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Subject[PATCH v2 09/12] x86/crypto: Fix RBP usage in sha256-avx2-asm.S
Date
Using RBP as a temporary register breaks frame pointer convention and
breaks stack traces when unwinding from an interrupt in the crypto code.

There's no need to use RBP as a temporary register for the TBL value,
because it always stores the same value: the address of the K256 table.
Instead just reference the address of K256 directly.

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>
---
arch/x86/crypto/sha256-avx2-asm.S | 22 +++++++---------------
1 file changed, 7 insertions(+), 15 deletions(-)

diff --git a/arch/x86/crypto/sha256-avx2-asm.S b/arch/x86/crypto/sha256-avx2-asm.S
index 89c8f09787d2..1420db15dcdd 100644
--- a/arch/x86/crypto/sha256-avx2-asm.S
+++ b/arch/x86/crypto/sha256-avx2-asm.S
@@ -98,8 +98,6 @@ d = %r8d
e = %edx # clobbers NUM_BLKS
y3 = %esi # clobbers INP

-
-TBL = %rbp
SRND = CTX # SRND is same register as CTX

a = %eax
@@ -531,7 +529,6 @@ STACK_SIZE = _RSP + _RSP_SIZE
ENTRY(sha256_transform_rorx)
.align 32
pushq %rbx
- pushq %rbp
pushq %r12
pushq %r13
pushq %r14
@@ -568,8 +565,6 @@ ENTRY(sha256_transform_rorx)
mov CTX, _CTX(%rsp)

loop0:
- lea K256(%rip), TBL
-
## Load first 16 dwords from two blocks
VMOVDQ 0*32(INP),XTMP0
VMOVDQ 1*32(INP),XTMP1
@@ -597,19 +592,19 @@ last_block_enter:

.align 16
loop1:
- vpaddd 0*32(TBL, SRND), X0, XFER
+ vpaddd K256+0*32(SRND), X0, XFER
vmovdqa XFER, 0*32+_XFER(%rsp, SRND)
FOUR_ROUNDS_AND_SCHED _XFER + 0*32

- vpaddd 1*32(TBL, SRND), X0, XFER
+ vpaddd K256+1*32(SRND), X0, XFER
vmovdqa XFER, 1*32+_XFER(%rsp, SRND)
FOUR_ROUNDS_AND_SCHED _XFER + 1*32

- vpaddd 2*32(TBL, SRND), X0, XFER
+ vpaddd K256+2*32(SRND), X0, XFER
vmovdqa XFER, 2*32+_XFER(%rsp, SRND)
FOUR_ROUNDS_AND_SCHED _XFER + 2*32

- vpaddd 3*32(TBL, SRND), X0, XFER
+ vpaddd K256+3*32(SRND), X0, XFER
vmovdqa XFER, 3*32+_XFER(%rsp, SRND)
FOUR_ROUNDS_AND_SCHED _XFER + 3*32

@@ -619,10 +614,11 @@ loop1:

loop2:
## Do last 16 rounds with no scheduling
- vpaddd 0*32(TBL, SRND), X0, XFER
+ vpaddd K256+0*32(SRND), X0, XFER
vmovdqa XFER, 0*32+_XFER(%rsp, SRND)
DO_4ROUNDS _XFER + 0*32
- vpaddd 1*32(TBL, SRND), X1, XFER
+
+ vpaddd K256+1*32(SRND), X1, XFER
vmovdqa XFER, 1*32+_XFER(%rsp, SRND)
DO_4ROUNDS _XFER + 1*32
add $2*32, SRND
@@ -676,9 +672,6 @@ loop3:
ja done_hash

do_last_block:
- #### do last block
- lea K256(%rip), TBL
-
VMOVDQ 0*16(INP),XWORD0
VMOVDQ 1*16(INP),XWORD1
VMOVDQ 2*16(INP),XWORD2
@@ -718,7 +711,6 @@ done_hash:
popq %r14
popq %r13
popq %r12
- popq %rbp
popq %rbx
ret
ENDPROC(sha256_transform_rorx)
--
2.13.5
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