pstore: Add priv field to pstore_record for backend specific use

The EFI pstore backend will need to store per-record variable name data
when we switch away from the efivars layer. Add a priv field to struct
pstore_record, and document it as holding a backend specific pointer
that is assumed to be a kmalloc()d buffer, and will be kfree()d when the
entire record is freed.

Acked-by: Kees Cook <keescook@chromium.org>
Signed-off-by: Ard Biesheuvel <ardb@kernel.org>

pstore: Don't use semaphores in always-atomic-context code

pstore_dump() is *always* invoked in atomic context (nowadays in an RCU
read-side critical section, before that under a spinlock).
It doesn't make sense to try to use semaphores here.

This is mostly a revert of commit ea84b580b955 ("pstore: Convert buf_lock
to semaphore"), except that two parts aren't restored back exactly as they
were:

- keep the lock initialization in pstore_register
- in efi_pstore_write(), always set the "block" flag to false
- omit "is_locked", that was unnecessary since
commit 959217c84c27 ("pstore: Actually give up during locking failure")
- fix the bailout message

The actual problem that the buggy commit was trying to address may have
been that the use of preemptible() in efi_pstore_write() was wrong - it
only looks at preempt_count() and the state of IRQs, but __rcu_read_lock()
doesn't touch either of those under CONFIG_PREEMPT_RCU.
(Sidenote: CONFIG_PREEMPT_RCU means that the scheduler can preempt tasks in
RCU read-side critical sections, but you're not allowed to actively
block/reschedule.)

Lockdep probably never caught the problem because it's very rare that you
actually hit the contended case, so lockdep always just sees the
down_trylock(), not the down_interruptible(), and so it can't tell that
there's a problem.

Fixes: ea84b580b955 ("pstore: Convert buf_lock to semaphore")
Cc: stable@vger.kernel.org
Acked-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Signed-off-by: Jann Horn <jannh@google.com>
Signed-off-by: Kees Cook <keescook@chromium.org>
Link: https://lore.kernel.org/r/20220314185953.2068993-1-jannh@google.com

pstore/platform: Pass max_reason to kmesg dump

Add a new member to struct pstore_info for passing information about
kmesg dump maximum reason. This allows a finer control of what kmesg
dumps are sent to pstore storage backends.

Those backends that do not explicitly set this field (keeping it equal to
0), get the default behavior: store only Oopses and Panics, or everything
if the printk.always_kmsg_dump boot param is set.

Signed-off-by: Pavel Tatashin <pasha.tatashin@soleen.com>
Link: https://lore.kernel.org/lkml/20200515184434.8470-5-keescook@chromium.org/
Co-developed-by: Kees Cook <keescook@chromium.org>
Signed-off-by: Kees Cook <keescook@chromium.org>

pstore/platform: Switch pstore_info::name to const

In order to more cleanly pass around backend names, make the "name" member
const. This means the module param needs to be dynamic (technically, it
was before, so this actually cleans up a minor memory leak if a backend
was specified and then gets unloaded.)

Link: https://lore.kernel.org/lkml/20200510202436.63222-3-keescook@chromium.org/
Signed-off-by: Kees Cook <keescook@chromium.org>

treewide: Replace GPLv2 boilerplate/reference with SPDX - rule 333

Based on 1 normalized pattern(s):

this program is free software you can redistribute it and or modify
it under the terms of the gnu general public license version 2 as
published by the free software foundation this program is
distributed in the hope that it will be useful but without any
warranty without even the implied warranty of merchantability or
fitness for a particular purpose see the gnu general public license
for more details you should have received a copy of the gnu general
public license along with this program if not write to the free
software foundation inc 59 temple place suite 330 boston ma 02111
1307 usa

extracted by the scancode license scanner the SPDX license identifier

GPL-2.0-only

has been chosen to replace the boilerplate/reference in 136 file(s).

