libc/libgloss/mips/crt0.S

317 lines
7.3 KiB
ArmAsm

/*
* crt0.S -- startup file for MIPS.
*
* Copyright (c) 1995, 1996, 1997, 2001 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.
*/
/* This file does not use any floating-point ABI. */
.gnu_attribute 4,0
#ifdef __mips16
/* This file contains 32 bit assembly code. */
.set nomips16
#endif
#include "regs.S"
#include "abiflags.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
.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 hardware_hazard_hook .text
.globl _start
.ent _start
_start:
#ifdef __mips_embedded_pic
#define PICBASE start_PICBASE
.set noreorder
PICBASE = .+8
bal PICBASE
nop
move s0,$31
.set reorder
#endif
#if __mips<3
# define STATUS_MASK (SR_CU1|SR_PE)
#else
/* Post-mips2 has no SR_PE bit. */
# ifdef __mips64
/* Turn on 64-bit addressing and additional float regs. */
# define STATUS_MASK (SR_CU1|SR_FR|SR_KX|SR_SX|SR_UX)
# else
# if __mips_fpr==32
# define STATUS_MASK (SR_CU1)
# else
/* Turn on additional float regs. */
# define STATUS_MASK (SR_CU1|SR_FR)
# endif
# endif
#endif
/* Clear Cause register. */
mtc0 zero,C0_CAUSE
nop
/* Read MIPS_abiflags structure and set status/config registers
accordingly. */
.weak __MIPS_abiflags_start
.weak __MIPS_abiflags_end
LA (t0,__MIPS_abiflags_start)
LA (t1,__MIPS_abiflags_end)
addiu t1,t1,-24
move v0,zero /* Mask for C0_SR. */
/* Branch to 1f is the .MIPS.abiflags section is not 24 bytes. This
indicates it is either missing or corrupt. */
bne t0,t1,1f
/* Check isa_level. */
lbu t1,ABIFlags_isa_level(t0)
sltu v1,t1,3 /* Is MIPS < 3? */
xori t1,t1,64 /* Is MIPS64? */
beq v1,zero,4f
li v1,SR_PE
or v0,v0,v1 /* Enable soft reset. */
4:
li v1,(SR_KX|SR_SX|SR_UX)
bne t1,zero,5f
or v0,v0,v1 /* Enable extended addressing. */
5:
/* Check fp_abi. */
lbu t1,ABIFlags_fp_abi(t0)
xori t1,t1,Val_GNU_MIPS_ABI_FP_SOFT
li v1,SR_CU1
beq t1,zero,2f /* Skip MSA and cpr1_size checks. */
or v0,v0,v1 /* Enable co-processor 1. */
/* Check cpr1_size. */
lbu t1,ABIFlags_cpr1_size(t0)
xori t1,t1,AFL_REG_64
li v1,SR_FR
bne t1,zero,3f
or v0,v0,v1 /* Enable 64-bit FPU registers. */
3:
/* Check ases. */
lw t1,ABIFlags_ases(t0)
andi t1,t1,AFL_ASE_MSA
li v1,SR_FR
beq t1,zero,2f
or v0,v0,v1 /* Enable 64-bit FPU registers. */
li v1,SR_MSA
.set push
.set mips32
mtc0 v1,C0_CONFIG,5 /* Enable MSA. */
.set pop
b 2f
1:
/* MIPS_abiflags structure is not available. Set status/config
registers based on flags defined by compiler. */
#ifdef __mips_soft_float
li v0,(STATUS_MASK-(STATUS_MASK & SR_CU1))
#else
li v0,STATUS_MASK
#endif
2:
/* Set C0_SR, */
mtc0 v0,C0_SR
nop
/* Avoid hazard from C0_SR changes. */
LA (t0, hardware_hazard_hook)
beq t0,zero,2f
jalr t0
2:
/* Fix high bits, if any, of the PC so that exception handling doesn't get
confused. */
LA (v0, 3f)
jr v0
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
.ent zerobss
zerobss:
LA (v0, _fbss)
LA (v1, _end)
beq v0,v1,2f
1:
addiu v0,v0,4
sw zero,-4(v0)
bne v0,v1,1b
2:
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
/* setup the stack pointer */
LA (t0, __stack) # is __stack set ?
bne t0,zero,4f
/* NOTE: a0[0] contains the amount of memory available, and
not the last memory address. */
la a0, __memsize
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
/* Allocate 32 bytes for the register parameters. Allocate 16
bytes for a null argv and envp. Round the result up to 64
bytes to preserve alignment. */
subu t0,t0,64
4:
move sp,t0 # set stack pointer
.end zerobss
/*
* initialize target specific stuff. Only execute these
* functions it they exist.
*/
.globl hardware_init_hook .text
.globl software_init_hook .text
.type _fini,@function
.type _init,@function
.globl atexit .text
.globl exit .text
.ent init
init:
LA (t9, hardware_init_hook) # init the hardware if needed
beq t9,zero,6f
jalr t9
6:
LA (t9, software_init_hook) # init the hardware if needed
beq t9,zero,7f
jalr t9
7:
LA (a0, _fini)
jal atexit
#ifdef GCRT0
.globl _ftext
.globl _extext
LA (a0, _ftext)
LA (a1, _etext)
jal monstartup
#endif
jal _init # run global constructors
addiu a1,sp,32 # argv = sp + 32
addiu a2,sp,40 # envp = sp + 40
#if __mips64
sd zero,(a1) # argv[argc] = 0
sd zero,(a2) # envp[0] = 0
#else
sw zero,(a1)
sw zero,(a2)
#endif
move a0,zero # set argc to 0
jal main # call the program start function
# fall through to the "exit" routine
move a0,v0 # pass through the exit code
jal exit # call libc exit to run the G++
# destructors
.end init
/* Assume the PICBASE set up above is no longer valid below here. */
#ifdef __mips_embedded_pic
#undef PICBASE
#endif
/*
* _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 hardware_exit_hook .text
.globl _exit
.ent _exit
_exit:
7:
#ifdef __mips_embedded_pic
/* Need to reinit PICBASE, since we might be called via exit()
rather than via a return path which would restore old s0. */
#define PICBASE exit_PICBASE
.set noreorder
PICBASE = .+8
bal PICBASE
nop
move s0,$31
.set reorder
#endif
#ifdef GCRT0
LA (t0, _mcleanup)
jalr t0
#endif
LA (t0, hardware_exit_hook)
beq t0,zero,1f
jalr t0
1:
# break instruction can cope with 0xfffff, but GAS limits the range:
break 1023
b 7b # but loop back just in-case
.end _exit
/* Assume the PICBASE set up above is no longer valid below here. */
#ifdef __mips_embedded_pic
#undef PICBASE
#endif
/* EOF crt0.S */