1 files changed, 128 insertions, 0 deletions
diff --git a/pkg/sentry/fsimpl/proc/subtasks.go b/pkg/sentry/fsimpl/proc/subtasks.go
new file mode 100644
index 000000000..91eded415
--- /dev/null
+++ b/pkg/sentry/fsimpl/proc/subtasks.go
@@ -0,0 +1,128 @@
+// Copyright 2019 The gVisor Authors.
+//
+// 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
+
+import (
+	"sort"
+	"strconv"
+
+	"gvisor.dev/gvisor/pkg/abi/linux"
+	"gvisor.dev/gvisor/pkg/sentry/context"
+	"gvisor.dev/gvisor/pkg/sentry/fsimpl/kernfs"
+	"gvisor.dev/gvisor/pkg/sentry/kernel"
+	"gvisor.dev/gvisor/pkg/sentry/vfs"
+	"gvisor.dev/gvisor/pkg/syserror"
+)
+
+// subtasksInode represents the inode for /proc/[pid]/task/ directory.
+//
+// +stateify savable
+type subtasksInode struct {
+	kernfs.InodeNotSymlink
+	kernfs.InodeDirectoryNoNewChildren
+	kernfs.InodeAttrs
+	kernfs.OrderedChildren
+
+	task              *kernel.Task
+	pidns             *kernel.PIDNamespace
+	inoGen            InoGenerator
+	cgroupControllers map[string]string
+}
+
+var _ kernfs.Inode = (*subtasksInode)(nil)
+
+func newSubtasks(task *kernel.Task, pidns *kernel.PIDNamespace, inoGen InoGenerator, cgroupControllers map[string]string) *kernfs.Dentry {
+	subInode := &subtasksInode{
+		task:              task,
+		pidns:             pidns,
+		inoGen:            inoGen,
+		cgroupControllers: cgroupControllers,
+	}
+	// Note: credentials are overridden by taskOwnedInode.
+	subInode.InodeAttrs.Init(task.Credentials(), inoGen.NextIno(), linux.ModeDirectory|0555)
+	subInode.OrderedChildren.Init(kernfs.OrderedChildrenOptions{})
+
+	inode := &taskOwnedInode{Inode: subInode, owner: task}
+	dentry := &kernfs.Dentry{}
+	dentry.Init(inode)
+
+	return dentry
+}
+
+// Valid implements kernfs.inodeDynamicLookup.
+func (i *subtasksInode) Valid(ctx context.Context) bool {
+	return true
+}
+
+// Lookup implements kernfs.inodeDynamicLookup.
+func (i *subtasksInode) Lookup(ctx context.Context, name string) (*vfs.Dentry, error) {
+	tid, err := strconv.ParseUint(name, 10, 32)
+	if err != nil {
+		return nil, syserror.ENOENT
+	}
+
+	subTask := i.pidns.TaskWithID(kernel.ThreadID(tid))
+	if subTask == nil {
+		return nil, syserror.ENOENT
+	}
+	if subTask.ThreadGroup() != i.task.ThreadGroup() {
+		return nil, syserror.ENOENT
+	}
+
+	subTaskDentry := newTaskInode(i.inoGen, subTask, i.pidns, false, i.cgroupControllers)
+	return subTaskDentry.VFSDentry(), nil
+}
+
+// IterDirents implements kernfs.inodeDynamicLookup.
+func (i *subtasksInode) IterDirents(ctx context.Context, cb vfs.IterDirentsCallback, offset, relOffset int64) (int64, error) {
+	tasks := i.task.ThreadGroup().MemberIDs(i.pidns)
+	if len(tasks) == 0 {
+		return offset, syserror.ENOENT
+	}
+
+	tids := make([]int, 0, len(tasks))
+	for _, tid := range tasks {
+		tids = append(tids, int(tid))
+	}
+
+	sort.Ints(tids)
+	for _, tid := range tids[relOffset:] {
+		dirent := vfs.Dirent{
+			Name:    strconv.FormatUint(uint64(tid), 10),
+			Type:    linux.DT_DIR,
+			Ino:     i.inoGen.NextIno(),
+			NextOff: offset + 1,
+		}
+		if !cb.Handle(dirent) {
+			return offset, nil
+		}
+		offset++
+	}
+	return offset, nil
+}
+
+// Open implements kernfs.Inode.
+func (i *subtasksInode) Open(rp *vfs.ResolvingPath, vfsd *vfs.Dentry, flags uint32) (*vfs.FileDescription, error) {
+	fd := &kernfs.GenericDirectoryFD{}
+	fd.Init(rp.Mount(), vfsd, &i.OrderedChildren, flags)
+	return fd.VFSFileDescription(), nil
+}
+
+// Stat implements kernfs.Inode.
+func (i *subtasksInode) Stat(vsfs *vfs.Filesystem) linux.Statx {
+	stat := i.InodeAttrs.Stat(vsfs)
+	stat.Nlink += uint32(i.task.ThreadGroup().Count())
+	return stat
+}