blob: 61b191468625f170c2245121b774e3b73a7141b1 (
plain) (
blame)
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
|
# Print the (hex) textual representation of the lowest byte of a number.
== code
# instruction effective address register displacement immediate
# . op subop mod rm32 base index scale r32
# . 1-3 bytes 3 bits 2 bits 3 bits 3 bits 3 bits 2 bits 2 bits 0/1/2/4 bytes 0/1/2/4 bytes
# main:
e8/call run-tests/disp32 # 'run-tests' is a function created automatically by SubX. It calls all functions that start with 'test-'.
# syscall(exit, Num-test-failures)
8b/copy 0/mod/indirect 5/rm32/.disp32 . . 3/r32/EBX Num-test-failures/disp32 # copy *Num-test-failures to EBX
b8/copy-to-EAX 1/imm32/exit
cd/syscall 0x80/imm8
print-byte: # f : (address buffered-file), n : int -> <void>
# . prolog
55/push-EBP
89/copy 3/mod/direct 5/rm32/EBP . . . 4/r32/ESP . . # copy ESP to EBP
# . save registers
50/push-EAX
# AL = convert upper nibble to hex
8b/copy 1/mod/*+disp8 4/rm32/sib 5/base/EBP 4/index/none . 0/r32/EAX 0xc/disp8 . # copy *(EBP+12) to EAX
c1/shift 5/subop/logic-right 3/mod/direct 0/rm32/EAX . . . . . 4/imm8 # shift EAX right by 4 bits, while padding zeroes
# . hex-char(AL)
# . . push args
50/push-EAX
# . . call
e8/call hex-char/disp32
# . . discard args
81 0/subop/add 3/mod/direct 4/rm32/ESP . . . . . 4/imm32 # add to ESP
# write-byte(f, AL)
# . . push args
50/push-EAX
ff 6/subop/push 1/mod/*+disp8 4/rm32/sib 5/base/EBP 4/index/none . . 8/disp8 . # push *(EBP+8)
# . . call
e8/call write-byte/disp32
# . . discard args
81 0/subop/add 3/mod/direct 4/rm32/ESP . . . . . 8/imm32 # add to ESP
# AL = convert lower nibble to hex
8b/copy 1/mod/*+disp8 4/rm32/sib 5/base/EBP 4/index/none . 0/r32/EAX 0xc/disp8 . # copy *(EBP+12) to EAX
25/and-EAX 0xf/imm32
# . hex-char(AL)
# . . push args
50/push-EAX
# . . call
e8/call hex-char/disp32
# . . discard args
81 0/subop/add 3/mod/direct 4/rm32/ESP . . . . . 4/imm32 # add to ESP
# write-byte(f, AL)
# . . push args
50/push-EAX
ff 6/subop/push 1/mod/*+disp8 4/rm32/sib 5/base/EBP 4/index/none . . 8/disp8 . # push *(EBP+8)
# . . call
e8/call write-byte/disp32
# . . discard args
81 0/subop/add 3/mod/direct 4/rm32/ESP . . . . . 8/imm32 # add to ESP
$print-byte:end:
# . restore registers
59/pop-to-ECX
58/pop-to-EAX
# . epilog
89/copy 3/mod/direct 4/rm32/ESP . . . 5/r32/EBP . . # copy EBP to ESP
5d/pop-to-EBP
c3/return
# extract lowest 4 bits and convert to 8-byte ascii
# return 0xffffffff if more than 4 bits are set
hex-char: # n : int -> char_or_error/EAX
# . prolog
55/push-EBP
89/copy 3/mod/direct 5/rm32/EBP . . . 4/r32/ESP . . # copy ESP to EBP
# EAX = n
8b/copy 1/mod/*+disp8 4/rm32/sib 5/base/EBP 4/index/none . 0/r32/EAX 8/disp8 . # copy *(EBP+8) to EAX
# if it's <= 9 add '0' to it
81 7/subop/compare 3/mod/direct 0/rm32/EAX . . . . . 0x9/imm32 # compare EAX
7f/jump-if-greater $hex-char:check2/disp8
05/add-to-EAX 0x30/imm32/'0'
eb/jump $hex-char:end/disp8
$hex-char:check2:
# else if it's <= 15 add ('a' - 10) to it
81 7/subop/compare 3/mod/direct 0/rm32/EAX . . . . . 0xf/imm32 # compare EAX
7f/jump-if-greater $hex-char:error/disp8
05/add-to-EAX 0x57/imm32 # 'a' - 10
eb/jump $hex-char:end/disp8
$hex-char:error:
# otherwise return 0xffffffff
b8/copy-to-EAX 0xffffffff/imm32
$hex-char:end:
# . epilog
89/copy 3/mod/direct 4/rm32/ESP . . . 5/r32/EBP . . # copy EBP to ESP
5d/pop-to-EBP
c3/return
test-print-byte:
# - check that print-byte prints the hex textual representation
# setup
# . clear-stream(_test-stream)
# . . push args
68/push _test-stream/imm32
# . . call
e8/call clear-stream/disp32
# . . discard args
81 0/subop/add 3/mod/direct 4/rm32/ESP . . . . . 4/imm32 # add to ESP
# . clear-stream(_test-buffered-file+4)
# . . push args
b8/copy-to-EAX _test-buffered-file/imm32
05/add-to-EAX 4/imm32
50/push-EAX
# . . call
e8/call clear-stream/disp32
# . . discard args
81 0/subop/add 3/mod/direct 4/rm32/ESP . . . . . 4/imm32 # add to ESP
# print-byte(_test-buffered-file, 0xa) # exercises digit, non-digit as well as leading zero
# . . push args
68/push 0xa/imm32
68/push _test-buffered-file/imm32
# . . call
e8/call print-byte/disp32
# . . discard args
81 0/subop/add 3/mod/direct 4/rm32/ESP . . . . . 8/imm32 # add to ESP
# flush(_test-buffered-file)
# . . push args
68/push _test-buffered-file/imm32
# . . call
e8/call flush/disp32
# . . discard args
81 0/subop/add 3/mod/direct 4/rm32/ESP . . . . . 4/imm32 # add to ESP
# check-ints-equal(*_test-stream->data, '0a', msg)
# . . push args
68/push "F - test-print-byte"/imm32
68/push 0x6130/imm32/0a
# . . push *_test-stream->data
b8/copy-to-EAX _test-stream/imm32
ff 6/subop/push 1/mod/*+disp8 0/rm32/EAX . . . . 0xc/disp8 . # push *(EAX+12)
# . . call
e8/call check-ints-equal/disp32
# . . discard args
81 0/subop/add 3/mod/direct 4/rm32/ESP . . . . . 0xc/imm32 # add to ESP
# . end
c3/return
# . . vim:nowrap:textwidth=0
|