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/*
* start.S -- startup file for JMR3904 BSP based upon crt0.S from
* newlib-1.8.2/libgloss/mips and adapted for RTEMS.
*
* crt0.S -- startup file for MIPS.
*
* Copyright (c) 1995, 1996, 1997 Cygnus Support
*
* 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.
*/
#include <rtems/asm.h>
#include <bsp/regs.h>
#ifdef __mips16
/* This file contains 32 bit assembly code. */
.set nomips16
#endif
/* This is for referencing addresses that are not in the .sdata or
.sbss section under embedded-pic, or before we've set up gp. */
#ifdef __mips_embedded_pic
# ifdef __mips64
# define LA(t,x) la t,x-PICBASE ; daddu t,s0,t
# else
# define LA(t,x) la t,x-PICBASE ; addu t,s0,t
# endif
#else /* __mips_embedded_pic */
# define LA(t,x) la t,x
#endif /* __mips_embedded_pic */
.text
.align 2
/* 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
/* Get the address of start into $5 in a position independent fashion.
** This lets us know whether we have been relocated or not.
*/
$LF1 = . + 8
bal $LF1
nop
_branch:
move $5, $31 # $5 == where are we
li $6, 0x8800000c # $6 == where we want to be
/* #la $6,_branch */
beq $5, $6, _start_in_ram
nop
/* relocate the code from EEPROM to RAM */
la $7, _edata
relocate:
lw $8, ($5) # $8 = *EEPROM
addu $5, $5, 4 # EEPROM++
sw $8, ($6) # *RAM = $8
addu $6, $6, 4 # RAM++
bne $6, $7, relocate # copied all the way to edata?
nop
la $6, _start_in_ram
jr $6
nop
.end _start
.globl _start_in_ram
.ent _start_in_ram
_start_in_ram:
nop
#ifdef __mips_embedded_pic
PICBASE = .+8
bal PICBASE
nop
move s0,$31
#endif
li v0, SR_CU1|SR_PE|SR_FR|SR_KX|SR_SX|SR_UX
mtc0 v0, C0_SR
mtc0 zero, C0_CAUSE
/* Check for FPU presence */
#ifndef __mips_soft_float
/* This doesn't work if there is no FPU. We get illegal instruction
exceptions. */
li t2,0xAAAA5555
mtc1 t2,fp0 /* write to FPR 0 */
mtc1 zero,fp1 /* write to FPR 1 */
mfc1 t0,fp0
mfc1 t1,fp1
nop
bne t0,t2,1f /* check for match */
nop
bne t1,zero,1f /* double check */
nop
#ifndef __mips64 /* Clear the FR bit */
li v0, SR_CU1|SR_PE|SR_KX|SR_SX|SR_UX
mtc0 v0, C0_SR
#endif
j 2f
nop
#endif
1:
li v0, SR_PE|SR_FR|SR_KX|SR_SX|SR_UX
mtc0 v0, C0_SR
2:
/* Fix high bits, if any, of the PC so that exception handling
doesn't get confused. */
LA (v0, 3f)
jr v0
nop
3:
LA (gp, _gp) # set the global data pointer
.end _start_in_ram
/*
* zero out the bss section.
*/
.globl zerobss
.ent zerobss
zerobss:
LA (v0, _fbss)
LA (v1, _end)
3:
sw zero,0(v0)
bltu v0,v1,3b
addiu v0,v0,4 # executed in delay slot
la t0, _Configuration_Interrupt_stack_area_end # initialize stack so we
/* 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 t0,t0,32
move sp,t0 # set stack pointer
.end zerobss
.globl exit .text
.globl init
.ent init
init:
move a0,zero # set command line to 0
jal boot_card # call the program start function
nop
/* fall through to the "exit" routine */
jal _sys_exit /* call libc exit to run the G++ */
/* destructors */
move a0,v0 /* pass through the exit code */
.end init
/*
* _sys_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 bsp_reset
bsp_reset:
.globl _sys_exit
.ent _sys_exit
_sys_exit:
7:
#ifdef GCRT0
jal _mcleanup
nop
#endif
/* break instruction can cope with 0xfffff, but GAS limits the range: */
break 1023
nop
b 7b # but loop back just in-case
nop
.end _sys_exit
/* EOF crt0.S */
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