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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.
*/
#define PMON_UTIL_ROUTINES 0xbfc00200
#define UTIL_WARMSTART_VECTOR 21*4
#define UTIL_CPUINIT_VECTOR 22*4
#define UTIL_CONFIGUART_VECTOR 23*4
#define UTIL_PUTCHROM_VECTOR 24*4
#include <asm.h>
#include "regs.S"
#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 */
/* defined by linkcmds, pointing to the start of the relocation target
memory, referenced in this way so we can avoid defining it
multiply */
.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 a1, ra /* save return address from the jump above */
/* call down into PMON's CpuInit, so we avoid having to
duplicate all that code plus remember to update both copies
when something changes... Note, a1 must be preserved by
CpuInit */
li t7,PMON_UTIL_ROUTINES /* get base address of pmon's vector table */
lw t0,UTIL_CPUINIT_VECTOR(t7)
nop
jal t0 /* init cpu */
nop
lw t0,UTIL_CONFIGUART_VECTOR(t7)
nop
jal t0 /* reconfigure UART for console output */
nop
lw t0,UTIL_PUTCHROM_VECTOR(t7)
li a0,'b' /* show we booted */
jal t0
/*
get the address of the _branch label above as it would appear in
the relocated code
*/
la a2, _branch /* relocation destination */
beq a1, a2, _start_in_ram /* skip relocating if we're already there */
nop
/* relocate the code from EEPROM to RAM */
lw t0,UTIL_PUTCHROM_VECTOR(t7)
li a0,'r' /* show we're starting relocation */
jal t0
la a3, _edata
relocate:
lw t0, (a1) /* load from EEPROM */
addu a1, 4
sw t0, (a2) /* store to RAM */
addu a2, 4
bne a2, a3, relocate /* copied all the way to edata? */
nop
lw t0,UTIL_PUTCHROM_VECTOR(t7)
li a0,'R' /* show we relocated */
jal t0
nop
la a2, _start_in_ram
jr a2
nop
.end _start
.globl _start_in_ram
.ent _start_in_ram
_start_in_ram:
lw t0,UTIL_PUTCHROM_VECTOR(t7)
li a0,'S' /* show we're starting in the target address range */
jal t0
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
/*
* zero out the bss section.
*/
.globl __memsize
.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, _stack_init # 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 argc 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 _sys_exit
.ent _sys_exit
_sys_exit:
#ifdef GCRT0
jal _mcleanup
nop
#endif
/* return non-zero if we want default behavior, else return to pmon */
bne a0,zero,7f
nop
li t0,PMON_UTIL_ROUTINES /* base address of PMON's util_routines table */
lw t0,UTIL_WARMSTART_VECTOR(t0) /* retrieve _warmstart vector at offset 21*4 */
nop
j t0 /* and jump */
nop
# break instruction can cope with 0xfffff, but GAS limits the range:
7: break 1023
nop
b 7b # but loop back just in-case
nop
.end _sys_exit
/* EOF crt0.S */
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