-
Notifications
You must be signed in to change notification settings - Fork 5
/
elf.S
219 lines (169 loc) · 2.64 KB
/
elf.S
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
# a0 = pointer to the start of an ELF file...
_map_elf:
push ra
lw t0, 0(a0)
li t1, 0x7F454c46
bne t0, t1, _valid_elf
la a0, invalid_elf_warning
call _writeln
j _end_map_elf
_valid_elf:
push a0
la a0, valid_elf
call _writeln
pop a0
lw t0, 0x20(a0)
push a0
mv a0, t0
call _print_hex
pop a0
lw t2, 0x28(a0)
push a0
mv a0, t2
call _print_hex
pop a0
# set t3 to the number of program header entries
lh t3, 0x38(a0)
push a0
mv a0, t3
call _print_hex
pop a0
li a2, 0x0
addi a1, a0, 0x40
push a0
la a0, elf_program_headers
call _writeln
pop a0
_next_program_header:
# t4 = offset of segment in file image
ld t4, 0x08(a1)
# t5 = virtual address
ld t5, 0x10(a1)
# t6 = memsize
ld t6, 0x28(a1)
# t6 = filesize
ld s6, 0x20(a1)
# t4 = file offset
# t5 = virtual address
# t6 = memsize
push a0
mv a0, t4
call _print_hex
pop a0
push a0
mv a0, t5
call _print_hex
pop a0
push a0
mv a0, t6
call _print_hex
pop a0
push a1
push a2
push t5
# calculate how many pages we need
# for the program section (+1)
push t6
push a0
srli t6, t6, 12
addi t6, t6, 1
mv a0, t6
call _kalloc
mv s5, a0
pop a0
pop t6
# t4 = elf offset + start of this section
# a0 = elf offset
# a1 = start of the allocated pages
add s3, a0, t4
li t5, 0
bnez t6, _copy_program_section
pop t5
pop a2
pop a1
j _skip_program_mapping
_copy_program_section:
add a3, s3, t5
lb a2, 0(a3)
add a3, s5, t5
sb a2, 0(a3)
addi t5, t5, 0x1
bne t5, s6, _copy_program_section
push a0
mv a0, a1
call _print_hex
pop a0
pop t5
pop a2
pop a1
push a0
push a1
push a2
# Number of Pages to Map
srli t6, t6, 12
addi t6, t6, 1
li s3, 0
_vmap_sections:
mv a0, t5
mv a1, s5
li a2, 0xF
call _map_to_virtual
li s4, 4096
add t5, t5, s4
add s5, s5, s4
add s3, s3, 0x01
bne s3, t6, _vmap_sections
pop a2
pop a1
pop a0
_skip_program_mapping:
addi a1, a1, 56
addi a2, a2, 0x1
bne a2, t3, _next_program_header
# t0 is incorrect
# Identity Map Stack
push a0
li a0, 0xD0000
la a1, _user_stacks
li a2, 0x0F
call _map_to_virtual
pop a0
push a0
li a0, 0x00000
la a1, _user_zero
li a2, 0x0F
call _map_to_virtual
pop a0
push a0
la a0, _vga_mmio
la a1, _vga_mmio
li a2, 0x0F
call _map_to_virtual
pop a0
push a0
li t0, 0
li s0, 0x0000000050000000
_map_frame_buffer:
mv a0, s0
mv a1, s0
li a2, 0x0F
call _map_to_virtual
li t1, 4096
add s0, s0, t1
li t1, 19
addi t0, t0, 1
bne t0, t1, _map_frame_buffer
pop a0
la a1, _machine_trap_stack
sd sp, 0(a1)
li sp, 0xD1000
#li t0, 0x0000000087FA27F8
ld t0, 0x18(a0)
csrw mepc, t0
mret
_end_map_elf:
pop ra
ret
.align 12
_user_zero:
.skip 65536