Move S/R code to separate file

Move Kernel S/R code to kernel_restore.go.

PiperOrigin-RevId: 691441815

pkg/sentry/kernel/BUILD

@@ -252,6 +252,7 @@ go_library(
         "kcov_unsafe.go",
         "kernel.go",
         "kernel_opts.go",
+        "kernel_restore.go",
         "kernel_state.go",
         "pending_signals.go",
         "pending_signals_list.go",

pkg/sentry/kernel/kernel.go

@@ -393,12 +393,6 @@ type Kernel struct {
 	UnixSocketOpts transport.UnixSocketOpts
 }
 
-// Saver is an interface for saving the kernel.
-type Saver interface {
-	SaveAsync() error
-	SpecEnviron(containerName string) []string
-}
-
 // InitKernelArgs holds arguments to Init.
 type InitKernelArgs struct {
 	// FeatureSet is the emulated CPU feature set.
@@ -1921,28 +1915,6 @@ func (k *Kernel) SetHostMount(mnt *vfs.Mount) {
 	k.hostMount = mnt
 }
 
-// AddStateToCheckpoint adds a key-value pair to be additionally checkpointed.
-func (k *Kernel) AddStateToCheckpoint(key, v any) {
-	k.checkpointMu.Lock()
-	defer k.checkpointMu.Unlock()
-	if k.additionalCheckpointState == nil {
-		k.additionalCheckpointState = make(map[any]any)
-	}
-	k.additionalCheckpointState[key] = v
-}
-
-// PopCheckpointState pops a key-value pair from the additional checkpoint
-// state. If the key doesn't exist, nil is returned.
-func (k *Kernel) PopCheckpointState(key any) any {
-	k.checkpointMu.Lock()
-	defer k.checkpointMu.Unlock()
-	if v, ok := k.additionalCheckpointState[key]; ok {
-		delete(k.additionalCheckpointState, key)
-		return v
-	}
-	return nil
-}
-
 // HostMount returns the hostfs mount.
 func (k *Kernel) HostMount() *vfs.Mount {
 	return k.hostMount
@@ -2202,79 +2174,3 @@ func (k *Kernel) ContainerName(cid string) string {
 	defer k.extMu.Unlock()
 	return k.containerNames[cid]
 }
-
-// SetSaver sets the kernel's Saver.
-// Thread-compatible.
-func (k *Kernel) SetSaver(s Saver) {
-	k.checkpointMu.Lock()
-	defer k.checkpointMu.Unlock()
-	k.saver = s
-}
-
-// Saver returns the kernel's Saver.
-// Thread-compatible.
-func (k *Kernel) Saver() Saver {
-	k.checkpointMu.Lock()
-	defer k.checkpointMu.Unlock()
-	return k.saver
-}
-
-// IncCheckpointCount increments the checkpoint counter.
-func (k *Kernel) IncCheckpointCount() {
-	k.checkpointMu.Lock()
-	defer k.checkpointMu.Unlock()
-	k.checkpointCounter++
-}
-
-// CheckpointCount returns the current checkpoint count. Note that the result
-// may be stale by the time the caller uses it.
-func (k *Kernel) CheckpointCount() uint32 {
-	k.checkpointMu.Lock()
-	defer k.checkpointMu.Unlock()
-	return k.checkpointCounter
-}
-
-// OnCheckpointAttempt is called when a checkpoint attempt is completed. err is
-// any checkpoint errors that may have occurred.
-func (k *Kernel) OnCheckpointAttempt(err error) {
-	k.checkpointMu.Lock()
-	defer k.checkpointMu.Unlock()
-	if err == nil {
-		k.checkpointCounter++
-	}
-	k.lastCheckpointStatus = err
-	k.checkpointCond.Broadcast()
-}
-
-// ResetCheckpointStatus resets the last checkpoint status, indicating a new
-// checkpoint is in progress. Caller must call OnCheckpointAttempt when the
-// checkpoint attempt is completed.
-func (k *Kernel) ResetCheckpointStatus() {
-	k.checkpointMu.Lock()
-	defer k.checkpointMu.Unlock()
-	k.lastCheckpointStatus = nil
-}
-
-// WaitCheckpoint waits for the Kernel to have been successfully checkpointed
-// n-1 times, then waits for either the n-th successful checkpoint (in which
-// case it returns nil) or any number of failed checkpoints (in which case it
-// returns an error returned by any such failure).
-func (k *Kernel) WaitCheckpoint(n uint32) error {
-	if n == 0 {
-		return nil
-	}
-	k.checkpointMu.Lock()
-	defer k.checkpointMu.Unlock()
-	if k.checkpointCounter >= n {
-		// n-th checkpoint already completed successfully.
-		return nil
-	}
-	for k.checkpointCounter < n {
-		if k.checkpointCounter == n-1 && k.lastCheckpointStatus != nil {
-			// n-th checkpoint was attempted but it had failed.
-			return k.lastCheckpointStatus
-		}
-		k.checkpointCond.Wait()
-	}
-	return nil
-}

