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// Copyright 2021 The Go Authors. All rights reserved.
// Use of this source code is governed by a BSD-style
// license that can be found in the LICENSE file.
package main
/*
#include <pthread.h>
#include <signal.h>
#include <stdint.h>
#include <sanitizer/msan_interface.h>
// cgoTracebackArg is the type of the argument passed to msanGoTraceback.
struct cgoTracebackArg {
uintptr_t context;
uintptr_t sigContext;
uintptr_t* buf;
uintptr_t max;
};
// msanGoTraceback is registered as the cgo traceback function.
// This will be called when a signal occurs.
void msanGoTraceback(void* parg) {
struct cgoTracebackArg* arg = (struct cgoTracebackArg*)(parg);
arg->buf[0] = 0;
}
// msanGoWait will be called with all registers undefined as far as
// msan is concerned. It just waits for a signal.
// Because the registers are msan-undefined, the signal handler will
// be invoked with all registers msan-undefined.
__attribute__((noinline))
void msanGoWait(unsigned long a1, unsigned long a2, unsigned long a3, unsigned long a4, unsigned long a5, unsigned long a6) {
sigset_t mask;
sigemptyset(&mask);
sigsuspend(&mask);
}
// msanGoSignalThread is the thread ID of the msanGoLoop thread.
static pthread_t msanGoSignalThread;
// msanGoSignalThreadSet is used to record that msanGoSignalThread
// has been initialized. This is accessed atomically.
static int32_t msanGoSignalThreadSet;
// uninit is explicitly poisoned, so that we can make all registers
// undefined by calling msanGoWait.
static unsigned long uninit;
// msanGoLoop loops calling msanGoWait, with the arguments passed
// such that msan thinks that they are undefined. msan permits
// undefined values to be used as long as they are not used to
// for conditionals or for memory access.
void msanGoLoop() {
int i;
msanGoSignalThread = pthread_self();
__atomic_store_n(&msanGoSignalThreadSet, 1, __ATOMIC_SEQ_CST);
// Force uninit to be undefined for msan.
__msan_poison(&uninit, sizeof uninit);
for (i = 0; i < 100; i++) {
msanGoWait(uninit, uninit, uninit, uninit, uninit, uninit);
}
}
// msanGoReady returns whether msanGoSignalThread is set.
int msanGoReady() {
return __atomic_load_n(&msanGoSignalThreadSet, __ATOMIC_SEQ_CST) != 0;
}
// msanGoSendSignal sends a signal to the msanGoLoop thread.
void msanGoSendSignal() {
pthread_kill(msanGoSignalThread, SIGWINCH);
}
*/
import "C"
import (
"runtime"
"time"
)
func main() {
runtime.SetCgoTraceback(0, C.msanGoTraceback, nil, nil)
c := make(chan bool)
go func() {
defer func() { c <- true }()
C.msanGoLoop()
}()
for C.msanGoReady() == 0 {
time.Sleep(time.Microsecond)
}
loop:
for {
select {
case <-c:
break loop
default:
C.msanGoSendSignal()
time.Sleep(time.Microsecond)
}
}
}
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