Check in gVisor.

PiperOrigin-RevId: 194583126
Change-Id: Ica1d8821a90f74e7e745962d71801c598c652463

1 files changed, 69 insertions, 0 deletions

diff --git a/pkg/sentry/kernel/signal.go b/pkg/sentry/kernel/signal.go
new file mode 100644
index 000000000..8edd05cdf
--- /dev/null
+++ b/pkg/sentry/kernel/signal.go
@@ -0,0 +1,69 @@
+// Copyright 2018 Google Inc.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package kernel
+
+import (
+	"gvisor.googlesource.com/gvisor/pkg/abi/linux"
+	"gvisor.googlesource.com/gvisor/pkg/log"
+	"gvisor.googlesource.com/gvisor/pkg/sentry/arch"
+	"gvisor.googlesource.com/gvisor/pkg/sentry/platform"
+)
+
+// SignalPanic is used to panic the running threads. It is a signal which
+// cannot be used by the application: it must be caught and ignored by the
+// runtime (in order to catch possible races).
+const SignalPanic = linux.SIGUSR2
+
+// sendExternalSignal is called when an asynchronous signal is sent to the
+// sentry ("in sentry context"). On some platforms, it may also be called when
+// an asynchronous signal is sent to sandboxed application threads ("in
+// application context").
+//
+// context is used only for debugging to differentiate these cases.
+//
+// Returns false if signal could not be sent because the Kernel is not fully
+// initialized yet.
+func (k *Kernel) sendExternalSignal(info *arch.SignalInfo, context string) bool {
+	switch linux.Signal(info.Signo) {
+	case platform.SignalInterrupt:
+		// Assume that a call to platform.Context.Interrupt() misfired.
+		return true
+
+	case SignalPanic:
+		// SignalPanic is also specially handled in sentry setup to ensure that
+		// it causes a panic even after tasks exit, but SignalPanic may also
+		// be sent here if it is received while in app context.
+		panic("Signal-induced panic")
+
+	default:
+		log.Infof("Received external signal %d in %s context", info.Signo, context)
+		if k.globalInit == nil {
+			log.Warningf("Received external signal %d before init created", info.Signo)
+			return false
+		}
+		k.globalInit.SendSignal(info)
+	}
+
+	return true
+}
+
+// sigPriv returns a SignalInfo representing a signal sent by the sentry. (The
+// name reflects its equivalence to Linux's SEND_SIG_PRIV.)
+func sigPriv(sig linux.Signal) *arch.SignalInfo {
+	return &arch.SignalInfo{
+		Signo: int32(sig),
+		Code:  arch.SignalInfoKernel,
+	}
+}