48 lines
1.3 KiB
Go
48 lines
1.3 KiB
Go
// Copyright 2013 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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"unsafe"
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)
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// This file tests the situation where memeq is checking
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// data very near to a page boundary. We want to make sure
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// equal does not read across the boundary and cause a page
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// fault where it shouldn't.
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// This test runs 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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func TestEqualNearPageBoundary(t *testing.T) {
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pagesize := syscall.Getpagesize()
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b := make([]byte, 4*pagesize)
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i := pagesize
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for ; uintptr(unsafe.Pointer(&b[i]))%uintptr(pagesize) != 0; i++ {
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}
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syscall.Mprotect(b[i-pagesize:i], 0)
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syscall.Mprotect(b[i+pagesize:i+2*pagesize], 0)
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defer syscall.Mprotect(b[i-pagesize:i], syscall.PROT_READ|syscall.PROT_WRITE)
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defer syscall.Mprotect(b[i+pagesize:i+2*pagesize], syscall.PROT_READ|syscall.PROT_WRITE)
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// both of these should fault
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//pagesize += int(b[i-1])
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//pagesize += int(b[i+pagesize])
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for j := 0; j < pagesize; j++ {
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b[i+j] = 'A'
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}
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for j := 0; j <= pagesize; j++ {
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Equal(b[i:i+j], b[i+pagesize-j:i+pagesize])
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Equal(b[i+pagesize-j:i+pagesize], b[i:i+j])
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}
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}
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