runtime: adjust frame pointer on stack copy on ARM64

Frame pointer is enabled on ARM64. When copying stacks, the
saved frame pointers need to be adjusted.

Updates #39524, #40044.
Fixes #58432.

Change-Id: I73651fdfd1a6cccae26a5ce02e7e86f6c2fb9bf7
Reviewed-on: https://go-review.googlesource.com/c/go/+/241158
Reviewed-by: Felix Geisendörfer <felix.geisendoerfer@datadoghq.com>
Run-TryBot: Cherry Mui <cherryyz@google.com>
Reviewed-by: Michael Knyszek <mknyszek@google.com>
TryBot-Result: Gopher Robot <gobot@golang.org>

src/runtime/stack.go

@@ -537,7 +537,7 @@ var ptrnames = []string{
 // +------------------+ <- frame->argp
 // |  return address  |
 // +------------------+
-// |  caller's BP (*) | (*) if framepointer_enabled && varp < sp
+// |  caller's BP (*) | (*) if framepointer_enabled && varp > sp
 // +------------------+ <- frame->varp
 // |     locals       |
 // +------------------+
@@ -549,6 +549,8 @@ var ptrnames = []string{
 // | args from caller |
 // +------------------+ <- frame->argp
 // | caller's retaddr |
+// +------------------+
+// |  caller's FP (*) | (*) on ARM64, if framepointer_enabled && varp > sp
 // +------------------+ <- frame->varp
 // |     locals       |
 // +------------------+
@@ -556,6 +558,9 @@ var ptrnames = []string{
 // +------------------+
 // |  return address  |
 // +------------------+ <- frame->sp
+//
+// varp > sp means that the function has a frame;
+// varp == sp means frameless function.
 
 type adjustinfo struct {
 	old   stack
@@ -673,9 +678,8 @@ func adjustframe(frame *stkframe, adjinfo *adjustinfo) {
 		adjustpointers(unsafe.Pointer(frame.varp-size), &locals, adjinfo, f)
 	}
 
-	// Adjust saved base pointer if there is one.
+	// Adjust saved frame pointer if there is one.
-	// TODO what about arm64 frame pointer adjustment?
+	if (goarch.ArchFamily == goarch.AMD64 || goarch.ArchFamily == goarch.ARM64) && frame.argp-frame.varp == 2*goarch.PtrSize {
-	if goarch.ArchFamily == goarch.AMD64 && frame.argp-frame.varp == 2*goarch.PtrSize {
 		if stackDebug >= 3 {
 			print("      saved bp\n")
 		}
@@ -689,6 +693,10 @@ func adjustframe(frame *stkframe, adjinfo *adjustinfo) {
 				throw("bad frame pointer")
 			}
 		}
+		// On AMD64, this is the caller's frame pointer saved in the current
+		// frame.
+		// On ARM64, this is the frame pointer of the caller's caller saved
+		// by the caller in its frame (one word below its SP).
 		adjustpointer(adjinfo, unsafe.Pointer(frame.varp))
 	}
 
@@ -750,7 +758,17 @@ func adjustctxt(gp *g, adjinfo *adjustinfo) {
 			throw("bad top frame pointer")
 		}
 	}
+	oldfp := gp.sched.bp
 	adjustpointer(adjinfo, unsafe.Pointer(&gp.sched.bp))
+	if GOARCH == "arm64" {
+		// On ARM64, the frame pointer is saved one word *below* the SP,
+		// which is not copied or adjusted in any frame. Do it explicitly
+		// here.
+		if oldfp == gp.sched.sp-goarch.PtrSize {
+			memmove(unsafe.Pointer(gp.sched.bp), unsafe.Pointer(oldfp), goarch.PtrSize)
+			adjustpointer(adjinfo, unsafe.Pointer(gp.sched.bp))
+		}
+	}
 }
 
 func adjustdefers(gp *g, adjinfo *adjustinfo) {

src/runtime/stack_test.go

@@ -927,3 +927,15 @@ func deferHeapAndStack(n int) (r int) {
 
 // Pass a value to escapeMe to force it to escape.
 var escapeMe = func(x any) {}
+
+func TestFramePointerAdjust(t *testing.T) {
+	switch GOARCH {
+	case "amd64", "arm64":
+	default:
+		t.Skipf("frame pointer is not supported on %s", GOARCH)
+	}
+	output := runTestProg(t, "testprog", "FramePointerAdjust")
+	if output != "" {
+		t.Errorf("output:\n%s\n\nwant no output", output)
+	}
+}

src/runtime/testdata/testprog/framepointer.go

@@ -0,0 +1,44 @@
+// Copyright 2023 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+//go:build amd64 || arm64
+
+package main
+
+import "unsafe"
+
+func init() {
+	register("FramePointerAdjust", FramePointerAdjust)
+}
+
+func FramePointerAdjust() { framePointerAdjust1(0) }
+
+//go:noinline
+func framePointerAdjust1(x int) {
+	argp := uintptr(unsafe.Pointer(&x))
+	fp := *getFP()
+	if !(argp-0x100 <= fp && fp <= argp+0x100) {
+		print("saved FP=", fp, " &x=", argp, "\n")
+		panic("FAIL")
+	}
+
+	// grow the stack
+	grow(10000)
+
+	// check again
+	argp = uintptr(unsafe.Pointer(&x))
+	fp = *getFP()
+	if !(argp-0x100 <= fp && fp <= argp+0x100) {
+		print("saved FP=", fp, " &x=", argp, "\n")
+		panic("FAIL")
+	}
+}
+
+func grow(n int) {
+	if n > 0 {
+		grow(n - 1)
+	}
+}
+
+func getFP() *uintptr

src/runtime/testdata/testprog/framepointer_amd64.s

@@ -0,0 +1,9 @@
+// Copyright 2023 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+#include "textflag.h"
+
+TEXT	·getFP(SB), NOSPLIT|NOFRAME, $0-8
+	MOVQ	BP, ret+0(FP)
+	RET

src/runtime/testdata/testprog/framepointer_arm64.s

@@ -0,0 +1,9 @@
+// Copyright 2023 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+#include "textflag.h"
+
+TEXT	·getFP(SB), NOSPLIT|NOFRAME, $0-8
+	MOVD	R29, ret+0(FP)
+	RET