux.ibm.com>
Cc: Christian Borntraeger <borntraeger@de.ibm.com>
Cc: David Lin <dtwlin@gmail.com>
Cc: Johan Hovold <johan@kernel.org>
Cc: Jiri Kosina <jikos@kernel.org>
Cc: Shawn Guo <shawnguo@kernel.org>
Cc: Sascha Hauer <s.hauer@pengutronix.de>
Cc: Oliver Neukum <oneukum@suse.com>
Cc: Felipe Balbi <balbi@kernel.org>
Cc: Mathias Nyman <mathias.nyman@intel.com>
Cc: Marcel Holtmann <marcel@holtmann.org>
Cc: Johan Hedberg <johan.hedberg@gmail.com>
Cc: Luiz Augusto von Dentz <luiz.dentz@gmail.com>
Link: https://lore.kernel.org/r/20210505091928.22010-23-jslaby@suse.cz
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

tty: return void from tty_unregister_ldisc

Now that noone checks the return value of tty_unregister_ldisc, make the
function return 'void'.

Signed-off-by: Jiri Slaby <jslaby@suse.cz>
Link: https://lore.kernel.org/r/20210505091928.22010-20-jslaby@suse.cz
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

tty: make tty_ldisc_ops a param in tty_unregister_ldisc

Make tty_unregister_ldisc symmetric to tty_register_ldisc by accepting
struct tty_ldisc_ops as a parameter instead of ldisc number. This avoids
checking of the ldisc number bounds in tty_unregister_ldisc.

Signed-off-by: Jiri Slaby <jslaby@suse.cz>
Cc: William Hubbs <w.d.hubbs@gmail.com>
Cc: Chris Brannon <chris@the-brannons.com>
Cc: Kirk Reiser <kirk@reisers.ca>
Cc: Samuel Thibault <samuel.thibault@ens-lyon.org>
Cc: Marcel Holtmann <marcel@holtmann.org>
Cc: Johan Hedberg <johan.hedberg@gmail.com>
Cc: Luiz Augusto von Dentz <luiz.dentz@gmail.com>
Cc: Dmitry Torokhov <dmitry.torokhov@gmail.com>
Cc: Arnd Bergmann <arnd@arndb.de>
Cc: "David S. Miller" <davem@davemloft.net>
Cc: Jakub Kicinski <kuba@kernel.org>
Cc: Wolfgang Grandegger <wg@grandegger.com>
Cc: Marc Kleine-Budde <mkl@pengutronix.de>
Cc: Andreas Koensgen <ajk@comnets.uni-bremen.de>
Cc: Paul Mackerras <paulus@samba.org>
Cc: Rodolfo Giometti <giometti@enneenne.com>
Cc: Peter Ujfalusi <peter.ujfalusi@gmail.com>
Cc: Liam Girdwood <lgirdwood@gmail.com>
Cc: Mark Brown <broonie@kernel.org>
Cc: Jaroslav Kysela <perex@perex.cz>
Cc: Takashi Iwai <tiwai@suse.com>
Link: https://lore.kernel.org/r/20210505091928.22010-17-jslaby@suse.cz
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

tty: set tty_ldisc_ops::num statically

There is no reason to pass the ldisc number to tty_register_ldisc
separately. Just set it in the already defined tty_ldisc_ops in all the
ldiscs.

This simplifies tty_register_ldisc a bit too (no need to set the num
member there).

Signed-off-by: Jiri Slaby <jslaby@suse.cz>
Cc: William Hubbs <w.d.hubbs@gmail.com>
Cc: Chris Brannon <chris@the-brannons.com>
Cc: Kirk Reiser <kirk@reisers.ca>
Cc: Samuel Thibault <samuel.thibault@ens-lyon.org>
Cc: Marcel Holtmann <marcel@holtmann.org>
Cc: Johan Hedberg <johan.hedberg@gmail.com>
Cc: Luiz Augusto von Dentz <luiz.dentz@gmail.com>
Cc: Dmitry Torokhov <dmitry.torokhov@gmail.com>
Cc: Arnd Bergmann <arnd@arndb.de>
Cc: "David S. Miller" <davem@davemloft.net>
Cc: Jakub Kicinski <kuba@kernel.org>
Cc: Wolfgang Grandegger <wg@grandegger.com>
Cc: Marc Kleine-Budde <mkl@pengutronix.de>
Cc: Andreas Koensgen <ajk@comnets.uni-bremen.de>
Cc: Paul Mackerras <paulus@samba.org>
Cc: Rodolfo Giometti <giometti@enneenne.com>
Cc: Peter Ujfalusi <peter.ujfalusi@gmail.com>
Cc: Liam Girdwood <lgirdwood@gmail.com>
Cc: Mark Brown <broonie@kernel.org>
Cc: Jaroslav Kysela <perex@perex.cz>
Cc: Takashi Iwai <tiwai@suse.com>
Link: https://lore.kernel.org/r/20210505091928.22010-15-jslaby@suse.cz
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

tty: cumulate and document tty_struct::ctrl* members

Group the ctrl members under a single struct called ctrl. The new struct
contains 'pgrp', 'session', 'pktstatus', and 'packet'. 'pktstatus' and
'packet' used to be bits in a bitfield. The struct also contains the
lock protecting them to share the same cache line.

Note that commit c545b66c6922b (tty: Serialize tcflow() with other tty
flow control changes) added a padding to the original bitfield. It was
for the bitfield to occupy a whole 64b word to avoid interferring stores
on Alpha (cannot we evaporate this arch with weird implications to C
code yet?). But it doesn't work as expected as the padding
(tty_struct::ctrl_unused) is aligned to a 8B boundary too and occupies
some bytes from the next word.

So make it reliable by:
1) setting __aligned of the struct -- that aligns the start, and
2) making 'unsigned long unused[0]' as the last member of the struct --
pads the end.

Add a kerneldoc comment for this grouped members.

Signed-off-by: Jiri Slaby <jslaby@suse.cz>
Cc: "David S. Miller" <davem@davemloft.net>
Cc: Jakub Kicinski <kuba@kernel.org>
Cc: netdev@vger.kernel.org
Link: https://lore.kernel.org/r/20210505091928.22010-14-jslaby@suse.cz
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

tty: cumulate and document tty_struct::flow* members

Group the flow flags under a single struct called flow. The new struct
contains 'stopped' and 'tco_stopped' bools which used to be bits in a
bitfield. The struct also contains the lock protecting them to
potentially share the same cache line.

Note that commit c545b66c6922b (tty: Serialize tcflow() with other tty
flow control changes) added a padding to the original bitfield. It was
for the bitfield to occupy a whole 64b word to avoid interferring stores
on Alpha (cannot we evaporate this arch with weird implications to C
code yet?). But it doesn't work as expected as the padding
(tty_struct::unused) is aligned to a 8B boundary too and occupies some
bytes from the next word.

So make it reliable by:
1) setting __aligned of the struct -- that aligns the start, and
2) making 'unsigned long unused[0]' as the last member of the struct --
pads the end.

This is also the perfect time to start the documentation of tty_struct
where all this lives. So we start by documenting what these bools
actually serve for. And why we do all the alignment dances. Only the few
up-to-date information from the Theodore's comment made it into this new
Kerneldoc comment.

Signed-off-by: Jiri Slaby <jslaby@suse.cz>
Cc: "David S. Miller" <davem@davemloft.net>
Cc: Jakub Kicinski <kuba@kernel.org>
Cc: Jonathan Corbet <corbet@lwn.net>
Cc: Arnd Bergmann <arnd@arndb.de>
Cc: Ulf Hansson <ulf.hansson@linaro.org>
Cc: Heiko Carstens <hca@linux.ibm.com>
Cc: Vasily Gorbik <gor@linux.ibm.com>
Cc: Christian Borntraeger <borntraeger@de.ibm.com>
Cc: Shawn Guo <shawnguo@kernel.org>
Cc: Sascha Hauer <s.hauer@pengutronix.de>
Cc: Vineet Gupta <vgupta@synopsys.com>
Cc: "Maciej W. Rozycki" <macro@orcam.me.uk>
Link: https://lore.kernel.org/r/20210505091928.22010-13-jslaby@suse.cz
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

tty: make fp of tty_ldisc_ops::receive_buf{,2} const

Char pointer (cp) passed to tty_ldisc_ops::receive_buf{,2} is const.
There is no reason for flag pointer (fp) not to be too. So switch it in
the definition and all uses.

Signed-off-by: Jiri Slaby <jslaby@suse.cz>
Cc: William Hubbs <w.d.hubbs@gmail.com>
Cc: Chris Brannon <chris@the-brannons.com>
Cc: Kirk Reiser <kirk@reisers.ca>
Cc: Samuel Thibault <samuel.thibault@ens-lyon.org>
Cc: Marcel Holtmann <marcel@holtmann.org>
Cc: Johan Hedberg <johan.hedberg@gmail.com>
Cc: Luiz Augusto von Dentz <luiz.dentz@gmail.com>
Cc: Dmitry Torokhov <dmitry.torokhov@gmail.com>
Cc: Arnd Bergmann <arnd@arndb.de>
Cc: "David S. Miller" <davem@davemloft.net>
Cc: Jakub Kicinski <kuba@kernel.org>
Cc: Wolfgang Grandegger <wg@grandegger.com>
Cc: Marc Kleine-Budde <mkl@pengutronix.de>
Cc: Andreas Koensgen <ajk@comnets.uni-bremen.de>
Cc: Paul Mackerras <paulus@samba.org>
Cc: Liam Girdwood <lgirdwood@gmail.com>
Cc: Mark Brown <broonie@kernel.org>
Cc: Jaroslav Kysela <perex@perex.cz>
Cc: Takashi Iwai <tiwai@suse.com>
Cc: Peter Ujfalusi <peter.ujfalusi@gmail.com>
Link: https://lore.kernel.org/r/20210505091928.22010-12-jslaby@suse.cz
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

tty: clean include/linux/tty.h up

There are a lot of tty-core-only functions that are listed in
include/linux/tty.h. Move them to drivers/tty/tty.h so that no one else
can accidentally call them or think that they are public functions.

Cc: Jiri Slaby <jirislaby@kernel.org>
Link: https://lore.kernel.org/r/20210408125134.3016837-14-gregkh@linuxfoundation.org
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

tty: move some tty-only functions to drivers/tty/tty.h

The flow change and restricted_tty_write() logic is internal to the tty
core only, so move it out of the include/linux/tty.h file.

Cc: Jiri Slaby <jirislaby@kernel.org>
Link: https://lore.kernel.org/r/20210408125134.3016837-12-gregkh@linuxfoundation.org
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

tty: make tty_release_redirect() static

No one calls this outside of the tty_io.c file, so mark this static and
do not export the symbol anymore.

Cc: Jiri Slaby <jirislaby@kernel.org>
Link: https://lore.kernel.org/r/20210408125134.3016837-11-gregkh@linuxfoundation.org
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

tty: move some internal tty lock enums and functions out of tty.h

Move the TTY_LOCK_* enums and tty_ldisc lock functions out of the global
tty.h into the local header file to clean things up.

Cc: Jiri Slaby <jirislaby@kernel.org>
Link: https://lore.kernel.org/r/20210408125134.3016837-10-gregkh@linuxfoundation.org
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

tty: audit: move some local functions out of tty.h

The functions tty_audit_add_data() and tty_audit_tiocsti() are local to
the tty core code, and do not need to be in a "kernel-wide" header file
so move them to drivers/tty/tty.h

Cc: Jiri Slaby <jirislaby@kernel.org>
Link: https://lore.kernel.org/r/20210408125134.3016837-9-gregkh@linuxfoundation.org
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

tty: create internal tty.h file

There are a number of functions and #defines in include/linux/tty.h that
do not belong there as they are private to the tty core code.

Create an initial drivers/tty/tty.h file and copy the odd "tty logging"
macros into it to seed the file with some initial things that we know
nothing outside of the tty core should be calling.

Cc: Tetsuo Handa <penguin-kernel@i-love.sakura.ne.jp>
Cc: Jiri Slaby <jirislaby@kernel.org>
Link: https://lore.kernel.org/r/20210408125134.3016837-2-gregkh@linuxfoundation.org
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

tty: clarify that not all ttys have a class device

Commit 30004ac9c090 ("tty: add tty_struct->dev pointer to corresponding
device instance") added a struct device pointer field to struct
tty_struct which was populated with the corresponding tty class device
during initialisation.

Unfortunately, not all ttys have a class device (e.g. pseudoterminals
and serdev) in which case the device pointer will be set to NULL,
something which have bit driver authors over the years.

In retrospect perhaps this field should never have been added, but let's
at least document the current behaviour.

Signed-off-by: Johan Hovold <johan@kernel.org>
Link: https://lore.kernel.org/r/20210409073512.6876-1-johan@kernel.org
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

tty: let tty_unregister_driver return void

Now that noone checks the return value, switch the return type of
tty_unregister_driver to void. We can do that as we always return zero.

Generally, drivers are not allowed to call tty_unregister_driver while
there are open devices.

Signed-off-by: Jiri Slaby <jslaby@suse.cz>
Link: https://lore.kernel.org/r/20210302062214.29627-35-jslaby@suse.cz
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

tty: Export redirect release

This will be required by the pty code when it removes tty_vhangup() on
master close.

Signed-off-by: Corey Minyard <cminyard@mvista.com>
Link: https://lore.kernel.org/r/20201124004902.1398477-2-minyard@acm.org
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

tty_port: drop last traces of low_latency

The main purpose of tty_port::low_latency was removed in commit
a9c3f68f3cd8 (tty: Fix low_latency BUG) back in 2014. It was left in
place for drivers as an optional tune knob. But only one driver has been
using it until the previous commit. So remove this misconcept
completely, given there are no users.

Signed-off-by: Jiri Slaby <jslaby@suse.cz>
Link: https://lore.kernel.org/r/20210105120239.28031-11-jslaby@suse.cz
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

tty: new helper function tty_get_icount()

For a given struct tty_struct this yields the corresponding statistics
about sent and received characters (and some more) which is needed to
implement an LED trigger for tty devices.

The new function is then used to simplify tty_tiocgicount().

Reviewed-by: Pavel Machek <pavel@ucw.cz>
Signed-off-by: Uwe Kleine-König <u.kleine-koenig@pengutronix.de>
Link: https://lore.kernel.org/r/20201218104246.591315-3-u.kleine-koenig@pengutronix.de
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

tty: rename tty_kopen() and add new function tty_kopen_shared()

Introduce a new function tty_kopen_shared() that yields a struct
tty_struct. The semantic difference to tty_kopen() is that the tty is
expected to be used already. So rename tty_kopen() to
tty_kopen_exclusive() for clearness, adapt the single user and put the
common code in a new static helper function.

tty_kopen_shared is to be used to implement an LED trigger for tty
devices in one of the next patches.

Signed-off-by: Uwe Kleine-König <u.kleine-koenig@pengutronix.de>
Link: https://lore.kernel.org/r/20201218104246.591315-2-u.kleine-koenig@pengutronix.de
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

Commit 9bb48c82aced ("tty: implement write_iter") converted the tty
layer to use write_iter. Fix the redirected_tty_write declaration
also in n_tty and change the comparisons to use write_iter instead of
write.

[ Also moved the declaration of redirected_tty_write() to the proper
location in a header file. The reason for the bug was the bogus extern
declaration in n_tty.c silently not matching the changed definition in
tty_io.c, and because it wasn't in a shared header file, there was no
cross-checking of the declaration.

Sami noticed because Clang's Control Flow Integrity checking ended up
incidentally noticing the inconsistent declaration. - Linus ]

Fixes: 9bb48c82aced ("tty: implement write_iter")
Signed-off-by: Sami Tolvanen <samitolvanen@google.com>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

tty: use const parameters in port-flag accessors

Declare the port parameter to the flag-test accessors as const.

This is currently mostly cosmetic as the accessors are already inlined.

Suggested-by: Jiri Slaby <jirislaby@kernel.org>
Signed-off-by: Johan Hovold <johan@kernel.org>
Link: https://lore.kernel.org/r/20201202113942.27024-3-johan@kernel.org
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

tty: use assign_bit() in port-flag accessors

Use the new assign_bit() wrapper in the port-flag accessors instead of
open coding.

Suggested-by: Jiri Slaby <jirislaby@kernel.org>
Signed-off-by: Johan Hovold <johan@kernel.org>
Link: https://lore.kernel.org/r/20201202113942.27024-2-johan@kernel.org
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

tty: Fix ->session locking

Currently, locking of ->session is very inconsistent; most places
protect it using the legacy tty mutex, but disassociate_ctty(),
__do_SAK(), tiocspgrp() and tiocgsid() don't.
Two of the writers hold the ctrl_lock (because they already need it for
->pgrp), but __proc_set_tty() doesn't do that yet.

On a PREEMPT=y system, an unprivileged user can theoretically abuse
this broken locking to read 4 bytes of freed memory via TIOCGSID if
tiocgsid() is preempted long enough at the right point. (Other things
might also go wrong, especially if root-only ioctls are involved; I'm
not sure about that.)

Change the locking on ->session such that:

- tty_lock() is held by all writers: By making disassociate_ctty()
hold it. This should be fine because the same lock can already be
taken through the call to tty_vhangup_session().
The tricky part is that we need to shorten the area covered by
siglock to be able to take tty_lock() without ugly retry logic; as
far as I can tell, this should be fine, since nothing in the
signal_struct is touched in the `if (tty)` branch.
- ctrl_lock is held by all writers: By changing __proc_set_tty() to
hold the lock a little longer.
- All readers that aren't holding tty_lock() hold ctrl_lock: By
adding locking to tiocgsid() and __do_SAK(), and expanding the area
covered by ctrl_lock in tiocspgrp().

Cc: stable@kernel.org
Signed-off-by: Jann Horn <jannh@google.com>
Reviewed-by: Jiri Slaby <jirislaby@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

tty: Remove dead termiox code

set_termiox() and the TCGETX handler bail out with -EINVAL immediately
if ->termiox is NULL, but there are no code paths that can set
->termiox to a non-NULL pointer; and no such code paths seem to have
existed since the termiox mechanism was introduced back in
commit 1d65b4a088de ("tty: Add termiox") in v2.6.28.
Similarly, no driver actually implements .set_termiox; and it looks like
no driver ever has.

Delete this dead code; but leave the definition of struct termiox in the
UAPI headers intact.

