runtime: store syscall parameters in m not on stack

Stack can move during callback, so libcall struct cannot be stored on stack.
asmstdcall updates return values and errno in libcall struct parameter, but
these could be at different location when callback returns.
Store these in m, so they are not affected by GC.

Fixes #10406

Change-Id: Id01c9d2b4b44530494e6d9e9e1c875261ce477cd
Reviewed-on: https://go-review.googlesource.com/10370Reviewed-by: Russ Cox <rsc@golang.org>

src/runtime/cgocall.go

@@ -163,6 +163,10 @@ func cgocallbackg() {
 		exit(2)
 	}
 
+	// Save current syscall parameters, so m.syscall can be
+	// used again if callback decide to make syscall.
+	syscall := gp.m.syscall
+
 	// entersyscall saves the caller's SP to allow the GC to trace the Go
 	// stack. However, since we're returning to an earlier stack frame and
 	// need to pair with the entersyscall() call made by cgocall, we must
@@ -173,6 +177,8 @@ func cgocallbackg() {
 	cgocallbackg1()
 	// going back to cgo call
 	reentersyscall(savedpc, uintptr(savedsp))
+
+	gp.m.syscall = syscall
 }
 
 func cgocallbackg1() {

src/runtime/runtime2.go

@@ -332,6 +332,7 @@ type m struct {
 	libcallpc uintptr // for cpu profiler
 	libcallsp uintptr
 	libcallg  guintptr
+	syscall   libcall // stores syscall parameters on windows
 	//#endif
 	//#ifdef GOOS_solaris
 	perrno *int32 // pointer to tls errno

src/runtime/syscall_windows.go

@@ -91,11 +91,11 @@ func compileCallback(fn eface, cleanstack bool) (code uintptr) {
 //go:linkname syscall_loadlibrary syscall.loadlibrary
 //go:nosplit
 func syscall_loadlibrary(filename *uint16) (handle, err uintptr) {
-	var c libcall
+	c := &getg().m.syscall
 	c.fn = getLoadLibrary()
 	c.n = 1
-	c.args = uintptr(unsafe.Pointer(&filename))
-	cgocall(asmstdcallAddr, unsafe.Pointer(&c))
+	c.args = uintptr(noescape(unsafe.Pointer(&filename)))
+	cgocall(asmstdcallAddr, unsafe.Pointer(c))
 	handle = c.r1
 	if handle == 0 {
 		err = c.err
@@ -106,11 +106,11 @@ func syscall_loadlibrary(filename *uint16) (handle, err uintptr) {
 //go:linkname syscall_getprocaddress syscall.getprocaddress
 //go:nosplit
 func syscall_getprocaddress(handle uintptr, procname *byte) (outhandle, err uintptr) {
-	var c libcall
+	c := &getg().m.syscall
 	c.fn = getGetProcAddress()
 	c.n = 2
-	c.args = uintptr(unsafe.Pointer(&handle))
-	cgocall(asmstdcallAddr, unsafe.Pointer(&c))
+	c.args = uintptr(noescape(unsafe.Pointer(&handle)))
+	cgocall(asmstdcallAddr, unsafe.Pointer(c))
 	outhandle = c.r1
 	if outhandle == 0 {
 		err = c.err
@@ -121,54 +121,54 @@ func syscall_getprocaddress(handle uintptr, procname *byte) (outhandle, err uint
 //go:linkname syscall_Syscall syscall.Syscall
 //go:nosplit
 func syscall_Syscall(fn, nargs, a1, a2, a3 uintptr) (r1, r2, err uintptr) {
-	var c libcall
+	c := &getg().m.syscall
 	c.fn = fn
 	c.n = nargs
-	c.args = uintptr(unsafe.Pointer(&a1))
-	cgocall(asmstdcallAddr, unsafe.Pointer(&c))
+	c.args = uintptr(noescape(unsafe.Pointer(&a1)))
+	cgocall(asmstdcallAddr, unsafe.Pointer(c))
 	return c.r1, c.r2, c.err
 }
 
 //go:linkname syscall_Syscall6 syscall.Syscall6
 //go:nosplit
 func syscall_Syscall6(fn, nargs, a1, a2, a3, a4, a5, a6 uintptr) (r1, r2, err uintptr) {
-	var c libcall
+	c := &getg().m.syscall
 	c.fn = fn
 	c.n = nargs
-	c.args = uintptr(unsafe.Pointer(&a1))
-	cgocall(asmstdcallAddr, unsafe.Pointer(&c))
+	c.args = uintptr(noescape(unsafe.Pointer(&a1)))
+	cgocall(asmstdcallAddr, unsafe.Pointer(c))
 	return c.r1, c.r2, c.err
 }
 
