1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
|
// run
// +build amd64
// +build linux darwin
// Copyright 2016 The Go Authors. All rights reserved.
// Use of this source code is governed by a BSD-style
// license that can be found in the LICENSE file.
package main
import (
"fmt"
"syscall"
)
// Use global variables so the compiler
// doesn't know that they are constants.
var p = syscall.Getpagesize()
var zero = 0
var one = 1
func main() {
// Allocate 2 pages of memory.
b, err := syscall.Mmap(-1, 0, 2*p, syscall.PROT_READ|syscall.PROT_WRITE, syscall.MAP_ANON|syscall.MAP_PRIVATE)
if err != nil {
panic(err)
}
// Mark the second page as faulting.
err = syscall.Mprotect(b[p:], syscall.PROT_NONE)
if err != nil {
panic(err)
}
// Get a slice pointing to the last byte of the good page.
x := b[p-one : p]
test16(x)
test16i(x, 0)
test32(x)
test32i(x, 0)
test64(x)
test64i(x, 0)
}
func test16(x []byte) uint16 {
defer func() {
r := recover()
if r == nil {
panic("no fault or bounds check failure happened")
}
s := fmt.Sprintf("%s", r)
if s != "runtime error: index out of range [1] with length 1" {
panic("bad panic: " + s)
}
}()
// Try to read 2 bytes from x.
return uint16(x[0]) | uint16(x[1])<<8
// We expect to get an "index out of range" error from x[1].
// If we promote the first load to a 2-byte load, it will segfault, which we don't want.
}
func test16i(x []byte, i int) uint16 {
defer func() {
r := recover()
if r == nil {
panic("no fault or bounds check failure happened")
}
s := fmt.Sprintf("%s", r)
if s != "runtime error: index out of range [1] with length 1" {
panic("bad panic: " + s)
}
}()
return uint16(x[i]) | uint16(x[i+1])<<8
}
func test32(x []byte) uint32 {
defer func() {
r := recover()
if r == nil {
panic("no fault or bounds check failure happened")
}
s := fmt.Sprintf("%s", r)
if s != "runtime error: index out of range [1] with length 1" {
panic("bad panic: " + s)
}
}()
return uint32(x[0]) | uint32(x[1])<<8 | uint32(x[2])<<16 | uint32(x[3])<<24
}
func test32i(x []byte, i int) uint32 {
defer func() {
r := recover()
if r == nil {
panic("no fault or bounds check failure happened")
}
s := fmt.Sprintf("%s", r)
if s != "runtime error: index out of range [1] with length 1" {
panic("bad panic: " + s)
}
}()
return uint32(x[i]) | uint32(x[i+1])<<8 | uint32(x[i+2])<<16 | uint32(x[i+3])<<24
}
func test64(x []byte) uint64 {
defer func() {
r := recover()
if r == nil {
panic("no fault or bounds check failure happened")
}
s := fmt.Sprintf("%s", r)
if s != "runtime error: index out of range [1] with length 1" {
panic("bad panic: " + s)
}
}()
return uint64(x[0]) | uint64(x[1])<<8 | uint64(x[2])<<16 | uint64(x[3])<<24 |
uint64(x[4])<<32 | uint64(x[5])<<40 | uint64(x[6])<<48 | uint64(x[7])<<56
}
func test64i(x []byte, i int) uint64 {
defer func() {
r := recover()
if r == nil {
panic("no fault or bounds check failure happened")
}
s := fmt.Sprintf("%s", r)
if s != "runtime error: index out of range [1] with length 1" {
panic("bad panic: " + s)
}
}()
return uint64(x[i+0]) | uint64(x[i+1])<<8 | uint64(x[i+2])<<16 | uint64(x[i+3])<<24 |
uint64(x[i+4])<<32 | uint64(x[i+5])<<40 | uint64(x[i+6])<<48 | uint64(x[i+7])<<56
}
|
