systrap: enabled the context decoupling feature by default

PiperOrigin-RevId: 519880828

pkg/sentry/platform/systrap/context_decoupling_disable.go

@@ -12,8 +12,8 @@
 // See the License for the specific language governing permissions and
 // limitations under the License.
 
-//go:build !context_decoupling
-// +build !context_decoupling
+//go:build context_decoupling_disabled
+// +build context_decoupling_disabled
 
 package systrap
 

pkg/sentry/platform/systrap/context_decoupling_enable.go

@@ -12,8 +12,8 @@
 // See the License for the specific language governing permissions and
 // limitations under the License.
 
-//go:build context_decoupling
-// +build context_decoupling
+//go:build !context_decoupling_disabled
+// +build !context_decoupling_disabled
 
 package systrap
 

pkg/sentry/platform/systrap/subprocess.go

@@ -764,6 +764,7 @@ func (s *subprocess) switchToApp(c *context, ac *arch.Context64) (isSyscall bool
 	// Copy register state locally.
 	regs.PtraceRegs = ctx.shared.Regs
 	retrieveArchSpecificState(ctx.shared, ac)
+	c.needToPullFullState = true
 	// We have a signal. We verify however, that the signal was
 	// either delivered from the kernel or from this process. We
 	// don't respect other signals.

pkg/sentry/platform/systrap/systrap.go

@@ -170,8 +170,6 @@ func (c *context) FullStateChanged() {
 
 // Switch runs the provided context in the given address space.
 func (c *context) Switch(ctx pkgcontext.Context, mm platform.MemoryManager, ac *arch.Context64, cpu int32) (*linux.SignalInfo, hostarch.AccessType, error) {
-	c.needToPullFullState = true
-
 	as := mm.AddressSpace()
 	s := as.(*subprocess)
 	if err := s.activateContext(c); err != nil {