 //go:linkname syscall_Syscall9 syscall.Syscall9
 //go:nosplit
 func syscall_Syscall9(fn, nargs, a1, a2, a3, a4, a5, a6, a7, a8, a9 uintptr) (r1, r2, err uintptr) {
-	var c libcall
+	c := &getg().m.syscall
 	c.fn = fn
 	c.n = nargs
-	c.args = uintptr(unsafe.Pointer(&a1))
-	cgocall(asmstdcallAddr, unsafe.Pointer(&c))
+	c.args = uintptr(noescape(unsafe.Pointer(&a1)))
+	cgocall(asmstdcallAddr, unsafe.Pointer(c))
 	return c.r1, c.r2, c.err
 }
 
 //go:linkname syscall_Syscall12 syscall.Syscall12
 //go:nosplit
 func syscall_Syscall12(fn, nargs, a1, a2, a3, a4, a5, a6, a7, a8, a9, a10, a11, a12 uintptr) (r1, r2, err uintptr) {
-	var c libcall
+	c := &getg().m.syscall
 	c.fn = fn
 	c.n = nargs
-	c.args = uintptr(unsafe.Pointer(&a1))
-	cgocall(asmstdcallAddr, unsafe.Pointer(&c))
+	c.args = uintptr(noescape(unsafe.Pointer(&a1)))
+	cgocall(asmstdcallAddr, unsafe.Pointer(c))
 	return c.r1, c.r2, c.err
 }
 
 //go:linkname syscall_Syscall15 syscall.Syscall15
 //go:nosplit
 func syscall_Syscall15(fn, nargs, a1, a2, a3, a4, a5, a6, a7, a8, a9, a10, a11, a12, a13, a14, a15 uintptr) (r1, r2, err uintptr) {
-	var c libcall
+	c := &getg().m.syscall
 	c.fn = fn
 	c.n = nargs
-	c.args = uintptr(unsafe.Pointer(&a1))
-	cgocall(asmstdcallAddr, unsafe.Pointer(&c))
+	c.args = uintptr(noescape(unsafe.Pointer(&a1)))
+	cgocall(asmstdcallAddr, unsafe.Pointer(c))
 	return c.r1, c.r2, c.err
 }

src/runtime/syscall_windows_test.go

@@ -554,3 +554,86 @@ func TestWERDialogue(t *testing.T) {
 	// Child process should not open WER dialogue, but return immediately instead.
 	cmd.CombinedOutput()
 }
+
+var used byte
+
+func use(buf []byte) {
+	for _, c := range buf {
+		used += c
+	}
+}
+
+func forceStackCopy() (r int) {
+	var f func(int) int
+	f = func(i int) int {
+		var buf [256]byte
+		use(buf[:])
+		if i == 0 {
+			return 0
+		}
+		return i + f(i-1)
+	}
+	r = f(128)
+	return
+}
+
+func TestReturnAfterStackGrowInCallback(t *testing.T) {
+
+	const src = `
+#include <stdint.h>
+#include <windows.h>
+
+typedef uintptr_t __stdcall (*callback)(uintptr_t);
+
+uintptr_t cfunc(callback f, uintptr_t n) {
+   uintptr_t r;
+   r = f(n);
+   SetLastError(333);
+   return r;
+}
+`
+	tmpdir, err := ioutil.TempDir("", "TestReturnAfterStackGrowInCallback")
+	if err != nil {
+		t.Fatal("TempDir failed: ", err)
+	}
+	defer os.RemoveAll(tmpdir)
+
+	srcname := "mydll.c"
+	err = ioutil.WriteFile(filepath.Join(tmpdir, srcname), []byte(src), 0)
+	if err != nil {
+		t.Fatal(err)
+	}
+	outname := "mydll.dll"
+	cmd := exec.Command("gcc", "-shared", "-s", "-Werror", "-o", outname, srcname)
+	cmd.Dir = tmpdir
+	out, err := cmd.CombinedOutput()
+	if err != nil {
+		t.Fatalf("failed to build dll: %v - %v", err, string(out))
+	}
+	dllpath := filepath.Join(tmpdir, outname)
+
+	dll := syscall.MustLoadDLL(dllpath)
+	defer dll.Release()
+
+	proc := dll.MustFindProc("cfunc")
+
+	cb := syscall.NewCallback(func(n uintptr) uintptr {
+		forceStackCopy()
+		return n
+	})
+
+	// Use a new goroutine so that we get a small stack.
+	type result struct {
+		r   uintptr
+		err syscall.Errno
+	}
+	c := make(chan result)
+	go func() {
+		r, _, err := proc.Call(cb, 100)
+		c <- result{r, err.(syscall.Errno)}
+	}()
+	want := result{r: 100, err: 333}
+	if got := <-c; got != want {
+		t.Errorf("got %d want %d", got, want)
+	}
+}