Anatomy of an ELF executable

Y	Hacker News new \| ask \| show \| jobs

	Anatomy of an ELF executable (kishuagarwal.github.io)
	241 points by kishu18 2613 days ago

7 comments

dietrichepp 2613 days ago

Strongly recommend reading "How To Write Shared Libraries" by Ulrich Drepper https://software.intel.com/sites/default/files/m/a/1/e/dsoho...

I recently dove into ELF files so I could convert ELF binaries to DOS EXE, for a little bit of retro programming with modern compilers. Not that I couldn't have used DJGPP.

link

unqueued 2613 days ago

> I recently dove into ELF files so I could convert ELF binaries to DOS EXE, for a little bit of retro programming with modern compilers. Not that I couldn't have used DJGPP.

That sounds pretty cool, did you make anything you could share?

link

dietrichepp 2612 days ago

Going to post it to GitHub when I have a moment. I literally wrote the code a couple weeks ago.

Edit: https://github.com/depp/elf2dos

link

kishu18 2613 days ago

Thanks for the suggestion @dietrichepp. Will definitely read.

link

zonovar 2613 days ago

Interesting article. When I was studying the elf format myself in the past I've also found very useful this poster. https://github.com/corkami/pics/blob/master/binary/elf101/el... The author has made many more for similar binary formats.

link

russellbeattie 2612 days ago

COM files are great... no headers, you just sort of start. Data, code... whatever.

link

saagarjha 2613 days ago

> You can ignore the directives starting with cfi. They are used for call stack unwinding in case of exceptions.

It might be worth compiling with -fno-asynchronous-unwind-tables, which will get rid of those.

link

kishu18 2613 days ago

Thanks for the suggestion. Do you have any good reference for reading about this feature?

link

saagarjha 2613 days ago

GCC's option page lists what it does: https://gcc.gnu.org/onlinedocs/gcc/Code-Gen-Options.html. However, it's not all that obvious that this is the flag that controls whether the "cfi" labels are emitted. Here's a more general Stack Overflow question about creating nice assembly output: https://stackoverflow.com/questions/38552116/how-to-remove-n...

link

kishu18 2613 days ago

Nice. Thanks for sharing the stackoverflow link. Will check that.

link

ddcc7 2613 days ago

Are you the author? Great job for the detailed writeup. Small nit, I noticed you misspelled the interpreter section, it should be .interp instead of .intrep

link

kishu18 2612 days ago

Thanks @ddcc7. Yes, I am the author. Fixed the spelling mistake.

link

ncmncm 2613 days ago

ELF may find new life as a format for data structures in persistent RAM, given a few extensions.

link

tantalor 2613 days ago

Mods fix title: "Life of a binary"

link

kishu18 2613 days ago

I don't see any option to edit the title now. Anyways, I don't see it would change any meaning of the article.