Add context to state.

PiperOrigin-RevId: 277840416

pkg/sentry/context/context.go

@@ -12,10 +12,20 @@
 // See the License for the specific language governing permissions and
 // limitations under the License.
 
-// Package context defines the sentry's Context type.
+// Package context defines an internal context type.
+//
+// The given Context conforms to the standard Go context, but mandates
+// additional methods that are specific to the kernel internals. Note however,
+// that the Context described by this package carries additional constraints
+// regarding concurrent access and retaining beyond the scope of a call.
+//
+// See the Context type for complete details.
 package context
 
 import (
+	"context"
+	"time"
+
 	"gvisor.dev/gvisor/pkg/amutex"
 	"gvisor.dev/gvisor/pkg/log"
 )
@@ -59,6 +69,7 @@ func ThreadGroupIDFromContext(ctx Context) (tgid int32, ok bool) {
 type Context interface {
 	log.Logger
 	amutex.Sleeper
+	context.Context
 
 	// UninterruptibleSleepStart indicates the beginning of an uninterruptible
 	// sleep state (equivalent to Linux's TASK_UNINTERRUPTIBLE). If deactivate
@@ -72,32 +83,10 @@ type Context interface {
 	// AddressSpace is activated. Normally activate is the same value as the
 	// deactivate parameter passed to UninterruptibleSleepStart.
 	UninterruptibleSleepFinish(activate bool)
-
-	// Value returns the value associated with this Context for key, or nil if
-	// no value is associated with key. Successive calls to Value with the same
-	// key returns the same result.
-	//
-	// A key identifies a specific value in a Context. Functions that wish to
-	// retrieve values from Context typically allocate a key in a global
-	// variable then use that key as the argument to Context.Value. A key can
-	// be any type that supports equality; packages should define keys as an
-	// unexported type to avoid collisions.
-	Value(key interface{}) interface{}
 }
 
-type logContext struct {
-	log.Logger
-	NoopSleeper
-}
-
-// Value implements Context.Value.
-func (logContext) Value(key interface{}) interface{} {
-	return nil
-}
-
-// NoopSleeper is a noop implementation of amutex.Sleeper and
-// Context.UninterruptibleSleep* methods for anonymous embedding in other types
-// that do not want to notify kernel.Task about sleeps.
+// NoopSleeper is a noop implementation of amutex.Sleeper and UninterruptibleSleep
+// methods for anonymous embedding in other types that do not implement sleeps.
 type NoopSleeper struct {
 	amutex.NoopSleeper
 }
@@ -108,6 +97,32 @@ func (NoopSleeper) UninterruptibleSleepStart(bool) {}
 // UninterruptibleSleepFinish does nothing.
 func (NoopSleeper) UninterruptibleSleepFinish(bool) {}
 
+// Deadline returns zero values, meaning no deadline.
+func (NoopSleeper) Deadline() (time.Time, bool) {
+	return time.Time{}, false
+}
+
+// Done returns nil.
+func (NoopSleeper) Done() <-chan struct{} {
+	return nil
+}
+
+// Err returns nil.
+func (NoopSleeper) Err() error {
+	return nil
+}
+
+// logContext implements basic logging.
+type logContext struct {
+	log.Logger
+	NoopSleeper
+}
+
+// Value implements Context.Value.
+func (logContext) Value(key interface{}) interface{} {
+	return nil
+}
+
 // bgContext is the context returned by context.Background.
 var bgContext = &logContext{Logger: log.Log()}
 

pkg/sentry/kernel/context.go

@@ -15,6 +15,8 @@
 package kernel
 
 import (
+	"time"
+
 	"gvisor.dev/gvisor/pkg/log"
 	"gvisor.dev/gvisor/pkg/sentry/context"
 )
@@ -97,6 +99,21 @@ func TaskFromContext(ctx context.Context) *Task {
 	return nil
 }
 
