1 files changed, 107 insertions, 0 deletions
diff --git a/pkg/osutil/fileutil.go b/pkg/osutil/fileutil.go
new file mode 100644
index 000000000..801453326
--- /dev/null
+++ b/pkg/osutil/fileutil.go
@@ -0,0 +1,107 @@
+// 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")
+}