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Reviewed-by: Alexios Zavras <alexios.zavras@intel.com>
Reviewed-by: Allison Randal <allison@lohutok.net>
Cc: linux-spdx@vger.kernel.org
Link: https://lkml.kernel.org/r/20190530000436.384967451@linutronix.de
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

pstore: Convert buf_lock to semaphore

Instead of running with interrupts disabled, use a semaphore. This should
make it easier for backends that may need to sleep (e.g. EFI) when
performing a write:

|BUG: sleeping function called from invalid context at kernel/sched/completion.c:99
|in_atomic(): 1, irqs_disabled(): 1, pid: 2236, name: sig-xstate-bum
|Preemption disabled at:
|[<ffffffff99d60512>] pstore_dump+0x72/0x330
|CPU: 26 PID: 2236 Comm: sig-xstate-bum Tainted: G D 4.20.0-rc3 #45
|Call Trace:
| dump_stack+0x4f/0x6a
| ___might_sleep.cold.91+0xd3/0xe4
| __might_sleep+0x50/0x90
| wait_for_completion+0x32/0x130
| virt_efi_query_variable_info+0x14e/0x160
| efi_query_variable_store+0x51/0x1a0
| efivar_entry_set_safe+0xa3/0x1b0
| efi_pstore_write+0x109/0x140
| pstore_dump+0x11c/0x330
| kmsg_dump+0xa4/0xd0
| oops_exit+0x22/0x30
...

Reported-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Fixes: 21b3ddd39fee ("efi: Don't use spinlocks for efi vars")
Signed-off-by: Kees Cook <keescook@chromium.org>

pstore: Map PSTORE_TYPE_* to strings

In later patches we will need to map types to names, so create a
constant table for that which can also be used in different parts of
old and new code. This saves the type in the PRZ which will be useful
in later patches.

Instead of having an explicit PSTORE_TYPE_UNKNOWN, just use ..._MAX.

This includes removing the now redundant filename templates which can use
a single format string. Also, there's no reason to limit the "is it still
compressed?" test to only PSTORE_TYPE_DMESG when building the pstorefs
filename. Records are zero-initialized, so a backend would need to have
explicitly set compressed=1.

Signed-off-by: Joel Fernandes (Google) <joel@joelfernandes.org>
Co-developed-by: Kees Cook <keescook@chromium.org>
Signed-off-by: Kees Cook <keescook@chromium.org>

pstore: Replace open-coded << with BIT()

Minor clean-up to use BIT() (as already done in pstore_ram.h).

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

pstore: Improve and update some comments and status output

This improves and updates some comments:
- dump handler comment out of sync from calling convention
- fix kern-doc typo

and improves status output:
- reminder that only kernel crash dumps are compressed
- do not be silent about ECC infrastructure failures

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

pstore/ram: Correctly calculate usable PRZ bytes

The actual number of bytes stored in a PRZ is smaller than the
bytes requested by platform data, since there is a header on each
PRZ. Additionally, if ECC is enabled, there are trailing bytes used
as well. Normally this mismatch doesn't matter since PRZs are circular
buffers and the leading "overflow" bytes are just thrown away. However, in
the case of a compressed record, this rather badly corrupts the results.

This corruption was visible with "ramoops.mem_size=204800 ramoops.ecc=1".
Any stored crashes would not be uncompressable (producing a pstorefs
"dmesg-*.enc.z" file), and triggering errors at boot:

[ 2.790759] pstore: crypto_comp_decompress failed, ret = -22!

Backporting this depends on commit 70ad35db3321 ("pstore: Convert console
write to use ->write_buf")

Reported-by: Joel Fernandes <joel@joelfernandes.org>
Fixes: b0aad7a99c1d ("pstore: Add compression support to pstore")
Signed-off-by: Kees Cook <keescook@chromium.org>
Reviewed-by: Joel Fernandes (Google) <joel@joelfernandes.org>

pstore: Convert internal records to timespec64

This prepares pstore for converting the VFS layer to timespec64.

Signed-off-by: Kees Cook <keescook@chromium.org>
Signed-off-by: Deepa Dinamani <deepa.kernel@gmail.com>

pstore: Populate pstore record->time field

The current time will be initially available in the record->time field
for all pstore_read() and pstore_write() calls. Backends can either
update the field during read(), or use the field during write() instead
of fetching time themselves.

