noxonad/fasm-examples

Linux x86_64 examples to demonstrate useful concepts in fasm

Linux x86_64 FASM Examples

Some more advanced and practical examples to demonstrate certain concepts I came across by experimenting and tinkering with fasm for ttyper. It uses standard c library for function calling like malloc, free, time etc.

Feel free to study, modify and play with them to see how fasm works, as I found little to no documentation to more advanced concepts like allocating memory and getting time difference.

A simpler examples can be found here.

Building

In order to build all the examples you can run

$ make

or build just a certain one

$ make malloc
$ make time 

and then run each of the example:

$ ./malloc
Value: 10
Value: 5

$ ./time
The elapsed time is 2 seconds

$ ./numbers
Number A: 1691
Number B: 42
Sum: 1733
Diff: 1649
Mul: 71022.00
Div: 40.26190
Mod: 11

Clearing up

To clear the build files, simply run

$ make clean

Linux x86_64 Calling Conventions

According to this, the register order for the syscalls is as follows: rdi, rsi, rdx, r10, r8, r9, and the result is put into rax.

Calling conventions for function calling, according to this post is as follows: rdi, rsi, rdx, rcx, r8 and r9

Contribution

I'm far from being a fasm expert and if you want to point out some mistakes or provide more examples, you're free to do so. I hope that will help not only me, but also other fasm newcomers that want to go beyond writing a hello world program.

The code is distributed under the MIT licence so feel free to use it as an example database for your tutoring.