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flat assembler > Unix > Mach-O objects made with fasmg

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Tomasz Grysztar
Assembly Artist


Joined: 16 Jun 2003
Posts: 6632
Location: Kraków, Poland
Mach-O objects made with fasmg
After I got the Mach-O executables more or less working the next step is to extend the macros so that they can build linkable objects as well.

I have prepared the macros to create symbol tables and relocations - you may notice that they are a relatively simple addition on top of the basic layers I created earlier for the executable output. I managed to assemble and then successfully link (with LD) the following 32-bit example consisting of two objects:

Code:
include '80386.inc'
use32

MachO.Settings.FileType equ MH_OBJECT
include 'macho.inc'

public start
extrn writemsg

SYS_exit = 1

section '__TEXT':'__text'

  start:

        mov     esi,msg
        call    writemsg

        push    1
        mov     eax,SYS_exit
        sub     esp,4
        int     0x80

section '__TEXT':'__cstring'

  msg db "Relocated and ready!",0xA,0


Code:

include '80386.inc'
use32

MachO.Settings.FileType equ MH_OBJECT
include 'macho.inc'

public writemsg

SYS_write = 4

section '__TEXT':'__text'

  writemsg:
        mov     edi,esi
        mov     ecx,-1
        xor     al,al
        repne   scasb
        neg     ecx
        sub     ecx,2
        push    ecx
        push    esi
        push    1
        mov     eax,SYS_write
        sub     esp,4
        int     0x80
        add     esp,4*4
        ret



Note that when Mach-O is used as an object, all sections should reside in a single unnamed segment, but each section in addition to its own name needs to specify the name of a segment it is intended for. Thus the unusual syntax in the above samples.

PS. I have not created any 64-bit objects yet. There are going to be some differences in relocations and perhaps some other things to adjust to make them work.


Description: Mach-O formatting macros with example objects
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Filename: machO.zip
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Post 27 Aug 2017, 22:11
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Tomasz Grysztar
Assembly Artist


Joined: 16 Jun 2003
Posts: 6632
Location: Kraków, Poland
With a small tweak in the relocation generating macro I was able to get 64-bit objects to work, too. The sources are like:

Code:
include 'x64.inc'
use64

MachO.Settings.FileType equ MH_OBJECT
MachO.Settings.ProcessorType equ CPU_TYPE_X86_64
MachO.Settings.ProcessorSubtype equ CPU_SUBTYPE_X86_64_ALL
include 'macho.inc'

section '__TEXT':'__text'

public start
extrn writemsg
extrn exit

start:
        lea     rsi,[msg]
        call    writemsg
        call    exit

section '__DATA':'__data'

        msg db 'Relocated and ready!',0Ah,0


Code:
include 'x64.inc'
use64

MachO.Settings.FileType equ MH_OBJECT
MachO.Settings.ProcessorType equ CPU_TYPE_X86_64
MachO.Settings.ProcessorSubtype equ CPU_SUBTYPE_X86_64_ALL
include 'macho.inc'

section '__TEXT':'__text'

public writemsg
public exit

        SYSCALL_CLASS_UNIX = 2
        SYSCALL_CLASS_SHIFT = 24
        define SYSCALL_CONSTRUCT_UNIX SYSCALL_CLASS_UNIX shl SYSCALL_CLASS_SHIFT +

        SYS_exit = 1
        SYS_write = 4

writemsg:
        mov     rdi,rsi
        or      rcx,-1
        xor     al,al
        repne   scasb
        neg     rcx
        sub     rcx,2
        mov     rdx,rcx
        mov     rdi,1
        mov     rax,SYSCALL_CONSTRUCT_UNIX(SYS_write)
        syscall
        retn

exit:
        mov     rdi,rax
        mov     rax,SYSCALL_CONSTRUCT_UNIX(SYS_exit)
        syscall

Post 28 Aug 2017, 17:07
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Tomasz Grysztar
Assembly Artist


