Check in gVisor.

PiperOrigin-RevId: 194583126
Change-Id: Ica1d8821a90f74e7e745962d71801c598c652463

1 files changed, 182 insertions, 0 deletions

diff --git a/pkg/sentry/fs/proc/proc.go b/pkg/sentry/fs/proc/proc.go
new file mode 100644
index 000000000..459eb7e62
--- /dev/null
+++ b/pkg/sentry/fs/proc/proc.go
@@ -0,0 +1,182 @@
+// 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)
+}