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/* Startup code compliant to the ELF SPARC ABI.
Copyright (C) 1996 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 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., 675 Mass Ave,
Cambridge, MA 02139, USA. */
/* This is the canonical entry point, usually the first thing in the text
segment. The SVR4/SPARC ABI (NOTE: I don't actually have it) says that
when the entry point runs, most registers' values are unspecified,
except for:
%g1 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
*/
.text
.align 16
.global _start
_start:
/* %g1 contains the address of the shared library termination
function, which we will register with `atexit' to be called by
`exit'. I suspect that on some systems, and when statically
linked, this will not be set by anything to any function
pointer; hopefully it will be zero so we don't try to call
random pointers. */
orcc %g1, %g0, %o0 /* Move %g1 to %o0 while testing it. */
be nofini
/* In delay slot: clear the frame pointer. The ABI suggests this
be done, to mark the outermost frame obviously. */
clr %fp
/* Call atexit, argument was set in %o0 above. */
call atexit
nop
nofini:
/* We will use some local variables in registers below. %g1 and
the %oN registers are call-clobbered, so we can't just use them. */
#define ARGC %l0
#define ARGV %l1
#define ENVP %l2
#define TMP %l3
/* Do essential libc initialization. In statically linked
programs under the GNU Hurd, this is what sets up the
arguments on the stack for the code below. */
call __libc_init_first
sethi %hi(_environ), TMP /* In delay slot: prepare to use &_environ. */
/* Extract the arguments and environment as encoded on the stack
and save them in local variables. */
ld [%sp + 64], ARGC /* After the register save area, ARGC. */
add %sp, 64+4, ARGV /* Next, the ARGV elements. */
/* After ARGC words that are the ARGV elements, and a zero word,
are the ENVP elements. Do ENVP = &ARGV[ARGC + 1]. */
add ARGC, 1, ENVP
sll ENVP, 2, ENVP
add ARGV, ENVP, ENVP
/* Store ENVP in the global variable `_environ'. */
st [TMP + %lo(_environ)], ENVP
/* Call `_init', which is the entry point to our own `.init'
section; and register with `atexit' to have `exit' call
`_fini', which is the entry point to our own `.fini' section. */
call _init
sethi %hi(_fini), TMP /* In delay slot of call. */
or TMP, %lo(_fini), %o0 /* Argument to atexit is &_fini. */
call atexit
nop
/* Call the user's main function, and exit with its value. */
mov ARGC, %o0
mov ARGV, %o1
call main
mov ENVP, %o2
call exit /* This should never return. */
unimp 0 /* Crash if somehow it does return. */
/* Define a symbol for the first piece of initialized data. */
.data
.global __data_start
__data_start:
.long 0
.weak data_start
data_start = __data_start
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