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