// Copyright 2017 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.
|
//
|
// +build linux
|
|
package bytes_test
|
|
import (
|
. "bytes"
|
"syscall"
|
"testing"
|
)
|
|
// This file tests the situation where byte operations are checking
|
// data very near to a page boundary. We want to make sure those
|
// operations do not read across the boundary and cause a page
|
// fault where they shouldn't.
|
|
// These tests run only on linux. The code being tested is
|
// not OS-specific, so it does not need to be tested on all
|
// operating systems.
|
|
// dangerousSlice returns a slice which is immediately
|
// preceded and followed by a faulting page.
|
func dangerousSlice(t *testing.T) []byte {
|
pagesize := syscall.Getpagesize()
|
b, err := syscall.Mmap(0, 0, 3*pagesize, syscall.PROT_READ|syscall.PROT_WRITE, syscall.MAP_ANONYMOUS|syscall.MAP_PRIVATE)
|
if err != nil {
|
t.Fatalf("mmap failed %s", err)
|
}
|
err = syscall.Mprotect(b[:pagesize], syscall.PROT_NONE)
|
if err != nil {
|
t.Fatalf("mprotect low failed %s\n", err)
|
}
|
err = syscall.Mprotect(b[2*pagesize:], syscall.PROT_NONE)
|
if err != nil {
|
t.Fatalf("mprotect high failed %s\n", err)
|
}
|
return b[pagesize : 2*pagesize]
|
}
|
|
func TestEqualNearPageBoundary(t *testing.T) {
|
t.Parallel()
|
b := dangerousSlice(t)
|
for i := range b {
|
b[i] = 'A'
|
}
|
for i := 0; i <= len(b); i++ {
|
Equal(b[:i], b[len(b)-i:])
|
Equal(b[len(b)-i:], b[:i])
|
}
|
}
|
|
func TestIndexByteNearPageBoundary(t *testing.T) {
|
t.Parallel()
|
b := dangerousSlice(t)
|
for i := range b {
|
idx := IndexByte(b[i:], 1)
|
if idx != -1 {
|
t.Fatalf("IndexByte(b[%d:])=%d, want -1\n", i, idx)
|
}
|
}
|
}
|
|
func TestIndexNearPageBoundary(t *testing.T) {
|
t.Parallel()
|
var q [64]byte
|
b := dangerousSlice(t)
|
if len(b) > 256 {
|
// Only worry about when we're near the end of a page.
|
b = b[len(b)-256:]
|
}
|
for j := 1; j < len(q); j++ {
|
q[j-1] = 1 // difference is only found on the last byte
|
for i := range b {
|
idx := Index(b[i:], q[:j])
|
if idx != -1 {
|
t.Fatalf("Index(b[%d:], q[:%d])=%d, want -1\n", i, j, idx)
|
}
|
}
|
q[j-1] = 0
|
}
|
}
|
