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// Copyright 2018 Google Inc.
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
// http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.
// Package proc implements a partial in-memory file system for profs.
package proc
import (
"fmt"
"sort"
"strconv"
"gvisor.googlesource.com/gvisor/pkg/sentry/context"
"gvisor.googlesource.com/gvisor/pkg/sentry/fs"
"gvisor.googlesource.com/gvisor/pkg/sentry/fs/proc/device"
"gvisor.googlesource.com/gvisor/pkg/sentry/fs/proc/seqfile"
"gvisor.googlesource.com/gvisor/pkg/sentry/fs/ramfs"
"gvisor.googlesource.com/gvisor/pkg/sentry/kernel"
)
// proc is a root proc node.
type proc struct {
ramfs.Dir
// k is the Kernel containing this proc node.
k *kernel.Kernel
// pidns is the PID namespace of the task that mounted the proc filesystem
// that this node represents.
pidns *kernel.PIDNamespace
}
// New returns the root node of a partial simple procfs.
func New(ctx context.Context, msrc *fs.MountSource) (*fs.Inode, error) {
k := kernel.KernelFromContext(ctx)
if k == nil {
return nil, fmt.Errorf("procfs requires a kernel")
}
pidns := kernel.PIDNamespaceFromContext(ctx)
if pidns == nil {
return nil, fmt.Errorf("procfs requires a PID namespace")
}
p := &proc{k: k, pidns: pidns}
p.InitDir(ctx, map[string]*fs.Inode{
// Note that these are just the static members. There are
// dynamic members populated in Readdir and Lookup below.
"filesystems": seqfile.NewSeqFileInode(ctx, &filesystemsData{}, msrc),
"loadavg": seqfile.NewSeqFileInode(ctx, &loadavgData{}, msrc),
"meminfo": seqfile.NewSeqFileInode(ctx, &meminfoData{k}, msrc),
"mounts": newMountsSymlink(ctx, msrc),
"stat": seqfile.NewSeqFileInode(ctx, &statData{k}, msrc),
"version": seqfile.NewSeqFileInode(ctx, &versionData{k}, msrc),
}, fs.RootOwner, fs.FilePermsFromMode(0555))
p.AddChild(ctx, "cpuinfo", p.newCPUInfo(ctx, msrc))
p.AddChild(ctx, "uptime", p.newUptime(ctx, msrc))
return newFile(p, msrc, fs.SpecialDirectory, nil), nil
}
// self is a magical link.
type self struct {
ramfs.Symlink
pidns *kernel.PIDNamespace
}
// newSelf returns a new "self" node.
func (p *proc) newSelf(ctx context.Context, msrc *fs.MountSource) *fs.Inode {
s := &self{pidns: p.pidns}
s.InitSymlink(ctx, fs.RootOwner, "")
return newFile(s, msrc, fs.Symlink, nil)
}
// Readlink implements fs.InodeOperations.Readlink.
func (s *self) Readlink(ctx context.Context, inode *fs.Inode) (string, error) {
if t := kernel.TaskFromContext(ctx); t != nil {
tgid := s.pidns.IDOfThreadGroup(t.ThreadGroup())
if tgid == 0 {
return "", ramfs.ErrNotFound
}
return strconv.FormatUint(uint64(tgid), 10), nil
}
// Who is reading this link?
return "", ramfs.ErrInvalidOp
}
// Lookup loads an Inode at name into a Dirent.
func (p *proc) Lookup(ctx context.Context, dir *fs.Inode, name string) (*fs.Dirent, error) {
// Is it one of the static ones?
dirent, walkErr := p.Dir.Lookup(ctx, dir, name)
if walkErr == nil {
return dirent, nil
}
// Is it a dynamic element?
nfs := map[string]func() *fs.Inode{
"net": func() *fs.Inode { return p.newNetDir(ctx, dir.MountSource) },
"self": func() *fs.Inode { return p.newSelf(ctx, dir.MountSource) },
"sys": func() *fs.Inode { return p.newSysDir(ctx, dir.MountSource) },
}
if nf, ok := nfs[name]; ok {
return fs.NewDirent(nf(), name), nil
}
// Try to lookup a corresponding task.
tid, err := strconv.ParseUint(name, 10, 64)
if err != nil {
// Ignore the parse error and return the original.
return nil, walkErr
}
// Grab the other task.
otherTask := p.pidns.TaskWithID(kernel.ThreadID(tid))
if otherTask == nil {
// Per above.
return nil, walkErr
}
// Wrap it in a taskDir.
td := newTaskDir(otherTask, dir.MountSource, p.pidns, true)
return fs.NewDirent(td, name), nil
}
// Readdir synthesizes proc contents.
func (p *proc) DeprecatedReaddir(ctx context.Context, dirCtx *fs.DirCtx, offset int) (int, error) {
// Serialize normal contents.
_, err := p.Dir.DeprecatedReaddir(ctx, dirCtx, offset)
if err != nil {
return offset, err
}
m := make(map[string]fs.DentAttr)
var names []string
// Add special files.
m["sys"] = fs.GenericDentAttr(fs.SpecialFile, device.ProcDevice)
names = append(names, "sys")
// Collect tasks.
// Per linux we only include it in directory listings if it's the leader.
// But for whatever crazy reason, you can still walk to the given node.
for _, tg := range p.pidns.ThreadGroups() {
if leader := tg.Leader(); leader != nil {
name := strconv.FormatUint(uint64(tg.ID()), 10)
m[name] = fs.GenericDentAttr(fs.SpecialDirectory, device.ProcDevice)
names = append(names, name)
}
}
if offset >= len(m) {
return offset, nil
}
sort.Strings(names)
names = names[offset:]
for _, name := range names {
if err := dirCtx.DirEmit(name, m[name]); err != nil {
return offset, err
}
offset++
}
return offset, err
}
// newMountsSymlink returns a symlink to "self/mounts"
func newMountsSymlink(ctx context.Context, msrc *fs.MountSource) *fs.Inode {
s := &ramfs.Symlink{}
s.InitSymlink(ctx, fs.RootOwner, "self/mounts")
return newFile(s, msrc, fs.Symlink, nil)
}
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