cmd/cgo, runtime: write cgo stub wrappers in Go, not C

LGTM=alex.brainman, iant
R=golang-codereviews, alex.brainman, iant
CC=dvyukov, golang-codereviews, khr, r
https://codereview.appspot.com/139070043

7 files changed, 48 insertions, 4 deletions

diff --git a/src/pkg/runtime/asm_386.s b/src/pkg/runtime/asm_386.s
index 07158ef0f..8a5fd3fb0 100644
--- a/src/pkg/runtime/asm_386.s
+++ b/src/pkg/runtime/asm_386.s
@@ -680,7 +680,15 @@ 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,$0-8
+TEXT runtime·asmcgocall(SB),NOSPLIT,$12-8
+	MOVL	fn+0(FP), AX
+	MOVL	arg+4(FP), BX
+	MOVL	AX, 0(SP)
+	MOVL	BX, 4(SP)
+	CALL	runtime·asmcgocall_errno(SB)
+	RET
+
+TEXT runtime·asmcgocall_errno(SB),NOSPLIT,$0-12
 	MOVL	fn+0(FP), AX
 	MOVL	arg+4(FP), BX
 	MOVL	SP, DX
@@ -712,6 +720,7 @@ TEXT runtime·asmcgocall(SB),NOSPLIT,$0-8
 	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 1d98fc265..0846966f1 100644
--- a/src/pkg/runtime/asm_amd64.s
+++ b/src/pkg/runtime/asm_amd64.s
@@ -764,7 +764,15 @@ 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,$0-16
+TEXT runtime·asmcgocall(SB),NOSPLIT,$24-16
+	MOVQ	fn+0(FP), AX
+	MOVQ	arg+8(FP), BX
+	MOVQ	AX, 0(SP)
+	MOVQ	BX, 8(SP)
+	CALL	runtime·asmcgocall_errno(SB)
+	RET
+
+TEXT runtime·asmcgocall_errno(SB),NOSPLIT,$0-20
 	MOVQ	fn+0(FP), AX
 	MOVQ	arg+8(FP), BX
 	MOVQ	SP, DX
@@ -805,6 +813,7 @@ 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_amd64p32.s b/src/pkg/runtime/asm_amd64p32.s
index 20069a6c7..7886861eb 100644
--- a/src/pkg/runtime/asm_amd64p32.s
+++ b/src/pkg/runtime/asm_amd64p32.s
@@ -711,6 +711,12 @@ TEXT runtime·asmcgocall(SB),NOSPLIT,$0-8
 	MOVL	0, AX
 	RET
 
+// asmcgocall(void(*fn)(void*), void *arg)
+// Not implemented.
+TEXT runtime·asmcgocall_errno(SB),NOSPLIT,$0-12
+	MOVL	0, AX
+	RET
+
 // cgocallback(void (*fn)(void*), void *frame, uintptr framesize)
 // Not implemented.
 TEXT runtime·cgocallback(SB),NOSPLIT,$0-12
diff --git a/src/pkg/runtime/asm_arm.s b/src/pkg/runtime/asm_arm.s
index 6e12cf60f..67763e1b2 100644
--- a/src/pkg/runtime/asm_arm.s
+++ b/src/pkg/runtime/asm_arm.s
@@ -493,7 +493,15 @@ 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,$0-8
+TEXT	runtime·asmcgocall(SB),NOSPLIT,$12-8
+	MOVW	fn+0(FP), R1
+	MOVW	arg+4(FP), R2
+	MOVW	R1, 0(R13)
+	MOVW	R2, 4(R13)
+	BL	runtime·asmcgocall_errno(SB)
+	RET
+
+TEXT runtime·asmcgocall_errno(SB),NOSPLIT,$0-12
 	MOVW	fn+0(FP), R1
 	MOVW	arg+4(FP), R0
 	MOVW	R13, R2
@@ -521,6 +529,7 @@ TEXT	runtime·asmcgocall(SB),NOSPLIT,$0-8
 	// 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)
diff --git a/src/pkg/runtime/cgocall.c b/src/pkg/runtime/cgocall.c
index 145ac7dc1..0fd5fbd00 100644
--- a/src/pkg/runtime/cgocall.c
+++ b/src/pkg/runtime/cgocall.c
@@ -97,7 +97,14 @@ static FuncVal endcgoV = { endcgo };
 void
 runtime·cgocall(void (*fn)(void*), void *arg)
 {
+	runtime·cgocall_errno(fn, arg);
+}
+
+int32
+runtime·cgocall_errno(void (*fn)(void*), void *arg)
+{
 	Defer d;
+	int32 errno;
 
 	if(!runtime·iscgo && !Solaris && !Windows)
 		runtime·throw("cgocall unavailable");
@@ -140,13 +147,15 @@ runtime·cgocall(void (*fn)(void*), void *arg)
 	 * the $GOMAXPROCS accounting.
 	 */
 	runtime·entersyscall();
-	runtime·asmcgocall(fn, arg);
+	errno = runtime·asmcgocall_errno(fn, arg);
 	runtime·exitsyscall();
 
 	if(g->defer != &d || d.fn != &endcgoV)
 		runtime·throw("runtime: bad defer entry in cgocallback");
 	g->defer = d.link;
 	endcgo();
+	
+	return errno;
 }
 
 static void
diff --git a/src/pkg/runtime/cgocall.h b/src/pkg/runtime/cgocall.h
index 253661a7e..c87a9cdc5 100644
--- a/src/pkg/runtime/cgocall.h
+++ b/src/pkg/runtime/cgocall.h
@@ -7,6 +7,7 @@
  */
 
 void runtime·cgocall(void (*fn)(void*), void*);
+int32 runtime·cgocall_errno(void (*fn)(void*), void*);
 void runtime·cgocallback(void (*fn)(void), void*, uintptr);
 void *runtime·cmalloc(uintptr);
 void runtime·cfree(void*);
diff --git a/src/pkg/runtime/runtime.h b/src/pkg/runtime/runtime.h
index d67d7a007..0d25ca6c5 100644
--- a/src/pkg/runtime/runtime.h
+++ b/src/pkg/runtime/runtime.h
@@ -848,6 +848,7 @@ void	runtime·tsleep(int64, String);
 M*	runtime·newm(void);
 void	runtime·goexit(void);
 void	runtime·asmcgocall(void (*fn)(void*), void*);
+int32	runtime·asmcgocall_errno(void (*fn)(void*), void*);
 void	runtime·entersyscall(void);
 void	runtime·entersyscallblock(void);
 void	runtime·exitsyscall(void);