1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
|
/*
* 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
#if __mips < 3
#define STATUS_MASK (SR_CU1|SR_PE)
#else
# For mips3 or mips4, turn on 64-bit addressing and additional float regs
#define STATUS_MASK (SR_CU1|SR_PE|SR_FR|SR_KX|SR_SX|SR_UX)
#endif
li v0, STATUS_MASK
mtc0 v0, C0_SR
mtc0 zero, C0_CAUSE
nop
/* Check for FPU presence. Don't check if we know that soft_float is
being used. (This also avoids illegal instruction exceptions.) */
#ifndef __mips_soft_float
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
j 2f /* FPU is present. */
nop
#endif
1:
/* FPU is not present. Set status register to say that. */
li v0, (STATUS_MASK-(STATUS_MASK & SR_CU1))
mtc0 v0, C0_SR
nop
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.
*/
.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 hardware 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
# 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 */
|
