mtdchar: add MEMREAD ioctl

User-space applications making use of MTD devices via /dev/mtd*
character devices currently have limited capabilities for reading data:

- only deprecated methods of accessing OOB layout information exist,

- there is no way to explicitly specify MTD operation mode to use; it
is auto-selected based on the MTD file mode (MTD_FILE_MODE_*) set
for the character device; in particular, this prevents using
MTD_OPS_AUTO_OOB for reads,

- all existing user-space interfaces which cause mtd_read() or
mtd_read_oob() to be called (via mtdchar_read() and
mtdchar_read_oob(), respectively) return success even when those
functions return -EUCLEAN or -EBADMSG; this renders user-space
applications using these interfaces unaware of any corrected
bitflips or uncorrectable ECC errors detected during reads.

Note that the existing MEMWRITE ioctl allows the MTD operation mode to
be explicitly set, allowing user-space applications to write page data
and OOB data without requiring them to know anything about the OOB
layout of the MTD device they are writing to (MTD_OPS_AUTO_OOB). Also,
the MEMWRITE ioctl does not mangle the return value of mtd_write_oob().

Add a new ioctl, MEMREAD, which addresses the above issues. It is
intended to be a read-side counterpart of the existing MEMWRITE ioctl.
Similarly to the latter, the read operation is performed in a loop which
processes at most mtd->erasesize bytes in each iteration. This is done
to prevent unbounded memory allocations caused by calling kmalloc() with
the 'size' argument taken directly from the struct mtd_read_req provided
by user space. However, the new ioctl is implemented so that the values
it returns match those that would have been returned if just a single
mtd_read_oob() call was issued to handle the entire read operation in
one go.

Note that while just returning -EUCLEAN or -EBADMSG to user space would
already be a valid and useful indication of the ECC algorithm detecting
errors during a read operation, that signal would not be granular enough
to cover all use cases. For example, knowing the maximum number of
bitflips detected in a single ECC step during a read operation performed
on a given page may be useful when dealing with an MTD partition whose
ECC layout varies across pages (e.g. a partition consisting of a
bootloader area using a "custom" ECC layout followed by data pages using
a "standard" ECC layout). To address that, include ECC statistics in
the structure returned to user space by the new MEMREAD ioctl.

Link: https://www.infradead.org/pipermail/linux-mtd/2016-April/067085.html

Suggested-by: Boris Brezillon <boris.brezillon@collabora.com>
Signed-off-by: Michał Kępień <kernel@kempniu.pl>
Acked-by: Richard Weinberger <richard@nod.at>
Signed-off-by: Miquel Raynal <miquel.raynal@bootlin.com>
Link: https://lore.kernel.org/linux-mtd/20220629125737.14418-5-kernel@kempniu.pl

mtdchar: prevent integer overflow in a safety check

Commit 6420ac0af95d ("mtdchar: prevent unbounded allocation in MEMWRITE
ioctl") added a safety check to mtdchar_write_ioctl() which attempts to
ensure that the write request sent by user space does not extend beyond
the MTD device's size. However, that check contains an addition of two
struct mtd_write_req fields, 'start' and 'len', both of which are u64
variables. The result of that addition can overflow, allowing the
safety check to be bypassed.

The arguably simplest fix - changing the data types of the relevant
struct mtd_write_req fields - is not feasible as it would break user
space.

Fix by making mtdchar_write_ioctl() truncate the value provided by user
space in the 'len' field of struct mtd_write_req, so that only the lower
32 bits of that field are used, preventing the overflow.

While the 'ooblen' field of struct mtd_write_req is not currently used
in any similarly flawed safety check, also truncate it to 32 bits, for
consistency with the 'len' field and with other MTD routines handling
OOB data.

Update include/uapi/mtd/mtd-abi.h accordingly.

Suggested-by: Richard Weinberger <richard@nod.at>
Signed-off-by: Michał Kępień <kernel@kempniu.pl>
Signed-off-by: Miquel Raynal <miquel.raynal@bootlin.com>
Link: https://lore.kernel.org/linux-mtd/20220516070601.11428-2-kernel@kempniu.pl

mtd: add OTP (one-time-programmable) erase ioctl

This may sound like a contradiction but some SPI-NOR flashes really
support erasing their OTP region until it is finally locked. Having the
possibility to erase an OTP region might come in handy during
development.

The ioctl argument follows the OTPLOCK style.

