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crypto: sha1-mb - make sha1_x8_avx2() conform to C function ABI

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Megha Dey reported a kernel panic in crypto code.  The problem is that
sha1_x8_avx2() clobbers registers r12-r15 without saving and restoring
them.

Before commit aec4d0e301 ("x86/asm/crypto: Simplify stack usage in
sha-mb functions"), those registers were saved and restored by the
callers of the function.  I removed them with that commit because I
didn't realize sha1_x8_avx2() clobbered them.

Fix the potential undefined behavior associated with clobbering the
registers and make the behavior less surprising by changing the
registers to be callee saved/restored to conform with the C function
call ABI.

Also, rdx (aka RSP_SAVE) doesn't need to be saved: I verified that none
of the callers rely on it being saved, and it's not a callee-saved
register in the C ABI.

Fixes: aec4d0e301 ("x86/asm/crypto: Simplify stack usage in sha-mb functions")
Cc: stable@vger.kernel.org # 4.6
Reported-by: Megha Dey <megha.dey@linux.intel.com>
Signed-off-by: Josh Poimboeuf <jpoimboe@redhat.com>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>
This commit is contained in:
Josh Poimboeuf 2016-05-16 15:16:18 -05:00 committed by Herbert Xu
parent 256b1cfb9a
commit 4a6b27b79d
1 changed files with 11 additions and 2 deletions
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13
arch/x86/crypto/sha-mb/sha1_x8_avx2.S
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@ -296,7 +296,11 @@ W14 = TMP_
#
ENTRY(sha1_x8_avx2)
push RSP_SAVE
# save callee-saved clobbered registers to comply with C function ABI
push %r12
push %r13
push %r14
push %r15
#save rsp
mov %rsp, RSP_SAVE
@ -446,7 +450,12 @@ lloop:
## Postamble
mov RSP_SAVE, %rsp
pop RSP_SAVE
# restore callee-saved clobbered registers
pop %r15
pop %r14
pop %r13
pop %r12
ret
ENDPROC(sha1_x8_avx2)