crap1.crap - crap0.asm written in crap

crap1.crap

#
# CRAP1 for Darwin-i386-MachO
# Copyright (C) 2013, Dan Glastonbury <[email protected]>
#
# Based on:
# HEX1 for Linux-i386-ELF
# Copyright (C) 2001, Edmund GRIMLEY EVANS <[email protected]>
#

# _mach_header:                 # struct mach_header
        ce fa ed fe             # magic
        07 00 00 00             # cputype (CPU_TYPE_X86_TYPE_X86)
        03 00 00 00             # cpusubtype (CPU_SUBTYPE_I386_ALL)
        02 00 00 00             # filetype (MH_EXECUTE)
        02 00 00 00             # ncmds
        cc 00 00 00             # sizeofcmds
        00 00 00 00             # flags

# +28
# Text Segment                  # struct segment_command
        01 00 00 00             # cmd (LC_SEGMENT)
        7c 00 00 00             # cmdsize = 124
        5f 5f 54 45 58 54 00 00 00 00 00 00 00 00 00 00 # segname[16] = '__TEXT'
        00 10 00 00             # vmaddr = 0x1000
        00 10 00 00             # vmsize = 0x1000
        00 00 00 00             # fileoff
        62 01 00 00             # filesize = 354
        07 00 00 00             # maxprot
        05 00 00 00             # initprot
        01 00 00 00             # nsects
        00 00 00 00             # flags
# +56
# Text section                  # struct section
        5f 5f 74 65 78 74 00 00 00 00 00 00 00 00 00 00 # sectname[16] = '__text'
        5f 5f 54 45 58 54 00 00 00 00 00 00 00 00 00 00 # segname[16]  = '__TEXT'
        e8 10 00 00             # addr = 0x10E8
        7a 00 00 00             # size = 0x7A
        e8 00 00 00             # offset = 0xE8
        02 00 00 00             # align
        00 00 00 00             # reloff
        00 00 00 00             # nreloc
        00 00 00 00             # flags
        00 00 00 00             # reserved1
        00 00 00 00             # reserved2
# +68
#                               # struct thread_command
        05 00 00 00             # cmd (LC_UNIXTHREAD)
        50 00 00 00             # cmdsize = 80
        01 00 00 00             # flavor = i386_THREAD_STATE
        10 00 00 00             # count
# state:    dd 0, 0, 0, 0, 0, 0, 0, 0
#           dd 0, 0, _start, 0, 0, 0, 0, 0
        00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 # 0, 0, 0, 0
        00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 # 0, 0, 0, 0
        00 00 00 00 00 00 00 00 49 11 00 00 00 00 00 00 # 0, 0, _start, 0
        00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 # 0, 0, 0, 0
# +80 =204

# Enter here:

# = 0xe8
# _syscall:
        cd 80                   # int     80h
        c3                      # ret

# _exit:
        31 c0                   # xor     eax, eax
        50                      # push    eax
        b0 01                   # mov     al, sys_exit
        e8 f3 ff ff ff          # call    _syscall

# _getchar:                     # read a byte from stdin
        31 c0                   # xor     eax, eax
        50                      # push    eax
        89 e1                   # mov     ecx, esp
        6a 01                   # push    1             ; read 1 byte
        51                      # push    ecx           ; into [ecx]
        6a 00                   # push    0             ; from stdin
        b0 03                   # mov     al, sys_read
        e8 e2 ff ff ff          # call    _syscall
        85 c0                   # test    eax, eax
        74 e1                   # je      _exit
        83 c4 0c                # add     esp, 12
        58                      # pop     eax           ; result in eax
        c3                      # ret

# _putchar:                     # write a byte to stdout
        8d 4c 24 04             # lea     ecx, [esp+4]
        31 c0                   # xor     eax, eax
        6a 01                   # push    1             ; write 1 byte
        51                      # push    ecx           ; from [ecx]
        6a 01                   # push    1             ; to stdout
        b0 04                   # mov     al, sys_write
        e8 c7 ff ff ff          # call    _syscall
        83 c4 0c                # add     esp, 12
        c3                      # ret

# _gethex:
        e8 cb ff ff ff          # call    _getchar
        83 f8 23                # cmp     eax, '#'
        75 0c                   # jne     .l1

# .loop:
        e8 c1 ff ff ff          # call    _getchar
        83 f8 0a                # cmp     eax, '\n'
        75 f6                   # jne     .loop
        eb ea                   # jmp     _gethex

# .l1:
        83 e8 30                # sub     eax, '0'
        7c e5                   # jl      _gethex
        83 f8 30                # cmp     eax, '0'
        7c 03                   # jl      .ret
        83 e8 27                # sub     eax, 39

# .ret:
        c3                      # ret

# _start:
        e8 d7 ff ff ff          # call    _gethex
        c1 e0 04                # sal     eax, 4
        50                      # push    eax
        e8 ce ff ff ff          # call    _gethex
        01 04 24                # add     [esp], eax
        e8 b0 ff ff ff          # call    _putchar
        58                      # pop     eax
        eb e7                   # jmp     _start