linux-kernel - [PATCH 05/13] x86/crypto/camellia-aesni-avx2: Unconditionally allocate stack buffer

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Date:   Wed, 24 Feb 2021 10:29:18 -0600
From:   Josh Poimboeuf <jpoimboe@...hat.com>
To:     x86@...nel.org, Herbert Xu <herbert@...dor.apana.org.au>
Cc:     linux-kernel@...r.kernel.org, Miroslav Benes <mbenes@...e.cz>,
        Peter Zijlstra <peterz@...radead.org>,
        Eric Biggers <ebiggers@...gle.com>,
        Ard Biesheuvel <ardb@...nel.org>,
        Sami Tolvanen <samitolvanen@...gle.com>,
        linux-crypto@...r.kernel.org,
        "David S . Miller" <davem@...emloft.net>
Subject: [PATCH 05/13] x86/crypto/camellia-aesni-avx2: Unconditionally allocate stack buffer

A conditional stack allocation violates traditional unwinding
requirements when a single instruction can have differing stack layouts.

There's no benefit in allocating the stack buffer conditionally.  Just
do it unconditionally.

Signed-off-by: Josh Poimboeuf <jpoimboe@...hat.com>
---
 arch/x86/crypto/camellia-aesni-avx2-asm_64.S | 5 ++---
 1 file changed, 2 insertions(+), 3 deletions(-)

diff --git a/arch/x86/crypto/camellia-aesni-avx2-asm_64.S b/arch/x86/crypto/camellia-aesni-avx2-asm_64.S
index 782e9712a1ec..706f70829a07 100644
--- a/arch/x86/crypto/camellia-aesni-avx2-asm_64.S
+++ b/arch/x86/crypto/camellia-aesni-avx2-asm_64.S
@@ -990,6 +990,7 @@ SYM_FUNC_START(camellia_cbc_dec_32way)
 	 *	%rdx: src (32 blocks)
 	 */
 	FRAME_BEGIN
+	subq $(16 * 32), %rsp;
 
 	vzeroupper;
 
@@ -1002,7 +1003,6 @@ SYM_FUNC_START(camellia_cbc_dec_32way)
 		     %ymm8, %ymm9, %ymm10, %ymm11, %ymm12, %ymm13, %ymm14,
 		     %ymm15, %rdx, (key_table)(CTX, %r8, 8));
 
-	movq %rsp, %r10;
 	cmpq %rsi, %rdx;
 	je .Lcbc_dec_use_stack;
 
@@ -1015,7 +1015,6 @@ SYM_FUNC_START(camellia_cbc_dec_32way)
 	 * dst still in-use (because dst == src), so use stack for temporary
 	 * storage.
 	 */
-	subq $(16 * 32), %rsp;
 	movq %rsp, %rax;
 
 .Lcbc_dec_continue:
@@ -1025,7 +1024,6 @@ SYM_FUNC_START(camellia_cbc_dec_32way)
 	vpxor %ymm7, %ymm7, %ymm7;
 	vinserti128 $1, (%rdx), %ymm7, %ymm7;
 	vpxor (%rax), %ymm7, %ymm7;
-	movq %r10, %rsp;
 	vpxor (0 * 32 + 16)(%rdx), %ymm6, %ymm6;
 	vpxor (1 * 32 + 16)(%rdx), %ymm5, %ymm5;
 	vpxor (2 * 32 + 16)(%rdx), %ymm4, %ymm4;
@@ -1047,6 +1045,7 @@ SYM_FUNC_START(camellia_cbc_dec_32way)
 
 	vzeroupper;
 
+	addq $(16 * 32), %rsp;
 	FRAME_END
 	ret;
 SYM_FUNC_END(camellia_cbc_dec_32way)
-- 
2.29.2