snapshot: sagernet/gvisor v0.0.0-20250811.0-sing-box-mod.1

Содержимое пина, зафиксированного в go.mod sing-box-lx, одним коммитом
без истории. Полная история SagerNet/gvisor — 1.45 ГБ и клонируется в
каждой CI-джобе; наша дельта — одна вставка в одну функцию, история для
неё не нужна.

Module path github.com/sagernet/gvisor сохранён намеренно: на него
опирается replace-директива суперпроекта.

Патч поверх — отдельным коммитом, чтобы дельта читалась одним git show
и переносилась на новый пин копированием.

SPECS/TASKS/048-GVISOR_HANDSHAKE_NIL_CRASH

pkg/sighandling/sighandling_linux_unsafe.go

@@ -0,0 +1,103 @@
+// 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.
+
+//go:build linux
+// +build linux
+
+package sighandling
+
+import (
+	"fmt"
+	"os"
+	"unsafe"
+
+	"github.com/sagernet/gvisor/pkg/abi/linux"
+	"golang.org/x/sys/unix"
+)
+
+// IgnoreChildStop sets the SA_NOCLDSTOP flag, causing child processes to not
+// generate SIGCHLD when they stop.
+func IgnoreChildStop() error {
+	var sa linux.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
+}
+
+// ReplaceSignalHandler replaces the existing signal handler for the provided
+// signal with the function pointer at `handler`. This bypasses the Go runtime
+// signal handlers, and should only be used for low-level signal handlers where
+// use of signal.Notify is not appropriate.
+//
+// It stores the value of the previously set handler in previous.
+func ReplaceSignalHandler(sig unix.Signal, handler uintptr, previous *uintptr) error {
+	var sa linux.SigAction
+	const maskLen = 8
+
+	// Get the existing signal handler information, and save the current
+	// handler. Once we replace it, we will use this pointer to fall back to
+	// it when we receive other signals.
+	if _, _, e := unix.RawSyscall6(unix.SYS_RT_SIGACTION, uintptr(sig), 0, uintptr(unsafe.Pointer(&sa)), maskLen, 0, 0); e != 0 {
+		return e
+	}
+
+	// Fail if there isn't a previous handler.
+	if sa.Handler == 0 {
+		return fmt.Errorf("previous handler for signal %x isn't set", sig)
+	}
+
+	*previous = uintptr(sa.Handler)
+
+	// Install our own handler.
+	sa.Handler = uint64(handler)
+	if _, _, e := unix.RawSyscall6(unix.SYS_RT_SIGACTION, uintptr(sig), uintptr(unsafe.Pointer(&sa)), 0, maskLen, 0, 0); e != 0 {
+		return e
+	}
+
+	return nil
+}
+
+// KillItself sends SIGKILL to the current process, bypassing the init process
+// restriction.
+//
+// The standard `kill(getpid(), SIGKILL)` syscall doesn't work when the current
+// process is the init process within its PID namespace. This is a "known"
+// Linux feature.
+//
+// This function uses the rt_tgqueueinfo syscall to send a "kernel-generated"
+// SIGKILL.
+func KillItself() error {
+	pid := os.Getpid()
+	tid, _, _ := unix.RawSyscall(unix.SYS_GETTID, 0, 0, 0)
+	info := linux.SignalInfo{Code: linux.SI_KERNEL}
+	// The current thread can send a fake kernel siginfo to itself.
+	if _, _, e := unix.RawSyscall6(
+		unix.SYS_RT_TGSIGQUEUEINFO,
+		uintptr(pid), uintptr(tid),
+		uintptr(linux.SIGKILL),
+		uintptr(unsafe.Pointer(&info)),
+		0, 0,
+	); e != 0 {
+		return e
+	}
+	panic("unreachable")
+}