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/* Startup code for ARM & ELF
Copyright (C) 1995, 1996, 1997, 1998, 2001, 2002, 2005
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.
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.
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:
a1 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(sp) argc
4(sp) argv[0]
...
(4*argc)(sp) NULL
(4*(argc+1))(sp) envp[0]
...
NULL
*/
/*
For uClinux it looks like this:
argc argument counter (integer)
argv char *argv[]
envp char *envp[]
argv[0] program name (pointer)
argv[1...N] program args (pointers)
argv[argc-1] end of args (integer)
NULL
env[0...N] environment variables (pointers)
NULL
ARM register quick reference:
Name Number ARM Procedure Calling Standard Role
a1 r0 argument 1 / integer result / scratch register / argc
a2 r1 argument 2 / scratch register / argv
a3 r2 argument 3 / scratch register / envp
a4 r3 argument 4 / scratch register
v1 r4 register variable
v2 r5 register variable
v3 r6 register variable
v4 r7 register variable
v5 r8 register variable
sb/v6 r9 static base / register variable
sl/v7 r10 stack limit / stack chunk handle / reg. variable
fp r11 frame pointer
ip r12 scratch register / new-sb in inter-link-unit calls
sp r13 lower end of current stack frame
lr r14 link address / scratch register
pc r15 program counter
*/
#include <features.h>
#include <bits/arm_asm.h>
.text
.globl _start
.type _start,%function
.type _init,%function
.type _fini,%function
#ifndef __UCLIBC_CTOR_DTOR__
.weak _init
.weak _fini
#endif
#if defined(THUMB1_ONLY)
.thumb_func
_start:
/* Clear the frame pointer since this is the outermost frame. */
mov r3, #0
mov fp, r3
#ifdef __ARCH_USE_MMU__
/* Pop argc off the stack and save a pointer to argv */
pop {a2}
mov a3, sp
#else
/*
* uClinux/arm stacks look a little different from normal
* MMU-full Linux/arm stacks (for no good reason)
*/
/* pull argc and argv off the stack. We are going to push 3
* arguments, so pop one here to maintain doubleword alignment. */
pop {a2}
ldr a3, [sp]
#endif
/* Push stack limit and rtld_fini */
push {a1, a3}
#ifdef __PIC__
ldr r4, .L_GOT
adr r5, .L_GOT
add r4, r5, r4
ldr r5, .L_GOT+4 /* _fini */
ldr a1, [r4, r5]
push {a1} /* Push _fini */
ldr r5, .L_GOT+8 /* _init */
ldr a4, [r4, r5]
ldr r5, .L_GOT+12 /* main */
ldr a1, [r4, r5]
#else
/* Fetch address of fini */
ldr r4, =_fini
/* Push fini */
push {r4}
/* Set up the other arguments in registers */
ldr a1, =main
ldr a4, =_init
#endif
/* __uClibc_main (main, argc, argv, init, fini, rtld_fini, stack_end) */
/* Let the libc call main and exit with its return code. */
bl __uClibc_main
/* should never get here....*/
bl abort
.pool
#ifdef __PIC__
.L_GOT:
.word _GLOBAL_OFFSET_TABLE_-.L_GOT
.word _fini(GOT)
.word _init(GOT)
.word main(GOT)
#endif
#else /* !THUMB1_ONLY */
_start:
/* Clear the frame pointer and link register since this is the outermost frame. */
mov fp, #0
mov lr, #0
#ifdef __ARCH_USE_MMU__
/* Pop argc off the stack and save a pointer to argv */
ldr a2, [sp], #4
mov a3, sp
#else
/*
* uClinux/arm stacks look a little different from normal
* MMU-full Linux/arm stacks (for no good reason)
*/
/* pull argc and argv off the stack. We are going to push 3
* arguments, so pop one here to maintain doubleword alignment. */
ldr a2, [sp], #4
ldr a3, [sp]
#endif
/* Push stack limit */
str a3, [sp, #-4]!
/* Push rtld_fini */
str a1, [sp, #-4]!
#ifdef __PIC__
ldr sl, .L_GOT
adr a4, .L_GOT
add sl, sl, a4
ldr ip, .L_GOT+4 /* _fini */
ldr a1, [sl, ip]
str a1, [sp, #-4]! /* Push _fini */
ldr ip, .L_GOT+8 /* _init */
ldr a4, [sl, ip]
ldr ip, .L_GOT+12 /* main */
ldr a1, [sl, ip]
/* __uClibc_main (main, argc, argv, init, fini, rtld_fini, stack_end) */
/* Let the libc call main and exit with its return code. */
b __uClibc_main(PLT)
#else
/* Fetch address of fini */
ldr ip, =_fini
/* Push fini */
str ip, [sp, #-4]!
/* Set up the other arguments in registers */
ldr a1, =main
ldr a4, =_init
/* __uClibc_main (main, argc, argv, init, fini, rtld_fini, stack_end) */
/* Let the libc call main and exit with its return code. */
b __uClibc_main
#endif
/* should never get here....*/
bl abort
#ifdef __PIC__
.L_GOT:
.word _GLOBAL_OFFSET_TABLE_ - .L_GOT
.word _fini(GOT)
.word _init(GOT)
.word main(GOT)
#endif
#endif
/* 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
|
