[llvm-dev] Relinking (syscall-free) ELF executable into Mach-O and PE executables

[Matt P. Dziubinski via llvm-dev]

Hi,

On 7/20/2018 09:46, ardi via llvm-dev wrote:
> Would this be possible with just LLVM tools, or would other
> libraries/tools also be needed?
I'd expect you'd run into the issues mentioned by Reid.

That being said, in terms of building blocks -- i.e., executables 
manipulation per se -- I'd recommend LIEF (Library to Instrument 
Executable Formats):
https://github.com/lief-project/LIEF

It supports multiple formats (including ELF, PE, and Mach-O). What's 
relevant here in particular is that you can extract code and data from 
an existing executable -- as well as build another one from scratch 
(with a given code and data):
https://lief.quarkslab.com/doc/latest/tutorials/01_play_with_formats.html
https://lief.quarkslab.com/doc/latest/tutorials/02_pe_from_scratch.html

One of the challenges you may also run into is (mentioned in 
https://lief.quarkslab.com/doc/latest/tutorials/08_elf_bin2lib.html -- 
admittedly a somewhat different context):
"For non-PIE executables such transformation would be very difficult 
because it requires to transform first the executable into a relocatable 
executable. It means creating relocations, patching absolute jump, …"

In terms of existing work, you may also want to take a look at:
- Exodus (a tool to relocate Linux ELF binaries from one system to 
another): https://github.com/Intoli/exodus
- loadlibrary (a library that allows native Linux programs to load and 
call functions from a Windows DLL): https://github.com/taviso/loadlibrary
- wine-binfmt: https://reposcope.com/package/wine-binfmt

More executables resources which may be of help:
https://github.com/MattPD/cpplinks/blob/master/executables.md

Best,
Matt