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

pstore: Remove write_buf() callback

Now that write() and write_buf() are functionally identical, this removes
write_buf(), and renames write_buf_user() to write_user(). Additionally
adds sanity-checks for pstore_info's declared functions and flags at
registration time.

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

pstore: Replace arguments for write_buf_user() API

Removes argument list in favor of pstore record, though the user buffer
remains passed separately since it must carry the __user annotation.

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

pstore: Replace arguments for write_buf() API

As with the other API updates, this removes the long argument list in favor
of passing a single pstore recaord.

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

pstore: Replace arguments for erase() API

This removes the argument list for the erase() callback and replaces it
with a pointer to the backend record details to be removed.

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

pstore: Replace arguments for write() API

Similar to the pstore_info read() callback, there were too many arguments.
This switches to the new struct pstore_record pointer instead. This adds
"reason" and "part" to the record structure as well.

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

pstore: Replace arguments for read() API

The argument list for the pstore_read() interface is unwieldy. This changes
passes the new struct pstore_record instead. The erst backend was already
doing something similar internally.

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

pstore: Extract common arguments into structure

The read/mkfile pair pass the same arguments and should be cleared
between calls. Move to a structure and wipe it after every loop.

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

pstore: Add kernel-doc for struct pstore_info

This adds documentation for struct pstore_info, which also includes
the basic API the backends need to implement.

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

pstore: Add ftrace timestamp counter

In preparation for merging the per CPU buffers into one buffer when
we retrieve the pstore ftrace data, we store the timestamp as a
counter in the ftrace pstore record. We store the CPU number as well
if !PSTORE_CPU_IN_IP, in this case we shift the counter and may lose
ordering there but we preserve the same record size. The timestamp counter
is also racy, and not doing any locking or synchronization here results
in the benefit of lower overhead. Since we don't care much here for exact
ordering of function traces across CPUs, we don't synchronize and may lose
some counter updates but I'm ok with that.

Using trace_clock() results in much lower performance so avoid using it
since we don't want accuracy in timestamp and need a rough ordering to
perform merge.

Signed-off-by: Joel Fernandes <joelaf@google.com>
[kees: updated commit message, added comments]
Signed-off-by: Kees Cook <keescook@chromium.org>

pstore/pmsg: drop bounce buffer

Removing a bounce buffer copy operation in the pmsg driver path is
always better. We also gain in overall performance by not requesting
a vmalloc on every write as this can cause precious RT tasks, such
as user facing media operation, to stall while memory is being
reclaimed. Added a write_buf_user to the pstore functions, a backup
platform write_buf_user that uses the small buffer that is part of
the instance, and implemented a ramoops write_buf_user that only
supports PSTORE_TYPE_PMSG.

Signed-off-by: Mark Salyzyn <salyzyn@android.com>
Signed-off-by: Kees Cook <keescook@chromium.org>

pstore/ram: Set pstore flags dynamically

The ramoops can be configured to enable each pstore type by setting
their size. In that case, it'd be better not to register disabled types
in the first place.

Cc: Anton Vorontsov <anton@enomsg.org>
Cc: Colin Cross <ccross@android.com>
Cc: Kees Cook <keescook@chromium.org>
Cc: Tony Luck <tony.luck@intel.com>
Signed-off-by: Namhyung Kim <namhyung@kernel.org>
Signed-off-by: Kees Cook <keescook@chromium.org>

pstore: Split pstore fragile flags

This patch adds new PSTORE_FLAGS for each pstore type so that they can
be enabled separately. This is a preparation for ongoing virtio-pstore
work to support those types flexibly.

The PSTORE_FLAGS_FRAGILE is changed to PSTORE_FLAGS_DMESG to preserve the
original behavior.

