mirror of
https://github.com/autc04/Retro68.git
synced 2024-12-04 01:50:38 +00:00
174 lines
4.3 KiB
ArmAsm
174 lines
4.3 KiB
ArmAsm
/*
|
|
* crt0_cygmon.S -- Minimal startup file for MIPS targets running Cygmon.
|
|
*
|
|
* Copyright (c) 1995, 1996, 1997, 2000 Red Hat, Inc.
|
|
*
|
|
* The authors hereby grant permission to use, copy, modify, distribute,
|
|
* and license this software and its documentation for any purpose, provided
|
|
* that existing copyright notices are retained in all copies and that this
|
|
* notice is included verbatim in any distributions. No written agreement,
|
|
* license, or royalty fee is required for any of the authorized uses.
|
|
* Modifications to this software may be copyrighted by their authors
|
|
* and need not follow the licensing terms described here, provided that
|
|
* the new terms are clearly indicated on the first page of each file where
|
|
* they apply.
|
|
*/
|
|
|
|
/*
|
|
* This file contains the minimal startup code necessary.
|
|
* This will not do any hardware initialization. It is assumed that we are talking to Cygmon
|
|
* and therefore the hardware will be initialized properly.
|
|
*/
|
|
|
|
#ifdef __mips16
|
|
/* This file contains 32 bit assembly code. */
|
|
.set nomips16
|
|
#endif
|
|
|
|
#include "regs.S"
|
|
|
|
/*
|
|
* Set up some room for a stack. We just grab a chunk of memory.
|
|
*/
|
|
#define STACK_SIZE 0x4000
|
|
#define GLOBAL_SIZE 0x2000
|
|
|
|
#define STARTUP_STACK_SIZE 0x0100
|
|
|
|
.comm __memsize, 12
|
|
.comm __lstack, STARTUP_STACK_SIZE
|
|
.comm __stackbase,4
|
|
|
|
.text
|
|
.align 4
|
|
/*
|
|
* Without the following nop, GDB thinks _start is a data variable.
|
|
* This is probably a bug in GDB in handling a symbol that is at the
|
|
* start of the .text section.
|
|
*/
|
|
nop
|
|
|
|
.globl _start
|
|
.ent _start
|
|
_start:
|
|
.set noreorder
|
|
la gp, _gp # set the global data pointer, defined in the linker script
|
|
.end _start
|
|
|
|
/*
|
|
* zero out the bss section.
|
|
*/
|
|
.globl __memsize
|
|
.globl get_mem_info .text
|
|
.globl zerobss
|
|
.ent zerobss
|
|
zerobss:
|
|
la v0, _fbss # These variables are defined in the linker script
|
|
la v1, _end
|
|
|
|
3:
|
|
sw zero, 0(v0)
|
|
bltu v0, v1, 3b
|
|
addiu v0, v0, 4 # executed in delay slot
|
|
|
|
/*
|
|
* Setup a small stack so we can run some C code,
|
|
* and get the usable memory size.
|
|
*/
|
|
la t0, __lstack
|
|
addiu sp, t0, STARTUP_STACK_SIZE
|
|
la a0, __memsize
|
|
jal get_mem_info
|
|
nop
|
|
|
|
/*
|
|
* Setup the stack pointer --
|
|
* get_mem_info returns the top of memory, so just use that In
|
|
* addition, we must subtract 24 bytes for the 3 8 byte
|
|
* arguments to main, in case main wants to write them back to
|
|
* the stack. The caller is supposed to allocate stack space
|
|
* for parameters in registers in the old MIPS ABIs. We must
|
|
* do this even though we aren't passing arguments, because
|
|
* main might be declared to have them.
|
|
* Some ports need a larger alignment for the stack, so we
|
|
* subtract 32, which satisifes the stack for the arguments and
|
|
* keeps the stack pointer better aligned.
|
|
*/
|
|
subu v0, v0, 32
|
|
move sp, v0
|
|
|
|
sw sp, __stackbase # keep this for future ref
|
|
.end zerobss
|
|
|
|
/*
|
|
* initialize target specific stuff. Only execute these
|
|
* functions it they exist.
|
|
*/
|
|
.globl hardware_init_hook .text
|
|
.globl software_init_hook .text
|
|
.globl __do_global_dtors .text
|
|
.globl atexit .text
|
|
.globl exit .text
|
|
.globl init
|
|
.ent init
|
|
init:
|
|
la t9, hardware_init_hook # init the hardware if needed
|
|
beq t9, zero, 6f
|
|
nop
|
|
jal t9
|
|
nop
|
|
6:
|
|
la t9, software_init_hook # init the software if needed
|
|
beq t9, zero, 7f
|
|
nop
|
|
jal t9
|
|
nop
|
|
7:
|
|
la a0, __do_global_dtors
|
|
jal atexit
|
|
nop
|
|
|
|
#ifdef GCRT0
|
|
.globl _ftext
|
|
.globl _extext
|
|
la a0, _ftext
|
|
la a1, _etext
|
|
jal monstartup
|
|
nop
|
|
#endif
|
|
|
|
move a0,zero # set argc to 0
|
|
jal main # call the program start function
|
|
nop
|
|
|
|
# fall through to the "exit" routine
|
|
jal exit # call libc exit to run the G++
|
|
# destructors
|
|
move a0, v0 # pass through the exit code
|
|
.end init
|
|
|
|
/*
|
|
* _exit -- Exit from the application. Normally we cause a user trap
|
|
* to return to the ROM monitor for another run. NOTE: This is
|
|
* the only other routine we provide in the crt0.o object, since
|
|
* it may be tied to the "_start" routine. It also allows
|
|
* executables that contain a complete world to be linked with
|
|
* just the crt0.o object.
|
|
*/
|
|
.globl _exit
|
|
.ent _exit
|
|
_exit:
|
|
7:
|
|
#ifdef GCRT0
|
|
jal _mcleanup
|
|
nop
|
|
#endif
|
|
# Cygmon expects a break 5
|
|
break 5
|
|
nop
|
|
b 7b # loop back just in-case
|
|
nop
|
|
.end _exit
|
|
|
|
/* EOF crt0.S */
|