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/safecopy/safecopy.go

@@ -0,0 +1,151 @@
+// 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 safecopy provides an efficient implementation of functions to access
+// memory that may result in SIGSEGV or SIGBUS being sent to the accessor.
+package safecopy
+
+import (
+	"fmt"
+	"runtime"
+
+	"github.com/sagernet/gvisor/pkg/errors"
+	"github.com/sagernet/gvisor/pkg/errors/linuxerr"
+	"github.com/sagernet/gvisor/pkg/sighandling"
+	"golang.org/x/sys/unix"
+)
+
+// SegvError is returned when a safecopy function receives SIGSEGV.
+type SegvError struct {
+	// Addr is the address at which the SIGSEGV occurred.
+	Addr uintptr
+}
+
+// Error implements error.Error.
+func (e SegvError) Error() string {
+	return fmt.Sprintf("SIGSEGV at %#x", e.Addr)
+}
+
+// BusError is returned when a safecopy function receives SIGBUS.
+type BusError struct {
+	// Addr is the address at which the SIGBUS occurred.
+	Addr uintptr
+}
+
+// Error implements error.Error.
+func (e BusError) Error() string {
+	return fmt.Sprintf("SIGBUS at %#x", e.Addr)
+}
+
+// AlignmentError is returned when a safecopy function is passed an address
+// that does not meet alignment requirements.
+type AlignmentError struct {
+	// Addr is the invalid address.
+	Addr uintptr
+
+	// Alignment is the required alignment.
+	Alignment uintptr
+}
+
+// Error implements error.Error.
+func (e AlignmentError) Error() string {
+	return fmt.Sprintf("address %#x is not aligned to a %d-byte boundary", e.Addr, e.Alignment)
+}
+
+var (
+	// The begin and end addresses below are for the functions that are
+	// checked by the signal handler.
+	memcpyBegin               uintptr
+	memcpyEnd                 uintptr
+	memclrBegin               uintptr
+	memclrEnd                 uintptr
+	swapUint32Begin           uintptr
+	swapUint32End             uintptr
+	swapUint64Begin           uintptr
+	swapUint64End             uintptr
+	compareAndSwapUint32Begin uintptr
+	compareAndSwapUint32End   uintptr
+	loadUint32Begin           uintptr
+	loadUint32End             uintptr
+
+	// savedSigSegVHandler is a pointer to the SIGSEGV handler that was
+	// configured before we replaced it with our own. We still call into it
+	// when we get a SIGSEGV that is not interesting to us.
+	savedSigSegVHandler uintptr
+
+	// Same as above, but for SIGBUS signals.
+	savedSigBusHandler uintptr
+)
+
+// signalHandler is our replacement signal handler for SIGSEGV and SIGBUS
+// signals.
+func signalHandler()
+
+// addrOfSignalHandler returns the start address of signalHandler.
+//
+// See comment on addrOfMemcpy for more details.
+func addrOfSignalHandler() uintptr
+
+// FindEndAddress returns the end address (one byte beyond the last) of the
+// function that contains the specified address (begin).
+func FindEndAddress(begin uintptr) uintptr {
+	f := runtime.FuncForPC(begin)
+	if f != nil {
+		for p := begin; ; p++ {
+			g := runtime.FuncForPC(p)
+			if f != g {
+				return p
+			}
+		}
+	}
+	return begin
+}
+
+// initializeAddresses initializes the addresses used by the signal handler.
+func initializeAddresses() {
+	// The following functions are written in assembly language, so they won't
+	// be inlined by the existing compiler/linker. Tests will fail if this
+	// assumption is violated.
+	memcpyBegin = addrOfMemcpy()
+	memcpyEnd = FindEndAddress(memcpyBegin)
+	memclrBegin = addrOfMemclr()
+	memclrEnd = FindEndAddress(memclrBegin)
+	swapUint32Begin = addrOfSwapUint32()
+	swapUint32End = FindEndAddress(swapUint32Begin)
+	swapUint64Begin = addrOfSwapUint64()
+	swapUint64End = FindEndAddress(swapUint64Begin)
+	compareAndSwapUint32Begin = addrOfCompareAndSwapUint32()
+	compareAndSwapUint32End = FindEndAddress(compareAndSwapUint32Begin)
+	loadUint32Begin = addrOfLoadUint32()
+	loadUint32End = FindEndAddress(loadUint32Begin)
+	initializeArchAddresses()
+}
+
+func init() {
+	initializeAddresses()
+	if err := sighandling.ReplaceSignalHandler(unix.SIGSEGV, addrOfSignalHandler(), &savedSigSegVHandler); err != nil {
+		panic(fmt.Sprintf("Unable to set handler for SIGSEGV: %v", err))
+	}
+	if err := sighandling.ReplaceSignalHandler(unix.SIGBUS, addrOfSignalHandler(), &savedSigBusHandler); err != nil {
+		panic(fmt.Sprintf("Unable to set handler for SIGBUS: %v", err))
+	}
+	linuxerr.AddErrorUnwrapper(func(e error) (*errors.Error, bool) {
+		switch e.(type) {
+		case SegvError, BusError, AlignmentError:
+			return linuxerr.EFAULT, true
+		default:
+			return nil, false
+		}
+	})
+}