Cc: Anton Vorontsov <anton@enomsg.org>
Cc: Colin Cross <ccross@android.com>
Cc: Kees Cook <keescook@chromium.org>
Cc: Tony Luck <tony.luck@intel.com>
Cc: "Rafael J. Wysocki" <rjw@rjwysocki.net>
Cc: Len Brown <lenb@kernel.org>
Cc: Matt Fleming <matt@codeblueprint.co.uk>
Cc: linux-acpi@vger.kernel.org
Cc: linux-efi@vger.kernel.org
Signed-off-by: Namhyung Kim <namhyung@kernel.org>
[kees: retained "FRAGILE" for now to make merges easier]
Signed-off-by: Kees Cook <keescook@chromium.org>

pstore: add lzo/lz4 compression support

Like zlib compression in pstore, this patch added lzo and lz4
compression support so that users can have more options and better
compression ratio.

The original code treats the compressed data together with the
uncompressed ECC correction notice by using zlib decompress. The
ECC correction notice is missing in the decompression process. The
treatment also makes lzo and lz4 not working. So I treat them
separately by using pstore_decompress() to treat the compressed
data, and memcpy() to treat the uncompressed ECC correction notice.

Signed-off-by: Geliang Tang <geliangtang@163.com>
Signed-off-by: Kees Cook <keescook@chromium.org>

pstore: add pstore unregister

pstore doesn't support unregistering yet. It was marked as TODO.
This patch adds some code to fix it:
1) Add functions to unregister kmsg/console/ftrace/pmsg.
2) Add a function to free compression buffer.
3) Unmap the memory and free it.
4) Add a function to unregister pstore filesystem.

Signed-off-by: Geliang Tang <geliangtang@163.com>
Acked-by: Kees Cook <keescook@chromium.org>
[Removed __exit annotation from ramoops_remove(). Reported by Arnd Bergmann]
Signed-off-by: Tony Luck <tony.luck@intel.com>

pstore: Add pstore type id for PPC64 opal nvram partition

This patch adds a new PPC64 partition type to be used for opal
specific nvram partition. A new partition type is needed as none
of the existing type matches this partition type.

Signed-off-by: Hari Bathini <hbathini@linux.vnet.ibm.com>
Reviewed-by: Kees Cook <keescook@chromium.org>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>

pstore: Add pmsg - user-space accessible pstore object

A secured user-space accessible pstore object. Writes
to /dev/pmsg0 are appended to the buffer, on reboot
the persistent contents are available in
/sys/fs/pstore/pmsg-ramoops-[ID].

One possible use is syslogd, or other daemon, can
write messages, then on reboot provides a means to
triage user-space activities leading up to a panic
as a companion to the pstore dmesg or console logs.

Signed-off-by: Mark Salyzyn <salyzyn@android.com>
Acked-by: Kees Cook <keescook@chromium.org>
Signed-off-by: Tony Luck <tony.luck@intel.com>

pstore: Don't allow high traffic options on fragile devices

Some pstore backing devices use on board flash as persistent
storage. These have limited numbers of write cycles so it
is a poor idea to use them from high frequency operations.

Signed-off-by: Tony Luck <tony.luck@intel.com>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

pstore: Introduce new argument 'compressed' in the read callback

Backends will set the flag 'compressed' after reading the log from
persistent store to indicate the data being returned to pstore is
compressed or not.

Signed-off-by: Aruna Balakrishnaiah <aruna@linux.vnet.ibm.com>
Reviewed-by: Kees Cook <keescook@chromium.org>
Signed-off-by: Tony Luck <tony.luck@intel.com>

pstore: Add new argument 'compressed' in pstore write callback

Addition of new argument 'compressed' in the write call back will
help the backend to know if the data passed from pstore is compressed
or not (In case where compression fails.). If compressed, the backend
can add a tag indicating the data is compressed while writing to
persistent store.

Signed-off-by: Aruna Balakrishnaiah <aruna@linux.vnet.ibm.com>
Reviewed-by: Kees Cook <keescook@chromium.org>
Signed-off-by: Tony Luck <tony.luck@intel.com>

pstore: Pass header size in the pstore write callback

Header size is needed to distinguish between header and the dump data.
Incorporate the addition of new argument (hsize) in the pstore write
callback.

