newlib/libc/sys/sysvi386/crt0.c

   1 /*-
   2  * Copyright (c) 1990 The Regents of the University of California.
   3  * All rights reserved.
   4  *
   5  * Redistribution and use in source and binary forms, with or without
   6  * modification, are permitted provided that the following conditions
   7  * are met:
   8  * 1. Redistributions of source code must retain the above copyright
   9  *    notice, this list of conditions and the following disclaimer.
  10  * 2. Redistributions in binary form must reproduce the above copyright
  11  *    notice, this list of conditions and the following disclaimer in the
  12  *    documentation and/or other materials provided with the distribution.
  13  * 3. Neither the name of the University nor the names of its contributors
  14  *    may be used to endorse or promote products derived from this software
  15  *    without specific prior written permission.
  16  *
  17  * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
  18  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
  19  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
  20  * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
  21  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
  22  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
  23  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
  24  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
  25  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
  26  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
  27  * SUCH DAMAGE.
  28  */
  29
  30 #if defined(LIBC_SCCS) && !defined(lint)
  31 static char sccsid[] = "@(#)crt0.c      5.7 (Berkeley) 7/3/91";
  32 #endif /* LIBC_SCCS and not lint */
  33
  34 /*
  35  *      C start up routine.
  36  *      Robert Henry, UCB, 20 Oct 81
  37  *
  38  *      We make the following (true) assumption:
  39  *      1) The only register variable that we can trust is ebp,
  40  *      which points to the base of the kernel calling frame.
  41  */
  42
  43 char **environ = (char **)0;
  44 static int fd;
  45
  46 /*
  47 asm(".text");
  48 asm(".long 0xc000c000");
  49 */
  50 extern  unsigned char   etext;
  51 extern  unsigned char   eprol asm ("eprol");
  52 /* extern                       start() asm("start"); */
  53
  54 _start(int arg)
  55 {
  56         struct kframe {
  57                 int     kargc;
  58                 char    *kargv[1];      /* size depends on kargc */
  59                 char    kargstr[1];     /* size varies */
  60                 char    kenvstr[1];     /* size varies */
  61         };
  62         /*
  63          *      ALL REGISTER VARIABLES!!!
  64          */
  65         register struct kframe *kfp;    /* r10 */
  66         register char **targv;
  67         register char **argv;
  68         extern int errno;
  69         extern void _mcleanup();
  70
  71 #ifdef lint
  72         kfp = 0;
  73         initcode = initcode = 0;
  74 #else not lint
  75 # if 0
  76         asm("lea 4(%ebp),%ebx");        /* catch it quick */
  77 # else
  78         kfp = (struct kframe *)&(((int *)(&arg))[-1]);
  79 # endif
  80 #endif not lint
  81         for (argv = targv = &kfp->kargv[0]; *targv++; /* void */)
  82                 /* void */ ;
  83         if (targv >= (char **)(*argv))
  84                 --targv;
  85         environ = targv;
  86 asm("eprol:");
  87
  88 #ifdef paranoid
  89         /*
  90          * The standard I/O library assumes that file descriptors 0, 1, and 2
  91          * are open. If one of these descriptors is closed prior to the start
  92          * of the process, I/O gets very confused. To avoid this problem, we
  93          * insure that the first three file descriptors are open before calling
  94          * main(). Normally this is undefined, as it adds two unnecessary
  95          * system calls.
  96          */
  97         do      {
  98                 fd = open("/dev/null", 2);
  99         } while (fd >= 0 && fd < 3);
 100         close(fd);
 101 #endif paranoid
 102
 103 #ifdef MCRT0
 104         atexit(_mcleanup);
 105         monstartup(&eprol, &etext);
 106 #endif MCRT0
 107         errno = 0;
 108         exit(main(kfp->kargc, argv, environ));
 109 }
 110
 111 #ifdef CRT0
 112 /*
 113  * null mcount and moncontrol,
 114  * just in case some routine is compiled for profiling
 115  */
 116 moncontrol(val)
 117         int val;
 118 {
 119
 120 }
 121 asm(".globl mcount");
 122 asm("mcount: ret");
 123 #endif CRT0