Signed-off-by: Jann Horn <jannh@google.com>
Link: https://lore.kernel.org/r/20201203020331.2394754-1-jannh@google.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

tty: tty_io: Move 'tty_sysctl_init's prototype to shared space

Fixes the following W=1 kernel build warning(s):

drivers/tty/tty_ldisc.c:883:6: warning: no previous prototype for ‘tty_sysctl_init’ [-Wmissing-prototypes]
883 | void tty_sysctl_init(void)
| ^~~~~~~~~~~~~~~

Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Cc: Jiri Slaby <jirislaby@kernel.org>
Cc: Nick Holloway <alfie@dcs.warwick.ac.uk>
Cc: -- <julian@uhunix.uhcc.hawaii.edu>
Cc: Marko Kohtala <Marko.Kohtala@hut.fi>
Cc: Bill Hawes <whawes@star.net>
Cc: "C. Scott Ananian" <cananian@alumni.princeton.edu>
Cc: Russell King <rmk@arm.linux.org.uk>
Cc: Andrew Morton <andrewm@uow.edu.eu>
Signed-off-by: Lee Jones <lee.jones@linaro.org>
Link: https://lore.kernel.org/r/20201104193549.4026187-5-lee.jones@linaro.org
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

gcc-10 warnings: fix low-hanging fruit

Due to a bug-report that was compiler-dependent, I updated one of my
machines to gcc-10. That shows a lot of new warnings. Happily they
seem to be mostly the valid kind, but it's going to cause a round of
churn for getting rid of them..

This is the really low-hanging fruit of removing a couple of zero-sized
arrays in some core code. We have had a round of these patches before,
and we'll have many more coming, and there is nothing special about
these except that they were particularly trivial, and triggered more
warnings than most.

Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

serdev: ttyport: restore client ops on deregistration

The serdev tty-port controller driver should reset the tty-port client
operations also on deregistration to avoid a NULL-pointer dereference in
case the port is later re-registered as a normal tty device.

Note that this can only happen with tty drivers such as 8250 which have
statically allocated port structures that can end up being reused and
where a later registration would not register a serdev controller (e.g.
due to registration errors or if the devicetree has been changed in
between).

Specifically, this can be an issue for any statically defined ports that
would be registered by 8250 core when an 8250 driver is being unbound.

Fixes: bed35c6dfa6a ("serdev: add a tty port controller driver")
Cc: stable <stable@vger.kernel.org> # 4.11
Reported-by: Loic Poulain <loic.poulain@linaro.org>
Signed-off-by: Johan Hovold <johan@kernel.org>
Link: https://lore.kernel.org/r/20200210145730.22762-1-johan@kernel.org
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

tty: Don't block on IO when ldisc change is pending

There might be situations where tty_ldisc_lock() has blocked, but there
is already IO on tty and it prevents line discipline changes.
It might theoretically turn into dead-lock.

Basically, provide more priority to pending tty_ldisc_lock() than to
servicing reads/writes over tty.

User-visible issue was reported by Mikulas where on pa-risc with
Debian 5 reboot took either 80 seconds, 3 minutes or 3:25 after proper
locking in tty_reopen().

Cc: Jiri Slaby <jslaby@suse.com>
Reported-by: Mikulas Patocka <mpatocka@redhat.com>
Signed-off-by: Dmitry Safonov <dima@arista.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

USB: serial: console: fix reported terminal settings

The USB-serial console implementation has never reported the actual
terminal settings used. Despite storing the corresponding cflags in its
struct console, these were never honoured on later tty open() where the
tty termios would be left initialised to the driver defaults.

Unlike the serial console implementation, the USB-serial code calls
subdriver open() already at console setup. While calling set_termios()
and write() before open() looks like it could work for some USB-serial
drivers, others definitely do not expect this, so modelling this after
serial core is going to be intrusive, if at all possible.

Instead, use a (renamed) tty helper to save the termios data used at
console setup so that the tty termios reflects the actual terminal
settings after a subsequent tty open().

Note that the calls to tty_init_termios() (tty_driver_install()) and
tty_save_termios() are serialised using the disconnect mutex.

This specifically fixes a regression that was triggered by a recent
change adding software flow control to the pl2303 driver: a getty trying
to disable flow control while leaving the baud rate unchanged would now
also set the baud rate to the driver default (prior to the flow-control
change this had been a noop).

Fixes: 7041d9c3f01b ("USB: serial: pl2303: add support for tx xon/xoff flow control")
Cc: stable <stable@vger.kernel.org> # 4.18
Cc: Florian Zumbiehl <florz@florz.de>
Reported-by: Jarkko Nikula <jarkko.nikula@linux.intel.com>
Tested-by: Jarkko Nikula <jarkko.nikula@linux.intel.com>
Acked-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Johan Hovold <johan@kernel.org>

move compat handling of tty ioctls to tty_compat_ioctl()

ioctls that are
* callable only via tty_ioctl()
* not driver-specific
* not demand data structure conversions
* either always need passing arg as is or always demand compat_ptr()
get intercepted in tty_compat_ioctl() from the very beginning and
redirecter to tty_ioctl(). As the result, their entries in fs/compat_ioctl.c
(some of those had been missing, BTW) got removed, as well as
n_tty_compat_ioctl_helper() (now it's never called with any cmd it would accept).

Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>

tty: add missing const to termios hw-change helper

Add missing const qualifiers to the parameters of the termios hw-change
helper, which is used by a few USB serial drivers. This specifically
allows the pl2303 driver to use const arguments in one of its helper as
well.

Cc: Jiri Slaby <jslaby@suse.com>
Acked-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Johan Hovold <johan@kernel.org>

proc: introduce proc_create_seq{,_data}

Variants of proc_create{,_data} that directly take a struct seq_operations
argument and drastically reduces the boilerplate code in the callers.

All trivial callers converted over.

Signed-off-by: Christoph Hellwig <hch@lst.de>

tty: Don't call panic() at tty_ldisc_init()

syzbot is reporting kernel panic [1] triggered by memory allocation failure
at tty_ldisc_get() from tty_ldisc_init(). But since both tty_ldisc_get()
and caller of tty_ldisc_init() can cleanly handle errors, tty_ldisc_init()
does not need to call panic() when tty_ldisc_get() failed.

[1] https://syzkaller.appspot.com/bug?id=883431818e036ae6a9981156a64b821110f39187

Signed-off-by: Tetsuo Handa <penguin-kernel@I-love.SAKURA.ne.jp>
Reported-by: syzbot <syzkaller@googlegroups.com>
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Cc: Jiri Slaby <jslaby@suse.com>
Cc: stable <stable@vger.kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

tty: make n_tty_read() always abort if hangup is in progress

A tty is hung up by __tty_hangup() setting file->f_op to
hung_up_tty_fops, which is skipped on ttys whose write operation isn't
tty_write(). This means that, for example, /dev/console whose write
op is redirected_tty_write() is never actually marked hung up.

Because n_tty_read() uses the hung up status to decide whether to
abort the waiting readers, the lack of hung-up marking can lead to the
following scenario.

1. A session contains two processes. The leader and its child. The
child ignores SIGHUP.

2. The leader exits and starts disassociating from the controlling
terminal (/dev/console).

3. __tty_hangup() skips setting f_op to hung_up_tty_fops.

4. SIGHUP is delivered and ignored.

5. tty_ldisc_hangup() is invoked. It wakes up the waits which should
clear the read lockers of tty->ldisc_sem.

6. The reader wakes up but because tty_hung_up_p() is false, it
doesn't abort and goes back to sleep while read-holding
tty->ldisc_sem.

7. The leader progresses to tty_ldisc_lock() in tty_ldisc_hangup()
and is now stuck in D sleep indefinitely waiting for
tty->ldisc_sem.

The following is Alan's explanation on why some ttys aren't hung up.

http://lkml.kernel.org/r/20171101170908.6ad08580@alans-desktop

1. It broke the serial consoles because they would hang up and close
down the hardware. With tty_port that *should* be fixable properly
for any cases remaining.

2. The console layer was (and still is) completely broken and doens't
refcount properly. So if you turn on console hangups it breaks (as
indeed does freeing consoles and half a dozen other things).

As neither can be fixed quickly, this patch works around the problem
by introducing a new flag, TTY_HUPPING, which is used solely to tell
n_tty_read() that hang-up is in progress for the console and the
readers should be aborted regardless of the hung-up status of the
device.

The following is a sample hung task warning caused by this issue.

INFO: task agetty:2662 blocked for more than 120 seconds.
Not tainted 4.11.3-dbg-tty-lockup-02478-gfd6c7ee-dirty #28
"echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
0 2662 1 0x00000086
Call Trace:
__schedule+0x267/0x890
schedule+0x36/0x80
schedule_timeout+0x23c/0x2e0
ldsem_down_write+0xce/0x1f6
tty_ldisc_lock+0x16/0x30
tty_ldisc_hangup+0xb3/0x1b0
__tty_hangup+0x300/0x410
disassociate_ctty+0x6c/0x290
do_exit+0x7ef/0xb00
do_group_exit+0x3f/0xa0
get_signal+0x1b3/0x5d0
do_signal+0x28/0x660
exit_to_usermode_loop+0x46/0x86
do_syscall_64+0x9c/0xb0
entry_SYSCALL64_slow_path+0x25/0x25

The following is the repro. Run "$PROG /dev/console". The parent
process hangs in D state.

#include <sys/types.h>
#include <sys/stat.h>
#include <sys/wait.h>
#include <sys/ioctl.h>
#include <fcntl.h>
#include <unistd.h>
#include <stdio.h>
#include <stdlib.h>
#include <errno.h>
#include <signal.h>
#include <time.h>
#include <termios.h>

int main(int argc, char **argv)
{
struct sigaction sact = { .sa_handler = SIG_IGN };
struct timespec ts1s = { .tv_sec = 1 };
pid_t pid;
int fd;

if (argc < 2) {
fprintf(stderr, "test-hung-tty /dev/$TTY\n");
return 1;
}

/* fork a child to ensure that it isn't already the session leader */
pid = fork();
if (pid < 0) {
perror("fork");
return 1;
}

if (pid > 0) {
/* top parent, wait for everyone */
while (waitpid(-1, NULL, 0) >= 0)
;
if (errno != ECHILD)
perror("waitpid");
return 0;
}

/* new session, start a new session and set the controlling tty */
if (setsid() < 0) {
perror("setsid");
return 1;
}

fd = open(argv[1], O_RDWR);
if (fd < 0) {
perror("open");
return 1;
}

if (ioctl(fd, TIOCSCTTY, 1) < 0) {
perror("ioctl");
return 1;
}

/* fork a child, sleep a bit and exit */
pid = fork();
if (pid < 0) {
perror("fork");
return 1;
}

if (pid > 0) {
nanosleep(&ts1s, NULL);
printf("Session leader exiting\n");
exit(0);
}

/*
* The child ignores SIGHUP and keeps reading from the controlling
* tty. Because SIGHUP is ignored, the child doesn't get killed on
* parent exit and the bug in n_tty makes the read(2) block the
* parent's control terminal hangup attempt. The parent ends up in
* D sleep until the child is explicitly killed.
*/
sigaction(SIGHUP, &sact, NULL);
printf("Child reading tty\n");
while (1) {
char buf[1024];

if (read(fd, buf, sizeof(buf)) < 0) {
perror("read");
return 1;
}
}

return 0;
}

Signed-off-by: Tejun Heo <tj@kernel.org>
Cc: Alan Cox <alan@llwyncelyn.cymru>
Cc: stable@vger.kernel.org
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

tty: fix data race between tty_init_dev and flush of buf

There can be a race, if receive_buf call comes before
tty initialization completes in n_tty_open and tty->disc_data
may be NULL.

CPU0 CPU1
---- ----
000|n_tty_receive_buf_common() n_tty_open()
-001|n_tty_receive_buf2() tty_ldisc_open.isra.3()
-002|tty_ldisc_receive_buf(inline) tty_ldisc_setup()

Using ldisc semaphore lock in tty_init_dev till disc_data
initializes completely.

Signed-off-by: Gaurav Kohli <gkohli@codeaurora.org>
Reviewed-by: Alan Cox <alan@linux.intel.com>
Cc: stable <stable@vger.kernel.org>

Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

License cleanup: add SPDX GPL-2.0 license identifier to files with no license

Many source files in the tree are missing licensing information, which
makes it harder for compliance tools to determine the correct license.

By default all files without license information are under the default
license of the kernel, which is GPL version 2.

Update the files which contain no license information with the 'GPL-2.0'
SPDX license identifier. The SPDX identifier is a legally binding
shorthand, which can be used instead of the full boiler plate text.

This patch is based on work done by Thomas Gleixner and Kate Stewart and
Philippe Ombredanne.

How this work was done:

Patches were generated and checked against linux-4.14-rc6 for a subset of
the use cases:
- file had no licensing information it it.
- file was a */uapi/* one with no licensing information in it,
- file was a */uapi/* one with existing licensing information,

Further patches will be generated in subsequent months to fix up cases
where non-standard license headers were used, and references to license
had to be inferred by heuristics based on keywords.

The analysis to determine which SPDX License Identifier to be applied to
a file was done in a spreadsheet of side by side results from of the
output of two independent scanners (ScanCode & Windriver) producing SPDX
tag:value files created by Philippe Ombredanne. Philippe prepared the
base worksheet, and did an initial spot review of a few 1000 files.

The 4.13 kernel was the starting point of the analysis with 60,537 files
assessed. Kate Stewart did a file by file comparison of the scanner
results in the spreadsheet to determine which SPDX license identifier(s)
to be applied to the file. She confirmed any determination that was not
immediately clear with lawyers working with the Linux Foundation.

Criteria used to select files for SPDX license identifier tagging was:
- Files considered eligible had to be source code files.
- Make and config files were included as candidates if they contained >5
lines of source
- File already had some variant of a license header in it (even if <5
lines).

All documentation files were explicitly excluded.

The following heuristics were used to determine which SPDX license
identifiers to apply.

- when both scanners couldn't find any license traces, file was
considered to have no license information in it, and the top level
COPYING file license applied.

For non */uapi/* files that summary was:

SPDX license identifier # files
---------------------------------------------------|-------
GPL-2.0 11139

and resulted in the first patch in this series.

If that file was a */uapi/* path one, it was "GPL-2.0 WITH
Linux-syscall-note" otherwise it was "GPL-2.0". Results of that was:

SPDX license identifier # files
---------------------------------------------------|-------
GPL-2.0 WITH Linux-syscall-note 930

and resulted in the second patch in this series.

- if a file had some form of licensing information in it, and was one
of the */uapi/* ones, it was denoted with the Linux-syscall-note if
any GPL family license was found in the file or had no licensing in
it (per prior point). Results summary:

SPDX license identifier # files
---------------------------------------------------|------
GPL-2.0 WITH Linux-syscall-note 270
GPL-2.0+ WITH Linux-syscall-note 169
((GPL-2.0 WITH Linux-syscall-note) OR BSD-2-Clause) 21
((GPL-2.0 WITH Linux-syscall-note) OR BSD-3-Clause) 17
LGPL-2.1+ WITH Linux-syscall-note 15
GPL-1.0+ WITH Linux-syscall-note 14
((GPL-2.0+ WITH Linux-syscall-note) OR BSD-3-Clause) 5
LGPL-2.0+ WITH Linux-syscall-note 4
LGPL-2.1 WITH Linux-syscall-note 3
((GPL-2.0 WITH Linux-syscall-note) OR MIT) 3
((GPL-2.0 WITH Linux-syscall-note) AND MIT) 1

and that resulted in the third patch in this series.

- when the two scanners agreed on the detected license(s), that became
the concluded license(s).

- when there was disagreement between the two scanners (one detected a
license but the other didn't, or they both detected different
licenses) a manual inspection of the file occurred.

- In most cases a manual inspection of the information in the file
resulted in a clear resolution of the license that should apply (and
which scanner probably needed to revisit its heuristics).

- When it was not immediately clear, the license identifier was
confirmed with lawyers working with the Linux Foundation.

- If there was any question as to the appropriate license identifier,
the file was flagged for further research and to be revisited later
in time.

In total, over 70 hours of logged manual review was done on the
spreadsheet to determine the SPDX license identifiers to apply to the
source files by Kate, Philippe, Thomas and, in some cases, confirmation
by lawyers working with the Linux Foundation.

Kate also obtained a third independent scan of the 4.13 code base from
FOSSology, and compared selected files where the other two scanners
disagreed against that SPDX file, to see if there was new insights. The
Windriver scanner is based on an older version of FOSSology in part, so
they are related.

Thomas did random spot checks in about 500 files from the spreadsheets
for the uapi headers and agreed with SPDX license identifier in the
files he inspected. For the non-uapi files Thomas did random spot checks
in about 15000 files.

In initial set of patches against 4.14-rc6, 3 files were found to have
copy/paste license identifier errors, and have been fixed to reflect the
correct identifier.

Additionally Philippe spent 10 hours this week doing a detailed manual
inspection and review of the 12,461 patched files from the initial patch
version early this week with:
- a full scancode scan run, collecting the matched texts, detected
license ids and scores
- reviewing anything where there was a license detected (about 500+
files) to ensure that the applied SPDX license was correct
- reviewing anything where there was no detection but the patch license
was not GPL-2.0 WITH Linux-syscall-note to ensure that the applied
SPDX license was correct

This produced a worksheet with 20 files needing minor correction. This
worksheet was then exported into 3 different .csv files for the
different types of files to be modified.

These .csv files were then reviewed by Greg. Thomas wrote a script to
parse the csv files and add the proper SPDX tag to the file, in the
format that the file expected. This script was further refined by Greg
based on the output to detect more types of files automatically and to
distinguish between header and source .c files (which need different
comment types.) Finally Greg ran the script using the .csv files to
generate the patches.

Reviewed-by: Kate Stewart <kstewart@linuxfoundation.org>
Reviewed-by: Philippe Ombredanne <pombredanne@nexb.com>
Reviewed-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

tty: undo export of tty_open_by_driver

Since we have tty_kopen, we no longer need to export tty_open_by_driver.
This patch makes this function static.

Signed-off-by: Okash Khawaja <okash.khawaja@gmail.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

tty: resolve tty contention between kernel and user space

The commit 12e84c71b7d4 ("tty: export tty_open_by_driver") exports
tty_open_by_device to allow tty to be opened from inside kernel which
works fine except that it doesn't handle contention with user space or
another kernel-space open of the same tty. For example, opening a tty
from user space while it is kernel opened results in failure and a
kernel log message about mismatch between tty->count and tty's file
open count.

This patch makes kernel access to tty exclusive, so that if a user
process or kernel opens a kernel opened tty, it gets -EBUSY. It does
this by adding TTY_KOPENED flag to tty->flags. When this flag is set,
tty_open_by_driver returns -EBUSY. Instead of overloading
tty_open_by_driver for both kernel and user space, this
patch creates a separate function tty_kopen which closely follows
tty_open_by_driver. tty_kclose closes the tty opened by tty_kopen.

To address the mismatch between tty->count and #fd's, this patch adds
#kopen's to the count before comparing it with tty->count. That way
check_tty_count reflects correct usage count.

Returning -EBUSY on tty open is a change in the interface. I have
tested this with minicom, picocom and commands like "echo foo >
/dev/ttyS0". They all correctly report "Device or resource busy" when
the tty is already kernel opened.

Signed-off-by: Okash Khawaja <okash.khawaja@gmail.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

randstruct: Mark various structs for randomization

This marks many critical kernel structures for randomization. These are
structures that have been targeted in the past in security exploits, or
contain functions pointers, pointers to function pointer tables, lists,
workqueues, ref-counters, credentials, permissions, or are otherwise
sensitive. This initial list was extracted from Brad Spengler/PaX Team's
code in the last public patch of grsecurity/PaX based on my understanding
of the code. Changes or omissions from the original code are mine and
don't reflect the original grsecurity/PaX code.

