[thirdparty/glibc.git] / sysdeps / arm / elf / start.S

/* Startup code for ARM & ELF
   Copyright (C) 1995, 1996, 1997, 1998 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., 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 for:

   r0		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(%esp)			argc
		4(%esp)			argv[0]
		...
		(4*argc)(%esp)		NULL
		(4*(argc+1))(%esp)	envp[0]
		...
					NULL
*/

	.text
	.globl _start
_start:
	/* Clear the frame pointer.  The Intel ABI suggests this be done,
		to mark the outermost frame obviously. This seems like a
		sensible thing to do  */
	mov fp, #0

	/* r0 contains the address of the shared library termination
	   function, which we will register with `atexit' to be called by
	   `exit'.  I suspect that on some systems, and when statically
	   linked, this will not be set by anything to any function
	   pointer; hopefully it will be zero so we don't try to call
	   random pointers.  */
	cmp r0,#0
	blne atexit(PLT)

	/* 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. For dyn-link
	   programs, this has been run already, in the .init code. */
#ifndef PIC
	bl __libc_init_first

	/* Extract the arguments and environment as encoded on the stack
	   and set up the arguments for `main': argc, argv, envp.  */
	ldr r0,[sp]
	add r1,sp,#4
	add r2,r1,r0,lsl #2
	add r2,r2,#4
	/* save a copy of envp while we have it */
	ldr r3,L_environ
	str r2,[r3]

	/* 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.  */
	bl _init
	ldr r0,L_fini
	bl atexit
	b L_pfini

L_fini:	.word _fini
L_environ: .word _environ
L_pfini:
#endif
	/* rebuild the arg list for main() */
	ldr r0,[sp]
	add r1,sp,#4
	add r2,r1,r0,lsl #2
	add r2,r2,#4

	/* Call the user's main function, and exit with its value.  */
	bl main
	bl exit
	/* 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
Commit	Line	Data
df27fae1 UD	1	/* Startup code for ARM & ELF
	2	Copyright (C) 1995, 1996, 1997, 1998 Free Software Foundation, Inc.
	3	This file is part of the GNU C Library.
	4
	5	The GNU C Library is free software; you can redistribute it and/or
	6	modify it under the terms of the GNU Library General Public License as
	7	published by the Free Software Foundation; either version 2 of the
	8	License, or (at your option) any later version.
	9
	10	The GNU C Library is distributed in the hope that it will be useful,
	11	but WITHOUT ANY WARRANTY; without even the implied warranty of
	12	MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
	13	Library General Public License for more details.
	14
	15	You should have received a copy of the GNU Library General Public
	16	License along with the GNU C Library; see the file COPYING.LIB. If not,
	17	write to the Free Software Foundation, Inc., 59 Temple Place - Suite 330,
	18	Boston, MA 02111-1307, USA. */
	19
	20	/* This is the canonical entry point, usually the first thing in the text
	21	segment.
	22
	23	Note that the code in the .init section has already been run.
	24	This includes _init and _libc_init
	25
	26
	27	At this entry point, most registers' values are unspecified, except for:
	28
	29	r0 Contains a function pointer to be registered with `atexit'.
	30	This is how the dynamic linker arranges to have DT_FINI
	31	functions called for shared libraries that have been loaded
	32	before this code runs.
	33
	34	sp The stack contains the arguments and environment:
	35	0(%esp) argc
	36	4(%esp) argv[0]
	37	...
	38	(4*argc)(%esp) NULL
	39	(4*(argc+1))(%esp) envp[0]
	40	...
	41	NULL
	42	*/
	43
	44	.text
	45	.globl _start
	46	_start:
	47	/* Clear the frame pointer. The Intel ABI suggests this be done,
	48	to mark the outermost frame obviously. This seems like a
	49	sensible thing to do */
	50	mov fp, #0
	51
	52	/* r0 contains the address of the shared library termination
	53	function, which we will register with `atexit' to be called by
	54	`exit'. I suspect that on some systems, and when statically
	55	linked, this will not be set by anything to any function
	56	pointer; hopefully it will be zero so we don't try to call
	57	random pointers. */
	58	cmp r0,#0
	59	blne atexit(PLT)
	60
	61	/* Do essential libc initialization. In statically linked
	62	programs under the GNU Hurd, this is what sets up the
	63	arguments on the stack for the code below. For dyn-link
	64	programs, this has been run already, in the .init code. */
65	#ifndef PIC
66	bl __libc_init_first
67
68	/* Extract the arguments and environment as encoded on the stack
69	and set up the arguments for `main': argc, argv, envp. */
70	ldr r0,[sp]
71	add r1,sp,#4
72	add r2,r1,r0,lsl #2
73	add r2,r2,#4
74	/* save a copy of envp while we have it */
75	ldr r3,L_environ
76	str r2,[r3]
77
78	/* Call `_init', which is the entry point to our own `.init'
79	section; and register with `atexit' to have `exit' call
80	`_fini', which is the entry point to our own `.fini' section. */
81	bl _init
82	ldr r0,L_fini
83	bl atexit
84	b L_pfini
85
86	L_fini: .word _fini
87	L_environ: .word _environ
88	L_pfini:
89	#endif
90	/* rebuild the arg list for main() */
91	ldr r0,[sp]
92	add r1,sp,#4
93	add r2,r1,r0,lsl #2
94	add r2,r2,#4
95
96	/* Call the user's main function, and exit with its value. */
97	bl main
98	bl exit
99	/* should never get here....*/
100	bl abort
101
102
103	/* Define a symbol for the first piece of initialized data. */
104	.data
105	.globl __data_start
106	__data_start:
107	.long 0
108	.weak data_start
109	data_start = __data_start