Support FreeBSD on pkg/system/utimes_*.go

Implement system.LUtimesNano and system.UtimesNano. The latter might be
removed in future because it's basically same as os.Chtimes. That's why
the test is mainly focusing LUtimesNano.

Docker-DCO-1.1-Signed-off-by: Kato Kazuyoshi <kato.kazuyoshi@gmail.com> (github: kzys)

system/utimes_freebsd.go

@@ -0,0 +1,24 @@
+package system
+
+import (
+	"syscall"
+	"unsafe"
+)
+
+func LUtimesNano(path string, ts []syscall.Timespec) error {
+	var _path *byte
+	_path, err := syscall.BytePtrFromString(path)
+	if err != nil {
+		return err
+	}
+
+	if _, _, err := syscall.Syscall(syscall.SYS_LUTIMES, uintptr(unsafe.Pointer(_path)), uintptr(unsafe.Pointer(&ts[0])), 0); err != 0 && err != syscall.ENOSYS {
+		return err
+	}
+
+	return nil
+}
+
+func UtimesNano(path string, ts []syscall.Timespec) error {
+	return syscall.UtimesNano(path, ts)
+}

system/utimes_test.go

@@ -0,0 +1,64 @@
+package system
+
+import (
+	"io/ioutil"
+	"os"
+	"path/filepath"
+	"syscall"
+	"testing"
+)
+
+func prepareFiles(t *testing.T) (string, string, string) {
+	dir, err := ioutil.TempDir("", "docker-system-test")
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	file := filepath.Join(dir, "exist")
+	if err := ioutil.WriteFile(file, []byte("hello"), 0644); err != nil {
+		t.Fatal(err)
+	}
+
+	invalid := filepath.Join(dir, "doesnt-exist")
+
+	symlink := filepath.Join(dir, "symlink")
+	if err := os.Symlink(file, symlink); err != nil {
+		t.Fatal(err)
+	}
+
+	return file, invalid, symlink
+}
+
+func TestLUtimesNano(t *testing.T) {
+	file, invalid, symlink := prepareFiles(t)
+
+	before, err := os.Stat(file)
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	ts := []syscall.Timespec{{0, 0}, {0, 0}}
+	if err := LUtimesNano(symlink, ts); err != nil {
+		t.Fatal(err)
+	}
+
+	symlinkInfo, err := os.Lstat(symlink)
+	if err != nil {
+		t.Fatal(err)
+	}
+	if before.ModTime().Unix() == symlinkInfo.ModTime().Unix() {
+		t.Fatal("The modification time of the symlink should be different")
+	}
+
+	fileInfo, err := os.Stat(file)
+	if err != nil {
+		t.Fatal(err)
+	}
+	if before.ModTime().Unix() != fileInfo.ModTime().Unix() {
+		t.Fatal("The modification time of the file should be same")
+	}
+
+	if err := LUtimesNano(invalid, ts); err == nil {
+		t.Fatal("Doesn't return an error on a non-existing file")
+	}
+}

system/utimes_unsupported.go

@@ -1,4 +1,4 @@
-// +build !linux
+// +build !linux,!freebsd
 
 package system