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