Signed-off-by: Michael Walle <michael@walle.cc>
Acked-by: Vignesh Raghavendra <vigneshr@ti.com>
Signed-off-by: Miquel Raynal <miquel.raynal@bootlin.com>
Link: https://lore.kernel.org/linux-mtd/20210303201819.2752-1-michael@walle.cc

MTD: mtd-abi.h: drop a duplicated word

Drop the repeated word "mode" in a comment.

Signed-off-by: Randy Dunlap <rdunlap@infradead.org>
Cc: Miquel Raynal <miquel.raynal@bootlin.com>
Cc: Richard Weinberger <richard@nod.at>
Cc: Vignesh Raghavendra <vigneshr@ti.com>
Cc: linux-mtd@lists.infradead.org
Signed-off-by: Richard Weinberger <richard@nod.at>

mtd: Add support for emulated SLC mode on MLC NANDs

MLC NANDs can be made a bit more reliable if we only program the lower
page of each pair. At least, this solves the paired-pages corruption
issue.

Signed-off-by: Boris Brezillon <bbrezillon@kernel.org>
Signed-off-by: Miquel Raynal <miquel.raynal@bootlin.com>
Link: https://lore.kernel.org/linux-mtd/20200503155341.16712-5-miquel.raynal@bootlin.com

mtd: abi: do not use C++ style comments in uapi header

Linux kernel tolerates C++ style comments these days. Actually, the
SPDX License tags for .c files start with //.

On the other hand, uapi headers are written in more strict C, where
the C++ comment style is forbidden.

Signed-off-by: Masahiro Yamada <yamada.masahiro@socionext.com>
Acked-by: Richard Weinberger <richard@nod.at>
Signed-off-by: Richard Weinberger <richard@nod.at>

License cleanup: add SPDX license identifier to uapi header files with a license

Many user space API headers have licensing information, which is either
incomplete, badly formatted or just a shorthand for referring to the
license under which the file is supposed to be. This makes it hard for
compliance tools to determine the correct license.

Update these files with an SPDX license identifier. The identifier was
chosen based on the license information in the file.

GPL/LGPL licensed headers get the matching GPL/LGPL SPDX license
identifier with the added 'WITH Linux-syscall-note' exception, which is
the officially assigned exception identifier for the kernel syscall
exception:

NOTE! This copyright does *not* cover user programs that use kernel
services by normal system calls - this is merely considered normal use
of the kernel, and does *not* fall under the heading of "derived work".

This exception makes it possible to include GPL headers into non GPL
code, without confusing license compliance tools.

Headers which have either explicit dual licensing or are just licensed
under a non GPL license are updated with the corresponding SPDX
identifier and the GPLv2 with syscall exception identifier. The format
is:
((GPL-2.0 WITH Linux-syscall-note) OR SPDX-ID-OF-OTHER-LICENSE)

SPDX license identifiers are a legally binding shorthand, which can be
used instead of the full boiler plate text. The update does not remove
existing license information as this has to be done on a case by case
basis and the copyright holders might have to be consulted. This will
happen in a separate step.

This patch is based on work done by Thomas Gleixner and Kate Stewart and
Philippe Ombredanne. See the previous patch in this series for the
methodology of how this patch was researched.

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>

mtd: kill the nand_ecclayout struct

Now that all MTD drivers have moved to the mtd_ooblayout_ops model we can
safely remove the struct nand_ecclayout definition, and all the remaining
places where it was still used.

Signed-off-by: Boris Brezillon <boris.brezillon@free-electrons.com>

mtd: lpddr: add driver for LPDDR2-NVM PCM memories

Signed-off-by: Vincenzo Aliberti <vincenzo.aliberti@gmail.com>
Signed-off-by: Brian Norris <computersforpeace@gmail.com>

mtd: mtd-abi: add a helper to detect the nand type

The helper is for user applications, and it is just a copy of
the kernel helper: mtd_type_is_nand();

Signed-off-by: Huang Shijie <b32955@freescale.com>
Signed-off-by: Brian Norris <computersforpeace@gmail.com>

mtd: nand: add more comment for MTD_NANDFLASH/MTD_MLCNANDFLASH

In current code, the MTD_NANDFLASH is used to represent both the SLC and
MLC. It is confusing to us.

By adding an explicit comment about these two macros, this patch makes it
clear that:
MTD_NANDFLASH : stands for SLC NAND,
MTD_MLCNANDFLASH : stands for MLC NAND (including TLC).

Signed-off-by: Huang Shijie <b32955@freescale.com>
Signed-off-by: Brian Norris <computersforpeace@gmail.com>

UAPI: (Scripted) Disintegrate include/mtd

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>