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Diffstat (limited to 'c/src/lib/libbsp/mips/jmr3904/start/start.S')
| -rw-r--r-- | c/src/lib/libbsp/mips/jmr3904/start/start.S | 231 |
1 files changed, 231 insertions, 0 deletions
diff --git a/c/src/lib/libbsp/mips/jmr3904/start/start.S b/c/src/lib/libbsp/mips/jmr3904/start/start.S new file mode 100644 index 0000000000..befe8b8b7a --- /dev/null +++ b/c/src/lib/libbsp/mips/jmr3904/start/start.S @@ -0,0 +1,231 @@ +/* + * 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. + */ + +#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 + +/* 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 */ + + .comm __memsize, 12 + .comm __lstack, STARTUP_STACK_SIZE + .comm __stackbase,4 + + .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 +#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 get_mem_info .text + .globl __stack + .globl __global + .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, __lstack # make a small stack so we + addiu sp, t0, STARTUP_STACK_SIZE # can run some C code + la a0, __memsize # get the usable memory size + jal get_mem_info + nop + + /* setup the stack pointer */ + LA (t0, __stack) # is __stack set ? + bne t0,zero,4f + nop + + /* NOTE: a0[0] contains the amount of memory available, and + not the last memory address. */ + lw t0,0(a0) # last address of memory available + la t1,K0BASE # cached kernel memory + addu t0,t0,t1 # get the end of memory address + /* 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 # and generate a starting stack-pointer +4: + move sp,t0 # set stack pointer + sw sp,__stackbase # keep this for future ref + .end zerobss + +/* + * initialize target specific stuff. Only execute these + * functions it they exist. + */ +#if 0 + .globl hardware_init_hook .text + .globl software_init_hook .text + .globl __do_global_dtors .text + .globl atexit .text +#endif + .globl exit .text + .globl init + .ent init +init: +#if 0 + 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 hardware if needed + beq t9,zero,7f + nop + jal t9 + nop +7: + LA (a0, __do_global_dtors) + jal atexit + nop +#endif + +#ifdef GCRT0 + .globl _ftext + .globl _extext + LA (a0, _ftext) + LA (a1, _etext) + jal monstartup + nop +#endif + + move a0,zero # set argc to 0 + jal boot_card # 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 _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 _exit + +/* EOF crt0.S */ |