runtime: preserve callee-saved C registers in sigtramp

This fixes Linux and the *BSD platforms on 386/amd64.

A few OS/arch combinations were already saving registers and/or doing
something that doesn't clearly resemble the SysV C ABI; those have
been left alone.

Fixes #18328.

Change-Id: I6398f6c71020de108fc8b26ca5946f0ba0258667
Reviewed-on: https://go-review.googlesource.com/34501
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Ian Lance Taylor <iant@golang.org>

9 files changed, 156 insertions, 27 deletions

diff --git a/misc/cgo/testsanitizers/tsan9.go b/misc/cgo/testsanitizers/tsan9.go
index 7cd0ac7dd6..f166d8b495 100644
--- a/misc/cgo/testsanitizers/tsan9.go
+++ b/misc/cgo/testsanitizers/tsan9.go
@@ -6,7 +6,8 @@ package main
 
 // This program failed when run under the C/C++ ThreadSanitizer. The
 // TSAN library was not keeping track of whether signals should be
-// delivered on the alternate signal stack.
+// delivered on the alternate signal stack, and the Go signal handler
+// was not preserving callee-saved registers from C callers.
 
 /*
 #cgo CFLAGS: -g -fsanitize=thread
@@ -19,10 +20,14 @@ void spin() {
 	size_t n;
 	struct timeval tvstart, tvnow;
 	int diff;
+	void *prev = NULL, *cur;
 
 	gettimeofday(&tvstart, NULL);
 	for (n = 0; n < 1<<20; n++) {
-		free(malloc(n));
+		cur = malloc(n);
+		free(prev);
+		prev = cur;
+
 		gettimeofday(&tvnow, NULL);
 		diff = (tvnow.tv_sec - tvstart.tv_sec) * 1000 * 1000 + (tvnow.tv_usec - tvstart.tv_usec);
 
@@ -32,6 +37,8 @@ void spin() {
 			break;
 		}
 	}
+
+	free(prev);
 }
 */
 import "C"
diff --git a/src/runtime/sys_dragonfly_amd64.s b/src/runtime/sys_dragonfly_amd64.s
index 88c7f9dd8a..b950b69fe0 100644
--- a/src/runtime/sys_dragonfly_amd64.s
+++ b/src/runtime/sys_dragonfly_amd64.s
@@ -200,11 +200,28 @@ TEXT runtime·sigfwd(SB),NOSPLIT,$0-32
 	POPQ	BP
 	RET
 
-TEXT runtime·sigtramp(SB),NOSPLIT,$24
-	MOVQ	DI, 0(SP)
-	MOVQ	SI, 8(SP)
-	MOVQ	DX, 16(SP)
+TEXT runtime·sigtramp(SB),NOSPLIT,$72
+	// Save callee-saved C registers, since the caller may be a C signal handler.
+	MOVQ	BX,  bx-8(SP)
+	MOVQ	BP,  bp-16(SP)  // save in case GOEXPERIMENT=noframepointer is set
+	MOVQ	R12, r12-24(SP)
+	MOVQ	R13, r13-32(SP)
+	MOVQ	R14, r14-40(SP)
+	MOVQ	R15, r15-48(SP)
+	// We don't save mxcsr or the x87 control word because sigtrampgo doesn't
+	// modify them.
+
+	MOVQ	DX, ctx-56(SP)
+	MOVQ	SI, info-64(SP)
+	MOVQ	DI, signum-72(SP)
 	CALL	runtime·sigtrampgo(SB)
+
+	MOVQ	r15-48(SP), R15
+	MOVQ	r14-40(SP), R14
+	MOVQ	r13-32(SP), R13
+	MOVQ	r12-24(SP), R12
+	MOVQ	bp-16(SP),  BP
+	MOVQ	bx-8(SP),   BX
 	RET
 
 TEXT runtime·mmap(SB),NOSPLIT,$0
diff --git a/src/runtime/sys_freebsd_amd64.s b/src/runtime/sys_freebsd_amd64.s
index 19007dc401..158a60dec2 100644
--- a/src/runtime/sys_freebsd_amd64.s
+++ b/src/runtime/sys_freebsd_amd64.s
@@ -196,11 +196,28 @@ TEXT runtime·sigfwd(SB),NOSPLIT,$0-32
 	POPQ	BP
 	RET
 