Left out of this list is task_struct, which requires special handling
and will be covered in a subsequent patch.

Signed-off-by: Kees Cook <keescook@chromium.org>

tty: add function to convert device name to number

The function converts strings like ttyS0 and ttyUSB0 to dev_t like
(4, 64) and (188, 0). It does this by scanning tty_drivers list for
corresponding device name and index. If the driver is not registered,
this function returns -ENODEV. It also acquires tty_mutex.

Signed-off-by: Okash Khawaja <okash.khawaja@gmail.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

tty: define tty_open_by_driver when CONFIG_TTY is not defined

This patch adds definition of tty_open_by_driver when CONFIG_TTY is not
defined. This was supposed to have been included in commit
12e84c71b7d4ee38d51377fd494ac748ee4e6912 ("tty: export
tty_open_by_driver"). The patch follows convention for other such
functions and returns NULL.

Signed-off-by: Okash Khawaja <okash.khawaja@gmail.com>
Reviewed-by: Samuel Thibault <samuel.thibault@ens-lyon.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

tty: drop unused alt_speed from tty_struct

Drop the now unused alt_speed field from struct tty_struct.

Setting an alt_speed using the ASYNC_SPD flags has been deprecated since
v2.1.69, and has been broken for all tty drivers but serial-core since
v3.10 and commit 6865ff222cca ("TTY: do not warn about setting speed via
SPD_*") without anyone noticing.

Note that serial-core still supports changing speed using TIOCSSERIAL
and SPD flags (including "alt-speeds"), but also warns about it being
deprecated since pre-git.

Signed-off-by: Johan Hovold <johan@kernel.org>
Reviewed-by: Andy Shevchenko <andy.shevchenko@gmail.com>
Reviewed-by: Alan Cox <alan@linux.intel.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

tty/serdev: add serdev registration interface

Add a new interface for registering a serdev controller and clients, and
a helper function to deregister serdev devices (or a tty device) that
were previously registered using the new interface.

Once every driver currently using the tty_port_register_device() helpers
have been vetted and converted to use the new serdev registration
interface (at least for deregistration), we can move serdev registration
to the current helpers and get rid of the serdev-specific functions.

Reviewed-by: Rob Herring <robh@kernel.org>
Signed-off-by: Johan Hovold <johan@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

tty: export tty_open_by_driver

This exports tty_open_by_driver so that it can be called from other
places inside the kernel. The checks for null file pointer are based on
Alan Cox's patch here:
http://www.mail-archive.com/linux-kernel@vger.kernel.org/msg1215095.html.
Description below is quoted from it:

"[RFC] tty_port: allow a port to be opened with a tty that has no file handle

Let us create tty objects entirely in kernel space. Untested proposal to
show why all the ideas around rewriting half the uart stack are not needed.

With this a kernel created non file backed tty object could be used to handle
data, and set terminal modes. Not all ldiscs can cope with this as N_TTY in
particular has to work back to the fs/tty layer.

The tty_port code is however otherwise clean of file handles as far as I can
tell as is the low level tty port write path used by the ldisc, the
configuration low level interfaces and most of the ldiscs.

Currently you don't have any exposure to see tty hangups because those are
built around the file layer. However a) it's a fixed port so you probably
don't care about that b) if you do we can add a callback and c) you almost
certainly don't want the userspace tear down/rebuild behaviour anyway.

This should however be sufficient if we wanted for example to enumerate all
the bluetooth bound fixed ports via ACPI and make them directly available.

It doesn't deal with the case of a user opening a port that's also kernel
opened and that would need some locking out (so it returned EBUSY if bound
to a kernel device of some kind). That needs resolving along with how you
"up" or "down" your new bluetooth device, or enumerate it while providing
the existing tty API to avoid regressions (and to debug)."

The exported funtion is used later in this patch set to gain access to tty_struct.

[changed export symbol level - gkh]

Signed-off-by: Okash Khawaja <okash.khawaja@gmail.com>
Reviewed-by: Samuel Thibault <samuel.thibault@ens-lyon.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

tty: split job control support into a file of its own

This makes it easier for job control to become optional and/or usable
independently from tty_io.c, as well as providing a nice purpose
separation. No logical changes from this patch.

Signed-off-by: Nicolas Pitre <nico@linaro.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

console: move console_init() out of tty_io.c

All the console driver handling code lives in printk.c.
Move console_init() there as well so console support can still be used
when the TTY code is configured out. No logical changes from this patch.

Signed-off-by: Nicolas Pitre <nico@linaro.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

tty_port: Add port client functions

Introduce a client (upward direction) operations struct for tty_port
clients. Initially supported operations are for receiving data and write
wake-up. This will allow for having clients other than an ldisc.

Convert the calls to the ldisc to use the client ops as the default
operations.

Signed-off-by: Rob Herring <robh@kernel.org>
Reviewed-By: Sebastian Reichel <sre@kernel.org>
Tested-By: Sebastian Reichel <sre@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

tty: constify tty_ldisc_receive_buf buffer pointer

This is needed to work with the client operations which uses const ptrs.

Really, the flags pointer could be const, too, but this would be a tree
wide fix.

Signed-off-by: Rob Herring <robh@kernel.org>
Reviewed-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Reviewed-By: Sebastian Reichel <sre@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

tty: move the non-file related parts of tty_release to new tty_release_struct

For in-kernel tty users, we need to be able to create and destroy
'struct tty' that are not associated with a file. The creation side is
fine, but tty_release() needs to be split into the file handle portion
and the struct tty portion. Introduce a new function, tty_release_struct,
to handle just the destroying of a struct tty.

Signed-off-by: Rob Herring <robh@kernel.org>
Reviewed-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Reviewed-By: Sebastian Reichel <sre@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

Fix OpenSSH pty regression on close

OpenSSH expects the (non-blocking) read() of pty master to return
EAGAIN only if it has received all of the slave-side output after
it has received SIGCHLD. This used to work on pre-3.12 kernels.

This fix effectively forces non-blocking read() and poll() to
block for parallel i/o to complete for all ttys. It also unwinds
these changes:

1) f8747d4a466ab2cafe56112c51b3379f9fdb7a12
tty: Fix pty master read() after slave closes

2) 52bce7f8d4fc633c9a9d0646eef58ba6ae9a3b73
pty, n_tty: Simplify input processing on final close

3) 1a48632ffed61352a7810ce089dc5a8bcd505a60
pty: Fix input race when closing

Inspired by analysis and patch from Marc Aurele La France <tsi@tuyoix.net>

Reported-by: Volth <openssh@volth.com>
Reported-by: Marc Aurele La France <tsi@tuyoix.net>
BugLink: https://bugzilla.mindrot.org/show_bug.cgi?id=52
BugLink: https://bugzilla.mindrot.org/show_bug.cgi?id=2492
Signed-off-by: Brian Bloniarz <brian.bloniarz@gmail.com>
Reviewed-by: Peter Hurley <peter@hurleysoftware.com>
Cc: stable <stable@vger.kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

tty: Replace ASYNC_INITIALIZED bit and update atomically

Replace ASYNC_INITIALIZED bit in the tty_port::flags field with
TTY_PORT_INITIALIZED bit in the tty_port::iflags field. Introduce helpers
tty_port_set_initialized() and tty_port_initialized() to abstract
atomic bit ops.

Note: the transforms for test_and_set_bit() and test_and_clear_bit()
are unnecessary as the state transitions are already mutually exclusive;
the tty lock prevents concurrent open/close/hangup.

Signed-off-by: Peter Hurley <peter@hurleysoftware.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

tty: Replace ASYNC_SUSPENDED bit and update atomically

Replace ASYNC_SUSPENDED bit in the tty_port::flags field with
TTY_PORT_SUSPENDED bit in the tty_port::iflags field. Introduce helpers
tty_port_set_suspended() and tty_port_suspended() to abstract
atomic bit ops.

Signed-off-by: Peter Hurley <peter@hurleysoftware.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

tty: Replace ASYNC_CHECK_CD and update atomically

Replace ASYNC_CHECK_CD bit in the tty_port::flags field with
TTY_PORT_CHECK_CD bit in the tty_port::iflags field. Introduce helpers
tty_port_set_check_carrier() and tty_port_check_carrier() to abstract
the atomic bit ops.

Signed-off-by: Peter Hurley <peter@hurleysoftware.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

tty: Replace ASYNC_NORMAL_ACTIVE bit and update atomically

Replace ASYNC_NORMAL_ACTIVE bit in the tty_port::flags field with
TTY_PORT_ACTIVE bit in the tty_port::iflags field. Introduce helpers
tty_port_set_active() and tty_port_active() to abstract atomic bit ops.

Extract state changes from port lock sections, as this usage is
broken and confused; the state transitions are protected by the
tty lock (which mutually excludes parallel open/close/hangup),
and no user tests the active state while holding the port lock.

Signed-off-by: Peter Hurley <peter@hurleysoftware.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

tty: Replace ASYNC_CTS_FLOW bit and update atomically

Replace ASYNC_CTS_FLOW bit in the tty_port::flags field with
TTY_PORT_CTS_FLOW bit in the tty_port::iflags field. Add
tty_port_set_cts_flow() helper to abstract the atomic bit ops.

Signed-off-by: Peter Hurley <peter@hurleysoftware.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

tty: Define ASYNC_ replacement bits

Prepare for relocating kernel private state bits out of tty_port::flags
field; tty_port::flags field is not atomic and can become corrupted
by concurrent updates. It also suffers from the complication of sharing
in a userspace-visible field which must be masked.

Define new tty_port::iflags field and new, substitute bit definitions
for the former ASYNC_* flags.

Signed-off-by: Peter Hurley <peter@hurleysoftware.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

tty: Replace TTY_THROTTLED bit tests with tty_throttled()

Abstract TTY_THROTTLED bit tests with tty_throttled().

Signed-off-by: Peter Hurley <peter@hurleysoftware.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

tty: Replace TTY_IO_ERROR bit tests with tty_io_error()

Abstract TTY_IO_ERROR status test treewide with tty_io_error().
NB: tty->flags uses atomic bit ops; replace non-atomic bit test
with test_bit().

Signed-off-by: Peter Hurley <peter@hurleysoftware.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

tty: provide tty_name() even without CONFIG_TTY

The audit subsystem just started printing the name of the tty,
but that causes a build failure when CONFIG_TTY is disabled:

kernel/built-in.o: In function `audit_log_task_info':
memremap.c:(.text+0x5e34c): undefined reference to `tty_name'
kernel/built-in.o: In function `audit_set_loginuid':
memremap.c:(.text+0x63b34): undefined reference to `tty_name'

This adds tty_name() to the list of functions that are provided
as trivial stubs in that configuration.

Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Fixes: db0a6fb5d97a ("audit: add tty field to LOGIN event")
Signed-off-by: Paul Moore <paul@paul-moore.com>

tty: Unify receive_buf() code paths

Instead of two distinct code branches for receive_buf() handling,
use tty_ldisc_receive_buf() as the single code path.

Signed-off-by: Peter Hurley <peter@hurleysoftware.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

tty: Fix GPF in flush_to_ldisc(), part 2

commit 9ce119f318ba ("tty: Fix GPF in flush_to_ldisc()") fixed a
GPF caused by a line discipline which does not define a receive_buf()
method.

However, the vt driver (and speakup driver also) pushes selection
data directly to the line discipline receive_buf() method via
tty_ldisc_receive_buf(). Fix the same problem in tty_ldisc_receive_buf().

Cc: <stable@vger.kernel.org>
Signed-off-by: Peter Hurley <peter@hurleysoftware.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

tty: audit: Combine push functions

tty_audit_push() and tty_audit_push_current() perform identical
tasks; eliminate the tty_audit_push() implementation and the
tty_audit_push_current() name.

Signed-off-by: Peter Hurley <peter@hurleysoftware.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

tty: audit: Ignore current association for audit push

In canonical read mode, each line read and logged is pushed separately
with tty_audit_push(). For all single-threaded processes and multi-threaded
processes reading from only one tty, this patch has no effect; the last line
read will still be the entry pushed to the audit log because the tty
association cannot have changed between tty_audit_add_data() and
tty_audit_push().

For multi-threaded processes reading from different ttys concurrently,
the audit log will have mixed log entries anyway. Consider two ttys
audited concurrently:

CPU0 CPU1
---------- ------------
tty_audit_add_data(ttyA)
tty_audit_add_data(ttyB)
tty_audit_push()
tty_audit_add_data(ttyB)
tty_audit_push()

This patch will now cause the ttyB output to be split into separate
audit log entries.

However, this possibility is equally likely without this patch:

CPU0 CPU1
---------- ------------
tty_audit_add_data(ttyB)
tty_audit_add_data(ttyA)
tty_audit_push()
tty_audit_add_data(ttyB)
tty_audit_push()

Mixed canonical and non-canonical reads have similar races.

Signed-off-by: Peter Hurley <peter@hurleysoftware.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

tty: audit: Remove icanon mode from call chain

The tty termios bits cannot change while n_tty_read() is in the
i/o loop; the termios_rwsem ensures mutual exclusion with termios
changes in n_tty_set_termios(). Check L_ICANON() directly and
eliminate icanon parameter.

NB: tty_audit_add_data() => tty_audit_buf_get() => tty_audit_buf_alloc()
is a single path; ie., tty_audit_buf_get() and tty_audit_buf_alloc()
have no other callers.

Signed-off-by: Peter Hurley <peter@hurleysoftware.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

tty: Make tty_files_lock per-tty

Access to tty->tty_files list is always per-tty, never for all ttys
simultaneously. Replace global tty_files_lock spinlock with per-tty
->files_lock. Initialize when the ->tty_files list is inited, in
alloc_tty_struct().

Signed-off-by: Peter Hurley <peter@hurleysoftware.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

tty: Remove unreferenced tty flags macro TTY_DEBUG

The TTY_DEBUG macro is not used; remove.

Signed-off-by: Peter Hurley <peter@hurleysoftware.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

tty: Move tty_check_change() helper

Move is_ignored() to drivers/tty/tty_io.c and re-declare in file
scope.

Signed-off-by: Peter Hurley <peter@hurleysoftware.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

tty: Remove declarations to non-existent functions

tty_read_raw_data() and tty_signal() no longer exist; remove
declarations.

Signed-off-by: Peter Hurley <peter@hurleysoftware.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

tty: Eliminate global symbol tty_ldisc_N_TTY

Reduce global tty symbols; move and rename tty_ldisc_begin() as
n_tty_init() and redefine the N_TTY ldisc ops as file scope.

Signed-off-by: Peter Hurley <peter@hurleysoftware.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

tty: Destroy ldisc instance on hangup

Currently, when the tty is hungup, the ldisc is re-instanced; ie., the
current instance is destroyed and a new instance is created. The purpose
of this design was to guarantee a valid, open ldisc for the lifetime of
the tty.

However, now that tty buffers are owned by and have lifetime equivalent
to the tty_port (since v3.10), any data received immediately after the
ldisc is re-instanced may cause continued driver i/o operations
concurrently with the driver's hangup() operation. For drivers that
shutdown h/w on hangup, this is unexpected and usually bad. For example,
the serial core may free the xmit buffer page concurrently with an
in-progress write() operation (triggered by echo).

With the existing stable and robust ldisc reference handling, the
cleaned-up tty_reopen(), the straggling unsafe ldisc use cleaned up, and
the preparation to properly handle a NULL tty->ldisc, the ldisc instance
can be destroyed and only re-instanced when the tty is re-opened.

If the tty was opened as /dev/console or /dev/tty0, the original behavior
of re-instancing the ldisc is retained (the 'reinit' parameter to
tty_ldisc_hangup() is true). This is required since those file descriptors
are never hungup.

This patch has neglible impact on userspace; the tty file_operations ptr
is changed to point to the hungup file operations _before_ the ldisc
instance is destroyed, so only racing file operations might now retrieve
a NULL ldisc reference (which is simply handled as if the hungup file
operation had been called instead -- see "tty: Prepare for destroying
line discipline on hangup").

This resolves a long-standing FIXME and several crash reports.

Signed-off-by: Peter Hurley <peter@hurleysoftware.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

tty: Use 'disc' for line discipline index name

tty->ldisc is a ptr to struct tty_ldisc, but unfortunately 'ldisc' is
also used as a parameter or local name to refer to the line discipline
index value (ie, N_TTY, N_GSM, etc.); instead prefer the name used
by the line discipline registration/ref counting functions.

Signed-off-by: Peter Hurley <peter@hurleysoftware.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

tty: Remove __lockfunc annotation from tty lock functions

The tty lock/unlock code does not belong in the special lockfunc section
which is treated specially by stack backtraces.

Signed-off-by: Peter Hurley <peter@hurleysoftware.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

tty: Re-declare tty_driver_remove_tty() file scope

tty_driver_remove_tty() is only local-scope; declare as static.

Signed-off-by: Peter Hurley <peter@hurleysoftware.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

tty: Fix tty_init_termios() declaration

tty_init_termios() never returns an error; re-declare as void. Remove
unnecessary error handling from callers. Remove extern declarations
of tty_free_termios() and free_tty_struct() and re-declare in file
scope.

Signed-off-by: Peter Hurley <peter@hurleysoftware.com>
Acked-by: Johan Hovold <johan@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

tty: Fix ldisc leak in failed tty_init_dev()

release_tty() leaks the ldisc instance when called directly (rather
than when releasing the file descriptor from tty_release()).

Since tty_ldisc_release() clears tty->ldisc, releasing the ldisc
instance at tty teardown if tty->ldisc is non-null is not in danger
of double-releasing the ldisc.

Remove deinitialize_tty_struct() now that free_tty_struct() always
performs the tty_ldisc_deinit().

Signed-off-by: Peter Hurley <peter@hurleysoftware.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

tty: Wait interruptibly for tty lock on reopen

Allow a signal to interrupt the wait for a tty reopen; eg., if
the tty has starting final close and is waiting for the device to
drain.

Signed-off-by: Peter Hurley <peter@hurleysoftware.com>
Cc: stable <stable@vger.kernel.org> # 4.4
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

tty: Remove dead tty_write_flush() declaration and macro

tty_write_flush() has no definition and the TTY_WRITE_FLUSH() macro
is never invoked; remove.

Signed-off-by: Peter Hurley <peter@hurleysoftware.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

tty: Remove __func__ from tty_debug() macro

Now that tty_debug() macro uses pr_debug(), the function name can
be printed when using dynamic debug; printing the function name within
the format string is redundant.

Remove the __func__ parameter and print specifier from the format string.
Add context to messages for when the function name is not printed by
dynamic debug, or when dynamic debug is not enabled.

Signed-off-by: Peter Hurley <peter@hurleysoftware.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

tty: Define tty_*() printk macros

Since not all ttys are devices (eg., SysV ptys), dev_*() printk macros
cannot be used. Define tty_*() printk macros that output in similar
format to dev_*() macros (ie., <driver> <tty>: .....).

