src/ecrt0.c

   1 /* C code startup routine.
   2    Copyright (C) 1985, 1986, 1992, 2001, 2002, 2003, 2004,
   3                  2005, 2006, 2007, 2008 Free Software Foundation, Inc.
   4
   5 This file is part of GNU Emacs.
   6
   7 GNU Emacs is free software: you can redistribute it and/or modify
   8 it under the terms of the GNU General Public License as published by
   9 the Free Software Foundation, either version 3 of the License, or
  10 (at your option) any later version.
  11
  12 GNU Emacs is distributed in the hope that it will be useful,
  13 but WITHOUT ANY WARRANTY; without even the implied warranty of
  14 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  15 GNU General Public License for more details.
  16
  17 You should have received a copy of the GNU General Public License
  18 along with GNU Emacs.  If not, see <http://www.gnu.org/licenses/>.  */
  19
  20
  21 /* The standard Vax 4.2 Unix crt0.c cannot be used for Emacs
  22    because it makes `environ' an initialized variable.
  23    It is easiest to have a special crt0.c on all machines
  24    though I don't know whether other machines actually need it.  */
  25
  26 /* On the vax and 68000, in BSD4.2 and USG5.2,
  27    this is the data format on startup:
  28   (vax) ap and fp are unpredictable as far as I know; don't use them.
  29   sp ->  word containing argc
  30          word pointing to first arg string
  31          [word pointing to next arg string]... 0 or more times
  32          0
  33 Optionally:
  34          [word pointing to environment variable]... 1 or more times
  35          ...
  36          0
  37 And always:
  38          first arg string
  39          [next arg string]... 0 or more times
  40 */
  41
  42 #ifdef emacs
  43 #include <config.h>
  44 #endif
  45
  46 /*              ********  WARNING ********
  47     Do not insert any data definitions before data_start!
  48     Since this is the first file linked, the address of the following
  49     variable should correspond to the start of initialized data space.
  50     On some systems this is a constant that is independent of the text
  51     size for shared executables.  On others, it is a function of the
  52     text size. In short, this seems to be the most portable way to
  53     discover the start of initialized data space dynamically at runtime,
  54     for either shared or unshared executables, on either swapping or
  55     virtual systems.  It only requires that the linker allocate objects
  56     in the order encountered, a reasonable model for most Unix systems.
  57     Similarly, note that the address of _start() should be the start
  58     of text space.   Fred Fish, UniSoft Systems Inc.  */
  59
  60 int data_start = 0;
  61
  62 #ifdef NEED_ERRNO
  63 int errno;
  64 #endif
  65
  66 #ifndef MSDOS
  67 char **environ;
  68 #endif
  69
  70 #ifndef static
  71 /* On systems where the static storage class is usable, this function
  72    should be declared as static.  Otherwise, the static keyword has
  73    been defined to be something else, and code for those systems must
  74    take care of this declaration appropriately.  */
  75 static start1 ();
  76 #endif
  77
  78 #ifdef CRT0_DUMMIES
  79
  80 /* Define symbol "start": here; some systems want that symbol.  */
  81 #ifdef DOT_GLOBAL_START
  82 asm("   .text           ");
  83 asm("   .globl start    ");
  84 asm("   start:          ");
  85 #endif /* DOT_GLOBAL_START */
  86
  87 #ifdef NODOT_GLOBAL_START
  88 asm("   text            ");
  89 asm("   global start    ");
  90 asm("   start:          ");
  91 #endif /* NODOT_GLOBAL_START */
  92
  93 _start ()
  94 {
  95 /* On vax, nothing is pushed here  */
  96   start1 ();
  97 }
  98
  99 static
 100 start1 (CRT0_DUMMIES argc, xargv)
 101      int argc;
 102      char *xargv;
 103 {
 104   register char **argv = &xargv;
 105   environ = argv + argc + 1;
 106
 107   if ((char *)environ == xargv)
 108     environ--;
 109   exit (main (argc, argv, environ));
 110
 111   /* Refer to `start1' so GCC will not think it is never called
 112      and optimize it out.  */
 113   (void) &start1;
 114 }
 115 #else /* not CRT0_DUMMIES */
 116
 117 /* This is a kludge.  Now that the CRT0_DUMMIES mechanism above exists,
 118    most of these machines could use the vax code above
 119    with some suitable definition of CRT0_DUMMIES.
 120    Then the symbol m68k could be flushed.
 121    But I don't want to risk breaking these machines
 122    in a version 17 patch release, so that change is being put off.  */
 123
 124 #ifdef m68k                     /* Can't do it all from C */
 125         asm ("  global  _start");
 126         asm ("  text");
 127         asm ("_start:");
 128         asm ("  comm    splimit%,4");
 129         asm ("  global  exit");
 130         asm ("  text");
 131         asm ("  mov.l   %d0,splimit%");
 132         asm ("  jsr     start1");
 133         asm ("  mov.l   %d0,(%sp)");
 134         asm ("  jsr     exit");
 135         asm ("  mov.l   &1,%d0");       /* d0 = 1 => exit */
 136         asm ("  trap    &0");
 137
 138 /* ignore takes care of skipping the a6 value pushed in start.  */
 139 static
 140 start1 (argc, xargv)
 141      int argc;
 142      char *xargv;
 143 {
 144   register char **argv = &xargv;
 145   environ = argv + argc + 1;
 146
 147   if ((char *)environ == xargv)
 148     environ--;
 149   exit (main (argc, argv, environ));
 150 }
 151
 152 #endif /* m68k */
 153
 154 #endif /* not CRT0_DUMMIES */
 155
 156 #ifdef __sparc__
 157 asm (".global __start");
 158 asm (".text");
 159 asm ("__start:");
 160 asm ("  mov     0, %fp");
 161 asm ("  ld      [%sp + 64], %o0");
 162 asm ("  add     %sp, 68, %o1");
 163 asm ("  sll     %o0, 2, %o2");
 164 asm ("  add     %o2, 4, %o2");
 165 asm ("  add     %o1, %o2, %o2");
 166 asm ("  sethi   %hi(_environ), %o3");
 167 asm ("  st      %o2, [%o3+%lo(_environ)]");
 168 asm ("  andn    %sp, 7, %sp");
 169 asm ("  call    _main");
 170 asm ("  sub     %sp, 24, %sp");
 171 asm ("  call    __exit");
 172 asm ("  nop");
 173
 174 #endif /* __sparc__ */
 175
 176 #if __FreeBSD__ == 2
 177 char *__progname;
 178 #endif
 179
 180 /* arch-tag: 4025c2fb-d6b1-4d29-b1b6-8100b6bd1e74
 181    (do not change this comment) */