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Annotation of 43BSDTahoe/lib/libc/vax/csu/crt0.c, revision 1.1.1.1

1.1       root        1: /*
                      2:  * Copyright (c) 1980 Regents of the University of California.
                      3:  * All rights reserved.  The Berkeley software License Agreement
                      4:  * specifies the terms and conditions for redistribution.
                      5:  */
                      6: 
                      7: #if defined(LIBC_SCCS) && !defined(lint)
                      8: static char sccsid[] = "@(#)crt0.c     5.4 (Berkeley) 1/18/88";
                      9: #endif LIBC_SCCS and not lint
                     10: 
                     11: /*
                     12:  *     C start up routine.
                     13:  *     Robert Henry, UCB, 20 Oct 81
                     14:  *
                     15:  *     We make the following (true) assumptions:
                     16:  *     1) when the kernel calls start, it does a jump to location 2,
                     17:  *     and thus avoids the register save mask.  We are NOT called
                     18:  *     with a calls!  see sys1.c:setregs().
                     19:  *     2) The only register variable that we can trust is sp,
                     20:  *     which points to the base of the kernel calling frame.
                     21:  *     Do NOT believe the documentation in exec(2) regarding the
                     22:  *     values of fp and ap.
                     23:  *     3) We can allocate as many register variables as we want,
                     24:  *     and don't have to save them for anybody.
                     25:  *     4) Because of the ways that asm's work, we can't have
                     26:  *     any automatic variables allocated on the stack, because
                     27:  *     we must catch the value of sp before any automatics are
                     28:  *     allocated.
                     29:  */
                     30: 
                     31: char **environ = (char **)0;
                     32: static int fd;
                     33: 
                     34: asm("#define _start start");
                     35: asm("#define _eprol eprol");
                     36: extern unsigned char   etext;
                     37: extern unsigned char   eprol;
                     38: start()
                     39: {
                     40:        struct kframe {
                     41:                int     kargc;
                     42:                char    *kargv[1];      /* size depends on kargc */
                     43:                char    kargstr[1];     /* size varies */
                     44:                char    kenvstr[1];     /* size varies */
                     45:        };
                     46:        /*
                     47:         *      ALL REGISTER VARIABLES!!!
                     48:         */
                     49:        register int r11;               /* needed for init */
                     50:        register struct kframe *kfp;    /* r10 */
                     51:        register char **targv;
                     52:        register char **argv;
                     53:        extern int errno;
                     54: 
                     55: #ifdef lint
                     56:        kfp = 0;
                     57:        initcode = initcode = 0;
                     58: #else not lint
                     59:        asm("   movl    sp,r10");       /* catch it quick */
                     60: #endif not lint
                     61:        for (argv = targv = &kfp->kargv[0]; *targv++; /* void */)
                     62:                /* void */ ;
                     63:        if (targv >= (char **)(*argv))
                     64:                --targv;
                     65:        environ = targv;
                     66: asm("eprol:");
                     67: 
                     68: #ifdef paranoid
                     69:        /*
                     70:         * The standard I/O library assumes that file descriptors 0, 1, and 2
                     71:         * are open. If one of these descriptors is closed prior to the start 
                     72:         * of the process, I/O gets very confused. To avoid this problem, we
                     73:         * insure that the first three file descriptors are open before calling
                     74:         * main(). Normally this is undefined, as it adds two unnecessary
                     75:         * system calls.
                     76:         */
                     77:        do      {
                     78:                fd = open("/dev/null", 2);
                     79:        } while (fd >= 0 && fd < 3);
                     80:        close(fd);
                     81: #endif paranoid
                     82: 
                     83: #ifdef MCRT0
                     84:        monstartup(&eprol, &etext);
                     85: #endif MCRT0
                     86:        errno = 0;
                     87:        exit(main(kfp->kargc, argv, environ));
                     88: }
                     89: asm("#undef _start");
                     90: asm("#undef _eprol");
                     91: 
                     92: #ifdef MCRT0
                     93: /*ARGSUSED*/
                     94: exit(code)
                     95:        register int code;      /* r11 */
                     96: {
                     97:        monitor(0);
                     98:        _cleanup();
                     99:        _exit(code);
                    100: }
                    101: #endif MCRT0
                    102: 
                    103: #ifdef CRT0
                    104: /*
                    105:  * null mcount and moncontrol,
                    106:  * just in case some routine is compiled for profiling
                    107:  */
                    108: moncontrol(val)
                    109:        int val;
                    110: {
                    111: 
                    112: }
                    113: asm("  .globl  mcount");
                    114: asm("mcount:   rsb");
                    115: #endif CRT0

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