Transform the most-trivial printk( LEVEL ...) usage to tty_*() usage.
NB: The function name has been eliminated from messages with unique
context, or prefixed to the format when given.

Signed-off-by: Peter Hurley <peter@hurleysoftware.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

tty: core: Add helper fn to deref tty driver name

Similar to tty_name(), add tty_driver_name() helper to safely
dereference tty->driver->name (otherwise return empty string).

Signed-off-by: Peter Hurley <peter@hurleysoftware.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

tty: Make tty_paranoia_check() file scope

tty_paranoia_check() is only used within drivers/tty/tty_io.c;
remove extern declaration in header and limit symbol to file scope.

Signed-off-by: Peter Hurley <peter@hurleysoftware.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

tty: Improve tty_debug() macro

Incorporate suggestions for tty core debug macro improvements
- printk(KERN_DEBUG) => pr_debug()
- ##args => ##__VA_ARGS__
- remove do {} while()
- output tty_name() first

cc: Joe Perches <joe@perches.com>
Signed-off-by: Peter Hurley <peter@hurleysoftware.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

tty: audit: Fix audit source

The data to audit/record is in the 'from' buffer (ie., the input
read buffer).

Fixes: 72586c6061ab ("n_tty: Fix auditing support for cannonical mode")
Cc: stable <stable@vger.kernel.org> # 4.1+
Cc: Miloslav Trmač <mitr@redhat.com>
Signed-off-by: Peter Hurley <peter@hurleysoftware.com>
Acked-by: Laura Abbott <labbott@fedoraproject.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

tty: Abstract tty buffer work

Introduce API functions to restart and cancel tty buffer work, rather
than manipulate buffer work directly.

Signed-off-by: Peter Hurley <peter@hurleysoftware.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

tty: Combine SIGTTOU/SIGTTIN handling

The job_control() check in n_tty_read() has nearly identical purpose
and results as tty_check_change(). Both functions' purpose is to
determine if the current task's pgrp is the foreground pgrp for the tty,
and if not, to signal the current pgrp.

Introduce __tty_check_change() which takes the signal to send
and performs the shared operations for job control() and
tty_check_change().

Signed-off-by: Peter Hurley <peter@hurleysoftware.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

tty: Remove wait_event_interruptible_tty()

In-tree users of wait_event_interruptible_tty() have been removed;
remove.

Signed-off-by: Peter Hurley <peter@hurleysoftware.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

tty: Remove tty_port::close_wait

With the removal of tty_wait_until_sent_from_close(), tty drivers
no longer wait during open for parallel closes to complete (instead,
the tty core waits before calling the driver open() method). Thus,
the close_wait waitqueue is no longer used for waiting.

Remove struct tty_port::close_wait.

Signed-off-by: Peter Hurley <peter@hurleysoftware.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

tty: Remove tty_wait_until_sent_from_close()

tty_wait_until_sent_from_close() drops the tty lock while waiting
for the tty driver to finish sending previously accepted data (ie.,
data remaining in its write buffer and transmit fifo).

tty_wait_until_sent_from_close() was added by commit a57a7bf3fc7e
("TTY: define tty_wait_until_sent_from_close") to prevent the entire
tty subsystem from being unable to open new ttys while waiting for
one tty to close while output drained.

However, since commit 0911261d4cb6 ("tty: Don't take tty_mutex for tty
count changes"), holding a tty lock while closing does not prevent other
ttys from being opened/closed/hung up, but only prevents lifetime event
changes for the tty under lock.

Holding the tty lock while waiting for output to drain does prevent
parallel non-blocking opens (O_NONBLOCK) from advancing or returning
while the tty lock is held. However, all parallel opens _already_
block even if the tty lock is dropped while closing and the parallel
open advances. Blocking in open has been in mainline since at least 2.6.29
(see tty_port_block_til_ready(); note the test for O_NONBLOCK is _after_
the wait while ASYNC_CLOSING).

IOW, before this patch a non-blocking open will sleep anyway for the
_entire_ duration of a parallel hardware shutdown, and when it wakes, the
error return will cause a release of its tty, and it will restart with
a fresh attempt to open. Similarly with a blocking open that is already
waiting; when it's woken, the hardware shutdown has already completed
to ASYNC_INITIALIZED is not set, which forces a release and restart as
well.

So, holding the tty lock across the _entire_ close (which is what this
patch does), even while waiting for output to drain, is equivalent to
the current outcome wrt parallel opens.

Cc: Alan Cox <alan@linux.intel.com>
Cc: David Laight <David.Laight@aculab.com>
CC: Arnd Bergmann <arnd@arndb.de>
CC: Karsten Keil <isdn@linux-pingi.de>
CC: linuxppc-dev@lists.ozlabs.org
Signed-off-by: Peter Hurley <peter@hurleysoftware.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

tty: core: Add tty_debug() for printk(KERN_DEBUG) messages

Introduce tty_debug() macro to output uniform debug information for
tty core debug messages (function name and tty name).

Note: printk(KERN_DEBUG) is retained here over pr_debug() since
messages can be enabled in non-DEBUG builds.

Signed-off-by: Peter Hurley <peter@hurleysoftware.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

pty: Fix input race when closing

A read() from a pty master may mistakenly indicate EOF (errno == -EIO)
after the pty slave has closed, even though input data remains to be read.
For example,

pty slave | input worker | pty master
| |
| | n_tty_read()
pty_write() | | input avail? no
add data | | sleep
schedule worker --->| | .
|---> flush_to_ldisc() | .
pty_close() | fill read buffer | .
wait for worker | wakeup reader --->| .
| read buffer full? |---> input avail ? yes
|<--- yes - exit worker | copy 4096 bytes to user
TTY_OTHER_CLOSED <---| |<--- kick worker
| |

**** New read() before worker starts ****

| | n_tty_read()
| | input avail? no
| | TTY_OTHER_CLOSED? yes
| | return -EIO

Several conditions are required to trigger this race:
1. the ldisc read buffer must become full so the input worker exits
2. the read() count parameter must be >= 4096 so the ldisc read buffer
is empty
3. the subsequent read() occurs before the kicked worker has processed
more input

However, the underlying cause of the race is that data is pipelined, while
tty state is not; ie., data already written by the pty slave end is not
yet visible to the pty master end, but state changes by the pty slave end
are visible to the pty master end immediately.

Pipeline the TTY_OTHER_CLOSED state through input worker to the reader.
1. Introduce TTY_OTHER_DONE which is set by the input worker when
TTY_OTHER_CLOSED is set and either the input buffers are flushed or
input processing has completed. Readers/polls are woken when
TTY_OTHER_DONE is set.
2. Reader/poll checks TTY_OTHER_DONE instead of TTY_OTHER_CLOSED.
3. A new input worker is started from pty_close() after setting
TTY_OTHER_CLOSED, which ensures the TTY_OTHER_DONE state will be
set if the last input worker is already finished (or just about to
exit).

Remove tty_flush_to_ldisc(); no in-tree callers.

Fixes: 52bce7f8d4fc ("pty, n_tty: Simplify input processing on final close")
Bugzilla: https://bugzilla.kernel.org/show_bug.cgi?id=96311
BugLink: http://bugs.launchpad.net/bugs/1429756
Cc: <stable@vger.kernel.org> # 3.19+
Reported-by: Andy Whitcroft <apw@canonical.com>
Reported-by: H.J. Lu <hjl.tools@gmail.com>
Signed-off-by: Peter Hurley <peter@hurleysoftware.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

tty: remove buf parameter from tty_name()

tty_name no longer uses the buf parameter, so remove it along with all
the 64 byte stack buffers that used to be passed in.

Mostly generated by the coccinelle script

@depends on patch@
identifier buf;
constant C;
expression tty;
@@
- char buf[C];
<+...
- tty_name(tty, buf)
+ tty_name(tty)
...+>

allmodconfig compiles, so I'm fairly confident the stack buffers
weren't used for other purposes as well.

Signed-off-by: Rasmus Villemoes <linux@rasmusvillemoes.dk>
Reviewed-by: Peter Hurley <peter@hurleysoftware.com>
Acked-by: Jesper Nilsson <jesper.nilsson@axis.com>
Acked-by: Dmitry Torokhov <dmitry.torokhov@gmail.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

tty: constify return type of tty_name

All users of tty_name pass the result directly to a printf-like
function. This means we can actually let tty_name return the literal
"NULL tty" or tty->name directly, avoiding the strcpy and a lot of
medium-sized stack buffers. In preparation for that, make the return
type const char*.

While at it, we can also constify the tty parameter.

Signed-off-by: Rasmus Villemoes <linux@rasmusvillemoes.dk>
Reviewed-by: Peter Hurley <peter@hurleysoftware.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

tty: Re-add external interface for tty_set_termios()

This is needed by Bluetooth hci_uart module to be able to change speed
of Bluetooth controller and local UART.

Signed-off-by: Frederic Danis <frederic.danis@linux.intel.com>
Reviewed-by: Peter Hurley <peter@hurleysoftware.com>
Cc: Marcel Holtmann <marcel@holtmann.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

tty: Remove external interface for tty_set_termios()

tty_set_termios() is an internal helper intended for file scope use.

UART drivers which are capable of driving the RTS pin must
properly handle the tiocmset() method, regardless of termios settings.
A failure to do so is a UART driver bug and should be fixed there.
Do not use this interface to workaround UART driver bugs.

Cc: Johan Hedberg <johan.hedberg@gmail.com>
Cc: <linux-bluetooth@vger.kernel.org>
Signed-off-by: Peter Hurley <peter@hurleysoftware.com>
Acked-by: Marcel Holtmann <marcel@holtmann.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

n_tty: Fix signal handling flushes

BRKINT and ISIG requires input and output flush when a signal char
is received. However, the order of operations is significant since
parallel i/o may be ongoing.

Merge the signal handling for BRKINT with ISIG handling.

Process the signal first. This ensures any ongoing i/o is aborted;
without this, a waiting writer may continue writing after the flush
occurs and after the signal char has been echoed.

Write lock the termios_rwsem, which excludes parallel writers from
pushing new i/o until after the output buffers are flushed; claiming
the write lock is necessary anyway to exclude parallel readers while
the read buffer is flushed.

Subclass the termios_rwsem for ptys since the slave pty performing
the flush may appear to reorder the termios_rwsem->tty buffer lock
lock order; adding annotation clarifies that
slave tty_buffer lock-> slave termios_rwsem -> master tty_buffer lock
is a valid lock order.

Flush the echo buffer. In this context, the echo buffer is 'output'.
Otherwise, the output will appear discontinuous because the output buffer
was cleared which contains older output than the echo buffer.

Open-code the read buffer flush since the input worker does not need
kicking (this is the input worker).

Signed-off-by: Peter Hurley <peter@hurleysoftware.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

pty: Fix buffer flush deadlock

The pty driver does not clear its write buffer when commanded.
This is to avoid an apparent deadlock between parallel flushes from
both pty ends; specifically when handling either BRK or INTR input.
However, parallel flushes from this source is not possible since
the pty master can never be set to BRKINT or ISIG. Parallel flushes
from other sources are possible but these do not threaten deadlocks.

Annotate the tty buffer mutex for lockdep to represent the nested
tty_buffer locking which occurs when the pty slave is processing input
(its buffer mutex held) and receives INTR or BRK and acquires the
linked tty buffer mutex via tty_buffer_flush().

Signed-off-by: Peter Hurley <peter@hurleysoftware.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

tty: Make lock subclasses available for other tty locks

Besides nested legacy_mutex locking which is required on pty pair
teardown, other nested pty operations require lock subclassing.

Move lock subclass definition to tty interface header, include/linux/tty.h,
and document its use.

Signed-off-by: Peter Hurley <peter@hurleysoftware.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

tty: Convert tty->closing to int

tty->closing is a bitfield member; prevent corruption from non-atomic
update by assigning a unique memory location.

Signed-off-by: Peter Hurley <peter@hurleysoftware.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

tty: Remove defunct serial_console_init() declaration

serial_console_init() is not defined by the tty core; remove
declaration.

Note that the powerpc arch boot code contains a serial_console_init()
declaration in arch/powerpc/boot/ops.h which is restricted to
the powerpc arch boot.

Signed-off-by: Peter Hurley <peter@hurleysoftware.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

tty: Remove defunct pcxe_open() declaration

pcxe_open() has no definition in mainline; remove declaration.

Signed-off-by: Peter Hurley <peter@hurleysoftware.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

tty: Flush ldisc buffer atomically with tty flip buffers

tty_ldisc_flush() first clears the line discipline input buffer,
then clears the tty flip buffers. However, this allows for existing
data in the tty flip buffers to be added after the ldisc input
buffer has been cleared, but before the flip buffers have been cleared.

Add an optional ldisc parameter to tty_buffer_flush() to allow
tty_ldisc_flush() to pass the ldisc to clear.

NB: Initially, the plan was to do this automatically in
tty_buffer_flush(). However, an audit of the behavior of existing
line disciplines showed that performing a ldisc buffer flush on
ioctl(TCFLSH) was not always the outcome. For example, some line
disciplines have flush_buffer() methods but not ioctl() methods,
so a ->flush_buffer() command would be unexpected.

Reviewed-by: Alan Cox <alan@linux.intel.com>
Signed-off-by: Peter Hurley <peter@hurleysoftware.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

tty: Remove tty_unhangup() declaration

The tty_unhangup() function is not defined.

Reviewed-by: Alan Cox <alan@linux.intel.com>
Signed-off-by: Peter Hurley <peter@hurleysoftware.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

tty: Preset lock subclass for nested tty locks

Eliminate the requirement of specifying the tty lock nesting at
lock time; instead, set the lock subclass for slave ptys at pty
install (normal ttys and master ptys use subclass 0).

Signed-off-by: Peter Hurley <peter@hurleysoftware.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

tty: Change tty lock order to master->slave

When releasing the master pty, the slave pty also needs to be locked
to prevent concurrent tty count changes for the slave pty and to
ensure that only one parallel master and slave release observe the
final close, and proceed to destruct the pty pair. Conversely, when
releasing the slave pty, locking the master pty is not necessary
(since the master's state can be inferred by the slave tty count).

Introduce tty_lock_slave()/tty_unlock_slave() which acquires/releases
the tty lock of the slave pty. Remove tty_lock_pair()/tty_unlock_pair().

Dropping the tty_lock is no longer required to re-establish a stable
lock order.

Reviewed-by: Alan Cox <alan@linux.intel.com>
Signed-off-by: Peter Hurley <peter@hurleysoftware.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

tty: Simplify tty_ldisc_release() interface

Passing the 'other' tty to tty_ldisc_release() only makes sense
for a pty pair; make o_tty function local instead.

Reviewed-by: Alan Cox <alan@linux.intel.com>
Signed-off-by: Peter Hurley <peter@hurleysoftware.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

tty: Remove TTY_CLOSING

Now that re-open is not permitted for a legacy BSD pty master,
using TTY_CLOSING to indicate when a tty can be torn-down is
no longer necessary.

Reviewed-by: Alan Cox <alan@linux.intel.com>
Signed-off-by: Peter Hurley <peter@hurleysoftware.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

tty: Remove TTY_HUPPING

Now that tty_ldisc_hangup() does not drop the tty lock, it is no
longer possible to observe TTY_HUPPING while holding the tty lock
on another cpu.

Remove TTY_HUPPING bit definition.

Reviewed-by: Alan Cox <alan@linux.intel.com>
Signed-off-by: Peter Hurley <peter@hurleysoftware.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

tty: Remove tty_pair_get_tty()/tty_pair_get_pty() api

tty_pair_get_pty() has no in-tree users and tty_pair_get_tty()
has only one file-local user. Remove the external declarations,
the export declarations, and declare tty_pair_get_tty() static.

Signed-off-by: Peter Hurley <peter@hurleysoftware.com>
Reviewed-by: Alan Cox <alan@linux.intel.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

tty: Fix width of unsigned long bitfield padding

Commit c545b66c6922b002b5fe224a6eaec58c913650b5,
'tty: Serialize tcflow() with other tty flow control changes' and
commit 99416322dd16b810ba74098cc50ef2a844091d35,
'tty: Workaround Alpha non-atomic byte storage in tty_struct' work around
compiler bugs and non-atomic storage on multiple arches by padding
bitfields out to the declared type which is unsigned long. However, the
width varies by arch.

Pad bitfields to actual width of unsigned long (which is BITS_PER_LONG).

Reported-by: Fengguang Wu <fengguang.wu@intel.com>
Signed-off-by: Peter Hurley <peter@hurleysoftware.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

tty: Workaround Alpha non-atomic byte storage in tty_struct

The Alpha EV4/EV5 cpus can corrupt adjacent byte and short data because
those cpus use RMW to store byte and short data. Thus, concurrent adjacent
byte stores could become corrupted, if serialized by a different lock.
tty_struct uses different locks to protect certain fields within the
structure, and thus is vulnerable to byte stores which are not atomic.

Merge the ->ctrl_status byte and packet mode bit, both protected by the
->ctrl_lock, into an unsigned long.

The padding bits are necessary to force the compiler to allocate the
type specified; otherwise, gcc will ignore the type specifier and
allocate the minimum number of bytes required to store the bitfield.
In turn, this would allow Alpha EV4/EV5 cpus to corrupt adjacent byte
or short storage (because those cpus use RMW to store byte and short data).

gcc versions < 4.7.2 will also corrupt storage adjacent to bitfields
smaller than unsigned long on ia64, ppc64, hppa64, and sparc64, thus
requiring more than unsigned int storage (which would otherwise be
sufficient to fix the Alpha non-atomic storage problem).

Signed-off-by: Peter Hurley <peter@hurleysoftware.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

tty: Move and rename send_prio_char() as tty_send_xchar()

Relocate the file-scope function, send_prio_char(), as a global
helper tty_send_xchar(). Remove the global declarations for
tty_write_lock()/tty_write_unlock(), as these are file-scope only now.

Signed-off-by: Peter Hurley <peter@hurleysoftware.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

tty: Serialize tcflow() with other tty flow control changes

Use newly-introduced tty->flow_lock to serialize updates to
tty->flow_stopped (via tcflow()) and with concurrent tty flow
control changes from other sources.

Merge the storage for ->stopped and ->flow_stopped, now that both
flags are serialized by ->flow_lock.

The padding bits are necessary to force the compiler to allocate the
type specified; otherwise, gcc will ignore the type specifier and
allocate the minimum number of bytes necessary to store the bitfield.
In turn, this would allow Alpha EV4 and EV5 cpus to corrupt adjacent
byte storage because those cpus use RMW to store byte and short data.

gcc versions < 4.7.2 will also corrupt storage adjacent to bitfields
smaller than unsigned long on ia64, ppc64, hppa64 and sparc64, thus
requiring more than unsigned int storage (which would otherwise be
sufficient to workaround the Alpha non-atomic byte/short storage problem).

