1// run 2 3// Copyright 2011 The Go Authors. All rights reserved. 4// Use of this source code is governed by a BSD-style 5// license that can be found in the LICENSE file. 6 7// Test that the implementation catches nil ptr indirection 8// in a large address space. 9 10package main 11 12import "unsafe" 13 14// Having a big address space means that indexing 15// at a 256 MB offset from a nil pointer might not 16// cause a memory access fault. This test checks 17// that Go is doing the correct explicit checks to catch 18// these nil pointer accesses, not just relying on the hardware. 19var dummy [256 << 20]byte // give us a big address space 20 21func main() { 22 // the test only tests what we intend to test 23 // if dummy starts in the first 256 MB of memory. 24 // otherwise there might not be anything mapped 25 // at the address that might be accidentally 26 // dereferenced below. 27 if uintptr(unsafe.Pointer(&dummy)) > 256<<20 { 28 panic("dummy too far out") 29 } 30 31 shouldPanic(p1) 32 shouldPanic(p2) 33 shouldPanic(p3) 34 shouldPanic(p4) 35 shouldPanic(p5) 36 shouldPanic(p6) 37 shouldPanic(p7) 38 shouldPanic(p8) 39 shouldPanic(p9) 40 shouldPanic(p10) 41} 42 43func shouldPanic(f func()) { 44 defer func() { 45 if recover() == nil { 46 panic("memory reference did not panic") 47 } 48 }() 49 f() 50} 51 52func p1() { 53 // Array index. 54 var p *[1 << 30]byte = nil 55 println(p[256<<20]) // very likely to be inside dummy, but should panic 56} 57 58var xb byte 59 60func p2() { 61 var p *[1 << 30]byte = nil 62 xb = 123 63 64 // Array index. 65 println(p[uintptr(unsafe.Pointer(&xb))]) // should panic 66} 67 68func p3() { 69 // Array to slice. 70 var p *[1 << 30]byte = nil 71 var x []byte = p[0:] // should panic 72 _ = x 73} 74 75var q *[1 << 30]byte 76 77func p4() { 78 // Array to slice. 79 var x []byte 80 var y = &x 81 *y = q[0:] // should crash (uses arraytoslice runtime routine) 82} 83 84func fb([]byte) { 85 panic("unreachable") 86} 87 88func p5() { 89 // Array to slice. 90 var p *[1 << 30]byte = nil 91 fb(p[0:]) // should crash 92} 93 94func p6() { 95 // Array to slice. 96 var p *[1 << 30]byte = nil 97 var _ []byte = p[10 : len(p)-10] // should crash 98} 99 100type T struct { 101 x [256 << 20]byte 102 i int 103} 104 105func f() *T { 106 return nil 107} 108 109var y *T 110var x = &y 111 112func p7() { 113 // Struct field access with large offset. 114 println(f().i) // should crash 115} 116 117func p8() { 118 // Struct field access with large offset. 119 println((*x).i) // should crash 120} 121 122func p9() { 123 // Struct field access with large offset. 124 var t *T 125 println(&t.i) // should crash 126} 127 128func p10() { 129 // Struct field access with large offset. 130 var t *T 131 println(t.i) // should crash 132} 133