crypto: x86/sha256-ssse3 - Fix RBP usage

Using RBP as a temporary register breaks frame pointer convention and
breaks stack traces when unwinding from an interrupt in the crypto code.

Swap the usages of R12 and RBP.  Use R12 for the TBL register, and use
RBP to store the pre-aligned stack pointer.

Reported-by: Eric Biggers <ebiggers@google.com>
Reported-by: Peter Zijlstra <peterz@infradead.org>
Tested-by: Eric Biggers <ebiggers@google.com>
Acked-by: Eric Biggers <ebiggers@google.com>
Signed-off-by: Josh Poimboeuf <jpoimboe@redhat.com>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>

diff --git a/arch/x86/crypto/sha256-ssse3-asm.S b/arch/x86/crypto/sha256-ssse3-asm.S
index 39b83c9..c6c05ed 100644 (file)
--- a/arch/x86/crypto/sha256-ssse3-asm.S
+++ b/arch/x86/crypto/sha256-ssse3-asm.S
@@ -95,7 +95,7 @@ SRND = %rsi       # clobbers INP
 c = %ecx
 d = %r8d
 e = %edx
-TBL = %rbp
+TBL = %r12
 a = %eax
 b = %ebx
 
@@ -356,13 +356,13 @@ a = TMP_
 ENTRY(sha256_transform_ssse3)
 .align 32
        pushq   %rbx
-       pushq   %rbp
+       pushq   %r12
        pushq   %r13
        pushq   %r14
        pushq   %r15
-       pushq   %r12
+       pushq   %rbp
+       mov     %rsp, %rbp
 
-       mov     %rsp, %r12
        subq    $STACK_SIZE, %rsp
        and     $~15, %rsp
 
@@ -462,13 +462,12 @@ loop2:
 
 done_hash:
 
-       mov     %r12, %rsp
-
-       popq    %r12
+       mov     %rbp, %rsp
+       popq    %rbp
        popq    %r15
        popq    %r14
        popq    %r13
-       popq    %rbp
+       popq    %r12
        popq    %rbx
 
        ret