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- // 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.
- //
- //go: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()
- q := dangerousSlice(t)
- if len(q) > 64 {
- // Only worry about when we're near the end of a page.
- q = q[len(q)-64:]
- }
- 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
- }
- // Test differing alignments and sizes of q which always end on a page boundary.
- q[len(q)-1] = 1 // difference is only found on the last byte
- for j := 0; j < len(q); j++ {
- 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[len(q)-1] = 0
- }
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