Stub oom_score_adj and oom_score.

Adds an oom_score_adj and oom_score proc file stub. oom_score_adj accepts
writes of values -1000 to 1000 and persists the value with the task. New tasks
inherit the parent's oom_score_adj.

oom_score is a read-only stub that always returns the value '0'.

Issue #202

PiperOrigin-RevId: 299245355

3 files changed, 67 insertions, 20 deletions

diff --git a/pkg/sentry/fsimpl/proc/task.go b/pkg/sentry/fsimpl/proc/task.go
index 2d814668a..18e5cd6f6 100644
--- a/pkg/sentry/fsimpl/proc/task.go
+++ b/pkg/sentry/fsimpl/proc/task.go
@@ -62,11 +62,13 @@ func newTaskInode(inoGen InoGenerator, task *kernel.Task, pidns *kernel.PIDNames
 			"pid":  newNamespaceSymlink(task, inoGen.NextIno(), "pid"),
 			"user": newNamespaceSymlink(task, inoGen.NextIno(), "user"),
 		}),
-		"smaps":   newTaskOwnedFile(task, inoGen.NextIno(), 0444, &smapsData{task: task}),
-		"stat":    newTaskOwnedFile(task, inoGen.NextIno(), 0444, &taskStatData{task: task, pidns: pidns, tgstats: isThreadGroup}),
-		"statm":   newTaskOwnedFile(task, inoGen.NextIno(), 0444, &statmData{task: task}),
-		"status":  newTaskOwnedFile(task, inoGen.NextIno(), 0444, &statusData{task: task, pidns: pidns}),
-		"uid_map": newTaskOwnedFile(task, inoGen.NextIno(), 0644, &idMapData{task: task, gids: false}),
+		"oom_score":     newTaskOwnedFile(task, inoGen.NextIno(), 0444, newStaticFile("0\n")),
+		"oom_score_adj": newTaskOwnedFile(task, inoGen.NextIno(), 0644, &oomScoreAdj{task: task}),
+		"smaps":         newTaskOwnedFile(task, inoGen.NextIno(), 0444, &smapsData{task: task}),
+		"stat":          newTaskOwnedFile(task, inoGen.NextIno(), 0444, &taskStatData{task: task, pidns: pidns, tgstats: isThreadGroup}),
+		"statm":         newTaskOwnedFile(task, inoGen.NextIno(), 0444, &statmData{task: task}),
+		"status":        newTaskOwnedFile(task, inoGen.NextIno(), 0444, &statusData{task: task, pidns: pidns}),
+		"uid_map":       newTaskOwnedFile(task, inoGen.NextIno(), 0644, &idMapData{task: task, gids: false}),
 	}
 	if isThreadGroup {
 		contents["task"] = newSubtasks(task, pidns, inoGen, cgroupControllers)
diff --git a/pkg/sentry/fsimpl/proc/task_files.go b/pkg/sentry/fsimpl/proc/task_files.go
index efd3b3453..5a231ac86 100644
--- a/pkg/sentry/fsimpl/proc/task_files.go
+++ b/pkg/sentry/fsimpl/proc/task_files.go
@@ -525,3 +525,46 @@ func (i *ioData) Generate(ctx context.Context, buf *bytes.Buffer) error {
 	fmt.Fprintf(buf, "cancelled_write_bytes: %d\n", io.BytesWriteCancelled)
 	return nil
 }
+
+// oomScoreAdj is a stub of the /proc/<pid>/oom_score_adj file.
+//
+// +stateify savable
+type oomScoreAdj struct {
+	kernfs.DynamicBytesFile
+
+	task *kernel.Task
+}
+
+var _ vfs.WritableDynamicBytesSource = (*oomScoreAdj)(nil)
+
+// Generate implements vfs.DynamicBytesSource.Generate.
+func (o *oomScoreAdj) Generate(ctx context.Context, buf *bytes.Buffer) error {
+	adj, err := o.task.OOMScoreAdj()
+	if err != nil {
+		return err
+	}
+	fmt.Fprintf(buf, "%d\n", adj)
+	return nil
+}
+
+// Write implements vfs.WritableDynamicBytesSource.Write.
+func (o *oomScoreAdj) Write(ctx context.Context, src usermem.IOSequence, offset int64) (int64, error) {
+	if src.NumBytes() == 0 {
+		return 0, nil
+	}
+
+	// Limit input size so as not to impact performance if input size is large.
+	src = src.TakeFirst(usermem.PageSize - 1)
+
+	var v int32
+	n, err := usermem.CopyInt32StringInVec(ctx, src.IO, src.Addrs, &v, src.Opts)
+	if err != nil {
+		return 0, err
+	}
+
+	if err := o.task.SetOOMScoreAdj(v); err != nil {
+		return 0, err
+	}
+
+	return n, nil
+}
diff --git a/pkg/sentry/fsimpl/proc/tasks_test.go b/pkg/sentry/fsimpl/proc/tasks_test.go
index c5d531fe0..0eb401619 100644
--- a/pkg/sentry/fsimpl/proc/tasks_test.go
+++ b/pkg/sentry/fsimpl/proc/tasks_test.go
@@ -63,21 +63,23 @@ var (
 		"thread-self": threadSelfLink.NextOff,
 	}
 	taskStaticFiles = map[string]testutil.DirentType{
-		"auxv":    linux.DT_REG,
-		"cgroup":  linux.DT_REG,
-		"cmdline": linux.DT_REG,
-		"comm":    linux.DT_REG,
-		"environ": linux.DT_REG,
-		"gid_map": linux.DT_REG,
-		"io":      linux.DT_REG,
-		"maps":    linux.DT_REG,
-		"ns":      linux.DT_DIR,
-		"smaps":   linux.DT_REG,
-		"stat":    linux.DT_REG,
-		"statm":   linux.DT_REG,
-		"status":  linux.DT_REG,
-		"task":    linux.DT_DIR,
-		"uid_map": linux.DT_REG,
+		"auxv":          linux.DT_REG,
+		"cgroup":        linux.DT_REG,
+		"cmdline":       linux.DT_REG,
+		"comm":          linux.DT_REG,
+		"environ":       linux.DT_REG,
+		"gid_map":       linux.DT_REG,
+		"io":            linux.DT_REG,
+		"maps":          linux.DT_REG,
+		"ns":            linux.DT_DIR,
+		"oom_score":     linux.DT_REG,
+		"oom_score_adj": linux.DT_REG,
+		"smaps":         linux.DT_REG,
+		"stat":          linux.DT_REG,
+		"statm":         linux.DT_REG,
+		"status":        linux.DT_REG,
+		"task":          linux.DT_DIR,
+		"uid_map":       linux.DT_REG,
 	}
 )