Signed-off-by: Aruna Balakrishnaiah <aruna@linux.vnet.ibm.com>
Acked-by: Kees Cook <keescook@chromium.org>
Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>

powerpc/pseries: Read common partition via pstore

This patch exploits pstore subsystem to read details of common partition
in NVRAM to a separate file in /dev/pstore. For instance, common partition
details will be stored in a file named [common-nvram-6].

Signed-off-by: Aruna Balakrishnaiah <aruna@linux.vnet.ibm.com>
Reviewed-by: Jim Keniston <jkenisto@us.ibm.com>
Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>

powerpc/pseries: Read of-config partition via pstore

This patch set exploits the pstore subsystem to read details of
of-config partition in NVRAM to a separate file in /dev/pstore.
For instance, of-config partition details will be stored in a
file named [of-nvram-5].

Signed-off-by: Aruna Balakrishnaiah <aruna@linux.vnet.ibm.com>
Reviewed-by: Jim Keniston <jkenisto@us.ibm.com>
Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>

powerpc/pseries: Read rtas partition via pstore

This patch set exploits the pstore subsystem to read details of rtas partition
in NVRAM to a separate file in /dev/pstore. For instance, rtas details will be
stored in a file named [rtas-nvram-4].

Signed-off-by: Aruna Balakrishnaiah <aruna@linux.vnet.ibm.com>
Reviewed-by: Jim Keniston <jkenisto@us.ibm.com>
Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>

pstore: Avoid deadlock in panic and emergency-restart path

[Issue]

When pstore is in panic and emergency-restart paths, it may be blocked
in those paths because it simply takes spin_lock.

This is an example scenario which pstore may hang up in a panic path:

- cpuA grabs psinfo->buf_lock
- cpuB panics and calls smp_send_stop
- smp_send_stop sends IRQ to cpuA
- after 1 second, cpuB gives up on cpuA and sends an NMI instead
- cpuA is now in an NMI handler while still holding buf_lock
- cpuB is deadlocked

This case may happen if a firmware has a bug and
cpuA is stuck talking with it more than one second.

Also, this is a similar scenario in an emergency-restart path:

- cpuA grabs psinfo->buf_lock and stucks in a firmware
- cpuB kicks emergency-restart via either sysrq-b or hangcheck timer.
And then, cpuB is deadlocked by taking psinfo->buf_lock again.

[Solution]

This patch avoids the deadlocking issues in both panic and emergency_restart
paths by introducing a function, is_non_blocking_path(), to check if a cpu
can be blocked in current path.

With this patch, pstore is not blocked even if another cpu has
taken a spin_lock, in those paths by changing from spin_lock_irqsave
to spin_trylock_irqsave.

In addition, according to a comment of emergency_restart() in kernel/sys.c,
spin_lock shouldn't be taken in an emergency_restart path to avoid
deadlock. This patch fits the comment below.

<snip>
/**
* emergency_restart - reboot the system
*
* Without shutting down any hardware or taking any locks
* reboot the system. This is called when we know we are in
* trouble so this is our best effort to reboot. This is
* safe to call in interrupt context.
*/
void emergency_restart(void)
<snip>

Signed-off-by: Seiji Aguchi <seiji.aguchi@hds.com>
Acked-by: Don Zickus <dzickus@redhat.com>
Signed-off-by: Tony Luck <tony.luck@intel.com>

efi_pstore: Add a sequence counter to a variable name

[Issue]

Currently, a variable name, which identifies each entry, consists of type, id and ctime.
But if multiple events happens in a short time, a second/third event may fail to log because
efi_pstore can't distinguish each event with current variable name.

[Solution]

A reasonable way to identify all events precisely is introducing a sequence counter to
the variable name.

The sequence counter has already supported in a pstore layer with "oopscount".
So, this patch adds it to a variable name.
Also, it is passed to read/erase callbacks of platform drivers in accordance with
the modification of the variable name.

<before applying this patch>
a variable name of first event: dump-type0-1-12345678
a variable name of second event: dump-type0-1-12345678

type:0
id:1
ctime:12345678

If multiple events happen in a short time, efi_pstore can't distinguish them because
variable names are same among them.

