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
|
## example showing file syscalls
# Create a file, open it for writing, write a character to it, close it, open
# it for reading, read a character from it, close it, delete it, and return
# the character read.
#
# To run:
# $ subx translate ex8.subx ex8
# $ subx run ex8
# Expected result:
# $ echo $?
# 97
== code
# instruction effective address operand 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
# creat(filename)
bb/copy . . . . . . . filename/imm32 # copy to EBX
b9/copy . . . . . . . 0x180/imm32/fixed-perms # copy to ECX
b8/copy . . . . . . . 8/imm32/creat # copy 8 to EAX
cd/syscall . . . . . . . 0x80/imm8 # int 80h
# stream = open(filename, O_WRONLY, 0) # we can't use 'fd' because it looks like a hex byte
bb/copy . . . . . . . filename/imm32 # copy to EBX
b9/copy . . . . . . . 1/imm32/wronly # copy 1 to ECX
ba/copy . . . . . . . 0x180/imm32/fixed-perms # copy 0 to EDX
b8/copy . . . . . . . 5/imm32/open # copy 5 to EAX
cd/syscall . . . . . . . 0x80/imm8 # int 80h
# save stream
bb/copy . . . . . . . stream/imm32 # copy to EBX
89/copy 0/mod/indirect 3/rm32/EBX 0/r32/EAX # copy EAX to *EBX
# write(stream, "a", 1)
# load stream
bb/copy . . . . . . . stream/imm32 # copy to EBX
8b/copy 0/mod/indirect 3/rm32/EBX 3/r32/EBX # copy *EBX to EBX
#
b9/copy . . . . . . . a/imm32 # copy to ECX
ba/copy . . . . . . . 1/imm32/size # copy 1 to EDX
b8/copy . . . . . . . 4/imm32/write # copy 4 to EAX
cd/syscall . . . . . . . 0x80/imm8 # int 80h
# close(stream)
# load stream
bb/copy . . . . . . . stream/imm32 # copy to EBX
8b/copy 0/mod/indirect 3/rm32/EBX 3/r32/EBX # copy *EBX to EBX
#
b8/copy . . . . . . . 6/imm32/close # copy 6 to EAX
cd/syscall . . . . . . . 0x80/imm8 # int 80h
# stream = open(filename, O_RDONLY, 0)
bb/copy . . . . . . . filename/imm32 # copy to EBX
b9/copy . . . . . . . 0/imm32/rdonly # copy 0 to ECX
ba/copy . . . . . . . 0x180/imm32/fixed-perms # copy to EDX
b8/copy . . . . . . . 5/imm32/open # copy 5 to EAX
cd/syscall . . . . . . . 0x80/imm8 # int 80h
# save stream
bb/copy . . . . . . . stream/imm32 # copy to EBX
89/copy 0/mod/indirect 3/rm32/EBX 0/r32/EAX # copy EAX to *EBX
# read(stream, b, 1)
# load stream
bb/copy . . . . . . . stream/imm32 # copy to EBX
8b/copy 0/mod/indirect 3/rm32/EBX 3/r32/EBX # copy *EBX to EBX
#
b9/copy . . . . . . . b/imm32 # copy to ECX
ba/copy . . . . . . . 1/imm32/size # copy 1 to EDX
b8/copy . . . . . . . 3/imm32/read # copy 3 to EAX
cd/syscall . . . . . . . 0x80/imm8 # int 80h
# close(stream)
# load stream
bb/copy . . . . . . . stream/imm32 # copy to EBX
8b/copy 0/mod/indirect 3/rm32/EBX 3/r32/EBX # copy *EBX to EBX
#
b8/copy . . . . . . . 6/imm32/close # copy 6 to EAX
cd/syscall . . . . . . . 0x80/imm8 # int 80h
# unlink(filename)
bb/copy . . . . . . . filename/imm32 # copy to EBX
b8/copy . . . . . . . 0xa/imm32/unlink # copy 10 to EAX
cd/syscall . . . . . . . 0x80/imm8 # int 80h
# exit(b)
# load b
bb/copy . . . . . . . b/imm32 # copy to EBX
8b/copy 0/mod/indirect 3/rm32/EBX 3/r32/EBX # copy *EBX to EBX
#
b8/copy . . . . . . . 1/imm32/exit # copy 1 to EAX
cd/syscall . . . . . . . 0x80/imm8 # int 80h
== data
stream:
00 00 00 00
a:
61 00 00 00
b:
00 00 00 00
filename:
2e 66 6f 6f 00 00 00 00
# vim:ft=subx:nowrap:tw&
|