glibc/sysdeps/cris/elf/start.S

/* Startup code compliant to the ELF CRIS ABI (to-be-written).
   Copyright (C) 2001 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.  */

#include <sysdep.h>

/* This is the canonical entry point, usually the first thing in the text
   segment.  When the entry point runs, most registers' values are
   unspecified, except for:

   R10		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:
		[SP]			argc
		[SP+4]			argv[0]
		...
		[SP+4*argc]		NULL
		[SP+4*(argc+1)]		envp[0]
		...
					NULL
*/

	.syntax no_register_prefix

	.text
	.globl	_start
	.type _start,@function
_start:
	/* Clear the frame pointer, to mark the outermost frame.  */
	moveq	0,r8

	/* Move the shared library termination function to the right place
	   for __libc_main.  */
	move.d	r10,r9

	/* Extract the arguments as encoded on the stack and set up the
	   arguments for `main': argc, argv.  envp will be determined
	   later in __libc_start_main.  */

	/* Get the argument count.  */
	move.d	[sp],r11

	/* Store the stack pointer as end of stack.  We overwrite
	   the incoming argc.  */
	move.d	sp,[sp]

	/* The argument vector starts just after the argument count.  */
	move.d	sp,r12
	addq	4,r12

	/* There are seven arguments to __libc_start_main:
	   r10:  main - Address of it.
	   r11:  argc
	   r12:  argv
	   r13:  init - Function to call.

	   [sp]: fini - Function to register with atexit.
           [sp+4]: rtld_fini - Another function to register with atexit.
	   [sp+8]: stack_end - Top of stack (actually same as argv).

	   The last two are passed on stack.  */

        /* Store the fini function coming from the dynamic loader.  */
	push	r9

	/* Get the addresses of our own entry points to `.fini' and
	   `.init'.  */

#ifdef __PIC__
        /* If for some reason this program is compiled as PIC, set up R0.  */
	move.d	pc,r0
	sub.d	.:GOTOFF,r0

	move.d	_init:PLTG,r13
	add.d	r0,r13
	move.d	_fini:PLTG,r9
	add.d	r0,r9
	move.d	main:PLTG,r10
	add.d	r0,r10
#else
	move.d	_init,r13
	move.d	_fini,r9
	move.d	main,r10
#endif
	push	r9

	/* Call the user's main function, and exit with its value.  But
	   let the libc call main.  */
	PLTCALL	(__libc_start_main)

	/* Crash if somehow `exit' does return.  We have at least 8192
	   invalid addresses to choose from.  */
	test.d	[6502]

	/* Stop the unstoppable.  */
0:
	ba	0b
	nop

/* 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