Signed-off-by: Peter Hurley <peter@hurleysoftware.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

tty: Serialize tty flow control changes with flow_lock

Without serialization, the flow control state can become inverted
wrt. the actual hardware state. For example,

CPU 0 | CPU 1
stop_tty() |
lock ctrl_lock |
tty->stopped = 1 |
unlock ctrl_lock |
| start_tty()
| lock ctrl_lock
| tty->stopped = 0
| unlock ctrl_lock
| driver->start()
driver->stop() |

In this case, the flow control state now indicates the tty has
been started, but the actual hardware state has actually been stopped.

Introduce tty->flow_lock spinlock to serialize tty flow control changes.
Split out unlocked __start_tty()/__stop_tty() flavors for use by
ioctl(TCXONC) in follow-on patch.

Signed-off-by: Peter Hurley <peter@hurleysoftware.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

tty: Convert tty_struct bitfield to ints

The stopped, hw_stopped, flow_stopped and packet bits are smp-unsafe
and interrupt-unsafe. For example,

CPU 0 | CPU 1
|
tty->flow_stopped = 1 | tty->hw_stopped = 0

One of these updates will be corrupted, as the bitwise operation
on the bitfield is non-atomic.

Ensure each flag has a separate memory location, so concurrent
updates do not corrupt orthogonal states. Because DEC Alpha EV4 and EV5
cpus (from 1995) perform RMW on smaller-than-machine-word storage,
"separate memory location" must be int instead of byte.

Signed-off-by: Peter Hurley <peter@hurleysoftware.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers: tty: Merge alloc_tty_struct and initialize_tty_struct

The two functions alloc_tty_struct and initialize_tty_struct are
always called together. Merge them into alloc_tty_struct, updating its
prototype and the only two callers of these functions.

Signed-off-by: Rasmus Villemoes <linux@rasmusvillemoes.dk>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

Revert "tty: Fix race condition between __tty_buffer_request_room and flush_to_ldisc"

This reverts commit 6a20dbd6caa2358716136144bf524331d70b1e03.

Although the commit correctly identifies an unsafe race condition
between __tty_buffer_request_room() and flush_to_ldisc(), the commit
fixes the race with an unnecessary spinlock in a lockless algorithm.

The follow-on commit, "tty: Fix lockless tty buffer race" fixes
the race locklessly.

Signed-off-by: Peter Hurley <peter@hurleysoftware.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

tty: Fix race condition between __tty_buffer_request_room and flush_to_ldisc

The race was introduced while development of linux-3.11 by
e8437d7ecbc50198705331449367d401ebb3181f and
e9975fdec0138f1b2a85b9624e41660abd9865d4.
Originally it was found and reproduced on linux-3.12.15 and
linux-3.12.15-rt25, by sending 500 byte blocks with 115kbaud to the
target uart in a loop with 100 milliseconds delay.

In short:
1. The consumer flush_to_ldisc is on to remove the head tty_buffer.
2. The producer adds a number of bytes, so that a new tty_buffer must
be allocated and added by __tty_buffer_request_room.
3. The consumer removes the head tty_buffer element, without handling
newly committed data.

Detailed example:
* Initial buffer:
* Head, Tail -> 0: used=250; commit=250; read=240; next=NULL
* Consumer: ''flush_to_ldisc''
* consumed 10 Byte
* buffer:
* Head, Tail -> 0: used=250; commit=250; read=250; next=NULL
{{{
count = head->commit - head->read; // count = 0
if (!count) { // enter
// INTERRUPTED BY PRODUCER ->
if (head->next == NULL)
break;
buf->head = head->next;
tty_buffer_free(port, head);
continue;
}
}}}
* Producer: tty_insert_flip_... 10 bytes + tty_flip_buffer_push
* buffer:
* Head, Tail -> 0: used=250; commit=250; read=250; next=NULL
* added 6 bytes: head-element filled to maximum.
* buffer:
* Head, Tail -> 0: used=256; commit=250; read=250; next=NULL
* added 4 bytes: __tty_buffer_request_room is called
* buffer:
* Head -> 0: used=256; commit=256; read=250; next=1
* Tail -> 1: used=4; commit=0; read=250 next=NULL
* push (tty_flip_buffer_push)
* buffer:
* Head -> 0: used=256; commit=256; read=250; next=1
* Tail -> 1: used=4; commit=4; read=250 next=NULL
* Consumer
{{{
count = head->commit - head->read;
if (!count) {
// INTERRUPTED BY PRODUCER <-
if (head->next == NULL) // -> no break
break;
buf->head = head->next;
tty_buffer_free(port, head);
// ERROR: tty_buffer head freed -> 6 bytes lost
continue;
}
}}}

This patch reintroduces a spin_lock to protect this case. Perhaps later
a lock-less solution could be found.

Signed-off-by: Manfred Schlaegl <manfred.schlaegl@gmx.at>
Cc: stable <stable@vger.kernel.org> # 3.11
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

tty: Fix low_latency BUG

The user-settable knob, low_latency, has been the source of
several BUG reports which stem from flush_to_ldisc() running
in interrupt context. Since 3.12, which added several sleeping
locks (termios_rwsem and buf->lock) to the input processing path,
the frequency of these BUG reports has increased.

Note that changes in 3.12 did not introduce this regression;
sleeping locks were first added to the input processing path
with the removal of the BKL from N_TTY in commit
a88a69c91256418c5907c2f1f8a0ec0a36f9e6cc,
'n_tty: Fix loss of echoed characters and remove bkl from n_tty'
and later in commit 38db89799bdf11625a831c5af33938dcb11908b6,
'tty: throttling race fix'. Since those changes, executing
flush_to_ldisc() in interrupt_context (ie, low_latency set), is unsafe.

However, since most devices do not validate if the low_latency
setting is appropriate for the context (process or interrupt) in
which they receive data, some reports are due to misconfiguration.
Further, serial dma devices for which dma fails, resort to
interrupt receiving as a backup without resetting low_latency.

Historically, low_latency was used to force wake-up the reading
process rather than wait for the next scheduler tick. The
effect was to trim multiple milliseconds of latency from
when the process would receive new data.

Recent tests [1] have shown that the reading process now receives
data with only 10's of microseconds latency without low_latency set.

Remove the low_latency rx steering from tty_flip_buffer_push();
however, leave the knob as an optional hint to drivers that can
tune their rx fifos and such like. Cleanup stale code comments
regarding low_latency.

[1] https://lkml.org/lkml/2014/2/20/434

"Yay.. thats an annoying historical pain in the butt gone."
-- Alan Cox

Reported-by: Beat Bolli <bbolli@ewanet.ch>
Reported-by: Pavel Roskin <proski@gnu.org>
Acked-by: David Sterba <dsterba@suse.cz>
Cc: Grant Edwards <grant.b.edwards@gmail.com>
Cc: Stanislaw Gruszka <sgruszka@redhat.com>
Cc: Hal Murray <murray+fedora@ip-64-139-1-69.sjc.megapath.net>
Cc: <stable@vger.kernel.org> # 3.12.x+
Signed-off-by: Peter Hurley <peter@hurleysoftware.com>
Signed-off-by: Alan Cox <alan@linux.intel.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

tty: Fix ref counting for port krefs

The tty core supports two models for handling tty_port lifetimes;
the tty_port can use the kref supplied by tty_port (which will
automatically destruct the tty_port when the ref count drops to
zero) or it can destruct the tty_port manually.

For tty drivers that choose to use the port kref to manage the
tty_port lifetime, it is not possible to safely acquire a port
reference conditionally. If the last reference is released after
evaluating the condition but before acquiring the reference, a
bogus reference will be held while the tty_port destruction
commences.

Rather, only acquire a port reference if the ref count is non-zero
and allow the caller to distinguish if a reference has successfully
been acquired.

Cc: Jiri Slaby <jslaby@suse.cz>
Signed-off-by: Peter Hurley <peter@hurleysoftware.com>
Acked-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Tested-By: Alexander Holler <holler@ahsoftware.de>
Signed-off-by: Marcel Holtmann <marcel@holtmann.org>

tty: Add C_CMSPAR(tty)

Add the missing C_CMSPAR(tty) macro.

Signed-off-by: Andrew Lunn <andrew@lunn.ch>
Signed-off-by: Johan Hovold <jhovold@gmail.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

tty: Removing the deprecated function tty_vhangup_locked()

The function tty_vhangup_locked() was deprecated, removed it
from the tty.h also.

Signed-off-by: Liu, Chuansheng <chuansheng.liu@intel.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

tty: Halve flip buffer GFP_ATOMIC memory consumption

tty flip buffers use GFP_ATOMIC allocations for received data
which is to be processed by the line discipline. For each byte
received, an extra byte is used to indicate the error status of
that byte.

Instead, if the received data is error-free, encode the entire
buffer without status bytes.

Signed-off-by: Peter Hurley <peter@hurleysoftware.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

tty: Rename tty buffer memory_used field

Trim up the memory_used field name to mem_used.

Signed-off-by: Peter Hurley <peter@hurleysoftware.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

tty: Enable configurable tty flip buffer limit

Allow driver to configure its maximum flip buffer memory
consumption/limit. This is necessary for very-high speed line
rates (in excess of 10MB/sec) because the flip buffers can
be saturated before the line discipline has a chance to
throttle the input.

Signed-off-by: Peter Hurley <peter@hurleysoftware.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

sched/wait: Make the __wait_event*() interface more friendly

Change all __wait_event*() implementations to match the corresponding
wait_event*() signature for convenience.

In particular this does away with the weird 'ret' logic. Since there
are __wait_event*() users this requires we update them too.

Reviewed-by: Oleg Nesterov <oleg@redhat.com>
Signed-off-by: Peter Zijlstra <peterz@infradead.org>
Link: http://lkml.kernel.org/r/20131002092529.042563462@infradead.org
Signed-off-by: Ingo Molnar <mingo@kernel.org>

sched/wait: Collapse __wait_event_interruptible_tty()

Reduce macro complexity by using the new ___wait_event() helper.
No change in behaviour, identical generated code.

Reviewed-by: Oleg Nesterov <oleg@redhat.com>
Signed-off-by: Peter Zijlstra <peterz@infradead.org>
Link: http://lkml.kernel.org/r/20131002092528.831085521@infradead.org
Signed-off-by: Ingo Molnar <mingo@kernel.org>

sched/wait: Make the signal_pending() checks consistent

There's two patterns to check signals in the __wait_event*() macros:

if (!signal_pending(current)) {
schedule();
continue;
}
ret = -ERESTARTSYS;
break;

And the more natural:

if (signal_pending(current)) {
ret = -ERESTARTSYS;
break;
}
schedule();

Change them all into the latter form.

Reviewed-by: Oleg Nesterov <oleg@redhat.com>
Signed-off-by: Peter Zijlstra <peterz@infradead.org>
Link: http://lkml.kernel.org/r/20131002092527.956416254@infradead.org
Signed-off-by: Ingo Molnar <mingo@kernel.org>

tty: Remove unused drop() method from tty_port interface

Although originally conceived as a hook for port drivers to know
when a port reference is dropped, no driver uses this method.

Signed-off-by: Peter Hurley <peter@hurleysoftware.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

tty: Fix lock order in tty_do_resize()

Commits 6a1c0680cf3ba94356ecd58833e1540c93472a57 and
9356b535fcb71db494fc434acceb79f56d15bda2, respectively
'tty: Convert termios_mutex to termios_rwsem' and
'n_tty: Access termios values safely'
introduced a circular lock dependency with console_lock and
termios_rwsem.

The lockdep report [1] shows that n_tty_write() will attempt
to claim console_lock while holding the termios_rwsem, whereas
tty_do_resize() may already hold the console_lock while
claiming the termios_rwsem.

Since n_tty_write() and tty_do_resize() do not contend
over the same data -- the tty->winsize structure -- correct
the lock dependency by introducing a new lock which
specifically serializes access to tty->winsize only.

[1] Lockdep report

======================================================
[ INFO: possible circular locking dependency detected ]
3.10.0-0+tip-xeon+lockdep #0+tip Not tainted
-------------------------------------------------------
modprobe/277 is trying to acquire lock:
(&tty->termios_rwsem){++++..}, at: [<ffffffff81452656>] tty_do_resize+0x36/0xe0

but task is already holding lock:
((fb_notifier_list).rwsem){.+.+.+}, at: [<ffffffff8107aac6>] __blocking_notifier_call_chain+0x56/0xc0

which lock already depends on the new lock.

the existing dependency chain (in reverse order) is:

-> #2 ((fb_notifier_list).rwsem){.+.+.+}:
[<ffffffff810b6d62>] lock_acquire+0x92/0x1f0
[<ffffffff8175b797>] down_read+0x47/0x5c
[<ffffffff8107aac6>] __blocking_notifier_call_chain+0x56/0xc0
[<ffffffff8107ab46>] blocking_notifier_call_chain+0x16/0x20
[<ffffffff813d7c0b>] fb_notifier_call_chain+0x1b/0x20
[<ffffffff813d95b2>] register_framebuffer+0x1e2/0x320
[<ffffffffa01043e1>] drm_fb_helper_initial_config+0x371/0x540 [drm_kms_helper]
[<ffffffffa01bcb05>] nouveau_fbcon_init+0x105/0x140 [nouveau]
[<ffffffffa01ad0af>] nouveau_drm_load+0x43f/0x610 [nouveau]
[<ffffffffa008a79e>] drm_get_pci_dev+0x17e/0x2a0 [drm]
[<ffffffffa01ad4da>] nouveau_drm_probe+0x25a/0x2a0 [nouveau]
[<ffffffff813b13db>] local_pci_probe+0x4b/0x80
[<ffffffff813b1701>] pci_device_probe+0x111/0x120
[<ffffffff814977eb>] driver_probe_device+0x8b/0x3a0
[<ffffffff81497bab>] __driver_attach+0xab/0xb0
[<ffffffff814956ad>] bus_for_each_dev+0x5d/0xa0
[<ffffffff814971fe>] driver_attach+0x1e/0x20
[<ffffffff81496cc1>] bus_add_driver+0x111/0x290
[<ffffffff814982b7>] driver_register+0x77/0x170
[<ffffffff813b0454>] __pci_register_driver+0x64/0x70
[<ffffffffa008a9da>] drm_pci_init+0x11a/0x130 [drm]
[<ffffffffa022a04d>] nouveau_drm_init+0x4d/0x1000 [nouveau]
[<ffffffff810002ea>] do_one_initcall+0xea/0x1a0
[<ffffffff810c54cb>] load_module+0x123b/0x1bf0
[<ffffffff810c5f57>] SyS_init_module+0xd7/0x120
[<ffffffff817677c2>] system_call_fastpath+0x16/0x1b

-> #1 (console_lock){+.+.+.}:
[<ffffffff810b6d62>] lock_acquire+0x92/0x1f0
[<ffffffff810430a7>] console_lock+0x77/0x80
[<ffffffff8146b2a1>] con_flush_chars+0x31/0x50
[<ffffffff8145780c>] n_tty_write+0x1ec/0x4d0
[<ffffffff814541b9>] tty_write+0x159/0x2e0
[<ffffffff814543f5>] redirected_tty_write+0xb5/0xc0
[<ffffffff811ab9d5>] vfs_write+0xc5/0x1f0
[<ffffffff811abec5>] SyS_write+0x55/0xa0
[<ffffffff817677c2>] system_call_fastpath+0x16/0x1b

-> #0 (&tty->termios_rwsem){++++..}:
[<ffffffff810b65c3>] __lock_acquire+0x1c43/0x1d30
[<ffffffff810b6d62>] lock_acquire+0x92/0x1f0
[<ffffffff8175b724>] down_write+0x44/0x70
[<ffffffff81452656>] tty_do_resize+0x36/0xe0
[<ffffffff8146c841>] vc_do_resize+0x3e1/0x4c0
[<ffffffff8146c99f>] vc_resize+0x1f/0x30
[<ffffffff813e4535>] fbcon_init+0x385/0x5a0
[<ffffffff8146a4bc>] visual_init+0xbc/0x120
[<ffffffff8146cd13>] do_bind_con_driver+0x163/0x320
[<ffffffff8146cfa1>] do_take_over_console+0x61/0x70
[<ffffffff813e2b93>] do_fbcon_takeover+0x63/0xc0
[<ffffffff813e67a5>] fbcon_event_notify+0x715/0x820
[<ffffffff81762f9d>] notifier_call_chain+0x5d/0x110
[<ffffffff8107aadc>] __blocking_notifier_call_chain+0x6c/0xc0
[<ffffffff8107ab46>] blocking_notifier_call_chain+0x16/0x20
[<ffffffff813d7c0b>] fb_notifier_call_chain+0x1b/0x20
[<ffffffff813d95b2>] register_framebuffer+0x1e2/0x320
[<ffffffffa01043e1>] drm_fb_helper_initial_config+0x371/0x540 [drm_kms_helper]
[<ffffffffa01bcb05>] nouveau_fbcon_init+0x105/0x140 [nouveau]
[<ffffffffa01ad0af>] nouveau_drm_load+0x43f/0x610 [nouveau]
[<ffffffffa008a79e>] drm_get_pci_dev+0x17e/0x2a0 [drm]
[<ffffffffa01ad4da>] nouveau_drm_probe+0x25a/0x2a0 [nouveau]
[<ffffffff813b13db>] local_pci_probe+0x4b/0x80
[<ffffffff813b1701>] pci_device_probe+0x111/0x120
[<ffffffff814977eb>] driver_probe_device+0x8b/0x3a0
[<ffffffff81497bab>] __driver_attach+0xab/0xb0
[<ffffffff814956ad>] bus_for_each_dev+0x5d/0xa0
[<ffffffff814971fe>] driver_attach+0x1e/0x20
[<ffffffff81496cc1>] bus_add_driver+0x111/0x290
[<ffffffff814982b7>] driver_register+0x77/0x170
[<ffffffff813b0454>] __pci_register_driver+0x64/0x70
[<ffffffffa008a9da>] drm_pci_init+0x11a/0x130 [drm]
[<ffffffffa022a04d>] nouveau_drm_init+0x4d/0x1000 [nouveau]
[<ffffffff810002ea>] do_one_initcall+0xea/0x1a0
[<ffffffff810c54cb>] load_module+0x123b/0x1bf0
[<ffffffff810c5f57>] SyS_init_module+0xd7/0x120
[<ffffffff817677c2>] system_call_fastpath+0x16/0x1b

other info that might help us debug this:

Chain exists of:
&tty->termios_rwsem --> console_lock --> (fb_notifier_list).rwsem

Possible unsafe locking scenario:

CPU0 CPU1
---- ----
lock((fb_notifier_list).rwsem);
lock(console_lock);
lock((fb_notifier_list).rwsem);
lock(&tty->termios_rwsem);

