Add context.FullStateChanged()

It indicates that the Sentry has changed the state of the thread and
next calls of PullFullState() has to do nothing.

PiperOrigin-RevId: 325567415

pkg/sentry/kernel/ptrace.go

@@ -1063,7 +1063,7 @@ func (t *Task) Ptrace(req int64, pid ThreadID, addr, data usermem.Addr) error {
 		if err != nil {
 			return err
 		}
-		t.p.FloatingPointStateChanged()
+		t.p.FullStateChanged()
 		ar.End -= usermem.Addr(n)
 		return t.CopyOutIovecs(data, usermem.AddrRangeSeqOf(ar))
 

pkg/sentry/kernel/task_exec.go

@@ -226,6 +226,7 @@ func (r *runSyscallAfterExecStop) execute(t *Task) taskRunState {
 	t.tc = *r.tc
 	t.mu.Unlock()
 	t.unstopVforkParent()
+	t.p.FullStateChanged()
 	// NOTE(b/30316266): All locks must be dropped prior to calling Activate.
 	t.MemoryManager().Activate(t)
 

pkg/sentry/kernel/task_signals.go

@@ -280,7 +280,7 @@ func (t *Task) deliverSignalToHandler(info *arch.SignalInfo, act arch.SignalAct)
 	if err := t.Arch().SignalSetup(st, &act, info, &alt, mask); err != nil {
 		return err
 	}
-	t.p.FloatingPointStateChanged()
+	t.p.FullStateChanged()
 	t.haveSavedSignalMask = false
 
 	// Add our signal mask.
@@ -312,7 +312,7 @@ func (t *Task) SignalReturn(rt bool) (*SyscallControl, error) {
 
 	// Restore our signal mask. SIGKILL and SIGSTOP should not be blocked.
 	t.SetSignalMask(sigset &^ UnblockableSignals)
-	t.p.FloatingPointStateChanged()
+	t.p.FullStateChanged()
 
 	return ctrlResume, nil
 }

pkg/sentry/platform/kvm/context.go

@@ -91,8 +91,8 @@ func (c *context) Interrupt() {
 // Release implements platform.Context.Release().
 func (c *context) Release() {}
 
-// FloatingPointStateChanged implements platform.Context.FloatingPointStateChanged.
-func (c *context) FloatingPointStateChanged() {}
+// FullStateChanged implements platform.Context.FullStateChanged.
+func (c *context) FullStateChanged() {}
 
 // PullFullState implements platform.Context.PullFullState.
 func (c *context) PullFullState(as platform.AddressSpace, ac arch.Context) {}

pkg/sentry/platform/platform.go

@@ -171,14 +171,20 @@ type Context interface {
 	// Preconditions: The caller must be running on the task goroutine.
 	PullFullState(as AddressSpace, ac arch.Context)
 
-	// FloatingPointStateChanged forces restoring a full state of the application thread.
+	// FullStateChanged() indicates that a thread state has been changed by
+	// the Sentry. This happens in case of the rt_sigreturn, execve, etc.
 	//
-	// A platform can support lazy loading/restoring of a thread state.
-	// This means that if the Sentry has not changed a thread state,
+	// First, it indicates that the Sentry has the full state of the thread
+	// and PullFullState() has to do nothing if it is called after
+	// FullStateChanged().
+	//
+	// Second, it forces restoring the full state of the application
+	// thread. A platform can support lazy loading/restoring of a thread
+	// state. This means that if the Sentry has not changed a thread state,
 	// the platform may not restore it.
 	//
 	// Preconditions: The caller must be running on the task goroutine.
-	FloatingPointStateChanged()
+	FullStateChanged()
 
 	// Interrupt interrupts a concurrent call to Switch(), causing it to return
 	// ErrContextInterrupt.

pkg/sentry/platform/ptrace/ptrace.go

@@ -182,8 +182,8 @@ func (c *context) Interrupt() {
 // Release implements platform.Context.Release().
 func (c *context) Release() {}
 
-// FloatingPointStateChanged implements platform.Context.FloatingPointStateChanged.
-func (c *context) FloatingPointStateChanged() {}
+// FullStateChanged implements platform.Context.FullStateChanged.
+func (c *context) FullStateChanged() {}
 
 // PullFullState implements platform.Context.PullFullState.
 func (c *context) PullFullState(as platform.AddressSpace, ac arch.Context) {}