runtime: fix windows syscalls for copying stacks

Syscall and everything it calls must be nosplit:
we cannot split a stack once Syscall has been invoked,
because we don't know which of its arguments are
pointers.

LGTM=khr, r, alex.brainman
R=dvyukov, iant, khr, r, bradfitz, alex.brainman
CC=golang-codereviews
https://golang.org/cl/133670043

src/pkg/runtime/cgocall.go

@@ -82,10 +82,12 @@ package runtime
 import "unsafe"
 
 // Call from Go to C.
+//go:nosplit
 func cgocall(fn, arg unsafe.Pointer) {
 	cgocall_errno(fn, arg)
 }
 
+//go:nosplit
 func cgocall_errno(fn, arg unsafe.Pointer) int32 {
 	if !iscgo && GOOS != "solaris" && GOOS != "windows" {
 		gothrow("cgocall unavailable")

src/pkg/runtime/os_windows.c

@@ -158,12 +158,14 @@ runtime·goenvs(void)
 	runtime·stdcall1(runtime·FreeEnvironmentStringsW, (uintptr)env);
 }
 
+#pragma textflag NOSPLIT
 void
 runtime·exit(int32 code)
 {
 	runtime·stdcall1(runtime·ExitProcess, code);
 }
 
+#pragma textflag NOSPLIT
 int32
 runtime·write(uintptr fd, void *buf, int32 n)
 {
@@ -206,12 +208,14 @@ runtime·semasleep(int64 ns)
 	return 0;
 }
 
+#pragma textflag NOSPLIT
 void
 runtime·semawakeup(M *mp)
 {
 	runtime·stdcall1(runtime·SetEvent, mp->waitsema);
 }
 
+#pragma textflag NOSPLIT
 uintptr
 runtime·semacreate(void)
 {
@@ -272,12 +276,15 @@ typedef struct KSYSTEM_TIME {
 const KSYSTEM_TIME* INTERRUPT_TIME	= (KSYSTEM_TIME*)0x7ffe0008;
 const KSYSTEM_TIME* SYSTEM_TIME		= (KSYSTEM_TIME*)0x7ffe0014;
 
+static void badsystime(void);
+
 #pragma textflag NOSPLIT
 int64
 runtime·systime(KSYSTEM_TIME *timeaddr)
 {
 	KSYSTEM_TIME t;
 	int32 i;
+	void (*fn)(void);
 
 	for(i = 1; i < 10000; i++) {
 		// these fields must be read in that order (see URL above)
@@ -289,10 +296,17 @@ runtime·systime(KSYSTEM_TIME *timeaddr)
 		if((i%100) == 0)
 			runtime·osyield();
 	}
-	runtime·throw("interrupt/system time is changing too fast");
+	fn = badsystime;
+	runtime·onM(&fn);
 	return 0;
 }
 
+static void
+badsystime(void)
+{
+	runtime·throw("interrupt/system time is changing too fast");
+}
+
 #pragma textflag NOSPLIT
 int64
 runtime·nanotime(void)
@@ -300,6 +314,7 @@ runtime·nanotime(void)
 	return runtime·systime(INTERRUPT_TIME) * 100LL;
 }
 
+#pragma textflag NOSPLIT
 void
 time·now(int64 sec, int32 usec)
 {

src/pkg/runtime/syscall_windows.goc → src/pkg/runtime/syscall_windows.c

@@ -2,41 +2,68 @@
 // Use of this source code is governed by a BSD-style
 // license that can be found in the LICENSE file.
 
-package syscall
 #include "runtime.h"
 #include "os_GOOS.h"
 #include "cgocall.h"
+#include "textflag.h"
 
-func loadlibrary(filename *uint16) (handle uintptr, err uintptr) {
+typedef struct HandleErr HandleErr;
+typedef struct SyscallErr SyscallErr;
+
+struct HandleErr {
+	uintptr handle;
+	uintptr err;
+};
+
+struct SyscallErr {
+	uintptr r1;
+	uintptr r2;
+	uintptr err;
+};
+
+#pragma textflag NOSPLIT
+HandleErr
+syscall·loadlibrary(uint16 *filename)
+{
 	LibCall c;
+	HandleErr r;
 
 	c.fn = runtime·LoadLibrary;
 	c.n = 1;
 	c.args = &filename;
-	runtime·cgocall(runtime·asmstdcall, &c);
-	handle = c.r1;
-	if(handle == 0)
-		err = c.err;
+	runtime·cgocall_errno(runtime·asmstdcall, &c);
+	r.handle = c.r1;
+	if(r.handle == 0)
+		r.err = c.err;
 	else
-		err = 0;
+		r.err = 0;
+	return r;
 }
 
-func getprocaddress(handle uintptr, procname *uint8) (proc uintptr, err uintptr) {
+#pragma textflag NOSPLIT
+HandleErr
+syscall·getprocaddress(uintptr handle, int8 *procname)
+{
 	LibCall c;
+	HandleErr r;
 
 	USED(procname);
 	c.fn = runtime·GetProcAddress;
 	c.n = 2;
 	c.args = &handle;
-	runtime·cgocall(runtime·asmstdcall, &c);
-	proc = c.r1;
-	if(proc == 0)
-		err = c.err;
+	runtime·cgocall_errno(runtime·asmstdcall, &c);
+	r.handle = c.r1;
+	if(r.handle == 0)
+		r.err = c.err;
 	else
-		err = 0;
+		r.err = 0;
+	return r;
 }
 
-func Syscall(fn uintptr, nargs uintptr, a1 uintptr, a2 uintptr, a3 uintptr) (r1 uintptr, r2 uintptr, err uintptr) {
+#pragma textflag NOSPLIT
+SyscallErr
+syscall·Syscall(uintptr fn, uintptr nargs, uintptr a1, uintptr a2, uintptr a3)
+{
 	LibCall c;
 
