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/* Startup code compliant to the ELF s390 ABI.
Copyright (C) 2000, 2001 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 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. 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
4(%r15) argv[0]
...
(4*argc)(%r15) NULL
(4*(argc+1))(%r15) envp[0]
...
NULL
*/
.text
.globl _start
type _start,@function
_start:
/* Setup pointer to literal pool of _start */
basr %r13,0
.L0: ahi %r13,.Llit-.L0
/* load argc and argv from stack */
la %r4,4(%r15) # get argv
l %r3,0(%r15) # get argc
/* align the stack to a double word boundary */
lhi %r0,-8
nr %r15,%r0
/* Setup a stack frame and a parameter area */
ahi %r15,-104 # make room on stack
xc 0(4,%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
*/
stm %r14,%r15,96(%r15) # store rtld_fini/stack_end to parameter area
la %r7,96(%r15)
l %r6,.L2-.Llit(%r13) # load pointer to _fini
l %r5,.L1-.Llit(%r13) # load pointer to _init
l %r2,.L3-.Llit(%r13) # load pointer to main
/* ok, now branch to the libc main routine */
l %r1,.L4-.Llit(%r13)
basr %r14,%r1
/* crash if __libc_start_main returns */
.word 0
.Llit:
.L1: .long _init
.L2: .long _fini
.L3: .long main
.L4: .long __libc_start_main
/* FIXME: FPU flags or what ?!? */
.section .rodata
.globl _fp_hw
.long 3
.size _fp_hw, 4
/* 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
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