[thirdparty/glibc.git] / sysdeps / x86_64 / elf / start.S

/* Startup code compliant to the ELF x86-64 ABI.
   Copyright (C) 2001, 2002, 2003 Free Software Foundation, Inc.
   This file is part of the GNU C Library.
   Contributed by Andreas Jaeger <aj@suse.de>, 2001.

   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, 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.  The SVR4/i386 ABI (pages 3-31, 3-32) says that when the entry
   point runs, most registers' values are unspecified, except for:

   %rdx		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.

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

#include "bp-sym.h"

	.text
	.globl _start
	.type _start,@function
_start:
	/* Clear the frame pointer.  The ABI suggests this be done, to mark
	   the outermost frame obviously.  */
	xorq %rbp, %rbp

	/* Extract the arguments as encoded on the stack and set up
	   the arguments for __libc_start_main (int (*main) (int, char **, char **),
		   int argc, char *argv,
		   void (*init) (void), void (*fini) (void),
		   void (*rtld_fini) (void), void *stack_end).
	   The arguments are passed via registers and on the stack:
	main:		%rdi
	argc:		%rsi
	argv:		%rdx
	init:		%rcx
	fini:		%r8
	rtld_fini:	%r9
	stack_end:	stack.	*/

	movq %rdx, %r9		/* Address of the shared library termination
				   function.  */
	popq %rsi		/* Pop the argument count.  */
	movq %rsp, %rdx		/* argv starts just at the current stack top.  */
	/* Align the stack to a 16 byte boundary to follow the ABI.  */
	andq  $~15, %rsp

	pushq %rax		/* Push garbage because we push 8 more bytes.  */

	/* Provide the highest stack address to the user code (for stacks
	   which grow downwards).  */
	pushq %rsp

#ifdef SHARED
	/* Pass address of our own entry points to .fini and .init.  */
	movq __libc_csu_fini@GOTPCREL(%rip), %r8
	movq __libc_csu_init@GOTPCREL(%rip), %rcx

	movq BP_SYM (main)@GOTPCREL(%rip), %rdi

	/* Call the user's main function, and exit with its value.
	   But let the libc call main.	  */
	call BP_SYM (__libc_start_main)@PLT
#else
	/* Pass address of our own entry points to .fini and .init.  */
	movq $__libc_csu_fini, %r8
	movq $__libc_csu_init, %rcx

	movq $BP_SYM (main), %rdi

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

	hlt			/* Crash if somehow `exit' 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
Commit	Line	Data
c9cf6dde	1	/* Startup code compliant to the ELF x86-64 ABI.
a334319f	2	Copyright (C) 2001, 2002, 2003 Free Software Foundation, Inc.
c9cf6dde AJ	3	This file is part of the GNU C Library.
	4	Contributed by Andreas Jaeger <aj@suse.de>, 2001.
	5
	6	The GNU C Library is free software; you can redistribute it and/or
	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.
	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
c9cf6dde 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
	31	Lesser General Public License for more details.
	32
	33	You should have received a copy of the GNU Lesser General Public
	34	License along with the GNU C Library; if not, write to the Free
	35	Software Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA
	36	02111-1307 USA. */
	37
	38	/* This is the canonical entry point, usually the first thing in the text
	39	segment. The SVR4/i386 ABI (pages 3-31, 3-32) says that when the entry
	40	point runs, most registers' values are unspecified, except for:
	41
	42	%rdx Contains a function pointer to be registered with `atexit'.
	43	This is how the dynamic linker arranges to have DT_FINI
	44	functions called for shared libraries that have been loaded
	45	before this code runs.
	46
	47	%rsp The stack contains the arguments and environment:
	48	0(%rsp) argc
	49	8(%rsp) argv[0]
	50	...
	51	(8*argc)(%rsp) NULL
	52	(8*(argc+1))(%rsp) envp[0]
	53	...
	54	NULL
	55	*/
	56
	57	#include "bp-sym.h"
	58
	59	.text
	60	.globl _start
	61	.type _start,@function
	62	_start:
	63	/* Clear the frame pointer. The ABI suggests this be done, to mark
	64	the outermost frame obviously. */
a334319f	65	xorq %rbp, %rbp
c9cf6dde AJ	66
	67	/* Extract the arguments as encoded on the stack and set up
	68	the arguments for __libc_start_main (int (main) (int, char , char *),
	69	int argc, char *argv,
	70	void (init) (void), void (fini) (void),
	71	void (rtld_fini) (void), void stack_end).
	72	The arguments are passed via registers and on the stack:
	73	main: %rdi
	74	argc: %rsi
	75	argv: %rdx
	76	init: %rcx
	77	fini: %r8
	78	rtld_fini: %r9
	79	stack_end: stack. */
	80
	81	movq %rdx, %r9 /* Address of the shared library termination
	82	function. */
	83	popq %rsi /* Pop the argument count. */
	84	movq %rsp, %rdx /* argv starts just at the current stack top. */
	85	/* Align the stack to a 16 byte boundary to follow the ABI. */
	86	andq $~15, %rsp
	87
	88	pushq %rax /* Push garbage because we push 8 more bytes. */
	89
	90	/* Provide the highest stack address to the user code (for stacks
	91	which grow downwards). */
	92	pushq %rsp
	93
d49c05e0 UD	94	#ifdef SHARED
	95	/* Pass address of our own entry points to .fini and .init. */
	96	movq __libc_csu_fini@GOTPCREL(%rip), %r8
	97	movq __libc_csu_init@GOTPCREL(%rip), %rcx
	98
	99	movq BP_SYM (main)@GOTPCREL(%rip), %rdi
	100
	101	/* Call the user's main function, and exit with its value.
	102	But let the libc call main. */
	103	call BP_SYM (__libc_start_main)@PLT
	104	#else
c9cf6dde	105	/* Pass address of our own entry points to .fini and .init. */
06b31ad3 RM	106	movq $__libc_csu_fini, %r8
06b31ad3 RM	107	movq $__libc_csu_init, %rcx
c9cf6dde AJ	108
	109	movq $BP_SYM (main), %rdi
	110
	111	/* Call the user's main function, and exit with its value.
	112	But let the libc call main. */
	113	call BP_SYM (__libc_start_main)
d49c05e0	114	#endif
c9cf6dde AJ	115
	116	hlt /* Crash if somehow `exit' does return. */
	117
	118	/* Define a symbol for the first piece of initialized data. */
	119	.data
	120	.globl __data_start
	121	__data_start:
	122	.long 0
	123	.weak data_start
	124	data_start = __data_start