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/* Startup code compliant to the ELF Xtensa ABI.
Copyright (C) 2001, 2007 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/>. */
#include <features.h>
#ifndef __UCLIBC_CTOR_DTOR__
.weak _init
.weak _fini
#endif
/* This is the canonical entry point, usually the first thing in the text
segment. When the entry point runs, most register values are unspecified,
except for:
a2 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.
a1 The stack (i.e., a1+16) contains the arguments and environment:
a1+0 argc
a1+4 argv[0]
...
a1+(4*argc) NULL
a1+(4*(argc+1)) envp[0]
...
NULL
Setup parameters accordingly (for a call4). See function prototype
from sysdeps/generic/libc-start.c
a6 = *main
a7 = argc
a8 = ubp_av
a9 = *init
a10 = *fini
a11 = *rtld_fini
[sp+0] = stack_end
*/
.text
.align 4
.literal_position
.global _start
.type _start, @function
_start:
#if defined(__XTENSA_WINDOWED_ABI__)
/* Clear a0 to obviously mark the outermost frame. */
movi a0, 0
/* Load up the user's main function. */
movi a6, main
/* Extract the arguments as encoded on the stack and set up
the arguments for `main': argc, argv. envp will be determined
later in __uClibc_main. */
l32i a7, a1, 0 /* Load the argument count. */
addi a8, a1, 4 /* Compute the argv pointer. */
/* Push address of our own entry points to .fini and .init. */
movi a9, _init
movi a10, _fini
/* Setup the shared library termination function. */
mov a11, a2
/* Provide the highest stack address to the user code (for stacks
which grow downwards). Note that we destroy the stack version
of argc here. */
s32i a1, a1, 0
/* Call the user's main function, and exit with its value.
But let the libc call main. */
movi a4, __uClibc_main
callx4 a4
#elif defined(__XTENSA_CALL0_ABI__)
/* Setup the shared library termination function. */
mov a7, a2
/* Load up the user's main function. */
movi a2, main
/* Extract the arguments as encoded on the stack and set up
the arguments for `main': argc, argv. envp will be determined
later in __uClibc_main. */
l32i a3, a1, 0 /* Load the argument count. */
addi a4, a1, 4 /* Compute the argv pointer. */
/* Push address of our own entry points to .fini and .init. */
movi a5, _init
movi a6, _fini
/* Provide the highest stack address to the user code (for stacks
which grow downwards). Note that we destroy the stack version
of argc here. */
s32i a1, a1, 0
/* Call the user's main function, and exit with its value.
But let the libc call main. */
movi a0, __uClibc_main
callx0 a0
#else
#error Unsupported Xtensa ABI
#endif
/* Crash if somehow `exit' does return. */
ill
/* Define a symbol for the first piece of initialized data. */
.data
.align 4
.global __data_start
__data_start:
.long 0
.weak data_start
data_start = __data_start
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