NASM help

So I wanted to dive into Linux Nasm. I am running a 64 bit system. From the google results I found, all the tutorials i see on Linux Nasm are 32bit. All of the 64bit Linux tutorials use AT&T syntax. Which I DO NOT want to use! Can I use Nasm on a 64bit Linux machine? I mean I installed it through the terminal but I assume that's for use with 32bit. Anyone know a little something? Perhaps a tutorial/PDF if Nasm on a 64bit system is possible?

Thanks.

EDIT: I went to a NASM forum and am seeking help there. If someone is still willing to post and help I'd appreciate it.

Did you read the NASM manual? It does mention NASM style assembly.

Jim

Yes i have Jim. The trouble is, its not sitting well with me. I find it far from beginner friendly! I look at it and can't help but feel overwhelmed!

I actually have decided to download myself a copy of Ubuntu 10.10. The 32 bit version and install that in replace of my 64 bit version of Ubuntu. Coding in 64 bit ASM will be so much harder for a beginner like myself than it's 32 bit counterpart.

Thanks Jim.

Looking for beginner friendly tutorials/PDF's/suggestions. So if anyone has any, please feel free to reply. Thanks.

I don't see your boggle. If you think you're going to have trouble learning 64 bit assembly, create a 32-bit virtual machine and start with 32 bit assembly instead.

But don't try 16 bit assembly - I still have nightmares. Segment, offset, segment, offset... (starts shaking violently) :(

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Originally Posted by SMurf

I don't see your boggle. If you think you're going to have trouble learning 64 bit assembly, create a 32-bit virtual machine and start with 32 bit assembly instead.

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This might help.

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Originally Posted by Annonymous

I actually have decided to download myself a copy of Ubuntu 10.10. The 32 bit version and install that in replace of my 64 bit version of Ubuntu. Coding in 64 bit ASM will be so much harder for a beginner like myself than it's 32 bit counterpart.

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Yeeeees but I feel you're missing something obvious here.
Tell me - can you run 32-bit user mode programs in a 64-bit OS?

yeah sure. Not vice versa tho.

If your going to suggest that i

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create a 32-bit virtual machine and start with 32 bit assembly instead.

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Instead of re-format and install a fresh copy of Ubuntu; I would like you to know that this is the way i prefer to do things. Sometimes i prefer the latter<shrugs shoulders>.

If that is not what you intended on saying...Then i spoke to soon lol

Right, so there's nothing stopping you from writing 32-bit assembly on your current 64-bit OS.

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Originally Posted by SMurf

Right, so there's nothing stopping you from writing 32-bit assembly on your current 64-bit OS.

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No there is not. This is what i can not figure out how to do. So that is why i said i am just going to switch to a 32 bit version of Ubuntu. Unless you can school me on how i go about doing the suggest.

I know reformatting and installing a fresh copy of Ubuntu may seem crazy just to program in 32 bit mode. I actually have nothing on my computer. Its all on my usb. The only reason i use my laptop is to watch a movie or program anyway. So i wont lose any data. Its just the hassle of re installing i would be dealing with.

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Originally Posted by SMurf

Yeeeees but I feel you're missing something obvious here.
Tell me - can you run 32-bit user mode programs in a 64-bit OS?

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The *CPU* supports it. Whether you can actually do it is up to the OS. On Windows, it works transparently. On Linux you have to do all kinds of awful crap to make it work and even then it's flaky.

Wow all i had to do was add 2 numbers to the compile process to make it work lol I cant believe it was that easy.

So it wouldnt work when i try:

Code:

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root@ubuntu:/home/ubuntu/Documents# nasm -f elf pause.asm
root@ubuntu:/home/ubuntu/Documents# ld pause.o -o pause

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which produces this error:

Code:

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ld: i386 architecture of input file `pause.o' is incompatible with i386:x86-64 output

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That is actually for 32 bit mode. Now all you have to do for 64 bit mode is add th number 64 after the word elf.

Code:

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nasm -f elf64 pause.asm

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"AND IT WORKS"

Read up on the BITS directive for NASM - NASM Manual

Then, you need to tell "ld" that you want 32 bit. I think this was the "-m32" flag that does this.

I cant check as I burned the power unit out my 64 bit laptop last week and the postman still hasn't delivered my new one

It shouldn't be too hard -- you don't need to link to any libraries, right? 64-bit linux kernels generally have 32-bit support built into them because grub requires it.

Yeah all I needed to do was add 2 numbers to the compile process MK27.

I was using
nasm -f elf pause.asm When creating the object file.

But needed to use
nasm -f elf64 pause.asm

Only a slight difference, but it is whats needed for the 64 bit Code to run. It surprisingly had nothing to do with the linker Fordy. It was the incompatable 32 bit obj file I was creating. Thanks yall

Hmm, but then aren't you creating a 64-bit executable? I dunno if that matters, but try it without the "64" using the ld flag Fordy recommends and see what happens.

Actually I think that flag should be "-m elf_i386" but if you put -m in there and it doesn't recognized the arg it will say:

root~»ld -m satan
ld: unrecognised emulation mode: satan
Supported emulations: elf_x86_64 elf_i386 i386linux elf_l1om

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Originally Posted by MK27

Hmm, but then aren't you creating a 64-bit executable? I dunno if that matters, but try it without the "64" using the ld flag Fordy recommends and see what happens.

Actually I think that flag should be "-m elf_i386" but if you put -m in there and it doesn't recognized the arg it will say:

root~»ld -m satan
ld: unrecognised emulation mode: satan
Supported emulations: elf_x86_64 elf_i386 i386linux elf_l1om

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That's what you get when you try to remember compiler flags from memory!

Either way, you should be able to assemble 32 or 64 bit code with nasm and "ld" is such an impressive linker that you can link together more than you can ever need if you refer to the docs

As for the AT&T syntax conundrum there are ways to get NASM to use Intel syntax. I know I did it way back when so perhaps Googling it will give you some answers. I know it is possible but I do not remember what I did.