panic_test.go

Documentation: runtime/debug

     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  // +build aix darwin dragonfly freebsd linux netbsd openbsd
     7  
     8  // TODO: test on Windows?
     9  
    10  package debug_test
    11  
    12  import (
    13  	"runtime"
    14  	"runtime/debug"
    15  	"syscall"
    16  	"testing"
    17  	"unsafe"
    18  )
    19  
    20  func TestPanicOnFault(t *testing.T) {
    21  	if runtime.GOARCH == "s390x" {
    22  		t.Skip("s390x fault addresses are missing the low order bits")
    23  	}
    24  	if runtime.GOOS == "ios" {
    25  		t.Skip("iOS doesn't provide fault addresses")
    26  	}
    27  	if runtime.GOOS == "netbsd" && runtime.GOARCH == "arm" {
    28  		t.Skip("netbsd-arm doesn't provide fault address (golang.org/issue/45026)")
    29  	}
    30  	m, err := syscall.Mmap(-1, 0, 0x1000, syscall.PROT_READ /* Note: no PROT_WRITE */, syscall.MAP_SHARED|syscall.MAP_ANON)
    31  	if err != nil {
    32  		t.Fatalf("can't map anonymous memory: %s", err)
    33  	}
    34  	defer syscall.Munmap(m)
    35  	old := debug.SetPanicOnFault(true)
    36  	defer debug.SetPanicOnFault(old)
    37  	const lowBits = 0x3e7
    38  	defer func() {
    39  		r := recover()
    40  		if r == nil {
    41  			t.Fatalf("write did not fault")
    42  		}
    43  		type addressable interface {
    44  			Addr() uintptr
    45  		}
    46  		a, ok := r.(addressable)
    47  		if !ok {
    48  			t.Fatalf("fault does not contain address")
    49  		}
    50  		want := uintptr(unsafe.Pointer(&m[lowBits]))
    51  		got := a.Addr()
    52  		if got != want {
    53  			t.Fatalf("fault address %x, want %x", got, want)
    54  		}
    55  	}()
    56  	m[lowBits] = 1 // will fault
    57  }
    58
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