ports/sysdeps/am33/elf/start.S

   1 /* Startup code compliant to the ELF MN10300 ABI.
   2    Copyright (C) 1995-2013 Free Software Foundation, Inc.
   3    Contributed by Alexandre Oliva  <aoliva@redhat.com>
   4    Based on ../../i386/elf/start.S.
   5    This file is part of the GNU C Library.
   6
   7    The GNU C Library is free software; you can redistribute it and/or
   8    modify it under the terms of the GNU Lesser General Public
   9    License as published by the Free Software Foundation; either
  10    version 2.1 of the License, or (at your option) any later version.
  11
  12    The GNU C Library 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 GNU
  15    Lesser General Public License for more details.
  16
  17    You should have received a copy of the GNU Lesser General Public
  18    License along with the GNU C Library.  If not, see
  19    <http://www.gnu.org/licenses/>.  */
  20
  21 /* This is the canonical entry point, usually the first thing in the text
  22    segment.  The SVR4/i386 ABI (pages 3-31, 3-32) says that when the entry
  23    point runs, most registers' values are unspecified, except for:
  24
  25    a0           Contains a function pointer to be registered with `atexit'.
  26                 This is how the dynamic linker arranges to have DT_FINI
  27                 functions called for shared libraries that have been loaded
  28                 before this code runs.
  29
  30    sp           The stack contains the arguments and environment:
  31                 (4,sp)                  argc
  32                 (8,sp)                  argv[0]
  33                 ...
  34                 (4*(argc+1),sp)         NULL
  35                 (4*(argc+2),sp)         envp[0]
  36                 ...
  37                                         NULL
  38 */
  39
  40         .text
  41         .globl _start
  42         .type _start,@function
  43 _start:
  44         /* Extract the arguments as encoded on the stack and set up
  45            the arguments for `main': argc, argv.  envp will be determined
  46            later in __libc_start_main.  */
  47         mov sp,a3
  48         add -32,sp
  49
  50         mov a3,(28,sp)          /* stack_end.  */
  51         mov d0,(24,sp)          /* rtld_fini.  */
  52         mov _fini, d3
  53         mov d3,(20,sp)          /* fini.  */
  54         mov _init, d2
  55         mov d2,(16,sp)          /* init.  */
  56         inc4 a3
  57         mov a3,(12,sp)          /* argv.  */
  58
  59         /* Set the initial frame pointer as 0, so that the bottom of
  60            the stack is clearly marked.  */
  61         mov 0,a3
  62
  63         mov (32,sp), d1         /* argc.  */
  64         mov main, d0            /* main.  */
  65
  66         /* Call the user's main function, and exit with its value.
  67            But let the libc call main.    */
  68         call __libc_start_main,[],0
  69
  70         call abort,[],0 /* Crash if somehow `exit' does return.  */
  71
  72 /* Define a symbol for the first piece of initialized data.  */
  73         .data
  74         .globl __data_start
  75 __data_start:
  76         .long 0
  77         .weak data_start
  78         data_start = __data_start