-TEXT runtime·sigtramp(SB),NOSPLIT,$24
-	MOVQ	DI, 0(SP)
-	MOVQ	SI, 8(SP)
-	MOVQ	DX, 16(SP)
+TEXT runtime·sigtramp(SB),NOSPLIT,$72
+	// Save callee-saved C registers, since the caller may be a C signal handler.
+	MOVQ	BX, bx-8(SP)
+	MOVQ	BP, bp-16(SP)  // save in case GOEXPERIMENT=noframepointer is set
+	MOVQ	R12, r12-24(SP)
+	MOVQ	R13, r13-32(SP)
+	MOVQ	R14, r14-40(SP)
+	MOVQ	R15, r15-48(SP)
+	// We don't save mxcsr or the x87 control word because sigtrampgo doesn't
+	// modify them.
+
+	MOVQ	DX, ctx-56(SP)
+	MOVQ	SI, info-64(SP)
+	MOVQ	DI, signum-72(SP)
 	CALL	runtime·sigtrampgo(SB)
+
+	MOVQ	r15-48(SP), R15
+	MOVQ	r14-40(SP), R14
+	MOVQ	r13-32(SP), R13
+	MOVQ	r12-24(SP), R12
+	MOVQ	bp-16(SP),  BP
+	MOVQ	bx-8(SP),   BX
 	RET
 
 TEXT runtime·mmap(SB),NOSPLIT,$0
diff --git a/src/runtime/sys_linux_386.s b/src/runtime/sys_linux_386.s
index 1d798c741e..45320c068a 100644
--- a/src/runtime/sys_linux_386.s
+++ b/src/runtime/sys_linux_386.s
@@ -228,7 +228,15 @@ TEXT runtime·sigfwd(SB),NOSPLIT,$12-16
 	MOVL	AX, SP
 	RET
 
-TEXT runtime·sigtramp(SB),NOSPLIT,$12
+TEXT runtime·sigtramp(SB),NOSPLIT,$28
+	// Save callee-saved C registers, since the caller may be a C signal handler.
+	MOVL	BX, bx-4(SP)
+	MOVL	BP, bp-8(SP)
+	MOVL	SI, si-12(SP)
+	MOVL	DI, di-16(SP)
+	// We don't save mxcsr or the x87 control word because sigtrampgo doesn't
+	// modify them.
+
 	MOVL	sig+0(FP), BX
 	MOVL	BX, 0(SP)
 	MOVL	info+4(FP), BX
@@ -236,6 +244,11 @@ TEXT runtime·sigtramp(SB),NOSPLIT,$12
 	MOVL	ctx+8(FP), BX
 	MOVL	BX, 8(SP)
 	CALL	runtime·sigtrampgo(SB)
+
+	MOVL	di-16(SP), DI
+	MOVL	si-12(SP), SI
+	MOVL	bp-8(SP),  BP
+	MOVL	bx-4(SP),  BX
 	RET
 
 TEXT runtime·cgoSigtramp(SB),NOSPLIT,$0
diff --git a/src/runtime/sys_linux_amd64.s b/src/runtime/sys_linux_amd64.s
index 832b98b674..839df16406 100644
--- a/src/runtime/sys_linux_amd64.s
+++ b/src/runtime/sys_linux_amd64.s
@@ -244,12 +244,29 @@ TEXT runtime·sigfwd(SB),NOSPLIT,$0-32
 	POPQ	BP
 	RET
 