<after applying this patch>

it can be distinguishable by adding a sequence counter as follows.

a variable name of first event: dump-type0-1-1-12345678
a variable name of Second event: dump-type0-1-2-12345678

type:0
id:1
sequence counter: 1(first event), 2(second event)
ctime:12345678

In case of a write callback executed in pstore_console_write(), "0" is added to
an argument of the write callback because it just logs all kernel messages and
doesn't need to care about multiple events.

Signed-off-by: Seiji Aguchi <seiji.aguchi@hds.com>
Acked-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
Acked-by: Mike Waychison <mikew@google.com>
Signed-off-by: Tony Luck <tony.luck@intel.com>

efi_pstore: Add ctime to argument of erase callback

[Issue]

Currently, a variable name, which is used to identify each log entry, consists of type,
id and ctime. But an erase callback does not use ctime.

If efi_pstore supported just one log, type and id were enough.
However, in case of supporting multiple logs, it doesn't work because
it can't distinguish each entry without ctime at erasing time.

<Example>

As you can see below, efi_pstore can't differentiate first event from second one without ctime.

a variable name of first event: dump-type0-1-12345678
a variable name of second event: dump-type0-1-23456789

type:0
id:1
ctime:12345678, 23456789

[Solution]

This patch adds ctime to an argument of an erase callback.

It works across reboots because ctime of pstore means the date that the record was originally stored.
To do this, efi_pstore saves the ctime to variable name at writing time and passes it to pstore
at reading time.

Signed-off-by: Seiji Aguchi <seiji.aguchi@hds.com>
Acked-by: Mike Waychison <mikew@google.com>
Signed-off-by: Tony Luck <tony.luck@intel.com>

pstore/ftrace: Convert to its own enable/disable debugfs knob

With this patch we no longer reuse function tracer infrastructure, now
we register our own tracer back-end via a debugfs knob.

It's a bit more code, but that is the only downside. On the bright side we
have:

- Ability to make persistent_ram module removable (when needed, we can
move ftrace_ops struct into a module). Note that persistent_ram is still
not removable for other reasons, but with this patch it's just one
thing less to worry about;

- Pstore part is more isolated from the generic function tracer. We tried
it already by registering our own tracer in available_tracers, but that
way we're loosing ability to see the traces while we record them to
pstore. This solution is somewhere in the middle: we only register
"internal ftracer" back-end, but not the "front-end";

- When there is only pstore tracing enabled, the kernel will only write
to the pstore buffer, omitting function tracer buffer (which, of course,
still can be enabled via 'echo function > current_tracer').

Suggested-by: Steven Rostedt <rostedt@goodmis.org>
Signed-off-by: Anton Vorontsov <anton.vorontsov@linaro.org>

pstore: Headers should include all stuff they use

Headers should really include all the needed prototypes, types, defines
etc. to be self-contained. This is a long-standing issue, but apparently
the new tracing code unearthed it (SMP=n is also a prerequisite):

In file included from fs/pstore/internal.h:4:0,
from fs/pstore/ftrace.c:21:
include/linux/pstore.h:43:15: error: field ‘read_mutex’ has incomplete type

While at it, I also added the following:

linux/types.h -> size_t, phys_addr_t, uXX and friends
linux/spinlock.h -> spinlock_t
linux/errno.h -> Exxxx
linux/time.h -> struct timespec (struct passed by value)
struct module and rs_control forward declaration (passed via pointers).

Signed-off-by: Anton Vorontsov <anton.vorontsov@linaro.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

pstore: Add persistent function tracing

With this support kernel can save function call chain log into a
persistent ram buffer that can be decoded and dumped after reboot
through pstore filesystem. It can be used to determine what function
was last called before a reset or panic.

We store the log in a binary format and then decode it at read time.

p.s.
Mostly the code comes from trace_persistent.c driver found in the
Android git tree, written by Colin Cross <ccross@android.com>
(according to sign-off history). I reworked the driver a little bit,
and ported it to pstore.