Joined: 16 Jun 2003
Posts: 6632
Location: Kraków, Poland
As an additional test of the macros I have assembled the MacOS version of fasmg as a linkable object and it appears to be working correctly. In the current packaging "source/macos/fasmg.asm" assembles directly to executable, to get an object instead it needs to be replaced with the following:

Code:
match ,{

        err ; fasm 1 assembly not supported

match -,{
else

        include 'selfhost.inc'

end match
_ equ }

format MachO
public main as '_main'

include '../version.inc'

extrn '_malloc' as libc.malloc
extrn '_realloc' as libc.realloc
extrn '_free' as libc.free
extrn '_fopen' as libc.fopen
extrn '_fclose' as libc.fclose
extrn '_fread' as libc.fread
extrn '_fwrite' as libc.fwrite
extrn '_fseek' as libc.fseek
extrn '_ftell' as libc.ftell
extrn '_time' as libc.time
extrn '_write' as libc.write

extrn '_getenv' as getenv
extrn '_gettimeofday' as gettimeofday
extrn '_exit' as exit

struct timeval
        time_t dd ?
        suseconds_t dd ?
ends

section '__TEXT':'__text' align 16

  main:
        mov     ecx,[esp+4]
        mov     [argc],ecx
        mov     ebx,[esp+8]
        mov     [argv],ebx

        call    system_init

        mov     esi,_logo
        xor     ecx,ecx
        call    display_string

        call    get_arguments
        jc      display_usage_information

        xor     al,al
        mov     ecx,[verbosity_level]
        jecxz   init
        or      al,TRACE_ERROR_STACK
        dec     ecx
        jz      init
        or      al,TRACE_DISPLAY
  init:
        call    assembly_init

        ccall   gettimeofday,start_time,0

  assemble:
        mov     esi,[initial_commands]
        mov     edx,[source_path]
        call    assembly_pass
        jc      assembly_done

        mov     eax,[current_pass]
        cmp     eax,[maximum_number_of_passes]
        jb      assemble

        call    show_display_data

        mov     ebx,_code_cannot_be_generated
        jmp     fatal_error

  assembly_done:

        call    show_display_data

        cmp     [first_error],0
        jne     assembly_failed

        mov     eax,[current_pass]
        mov     edi,string_buffer
        call    itoa
        call    display_string
        mov     esi,_passes
        cmp     [current_pass],1
        jne     display_passes_suffix
        mov     esi,_pass
      display_passes_suffix:
        xor     ecx,ecx
        call    display_string
        ccall   gettimeofday,end_time,0
        mov     eax,[end_time.time_t]
        sub     eax,[start_time.time_t]
        mov     ecx,1000000
        mul     ecx
        add     eax,[end_time.suseconds_t]
        adc     edx,0
        sub     eax,[start_time.suseconds_t]
        sbb     edx,0
        add     eax,50000
        mov     ecx,1000000
        div     ecx
        mov     ebx,eax
        mov     eax,edx
        xor     edx,edx
        mov     ecx,100000
        div     ecx
        mov     [tenths_of_second],eax
        xchg    eax,ebx
        or      ebx,eax
        jz      display_output_length
        mov     edi,string_buffer
        call    itoa
        call    display_string
        mov     esi,_message_suffix
        mov     ecx,1
        call    display_string
        mov     eax,[tenths_of_second]
        mov     edi,string_buffer
        call    itoa
        call    display_string
        mov     esi,_seconds
        xor     ecx,ecx
        call    display_string
      display_output_length:
        call    get_output_length
        push    eax
        mov     edi,string_buffer
        call    itoa
        call    display_string
        pop     eax
        mov     esi,_bytes
        cmp     eax,1
        jne     display_bytes_suffix
        mov     esi,_byte
      display_bytes_suffix:
        xor     ecx,ecx
        call    display_string
        mov     esi,_new_line
        xor     ecx,ecx
        call    display_string

        mov     edi,[output_path]
        call    write_output_file
        jc      write_failed

        call    assembly_shutdown
        call    system_shutdown

        ccall   exit,0

  assembly_failed:

        call    show_errors

        call    assembly_shutdown
        call    system_shutdown

        ccall   exit,2

  write_failed:
        mov     ebx,_write_failed
        jmp     fatal_error

  out_of_memory:
        mov     ebx,_out_of_memory
        jmp     fatal_error

  fatal_error:

        mov     esi,_error_prefix
        xor     ecx,ecx
        call    display_error_string
        mov     esi,ebx
        xor     ecx,ecx
        call    display_error_string
        mov     esi,_message_suffix
        xor     ecx,ecx
        call    display_error_string

        call    assembly_shutdown
        call    system_shutdown

        ccall   exit,3

  display_usage_information:

        mov     esi,_usage
        xor     ecx,ecx
        call    display_string

        call    system_shutdown

        ccall   exit,1

  get_arguments:
        xor     eax,eax
        mov     [initial_commands],eax
        mov     [source_path],eax
        mov     [output_path],eax
        mov     [maximum_number_of_passes],100
        mov     [maximum_number_of_errors],1
        mov     [maximum_depth_of_stack],10000
        mov     ecx,[argc]
        mov     ebx,[argv]
        add     ebx,4
        dec     ecx
        jz      error_in_arguments
    get_argument:
        mov     esi,[ebx]
        mov     al,[esi]
        cmp     al,'-'
        je      get_option
        cmp     [source_path],0
        jne     get_output_file
        mov     [source_path],esi
        jmp     next_argument
    get_output_file:
        cmp     [output_path],0
        jne     error_in_arguments
        mov     [output_path],esi
        jmp     next_argument
    get_option:
        inc     esi
        lodsb
        cmp     al,'e'
        je      set_errors_limit
        cmp     al,'E'
        je      set_errors_limit
        cmp     al,'i'
        je      insert_initial_command
        cmp     al,'I'
        je      insert_initial_command
        cmp     al,'p'
        je      set_passes_limit
        cmp     al,'P'
        je      set_passes_limit
        cmp     al,'r'
        je      set_recursion_limit
        cmp     al,'R'
        je      set_recursion_limit
        cmp     al,'v'
        je      set_verbose_mode
        cmp     al,'V'
        je      set_verbose_mode
    error_in_arguments:
        stc
        ret
    set_verbose_mode:
        cmp     byte [esi],0
        jne     get_verbose_setting
        dec     ecx
        jz      error_in_arguments
        add     ebx,4
        mov     esi,[ebx]
      get_verbose_setting:
        call    get_option_value
        cmp     edx,2
        ja      error_in_arguments
        mov     [verbosity_level],edx
        jmp     next_argument
    set_errors_limit:
        cmp     byte [esi],0
        jne     get_errors_setting
        dec     ecx
        jz      error_in_arguments
        add     ebx,4
        mov     esi,[ebx]
      get_errors_setting:
        call    get_option_value
        test    edx,edx
        jz      error_in_arguments
        mov     [maximum_number_of_errors],edx
        jmp     next_argument
    set_recursion_limit:
        cmp     byte [esi],0
        jne     get_recursion_setting
        dec     ecx
        jz      error_in_arguments
        add     ebx,4
        mov     esi,[ebx]
      get_recursion_setting:
        call    get_option_value
        test    edx,edx
        jz      error_in_arguments
        mov     [maximum_depth_of_stack],edx
        jmp     next_argument
    set_passes_limit:
        cmp     byte [esi],0
        jne     get_passes_setting
        dec     ecx
        jz      error_in_arguments
        add     ebx,4
        mov     esi,[ebx]
      get_passes_setting:
        call    get_option_value
        test    edx,edx
        jz      error_in_arguments
        mov     [maximum_number_of_passes],edx
    next_argument:
        add     ebx,4
        dec     ecx
        jnz     get_argument
        cmp     [source_path],0
        je      error_in_arguments
        cmp     [output_path],0
        je      error_in_arguments
        clc
        ret
    get_option_value:
        xor     eax,eax
        mov     edx,eax
      find_option_value:
        cmp     byte [esi],20h
        jne     get_option_digit
        inc     esi
        jmp     find_option_value
      get_option_digit:
        lodsb
        test    al,al
        jz      option_value_ok
        sub     al,30h
        jc      invalid_option_value
        cmp     al,9
        ja      invalid_option_value
        imul    edx,10
        jo      invalid_option_value
        add     edx,eax
        jc      invalid_option_value
        jmp     get_option_digit
      option_value_ok:
        dec     esi
        clc
        ret
      invalid_option_value:
        stc
        ret
    insert_initial_command:
        cmp     byte [esi],0
        jne     measure_initial_command
        dec     ecx
        jz      error_in_arguments
        add     ebx,4
        mov     esi,[ebx]
      measure_initial_command:
        push    ebx ecx edi
        mov     edi,esi
        or      ecx,-1
        xor     al,al
        repne   scasb
        not     ecx
        dec     ecx
        mov     edi,[initial_commands]
        lea     eax,[ecx+2]
        test    edi,edi
        jz      allocate_initial_commands_buffer
        mov     edx,[initial_commands_length]
        add     edi,edx
        add     eax,edx
        cmp     eax,[initial_commands_maximum_length]
        ja      grow_initial_commands_buffer
      copy_initial_command:
        rep     movsb
        mov     ax,0Ah
        stosw
        dec     edi
        sub     edi,[initial_commands]
        mov     [initial_commands_length],edi
        pop     edi ecx ebx
        jmp     next_argument
      allocate_initial_commands_buffer:
        push    ecx
        mov     ecx,eax
        call    malloc
        jc      out_of_memory
        mov     [initial_commands],eax
        mov     [initial_commands_maximum_length],ecx
        mov     edi,eax
        pop     ecx
        jmp     copy_initial_command
      grow_initial_commands_buffer:
        push    ecx
        mov     ecx,eax
        mov     eax,[initial_commands]
        call    realloc
        jc      out_of_memory
        mov     [initial_commands],eax
        mov     [initial_commands_maximum_length],ecx
        mov     edi,eax
        add     edi,[initial_commands_length]
        pop     ecx
        jmp     copy_initial_command