-TEXT runtime·sigtramp(SB),NOSPLIT,$24
-	MOVQ	DI, 0(SP)   // signum
-	MOVQ	SI, 8(SP)   // info
-	MOVQ	DX, 16(SP)  // ctx
+TEXT runtime·sigtramp(SB),NOSPLIT,$72
+	// Save callee-saved C registers, since the caller may be a C signal handler.
+	MOVQ	BX,  bx-8(SP)
+	MOVQ	BP,  bp-16(SP)  // save in case GOEXPERIMENT=noframepointer is set
+	MOVQ	R12, r12-24(SP)
+	MOVQ	R13, r13-32(SP)
+	MOVQ	R14, r14-40(SP)
+	MOVQ	R15, r15-48(SP)
+	// We don't save mxcsr or the x87 control word because sigtrampgo doesn't
+	// modify them.
+
+	MOVQ	DX, ctx-56(SP)
+	MOVQ	SI, info-64(SP)
+	MOVQ	DI, signum-72(SP)
 	MOVQ	$runtime·sigtrampgo(SB), AX
 	CALL AX
+
+	MOVQ	r15-48(SP), R15
+	MOVQ	r14-40(SP), R14
+	MOVQ	r13-32(SP), R13
+	MOVQ	r12-24(SP), R12
+	MOVQ	bp-16(SP),  BP
+	MOVQ	bx-8(SP),   BX
 	RET
 
 // Used instead of sigtramp in programs that use cgo.
diff --git a/src/runtime/sys_netbsd_386.s b/src/runtime/sys_netbsd_386.s
index 50d35e5b5c..8c4f004a4b 100644
--- a/src/runtime/sys_netbsd_386.s
+++ b/src/runtime/sys_netbsd_386.s
@@ -232,7 +232,15 @@ TEXT runtime·sigfwd(SB),NOSPLIT,$12-16
 	MOVL	AX, SP
 	RET
 
-TEXT runtime·sigtramp(SB),NOSPLIT,$12
+TEXT runtime·sigtramp(SB),NOSPLIT,$28
+	// Save callee-saved C registers, since the caller may be a C signal handler.
+	MOVL	BX, bx-4(SP)
+	MOVL	BP, bp-8(SP)
+	MOVL	SI, si-12(SP)
+	MOVL	DI, di-16(SP)
+	// We don't save mxcsr or the x87 control word because sigtrampgo doesn't
+	// modify them.
+
 	MOVL	signo+0(FP), BX
 	MOVL	BX, 0(SP)
 	MOVL	info+4(FP), BX
@@ -240,6 +248,11 @@ TEXT runtime·sigtramp(SB),NOSPLIT,$12
 	MOVL	context+8(FP), BX
 	MOVL	BX, 8(SP)
 	CALL	runtime·sigtrampgo(SB)
+
+	MOVL	di-16(SP), DI
+	MOVL	si-12(SP), SI
+	MOVL	bp-8(SP),  BP
+	MOVL	bx-4(SP),  BX
 	RET
 
 // int32 lwp_create(void *context, uintptr flags, void *lwpid);
diff --git a/src/runtime/sys_netbsd_amd64.s b/src/runtime/sys_netbsd_amd64.s
index 2c50adb123..7c7771bcba 100644
--- a/src/runtime/sys_netbsd_amd64.s
+++ b/src/runtime/sys_netbsd_amd64.s
@@ -250,13 +250,28 @@ TEXT runtime·sigfwd(SB),NOSPLIT,$0-32
 	POPQ	BP
 	RET
 
-TEXT runtime·sigtramp(SB),NOSPLIT,$32
-	MOVQ	DI, 0(SP)   // signum
-	MOVQ	SI, 8(SP)   // info
-	MOVQ	DX, 16(SP)  // ctx
-	MOVQ	R15, 24(SP) // for sigreturn
+TEXT runtime·sigtramp(SB),NOSPLIT,$72
+	// Save callee-saved C registers, since the caller may be a C signal handler.
+	MOVQ	BX,  bx-8(SP)
+	MOVQ	BP,  bp-16(SP)  // save in case GOEXPERIMENT=noframepointer is set
+	MOVQ	R12, r12-24(SP)
+	MOVQ	R13, r13-32(SP)
+	MOVQ	R14, r14-40(SP)
+	MOVQ	R15, r15-48(SP)
+	// We don't save mxcsr or the x87 control word because sigtrampgo doesn't
+	// modify them.
+
+	MOVQ	DX, ctx-56(SP)
+	MOVQ	SI, info-64(SP)
+	MOVQ	DI, signum-72(SP)
 	CALL	runtime·sigtrampgo(SB)
-	MOVQ	24(SP), R15
+
+	MOVQ	r15-48(SP), R15
+	MOVQ	r14-40(SP), R14
+	MOVQ	r13-32(SP), R13
+	MOVQ	r12-24(SP), R12
+	MOVQ	bp-16(SP),  BP
+	MOVQ	bx-8(SP),   BX
 	RET
 
