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// Copyright 2015 syzkaller project authors. All rights reserved.
// Use of this source code is governed by Apache 2 LICENSE that can be found in the LICENSE file.
package osutil
import (
"fmt"
"io"
"io/ioutil"
"os"
"path/filepath"
"strconv"
"syscall"
)
// CopyFile atomically copies oldFile to newFile preserving permissions and modification time.
func CopyFile(oldFile, newFile string) error {
oldf, err := os.Open(oldFile)
if err != nil {
return err
}
defer oldf.Close()
stat, err := oldf.Stat()
if err != nil {
return err
}
tmpFile := newFile + ".tmp"
newf, err := os.OpenFile(tmpFile, os.O_WRONLY|os.O_CREATE|os.O_TRUNC, stat.Mode()&os.ModePerm)
if err != nil {
return err
}
defer newf.Close()
_, err = io.Copy(newf, oldf)
if err != nil {
return err
}
if err := newf.Close(); err != nil {
return err
}
if err := os.Chtimes(tmpFile, stat.ModTime(), stat.ModTime()); err != nil {
return err
}
return os.Rename(tmpFile, newFile)
}
// WriteTempFile writes data to a temp file and returns its name.
func WriteTempFile(data []byte) (string, error) {
f, err := ioutil.TempFile("", "syzkaller")
if err != nil {
return "", fmt.Errorf("failed to create a temp file: %v", err)
}
if _, err := f.Write(data); err != nil {
f.Close()
os.Remove(f.Name())
return "", fmt.Errorf("failed to write a temp file: %v", err)
}
f.Close()
return f.Name(), nil
}
// ProcessTempDir creates a new temp dir in where and returns its path and an unique index.
// It also cleans up old, unused temp dirs after dead processes.
func ProcessTempDir(where string) (string, error) {
lk := filepath.Join(where, "instance-lock")
lkf, err := syscall.Open(lk, syscall.O_RDWR|syscall.O_CREAT, DefaultFilePerm)
if err != nil {
return "", err
}
defer syscall.Close(lkf)
if err := syscall.Flock(lkf, syscall.LOCK_EX); err != nil {
return "", err
}
defer syscall.Flock(lkf, syscall.LOCK_UN)
for i := 0; i < 1e3; i++ {
path := filepath.Join(where, fmt.Sprintf("instance-%v", i))
pidfile := filepath.Join(path, ".pid")
err := os.Mkdir(path, DefaultDirPerm)
if os.IsExist(err) {
// Try to clean up.
data, err := ioutil.ReadFile(pidfile)
if err == nil && len(data) > 0 {
pid, err := strconv.Atoi(string(data))
if err == nil && pid > 1 {
if err := syscall.Kill(pid, 0); err == syscall.ESRCH {
if os.Remove(pidfile) == nil {
if os.RemoveAll(path) == nil {
i--
continue
}
}
}
}
}
// If err != nil, assume that the pid file is not created yet.
continue
}
if err != nil {
return "", err
}
if err := WriteFile(pidfile, []byte(strconv.Itoa(syscall.Getpid()))); err != nil {
return "", err
}
return path, nil
}
return "", fmt.Errorf("too many live instances")
}
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