183 lines
5.5 KiB
Go
183 lines
5.5 KiB
Go
// Copyright 2018 Google Inc.
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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 proc implements a partial in-memory file system for profs.
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package proc
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import (
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"fmt"
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"sort"
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"strconv"
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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/proc/device"
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"gvisor.googlesource.com/gvisor/pkg/sentry/fs/proc/seqfile"
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"gvisor.googlesource.com/gvisor/pkg/sentry/fs/ramfs"
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"gvisor.googlesource.com/gvisor/pkg/sentry/kernel"
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)
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// proc is a root proc node.
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type proc struct {
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ramfs.Dir
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// k is the Kernel containing this proc node.
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k *kernel.Kernel
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// pidns is the PID namespace of the task that mounted the proc filesystem
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// that this node represents.
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pidns *kernel.PIDNamespace
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}
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// New returns the root node of a partial simple procfs.
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func New(ctx context.Context, msrc *fs.MountSource) (*fs.Inode, error) {
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k := kernel.KernelFromContext(ctx)
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if k == nil {
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return nil, fmt.Errorf("procfs requires a kernel")
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}
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pidns := kernel.PIDNamespaceFromContext(ctx)
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if pidns == nil {
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return nil, fmt.Errorf("procfs requires a PID namespace")
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}
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p := &proc{k: k, pidns: pidns}
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p.InitDir(ctx, map[string]*fs.Inode{
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// Note that these are just the static members. There are
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// dynamic members populated in Readdir and Lookup below.
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"filesystems": seqfile.NewSeqFileInode(ctx, &filesystemsData{}, msrc),
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"loadavg": seqfile.NewSeqFileInode(ctx, &loadavgData{}, msrc),
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"meminfo": seqfile.NewSeqFileInode(ctx, &meminfoData{k}, msrc),
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"mounts": newMountsSymlink(ctx, msrc),
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"stat": seqfile.NewSeqFileInode(ctx, &statData{k}, msrc),
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"version": seqfile.NewSeqFileInode(ctx, &versionData{k}, msrc),
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}, fs.RootOwner, fs.FilePermsFromMode(0555))
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p.AddChild(ctx, "cpuinfo", p.newCPUInfo(ctx, msrc))
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p.AddChild(ctx, "uptime", p.newUptime(ctx, msrc))
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return newFile(p, msrc, fs.SpecialDirectory, nil), nil
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}
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// self is a magical link.
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type self struct {
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ramfs.Symlink
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pidns *kernel.PIDNamespace
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}
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// newSelf returns a new "self" node.
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func (p *proc) newSelf(ctx context.Context, msrc *fs.MountSource) *fs.Inode {
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s := &self{pidns: p.pidns}
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s.InitSymlink(ctx, fs.RootOwner, "")
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return newFile(s, msrc, fs.Symlink, nil)
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}
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// Readlink implements fs.InodeOperations.Readlink.
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func (s *self) Readlink(ctx context.Context, inode *fs.Inode) (string, error) {
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if t := kernel.TaskFromContext(ctx); t != nil {
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tgid := s.pidns.IDOfThreadGroup(t.ThreadGroup())
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if tgid == 0 {
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return "", ramfs.ErrNotFound
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}
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return strconv.FormatUint(uint64(tgid), 10), nil
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}
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// Who is reading this link?
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return "", ramfs.ErrInvalidOp
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}
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// Lookup loads an Inode at name into a Dirent.
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func (p *proc) Lookup(ctx context.Context, dir *fs.Inode, name string) (*fs.Dirent, error) {
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// Is it one of the static ones?
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dirent, walkErr := p.Dir.Lookup(ctx, dir, name)
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if walkErr == nil {
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return dirent, nil
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}
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// Is it a dynamic element?
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nfs := map[string]func() *fs.Inode{
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"net": func() *fs.Inode { return p.newNetDir(ctx, dir.MountSource) },
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"self": func() *fs.Inode { return p.newSelf(ctx, dir.MountSource) },
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"sys": func() *fs.Inode { return p.newSysDir(ctx, dir.MountSource) },
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}
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if nf, ok := nfs[name]; ok {
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return fs.NewDirent(nf(), name), nil
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}
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// Try to lookup a corresponding task.
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tid, err := strconv.ParseUint(name, 10, 64)
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if err != nil {
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// Ignore the parse error and return the original.
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return nil, walkErr
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}
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// Grab the other task.
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otherTask := p.pidns.TaskWithID(kernel.ThreadID(tid))
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if otherTask == nil {
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// Per above.
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return nil, walkErr
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}
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// Wrap it in a taskDir.
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td := newTaskDir(otherTask, dir.MountSource, p.pidns, true)
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return fs.NewDirent(td, name), nil
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}
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// Readdir synthesizes proc contents.
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func (p *proc) DeprecatedReaddir(ctx context.Context, dirCtx *fs.DirCtx, offset int) (int, error) {
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// Serialize normal contents.
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_, err := p.Dir.DeprecatedReaddir(ctx, dirCtx, offset)
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if err != nil {
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return offset, err
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}
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m := make(map[string]fs.DentAttr)
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var names []string
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// Add special files.
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m["sys"] = fs.GenericDentAttr(fs.SpecialFile, device.ProcDevice)
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names = append(names, "sys")
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// Collect tasks.
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// Per linux we only include it in directory listings if it's the leader.
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// But for whatever crazy reason, you can still walk to the given node.
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for _, tg := range p.pidns.ThreadGroups() {
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if leader := tg.Leader(); leader != nil {
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name := strconv.FormatUint(uint64(tg.ID()), 10)
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m[name] = fs.GenericDentAttr(fs.SpecialDirectory, device.ProcDevice)
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names = append(names, name)
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}
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}
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if offset >= len(m) {
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return offset, nil
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}
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sort.Strings(names)
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names = names[offset:]
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for _, name := range names {
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if err := dirCtx.DirEmit(name, m[name]); err != nil {
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return offset, err
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}
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offset++
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}
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return offset, err
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}
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// newMountsSymlink returns a symlink to "self/mounts"
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func newMountsSymlink(ctx context.Context, msrc *fs.MountSource) *fs.Inode {
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s := &ramfs.Symlink{}
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s.InitSymlink(ctx, fs.RootOwner, "self/mounts")
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return newFile(s, msrc, fs.Symlink, nil)
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}
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