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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