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, 60 insertions, 0 deletions

diff --git a/pkg/sentry/fsimpl/cgroupfs/memory.go b/pkg/sentry/fsimpl/cgroupfs/memory.go
new file mode 100644
index 000000000..eaf40a753
--- /dev/null
+++ b/pkg/sentry/fsimpl/cgroupfs/memory.go
@@ -0,0 +1,60 @@
+// Copyright 2021 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 cgroupfs
+
+import (
+	"bytes"
+	"fmt"
+
+	"gvisor.dev/gvisor/pkg/context"
+	"gvisor.dev/gvisor/pkg/sentry/fsimpl/kernfs"
+	"gvisor.dev/gvisor/pkg/sentry/kernel"
+	"gvisor.dev/gvisor/pkg/sentry/kernel/auth"
+	"gvisor.dev/gvisor/pkg/sentry/usage"
+)
+
+// +stateify savable
+type memoryController struct {
+	controllerCommon
+}
+
+var _ controller = (*memoryController)(nil)
+
+func newMemoryController(fs *filesystem) *memoryController {
+	c := &memoryController{}
+	c.controllerCommon.init(controllerMemory, fs)
+	return c
+}
+
+// AddControlFiles implements controller.AddControlFiles.
+func (c *memoryController) AddControlFiles(ctx context.Context, creds *auth.Credentials, _ *cgroupInode, contents map[string]kernfs.Inode) {
+	contents["memory.usage_in_bytes"] = c.fs.newControllerFile(ctx, creds, &memoryUsageInBytesData{})
+}
+
+// +stateify savable
+type memoryUsageInBytesData struct{}
+
+// Generate implements vfs.DynamicBytesSource.Generate.
+func (d *memoryUsageInBytesData) Generate(ctx context.Context, buf *bytes.Buffer) error {
+	// TODO(b/183151557): This is a giant hack, we're using system-wide
+	// accounting since we know there is only one cgroup.
+	k := kernel.KernelFromContext(ctx)
+	mf := k.MemoryFile()
+	mf.UpdateUsage()
+	_, totalBytes := usage.MemoryAccounting.Copy()
+
+	fmt.Fprintf(buf, "%d\n", totalBytes)
+	return nil
+}