Add platform to statefile metadata and check it on restore.

Save/restoring across platforms is not supported. This CL encodifies that.

PiperOrigin-RevId: 808760537

Author: konstantin-s-bogom

pkg/sentry/platform/kvm/kvm.go

@@ -187,6 +187,11 @@ func (k *KVM) NewContext(pkgcontext.Context) platform.Context {
 	}
 }
 
+// Name implements platform.Platform.Name.
+func (*KVM) Name() string {
+	return "kvm"
+}
+
 type constructor struct{}
 
 func (*constructor) New(opts platform.Options) (platform.Platform, error) {

pkg/sentry/platform/platform.go

@@ -121,6 +121,9 @@ type Platform interface {
 	// in parallel. Concurrent calls to Context.Switch() beyond
 	// ConcurrencyCount() may block until previous calls have returned.
 	ConcurrencyCount() int
+
+	// Name returns the name of the platform.
+	Name() string
 }
 
 // NoCPUPreemptionDetection implements Platform.DetectsCPUPreemption and

pkg/sentry/platform/ptrace/ptrace.go

@@ -268,6 +268,11 @@ func (*PTrace) ConcurrencyCount() int {
 	return math.MaxInt
 }
 
+// Name implements platform.Platform.Name.
+func (*PTrace) Name() string {
+	return "ptrace"
+}
+
 type constructor struct{}
 
 func (*constructor) New(platform.Options) (platform.Platform, error) {

pkg/sentry/platform/systrap/systrap.go

@@ -349,6 +349,11 @@ func (*Systrap) ConcurrencyCount() int {
 	return maxSysmsgThreads
 }
 
+// Name implements platform.Platform.Name.
+func (*Systrap) Name() string {
+	return "systrap"
+}
+
 type constructor struct{}
 
 func (*constructor) New(opts platform.Options) (platform.Platform, error) {

pkg/sentry/state/state.go

@@ -93,7 +93,7 @@ func (opts SaveOpts) Save(ctx context.Context, k *kernel.Kernel, w *watchdog.Wat
 	if opts.Metadata == nil {
 		opts.Metadata = make(map[string]string)
 	}
-	addSaveMetadata(opts.Metadata)
+	addSaveMetadata(opts.Metadata, k.Platform.Name())
 
 	// Open the statefile.
 	wc, err := statefile.NewWriter(opts.Destination, opts.Key, opts.Metadata)

pkg/sentry/state/state_metadata.go

@@ -24,13 +24,14 @@ import (
 	"gvisor.dev/gvisor/pkg/log"
 )
 
-// The save metadata keys for timestamp.
+// The save metadata keys for timestamp and platform.
 const (
 	cpuUsage          = "cpu_usage"
 	metadataTimestamp = "timestamp"
+	MetadataPlatform  = "platform"
 )
 
-func addSaveMetadata(m map[string]string) {
+func addSaveMetadata(m map[string]string, platform string) {
 	t, err := CPUTime()
 	if err != nil {
 		log.Warningf("Error getting cpu time: %v", err)
@@ -45,4 +46,6 @@ func addSaveMetadata(m map[string]string) {
 	m[cpuUsage] = t.String()
 
 	m[metadataTimestamp] = fmt.Sprintf("%v", time.Now())
+
+	m[MetadataPlatform] = platform
 }

runsc/boot/controller.go

@@ -639,6 +639,11 @@ func (cm *containerManager) Restore(o *RestoreOpts, _ *struct{}) error {
 	if checkpointVersion != currentVersion {
 		return fmt.Errorf("runsc version does not match across checkpoint restore, checkpoint: %v current: %v", checkpointVersion, currentVersion)
 	}
+	checkpointPlatform := metadata[state.MetadataPlatform]
+	currentPlatform := cm.l.k.Platform.Name()
+	if checkpointPlatform != currentPlatform {
+		return fmt.Errorf("platform does not match across checkpoint restore, checkpoint: %v current: %v", checkpointPlatform, currentPlatform)
+	}
 	return cm.restorer.restoreContainerInfo(cm.l, &cm.l.root, timer.Fork("cont:root"))
 }