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/* Startup code compliant to the ELF Mips ABI.
Copyright (C) 1995-2020 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
<https://www.gnu.org/licenses/>. */
#define __ASSEMBLY__ 1
#include <entry.h>
#include <sgidefs.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
#ifndef __mips16
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 == _ABIO32
PTR_SUBIU $29, 32
# endif
PTR_LA $7, __libc_csu_init /* init */
PTR_LA $8, __libc_csu_fini
# if _MIPS_SIM == _ABIO32
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
PTR_LA $25, __libc_start_main
jalr $25
hlt: b hlt /* Crash if somehow it does return. */
#elif _MIPS_SIM == _ABIO32 /* __mips16 */
/* MIPS16 entry point. */
.set mips16
ENTRY_POINT:
# ifdef __PIC__
li $3, %hi(_gp_disp)
addiu $4, $pc, %lo(_gp_disp)
sll $3, 16
addu $3, $4
move $gp, $3
# else
li $3, %hi(_gp)
sll $3, 16
addiu $3, %lo(_gp)
move $gp, $3
# endif
/* Tie end of stack frames. */
li $4, 0
move $31, $4
/* Create new SP value in $7, including alignment. */
li $4, 2 * SZREG
neg $4, $4
move $7, $sp
and $7, $4
addiu $7, -32
/* Load arguments with original SP. */
lw $5, 0($sp)
addiu $6, $sp, PTRSIZE
/* Update SP. */
move $sp, $7
/* Lay out last arguments, and call __libc_start_main(). */
# ifdef __PIC__
sw $7, 24($sp) /* stack_end */
lw $4, %got(__libc_csu_fini)($3)
lw $7, %got(__libc_csu_init)($3) /* init */
sw $4, 16($sp) /* fini */
lw $4, %got(main)($3) /* main */
lw $3, %call16(__libc_start_main)($3)
sw $2, 20($sp) /* rtld_fini */
move $25, $3
jalr $3
# else
lw $4, 1f
sw $7, 24($sp) /* stack_end */
lw $7, 2f /* init */
sw $4, 16($sp) /* fini */
lw $4, 3f /* main */
sw $2, 20($sp) /* rtld_fini */
/* Load and call __libc_start_main(). */
lw $3, 4f
jalr $3
# endif
hlt: b hlt /* Crash if somehow it does return. */
# ifndef __PIC__
.align 2
1: .word __libc_csu_fini
2: .word __libc_csu_init
3: .word main
4: .word __libc_start_main
# endif
#else /* __mips16 && _MIPS_SIM != _ABIO32 */
# error "MIPS16 support for N32/N64 not implemented"
#endif /* __mips16 */
/* 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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