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/*
* 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 */
|