  include 'system.inc'

  include '../assembler.inc'
  include '../symbols.inc'
  include '../expressions.inc'
  include '../conditions.inc'
  include '../directives.inc'
  include '../floats.inc'
  include '../errors.inc'
  include '../map.inc'
  include '../reader.inc'
  include '../output.inc'
  include '../console.inc'

section '__TEXT':'__cstring' align 4

  _logo db 'flat assembler  version g.',VERSION,10,0

  _usage db 'Usage: fasmg source output',10
         db 'Optional settings:',10
         db '    -p limit    Set the maximum allowed number of passes (default 100)',10
         db '    -e limit    Set the maximum number of displayed errors (default 1)',10
         db '    -r limit    Set the maximum depth of stack (default 10000)',10
         db '    -v flag     Enable or disable showing all lines from the stack (default 0)',10
         db '    -i command  Insert instruction at the beginning of source',13,10
         db 0

  _pass db ' pass, ',0
  _passes db ' passes, ',0
  _dot db '.'
  _seconds db ' seconds, ',0
  _byte db ' byte.',0
  _bytes db ' bytes.',0

  _write_failed db 'failed to write the output file',0
  _out_of_memory db 'not enough memory to complete the assembly',0
  _code_cannot_be_generated db 'could not generate code within the allowed number of passes',0

  _open_mode db 'r',0
  _create_mode db 'w',0

  include '../tables.inc'
  include '../messages.inc'

section '__DATA':'__data' align 4

  include '../variables.inc'

  source_path dd ?
  output_path dd ?
  maximum_number_of_passes dd ?

  initial_commands dd ?
  initial_commands_length dd ?
  initial_commands_maximum_length dd ?

  argc dd ?
  argv dd ?
  timestamp dq ?

  start_time timeval
  end_time timeval
  tenths_of_second dd ?

  verbosity_level dd ?
  string_buffer rb 100h

  path_buffer rb 1000h

Post 01 Sep 2017, 20:47
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