crypto: x86/sha1-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 REG_D 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/sha1_ssse3_asm.S b/arch/x86/crypto/sha1_ssse3_asm.S
index a410950..6204bd5 100644 (file)
--- a/arch/x86/crypto/sha1_ssse3_asm.S
+++ b/arch/x86/crypto/sha1_ssse3_asm.S
@@ -37,7 +37,7 @@
 #define REG_A  %ecx
 #define REG_B  %esi
 #define REG_C  %edi
-#define REG_D  %ebp
+#define REG_D  %r12d
 #define REG_E  %edx
 
 #define REG_T1 %eax
@@ -74,10 +74,10 @@
        ENTRY(\name)
 
        push    %rbx
-       push    %rbp
        push    %r12
+       push    %rbp
+       mov     %rsp, %rbp
 
-       mov     %rsp, %r12
        sub     $64, %rsp               # allocate workspace
        and     $~15, %rsp              # align stack
 
@@ -99,10 +99,9 @@
        xor     %rax, %rax
        rep stosq
 
-       mov     %r12, %rsp              # deallocate workspace
-
-       pop     %r12
+       mov     %rbp, %rsp              # deallocate workspace
        pop     %rbp
+       pop     %r12
        pop     %rbx
        ret