glibc/sysdeps/arm/elf/start.S

/* Startup code for ARM & ELF
   Copyright (C) 1995, 1996, 1997, 1998, 2001, 2002 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 Lesser General Public
   License as published by the Free Software Foundation; either
   version 2.1 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
   Lesser General Public License for more details.

   You should have received a copy of the GNU Lesser General Public
   License along with the GNU C Library; if not, write to the Free
   Software Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA
   02111-1307 USA.  */

/* This is the canonical entry point, usually the first thing in the text
   segment.

	Note that the code in the .init section has already been run.
	This includes _init and _libc_init


	At this entry point, most registers' values are unspecified, except:

   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
	.type _start,#function
_start:
	/* Fetch address of fini */
	ldr ip, =__libc_csu_fini

	/* Clear the frame pointer since this is the outermost frame.  */
	mov fp, #0

	/* Pop argc off the stack and save a pointer to argv */
	ldr a2, [sp], #4
	mov a3, sp

	/* Push stack limit */
	str a3, [sp, #-4]!

	/* Push rtld_fini */
	str a1, [sp, #-4]!

	/* Set up the other arguments in registers */
	ldr a1, =main
	ldr a4, =__libc_csu_init

	/* Push fini */
	str ip, [sp, #-4]!

	/* __libc_start_main (main, argc, argv, init, fini, rtld_fini, stack_end) */

	/* Let the libc call main and exit with its return code.  */
	bl __libc_start_main

	/* should never get here....*/
	bl abort

/* 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