runtime: avoid clobbering C callee-save register in cgoSigtramp

Use R11 (a caller-saved temp register) instead of RBX (a callee-saved register). I believe this only affects linux/amd64, since it is the only platform with a non-trivial cgoSigtramp implementation. Updates #18328. Change-Id: I3d35c4512624184d5a8ece653fa09ddf50e079a2 Reviewed-on: https://go-review.googlesource.com/35068 Reviewed-by: Ian Lance Taylor <[email protected]> Run-TryBot: Ian Lance Taylor <[email protected]> TryBot-Result: Gobot Gobot <[email protected]>
golang · Jan 12, 2017 · fdde7ba · fdde7ba
1 parent f65abf6
commit fdde7ba
Showing 1 changed file with 2 additions and 2 deletions.
diff --git a/src/runtime/sys_linux_amd64.s b/src/runtime/sys_linux_amd64.s
@@ -330,9 +330,9 @@ sigtrampnog:
 	// Lock sigprofCallersUse.
 	MOVL	$0, AX
 	MOVL	$1, CX
-	MOVQ	$runtime·sigprofCallersUse(SB), BX
+	MOVQ	$runtime·sigprofCallersUse(SB), R11
 	LOCK
-	CMPXCHGL	CX, 0(BX)
+	CMPXCHGL	CX, 0(R11)
 	JNZ	sigtramp  // Skip stack trace if already locked.
 
 	// Jump to the traceback function in runtime/cgo.