usr/src/lib/csu/i386/crt0.c

/*-
 * Copyright (c) 1990 The Regents of the University of California.
 * All rights reserved.
 *
 * %sccs.include.redist.c%
 */

#ifndef lint
static char sccsid[] = "@(#)crt0.c      5.5 (Berkeley) %G%";
#endif /* not lint */

/*
 *      C start up routine.
 *      Robert Henry, UCB, 20 Oct 81
 *
 *      We make the following (true) assumption:
 *      1) The only register variable that we can trust is ebp,
 *      which points to the base of the kernel calling frame.
 */

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

asm(".text");
asm(".long 0xc000c000");

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

start()
{
        struct kframe {
                int     kargc;
                char    *kargv[1];      /* size depends on kargc */
                char    kargstr[1];     /* size varies */
                char    kenvstr[1];     /* size varies */
        };
        /*
         *      ALL REGISTER VARIABLES!!!
         */
        register struct kframe *kfp;    /* r10 */
        register char **targv;
        register char **argv;
        extern int errno;

#ifdef lint
        kfp = 0;
        initcode = initcode = 0;
#else not lint
        asm("lea 4(%ebp),%ebx");        /* catch it quick */
#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
        monstartup(&eprol, &etext);
#endif MCRT0
        errno = 0;
        exit(main(kfp->kargc, argv, environ));
}

#ifdef MCRT0
/*ARGSUSED*/
exit(code)
        register int code;
{
        monitor(0);
        _cleanup();
        asm("pushl 8(%ebp)") ;
        asm("movl $1,%eax");
        asm(".byte 0x9a; .long 0; .word 0");
}
#endif MCRT0

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

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