Re: assembler [was: Re: cheers for gogo]

[Al Hudson <nospam [at] york.ac.uk>]

On Tue, 14 Mar 2000, Dr A V Le Blanc wrote:

> By the way, has anyone seen ELFkickers?  It produces the following
> tiny binaries:
> 
>      -rwx--x--x   1    128 Mar 14 09:54 cat
>      -rwx--x--x   1   1000 Mar 14 09:54 factor
>      -rwx--x--x   1     59 Mar 14 09:54 hello
>      -rwx--x--x   1    192 Mar 14 09:54 hexdump
>      -rwx--x--x   1     45 Mar 14 09:54 true
> 
> These are in fact written in assembler and assembled using nasm.
> The best I can do with a 'normal' assembler program for
> hello world is 448 bytes...

ELF is notorious for having large gaping holes in it which you can stuff
with code. There are a number of pointers to fields in there, and you can
munge some of the fields such that they contain subsets of each other,
thus you can overlap them and do all sorts of crazy things. 

Cheers,

Alex.


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