linux-kernel - [PATCH v2 05/12] x86/crypto: Fix RBP usage in des3_ede-asm

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Date:   Mon, 18 Sep 2017 14:42:04 -0500
From:   Josh Poimboeuf <jpoimboe@...hat.com>
To:     Herbert Xu <herbert@...dor.apana.org.au>,
        "David S. Miller" <davem@...emloft.net>
Cc:     x86@...nel.org, linux-kernel@...r.kernel.org,
        Tim Chen <tim.c.chen@...ux.intel.com>,
        Mathias Krause <minipli@...glemail.com>,
        Jussi Kivilinna <jussi.kivilinna@....fi>,
        Peter Zijlstra <peterz@...radead.org>,
        linux-crypto@...r.kernel.org, Eric Biggers <ebiggers@...gle.com>,
        Andy Lutomirski <luto@...nel.org>, Jiri Slaby <jslaby@...e.cz>
Subject: [PATCH v2 05/12] x86/crypto: Fix RBP usage in des3_ede-asm_64.S

Using RBP as a temporary register breaks frame pointer convention and
breaks stack traces when unwinding from an interrupt in the crypto code.

Use RSI instead of RBP for RT1.  Since RSI is also used as a the 'dst'
function argument, it needs to be saved on the stack until the argument
is needed.

Reported-by: Eric Biggers <ebiggers@...gle.com>
Reported-by: Peter Zijlstra <peterz@...radead.org>
Tested-by: Eric Biggers <ebiggers@...gle.com>
Acked-by: Eric Biggers <ebiggers@...gle.com>
Signed-off-by: Josh Poimboeuf <jpoimboe@...hat.com>
---
 arch/x86/crypto/des3_ede-asm_64.S | 15 +++++++++------
 1 file changed, 9 insertions(+), 6 deletions(-)

diff --git a/arch/x86/crypto/des3_ede-asm_64.S b/arch/x86/crypto/des3_ede-asm_64.S
index f3e91647ca27..8e49ce117494 100644
--- a/arch/x86/crypto/des3_ede-asm_64.S
+++ b/arch/x86/crypto/des3_ede-asm_64.S
@@ -64,12 +64,12 @@
 #define RW2bh %ch
 
 #define RT0 %r15
-#define RT1 %rbp
+#define RT1 %rsi
 #define RT2 %r14
 #define RT3 %rdx
 
 #define RT0d %r15d
-#define RT1d %ebp
+#define RT1d %esi
 #define RT2d %r14d
 #define RT3d %edx
 
@@ -177,13 +177,14 @@ ENTRY(des3_ede_x86_64_crypt_blk)
 	 *	%rsi: dst
 	 *	%rdx: src
 	 */
-	pushq %rbp;
 	pushq %rbx;
 	pushq %r12;
 	pushq %r13;
 	pushq %r14;
 	pushq %r15;
 
+	pushq %rsi; /* dst */
+
 	read_block(%rdx, RL0, RR0);
 	initial_permutation(RL0, RR0);
 
@@ -241,6 +242,8 @@ ENTRY(des3_ede_x86_64_crypt_blk)
 	round1(32+15, RL0, RR0, dummy2);
 
 	final_permutation(RR0, RL0);
+
+	popq %rsi /* dst */
 	write_block(%rsi, RR0, RL0);
 
 	popq %r15;
@@ -248,7 +251,6 @@ ENTRY(des3_ede_x86_64_crypt_blk)
 	popq %r13;
 	popq %r12;
 	popq %rbx;
-	popq %rbp;
 
 	ret;
 ENDPROC(des3_ede_x86_64_crypt_blk)
@@ -432,13 +434,14 @@ ENTRY(des3_ede_x86_64_crypt_blk_3way)
 	 *	%rdx: src (3 blocks)
 	 */
 
-	pushq %rbp;
 	pushq %rbx;
 	pushq %r12;
 	pushq %r13;
 	pushq %r14;
 	pushq %r15;
 
+	pushq %rsi /* dst */
+
 	/* load input */
 	movl 0 * 4(%rdx), RL0d;
 	movl 1 * 4(%rdx), RR0d;
@@ -520,6 +523,7 @@ ENTRY(des3_ede_x86_64_crypt_blk_3way)
 	bswapl RR2d;
 	bswapl RL2d;
 
+	popq %rsi /* dst */
 	movl RR0d, 0 * 4(%rsi);
 	movl RL0d, 1 * 4(%rsi);
 	movl RR1d, 2 * 4(%rsi);
@@ -532,7 +536,6 @@ ENTRY(des3_ede_x86_64_crypt_blk_3way)
 	popq %r13;
 	popq %r12;
 	popq %rbx;
-	popq %rbp;
 
 	ret;
 ENDPROC(des3_ede_x86_64_crypt_blk_3way)
-- 
2.13.5