src/runtime/testdata/testprogcgo/sigstack.go

// Copyright 2017 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.

//go:build !plan9 && !windows
// +build !plan9,!windows

// Test handling of Go-allocated signal stacks when calling from
// C-created threads with and without signal stacks. (See issue
// #22930.)

package main

/*
#include <pthread.h>
#include <signal.h>
#include <stdio.h>
#include <stdlib.h>
#include <sys/mman.h>

#ifdef _AIX
// On AIX, SIGSTKSZ is too small to handle Go sighandler.
#define CSIGSTKSZ 0x4000
#else
#define CSIGSTKSZ SIGSTKSZ
#endif

extern void SigStackCallback();

static void* WithSigStack(void* arg __attribute__((unused))) {
	// Set up an alternate system stack.
	void* base = mmap(0, CSIGSTKSZ, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_ANON, -1, 0);
	if (base == MAP_FAILED) {
		perror("mmap failed");
		abort();
	}
	stack_t st = {}, ost = {};
	st.ss_sp = (char*)base;
	st.ss_flags = 0;
	st.ss_size = CSIGSTKSZ;
	if (sigaltstack(&st, &ost) < 0) {
		perror("sigaltstack failed");
		abort();
	}

	// Call Go.
	SigStackCallback();

	// Disable signal stack and protect it so we can detect reuse.
	if (ost.ss_flags & SS_DISABLE) {
		// Darwin libsystem has a bug where it checks ss_size
		// even if SS_DISABLE is set. (The kernel gets it right.)
		ost.ss_size = CSIGSTKSZ;
	}
	if (sigaltstack(&ost, NULL) < 0) {
		perror("sigaltstack restore failed");
		abort();
	}
	mprotect(base, CSIGSTKSZ, PROT_NONE);
	return NULL;
}

static void* WithoutSigStack(void* arg __attribute__((unused))) {
	SigStackCallback();
	return NULL;
}

static void DoThread(int sigstack) {
	pthread_t tid;
	if (sigstack) {
		pthread_create(&tid, NULL, WithSigStack, NULL);
	} else {
		pthread_create(&tid, NULL, WithoutSigStack, NULL);
	}
	pthread_join(tid, NULL);
}
*/
import "C"

func init() {
	register("SigStack", SigStack)
}

func SigStack() {
	C.DoThread(0)
	C.DoThread(1)
	C.DoThread(0)
	C.DoThread(1)
	println("OK")
}

var BadPtr *int

//export SigStackCallback
func SigStackCallback() {
	// Cause the Go signal handler to run.
	defer func() { recover() }()
	*BadPtr = 42
}