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