1 # Repeatedly read 32-bit numbers from /dev/random, print them to stdout.
 2 #
 3 # To run:
 4 #   $ ./translate_subx [01]*.subx apps/random.subx
 5 #   $ ./a.elf
 6 
 7 == code 0x09000000
 8 #   instruction                     effective address                                                   register    displacement    immediate
 9 # . op          subop               mod             rm32          base        index         scale       r32
10 # . 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
11 
12 Entry:
13     # stream/esi = syscall_open("/dev/null", O_RDONLY, 0)  # we can't use 'fd' because it looks like a hex byte
14     bb/copy-to-ebx  Filename/imm32
15     b9/copy-to-ecx  0/imm32/rdonly
16     ba/copy-to-edx  0x180/imm32/fixed-perms
17     e8/call  syscall_open/disp32
18     # . stream = eax
19     89/copy                         3/mod/direct    6/rm32/esi    .           .             .           0/r32/eax   .               .                 # copy eax to esi
20 
21 $loop:
22 
23     # syscall_read(Stream, N, 4)
24     89/copy                         3/mod/direct    3/rm32/ebx    .           .             .           6/r32/esi   .               .                 # copy esi to ebx
25     b9/copy-to-ecx  N/imm32
26     ba/copy-to-edx  4/imm32/size
27     e8/call  syscall_read/disp32
28 
29     # write-int32-hex-buffered(Stdout, *N)
30     # . . push args
31     ff          6/subop/push        0/mod/indirect  5/rm32/.disp32            .             .           .           N/disp32                          # push *N
32     68/push  Stdout/imm32
33     # . . call
34     e8/call  write-int32-hex-buffered/disp32
35 
36     # write-buffered(Stdout, Newline)
37     # . . push args
38     68/push  Newline/imm32
39     68/push  Stdout/imm32
40     # . . call
41     e8/call  write-buffered/disp32
42     # . . discard args
43     81          0/subop/add         3/mod/direct    4/rm32/esp    .           .             .           .           .               8/imm32           # add to esp
44 
45     eb/jump  $loop/disp8
46 
47     # syscall_exit(0)
48     bb/copy-to-ebx  0/imm32
49     e8/call  syscall_exit/disp32
50 
51 == data 0x0a000000
52 
53 N:
54     0/imm32
55 Filename:
56     2f 64 65 76 2f 72 61 6e 64 6f 6d 00
57 #   /  d  e  v  /  r  a  n  d  o  m  null
58 
59 # . . vim:nowrap:textwidth=0