 TEXT runtime·mmap(SB),NOSPLIT,$0
diff --git a/src/runtime/sys_openbsd_386.s b/src/runtime/sys_openbsd_386.s
index 997c07fe17..76d22b0131 100644
--- a/src/runtime/sys_openbsd_386.s
+++ b/src/runtime/sys_openbsd_386.s
@@ -213,7 +213,15 @@ TEXT runtime·sigfwd(SB),NOSPLIT,$12-16
 	MOVL	AX, SP
 	RET
 
-TEXT runtime·sigtramp(SB),NOSPLIT,$12
+TEXT runtime·sigtramp(SB),NOSPLIT,$28
+	// Save callee-saved C registers, since the caller may be a C signal handler.
+	MOVL	BX, bx-4(SP)
+	MOVL	BP, bp-8(SP)
+	MOVL	SI, si-12(SP)
+	MOVL	DI, di-16(SP)
+	// We don't save mxcsr or the x87 control word because sigtrampgo doesn't
+	// modify them.
+
 	MOVL	signo+0(FP), BX
 	MOVL	BX, 0(SP)
 	MOVL	info+4(FP), BX
@@ -221,6 +229,11 @@ TEXT runtime·sigtramp(SB),NOSPLIT,$12
 	MOVL	context+8(FP), BX
 	MOVL	BX, 8(SP)
 	CALL	runtime·sigtrampgo(SB)
+
+	MOVL	di-16(SP), DI
+	MOVL	si-12(SP), SI
+	MOVL	bp-8(SP),  BP
+	MOVL	bx-4(SP),  BX
 	RET
 
 // int32 tfork(void *param, uintptr psize, M *mp, G *gp, void (*fn)(void));
diff --git a/src/runtime/sys_openbsd_amd64.s b/src/runtime/sys_openbsd_amd64.s
index 6ca5a81d2a..cf7a3fb7a9 100644
--- a/src/runtime/sys_openbsd_amd64.s
+++ b/src/runtime/sys_openbsd_amd64.s
@@ -242,11 +242,28 @@ TEXT runtime·sigfwd(SB),NOSPLIT,$0-32
 	POPQ	BP
 	RET
 
-TEXT runtime·sigtramp(SB),NOSPLIT,$24
-	MOVQ	DI, 0(SP)
-	MOVQ	SI, 8(SP)
-	MOVQ	DX, 16(SP)
+TEXT runtime·sigtramp(SB),NOSPLIT,$72
+	// Save callee-saved C registers, since the caller may be a C signal handler.
+	MOVQ	BX,  bx-8(SP)
+	MOVQ	BP,  bp-16(SP)  // save in case GOEXPERIMENT=noframepointer is set
+	MOVQ	R12, r12-24(SP)
+	MOVQ	R13, r13-32(SP)
+	MOVQ	R14, r14-40(SP)
+	MOVQ	R15, r15-48(SP)
+	// We don't save mxcsr or the x87 control word because sigtrampgo doesn't
+	// modify them.
+
+	MOVQ	DX, ctx-56(SP)
+	MOVQ	SI, info-64(SP)
+	MOVQ	DI, signum-72(SP)
 	CALL	runtime·sigtrampgo(SB)
+
+	MOVQ	r15-48(SP), R15
+	MOVQ	r14-40(SP), R14
+	MOVQ	r13-32(SP), R13
+	MOVQ	r12-24(SP), R12
+	MOVQ	bp-16(SP),  BP
+	MOVQ	bx-8(SP),   BX
 	RET
 
 TEXT runtime·mmap(SB),NOSPLIT,$0