linux.git/lib/bch.c, branch v7.1-rc4

lib/bch: fix signed shift overflow in build_mod8_tables

2026-03-28T04:19:48+00:00

Cast loop variable to unsigned int before left-shifting to avoid undefined
behavior when i >= 128 and b == 3 (i << 24 overflows signed int).

Link: https://lkml.kernel.org/r/20260318074806.16527-3-objecting@objecting.org
Signed-off-by: Josh Law 
Reviewed-by: Andrew Morton 
Cc: Ivan Djelic 
Signed-off-by: Andrew Morton

lib/bch: fix signed left-shift undefined behavior

2026-03-28T04:19:48+00:00

Patch series "lib/bch: fix undefined behavior from signed left-shifts".

Fix two instances of undefined behavior in lib/bch.c caused by
left-shifting signed integers into or past the sign bit.

While the kernel's -fno-strict-overflow flag prevents miscompilation
today, these are formally UB per C11 6.5.7p4 and trivial to fix.


This patch (of 2):

Use 1u instead of 1 to avoid undefined behavior when left-shifting into
the sign bit of a signed int.  deg() can return up to 31, and 1 << 31 is
UB per C11.

Link: https://lkml.kernel.org/r/20260318074806.16527-2-objecting@objecting.org
Signed-off-by: Josh Law 
Reviewed-by: Andrew Morton 
Cc: Ivan Djelic 
Signed-off-by: Andrew Morton

Convert 'alloc_obj' family to use the new default GFP_KERNEL argument

2026-02-22T01:09:51+00:00

This was done entirely with mindless brute force, using

    git grep -l '\

treewide: Replace kmalloc with kmalloc_obj for non-scalar types

2026-02-21T09:02:28+00:00

This is the result of running the Coccinelle script from
scripts/coccinelle/api/kmalloc_objs.cocci. The script is designed to
avoid scalar types (which need careful case-by-case checking), and
instead replace kmalloc-family calls that allocate struct or union
object instances:

Single allocations:	kmalloc(sizeof(TYPE), ...)
are replaced with:	kmalloc_obj(TYPE, ...)

Array allocations:	kmalloc_array(COUNT, sizeof(TYPE), ...)
are replaced with:	kmalloc_objs(TYPE, COUNT, ...)

Flex array allocations:	kmalloc(struct_size(PTR, FAM, COUNT), ...)
are replaced with:	kmalloc_flex(*PTR, FAM, COUNT, ...)

(where TYPE may also be *VAR)

The resulting allocations no longer return "void *", instead returning
"TYPE *".

Signed-off-by: Kees Cook

lib/bch.c: use swap() to improve code

2024-07-12T23:39:53+00:00

Use the swap() macro to simplify the functions solve_linear_system() and
gf_poly_gcd() and improve their readability.  Remove the local variable
tmp.

Fixes the following three Coccinelle/coccicheck warnings reported by
swap.cocci:

  WARNING opportunity for swap()
  WARNING opportunity for swap()
  WARNING opportunity for swap()

Link: https://lkml.kernel.org/r/20240708224023.9312-2-thorsten.blum@toblux.com
Signed-off-by: Thorsten Blum 
Signed-off-by: Andrew Morton

lib/bch.c: use bitrev instead of internal logic

2023-08-18T17:18:58+00:00

Replace internal logic with separate bitrev library.

Link: https://lkml.kernel.org/r/20230730081717.1498217-1-sanpeqf@gmail.com
Signed-off-by: John Sanpe 
Cc: Bhaskar Chowdhury 
Cc: Randy Dunlap 
Signed-off-by: Andrew Morton

lib/bch.c: fix a typo in the file bch.c

2021-05-07T02:24:12+00:00

s/buid/build/

Link: https://lkml.kernel.org/r/20210301123129.18754-1-unixbhaskar@gmail.com
Signed-off-by: Bhaskar Chowdhury 
Acked-by: Randy Dunlap 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds

lib/bch: Allow easy bit swapping

2020-05-24T18:48:11+00:00

It seems that several hardware ECC engine use a swapped representation
of bytes compared to software. This might having to do with how the
ECC engine is wired to the NAND controller or the order the bits are
passed to the hardware BCH logic.

This means that when the software BCH engine is working in conjunction
with data generated with hardware, sometimes we might need to swap the
bits inside bytes, eg:

    0x0A = b0000_1010 -> b0101_0000 = 0x50

Make it possible by adding a boolean to the BCH initialization routine.

Regarding the implementation itself, this is a rather simple approach
that can probably be enhanced in the future by preparing the
->a_{mod,pow}_tab tables with the swapping in mind.

Suggested-by: Boris Brezillon 
Signed-off-by: Miquel Raynal 
Reviewed-by: Boris Brezillon 
Link: https://lore.kernel.org/linux-mtd/20200519074549.23673-3-miquel.raynal@bootlin.com

lib/bch: Rework a little bit the exported function names

2020-05-24T18:48:11+00:00

There are four exported functions, all suffixed by _bch, which is
clearly not the norm. Let's rename them by prefixing them with bch_
instead.

This is a mechanical change:
    init_bch -> bch_init
    free_bch -> bch_free
    encode_bch -> bch_encode
    decode_bch -> bch_decode

Signed-off-by: Miquel Raynal 
Reviewed-by: Boris Brezillon 
Link: https://lore.kernel.org/linux-mtd/20200519074549.23673-2-miquel.raynal@bootlin.com

lib/bch.c: replace zero-length array with flexible-array member

2020-04-07T17:43:42+00:00

The current codebase makes use of the zero-length array language extension
to the C90 standard, but the preferred mechanism to declare
variable-length types such as these ones is a flexible array member[1][2],
introduced in C99:

struct foo {
        int stuff;
        struct boo array[];
};

By making use of the mechanism above, we will get a compiler warning in
case the flexible array does not occur last in the structure, which will
help us prevent some kind of undefined behavior bugs from being
inadvertenly introduced[3] to the codebase from now on.

This issue was found with the help of Coccinelle.

[1] https://gcc.gnu.org/onlinedocs/gcc/Zero-Length.html
[2] https://github.com/KSPP/linux/issues/21
[3] commit 76497732932f ("cxgb3/l2t: Fix undefined behaviour")

Signed-off-by: Gustavo A. R. Silva 
Signed-off-by: Andrew Morton 
Link: http://lkml.kernel.org/r/20200211205119.GA21234@embeddedor
Signed-off-by: Linus Torvalds