mirror of
https://github.com/golang/go
synced 2024-11-15 01:40:25 -07:00
e858a6b9f0
Change-Id: I30e9b938bb19ed4e674c3ea4a1cd389b9c4f0b88 Reviewed-on: https://go-review.googlesource.com/86875 Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org> Run-TryBot: Brad Fitzpatrick <bradfitz@golang.org> TryBot-Result: Gobot Gobot <gobot@golang.org>
74 lines
2.2 KiB
Go
74 lines
2.2 KiB
Go
// +build linux darwin
|
|
// run
|
|
|
|
// Copyright 2015 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.
|
|
|
|
// Test that if a slice access causes a fault, a deferred func
|
|
// sees the most recent value of the variables it accesses.
|
|
// This is true today; the role of the test is to ensure it stays true.
|
|
//
|
|
// In the test, memcopy is the function that will fault, during dst[i] = src[i].
|
|
// The deferred func recovers from the error and returns, making memcopy
|
|
// return the current value of n. If n is not being flushed to memory
|
|
// after each modification, the result will be a stale value of n.
|
|
//
|
|
// The test is set up by mmapping a 64 kB block of memory and then
|
|
// unmapping a 16 kB hole in the middle of it. Running memcopy
|
|
// on the resulting slice will fault when it reaches the hole.
|
|
|
|
package main
|
|
|
|
import (
|
|
"log"
|
|
"runtime/debug"
|
|
"syscall"
|
|
"unsafe"
|
|
)
|
|
|
|
func memcopy(dst, src []byte) (n int, err error) {
|
|
defer func() {
|
|
err = recover().(error)
|
|
}()
|
|
|
|
for i := 0; i < len(dst) && i < len(src); i++ {
|
|
dst[i] = src[i]
|
|
n++
|
|
}
|
|
return
|
|
}
|
|
|
|
func main() {
|
|
// Turn the eventual fault into a panic, not a program crash,
|
|
// so that memcopy can recover.
|
|
debug.SetPanicOnFault(true)
|
|
|
|
size := syscall.Getpagesize()
|
|
|
|
// Map 16 pages of data with a 4-page hole in the middle.
|
|
data, err := syscall.Mmap(-1, 0, 16*size, syscall.PROT_READ|syscall.PROT_WRITE, syscall.MAP_ANON|syscall.MAP_PRIVATE)
|
|
if err != nil {
|
|
log.Fatalf("mmap: %v", err)
|
|
}
|
|
|
|
other := make([]byte, 16*size)
|
|
|
|
// Note: Cannot call syscall.Munmap, because Munmap checks
|
|
// that you are unmapping a whole region returned by Mmap.
|
|
// We are trying to unmap just a hole in the middle.
|
|
if _, _, err := syscall.Syscall(syscall.SYS_MUNMAP, uintptr(unsafe.Pointer(&data[8*size])), uintptr(4*size), 0); err != 0 {
|
|
log.Fatalf("munmap: %v", err)
|
|
}
|
|
|
|
// Check that memcopy returns the actual amount copied
|
|
// before the fault (8*size - 5, the offset we skip in the argument).
|
|
n, err := memcopy(data[5:], other)
|
|
if err == nil {
|
|
log.Fatal("no error from memcopy across memory hole")
|
|
}
|
|
if n != 8*size-5 {
|
|
log.Fatalf("memcopy returned %d, want %d", n, 8*size-5)
|
|
}
|
|
}
|