+// Deadline implements context.Context.Deadline.
+func (*Task) Deadline() (time.Time, bool) {
+	return time.Time{}, false
+}
+
+// Done implements context.Context.Done.
+func (*Task) Done() <-chan struct{} {
+	return nil
+}
+
+// Err implements context.Context.Err.
+func (*Task) Err() error {
+	return nil
+}
+
 // AsyncContext returns a context.Context that may be used by goroutines that
 // do work on behalf of t and therefore share its contextual values, but are
 // not t's task goroutine (e.g. asynchronous I/O).
@@ -129,6 +146,21 @@ func (ctx taskAsyncContext) IsLogging(level log.Level) bool {
 	return ctx.t.IsLogging(level)
 }
 
+// Deadline implements context.Context.Deadline.
+func (ctx taskAsyncContext) Deadline() (time.Time, bool) {
+	return ctx.t.Deadline()
+}
+
+// Done implements context.Context.Done.
+func (ctx taskAsyncContext) Done() <-chan struct{} {
+	return ctx.t.Done()
+}
+
+// Err implements context.Context.Err.
+func (ctx taskAsyncContext) Err() error {
+	return ctx.t.Err()
+}
+
 // Value implements context.Context.Value.
 func (ctx taskAsyncContext) Value(key interface{}) interface{} {
 	return ctx.t.Value(key)

pkg/sentry/kernel/kernel.go

@@ -391,7 +391,7 @@ func (k *Kernel) SaveTo(w io.Writer) error {
 	//
 	// N.B. This will also be saved along with the full kernel save below.
 	cpuidStart := time.Now()
-	if err := state.Save(w, k.FeatureSet(), nil); err != nil {
+	if err := state.Save(k.SupervisorContext(), w, k.FeatureSet(), nil); err != nil {
 		return err
 	}
 	log.Infof("CPUID save took [%s].", time.Since(cpuidStart))
@@ -399,7 +399,7 @@ func (k *Kernel) SaveTo(w io.Writer) error {
 	// Save the kernel state.
 	kernelStart := time.Now()
 	var stats state.Stats
-	if err := state.Save(w, k, &stats); err != nil {
+	if err := state.Save(k.SupervisorContext(), w, k, &stats); err != nil {
 		return err
 	}
 	log.Infof("Kernel save stats: %s", &stats)
@@ -407,7 +407,7 @@ func (k *Kernel) SaveTo(w io.Writer) error {
 
 	// Save the memory file's state.
 	memoryStart := time.Now()
-	if err := k.mf.SaveTo(w); err != nil {
+	if err := k.mf.SaveTo(k.SupervisorContext(), w); err != nil {
 		return err
 	}
 	log.Infof("Memory save took [%s].", time.Since(memoryStart))
@@ -542,7 +542,7 @@ func (k *Kernel) LoadFrom(r io.Reader, net inet.Stack, clocks sentrytime.Clocks)
 	// don't need to explicitly install it in the Kernel.
 	cpuidStart := time.Now()
 	var features cpuid.FeatureSet
-	if err := state.Load(r, &features, nil); err != nil {
+	if err := state.Load(k.SupervisorContext(), r, &features, nil); err != nil {
 		return err
 	}
 	log.Infof("CPUID load took [%s].", time.Since(cpuidStart))
@@ -558,7 +558,7 @@ func (k *Kernel) LoadFrom(r io.Reader, net inet.Stack, clocks sentrytime.Clocks)
 	// Load the kernel state.
 	kernelStart := time.Now()
 	var stats state.Stats
-	if err := state.Load(r, k, &stats); err != nil {
+	if err := state.Load(k.SupervisorContext(), r, k, &stats); err != nil {
 		return err
 	}
 	log.Infof("Kernel load stats: %s", &stats)
@@ -566,7 +566,7 @@ func (k *Kernel) LoadFrom(r io.Reader, net inet.Stack, clocks sentrytime.Clocks)
 
 	// Load the memory file's state.
 	memoryStart := time.Now()
-	if err := k.mf.LoadFrom(r); err != nil {
+	if err := k.mf.LoadFrom(k.SupervisorContext(), r); err != nil {
 		return err
 	}
 	log.Infof("Memory load took [%s].", time.Since(memoryStart))
@@ -1322,6 +1322,7 @@ func (k *Kernel) ListSockets() []*SocketEntry {
 	return socks
 }
 
