1// Copyright 2020 The Go Authors. All rights reserved.
2// Use of this source code is governed by a BSD-style
3// license that can be found in the LICENSE file.
4
5//go:build aix || darwin || dragonfly || freebsd || linux || netbsd || openbsd
6
7// TODO: test on Windows?
8
9package debug_test
10
11import (
12	"runtime"
13	"runtime/debug"
14	"syscall"
15	"testing"
16	"unsafe"
17)
18
19func TestPanicOnFault(t *testing.T) {
20	if runtime.GOARCH == "s390x" {
21		t.Skip("s390x fault addresses are missing the low order bits")
22	}
23	if runtime.GOOS == "ios" {
24		t.Skip("iOS doesn't provide fault addresses")
25	}
26	if runtime.GOOS == "netbsd" && runtime.GOARCH == "arm" {
27		t.Skip("netbsd-arm doesn't provide fault address (golang.org/issue/45026)")
28	}
29	m, err := syscall.Mmap(-1, 0, 0x1000, syscall.PROT_READ /* Note: no PROT_WRITE */, syscall.MAP_SHARED|syscall.MAP_ANON)
30	if err != nil {
31		t.Fatalf("can't map anonymous memory: %s", err)
32	}
33	defer syscall.Munmap(m)
34	old := debug.SetPanicOnFault(true)
35	defer debug.SetPanicOnFault(old)
36	const lowBits = 0x3e7
37	defer func() {
38		r := recover()
39		if r == nil {
40			t.Fatalf("write did not fault")
41		}
42		type addressable interface {
43			Addr() uintptr
44		}
45		a, ok := r.(addressable)
46		if !ok {
47			t.Fatalf("fault does not contain address")
48		}
49		want := uintptr(unsafe.Pointer(&m[lowBits]))
50		got := a.Addr()
51		if got != want {
52			t.Fatalf("fault address %x, want %x", got, want)
53		}
54	}()
55	m[lowBits] = 1 // will fault
56}
57