Move ThreadGroupIDFromContext to kernel/auth.

This function doesn't belong in the global context package. Move to a more
suitable package to break the dependency cycle.

PiperOrigin-RevId: 406942122

pkg/context/context.go

@@ -29,26 +29,6 @@ import (
 	"gvisor.dev/gvisor/pkg/log"
 )
 
-type contextID int
-
-// Globally accessible values from a context. These keys are defined in the
-// context package to resolve dependency cycles by not requiring the caller to
-// import packages usually required to get these information.
-const (
-	// CtxThreadGroupID is the current thread group ID when a context represents
-	// a task context. The value is represented as an int32.
-	CtxThreadGroupID contextID = iota
-)
-
-// ThreadGroupIDFromContext returns the current thread group ID when ctx
-// represents a task context.
-func ThreadGroupIDFromContext(ctx Context) (tgid int32, ok bool) {
-	if tgid := ctx.Value(CtxThreadGroupID); tgid != nil {
-		return tgid.(int32), true
-	}
-	return 0, false
-}
-
 // A Context represents a thread of execution (hereafter "goroutine" to reflect
 // Go idiosyncrasy). It carries state associated with the goroutine across API
 // boundaries.

pkg/sentry/kernel/auth/context.go

@@ -24,6 +24,10 @@ type contextID int
 const (
 	// CtxCredentials is a Context.Value key for Credentials.
 	CtxCredentials contextID = iota
+
+	// CtxThreadGroupID is the current thread group ID when a context represents
+	// a task context. The value is represented as an int32.
+	CtxThreadGroupID contextID = iota
 )
 
 // CredentialsFromContext returns a copy of the Credentials used by ctx, or a
@@ -35,6 +39,15 @@ func CredentialsFromContext(ctx context.Context) *Credentials {
 	return NewAnonymousCredentials()
 }
 
+// ThreadGroupIDFromContext returns the current thread group ID when ctx
+// represents a task context.
+func ThreadGroupIDFromContext(ctx context.Context) (tgid int32, ok bool) {
+	if tgid := ctx.Value(CtxThreadGroupID); tgid != nil {
+		return tgid.(int32), true
+	}
+	return 0, false
+}
+
 // ContextWithCredentials returns a copy of ctx carrying creds.
 func ContextWithCredentials(ctx context.Context, creds *Credentials) context.Context {
 	return &authContext{ctx, creds}

pkg/sentry/kernel/mq/mq.go

@@ -399,7 +399,7 @@ func (q *Queue) Flush(ctx context.Context) {
 	q.mu.Lock()
 	defer q.mu.Unlock()
 
-	pid, ok := context.ThreadGroupIDFromContext(ctx)
+	pid, ok := auth.ThreadGroupIDFromContext(ctx)
 	if ok {
 		if q.subscriber != nil && pid == q.subscriber.pid {
 			q.subscriber = nil

pkg/sentry/kernel/shm/shm.go

@@ -444,7 +444,7 @@ func (s *Shm) AddMapping(ctx context.Context, _ memmap.MappingSpace, _ hostarch.
 	s.mu.Lock()
 	defer s.mu.Unlock()
 	s.attachTime = ktime.NowFromContext(ctx)
-	if pid, ok := context.ThreadGroupIDFromContext(ctx); ok {
+	if pid, ok := auth.ThreadGroupIDFromContext(ctx); ok {
 		s.lastAttachDetachPID = pid
 	} else {
 		// AddMapping is called during a syscall, so ctx should always be a task
@@ -468,7 +468,7 @@ func (s *Shm) RemoveMapping(ctx context.Context, _ memmap.MappingSpace, _ hostar
 
 	// If called from a non-task context we also won't have a threadgroup
 	// id. Silently skip updating the lastAttachDetachPid in that case.
-	if pid, ok := context.ThreadGroupIDFromContext(ctx); ok {
+	if pid, ok := auth.ThreadGroupIDFromContext(ctx); ok {
 		s.lastAttachDetachPID = pid
 	} else {
 		log.Debugf("Couldn't obtain pid when removing mapping to %s, not updating the last detach pid.", s.debugLocked())

pkg/sentry/kernel/task_context.go

@@ -86,7 +86,7 @@ func (t *Task) contextValue(key interface{}, isTaskGoroutine bool) interface{} {
 		return t
 	case auth.CtxCredentials:
 		return t.creds.Load()
-	case context.CtxThreadGroupID:
+	case auth.CtxThreadGroupID:
 		return int32(t.tg.ID())
 	case fs.CtxRoot:
 		if !isTaskGoroutine {