usr/src/lib/csu.vax/crt0.c

/*-
 * Copyright (c) 1982 The Regents of the University of California.
 * All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in the
 *    documentation and/or other materials provided with the distribution.
 * 3. All advertising materials mentioning features or use of this software
 *    must display the following acknowledgement:
 *      This product includes software developed by the University of
 *      California, Berkeley and its contributors.
 * 4. Neither the name of the University nor the names of its contributors
 *    may be used to endorse or promote products derived from this software
 *    without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
 * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
 * SUCH DAMAGE.
 */

#ifndef lint
static char sccsid[] = "@(#)crt0.c      5.10 (Berkeley) 7/3/91";
#endif /* not lint */

/*
 *      C start up routine.
 *      Robert Henry, UCB, 20 Oct 81
 *
 *      We make the following (true) assumptions:
 *      1) when the kernel calls start, it does a jump to location 2,
 *      and thus avoids the register save mask.  We are NOT called
 *      with a calls!  see sys1.c:setregs().
 *      2) The only register variable that we can trust is sp,
 *      which points to the base of the kernel calling frame.
 *      Do NOT believe the documentation in exec(2) regarding the
 *      values of fp and ap.
 */

char **environ = (char **)0;
static int fd;

extern  unsigned char   etext;
extern  unsigned char   eprol asm ("eprol");
extern                  start() asm("start");

/*
 * Two kluges: store sp at entry in environ, and
 * install 16 bits of 0 at location 0 (a zero register save mask).
 * These two hacks remove limits on the use of local
 * and register variables in start().
 */
asm(".text; .word 0; movl sp,_environ; jbr start+2");

start()
{
        struct kframe {
                int     kargc;
                char    *kargv[1];      /* size depends on kargc */
                char    kargstr[1];     /* size varies */
                char    kenvstr[1];     /* size varies */
        };
        register struct kframe *kfp;
        register char **targv;
        register char **argv;
        extern int errno;
        extern void _mcleanup();

#ifdef lint
        kfp = 0;
        initcode = initcode = 0;
#else not lint
        kfp = (struct kframe *) environ;
#endif not lint
        for (argv = targv = &kfp->kargv[0]; *targv++; /* void */)
                /* void */ ;
        if (targv >= (char **)(*argv))
                --targv;
        environ = targv;
asm("eprol:");

#ifdef paranoid
        /*
         * The standard I/O library assumes that file descriptors 0, 1, and 2
         * are open. If one of these descriptors is closed prior to the start
         * of the process, I/O gets very confused. To avoid this problem, we
         * insure that the first three file descriptors are open before calling
         * main(). Normally this is undefined, as it adds two unnecessary
         * system calls.
         */
        do      {
                fd = open("/dev/null", 2);
        } while (fd >= 0 && fd < 3);
        close(fd);
#endif paranoid

#ifdef MCRT0
        atexit(_mcleanup);
        monstartup(&eprol, &etext);
#endif MCRT0
        errno = 0;
        exit(main(kfp->kargc, argv, environ));
}

#ifdef CRT0
/*
 * null mcount and moncontrol,
 * just in case some routine is compiled for profiling
 */
moncontrol(val)
        int val;
{

}
asm(".globl mcount");
asm("mcount: rsb");
#endif CRT0