blob: eb66f1bf3022e8389ed9c411490b782a34162857 (
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
|
## add the first 10 numbers, and return the result in the exit code
#
# To run:
# $ subx translate ex3.subx ex3
# $ subx run ex3
# Expected result:
# $ echo $?
# 55
== 0x08048054 # code segment, after leaving room for ELF header
# 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
# result: EBX = 0
bb/copy 0/imm32 # copy 0 to EBX
# counter: ECX = 1
b9/copy 1/imm32 # copy 1 to ECX
loop:
# while (counter <= 10)
81 7/subop/compare 3/mod/direct 1/rm32/ecx 0xa/imm32 # compare ECX, 10/imm
7f/jump-if exit/disp8 # jump-if-greater exit
# result += counter
01/add 3/mod/direct 3/rm32/ebx 1/r32/ecx # add ECX to EBX
# ++counter
81 0/subop/add 3/mod/direct 1/rm32/ecx 1/imm32 # add 1 to ECX
# loop
eb/jump loop/disp8 # jump loop
exit:
# exit(EBX)
b8/copy 1/imm32 # copy 1 to EAX
cd/syscall 0x80/imm8 # int 80h
# vim:ft=subx:nowrap
|