 	USED(a2);
@@ -44,13 +71,14 @@ func Syscall(fn uintptr, nargs uintptr, a1 uintptr, a2 uintptr, a3 uintptr) (r1
 	c.fn = (void*)fn;
 	c.n = nargs;
 	c.args = &a1;
-	runtime·cgocall(runtime·asmstdcall, &c);
-	err = c.err;
-	r1 = c.r1;
-	r2 = c.r2;
+	runtime·cgocall_errno(runtime·asmstdcall, &c);
+	return (SyscallErr){c.r1, c.r2, c.err};
 }
 
-func Syscall6(fn uintptr, nargs uintptr, a1 uintptr, a2 uintptr, a3 uintptr, a4 uintptr, a5 uintptr, a6 uintptr) (r1 uintptr, r2 uintptr, err uintptr) {
+#pragma textflag NOSPLIT
+SyscallErr
+syscall·Syscall6(uintptr fn, uintptr nargs, uintptr a1, uintptr a2, uintptr a3, uintptr a4, uintptr a5, uintptr a6)
+{
 	LibCall c;
 
 	USED(a2);
@@ -61,13 +89,14 @@ func Syscall6(fn uintptr, nargs uintptr, a1 uintptr, a2 uintptr, a3 uintptr, a4
 	c.fn = (void*)fn;
 	c.n = nargs;
 	c.args = &a1;
-	runtime·cgocall(runtime·asmstdcall, &c);
-	err = c.err;
-	r1 = c.r1;
-	r2 = c.r2;
+	runtime·cgocall_errno(runtime·asmstdcall, &c);
+	return (SyscallErr){c.r1, c.r2, c.err};
 }
 
-func Syscall9(fn uintptr, nargs uintptr, a1 uintptr, a2 uintptr, a3 uintptr, a4 uintptr, a5 uintptr, a6 uintptr, a7 uintptr, a8 uintptr, a9 uintptr) (r1 uintptr, r2 uintptr, err uintptr) {
+#pragma textflag NOSPLIT
+SyscallErr
+syscall·Syscall9(uintptr fn, uintptr nargs, uintptr a1, uintptr a2, uintptr a3, uintptr a4, uintptr a5, uintptr a6, uintptr a7, uintptr a8, uintptr a9)
+{
 	LibCall c;
 
 	USED(a2);
@@ -81,13 +110,14 @@ func Syscall9(fn uintptr, nargs uintptr, a1 uintptr, a2 uintptr, a3 uintptr, a4
 	c.fn = (void*)fn;
 	c.n = nargs;
 	c.args = &a1;
-	runtime·cgocall(runtime·asmstdcall, &c);
-	err = c.err;
-	r1 = c.r1;
-	r2 = c.r2;
+	runtime·cgocall_errno(runtime·asmstdcall, &c);
+	return (SyscallErr){c.r1, c.r2, c.err};
 }
 
-func Syscall12(fn uintptr, nargs uintptr, a1 uintptr, a2 uintptr, a3 uintptr, a4 uintptr, a5 uintptr, a6 uintptr, a7 uintptr, a8 uintptr, a9 uintptr, a10 uintptr, a11 uintptr, a12 uintptr) (r1 uintptr, r2 uintptr, err uintptr) {
+#pragma textflag NOSPLIT
+SyscallErr
+syscall·Syscall12(uintptr fn, uintptr nargs, uintptr a1, uintptr a2, uintptr a3, uintptr a4, uintptr a5, uintptr a6, uintptr a7, uintptr a8, uintptr a9, uintptr a10, uintptr a11, uintptr a12)
+{
 	LibCall c;
 
 	USED(a2);
@@ -104,13 +134,14 @@ func Syscall12(fn uintptr, nargs uintptr, a1 uintptr, a2 uintptr, a3 uintptr, a4
 	c.fn = (void*)fn;
 	c.n = nargs;
 	c.args = &a1;
-	runtime·cgocall(runtime·asmstdcall, &c);
-	err = c.err;
-	r1 = c.r1;
-	r2 = c.r2;
+	runtime·cgocall_errno(runtime·asmstdcall, &c);
+	return (SyscallErr){c.r1, c.r2, c.err};
 }
 
-func Syscall15(fn uintptr, nargs uintptr, a1 uintptr, a2 uintptr, a3 uintptr, a4 uintptr, a5 uintptr, a6 uintptr, a7 uintptr, a8 uintptr, a9 uintptr, a10 uintptr, a11 uintptr, a12 uintptr, a13 uintptr, a14 uintptr, a15 uintptr) (r1 uintptr, r2 uintptr, err uintptr) {
+#pragma textflag NOSPLIT
+SyscallErr
+syscall·Syscall15(uintptr fn, uintptr nargs, uintptr a1, uintptr a2, uintptr a3, uintptr a4, uintptr a5, uintptr a6, uintptr a7, uintptr a8, uintptr a9, uintptr a10, uintptr a11, uintptr a12, uintptr a13, uintptr a14, uintptr a15)
+{
 	LibCall c;
 
 	USED(a2);
@@ -130,8 +161,6 @@ func Syscall15(fn uintptr, nargs uintptr, a1 uintptr, a2 uintptr, a3 uintptr, a4
 	c.fn = (void*)fn;
 	c.n = nargs;
 	c.args = &a1;
-	runtime·cgocall(runtime·asmstdcall, &c);
-	err = c.err;
-	r1 = c.r1;
-	r2 = c.r2;
+	runtime·cgocall_errno(runtime·asmstdcall, &c);
+	return (SyscallErr){c.r1, c.r2, c.err};
 }