*** DEADLOCK ***

7 locks held by modprobe/277:
#0: (&__lockdep_no_validate__){......}, at: [<ffffffff81497b5b>] __driver_attach+0x5b/0xb0
#1: (&__lockdep_no_validate__){......}, at: [<ffffffff81497b69>] __driver_attach+0x69/0xb0
#2: (drm_global_mutex){+.+.+.}, at: [<ffffffffa008a6dd>] drm_get_pci_dev+0xbd/0x2a0 [drm]
#3: (registration_lock){+.+.+.}, at: [<ffffffff813d93f5>] register_framebuffer+0x25/0x320
#4: (&fb_info->lock){+.+.+.}, at: [<ffffffff813d8116>] lock_fb_info+0x26/0x60
#5: (console_lock){+.+.+.}, at: [<ffffffff813d95a4>] register_framebuffer+0x1d4/0x320
#6: ((fb_notifier_list).rwsem){.+.+.+}, at: [<ffffffff8107aac6>] __blocking_notifier_call_chain+0x56/0xc0

stack backtrace:
CPU: 0 PID: 277 Comm: modprobe Not tainted 3.10.0-0+tip-xeon+lockdep #0+tip
Hardware name: Dell Inc. Precision WorkStation T5400 /0RW203, BIOS A11 04/30/2012
ffffffff8213e5e0 ffff8802aa2fb298 ffffffff81755f19 ffff8802aa2fb2e8
ffffffff8174f506 ffff8802aa2fa000 ffff8802aa2fb378 ffff8802aa2ea8e8
ffff8802aa2ea910 ffff8802aa2ea8e8 0000000000000006 0000000000000007
Call Trace:
[<ffffffff81755f19>] dump_stack+0x19/0x1b
[<ffffffff8174f506>] print_circular_bug+0x1fb/0x20c
[<ffffffff810b65c3>] __lock_acquire+0x1c43/0x1d30
[<ffffffff810b775e>] ? mark_held_locks+0xae/0x120
[<ffffffff810b78d5>] ? trace_hardirqs_on_caller+0x105/0x1d0
[<ffffffff810b6d62>] lock_acquire+0x92/0x1f0
[<ffffffff81452656>] ? tty_do_resize+0x36/0xe0
[<ffffffff8175b724>] down_write+0x44/0x70
[<ffffffff81452656>] ? tty_do_resize+0x36/0xe0
[<ffffffff81452656>] tty_do_resize+0x36/0xe0
[<ffffffff8146c841>] vc_do_resize+0x3e1/0x4c0
[<ffffffff8146c99f>] vc_resize+0x1f/0x30
[<ffffffff813e4535>] fbcon_init+0x385/0x5a0
[<ffffffff8146a4bc>] visual_init+0xbc/0x120
[<ffffffff8146cd13>] do_bind_con_driver+0x163/0x320
[<ffffffff8146cfa1>] do_take_over_console+0x61/0x70
[<ffffffff813e2b93>] do_fbcon_takeover+0x63/0xc0
[<ffffffff813e67a5>] fbcon_event_notify+0x715/0x820
[<ffffffff81762f9d>] notifier_call_chain+0x5d/0x110
[<ffffffff8107aadc>] __blocking_notifier_call_chain+0x6c/0xc0
[<ffffffff8107ab46>] blocking_notifier_call_chain+0x16/0x20
[<ffffffff813d7c0b>] fb_notifier_call_chain+0x1b/0x20
[<ffffffff813d95b2>] register_framebuffer+0x1e2/0x320
[<ffffffffa01043e1>] drm_fb_helper_initial_config+0x371/0x540 [drm_kms_helper]
[<ffffffff8173cbcb>] ? kmemleak_alloc+0x5b/0xc0
[<ffffffff81198874>] ? kmem_cache_alloc_trace+0x104/0x290
[<ffffffffa01035e1>] ? drm_fb_helper_single_add_all_connectors+0x81/0xf0 [drm_kms_helper]
[<ffffffffa01bcb05>] nouveau_fbcon_init+0x105/0x140 [nouveau]
[<ffffffffa01ad0af>] nouveau_drm_load+0x43f/0x610 [nouveau]
[<ffffffffa008a79e>] drm_get_pci_dev+0x17e/0x2a0 [drm]
[<ffffffffa01ad4da>] nouveau_drm_probe+0x25a/0x2a0 [nouveau]
[<ffffffff8175f162>] ? _raw_spin_unlock_irqrestore+0x42/0x80
[<ffffffff813b13db>] local_pci_probe+0x4b/0x80
[<ffffffff813b1701>] pci_device_probe+0x111/0x120
[<ffffffff814977eb>] driver_probe_device+0x8b/0x3a0
[<ffffffff81497bab>] __driver_attach+0xab/0xb0
[<ffffffff81497b00>] ? driver_probe_device+0x3a0/0x3a0
[<ffffffff814956ad>] bus_for_each_dev+0x5d/0xa0
[<ffffffff814971fe>] driver_attach+0x1e/0x20
[<ffffffff81496cc1>] bus_add_driver+0x111/0x290
[<ffffffffa022a000>] ? 0xffffffffa0229fff
[<ffffffff814982b7>] driver_register+0x77/0x170
[<ffffffffa022a000>] ? 0xffffffffa0229fff
[<ffffffff813b0454>] __pci_register_driver+0x64/0x70
[<ffffffffa008a9da>] drm_pci_init+0x11a/0x130 [drm]
[<ffffffffa022a000>] ? 0xffffffffa0229fff
[<ffffffffa022a000>] ? 0xffffffffa0229fff
[<ffffffffa022a04d>] nouveau_drm_init+0x4d/0x1000 [nouveau]
[<ffffffff810002ea>] do_one_initcall+0xea/0x1a0
[<ffffffff810c54cb>] load_module+0x123b/0x1bf0
[<ffffffff81399a50>] ? ddebug_proc_open+0xb0/0xb0
[<ffffffff813855ae>] ? trace_hardirqs_on_thunk+0x3a/0x3f
[<ffffffff810c5f57>] SyS_init_module+0xd7/0x120
[<ffffffff817677c2>] system_call_fastpath+0x16/0x1b

Signed-off-by: Peter Hurley <peter@hurleysoftware.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

n_tty: Fix EOF push handling

In canonical mode, an EOF which is not the first character of the line
causes read() to complete and return the number of characters read so
far (commonly referred to as EOF push). However, if the previous read()
returned because the user buffer was full _and_ the next character
is an EOF not at the beginning of the line, read() must not return 0,
thus mistakenly indicating the end-of-file condition.

The TTY_PUSH flag is used to indicate an EOF was received which is not
at the beginning of the line. Because the EOF push condition is
evaluated by a thread other than the read(), multiple EOF pushes can
cause a premature end-of-file to be indicated.

Instead, discover the 'EOF push as first read character' condition
from the read() thread itself, and restart the i/o loop if detected.

Signed-off-by: Peter Hurley <peter@hurleysoftware.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

tty: Remove private constant from global namespace

TTY_BUFFER_PAGE is only used within drivers/tty/tty_buffer.c;
relocate to that file scope.

Signed-off-by: Peter Hurley <peter@hurleysoftware.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

tty: Fix unsafe vt paste_selection()

Convert the tty_buffer_flush() exclusion mechanism to a
public interface - tty_buffer_lock/unlock_exclusive() - and use
the interface to safely write the paste selection to the line
discipline.

Signed-off-by: Peter Hurley <peter@hurleysoftware.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

tty: Use non-atomic state to signal flip buffer flush pending

Atomic bit ops are no longer required to indicate a flip buffer
flush is pending, as the flush_mutex is sufficient barrier.

Remove the unnecessary port .iflags field and localize flip buffer
state to struct tty_bufhead.

Signed-off-by: Peter Hurley <peter@hurleysoftware.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

tty: Avoid false-sharing flip buffer ptrs

Separate the head and tail ptrs to avoid cache-line contention
(so called 'false-sharing') between concurrent threads.

Signed-off-by: Peter Hurley <peter@hurleysoftware.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

tty: Only perform flip buffer flush from tty_buffer_flush()

Now that dropping the buffer lock is not necessary (as result of
converting the spin lock to a mutex), the flip buffer flush no
longer needs to be handled by the buffer work.

Simply signal a flush is required; the buffer work will exit the
i/o loop, which allows tty_buffer_flush() to proceed.

Signed-off-by: Peter Hurley <peter@hurleysoftware.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

tty: Ensure single-threaded flip buffer consumer with mutex

The buffer work may race with parallel tty_buffer_flush. Use a
mutex to guarantee exclusive modify access to the head flip
buffer.

Remove the unneeded spin lock.

Signed-off-by: Peter Hurley <peter@hurleysoftware.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

tty: Track flip buffer memory limit atomically

Lockless flip buffers require atomically updating the bytes-in-use
watermark.

The pty driver also peeks at the watermark value to limit
memory consumption to a much lower value than the default; query
the watermark with new fn, tty_buffer_space_avail().

Signed-off-by: Peter Hurley <peter@hurleysoftware.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

tty: Simplify flip buffer list with 0-sized sentinel

Use a 0-sized sentinel to avoid assigning the head ptr from
the driver side thread. This also eliminates testing head/tail
for NULL.

When the sentinel is first 'consumed' by the buffer work
(or by tty_buffer_flush()), it is detached from the list but not
freed nor added to the free list. Both buffer work and
tty_buffer_flush() continue to preserve at least 1 flip buffer
to which head & tail is pointed.

Signed-off-by: Peter Hurley <peter@hurleysoftware.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

tty: Use lockless flip buffer free list

In preparation for lockless flip buffers, make the flip buffer
free list lockless.

NB: using llist is not the optimal solution, as the driver and
buffer work may contend over the llist head unnecessarily. However,
test measurements indicate this contention is low.

Signed-off-by: Peter Hurley <peter@hurleysoftware.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

tty: Compute flip buffer ptrs

The char_buf_ptr and flag_buf_ptr values are trivially derived from
the .data field offset; compute values as needed.

Fixes a long-standing type-mismatch with the char and flag ptrs.

Signed-off-by: Peter Hurley <peter@hurleysoftware.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

tty: Only guarantee termios read safety for throttle/unthrottle

No tty driver modifies termios during throttle() or unthrottle().
Therefore, only read safety is required.

However, tty_throttle_safe and tty_unthrottle_safe must still be
mutually exclusive; introduce throttle_mutex for that purpose.

Signed-off-by: Peter Hurley <peter@hurleysoftware.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

tty: Convert termios_mutex to termios_rwsem

termios is commonly accessed unsafely (especially by N_TTY)
because the existing mutex forces exclusive access.
Convert existing usage.

Signed-off-by: Peter Hurley <peter@hurleysoftware.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

tty: Make ldisc input flow control concurrency-friendly

Although line discipline receiving is single-producer/single-consumer,
using tty->receive_room to manage flow control creates unnecessary
critical regions requiring additional lock use.

Instead, introduce the optional .receive_buf2() ldisc method which
returns the # of bytes actually received. Serialization is guaranteed
by the caller.

In turn, the line discipline should schedule the buffer work item
whenever space becomes available; ie., when there is room to receive
data and receive_room() previously returned 0 (the buffer work
item stops processing if receive_buf2() returns 0). Note the
'no room' state need not be atomic despite concurrent use by two
threads because only the buffer work thread can set the state and
only the read() thread can clear the state.

Add n_tty_receive_buf2() as the receive_buf2() method for N_TTY.
Provide a public helper function, tty_ldisc_receive_buf(), to use
when directly accessing the receive_buf() methods.

Line disciplines not using input flow control can continue to set
tty->receive_room to a fixed value and only provide the receive_buf()
method.

Signed-off-by: Peter Hurley <peter@hurleysoftware.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

tty: Replace ldisc locking with ldisc_sem

Line discipline locking was performed with a combination of
a mutex, a status bit, a count, and a waitqueue -- basically,
a rw semaphore.

Replace the existing combination with an ld_semaphore.

Fixes:
1) the 'reference acquire after ldisc locked' bug
2) the over-complicated halt mechanism
3) lock order wrt. tty_lock()
4) dropping locks while changing ldisc
5) previously unidentified deadlock while locking ldisc from
both linked ttys concurrently
6) previously unidentified recursive deadlocks

Adds much-needed lockdep diagnostics.

Signed-off-by: Peter Hurley <peter@hurleysoftware.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

n_tty: Encapsulate minimum_to_wake within N_TTY

minimum_to_wake is unique to N_TTY processing, and belongs in
per-ldisc data.

Add the ldisc method, ldisc_ops::fasync(), to notify line disciplines
when signal-driven I/O is enabled or disabled. When enabled for N_TTY
(by fcntl(F_SETFL, O_ASYNC)), blocking reader/polls will be woken
for any readable input. When disabled, blocking reader/polls are not
woken until the read buffer is full.

Canonical mode (L_ICANON(tty), n_tty_data::icanon) is not affected by
the minimum_to_wake setting.

Signed-off-by: Peter Hurley <peter@hurleysoftware.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

tty: Remove TTY_HW_COOK_IN/OUT

No in-tree tty driver supports cooked mode in hardware; remove.

Signed-off-by: Peter Hurley <peter@hurleysoftware.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

proc: Move some bits from linux/proc_fs.h to linux/{of.h,signal.h,tty.h}

Move some bits from linux/proc_fs.h to linux/of.h, signal.h and tty.h.

Also move proc_tty_init() and proc_device_tree_init() to fs/proc/internal.h as
they're internal to procfs.

Signed-off-by: David Howells <dhowells@redhat.com>
Acked-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Acked-by: Grant Likely <grant.likely@secretlab.ca>
cc: devicetree-discuss@lists.ozlabs.org
cc: linux-arch@vger.kernel.org
cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
cc: Jri Slaby <jslaby@suse.cz>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>

audit: push loginuid and sessionid processing down

Since we are always current, we can push a lot of this stuff to the
bottom and get rid of useless interfaces and arguments.

Signed-off-by: Eric Paris <eparis@redhat.com>

audit: stop pushing loginid, uid, sessionid as arguments

We always use current. Stop pulling this when the skb comes in and
pushing it around as arguments. Just get it at the end when you need
it.

Signed-off-by: Eric Paris <eparis@redhat.com>

tty: Don't reenable already enabled ldisc

tty_ldisc_hangup() guarantees the ldisc is enabled (or that there
is no ldisc). Since __tty_hangup() was the only user, re-define
tty_ldisc_enable() in file-scope.

Signed-off-by: Peter Hurley <peter@hurleysoftware.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

tty: Add diagnostic for halted line discipline

Flip buffer work must not be scheduled by the line discipline
after the line discipline has been halted; issue warning.

Note: drivers can still schedule flip buffer work.

Signed-off-by: Peter Hurley <peter@hurleysoftware.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

TTY: add tty_port_tty_hangup helper

It allows for cleaning up on a considerable amount of places. They did
port_get, hangup, kref_put. Now the only thing needed is to call
tty_port_tty_hangup which does exactly that. And they can also decide
whether to consider CLOCAL or completely ignore that.

Signed-off-by: Jiri Slaby <jslaby@suse.cz>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

TTY: add tty_port_tty_wakeup helper

It allows for cleaning up on a considerable amount of places. They did
port_get, wakeup, kref_put. Now the only thing needed is to call
tty_port_tty_wakeup which does exactly that.

One exception is ifx6x60 where tty_wakeup was open-coded. We now call
tty_wakeup properly there.

Signed-off-by: Jiri Slaby <jslaby@suse.cz>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

TTY: do not warn about setting speed via SPD_*

The warning is there since 2.1.69 and we have not seen anybody
reporting it in the past decade. Remove the warning now.

tty_get_baud_rate can now be inline. This gives us one less
EXPORT_SYMBOL.

Signed-off-by: Jiri Slaby <jslaby@suse.cz>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

tty: Add safe tty throttle/unthrottle functions

The tty driver can become stuck throttled due to race conditions
between throttle and unthrottle, when the decision to throttle
or unthrottle is conditional. The following example helps to
illustrate the race:

CPU 0 | CPU 1
|
if (condition A) |
| <processing such that A not true>
| if (!condition A)
| unthrottle()
throttle() |
|

Note the converse is also possible; ie.,

CPU 0 | CPU 1
|
| if (!condition A)
<processing such that A true> |
if (condition A) |
throttle() |
| unthrottle()
|

Add new throttle/unthrottle functions based on the familiar model
of task state and schedule/wake. For example,

while (1) {
tty_set_flow_change(tty, TTY_THROTTLE_SAFE);
if (!condition)
break;
if (!tty_throttle_safe(tty))
break;
}
__tty_set_flow_change(tty, 0);

In this example, if an unthrottle occurs after the condition is
evaluated but before tty_throttle_safe(), then tty_throttle_safe()
will return non-zero, looping and forcing the re-evaluation of
condition.

Reported-by: Vincent Pillet <vincentx.pillet@intel.com>
Signed-off-by: Peter Hurley <peter@hurleysoftware.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

tty: Added a CONFIG_TTY option to allow removal of TTY

The option allows you to remove TTY and compile without errors. This
saves space on systems that won't support TTY interfaces anyway.
bloat-o-meter output is below.

The bulk of this patch consists of Kconfig changes adding "depends on
TTY" to various serial devices and similar drivers that require the TTY
layer. Ideally, these dependencies would occur on a common intermediate
symbol such as SERIO, but most drivers "select SERIO" rather than
"depends on SERIO", and "select" does not respect dependencies.

bloat-o-meter output comparing our previous minimal to new minimal by
removing TTY. The list is filtered to not show removed entries with awk
'$3 != "-"' as the list was very long.

add/remove: 0/226 grow/shrink: 2/14 up/down: 6/-35356 (-35350)
function old new delta
chr_dev_init 166 170 +4
allow_signal 80 82 +2
static.__warned 143 142 -1
disallow_signal 63 62 -1
__set_special_pids 95 94 -1
unregister_console 126 121 -5
start_kernel 546 541 -5
register_console 593 588 -5
copy_from_user 45 40 -5
sys_setsid 128 120 -8
sys_vhangup 32 19 -13
do_exit 1543 1526 -17
bitmap_zero 60 40 -20
arch_local_irq_save 137 117 -20
release_task 674 652 -22
static.spin_unlock_irqrestore 308 260 -48

Signed-off-by: Joe Millenbach <jmillenbach@gmail.com>
Reviewed-by: Jamey Sharp <jamey@minilop.net>
Reviewed-by: Josh Triplett <josh@joshtriplett.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

TTY: switch tty_flip_buffer_push

Now, we start converting tty buffer functions to actually use
tty_port. This will allow us to get rid of the need of tty in many
call sites. Only tty_port will needed and hence no more
tty_port_tty_get in those paths.

Now, the one where most of tty_port_tty_get gets removed:
tty_flip_buffer_push.

IOW we also closed all the races in drivers not using tty_port_tty_get
at all yet.

Also we move tty_flip_buffer_push declaration from include/linux/tty.h
to include/linux/tty_flip.h to all others while we are changing it
anyway.

Signed-off-by: Jiri Slaby <jslaby@suse.cz>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

TTY: move low_latency to tty_port

One point is to have less places where we actually need tty pointer.
The other is that low_latency is bound to buffer processing and
buffers are now in tty_port. So it makes sense to move low_latency to
tty_port too.