pkg/sentry/kernel/kernel_restore.go

@@ -0,0 +1,119 @@
+// Copyright 2024 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 kernel
+
+// Saver is an interface for saving the kernel.
+type Saver interface {
+	SaveAsync() error
+	SpecEnviron(containerName string) []string
+}
+
+// AddStateToCheckpoint adds a key-value pair to be additionally checkpointed.
+func (k *Kernel) AddStateToCheckpoint(key, v any) {
+	k.checkpointMu.Lock()
+	defer k.checkpointMu.Unlock()
+	if k.additionalCheckpointState == nil {
+		k.additionalCheckpointState = make(map[any]any)
+	}
+	k.additionalCheckpointState[key] = v
+}
+
+// PopCheckpointState pops a key-value pair from the additional checkpoint
+// state. If the key doesn't exist, nil is returned.
+func (k *Kernel) PopCheckpointState(key any) any {
+	k.checkpointMu.Lock()
+	defer k.checkpointMu.Unlock()
+	if v, ok := k.additionalCheckpointState[key]; ok {
+		delete(k.additionalCheckpointState, key)
+		return v
+	}
+	return nil
+}
+
+// SetSaver sets the kernel's Saver.
+// Thread-compatible.
+func (k *Kernel) SetSaver(s Saver) {
+	k.checkpointMu.Lock()
+	defer k.checkpointMu.Unlock()
+	k.saver = s
+}
+
+// Saver returns the kernel's Saver.
+// Thread-compatible.
+func (k *Kernel) Saver() Saver {
+	k.checkpointMu.Lock()
+	defer k.checkpointMu.Unlock()
+	return k.saver
+}
+
+// IncCheckpointCount increments the checkpoint counter.
+func (k *Kernel) IncCheckpointCount() {
+	k.checkpointMu.Lock()
+	defer k.checkpointMu.Unlock()
+	k.checkpointCounter++
+}
+
+// CheckpointCount returns the current checkpoint count. Note that the result
+// may be stale by the time the caller uses it.
+func (k *Kernel) CheckpointCount() uint32 {
+	k.checkpointMu.Lock()
+	defer k.checkpointMu.Unlock()
+	return k.checkpointCounter
+}
+
+// OnCheckpointAttempt is called when a checkpoint attempt is completed. err is
+// any checkpoint errors that may have occurred.
+func (k *Kernel) OnCheckpointAttempt(err error) {
+	k.checkpointMu.Lock()
+	defer k.checkpointMu.Unlock()
+	if err == nil {
+		k.checkpointCounter++
+	}
+	k.lastCheckpointStatus = err
+	k.checkpointCond.Broadcast()
+}
+
+// ResetCheckpointStatus resets the last checkpoint status, indicating a new
+// checkpoint is in progress. Caller must call OnCheckpointAttempt when the
+// checkpoint attempt is completed.
+func (k *Kernel) ResetCheckpointStatus() {
+	k.checkpointMu.Lock()
+	defer k.checkpointMu.Unlock()
+	k.lastCheckpointStatus = nil
+}
+
+// WaitCheckpoint waits for the Kernel to have been successfully checkpointed
+// n-1 times, then waits for either the n-th successful checkpoint (in which
+// case it returns nil) or any number of failed checkpoints (in which case it
+// returns an error returned by any such failure).
+func (k *Kernel) WaitCheckpoint(n uint32) error {
+	if n == 0 {
+		return nil
+	}
+	k.checkpointMu.Lock()
+	defer k.checkpointMu.Unlock()
+	if k.checkpointCounter >= n {
+		// n-th checkpoint already completed successfully.
+		return nil
+	}
+	for k.checkpointCounter < n {
+		if k.checkpointCounter == n-1 && k.lastCheckpointStatus != nil {
+			// n-th checkpoint was attempted but it had failed.
+			return k.lastCheckpointStatus
+		}
+		k.checkpointCond.Wait()
+	}
+	return nil
+}