panic_test.go

     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  
     9  package debug_test
    10  
    11  import (
    12  	"runtime"
    13  	"runtime/debug"
    14  	"syscall"
    15  	"testing"
    16  	"unsafe"
    17  )
    18  
    19  func 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
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