glibc/sysdeps/mips/elf/start.S

/* Startup code compliant to the ELF Mips ABI.
   Copyright (C) 1995, 1997, 2000, 2001, 2002, 2003
	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.  */

#define __ASSEMBLY__ 1
#include <entry.h>
#include <sys/asm.h>

#ifndef ENTRY_POINT
#error ENTRY_POINT needs to be defined for start.S on MIPS/ELF.
#endif

/* This is the canonical entry point, usually the first thing in the text
   segment.  The SVR4/Mips ABI (pages 3-31, 3-32) says that when the entry
   point runs, most registers' values are unspecified, except for:

   v0 ($2)	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 ($29)	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
   ra ($31)	The return address register is set to zero so that programs
		that search backword through stack frames recognize the last
		stack frame.
*/


/* We need to call:
   __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)
*/
	
	.text
	.globl ENTRY_POINT
	.type ENTRY_POINT,@function
ENTRY_POINT:
#ifdef __PIC__
	SETUP_GPX($0)
	SETUP_GPX64($25,$0)
#else
	PTR_LA $28, _gp		/* Setup GP correctly if we're non-PIC.  */
	move $31, $0
#endif

	PTR_LA $4, main		/* main */
	PTR_L $5, 0($29)		/* argc */
	PTR_ADDIU $6, $29, PTRSIZE	/* argv  */
	
	/* Allocate space on the stack for seven arguments (o32 only)
	   and make sure the stack is aligned to double words (8 bytes) 
	   on o32 and quad words (16 bytes) on n32 and n64.  */
	
	and $29, -2 * SZREG
#if _MIPS_SIM == _MIPS_SIM_ABI32
	PTR_SUBIU $29, 32
#endif
	PTR_LA $7, __libc_csu_init		/* init */
	PTR_LA $8, __libc_csu_fini
#if _MIPS_SIM == _MIPS_SIM_ABI32
	PTR_S $8, 16($29)		/* fini */
	PTR_S $2, 20($29)		/* rtld_fini */
	PTR_S $29, 24($29)		/* stack_end */
#else
	move $9, $2		/* rtld_fini */
	move $10, $29		/* stack_end */
#endif
	jal __libc_start_main
hlt:	b hlt			/* Crash if somehow it 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