Implement cgroupfs.

A skeleton implementation of cgroupfs. It supports trivial cpu and
memory controllers with no support for hierarchies.

PiperOrigin-RevId: 366561126

1 files changed, 14 insertions, 9 deletions

diff --git a/pkg/sentry/fsimpl/proc/task.go b/pkg/sentry/fsimpl/proc/task.go
index fea138f93..d05cc1508 100644
--- a/pkg/sentry/fsimpl/proc/task.go
+++ b/pkg/sentry/fsimpl/proc/task.go
@@ -47,7 +47,7 @@ type taskInode struct {
 
 var _ kernfs.Inode = (*taskInode)(nil)
 
-func (fs *filesystem) newTaskInode(ctx context.Context, task *kernel.Task, pidns *kernel.PIDNamespace, isThreadGroup bool, cgroupControllers map[string]string) (kernfs.Inode, error) {
+func (fs *filesystem) newTaskInode(ctx context.Context, task *kernel.Task, pidns *kernel.PIDNamespace, isThreadGroup bool, fakeCgroupControllers map[string]string) (kernfs.Inode, error) {
 	if task.ExitState() == kernel.TaskExitDead {
 		return nil, syserror.ESRCH
 	}
@@ -82,10 +82,12 @@ func (fs *filesystem) newTaskInode(ctx context.Context, task *kernel.Task, pidns
 		"uid_map":       fs.newTaskOwnedInode(ctx, task, fs.NextIno(), 0644, &idMapData{task: task, gids: false}),
 	}
 	if isThreadGroup {
-		contents["task"] = fs.newSubtasks(ctx, task, pidns, cgroupControllers)
+		contents["task"] = fs.newSubtasks(ctx, task, pidns, fakeCgroupControllers)
 	}
-	if len(cgroupControllers) > 0 {
-		contents["cgroup"] = fs.newTaskOwnedInode(ctx, task, fs.NextIno(), 0444, newCgroupData(cgroupControllers))
+	if len(fakeCgroupControllers) > 0 {
+		contents["cgroup"] = fs.newTaskOwnedInode(ctx, task, fs.NextIno(), 0444, newFakeCgroupData(fakeCgroupControllers))
+	} else {
+		contents["cgroup"] = fs.newTaskOwnedInode(ctx, task, fs.NextIno(), 0444, &taskCgroupData{task: task})
 	}
 
 	taskInode := &taskInode{task: task}
@@ -226,11 +228,14 @@ func newIO(t *kernel.Task, isThreadGroup bool) *ioData {
 	return &ioData{ioUsage: t}
 }
 
-// newCgroupData creates inode that shows cgroup information.
-// From man 7 cgroups: "For each cgroup hierarchy of which the process is a
-// member, there is one entry containing three colon-separated fields:
-//   hierarchy-ID:controller-list:cgroup-path"
-func newCgroupData(controllers map[string]string) dynamicInode {
+// newFakeCgroupData creates an inode that shows fake cgroup
+// information passed in as mount options.  From man 7 cgroups: "For
+// each cgroup hierarchy of which the process is a member, there is
+// one entry containing three colon-separated fields:
+// hierarchy-ID:controller-list:cgroup-path"
+//
+// TODO(b/182488796): Remove once all users adopt cgroupfs.
+func newFakeCgroupData(controllers map[string]string) dynamicInode {
 	var buf bytes.Buffer
 
 	// The hierarchy ids must be positive integers (for cgroup v1), but the