Signed-off-by: Anton Vorontsov <anton.vorontsov@linaro.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

pstore: Introduce write_buf backend callback

For function tracing we need to stop using pstore.buf directly, since
in a tracing callback we can't use spinlocks, and thus we can't safely
use the global buffer.

With write_buf callback, backends no longer need to access pstore.buf
directly, and thus we can pass any buffers (e.g. allocated on stack).

Signed-off-by: Anton Vorontsov <anton.vorontsov@linaro.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

pstore: Add console log messages support

Pstore doesn't support logging kernel messages in run-time, it only
dumps dmesg when kernel oopses/panics. This makes pstore useless for
debugging hangs caused by HW issues or improper use of HW (e.g.
weird device inserted -> driver tried to write a reserved bits ->
SoC hanged. In that case we don't get any messages in the pstore.

Therefore, let's add a runtime logging support: PSTORE_TYPE_CONSOLE.

Signed-off-by: Anton Vorontsov <anton.vorontsov@linaro.org>
Acked-by: Kees Cook <keescook@chromium.org>
Acked-by: Colin Cross <ccross@android.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

pstore: pass reason to backend write callback

This allows a backend to filter on the dmesg reason as well as the pstore
reason. When ramoops is switched to pstore, this is needed since it has
no interest in storing non-crash dmesg details.

Drop pstore_write() as it has no users, and handling the "reason" here
has no obviously correct value.

Signed-off-by: Kees Cook <keescook@chromium.org>
Signed-off-by: Tony Luck <tony.luck@intel.com>

pstore: pass allocated memory region back to caller

The buf_lock cannot be held while populating the inodes, so make the backend
pass forward an allocated and filled buffer instead. This solves the following
backtrace. The effect is that "buf" is only ever used to notify the backends
that something was written to it, and shouldn't be used in the read path.

To replace the buf_lock during the read path, isolate the open/read/close
loop with a separate mutex to maintain serialized access to the backend.

Note that is is up to the pstore backend to cope if the (*write)() path is
called in the middle of the read path.

[ 59.691019] BUG: sleeping function called from invalid context at .../mm/slub.c:847
[ 59.691019] in_atomic(): 0, irqs_disabled(): 1, pid: 1819, name: mount
[ 59.691019] Pid: 1819, comm: mount Not tainted 3.0.8 #1
[ 59.691019] Call Trace:
[ 59.691019] [<810252d5>] __might_sleep+0xc3/0xca
[ 59.691019] [<810a26e6>] kmem_cache_alloc+0x32/0xf3
[ 59.691019] [<810b53ac>] ? __d_lookup_rcu+0x6f/0xf4
[ 59.691019] [<810b68b1>] alloc_inode+0x2a/0x64
[ 59.691019] [<810b6903>] new_inode+0x18/0x43
[ 59.691019] [<81142447>] pstore_get_inode.isra.1+0x11/0x98
[ 59.691019] [<81142623>] pstore_mkfile+0xae/0x26f
[ 59.691019] [<810a2a66>] ? kmem_cache_free+0x19/0xb1
[ 59.691019] [<8116c821>] ? ida_get_new_above+0x140/0x158
[ 59.691019] [<811708ea>] ? __init_rwsem+0x1e/0x2c
[ 59.691019] [<810b67e8>] ? inode_init_always+0x111/0x1b0
[ 59.691019] [<8102127e>] ? should_resched+0xd/0x27
[ 59.691019] [<8137977f>] ? _cond_resched+0xd/0x21
[ 59.691019] [<81142abf>] pstore_get_records+0x52/0xa7
[ 59.691019] [<8114254b>] pstore_fill_super+0x7d/0x91
[ 59.691019] [<810a7ff5>] mount_single+0x46/0x82
[ 59.691019] [<8114231a>] pstore_mount+0x15/0x17
[ 59.691019] [<811424ce>] ? pstore_get_inode.isra.1+0x98/0x98
[ 59.691019] [<810a8199>] mount_fs+0x5a/0x12d
[ 59.691019] [<810b9174>] ? alloc_vfsmnt+0xa4/0x14a
[ 59.691019] [<810b9474>] vfs_kern_mount+0x4f/0x7d
[ 59.691019] [<810b9d7e>] do_kern_mount+0x34/0xb2
[ 59.691019] [<810bb15f>] do_mount+0x5fc/0x64a
[ 59.691019] [<810912fb>] ? strndup_user+0x2e/0x3f
[ 59.691019] [<810bb3cb>] sys_mount+0x66/0x99
[ 59.691019] [<8137b537>] sysenter_do_call+0x12/0x26

