Add Usage controls

Add Usage controls and implement "usage/usagefd" commands.

PiperOrigin-RevId: 390507423

2 files changed, 185 insertions, 0 deletions

diff --git a/pkg/sentry/control/BUILD b/pkg/sentry/control/BUILD
index 7ee237c9f..fa3fe47c1 100644
--- a/pkg/sentry/control/BUILD
+++ b/pkg/sentry/control/BUILD
@@ -12,6 +12,7 @@ go_library(
         "pprof.go",
         "proc.go",
         "state.go",
+        "usage.go",
     ],
     visibility = [
         "//:sandbox",
@@ -39,6 +40,7 @@ go_library(
         "//pkg/tcpip/link/sniffer",
         "//pkg/urpc",
         "//pkg/usermem",
+        "@org_golang_x_sys//unix:go_default_library",
     ],
 )
 
diff --git a/pkg/sentry/control/usage.go b/pkg/sentry/control/usage.go
new file mode 100644
index 000000000..cc78d3f45
--- /dev/null
+++ b/pkg/sentry/control/usage.go
@@ -0,0 +1,183 @@
+// 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 control
+
+import (
+	"fmt"
+	"os"
+	"runtime"
+
+	"golang.org/x/sys/unix"
+	"gvisor.dev/gvisor/pkg/sentry/kernel"
+	"gvisor.dev/gvisor/pkg/sentry/usage"
+	"gvisor.dev/gvisor/pkg/urpc"
+)
+
+// Usage includes usage-related RPC stubs.
+type Usage struct {
+	Kernel *kernel.Kernel
+}
+
+// MemoryUsageOpts contains usage options.
+type MemoryUsageOpts struct {
+	// Full indicates that a full accounting should be done. If Full is not
+	// specified, then a partial accounting will be done, and Unknown will
+	// contain a majority of memory. See Collect for more information.
+	Full bool `json:"Full"`
+}
+
+// MemoryUsage is a memory usage structure.
+type MemoryUsage struct {
+	Unknown   uint64 `json:"Unknown"`
+	System    uint64 `json:"System"`
+	Anonymous uint64 `json:"Anonymous"`
+	PageCache uint64 `json:"PageCache"`
+	Mapped    uint64 `json:"Mapped"`
+	Tmpfs     uint64 `json:"Tmpfs"`
+	Ramdiskfs uint64 `json:"Ramdiskfs"`
+	Total     uint64 `json:"Total"`
+}
+
+// MemoryUsageFileOpts contains usage file options.
+type MemoryUsageFileOpts struct {
+	// Version is used to ensure both sides agree on the format of the
+	// shared memory buffer.
+	Version uint64 `json:"Version"`
+}
+
+// MemoryUsageFile contains the file handle to the usage file.
+type MemoryUsageFile struct {
+	urpc.FilePayload
+}
+
+// UsageFD returns the file that tracks the memory usage of the application.
+func (u *Usage) UsageFD(opts *MemoryUsageFileOpts, out *MemoryUsageFile) error {
+	// Only support version 1 for now.
+	if opts.Version != 1 {
+		return fmt.Errorf("unsupported version requested: %d", opts.Version)
+	}
+
+	mf := u.Kernel.MemoryFile()
+	*out = MemoryUsageFile{
+		FilePayload: urpc.FilePayload{
+			Files: []*os.File{
+				usage.MemoryAccounting.File,
+				mf.File(),
+			},
+		},
+	}
+
+	return nil
+}
+
+// Collect returns memory used by the sandboxed application.
+func (u *Usage) Collect(opts *MemoryUsageOpts, out *MemoryUsage) error {
+	if opts.Full {
+		// Ensure everything is up to date.
+		if err := u.Kernel.MemoryFile().UpdateUsage(); err != nil {
+			return err
+		}
+
+		// Copy out a snapshot.
+		snapshot, total := usage.MemoryAccounting.Copy()
+		*out = MemoryUsage{
+			System:    snapshot.System,
+			Anonymous: snapshot.Anonymous,
+			PageCache: snapshot.PageCache,
+			Mapped:    snapshot.Mapped,
+			Tmpfs:     snapshot.Tmpfs,
+			Ramdiskfs: snapshot.Ramdiskfs,
+			Total:     total,
+		}
+	} else {
+		// Get total usage from the MemoryFile implementation.
+		total, err := u.Kernel.MemoryFile().TotalUsage()
+		if err != nil {
+			return err
+		}
+
+		// The memory accounting is guaranteed to be accurate only when
+		// UpdateUsage is called. If UpdateUsage is not called, then only Mapped
+		// will be up-to-date.
+		snapshot, _ := usage.MemoryAccounting.Copy()
+		*out = MemoryUsage{
+			Unknown: total,
+			Mapped:  snapshot.Mapped,
+			Total:   total + snapshot.Mapped,
+		}
+
+	}
+
+	return nil
+}
+
+// UsageReduceOpts contains options to Usage.Reduce().
+type UsageReduceOpts struct {
+	// If Wait is true, Reduce blocks until all activity initiated by
+	// Usage.Reduce() has completed.
+	Wait bool `json:"wait"`
+}
+
+// UsageReduceOutput contains output from Usage.Reduce().
+type UsageReduceOutput struct{}
+
+// Reduce requests that the sentry attempt to reduce its memory usage.
+func (u *Usage) Reduce(opts *UsageReduceOpts, out *UsageReduceOutput) error {
+	mf := u.Kernel.MemoryFile()
+	mf.StartEvictions()
+	if opts.Wait {
+		mf.WaitForEvictions()
+	}
+	return nil
+}
+
+// MemoryUsageRecord contains the mapping and platform memory file.
+type MemoryUsageRecord struct {
+	mmap  uintptr
+	stats *usage.RTMemoryStats
+	mf    os.File
+}
+
+// NewMemoryUsageRecord creates a new MemoryUsageRecord from usageFile and
+// platformFile.
+func NewMemoryUsageRecord(usageFile, platformFile os.File) (*MemoryUsageRecord, error) {
+	mmap, _, e := unix.RawSyscall6(unix.SYS_MMAP, 0, usage.RTMemoryStatsSize, unix.PROT_READ, unix.MAP_SHARED, usageFile.Fd(), 0)
+	if e != 0 {
+		return nil, fmt.Errorf("mmap returned %d, want 0", e)
+	}
+
+	m := MemoryUsageRecord{
+		mmap:  mmap,
+		stats: usage.RTMemoryStatsPointer(mmap),
+		mf:    platformFile,
+	}
+
+	runtime.SetFinalizer(&m, finalizer)
+	return &m, nil
+}
+
+func finalizer(m *MemoryUsageRecord) {
+	unix.RawSyscall(unix.SYS_MUNMAP, m.mmap, usage.RTMemoryStatsSize, 0)
+}
+
+// Fetch fetches the usage info from a MemoryUsageRecord.
+func (m *MemoryUsageRecord) Fetch() (mapped, unknown, total uint64, err error) {
+	var stat unix.Stat_t
+	if err := unix.Fstat(int(m.mf.Fd()), &stat); err != nil {
+		return 0, 0, 0, err
+	}
+	fmem := uint64(stat.Blocks) * 512
+	return m.stats.RTMapped, fmem, m.stats.RTMapped + fmem, nil
+}