[thirdparty/glibc.git] / sysdeps / s390 / s390-64 / start.S

/* Startup code compliant to the 64 bit S/390 ELF ABI.
   Copyright (C) 2001-2015 Free Software Foundation, Inc.
   Contributed by Martin Schwidefsky (schwidefsky@de.ibm.com).
   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.

   In addition to the permissions in the GNU Lesser General Public
   License, the Free Software Foundation gives you unlimited
   permission to link the compiled version of this file with other
   programs, and to distribute those programs without any restriction
   coming from the use of this file. (The GNU Lesser General Public
   License restrictions do apply in other respects; for example, they
   cover modification of the file, and distribution when not linked
   into another program.)

   Note that people who make modified versions of this file are not
   obligated to grant this special exception for their modified
   versions; it is their choice whether to do so. The GNU Lesser
   General Public License gives permission to release a modified
   version without this exception; this exception also makes it
   possible to release a modified version which carries forward this
   exception.

   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, see
   <http://www.gnu.org/licenses/>.  */

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

   %r14		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.

   %r15		The stack contains the arguments and environment:
		0(%r15)			argc
		8(%r15)			argv[0]
		...
		(8*argc)(%r15)		NULL
		(8*(argc+1))(%r15)	envp[0]
		...
					NULL
*/

	.text
	.globl _start
	.type _start,@function
_start:
	/* Load argc and argv from stack.  */
	la	%r4,8(%r15)		# get argv
	lg	%r3,0(%r15)		# get argc

	/* Align the stack to a double word boundary.  */
	lghi	%r0,-16
	ngr	%r15,%r0

	/* Setup a stack frame and a parameter area.  */
	aghi	%r15,-176		# make room on stack
	xc	0(8,%r15),0(%r15)	# clear back-chain

	/* Set up arguments for __libc_start_main:
	   main, argc, argv, envp, _init, _fini, rtld_fini, stack_end
	   Note that envp will be determined later in __libc_start_main.
	 */
	stmg	%r14,%r15,160(%r15)	# store rtld_fini/stack_end to parameter area
	la	%r7,160(%r15)
	larl	%r6,__libc_csu_fini	# load pointer to __libc_csu_fini
	larl	%r5,__libc_csu_init	# load pointer to __libc_csu_init

	/* Ok, now branch to the libc main routine.  */
#ifdef PIC
	larl	%r2,main@GOTENT		# load pointer to main
	lg	%r2,0(%r2)
	brasl	%r14,__libc_start_main@plt
#else
	larl	%r2,main		# load pointer to main
	brasl	%r14,__libc_start_main
#endif

	/* Crash if __libc_start_main returns.	*/
	.word	0

	/* 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
ffeac417	1	/* Startup code compliant to the 64 bit S/390 ELF ABI.
b168057a	2	Copyright (C) 2001-2015 Free Software Foundation, Inc.
847b055c AJ	3	Contributed by Martin Schwidefsky (schwidefsky@de.ibm.com).
	4	This file is part of the GNU C Library.
	5
	6	The GNU C Library is free software; you can redistribute it and/or
41bdb6e2 AJ	7	modify it under the terms of the GNU Lesser General Public
	8	License as published by the Free Software Foundation; either
	9	version 2.1 of the License, or (at your option) any later version.
847b055c	10
92c6ccd1 RM	11	In addition to the permissions in the GNU Lesser General Public
	12	License, the Free Software Foundation gives you unlimited
	13	permission to link the compiled version of this file with other
	14	programs, and to distribute those programs without any restriction
	15	coming from the use of this file. (The GNU Lesser General Public
	16	License restrictions do apply in other respects; for example, they
	17	cover modification of the file, and distribution when not linked
	18	into another program.)
	19
	20	Note that people who make modified versions of this file are not
	21	obligated to grant this special exception for their modified
	22	versions; it is their choice whether to do so. The GNU Lesser
	23	General Public License gives permission to release a modified
	24	version without this exception; this exception also makes it
	25	possible to release a modified version which carries forward this
	26	exception.
	27
847b055c AJ	28	The GNU C Library is distributed in the hope that it will be useful,
	29	but WITHOUT ANY WARRANTY; without even the implied warranty of
	30	MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
41bdb6e2	31	Lesser General Public License for more details.
847b055c	32
41bdb6e2	33	You should have received a copy of the GNU Lesser General Public
59ba27a6 PE	34	License along with the GNU C Library; if not, see
59ba27a6 PE	35	<http://www.gnu.org/licenses/>. */
847b055c	36
6a7a8b22	37	/*
847b055c AJ	38	This is the canonical entry point, usually the first thing in the text
	39	segment. Most registers' values are unspecified, except for:
	40
ffeac417	41	%r14 Contains a function pointer to be registered with `atexit'.
847b055c AJ	42	This is how the dynamic linker arranges to have DT_FINI
	43	functions called for shared libraries that have been loaded
	44	before this code runs.
	45
	46	%r15 The stack contains the arguments and environment:
	47	0(%r15) argc
ffeac417	48	8(%r15) argv[0]
847b055c	49	...
ffeac417 UD	50	(8*argc)(%r15) NULL
ffeac417 UD	51	(8*(argc+1))(%r15) envp[0]
847b055c AJ	52	...
	53	NULL
	54	*/
	55
	56	.text
	57	.globl _start
d1cf3e71	58	.type _start,@function
847b055c	59	_start:
ffeac417 UD	60	/* Load argc and argv from stack. */
	61	la %r4,8(%r15) # get argv
	62	lg %r3,0(%r15) # get argc
847b055c	63
ffeac417 UD	64	/* Align the stack to a double word boundary. */
	65	lghi %r0,-16
	66	ngr %r15,%r0
847b055c	67
ffeac417 UD	68	/* Setup a stack frame and a parameter area. */
	69	aghi %r15,-176 # make room on stack
	70	xc 0(8,%r15),0(%r15) # clear back-chain
847b055c	71
ffeac417	72	/* Set up arguments for __libc_start_main:
847b055c	73	main, argc, argv, envp, _init, _fini, rtld_fini, stack_end
ffeac417	74	Note that envp will be determined later in __libc_start_main.
847b055c	75	*/
ffeac417 UD	76	stmg %r14,%r15,160(%r15) # store rtld_fini/stack_end to parameter area
ffeac417 UD	77	la %r7,160(%r15)
06b31ad3 RM	78	larl %r6,__libc_csu_fini # load pointer to __libc_csu_fini
06b31ad3 RM	79	larl %r5,__libc_csu_init # load pointer to __libc_csu_init
847b055c	80
ffeac417	81	/* Ok, now branch to the libc main routine. */
57a5ea02	82	#ifdef PIC
308bb2d5 UD	83	larl %r2,main@GOTENT # load pointer to main
308bb2d5 UD	84	lg %r2,0(%r2)
57a5ea02 UD	85	brasl %r14,__libc_start_main@plt
57a5ea02 UD	86	#else
308bb2d5	87	larl %r2,main # load pointer to main
ffeac417	88	brasl %r14,__libc_start_main
57a5ea02	89	#endif
847b055c	90
ffeac417 UD	91	/* Crash if __libc_start_main returns. */
ffeac417 UD	92	.word 0
847b055c	93
ffeac417	94	/* Define a symbol for the first piece of initialized data. */
847b055c AJ	95	.data
	96	.globl __data_start
	97	__data_start:
	98	.long 0
	99	.weak data_start
	100	data_start = __data_start