Signed-off-by: Jiri Slaby <jslaby@suse.cz>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

TTY: introduce tty_port_destroy

After commit "TTY: move tty buffers to tty_port", the tty buffers are
not freed in some drivers. This is because tty_port_destructor is not
called whenever a tty_port is freed. This was an assumption I counted
with but was unfortunately untrue.

Those using refcounting are safe now, but for those which do not we
introduce a function to be called right before the tty_port is freed
by the drivers.

Signed-off-by: Jiri Slaby <jslaby@suse.cz>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

TTY: move tty buffers to tty_port

So this is it. The big step why we did all the work over the past
kernel releases. Now everything is prepared, so nothing protects us
from doing that big step.

| | \ \ nnnn/^l | |
| | \ / / | |
| '-,.__ => \/ ,-` => | '-,.__
| O __.´´) ( .` | O __.´´)
~~~ ~~ `` ~~~ ~~
The buffers are now in the tty_port structure and we can start
teaching the buffer helpers (insert char/string, flip etc.) to use
tty_port instead of tty_struct all around.

Signed-off-by: Jiri Slaby <jslaby@suse.cz>
Acked-by: Alan Cox <alan@linux.intel.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

TTY: add port -> tty link

For that purpose we have to temporarily introduce a second tty back
pointer into tty_port. It is because serial layer, and maybe others,
still do not use tty_port_tty_set/get. So that we cannot set the
tty_port->tty to NULL at will now.

Yes, the fix would be to convert whole serial layer and all its users
to tty_port_tty_set/get. However we are in the process of removing the
need of tty in most of the call sites, so this would lead to a
duplicated work.

Instead we have now tty_port->itty (internal tty) which will be used
only in flush_to_ldisc. For that one it is ensured that itty is valid
wherever the work is run. IOW, the work is synchronously cancelled
before we set itty to NULL and also before hangup is processed.

After we need only tty_port and not tty_struct in most code, this
shall be changed to tty_port_tty_set/get and itty removed completely.

Signed-off-by: Jiri Slaby <jslaby@suse.cz>
Acked-by: Alan Cox <alan@linux.intel.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

TTY: move TTY_FLUSH* flags to tty_port

They are only TTY buffers specific. And the buffers will go to
tty_port in the next patches. So to remove the need to have both
tty_port and tty_struct at some places, let us move the flags to
tty_port.

Signed-off-by: Jiri Slaby <jslaby@suse.cz>
Acked-by: Alan Cox <alan@linux.intel.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

TTY: move ldisc data from tty_struct: locks

atomic_write_lock is not n_tty specific, so move it up in the
tty_struct.

And since these are the last ones to move, remove also the comment
saying there are some ldisc' members. There are none now.

Signed-off-by: Jiri Slaby <jslaby@suse.cz>
Acked-by: Alan Cox <alan@linux.intel.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

TTY: move ldisc data from tty_struct: read_* and echo_* and canon_* stuff

All the ring-buffers...

Signed-off-by: Jiri Slaby <jslaby@suse.cz>
Acked-by: Alan Cox <alan@linux.intel.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

TTY: move ldisc data from tty_struct: bitmaps

Here we move bitmaps and use DECLARE_BITMAP to declare them in the new
structure. And instead of memset, we use bitmap_zero as it is more
appropriate.

Signed-off-by: Jiri Slaby <jslaby@suse.cz>
Acked-by: Alan Cox <alan@linux.intel.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

TTY: move ldisc data from tty_struct: simple members

Here we start moving all the n_tty related bits from tty_struct to
the newly defined n_tty_data struct in n_tty proper.

In this patch primitive members and bits are moved. The rest will be
done per-partes in the next patches.

Signed-off-by: Jiri Slaby <jslaby@suse.cz>
Acked-by: Alan Cox <alan@linux.intel.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

TTY: audit, stop accessing tty->icount

This is a private member of n_tty. Stop accessing it. Instead, take is
as an argument.

This is needed to allow clean switch of the private members to a
separate private structure of n_tty.

Signed-off-by: Jiri Slaby <jslaby@suse.cz>
Acked-by: Alan Cox <alan@linux.intel.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

UAPI: (Scripted) Disintegrate include/linux

Signed-off-by: David Howells <dhowells@redhat.com>
Acked-by: Arnd Bergmann <arnd@arndb.de>
Acked-by: Thomas Gleixner <tglx@linutronix.de>
Acked-by: Michael Kerrisk <mtk.manpages@gmail.com>
Acked-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Acked-by: Dave Jones <davej@redhat.com>

userns: Convert the audit loginuid to be a kuid

Always store audit loginuids in type kuid_t.

Print loginuids by converting them into uids in the appropriate user
namespace, and then printing the resulting uid.

Modify audit_get_loginuid to return a kuid_t.

Modify audit_set_loginuid to take a kuid_t.

Modify /proc/<pid>/loginuid on read to convert the loginuid into the
user namespace of the opener of the file.

Modify /proc/<pid>/loginud on write to convert the loginuid
rom the user namespace of the opener of the file.

Cc: Al Viro <viro@zeniv.linux.org.uk>
Cc: Eric Paris <eparis@redhat.com>
Cc: Paul Moore <paul@paul-moore.com> ?
Cc: David Miller <davem@davemloft.net>
Signed-off-by: Eric W. Biederman <ebiederm@xmission.com>

tty_register_device_attr updated for tty-next

Added tty_device_create_release() and bound to dev->release in
tty_register_device_attr().
Added tty_port_register_device_attr() and used in uart_add_one_port()
instead of tty_register_device_attr().

Signed-off-by: Tomas Hlavacek <tmshlvck@gmail.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

tty: uartclk value from serial_core exposed to sysfs

Added file /sys/devices/.../tty/ttySX/uartclk to allow reading
uartclk value in struct uart_port in serial_core via sysfs.

tty_register_device() has been generalized and refactored in order
to add support for setting drvdata and attribute_group to the device.

Signed-off-by: Tomas Hlavacek <tmshlvck@gmail.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

serial: add a new helper function

In most of the time, the driver needs to check if the cts flow control
is enabled. But now, the driver checks the ASYNC_CTS_FLOW flag manually,
which is not a grace way. So add a new wraper function to make the code
tidy and clean.

Signed-off-by: Huang Shijie <shijie8@gmail.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

tty: move the async flags from the serial code into the tty includes

These are used with the tty_port flags which are tty generic so move the
flags into a more sensible place. This then makes it possible to add
helpers such as those suggested by Huang Shijie.

Signed-off-by: Alan Cox <alan@linux.intel.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

TTY: add tty_port_link_device

This is for those drivers which do not have dynamic device creation
(do not call tty_port_register_device) and do not want to implement
tty->ops->install (will not call tty_port_install). They still have to
provide the link somehow though.

And this newly added function is exactly to serve that purpose.

Signed-off-by: Jiri Slaby <jslaby@suse.cz>
Acked-by: Alan Cox <alan@linux.intel.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

tty: localise the lock

The termios and other changes mean the other protections needed on the driver
tty arrays should be adequate. Turn it all back on.

This contains pieces folded in from the fixes made to the original patches

| From: Geert Uytterhoeven <geert@linux-m68k.org> (fix m68k)
| From: Paul Gortmaker <paul.gortmaker@windriver.com> (fix cris)
| From: Jiri Kosina <jkosina@suze.cz> (lockdep)
| From: Eric Dumazet <eric.dumazet@gmail.com> (lockdep)

Signed-off-by: Alan Cox <alan@linux.intel.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

tty: Move the handling of the tty release logic

Now that we don't have tty->termios tied to drivers->tty we can untangle
the logic here. In addition we can push the removal logic out of the
destructor path.

At that point we can think about sorting out tty_port and console and all
the other ugly hangovers.

Signed-off-by: Alan Cox <alan@linux.intel.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

tty: move the termios object into the tty

This will let us sort out a whole pile of tty related races. The
alternative would be to keep points and refcount the termios objects.
However
1. They are tiny anyway
2. Many devices don't use the stored copies
3. We can remove a pty special case

Signed-off-by: Alan Cox <alan@linux.intel.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

tty: revert incorrectly applied lock patch

I sent GregKH this after the pre-requisites. He dropped the pre-requesites
for good reason and unfortunately then applied this patch. Without this
reverted you get random kernel memory corruption which will make bisecting
anything between it and the properly applied patches a complete sod.

Signed-off-by: Alan Cox <alan@linux.intel.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

tty: localise the lock

The termios and other changes mean the other protections needed on the driver
tty arrays should be adequate. Turn it all back on.

This contains pieces folded in from the fixes made to the original patches

| From: Geert Uytterhoeven <geert@linux-m68k.org> (fix m68k)
| From: Paul Gortmaker <paul.gortmaker@windriver.com> (fix cris)
| From: Jiri Kosina <jkosina@suze.cz> (lockdep)
| From: Eric Dumazet <eric.dumazet@gmail.com> (lockdep)

Signed-off-by: Alan Cox <alan@linux.intel.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

TTY: add tty_port_register_device helper

This will automatically assign tty_port to tty_driver's port array for
later recall in tty_init_dev. This is intended to be called instead of
tty_register_device.

Signed-off-by: Jiri Slaby <jslaby@suse.cz>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

TTY: provide drivers with tty_port_install

This will be used in tty_ops->install to set tty->port (and to call
tty_standard_install).

Signed-off-by: Jiri Slaby <jslaby@suse.cz>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

tty: Revert the tty locking series, it needs more work

This reverts the tty layer change to use per-tty locking, because it's
not correct yet, and fixing it will require some more deep surgery.

The main revert is d29f3ef39be4 ("tty_lock: Localise the lock"), but
there are several smaller commits that built upon it, they also get
reverted here. The list of reverted commits is:

fde86d310886 - tty: add lockdep annotations
8f6576ad476b - tty: fix ldisc lock inversion trace
d3ca8b64b97e - pty: Fix lock inversion
b1d679afd766 - tty: drop the pty lock during hangup
abcefe5fc357 - tty/amiserial: Add missing argument for tty_unlock()
fd11b42e3598 - cris: fix missing tty arg in wait_event_interruptible_tty call
d29f3ef39be4 - tty_lock: Localise the lock

The revert had a trivial conflict in the 68360serial.c staging driver
that got removed in the meantime.

Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

tty_lock: Localise the lock

In each remaining case the tty_lock is associated with a specific tty. This
means we can now lock on a per tty basis. We do need tty_lock_pair() for
the pty case. Uglier but still a step in the right direction.

[fixed up calls in 3 missing drivers - gregkh]

Signed-off-by: Alan Cox <alan@linux.intel.com>
Acked-by: Arnd Bergmann <arnd@arndb.de>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

Remove all #inclusions of asm/system.h

Remove all #inclusions of asm/system.h preparatory to splitting and killing
it. Performed with the following command:

perl -p -i -e 's!^#\s*include\s*<asm/system[.]h>.*\n!!' `grep -Irl '^#\s*include\s*<asm/system[.]h>' *`

Signed-off-by: David Howells <dhowells@redhat.com>

TTY: provide tty_standard_install helper

There are currently many cut&paste copies of what
tty_driver_install_tty does when custom ->install method is not
provided. Let's get rid of the copies and create a helper with this
setup code.

Signed-off-by: Jiri Slaby <jslaby@suse.cz>
Cc: Havard Skinnemoen <hskinnemoen@google.com>
Acked-by: Alan Cox <alan@linux.intel.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

tty: rework pty count limiting

After adding devpts multiple-insrances sysctl kernel.pty.max limit pty count for
each devpts instance independently, while kernel.pty.nr shows total pty count.

This patch restores sysctl kernel.pty.max as global limit (4096 by default),
adds pty reseve for main devpts (mounted without "newinstance" argument),
and new sysctl to tune it: kernel.pty.reserve (1024 by default)

Also it adds devpts mount option "max=%d" to limit pty count for each devpts
instance independently. (by default NR_UNIX98_PTY_MAX == 2^20)

Thus devpts instances in containers cannot eat up all available pty even if we didn't
set any limits, while with "max" argument we can adjust limits more precisely.

Plus, now open("/dev/ptmx") return -ENOSPC in case lack of pty indexes,
this is more informative than -EIO.

Signed-off-by: Konstantin Khlebnikov <khlebnikov@openvz.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

tty: cleanup prohibition of direct opening for unix98 pty master

cleanup hack added in v2.6.27-3203-g15582d3

comment from that patch:

: pty: If the administrator creates a device for a ptmx slave we should not error
:
: The open path for ptmx slaves is via the ptmx device. Opening them any
: other way is not allowed. Vegard Nossum found that previously this was not
: the case and mknod foo c 128 42; cat foo would produce nasty diagnostics
:
: Signed-off-by: Alan Cox <alan@redhat.com>
: Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

devpts_get_tty() returns non-null only for inodes on devpts, but there is no
inodes for master-devices, /dev/ptmx (/dev/pts/ptmx) is the only way to open them.
Thus we can completely forbid lookup for master-devices and eliminate that hack in
tty_init_dev() because tty_open() will get EIO from tty_driver_lookup_tty().

Signed-off-by: Konstantin Khlebnikov <khlebnikov@openvz.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

TTY: make tty_add_file non-failing

If tty_add_file fails at the point it is now, we have to revert all
the changes we did to the tty. It means either decrease all refcounts
if this was a tty reopen or delete the tty if it was newly allocated.

There was a try to fix this in v3.0-rc2 using tty_release in 0259894c7
(TTY: fix fail path in tty_open). But instead it introduced a NULL
dereference. It's because tty_release dereferences
filp->private_data, but that one is set even in our tty_add_file. And
when tty_add_file fails, it's still NULL/garbage. Hence tty_release
cannot be called there.

To circumvent the original leak (and the current NULL deref) we split
tty_add_file into two functions, making the latter non-failing. In
that case we may do the former early in open, where handling failures
is easy. The latter stays as it is now. So there is no change in
functionality.

The original bug (leak) was introduced by f573bd176 (tty: Remove
__GFP_NOFAIL from tty_add_file()). Thanks Dan for reporting this.

Later, we may split tty_release into more functions and call only some
of them in this fail path instead. (If at all possible.)

Introduced-in: v2.6.37-rc2
Signed-off-by: Jiri Slaby <jslaby@suse.cz>
Reported-by: Dan Carpenter <dan.carpenter@oracle.com>
Cc: stable <stable@vger.kernel.org>
Cc: Alan Cox <alan@lxorguk.ukuu.org.uk>
Cc: Pekka Enberg <penberg@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

tty: Support compat_ioctl get/set termios_locked

When running a Fedora 15 (x86) on an x86_64 kernel, in the boot process
plymouthd complains about those two missing ioctls:
[ 2.581783] ioctl32(plymouthd:186): Unknown cmd fd(10) cmd(00005457){t:'T';sz:0} arg(ffb6a5d0) on /dev/tty1
[ 2.581803] ioctl32(plymouthd:186): Unknown cmd fd(10) cmd(00005456){t:'T';sz:0} arg(ffb6a680) on /dev/tty1

both ioctl functions work on the 'struct termios' resp. 'struct termios2',
which has the same size (36 bytes resp. 44 bytes) on x86 and x86_64,
so it's just a matter of converting the pointer from userland.

Signed-off-by: Thomas Meyer <thomas@m3y3r.de>
Cc: Arnd Bergmann <arnd@arndb.de>
Cc: Alan Cox <alan@lxorguk.ukuu.org.uk>
Signed-off-by: Andrew Morton <akpm@google.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

TTY: define tty_wait_until_sent_from_close

We need this helper to fix system stalls. The issue is that the rest
of the system TTYs wait for us to finish waiting. This wasn't an issue
with BKL. BKL used to unlock implicitly.

This is based on the Arnd suggestion.

Signed-off-by: Jiri Slaby <jslaby@suse.cz>
Acked-by: Arnd Bergmann <arnd@arndb.de>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

TTY: remove tty_locked

We used it really only serial and ami_serial. The rest of the
callsites were BUG/WARN_ONs to check if BTM is held. Now that we
pruned tty_locked from both of the real users, we can get rid of
tty_lock along with __big_tty_mutex_owner.

Signed-off-by: Jiri Slaby <jslaby@suse.cz>
Acked-by: Arnd Bergmann <arnd@arndb.de>
Cc: Alan Cox <alan@linux.intel.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

TTY: pty, fix pty counting

tty_operations->remove is normally called like:
queue_release_one_tty
->tty_shutdown
->tty_driver_remove_tty
->tty_operations->remove

However tty_shutdown() is called from queue_release_one_tty() only if
tty_operations->shutdown is NULL. But for pty, it is not.
pty_unix98_shutdown() is used there as ->shutdown.

So tty_operations->remove of pty (i.e. pty_unix98_remove()) is never
called. This results in invalid pty_count. I.e. what can be seen in
/proc/sys/kernel/pty/nr.

I see this was already reported at:
https://lkml.org/lkml/2009/11/5/370
But it was not fixed since then.

This patch is kind of a hackish way. The problem lies in ->install. We
allocate there another tty (so-called tty->link). So ->install is
called once, but ->remove twice, for both tty and tty->link. The fix
here is to count both tty and tty->link and divide the count by 2 for
user.

And to have ->remove called, let's make tty_driver_remove_tty() global
and call that from pty_unix98_shutdown() (tty_operations->shutdown).

While at it, let's document that when ->shutdown is defined,
tty_shutdown() is not called.

Signed-off-by: Jiri Slaby <jslaby@suse.cz>
Cc: Alan Cox <alan@linux.intel.com>
Cc: "H. Peter Anvin" <hpa@zytor.com>
Cc: stable <stable@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

TTY: export NR_LDISC and N_* line discipline numbers to user-space

Since commit (4564f9e5: consolidate line discipline number definitions)
the patch moved all line discipline number from a per-architecture termios.h
to a shared one: tty.h. However, prior to this consolidation work, the
line discipline numbers were outside of an ifdef __KERNEL__/endif block
so these numbers used to be exported to user-space.

Since such numbers are kernel ABI anyway, and tty.h is already included
for user- space header processing, just move these relevant defines
outside of the ifdef __KERNEL__/endif block in include/linux/tty.h.

CC: Maxime Bizon <mbizon@freebox.fr>
Signed-off-by: Florian Fainelli <ffainelli@freebox.fr>
Acked-by: Tilman Schmidt <tilman@imap.cc>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

n_tracerouter and n_tracesink ldisc additions.

The n_tracerouter and n_tracesink line discpline drivers use the
Linux tty line discpline framework to route trace data coming
from a tty port (say UART for example) to the trace sink line
discipline driver and to another tty port(say USB). Those
these two line discipline drivers can be used together,
independently from pti.c, they are part of the original
implementation solution of the MIPI P1149.7, compact JTAG, PTI
solution for Intel mobile platforms starting with the
Medfield platform.

Signed-off-by: J Freyensee <james_p_freyensee@linux.intel.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

TTY: introduce deinit helpers for proper ldisc shutdown

Introduce deinitialize_tty_struct which should be called after
initialize_tty_struct and before successfull tty_ldisc_setup.

It calls tty_ldisc_deinit which is opposite of tty_ldisc_init. It only
puts a reference to ldisc and assigns NULL to tty->ldisc.

It will be used to shut down ldisc when tty_release cannot be called
yet.

Signed-off-by: Jiri Slaby <jslaby@suse.cz>
Cc: Alan Cox <alan@lxorguk.ukuu.org.uk>
Cc: Julian Anastasov <ja@ssi.bg>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

