blob: 1f146a5dbbf246431adf4ef71d1facbb08a9b14c (
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
|
# _write: write to a file descriptor (fd)
== 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:
# syscall(exit, 0) -- can't test _write just yet
bb/copy-to-EBX 0/imm32
b8/copy-to-EAX 1/imm32/exit
cd/syscall 0x80/imm8
_write: # fd : int, s : (address array byte) -> <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
51/push-ECX
52/push-EDX
53/push-EBX
# syscall(write, fd, (data) s+4, (size) *s)
# . fd : EBX
8b/copy 1/mod/*+disp8 4/rm32/sib 5/base/EBP 4/index/none . 3/r32/EBX 8/disp8 . # copy *(EBP+8) to EBX
# . data : ECX = s+4
8b/copy 1/mod/*+disp8 4/rm32/sib 5/base/EBP 4/index/none . 1/r32/ECX 0xc/disp8 . # copy *(EBP+12) to ECX
81 0/subop/add 3/mod/direct 1/rm32/ECX . . . . . 4/imm32 # add to ECX
# . size : EDX = *s
8b/copy 1/mod/*+disp8 4/rm32/sib 5/base/EBP 4/index/none . 2/r32/EDX 0xc/disp8 . # copy *(EBP+12) to EDX
8b/copy 0/mod/indirect 2/rm32/EDX . . . 2/r32/EDX . . # copy *EDX to EDX
# . syscall
b8/copy-to-EAX 4/imm32/write
cd/syscall 0x80/imm8
$_write:end:
# . restore registers
5b/pop-to-EBX
5a/pop-to-EDX
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
# . . vim:nowrap:textwidth=0
|