Creating Teensy ELF Executables for Linux (Or, "Size Is Everything") (1999)
muppetlabs.comPart 2: https://www.muppetlabs.com/~breadbox/software/tiny/revisit.h...
Discussed here a couple months ago: https://news.ycombinator.com/item?id=48654411
Part 3: https://www.muppetlabs.com/~breadbox/software/tiny/somewhat....
This is actually a lot of fun. Never did it on Linux, but Windows PE EXE files make similar tricks possible. Windows 95 in particular was very permissive. Using a (very primitive, by today's standards) hex editor I tried making the ".text" section begin halfway through the header and bang! ..it worked, a revelation of sorts. I imagine today's loaders may be a bit more strict because of security but I guess you can always make your own loader :)
First experience with proper ELFs was using PS2 Linux ELFs to run homebrew and games and get past Sony’s restrictions
I wonder how much of this could be done by a clever linker? There’s a lot of skill in there but how would an llm do, for the rest of us?
A linker could do this, but "clever" isn't the adjective I'd use when something randomly breaks due to it not working to standard.
Oh, ELF file manipulation. I thought this would be about getting Linux to run on a Teensy.
https://forum.pjrc.com/index.php?threads/linux-on-teensy-4-x...
The program described in this article is as simple as possible. What about something more complex, like basic "hello world"? It requires at least one more syscall and several bytes more data.
My approach to crafting "small" ELFs (in the hundreds-of-bytes range, written in relatively normal C) is like so: https://github.com/DavidBuchanan314/kurl/blob/main/golfed/el...
Take a look at the collections by the same author:
https://www.muppetlabs.com/~breadbox/software/tiny/home.html
There are some more complete programs there.
Lot of useful info here! Good work!
This is the wrong end of the issue. ELF for executables and dynamic libs is obsolete on modern hardware (same for microsoft PE+).
I am now using for most of my projects a exe/dynamic lib format of my own. This file format is so miminal a simple RFC will suffice. BUT, I will need to build dynamic libs which are system interfaces (for instance userland drivers like mesa) with this file format: problem, c++ and its runtime (and probably other similar languages with their runtimes)... as usual...
Well, I am still removing stuff from my file format, because I think this is not yet "minimal and enough" on modern hardware architecture (I think I have still too much complexity in the tracker of loaded dynamic libs).
> ELF for executables and dynamic libs is obsolete on modern hardware (same for microsoft PE+)
This is... extremely not true?
i386 are perhaps starting to die out. Has anything like this been done for amd64? Can we play such tricks with arm and aarch64?