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| author | Lasse Collin <lasse.collin@tukaani.org> | 2024-07-21 16:36:25 +0300 |
|---|---|---|
| committer | Andrew Morton <akpm@linux-foundation.org> | 2024-09-01 20:43:26 -0700 |
| commit | bdfc0411717d52b9d2f00e48c452a61389814693 (patch) | |
| tree | d3d470310e116ea6798d11bc552958b796c70f69 /lib | |
| parent | 2ee96abef214550d9e92f5143ee3ac1fd1323e67 (diff) | |
| download | linux-bdfc0411717d52b9d2f00e48c452a61389814693.tar.gz linux-bdfc0411717d52b9d2f00e48c452a61389814693.tar.bz2 linux-bdfc0411717d52b9d2f00e48c452a61389814693.zip | |
xz: optimize for-loop conditions in the BCJ decoders
Compilers cannot optimize the addition "i + 4" away since theoretically it
could overflow.
Link: https://lkml.kernel.org/r/20240721133633.47721-11-lasse.collin@tukaani.org
Signed-off-by: Lasse Collin <lasse.collin@tukaani.org>
Reviewed-by: Sam James <sam@gentoo.org>
Cc: Albert Ou <aou@eecs.berkeley.edu>
Cc: Catalin Marinas <catalin.marinas@arm.com>
Cc: Emil Renner Berthing <emil.renner.berthing@canonical.com>
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Cc: Herbert Xu <herbert@gondor.apana.org.au>
Cc: Joel Stanley <joel@jms.id.au>
Cc: Jonathan Corbet <corbet@lwn.net>
Cc: Jubin Zhong <zhongjubin@huawei.com>
Cc: Jules Maselbas <jmaselbas@zdiv.net>
Cc: Krzysztof Kozlowski <krzk@kernel.org>
Cc: Michael Ellerman <mpe@ellerman.id.au>
Cc: Palmer Dabbelt <palmer@dabbelt.com>
Cc: Paul Walmsley <paul.walmsley@sifive.com>
Cc: Randy Dunlap <rdunlap@infradead.org>
Cc: Rui Li <me@lirui.org>
Cc: Simon Glass <sjg@chromium.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Will Deacon <will@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Diffstat (limited to 'lib')
| -rw-r--r-- | lib/xz/xz_dec_bcj.c | 23 |
1 files changed, 18 insertions, 5 deletions
diff --git a/lib/xz/xz_dec_bcj.c b/lib/xz/xz_dec_bcj.c index ab9237ed6db8..e0b4bf4999c0 100644 --- a/lib/xz/xz_dec_bcj.c +++ b/lib/xz/xz_dec_bcj.c @@ -161,7 +161,9 @@ static size_t bcj_powerpc(struct xz_dec_bcj *s, uint8_t *buf, size_t size) size_t i; uint32_t instr; - for (i = 0; i + 4 <= size; i += 4) { + size &= ~(size_t)3; + + for (i = 0; i < size; i += 4) { instr = get_unaligned_be32(buf + i); if ((instr & 0xFC000003) == 0x48000001) { instr &= 0x03FFFFFC; @@ -218,7 +220,9 @@ static size_t bcj_ia64(struct xz_dec_bcj *s, uint8_t *buf, size_t size) /* Instruction normalized with bit_res for easier manipulation */ uint64_t norm; - for (i = 0; i + 16 <= size; i += 16) { + size &= ~(size_t)15; + + for (i = 0; i < size; i += 16) { mask = branch_table[buf[i] & 0x1F]; for (slot = 0, bit_pos = 5; slot < 3; ++slot, bit_pos += 41) { if (((mask >> slot) & 1) == 0) @@ -266,7 +270,9 @@ static size_t bcj_arm(struct xz_dec_bcj *s, uint8_t *buf, size_t size) size_t i; uint32_t addr; - for (i = 0; i + 4 <= size; i += 4) { + size &= ~(size_t)3; + + for (i = 0; i < size; i += 4) { if (buf[i + 3] == 0xEB) { addr = (uint32_t)buf[i] | ((uint32_t)buf[i + 1] << 8) | ((uint32_t)buf[i + 2] << 16); @@ -289,7 +295,12 @@ static size_t bcj_armthumb(struct xz_dec_bcj *s, uint8_t *buf, size_t size) size_t i; uint32_t addr; - for (i = 0; i + 4 <= size; i += 2) { + if (size < 4) + return 0; + + size -= 4; + + for (i = 0; i <= size; i += 2) { if ((buf[i + 1] & 0xF8) == 0xF0 && (buf[i + 3] & 0xF8) == 0xF8) { addr = (((uint32_t)buf[i + 1] & 0x07) << 19) @@ -317,7 +328,9 @@ static size_t bcj_sparc(struct xz_dec_bcj *s, uint8_t *buf, size_t size) size_t i; uint32_t instr; - for (i = 0; i + 4 <= size; i += 4) { + size &= ~(size_t)3; + + for (i = 0; i < size; i += 4) { instr = get_unaligned_be32(buf + i); if ((instr >> 22) == 0x100 || (instr >> 22) == 0x1FF) { instr <<= 2; |