The Netwide Assembler (NASM)

I have a kind of off-topic NASM story. I think I was using it circa 2004 for a class, and was taking another class that required us to find 10 exploitable security holes in existing software. (This was DJB's "Unix Security Holes" class. Best class I ever took.) NASM was the first place I looked (my thought process was, it takes untrusted input and it's written in C), and indeed I found one: https://lists.debian.org/debian-security-announce/2005/msg00...

Incidentally, the other holes I found for that class were various XSS vulnerabilities in our course registration software. The administration was furious with me (I didn't exploit them, only proved that they existed), and banned me from using any computers at the University. DJB stuck up for me, though, and the vendor sent me a new iPod as a thank you. It was pretty stressful for a first-year student in 2004 though.

My parents really didn't want me being involved in any security-related fields, so I ended up not really touching it again. My take these days is that security is a subset of correctness; design for security, and make sure you implement it correctly, just like you do for any other feature. I also write a LOT of fuzz tests ;) But yeah, NASM was the beginning and end of my software security career, which I still find kind of amusing.

Nice to see NASM is still going strong. I used this for a class I taught back in the 90's. The class supported both Windows and Linux (but most students used Windows) and NASM supported both and was free.

I ended up creating my own free online textbook for the course. It's sorta out of date now since it was for 32-bit processors.

Wonder why Tatham is not an ACM fellow or something like it yet. Some very widely used code came from under his fingers.

One of my little pet projects is a Linux webserver written in NASM: https://github.com/jcalvinowens/asmhttpd

Why would anybody use this over the assembler shipped with their compiler?

This might make sense if your project is written entirely in assembly, but does anybody even do that nowadays? For projects that are mostly in C/C++ with bits of assembly here and there, it's yet one more dependency your users have to install.

We were taught NASM as part of a course and I'm so much accustomed to it's beautiful syntax.

Is it less capable than MASM? Don't have a reason to believe so because there's one to one correspondence between what you write and what's gets executed.

I wrote thousands lines of assembler for NASM. It was such a nice update to the good old turbo assembler back in the 90th.

Good memories. Thank you zsKnight, wherever you are.

I have been using NASM in my spare time recently because “learning” assembly is an itch I always had. I’m having so much fun. Cool to see it posted here.

I began learning computer programming with Logo [1], then BASIC, then C, Lisp, etc. However, somewhere along the way, growing dissatisfied with not knowing exactly what's going on under the hood, I began descending down the stack. That journey led me to learning about the CPU, using assemblers, as well as loading instructions in hexadecimal format into a memory by pushing buttons on a 8086 trainer kit. At one point, I also designed my own Mano Machine in VHDL which I then synthesised and tested on a Xilinx CPLD kit [2].

The last one was the most fun. It was very rewarding to see the abstract concepts presented in books come alive in the form of a working machine that could fetch, decode, and execute instructions from a memory. The memory was designed in VHDL too and implemented on the same Xilinx CPLD kit. Loading instructions into the memory required me to push DIP switches (one switch for each bit). A far cry from the comfort of Emacs running atop a modern operating system!

Those two adventures lied on opposite ends of a spectrum. There was the luxury of high level languages and tooling at one end. On the other end, there was the hands-on ritual of loading each bit of instruction, accomplished through the deliberate act of manipulating DIP switches. Such a laborious experience prompts a profound awareness that ultimately all software executes on physical matter.

Nestled in between these two extremes, there was a sweet spot involving assemblers. The first assembler I stumbled upon was the "A" command of DEBUG.EXE [2] of MS-DOS. The features were very minimalist and the tool was a bit more than an assembler. This humble debugger allowed me to peek into interrupt vector tables, inspect the content of ROM, learn how MS-DOS boots from scratch, etc. I later did come across GNU as, TASM, NASM, etc. which made me appreciate the number of bookkeeping problems a proper assembler solves. No more recalculating all the offsets for the jump and call instructions after every refactoring of the program!

These days, I work very high up in the stack where there are numerous layers of technology between what I type and what the physical machine executes. But I do fondly remember the days when armed with an assembler, some knowledge of the CPU and the computer architecture, we could plunge into the depths of the system, unravelling its intricacies to our heart's content.

[1] https://susam.net/blog/fd-100.html

[2] https://github.com/susam/mano-cpu

[3] https://susam.net/blog/programming-with-dos-debugger.html

TL;DR: I want to tinker with one assembler, which is better for tinkering, NASM or FASM?

I am looking to one day learn assembly (x86, x86-64 and potentially ARM) simply for tinkering hobby purposes, to prove I learned something watching all those Ben Eater TTL youtube videos and try my hand at logic design and creating toy programs that are as close to the metal as possible, just to say I can do it.

But part of the trick is not knowing where to start. There's MASM which appeals to me as a higher level language user in that you create those macros and use them in various places, and there's NASM and FASM which I like the idea of since they seem to be more portable to both Windows and Linux. I doubt I can write an assembly program and run it on an old android smartphone, so I'll leave that aside here.

This is why C is a high level language (and portable)