diff --git a/misc/cgo/test/callback.go b/misc/cgo/test/callback.go
index 67d271404a..98f653ef77 100644
--- a/misc/cgo/test/callback.go
+++ b/misc/cgo/test/callback.go
@@ -156,6 +156,7 @@ func testCallbackCallers(t *testing.T) {
 		"runtime.cgocallbackg1",
 		"runtime.cgocallbackg",
 		"runtime.cgocallback_gofunc",
+		"asmcgocall",
 		"runtime.asmcgocall_errno",
 		"runtime.cgocall_errno",
 		"test._Cfunc_callback",
@@ -182,8 +183,12 @@ func testCallbackCallers(t *testing.T) {
 		if strings.HasPrefix(fname, "_") {
 			fname = path.Base(f.Name()[1:])
 		}
-		if fname != name[i] {
-			t.Errorf("expected function name %s, got %s", name[i], fname)
+		namei := ""
+		if i < len(name) {
+			namei = name[i]
+		}
+		if fname != namei {
+			t.Errorf("stk[%d] = %q, want %q", i, fname, namei)
 		}
 	}
 }
diff --git a/src/pkg/runtime/asm_386.s b/src/pkg/runtime/asm_386.s
index 2477726f51..aafe960ce3 100644
--- a/src/pkg/runtime/asm_386.s
+++ b/src/pkg/runtime/asm_386.s
@@ -680,17 +680,21 @@ TEXT gosave<>(SB),NOSPLIT,$0
 // Call fn(arg) on the scheduler stack,
 // aligned appropriately for the gcc ABI.
 // See cgocall.c for more details.
-TEXT runtime·asmcgocall(SB),NOSPLIT,$12-8
+TEXT runtime·asmcgocall(SB),NOSPLIT,$0-8
 	MOVL	fn+0(FP), AX
 	MOVL	arg+4(FP), BX
-	MOVL	AX, 0(SP)
-	MOVL	BX, 4(SP)
-	CALL	runtime·asmcgocall_errno(SB)
+	CALL	asmcgocall<>(SB)
 	RET
 
 TEXT runtime·asmcgocall_errno(SB),NOSPLIT,$0-12
 	MOVL	fn+0(FP), AX
 	MOVL	arg+4(FP), BX
+	CALL	asmcgocall<>(SB)
+	MOVL	AX, ret+8(FP)
+	RET
+
+TEXT asmcgocall<>(SB),NOSPLIT,$0-12
+	// fn in AX, arg in BX
 	MOVL	SP, DX
 
 	// Figure out if we need to switch to m->g0 stack.
@@ -720,7 +724,6 @@ TEXT runtime·asmcgocall_errno(SB),NOSPLIT,$0-12
 	MOVL	8(SP), DI
 	MOVL	DI, g(CX)
 	MOVL	4(SP), SP
-	MOVL	AX, ret+8(FP)
 	RET
 
 // cgocallback(void (*fn)(void*), void *frame, uintptr framesize)
diff --git a/src/pkg/runtime/asm_amd64.s b/src/pkg/runtime/asm_amd64.s
index d7e30de7b4..5840b56c81 100644
--- a/src/pkg/runtime/asm_amd64.s
+++ b/src/pkg/runtime/asm_amd64.s
@@ -764,17 +764,21 @@ TEXT gosave<>(SB),NOSPLIT,$0
 // Call fn(arg) on the scheduler stack,
 // aligned appropriately for the gcc ABI.
 // See cgocall.c for more details.
-TEXT runtime·asmcgocall(SB),NOSPLIT,$24-16
+TEXT runtime·asmcgocall(SB),NOSPLIT,$0-16
 	MOVQ	fn+0(FP), AX
 	MOVQ	arg+8(FP), BX
-	MOVQ	AX, 0(SP)
-	MOVQ	BX, 8(SP)
-	CALL	runtime·asmcgocall_errno(SB)
+	CALL	asmcgocall<>(SB)
 	RET
 
 TEXT runtime·asmcgocall_errno(SB),NOSPLIT,$0-20
 	MOVQ	fn+0(FP), AX
 	MOVQ	arg+8(FP), BX
+	CALL	asmcgocall<>(SB)
+	MOVL	AX, ret+16(FP)
+	RET
+
+// asmcgocall common code. fn in AX, arg in BX. returns errno in AX.
+TEXT asmcgocall<>(SB),NOSPLIT,$0-0
 	MOVQ	SP, DX
 
 	// Figure out if we need to switch to m->g0 stack.
@@ -813,7 +817,6 @@ nosave:
 	MOVQ	48(SP), DI
 	MOVQ	DI, g(CX)
 	MOVQ	40(SP), SP
-	MOVL	AX, ret+16(FP)
 	RET
 
 // cgocallback(void (*fn)(void*), void *frame, uintptr framesize)
diff --git a/src/pkg/runtime/asm_arm.s b/src/pkg/runtime/asm_arm.s
index 26b58cfb17..49a863258c 100644
--- a/src/pkg/runtime/asm_arm.s
+++ b/src/pkg/runtime/asm_arm.s
@@ -493,17 +493,21 @@ TEXT gosave<>(SB),NOSPLIT,$0
 // Call fn(arg) on the scheduler stack,
 // aligned appropriately for the gcc ABI.
 // See cgocall.c for more details.
-TEXT	runtime·asmcgocall(SB),NOSPLIT,$12-8
+TEXT	runtime·asmcgocall(SB),NOSPLIT,$0-8
 	MOVW	fn+0(FP), R1
-	MOVW	arg+4(FP), R2
-	MOVW	R1, 0(R13)
-	MOVW	R2, 4(R13)
-	BL	runtime·asmcgocall_errno(SB)
+	MOVW	arg+4(FP), R0
+	BL	asmcgocall<>(SB)
 	RET
 
 TEXT runtime·asmcgocall_errno(SB),NOSPLIT,$0-12
 	MOVW	fn+0(FP), R1
 	MOVW	arg+4(FP), R0
+	BL	asmcgocall<>(SB)
+	MOVW	R0, ret+8(FP)
+	RET
+
+TEXT asmcgocall<>(SB),NOSPLIT,$0-0
+	// fn in R1, arg in R0.
 	MOVW	R13, R2
 	MOVW	g, R5
 
@@ -529,7 +533,6 @@ TEXT runtime·asmcgocall_errno(SB),NOSPLIT,$0-12
 	// Restore registers, g, stack pointer.
 	MOVW	20(R13), g
 	MOVW	16(R13), R13
-	MOVW	R0, ret+8(FP)
 	RET
 
 // cgocallback(void (*fn)(void*), void *frame, uintptr framesize)