os: add Root.Rename

For #67002

Change-Id: Ifb1042bc5ceaeea64296763319b24634bbcb0bf0
Reviewed-on: https://go-review.googlesource.com/c/go/+/659416
Reviewed-by: Ian Lance Taylor <iant@google.com>
LUCI-TryBot-Result: Go LUCI <golang-scoped@luci-project-accounts.iam.gserviceaccount.com>
Auto-Submit: Damien Neil <dneil@google.com>

1 files changed, 14 insertions, 0 deletions

diff --git a/src/os/root_noopenat.go b/src/os/root_noopenat.go
index f0e1aa5131..4a4aa684af 100644
--- a/src/os/root_noopenat.go
+++ b/src/os/root_noopenat.go
@@ -166,3 +166,17 @@ func rootReadlink(r *Root, name string) (string, error) {
 	}
 	return name, nil
 }
+
+func rootRename(r *Root, oldname, newname string) error {
+	if err := checkPathEscapesLstat(r, oldname); err != nil {
+		return &PathError{Op: "renameat", Path: oldname, Err: err}
+	}
+	if err := checkPathEscapesLstat(r, newname); err != nil {
+		return &PathError{Op: "renameat", Path: newname, Err: err}
+	}
+	err := Rename(joinPath(r.root.name, oldname), joinPath(r.root.name, newname))
+	if err != nil {
+		return &LinkError{"renameat", oldname, newname, underlyingError(err)}
+	}
+	return nil
+}