78 lines
2.7 KiB
Go
78 lines
2.7 KiB
Go
// Copyright 2018 Google LLC
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//
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// Licensed under the Apache License, Version 2.0 (the "License");
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// you may not use this file except in compliance with the License.
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// You may obtain a copy of the License at
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//
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// http://www.apache.org/licenses/LICENSE-2.0
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//
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// Unless required by applicable law or agreed to in writing, software
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// distributed under the License is distributed on an "AS IS" BASIS,
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// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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// See the License for the specific language governing permissions and
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// limitations under the License.
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package ramfs
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import (
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"fmt"
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"path"
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"strings"
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"gvisor.googlesource.com/gvisor/pkg/sentry/context"
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"gvisor.googlesource.com/gvisor/pkg/sentry/fs"
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"gvisor.googlesource.com/gvisor/pkg/sentry/fs/anon"
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"gvisor.googlesource.com/gvisor/pkg/sentry/usermem"
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)
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// MakeDirectoryTree constructs a ramfs tree of all directories containing
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// subdirs. Each element of subdir must be a clean path, and cannot be empty or
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// "/".
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//
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// All directories in the created tree will have full (read-write-execute)
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// permissions, but note that file creation inside the directories is not
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// actually supported because ramfs.Dir.CreateOpts == nil. However, these
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// directory trees are normally "underlayed" under another filesystem (possibly
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// the root), and file creation inside these directories in the overlay will be
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// possible if the upper is writeable.
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func MakeDirectoryTree(ctx context.Context, msrc *fs.MountSource, subdirs []string) (*fs.Inode, error) {
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root := emptyDir(ctx, msrc)
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for _, subdir := range subdirs {
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if path.Clean(subdir) != subdir {
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return nil, fmt.Errorf("cannot add subdir at an unclean path: %q", subdir)
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}
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if subdir == "" || subdir == "/" {
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return nil, fmt.Errorf("cannot add subdir at %q", subdir)
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}
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makeSubdir(ctx, msrc, root.InodeOperations.(*Dir), subdir)
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}
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return root, nil
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}
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// makeSubdir installs into root each component of subdir. The final component is
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// a *ramfs.Dir.
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func makeSubdir(ctx context.Context, msrc *fs.MountSource, root *Dir, subdir string) {
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for _, c := range strings.Split(subdir, "/") {
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if len(c) == 0 {
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continue
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}
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child, ok := root.FindChild(c)
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if !ok {
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child = emptyDir(ctx, msrc)
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root.AddChild(ctx, c, child)
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}
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root = child.InodeOperations.(*Dir)
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}
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}
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// emptyDir returns an empty *ramfs.Dir with all permissions granted.
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func emptyDir(ctx context.Context, msrc *fs.MountSource) *fs.Inode {
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dir := NewDir(ctx, make(map[string]*fs.Inode), fs.RootOwner, fs.FilePermsFromMode(0777))
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return fs.NewInode(dir, msrc, fs.StableAttr{
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DeviceID: anon.PseudoDevice.DeviceID(),
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InodeID: anon.PseudoDevice.NextIno(),
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BlockSize: usermem.PageSize,
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Type: fs.Directory,
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})
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}
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