Check in gVisor.

PiperOrigin-RevId: 194583126
Change-Id: Ica1d8821a90f74e7e745962d71801c598c652463

1 files changed, 74 insertions, 0 deletions

diff --git a/pkg/sentry/sighandling/sighandling_unsafe.go b/pkg/sentry/sighandling/sighandling_unsafe.go
new file mode 100644
index 000000000..a455b919f
--- /dev/null
+++ b/pkg/sentry/sighandling/sighandling_unsafe.go
@@ -0,0 +1,74 @@
+// 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 sighandling
+
+import (
+	"fmt"
+	"runtime"
+	"syscall"
+	"unsafe"
+
+	"gvisor.googlesource.com/gvisor/pkg/abi/linux"
+)
+
+// TODO: Move to pkg/abi/linux along with definitions in
+// pkg/sentry/arch.
+type sigaction struct {
+	handler  uintptr
+	flags    uint64
+	restorer uintptr
+	mask     uint64
+}
+
+// IgnoreChildStop sets the SA_NOCLDSTOP flag, causing child processes to not
+// generate SIGCHLD when they stop.
+func IgnoreChildStop() error {
+	var sa sigaction
+
+	// Get the existing signal handler information, and set the flag.
+	if _, _, e := syscall.RawSyscall6(syscall.SYS_RT_SIGACTION, uintptr(syscall.SIGCHLD), 0, uintptr(unsafe.Pointer(&sa)), linux.SignalSetSize, 0, 0); e != 0 {
+		return e
+	}
+	sa.flags |= linux.SA_NOCLDSTOP
+	if _, _, e := syscall.RawSyscall6(syscall.SYS_RT_SIGACTION, uintptr(syscall.SIGCHLD), uintptr(unsafe.Pointer(&sa)), 0, linux.SignalSetSize, 0, 0); e != 0 {
+		return e
+	}
+
+	return nil
+}
+
+// dieFromSignal kills the current process with sig.
+//
+// Preconditions: The default action of sig is termination.
+func dieFromSignal(sig linux.Signal) {
+	runtime.LockOSThread()
+	defer runtime.UnlockOSThread()
+
+	sa := sigaction{handler: linux.SIG_DFL}
+	if _, _, e := syscall.RawSyscall6(syscall.SYS_RT_SIGACTION, uintptr(sig), uintptr(unsafe.Pointer(&sa)), 0, linux.SignalSetSize, 0, 0); e != 0 {
+		panic(fmt.Sprintf("rt_sigaction failed: %v", e))
+	}
+
+	set := linux.MakeSignalSet(sig)
+	if _, _, e := syscall.RawSyscall6(syscall.SYS_RT_SIGPROCMASK, linux.SIG_UNBLOCK, uintptr(unsafe.Pointer(&set)), 0, linux.SignalSetSize, 0, 0); e != 0 {
+		panic(fmt.Sprintf("rt_sigprocmask failed: %v", e))
+	}
+
+	if err := syscall.Tgkill(syscall.Getpid(), syscall.Gettid(), syscall.Signal(sig)); err != nil {
+		panic(fmt.Sprintf("tgkill failed: %v", err))
+	}
+
+	panic("failed to die")
+}