Signed-off-by: Kees Cook <keescook@chromium.org>
Signed-off-by: Tony Luck <tony.luck@intel.com>

pstore: make pstore write function return normal success/fail value

Currently pstore write interface employs record id as return
value, but it is not enough because it can't tell caller if
the write operation is successful. Pass the record id back via
an argument pointer and return zero for success, non-zero for
failure.

Signed-off-by: Chen Gong <gong.chen@linux.intel.com>
Signed-off-by: Tony Luck <tony.luck@intel.com>

pstore: change mutex locking to spin_locks

pstore was using mutex locking to protect read/write access to the
backend plug-ins. This causes problems when pstore is executed in
an NMI context through panic() -> kmsg_dump().

This patch changes the mutex to a spin_lock_irqsave then also checks to
see if we are in an NMI context. If we are in an NMI and can't get the
lock, just print a message stating that and blow by the locking.

All this is probably a hack around the bigger locking problem but it
solves my current situation of trying to sleep in an NMI context.

Tested by loading the lkdtm module and executing a HARDLOCKUP which
will cause the machine to panic inside the nmi handler.

Signed-off-by: Don Zickus <dzickus@redhat.com>
Acked-by: Matthew Garrett <mjg@redhat.com>
Signed-off-by: Tony Luck <tony.luck@intel.com>

pstore: Make "part" unsigned

We'll never have a negative part, so just make this an unsigned int.

Signed-off-by: Matthew Garrett <mjg@redhat.com>
Signed-off-by: Tony Luck <tony.luck@intel.com>

pstore: Add extra context for writes and erases

EFI only provides small amounts of individual storage, and conventionally
puts metadata in the storage variable name. Rather than add a metadata
header to the (already limited) variable storage, it's easier for us to
modify pstore to pass all the information we need to construct a unique
variable name to the appropriate functions.

Signed-off-by: Matthew Garrett <mjg@redhat.com>
Signed-off-by: Tony Luck <tony.luck@intel.com>

pstore: Extend API for more flexibility in new backends

Some pstore implementations may not have a static context, so extend the
API to pass the pstore_info struct to all calls and allow for a context
pointer.

Signed-off-by: Matthew Garrett <mjg@redhat.com>
Signed-off-by: Tony Luck <tony.luck@intel.com>

pstore: fix pstore filesystem mount/remount issue

Currently after mount/remount operation on pstore filesystem,
the content on pstore will be lost. It is because current ERST
implementation doesn't support multi-user usage, which moves
internal pointer to the end after accessing it. Adding
multi-user support for pstore usage.

Signed-off-by: Chen Gong <gong.chen@linux.intel.com>
Signed-off-by: Tony Luck <tony.luck@intel.com>

pstore: fix one type of return value in pstore

the return type of function _read_ in pstore is size_t,
but in the callback function of _read_, the logic doesn't
consider it too much, which means if negative value (assuming
error here) is returned, it will be converted to positive because
of type casting. ssize_t is enough for this function.

Signed-off-by: Chen Gong <gong.chen@linux.intel.com>
Signed-off-by: Tony Luck <tony.luck@intel.com>

pstore: new filesystem interface to platform persistent storage

Some platforms have a small amount of non-volatile storage that
can be used to store information useful to diagnose the cause of
a system crash. This is the generic part of a file system interface
that presents information from the crash as a series of files in
/dev/pstore. Once the information has been seen, the underlying
storage is freed by deleting the files.

Signed-off-by: Tony Luck <tony.luck@intel.com>