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https://github.com/golang/go
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7aeaad5c86
This avoids an incorrect msan uninitialized memory report when using runtime.SetCgoTraceback when a signal occurs while the fifth argument register is undefined. See the issue for more details. Fixes #47543 Change-Id: I3d1b673e2c93471ccdae0171a99b88b5a6062840 Reviewed-on: https://go-review.googlesource.com/c/go/+/339902 Trust: Ian Lance Taylor <iant@golang.org> Run-TryBot: Ian Lance Taylor <iant@golang.org> TryBot-Result: Go Bot <gobot@golang.org> Reviewed-by: Austin Clements <austin@google.com>
110 lines
2.7 KiB
Go
110 lines
2.7 KiB
Go
// Copyright 2021 The Go Authors. All rights reserved.
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// Use of this source code is governed by a BSD-style
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// license that can be found in the LICENSE file.
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package main
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/*
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#include <pthread.h>
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#include <signal.h>
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#include <stdint.h>
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#include <sanitizer/msan_interface.h>
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// cgoTracebackArg is the type of the argument passed to msanGoTraceback.
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struct cgoTracebackArg {
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uintptr_t context;
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uintptr_t sigContext;
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uintptr_t* buf;
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uintptr_t max;
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};
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// msanGoTraceback is registered as the cgo traceback function.
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// This will be called when a signal occurs.
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void msanGoTraceback(void* parg) {
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struct cgoTracebackArg* arg = (struct cgoTracebackArg*)(parg);
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arg->buf[0] = 0;
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}
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// msanGoWait will be called with all registers undefined as far as
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// msan is concerned. It just waits for a signal.
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// Because the registers are msan-undefined, the signal handler will
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// be invoked with all registers msan-undefined.
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__attribute__((noinline))
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void msanGoWait(unsigned long a1, unsigned long a2, unsigned long a3, unsigned long a4, unsigned long a5, unsigned long a6) {
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sigset_t mask;
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sigemptyset(&mask);
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sigsuspend(&mask);
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}
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// msanGoSignalThread is the thread ID of the msanGoLoop thread.
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static pthread_t msanGoSignalThread;
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// msanGoSignalThreadSet is used to record that msanGoSignalThread
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// has been initialized. This is accessed atomically.
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static int32_t msanGoSignalThreadSet;
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// uninit is explicitly poisoned, so that we can make all registers
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// undefined by calling msanGoWait.
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static unsigned long uninit;
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// msanGoLoop loops calling msanGoWait, with the arguments passed
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// such that msan thinks that they are undefined. msan permits
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// undefined values to be used as long as they are not used to
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// for conditionals or for memory access.
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void msanGoLoop() {
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int i;
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msanGoSignalThread = pthread_self();
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__atomic_store_n(&msanGoSignalThreadSet, 1, __ATOMIC_SEQ_CST);
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// Force uninit to be undefined for msan.
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__msan_poison(&uninit, sizeof uninit);
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for (i = 0; i < 100; i++) {
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msanGoWait(uninit, uninit, uninit, uninit, uninit, uninit);
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}
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}
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// msanGoReady returns whether msanGoSignalThread is set.
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int msanGoReady() {
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return __atomic_load_n(&msanGoSignalThreadSet, __ATOMIC_SEQ_CST) != 0;
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}
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// msanGoSendSignal sends a signal to the msanGoLoop thread.
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void msanGoSendSignal() {
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pthread_kill(msanGoSignalThread, SIGWINCH);
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}
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*/
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import "C"
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import (
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"runtime"
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"time"
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)
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func main() {
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runtime.SetCgoTraceback(0, C.msanGoTraceback, nil, nil)
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c := make(chan bool)
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go func() {
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defer func() { c <- true }()
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C.msanGoLoop()
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}()
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for C.msanGoReady() == 0 {
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time.Sleep(time.Microsecond)
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}
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loop:
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for {
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select {
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case <-c:
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break loop
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default:
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C.msanGoSendSignal()
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time.Sleep(time.Microsecond)
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}
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}
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}
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