+// supervisorContext is a privileged context.
 type supervisorContext struct {
 	context.NoopSleeper
 	log.Logger

pkg/sentry/pgalloc/save_restore.go

@@ -16,6 +16,7 @@ package pgalloc
 
 import (
 	"bytes"
+	"context"
 	"fmt"
 	"io"
 	"runtime"
@@ -29,7 +30,7 @@ import (
 )
 
 // SaveTo writes f's state to the given stream.
-func (f *MemoryFile) SaveTo(w io.Writer) error {
+func (f *MemoryFile) SaveTo(ctx context.Context, w io.Writer) error {
 	// Wait for reclaim.
 	f.mu.Lock()
 	defer f.mu.Unlock()
@@ -78,10 +79,10 @@ func (f *MemoryFile) SaveTo(w io.Writer) error {
 	}
 
 	// Save metadata.
-	if err := state.Save(w, &f.fileSize, nil); err != nil {
+	if err := state.Save(ctx, w, &f.fileSize, nil); err != nil {
 		return err
 	}
-	if err := state.Save(w, &f.usage, nil); err != nil {
+	if err := state.Save(ctx, w, &f.usage, nil); err != nil {
 		return err
 	}
 
@@ -114,9 +115,9 @@ func (f *MemoryFile) SaveTo(w io.Writer) error {
 }
 
 // LoadFrom loads MemoryFile state from the given stream.
-func (f *MemoryFile) LoadFrom(r io.Reader) error {
+func (f *MemoryFile) LoadFrom(ctx context.Context, r io.Reader) error {
 	// Load metadata.
-	if err := state.Load(r, &f.fileSize, nil); err != nil {
+	if err := state.Load(ctx, r, &f.fileSize, nil); err != nil {
 		return err
 	}
 	if err := f.file.Truncate(f.fileSize); err != nil {
@@ -124,7 +125,7 @@ func (f *MemoryFile) LoadFrom(r io.Reader) error {
 	}
 	newMappings := make([]uintptr, f.fileSize>>chunkShift)
 	f.mappings.Store(newMappings)
-	if err := state.Load(r, &f.usage, nil); err != nil {
+	if err := state.Load(ctx, r, &f.usage, nil); err != nil {
 		return err
 	}
 

pkg/state/decode.go

@@ -16,6 +16,7 @@ package state
 
 import (
 	"bytes"
+	"context"
 	"encoding/binary"
 	"errors"
 	"fmt"
@@ -133,6 +134,9 @@ func (os *objectState) findCycle() []*objectState {
 // to ensure that all callbacks are executed, otherwise the callback graph was
 // not acyclic.
 type decodeState struct {
+	// ctx is the decode context.
+	ctx context.Context
+
 	// objectByID is the set of objects in progress.
 	objectsByID map[uint64]*objectState
 

pkg/state/encode.go

@@ -16,6 +16,7 @@ package state
 
 import (
 	"container/list"
+	"context"
 	"encoding/binary"
 	"fmt"
 	"io"
@@ -38,6 +39,9 @@ type queuedObject struct {
 // The encoding process is a breadth-first traversal of the object graph. The
 // inherent races and dependencies are much simpler than the decode case.
 type encodeState struct {
+	// ctx is the encode context.
+	ctx context.Context
+
 	// lastID is the last object ID.
 	//
 	// See idsByObject for context. Because of the special zero encoding

pkg/state/map.go

@@ -15,6 +15,7 @@
 package state
 
 import (
+	"context"
 	"fmt"
 	"reflect"
 	"sort"
@@ -219,3 +220,13 @@ func (m Map) AfterLoad(fn func()) {
 	// data dependencies have been cleared.
 	m.os.callbacks = append(m.os.callbacks, fn)
 }
+
+// Context returns the current context object.
+func (m Map) Context() context.Context {
+	if m.es != nil {
+		return m.es.ctx
+	} else if m.ds != nil {
+		return m.ds.ctx
+	}
+	return context.Background() // No context.
+}

pkg/state/state.go

@@ -50,6 +50,7 @@
 package state
 
 import (
+	"context"
 	"fmt"
 	"io"
 	"reflect"
@@ -86,9 +87,10 @@ func UnwrapErrState(err error) error {
 }
 
