// 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 (
	"unsafe"

	"golang.org/x/sys/unix"
	"gvisor.dev/gvisor/pkg/abi/linux"
)

// FIXME(gvisor.dev/issue/214): 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 := unix.RawSyscall6(unix.SYS_RT_SIGACTION, uintptr(unix.SIGCHLD), 0, uintptr(unsafe.Pointer(&sa)), linux.SignalSetSize, 0, 0); e != 0 {
		return e
	}
	sa.flags |= linux.SA_NOCLDSTOP
	if _, _, e := unix.RawSyscall6(unix.SYS_RT_SIGACTION, uintptr(unix.SIGCHLD), uintptr(unsafe.Pointer(&sa)), 0, linux.SignalSetSize, 0, 0); e != 0 {
		return e
	}

	return nil
}