tty: stop using "delayed_work" in the tty layer

Using delayed-work for tty flip buffers ends up causing us to wait for
the next tick to complete some actions. That's usually not all that
noticeable, but for certain latency-critical workloads it ends up being
totally unacceptable.

As an extreme case of this, passing a token back-and-forth over a pty
will take two ticks per iteration, so even just a thousand iterations
will take 8 seconds assuming a common 250Hz configuration.

Avoiding the whole delayed work issue brings that ping-pong test-case
down to 0.009s on my machine.

In more practical terms, this latency has been a performance problem for
things like dive computer simulators (simulating the serial interface
using the ptys) and for other environments (Alan mentions a CP/M emulator).

Reported-by: Jef Driesen <jefdriesen@telenet.be>
Acked-by: Greg KH <gregkh@suse.de>
Acked-by: Alan Cox <alan@lxorguk.ukuu.org.uk>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

tty: add a helper for setting termios data from kernel side

This basically encapsulates the small bit of locking knowledge needed. While
we are at it make sure we blow up on any more abusers and unsafe misuses of
ioctl for this kind of stuff.

We change the function to return an argument as at some point it needs to
honour the POSIX 'I asked for changes but got none of them' error reporting
corner case.

Signed-off-by: Alan Cox <alan@linux.intel.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

tty: fix build error in vt_ioctl.c if CONFIG_COMPAT is enabled

This was caused by the previous patch to remove the file pointer
from the tty ioctl handler.

Cc: Alan Cox <alan@linux.intel.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

tty: now phase out the ioctl file pointer for good

Only oddities here are a couple of drivers that bogusly called the ldisc
helpers instead of returning -ENOIOCTLCMD. Fix the bug and the rest goes
away.

Signed-off-by: Alan Cox <alan@linux.intel.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

TTY: open/hangup race fixup

Like in the "TTY: don't allow reopen when ldisc is changing" patch,
this one fixes a TTY WARNING as described in the option 1) there:
1) __tty_hangup from tty_ldisc_hangup to tty_ldisc_enable. During this
section tty_lock is held. However tty_lock is temporarily dropped in
the middle of the function by tty_ldisc_hangup.

The fix is to introduce a new flag which we set during the unlocked
window and check it in tty_reopen too. The flag is TTY_HUPPING and is
cleared after TTY_HUPPED is set.

While at it, remove duplicate TTY_HUPPED set_bit. The one after
calling ops->hangup seems to be more correct. But anyway, we hold
tty_lock, so there should be no difference.

Also document the function it does that kind of crap.

Nicely reproducible with two forked children:
static void do_work(const char *tty)
{
if (signal(SIGHUP, SIG_IGN) == SIG_ERR) exit(1);
setsid();
while (1) {
int fd = open(tty, O_RDWR|O_NOCTTY);
if (fd < 0) continue;
if (ioctl(fd, TIOCSCTTY)) continue;
if (vhangup()) continue;
close(fd);
}
exit(0);
}

Signed-off-by: Jiri Slaby <jslaby@suse.cz>
Reported-by: <Valdis.Kletnieks@vt.edu>
Reported-by: Kyle McMartin <kyle@mcmartin.ca>
Cc: Alan Cox <alan@lxorguk.ukuu.org.uk>
Cc: stable <stable@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

BKL: remove extraneous #include <smp_lock.h>

The big kernel lock has been removed from all these files at some point,
leaving only the #include.

Remove this too as a cleanup.

Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

tty: Fix formatting in tty.h

Someone added a new ldisc number and messed up the tabbing. Fix it before
anyone else copies it.

Signed-off-by: Alan Cox <alan@linux.intel.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

audit: Call tty_audit_push_task() outside preempt disabled

While auditing all tasklist_lock read_lock sites I stumbled over the
following call chain:

audit_prepare_user_tty()
read_lock(&tasklist_lock);
tty_audit_push_task();
mutex_lock(&buf->mutex);

--> buf->mutex is locked with preemption disabled.

Solve this by acquiring a reference to the task struct under
rcu_read_lock and call tty_audit_push_task outside of the preempt
disabled region.

Move all code which needs to be protected by sighand lock into
tty_audit_push_task() and use lock/unlock_sighand as we do not hold
tasklist_lock.

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Cc: Al Viro <viro@zeniv.linux.org.uk>
Cc: Eric Paris <eparis@redhat.com>
Cc: Oleg Nesterov <oleg@redhat.com>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>

tty: Remove __GFP_NOFAIL from tty_add_file()

This patch removes __GFP_NOFAIL use from tty_add_file() and adds proper error
handling to the call-sites of the function.

Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Alan Cox <alan@lxorguk.ukuu.org.uk>
Cc: Arnd Bergmann <arnd@arndb.de>
Signed-off-by: Pekka Enberg <penberg@kernel.org>
Acked-by: David Rientjes <rientjes@google.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

tty: add tty_struct->dev pointer to corresponding device instance

Some device drivers (mostly tty line disciplines) would like to have way
know a struct device instance corresponding to passed tty_struct. Add
a struct device pointer to struct tty_struct and populate it during
initialize_tty_struct().

Signed-off-by: Dmitry Eremin-Solenikov <dbaryshkov@gmail.com>
Acked-by: Alan Cox <alan@linux.intel.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

tty.h: new ldisc for TI WiLink ST

Texas Instrument's WiLink7 connectivity devices pack wireless connectivity
technologies like Bluetooth, FM Radio Receiver and Transmitter, GPS and WLAN
into a single die.
The BT, FM and GPS core on the chip are interfaced to application
processors via a single UART.

This line discipline driver allows such different technologies to be used
simultaneous and independent of each other.
Signed-off-by: Pavan Savoy <pavan_savoy@ti.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

tty: fix fu_list abuse

tty: fix fu_list abuse

tty code abuses fu_list, which causes a bug in remount,ro handling.

If a tty device node is opened on a filesystem, then the last link to the inode
removed, the filesystem will be allowed to be remounted readonly. This is
because fs_may_remount_ro does not find the 0 link tty inode on the file sb
list (because the tty code incorrectly removed it to use for its own purpose).
This can result in a filesystem with errors after it is marked "clean".

Taking idea from Christoph's initial patch, allocate a tty private struct
at file->private_data and put our required list fields in there, linking
file and tty. This makes tty nodes behave the same way as other device nodes
and avoid meddling with the vfs, and avoids this bug.

The error handling is not trivial in the tty code, so for this bugfix, I take
the simple approach of using __GFP_NOFAIL and don't worry about memory errors.
This is not a problem because our allocator doesn't fail small allocs as a rule
anyway. So proper error handling is left as an exercise for tty hackers.

[ Arguably filesystem's device inode would ideally be divorced from the
driver's pseudo inode when it is opened, but in practice it's not clear whether
that will ever be worth implementing. ]

Cc: linux-kernel@vger.kernel.org
Cc: Christoph Hellwig <hch@infradead.org>
Cc: Alan Cox <alan@lxorguk.ukuu.org.uk>
Cc: Greg Kroah-Hartman <gregkh@suse.de>
Signed-off-by: Nick Piggin <npiggin@kernel.dk>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>

fs: cleanup files_lock locking

fs: cleanup files_lock locking

Lock tty_files with a new spinlock, tty_files_lock; provide helpers to
manipulate the per-sb files list; unexport the files_lock spinlock.

Cc: linux-kernel@vger.kernel.org
Cc: Christoph Hellwig <hch@infradead.org>
Cc: Alan Cox <alan@lxorguk.ukuu.org.uk>
Acked-by: Andi Kleen <ak@linux.intel.com>
Acked-by: Greg Kroah-Hartman <gregkh@suse.de>
Signed-off-by: Nick Piggin <npiggin@kernel.dk>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>

tty: implement BTM as mutex instead of BKL

The tty locking now follows the rules for mutexes, so
we can replace the BKL usage with a new subsystem
wide mutex.

Using a regular mutex here will change the behaviour
when blocked on the BTM from spinning to sleeping,
but that should not be visible to the user.

Using the mutex also means that all the BTM is now
covered by lockdep.

Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Cc: Alan Cox <alan@lxorguk.ukuu.org.uk>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

tty: remove tty_lock_nested

This changes all remaining users of tty_lock_nested
to be non-recursive, which lets us kill this function.
As a consequence, we won't need to keep the lock count
any more, which allows more simplifications later.

Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Cc: Alan Cox <alan@lxorguk.ukuu.org.uk>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

tty: introduce wait_event_interruptible_tty

Calling wait_event_interruptible implicitly
releases the BKL when it sleeps, but we need
to do this explcitly when we have converted
it to a mutex.

Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Cc: Alan Cox <alan@lxorguk.ukuu.org.uk>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

tty: replace BKL with a new tty_lock

As a preparation for replacing the big kernel lock
in the TTY layer, wrap all the callers in new
macros tty_lock, tty_lock_nested and tty_unlock.

Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Cc: Alan Cox <alan@lxorguk.ukuu.org.uk>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

tty: Add EXTPROC support for LINEMODE

This patch is against the 2.6.34 source.

Paraphrased from the 1989 BSD patch by David Borman @ cray.com:

These are the changes needed for the kernel to support
LINEMODE in the server.

There is a new bit in the termios local flag word, EXTPROC.
When this bit is set, several aspects of the terminal driver
are disabled. Input line editing, character echo, and mapping
of signals are all disabled. This allows the telnetd to turn
off these functions when in linemode, but still keep track of
what state the user wants the terminal to be in.

New ioctl:
TIOCSIG Generate a signal to processes in the
current process group of the pty.

There is a new mode for packet driver, the TIOCPKT_IOCTL bit.
When packet mode is turned on in the pty, and the EXTPROC bit
is set, then whenever the state of the pty is changed, the
next read on the master side of the pty will have the TIOCPKT_IOCTL
bit set. This allows the process on the server side of the pty
to know when the state of the terminal has changed; it can then
issue the appropriate ioctl to retrieve the new state.

Since the original BSD patches accompanied the source code for telnet
I've left that reference here, but obviously the feature is useful for
any remote terminal protocol, including ssh.

The corresponding feature has existed in the BSD tty driver since 1989.
For historical reference, a good copy of the relevant files can be found
here:

http://anonsvn.mit.edu/viewvc/krb5/trunk/src/appl/telnet/?pathrev=17741

Signed-off-by: Howard Chu <hyc@symas.com>
Cc: Alan Cox <alan@lxorguk.ukuu.org.uk>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

Fix init ordering of /dev/console vs callers of modprobe

Make /dev/console get initialised before any initialisation routine that
invokes modprobe because if modprobe fails, it's going to want to open
/dev/console, presumably to write an error message to.

The problem with that is that if the /dev/console driver is not yet
initialised, the chardev handler will call request_module() to invoke
modprobe, which will fail, because we never compile /dev/console as a
module.

This will lead to a modprobe loop, showing the following in the kernel
log:

request_module: runaway loop modprobe char-major-5-1
request_module: runaway loop modprobe char-major-5-1
request_module: runaway loop modprobe char-major-5-1
request_module: runaway loop modprobe char-major-5-1
request_module: runaway loop modprobe char-major-5-1

This can happen, for example, when the built in md5 module can't find
the built in cryptomgr module (because the latter fails to initialise).
The md5 module comes before the call to tty_init(), presumably because
'crypto' comes before 'drivers' alphabetically.

Fix this by calling tty_init() from chrdev_init().

Signed-off-by: David Howells <dhowells@redhat.com>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

tty: n_gsm line discipline

Add an implementation of GSM 0710 MUX. The implementation currently supports

- Basic and advanced framing (as either end of the link)
- UI or UIH data frames
- Adaption layer 1-4 (1 and 2 via tty, 3 and 4 as skbuff lists)
- Modem and control messages including the correct retry process
- Flow control

and exposes the MUX channels as a set of virtual tty devices including modem
signals. This is an experimental driver.

Signed-off-by: Alan Cox <alan@linux.intel.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

serial: TTY: new ldiscs for staging

Push the max ldiscs by a few number to allow ldiscs
to exist in the staging directory and elsewhere.

Signed-off-by: Pavan Savoy <pavan_savoy@ti.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

net-caif-driver: add CAIF serial driver (ldisc)

Add CAIF Serial driver. This driver is implemented as a line discipline.

caif_serial uses the following module parameters:
ser_use_stx - specifies if STart of frame eXtension is in use.
ser_loop - sets the interface in loopback mode.

Signed-off-by: Sjur Braendeland <sjur.brandeland@stericsson.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

tty_port,usb-console: Fix usb serial console open/close regression

Commit e1108a63e10d344284011cccc06328b2cd3e5da3 ("usb_serial: Use the
shutdown() operation") breaks the ability to use a usb console
starting in 2.6.33. This was observed when using
console=ttyUSB0,115200 as a boot argument with an FTDI device. The
error is:

ftdi_sio ttyUSB0: ftdi_submit_read_urb - failed submitting read urb, error -22

The handling of the ASYNCB_INITIALIZED changed in 2.6.32 such that in
tty_port_shutdown() it always clears the flag if it is set. The fix
is to add a variable to the tty_port struct to indicate when the tty
port is a console.

CC: Alan Cox <alan@linux.intel.com>
CC: Alan Stern <stern@rowland.harvard.edu>
CC: Oliver Neukum <oliver@neukum.org>
CC: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Jason Wessel <jason.wessel@windriver.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

tty: Take a 256 byte padding into account when buffering below sub-page units

The TTY layer takes some care to ensure that only sub-page allocations
are made with interrupts disabled. It does this by setting a goal of
"TTY_BUFFER_PAGE" to allocate. Unfortunately, while TTY_BUFFER_PAGE takes the
size of tty_buffer into account, it fails to account that tty_buffer_find()
rounds the buffer size out to the next 256 byte boundary before adding on
the size of the tty_buffer.

This patch adjusts the TTY_BUFFER_PAGE calculation to take into account the
size of the tty_buffer and the padding. Once applied, tty_buffer_alloc()
should not require high-order allocations.

Signed-off-by: Mel Gorman <mel@csn.ul.ie>
Cc: stable <stable@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

ldisc n_tty: add new method n_tty_inherit_ops()

This new method can be used to init a new struct tty_ldisc_ops as the
default tty_ldisc_N_TTY struct.

Signed-off-by: Rodolfo Giometti <giometti@linux.it>
Cc: David Woodhouse <dwmw2@infradead.org>
Cc: Greg KH <greg@kroah.com>
Cc: Alan Cox <alan@lxorguk.ukuu.org.uk>
Cc: Alexander Gordeev <lasaine@lvk.cs.msu.su>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

tty: Keep the default buffering to sub-page units

We allocate during interrupts so while our buffering is normally diced up
small anyway on some hardware at speed we can pressure the VM excessively
for page pairs. We don't really need big buffers to be linear so don't try
so hard.

In order to make this work well we will tidy up excess callers to request_room,
which cannot itself enforce this break up.

Signed-off-by: Alan Cox <alan@linux.intel.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

tty.h: make tty_port_get() static inline

I get a few dozen of these warnings when using
gcc (GCC) 4.4.1 20090725 (Red Hat 4.4.1-2):

In file included from mmotm-2010-0113-1217/init/do_mounts.c:5:
mmotm-2010-0113-1217/include/linux/tty.h: In function 'tty_port_get':
mmotm-2010-0113-1217/include/linux/tty.h:469: warning: '______f' is static but declared in inline function 'tty_port_get' which is not static

so make the function static inline.

[akpm@linux-foundation.org: may as well convert tty_port_users() also]
Signed-off-by: Randy Dunlap <randy.dunlap@oracle.com>
Cc: Alan Cox <alan@lxorguk.ukuu.org.uk>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

vt: introduce and use vt_kmsg_redirect() function

The kernel offers with TIOCL_GETKMSGREDIRECT ioctl() the possibility to
redirect the kernel messages to a specific console.

However, since it's not possible to switch to the kernel message console
after a panic(), it would be nice if the kernel would print the panic
message on the current console.

This patch series adds a new interface to access the global kmsg_redirect
variable by a function to be able to use it in code where
CONFIG_VT_CONSOLE is not set (kernel/panic.c).

This patch:

Instead of using and exporting a global value kmsg_redirect, introduce a
function vt_kmsg_redirect() that both can set and return the console where
messages are printed.

Change all users of kmsg_redirect (the VT code itself and kernel/power.c)
to the new interface.

The main advantage is that vt_kmsg_redirect() can also be used when
CONFIG_VT_CONSOLE is not set.

Signed-off-by: Bernhard Walle <bernhard@bwalle.de>
Cc: Alan Cox <alan@lxorguk.ukuu.org.uk>
Cc: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

tty: push the BKL down into the handlers a bit

Start trying to untangle the remaining BKL mess

Updated to fix missing unlock_kernel noted by Dan Carpenter

Signed-off-by: Alan "I must be out of my tree" Cox <alan@linux.intel.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

tty: tty_port: Add a kref object to the tty port

Users of tty port need a way to refcount ports when hotplugging is
involved.

Signed-off-by: Alan Cox <alan@linux.intel.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

tty: tty_port: Change the buffer allocator locking

We want to be able to do this without regard for the activate/own open
method being used which causes a problem using port->mutex. Add another
mutex for now. Once everything uses port_open to do buffer allocs we can
kill it back off

Signed-off-by: Alan Cox <alan@linux.intel.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

tty_port: add "tty_port_open" helper

For the moment this just moves the USB logic over and fixes the 'what if
we open and hangup at the same time' race noticed by Oliver Neukum.

Signed-off-by: Alan Cox <alan@linux.intel.com>
Cc: Alan Stern <stern@rowland.harvard.edu>
Cc: Oliver Neukum <oliver@neukum.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

tty: handle VT specific compat ioctls in vt driver

The VT specific compat_ioctl handlers are the only ones
in common code that require the BKL. Moving them into
the vt driver lets us remove the BKL from the other handlers
and cleans up the code.

Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

serial: move port users helper

This little helper is now tty_port specific and useful generally so move it

Signed-off-by: Alan Cox <alan@linux.intel.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

serial: move delta_msr_wait into the tty_port

This is used by various drivers not just serial and can be extracted
as commonality

Signed-off-by: Alan Cox <alan@linux.intel.com>

serial: Fold closing_* fields into the tty_port ones

Remove some more serial specific use

Signed-off-by: Alan Cox <alan@linux.intel.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

tty: Add a full port_close function

Now we are extracting out methods for shutdown and the like we can add a
proper tty_port_close method that knows all the innards of the tty closing
process and hides the lot from the caller.

At some point in the future this will be paired with a similar open()
helper and the drivers can stick to hardware management.

Signed-off-by: Alan Cox <alan@linux.intel.com>
Cc: stable <stable@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>