 // Save saves the given object state.
-func Save(w io.Writer, rootPtr interface{}, stats *Stats) error {
+func Save(ctx context.Context, w io.Writer, rootPtr interface{}, stats *Stats) error {
 	// Create the encoding state.
 	es := &encodeState{
+		ctx:         ctx,
 		idsByObject: make(map[uintptr]uint64),
 		w:           w,
 		stats:       stats,
@@ -101,9 +103,10 @@ func Save(w io.Writer, rootPtr interface{}, stats *Stats) error {
 }
 
 // Load loads a checkpoint.
-func Load(r io.Reader, rootPtr interface{}, stats *Stats) error {
+func Load(ctx context.Context, r io.Reader, rootPtr interface{}, stats *Stats) error {
 	// Create the decoding state.
 	ds := &decodeState{
+		ctx:         ctx,
 		objectsByID: make(map[uint64]*objectState),
 		deferred:    make(map[uint64]*pb.Object),
 		r:           r,

pkg/state/state_test.go

@@ -16,6 +16,7 @@ package state
 
 import (
 	"bytes"
+	"context"
 	"io/ioutil"
 	"math"
 	"reflect"
@@ -46,7 +47,7 @@ func runTest(t *testing.T, tests []TestCase) {
 			saveBuffer := &bytes.Buffer{}
 			saveObjectPtr := reflect.New(reflect.TypeOf(root))
 			saveObjectPtr.Elem().Set(reflect.ValueOf(root))
-			if err := Save(saveBuffer, saveObjectPtr.Interface(), nil); err != nil && !test.Fail {
+			if err := Save(context.Background(), saveBuffer, saveObjectPtr.Interface(), nil); err != nil && !test.Fail {
 				t.Errorf("    FAIL: Save failed unexpectedly: %v", err)
 				continue
 			} else if err != nil {
@@ -56,7 +57,7 @@ func runTest(t *testing.T, tests []TestCase) {
 
 			// Load a new copy of the object.
 			loadObjectPtr := reflect.New(reflect.TypeOf(root))
-			if err := Load(bytes.NewReader(saveBuffer.Bytes()), loadObjectPtr.Interface(), nil); err != nil && !test.Fail {
+			if err := Load(context.Background(), bytes.NewReader(saveBuffer.Bytes()), loadObjectPtr.Interface(), nil); err != nil && !test.Fail {
 				t.Errorf("    FAIL: Load failed unexpectedly: %v", err)
 				continue
 			} else if err != nil {
@@ -624,7 +625,7 @@ func BenchmarkEncoding(b *testing.B) {
 	bs := buildObject(b.N)
 	var stats Stats
 	b.StartTimer()
-	if err := Save(ioutil.Discard, bs, &stats); err != nil {
+	if err := Save(context.Background(), ioutil.Discard, bs, &stats); err != nil {
 		b.Errorf("save failed: %v", err)
 	}
 	b.StopTimer()
@@ -638,12 +639,12 @@ func BenchmarkDecoding(b *testing.B) {
 	bs := buildObject(b.N)
 	var newBS benchStruct
 	buf := &bytes.Buffer{}
-	if err := Save(buf, bs, nil); err != nil {
+	if err := Save(context.Background(), buf, bs, nil); err != nil {
 		b.Errorf("save failed: %v", err)
 	}
 	var stats Stats
 	b.StartTimer()
-	if err := Load(buf, &newBS, &stats); err != nil {
+	if err := Load(context.Background(), buf, &newBS, &stats); err != nil {
 		b.Errorf("load failed: %v", err)
 	}
 	b.StopTimer()