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>

1 files changed, 7 insertions, 8 deletions

diff --git a/arch/x86/crypto/sha256-ssse3-asm.S b/arch/x86/crypto/sha256-ssse3-asm.S
index 39b83c93e7fd..c6c05ed2c16a 100644
--- 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