/*      $OpenBSD: syscallwx.c,v 1.2 2023/01/09 11:50:01 anton Exp $     */
/*
 * Copyright (c) 2018 Todd Mortimer <mortimer@openbsd.org>
 * Copyright (c) 2019 Alexander Bluhm <bluhm@openbsd.org>
 *
 * Permission to use, copy, modify, and distribute this software for any
 * purpose with or without fee is hereby granted, provided that the above
 * copyright notice and this permission notice appear in all copies.
 *
 * THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
 * WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
 * MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
 * ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
 * WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
 * ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
 * OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
 */

#include <sys/mman.h>

#include <err.h>
#include <signal.h>
#include <string.h>
#include <unistd.h>

extern void gadget_getpid(void);
static void handler(int);

int
main(int argc, char *argv[])
{
        union {
                void *p;
                void (*gadget)(void);
        } addr;
        int psz = getpagesize();

        if (signal(SIGSEGV, handler) == SIG_ERR)
                err(1, "signal");

        addr.p = mmap(NULL, psz, PROT_READ | PROT_WRITE | PROT_EXEC,
            MAP_PRIVATE | MAP_ANON, -1, 0);
        if (addr.p == NULL)
                err(1, "mmap");
        memcpy(addr.p, gadget_getpid, psz);
        addr.gadget();
        return 3;
}

static void
handler(int signum)
{
        _exit(0);
}