usr/src/lib/csu.hp300/crt0.c

/*
 * Copyright (c) 1980 Regents of the University of California.
 * All rights reserved.  The Berkeley software License Agreement
 * specifies the terms and conditions for redistribution.
 */

#if defined(LIBC_SCCS) && !defined(lint)
static char sccsid[] = "@(#)crt0.c      5.3 (Berkeley) 3/9/86";
#endif LIBC_SCCS and 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.
 *      3) We can allocate as many register variables as we want,
 *      and don't have to save them for anybody.
 *      4) Because of the ways that asm's work, we can't have
 *      any automatic variables allocated on the stack, because
 *      we must catch the value of sp before any automatics are
 *      allocated.
 */

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

asm("#define _start start");
asm("#define _eprol eprol");

#ifdef hp300
asm("#define link .long 0; linkw");     /* Yuk!! */
#endif

extern  unsigned char   etext;
extern  unsigned char   eprol;
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 int d7;                /* needed for init (this will be
                                           a problem with GCC) */
        register struct kframe *kfp;    /* PCC a5 */
        register char **targv;
        register char **argv;
        extern int errno;

#ifdef lint
        kfp = 0;
        initcode = initcode = 0;
#else not lint
#ifdef __GNUC__
        asm("lea a6@(4),%0" : "=r" (kfp));      /* catch it quick */
#else
        asm("   lea     a6@(4),a5");    /* catch it quick */
#endif
#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));
}
asm("#undef link");
asm("#undef _start");
asm("#undef _eprol");

#ifdef MCRT0
/*ARGSUSED*/
exit(code)
        register int code;      /* PCC d7 */
{
        monitor(0);
        _cleanup();
#ifdef __GNUC__
        asm("movl %1,sp@-" : "=m" (*(char *)0) : "r" (code));
#else
        asm("   movl d7,sp@-");
#endif
        asm("   subql #4,sp");
        asm("   movl #1,d0");
        asm("   trap #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:    rts");
#endif CRT0