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Subject[PATCH v2 11/12] x86/crypto: Fix RBP usage in sha512-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.

Mix things up a little bit to get rid of the RBP usage, without hurting
performance too much. Use RDI instead of RBP for the TBL pointer. That
will clobber CTX, so spill CTX onto the stack and use R12 to read it in
the outer loop. R12 is used as a non-persistent temporary variable
elsewhere, so it's safe to use.

Also remove the unused y4 variable.

Reported-by: Eric Biggers <ebiggers3@gmail.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/sha512-avx2-asm.S | 75 ++++++++++++++++++++-------------------
1 file changed, 39 insertions(+), 36 deletions(-)

diff --git a/arch/x86/crypto/sha512-avx2-asm.S b/arch/x86/crypto/sha512-avx2-asm.S
index 7f5f6c6ec72e..b16d56005162 100644
--- a/arch/x86/crypto/sha512-avx2-asm.S
+++ b/arch/x86/crypto/sha512-avx2-asm.S
@@ -69,8 +69,9 @@ XFER = YTMP0

BYTE_FLIP_MASK = %ymm9

-# 1st arg
-CTX = %rdi
+# 1st arg is %rdi, which is saved to the stack and accessed later via %r12
+CTX1 = %rdi
+CTX2 = %r12
# 2nd arg
INP = %rsi
# 3rd arg
@@ -81,7 +82,7 @@ d = %r8
e = %rdx
y3 = %rsi

-TBL = %rbp
+TBL = %rdi # clobbers CTX1

a = %rax
b = %rbx
@@ -91,26 +92,26 @@ g = %r10
h = %r11
old_h = %r11

-T1 = %r12
+T1 = %r12 # clobbers CTX2
y0 = %r13
y1 = %r14
y2 = %r15

-y4 = %r12
-
# Local variables (stack frame)
XFER_SIZE = 4*8
SRND_SIZE = 1*8
INP_SIZE = 1*8
INPEND_SIZE = 1*8
+CTX_SIZE = 1*8
RSPSAVE_SIZE = 1*8
-GPRSAVE_SIZE = 6*8
+GPRSAVE_SIZE = 5*8

frame_XFER = 0
frame_SRND = frame_XFER + XFER_SIZE
frame_INP = frame_SRND + SRND_SIZE
frame_INPEND = frame_INP + INP_SIZE
-frame_RSPSAVE = frame_INPEND + INPEND_SIZE
+frame_CTX = frame_INPEND + INPEND_SIZE
+frame_RSPSAVE = frame_CTX + CTX_SIZE
frame_GPRSAVE = frame_RSPSAVE + RSPSAVE_SIZE
frame_size = frame_GPRSAVE + GPRSAVE_SIZE

@@ -576,12 +577,11 @@ ENTRY(sha512_transform_rorx)
mov %rax, frame_RSPSAVE(%rsp)

# Save GPRs
- mov %rbp, frame_GPRSAVE(%rsp)
- mov %rbx, 8*1+frame_GPRSAVE(%rsp)
- mov %r12, 8*2+frame_GPRSAVE(%rsp)
- mov %r13, 8*3+frame_GPRSAVE(%rsp)
- mov %r14, 8*4+frame_GPRSAVE(%rsp)
- mov %r15, 8*5+frame_GPRSAVE(%rsp)
+ mov %rbx, 8*0+frame_GPRSAVE(%rsp)
+ mov %r12, 8*1+frame_GPRSAVE(%rsp)
+ mov %r13, 8*2+frame_GPRSAVE(%rsp)
+ mov %r14, 8*3+frame_GPRSAVE(%rsp)
+ mov %r15, 8*4+frame_GPRSAVE(%rsp)

shl $7, NUM_BLKS # convert to bytes
jz done_hash
@@ -589,14 +589,17 @@ ENTRY(sha512_transform_rorx)
mov NUM_BLKS, frame_INPEND(%rsp)

## load initial digest
- mov 8*0(CTX),a
- mov 8*1(CTX),b
- mov 8*2(CTX),c
- mov 8*3(CTX),d
- mov 8*4(CTX),e
- mov 8*5(CTX),f
- mov 8*6(CTX),g
- mov 8*7(CTX),h
+ mov 8*0(CTX1), a
+ mov 8*1(CTX1), b
+ mov 8*2(CTX1), c
+ mov 8*3(CTX1), d
+ mov 8*4(CTX1), e
+ mov 8*5(CTX1), f
+ mov 8*6(CTX1), g
+ mov 8*7(CTX1), h
+
+ # save %rdi (CTX) before it gets clobbered
+ mov %rdi, frame_CTX(%rsp)

vmovdqa PSHUFFLE_BYTE_FLIP_MASK(%rip), BYTE_FLIP_MASK

@@ -652,14 +655,15 @@ loop2:
subq $1, frame_SRND(%rsp)
jne loop2

- addm 8*0(CTX),a
- addm 8*1(CTX),b
- addm 8*2(CTX),c
- addm 8*3(CTX),d
- addm 8*4(CTX),e
- addm 8*5(CTX),f
- addm 8*6(CTX),g
- addm 8*7(CTX),h
+ mov frame_CTX(%rsp), CTX2
+ addm 8*0(CTX2), a
+ addm 8*1(CTX2), b
+ addm 8*2(CTX2), c
+ addm 8*3(CTX2), d
+ addm 8*4(CTX2), e
+ addm 8*5(CTX2), f
+ addm 8*6(CTX2), g
+ addm 8*7(CTX2), h

mov frame_INP(%rsp), INP
add $128, INP
@@ -669,12 +673,11 @@ loop2:
done_hash:

# Restore GPRs
- mov frame_GPRSAVE(%rsp) ,%rbp
- mov 8*1+frame_GPRSAVE(%rsp) ,%rbx
- mov 8*2+frame_GPRSAVE(%rsp) ,%r12
- mov 8*3+frame_GPRSAVE(%rsp) ,%r13
- mov 8*4+frame_GPRSAVE(%rsp) ,%r14
- mov 8*5+frame_GPRSAVE(%rsp) ,%r15
+ mov 8*0+frame_GPRSAVE(%rsp), %rbx
+ mov 8*1+frame_GPRSAVE(%rsp), %r12
+ mov 8*2+frame_GPRSAVE(%rsp), %r13
+ mov 8*3+frame_GPRSAVE(%rsp), %r14
+ mov 8*4+frame_GPRSAVE(%rsp), %r15

# Restore Stack Pointer
mov frame_RSPSAVE(%rsp), %rsp
--
2.13.5
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