kvm: handle exit reasons even under EINTR.

In the case of other signals (preemption), inject a normal bounce and
defer the signal until the vCPU has been returned from guest mode.

PiperOrigin-RevId: 303799678

2 files changed, 6 insertions, 4 deletions

diff --git a/pkg/safecopy/safecopy.go b/pkg/safecopy/safecopy.go
index 2fb7e5809..521f1a82d 100644
--- a/pkg/safecopy/safecopy.go
+++ b/pkg/safecopy/safecopy.go
@@ -127,10 +127,10 @@ func initializeAddresses() {
 
 func init() {
 	initializeAddresses()
-	if err := ReplaceSignalHandler(syscall.SIGSEGV, reflect.ValueOf(signalHandler).Pointer(), &savedSigSegVHandler); err != nil {
+	if err := ReplaceSignalHandler(syscall.SIGSEGV, reflect.ValueOf(signalHandler).Pointer(), &savedSigSegVHandler, 0); err != nil {
 		panic(fmt.Sprintf("Unable to set handler for SIGSEGV: %v", err))
 	}
-	if err := ReplaceSignalHandler(syscall.SIGBUS, reflect.ValueOf(signalHandler).Pointer(), &savedSigBusHandler); err != nil {
+	if err := ReplaceSignalHandler(syscall.SIGBUS, reflect.ValueOf(signalHandler).Pointer(), &savedSigBusHandler, 0); err != nil {
 		panic(fmt.Sprintf("Unable to set handler for SIGBUS: %v", err))
 	}
 	syserror.AddErrorUnwrapper(func(e error) (syscall.Errno, bool) {
diff --git a/pkg/safecopy/safecopy_unsafe.go b/pkg/safecopy/safecopy_unsafe.go
index 41dd567f3..b15b920fe 100644
--- a/pkg/safecopy/safecopy_unsafe.go
+++ b/pkg/safecopy/safecopy_unsafe.go
@@ -324,11 +324,13 @@ func errorFromFaultSignal(addr uintptr, sig int32) error {
 //
 // It stores the value of the previously set handler in previous.
 //
+// The extraMask parameter is OR'ed into the existing signal handler mask.
+//
 // This function will be called on initialization in order to install safecopy
 // handlers for appropriate signals. These handlers will call the previous
 // handler however, and if this is function is being used externally then the
 // same courtesy is expected.
-func ReplaceSignalHandler(sig syscall.Signal, handler uintptr, previous *uintptr) error {
+func ReplaceSignalHandler(sig syscall.Signal, handler uintptr, previous *uintptr, extraMask uint64) error {
 	var sa struct {
 		handler  uintptr
 		flags    uint64
@@ -348,10 +350,10 @@ func ReplaceSignalHandler(sig syscall.Signal, handler uintptr, previous *uintptr
 	if sa.handler == 0 {
 		return fmt.Errorf("previous handler for signal %x isn't set", sig)
 	}
-
 	*previous = sa.handler
 
 	// Install our own handler.
+	sa.mask |= extraMask
 	sa.handler = handler
 	if _, _, e := syscall.RawSyscall6(syscall.SYS_RT_SIGACTION, uintptr(sig), uintptr(unsafe.Pointer(&sa)), 0, maskLen, 0, 0); e != 0 {
 		return e