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// Copyright 2018 The gVisor Authors.
//
// 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.dev/gvisor/pkg/abi/linux"
)
// TODO(b/34161764): 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")
}
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