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/* Startup code compliant to the ELF m68k ABI.
Copyright (C) 1996 Free Software Foundation, Inc.
This file is part of the GNU C Library.
The GNU C Library is free software; you can redistribute it and/or
modify it under the terms of the GNU Library General Public License as
published by the Free Software Foundation; either version 2 of the
License, or (at your option) any later version.
The GNU C Library is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
Library General Public License for more details.
You should have received a copy of the GNU Library General Public
License along with the GNU C Library; see the file COPYING.LIB. If
not, write to the Free Software Foundation, Inc., 675 Mass Ave,
Cambridge, MA 02139, USA. */
/* This is the canonical entry point, usually the first thing in the text
segment. The SVR4/m68k ABI says that when the entry point runs,
most registers' values are unspecified, except for:
%a1 Contains a function pointer to be registered with `atexit'.
This is how the dynamic linker arranges to have DT_FINI
functions called for shared libraries that have been loaded
before this code runs.
%sp The stack contains the arguments and environment:
0(%sp) argc
4(%sp) argv[0]
...
(4*argc)(%sp) NULL
(4*(argc+1))(%sp) envp[0]
...
NULL
*/
.text
.globl _start
_start:
/* Clear the frame pointer. The ABI suggests this be done, to mark
the outermost frame obviously. */
sub.l %fp, %fp
/* %a1 contains the address of the shared library termination
function, which we will register with `atexit' to be called by
`exit'. */
tstl %a1
jbeq 1f
move.l %a1, -(%sp)
jbsr atexit
addql #4, %sp
1:
/* Do essential libc initialization. In statically linked
programs under the GNU Hurd, this is what sets up the
arguments on the stack for the code below. */
jbsr __libc_init_first
/* Extract the arguments and environment as encoded on the stack
and set up the arguments for `main': argc, argv, envp. */
move.l (%sp)+, %d0 /* Pop the argument count. */
lea (4,%sp,%d0*4), %a0 /* envp = &argv[argc + 1] */
move.l %a0, _environ /* Store it in the global variable. */
pea (%a0) /* Push third argument: envp. */
pea 4(%sp) /* Push second argument: argv. */
move.l %d0, -(%sp) /* Push first argument: argc. */
/* Call `_init', which is the entry point to our own `.init'
section; and register with `atexit' to have `exit' call
`_fini', which is the entry point to our own `.fini' section. */
jbsr _init
move.l #_fini, -(%sp)
jbsr atexit
addq.l #4, %sp
/* Call the user's main function, and exit with its value. */
jbsr main
move.l %d0, (%sp)
1: jbsr exit /* This should never return. */
jbra 1b /* Try again if somehow it does return. */
/* Define a symbol for the first piece of initialized data. */
.data
.globl __data_start
__data_start:
.long 0
.weak data_start
data_start = __data_start
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