x86 Assembly on a Mac

Question

Does anyone know of any good tools  I m looking for IDEs  to write assembly on the Mac  Xcode is a little cumbersome to me   Also  on the Intel Macs  can I use generic x86 asm   Or is there a modified instruction set  Any information about post Intel   Also  I know that on windows  asm can run in an emulated environment created by the OS to let the code think it s running on its own dedicated machine  Does OS X provide the same thing

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Also  on the Intel Macs  can I use generic x86 asm  or is there a modified instruction set  Any information about post Intel Mac assembly helps    It s the same instruction set  it s the same chips

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Forget about finding a IDE to write run compile assembler on Mac  But  remember mac is UNIX  See http   asm sourceforge net articles linasm html  A decent guide  though short  to running assembler via GCC on Linux  You can mimic this  Macs use Intel chips so you want to look at Intel syntax

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After installing any version of Xcode targeting Intel-based Macs  you should be able to write assembly code   Xcode is a suite of tools  only one of which is the IDE  so you don t have to use it if you don t want to    That said  if there are specific things you find clunky  please file a bug at Apple s bug reporter - every bug goes to engineering    Furthermore  installing Xcode will install both the Netwide Assembler  NASM  and the GNU Assembler  GAS   that will let you use whatever assembly syntax you re most comfortable with   You ll also want to take a look at the Compiler  amp  Debugging Guides  because those document the calling conventions used for the various architectures that Mac OS X runs on  as well as how the binary format and the loader work   The IA-32  x86-32  calling conventions in particular may be slightly different from what you re used to   Another thing to keep in mind is that the system call interface on Mac OS X is different from what you might be used to on DOS Windows  Linux  or the other BSD flavors   System calls aren t considered a stable API on Mac OS X  instead  you always go through libSystem   That will ensure you re writing code that s portable from one release of the OS to the next   Finally  keep in mind that Mac OS X runs across a pretty wide array of hardware - everything from the 32-bit Core Single through the high-end quad-core Xeon   By coding in assembly you might not be optimizing as much as you think  what s optimal on one machine may be pessimal on another   Apple regularly measures its compilers and tunes their output with the  -Os  optimization flag to be decent across its line  and there are extensive vector matrix-processing libraries that you can use to get high performance with hand-tuned CPU-specific implementations   Going to assembly for fun is great   Going to assembly for speed is not for the faint of heart these days

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As stated before  don t use syscall  You can use standard C library calls though  but be aware that the stack MUST be 16 byte aligned per Apple s IA32 function call ABI   If you don t align the stack  your program will crash in   dyld misaligned stack error when you make a call into any of the libraries or frameworks   The following snippet assembles and runs on my system     File  hello asm   Build  nasm -f macho hello asm  amp  amp  gcc -o hello hello o  SECTION  rodata hello msg db  Hello  World   0x0a 0x00  SECTION  text  extern  printf   could also use  puts    GLOBAL  main    aligns esp to 16 bytes in preparation for calling a C library function   arg is number of bytes to pad for function arguments  this should be a multiple of 16   unless you are using push pop to load args  macro clib prolog 1     mov ebx  esp          remember current esp     and esp  0xFFFFFFF0   align to next 16 byte boundary  could be zero offset       sub esp  12           skip ahead 12 so we can store original esp     push ebx              store esp  16 bytes aligned again      sub esp   1           pad for arguments  make conditional    endmacro    arg must match most recent call to clib prolog  macro clib epilog 1     add esp   1           remove arg padding     pop ebx               get original esp     mov esp  ebx          restore  endmacro   main        set up stack frame     push ebp     mov ebp  esp     push ebx      clib prolog 16     mov dword  esp   hello msg     call  printf       can make more clib calls here        clib epilog 16        tear down stack frame     pop ebx     mov esp  ebp     pop ebp     mov eax  0            set return code     ret

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Recently I wanted to learn how to compile Intel x86 on Mac OS X  For nasm  -o hello tmp - outfile -f macho - specify format Linux - elf or elf64 Mac OSX - macho  For ld  -arch i386 - specify architecture  32 bit assembly  -macosx version min 10 6  Mac OSX - complains about default specification  -no pie  Mac OSX - removes ld warning  -e main - specify main symbol name  Mac OSX - default is start  -o hello o - outfile  For Shell    hello o - execution  One-liner  nasm -o hello tmp -f macho hello s  amp  amp  ld -arch i386 -macosx version min 10 6 -no pie -e  main -o hello o hello tmp  amp  amp    hello o  Let me know if this helps  I wrote how to do it on my blog here  http   blog burrowsapps com 2013 07 how-to-compile-helloworld-in-intel-x86 html For a more verbose explanation  I explained on my Github here  https   github com jaredsburrows Assembly

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Running assembly Code on Mac is just 3 steps away from you  It could be done using XCODE but better is to use NASM Command Line Tool  For My Ease I have already installed Xcode  if you have Xcode installed its good   But You can do it without XCode as well   Just Follow    First Install NASM using Homebrew brew install nasm convert  asm file into Obj File using this command nasm -f macho64 myFile asm Run Obj File to see OutPut using command ld -macosx version min 10 7 0 -lSystem -o OutPutFile myFile o  amp  amp    64   Simple Text File named myFile asm is written below for your convenience   global start section  text  start      mov     rax  0x2000004   write     mov     rdi  1   stdout     mov     rsi  msg     mov     rdx  msg len     syscall      mov     rax  0x2000001   exit     mov     rdi  0     syscall  section  data  msg     db       Assalam O Alaikum Dear   10  len    equ       - msg

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The features available to use are dependent on your processor  Apple uses the same Intel stuff as everybody else  So yes  generic x86 should be fine  assuming you re not  on a PPC  D    As far as tools go  I think your best bet is a good text editor that  understands  assembly

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For a nice step-by-step x86 Mac-specific introduction see http   peter michaux ca articles assembly-hello-world-for-os-x   The other links I   ve tried have some non-Mac pitfalls

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Don t forget that unlike Windows  all Unix based system need to have the source before destination unlike Windows  On Windows its   mov  source    destination  but on the Mac its the other way around

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