I'm looking for some sort of "universal loader and dynamic linker",
capable of loading in memory an executable (ELF or other, the format
is not a requisite at this time) for any of the "major" architectures
that have LLVM backends (namely: x86, x86_64, ARM, ARM64, PPC, PPC64,
MIPS32, MIPS64), including also relocation, and loading of symbols
from dynamic libraries that the executable depends on.
The final memory representation of the executable should be "ready to
be executed". Before you ask "what OS?, what about syscalls?", let's
assume the executable doesn't use any library from the OS, and that
there are only a couple of basic syscalls for terminal I/O only, and
that such syscalls are already hooked in advance by a tweaked C
runtime (i.e.: the executable won't use any syscall protocol, just
call hooks in the loader, thanks to the tweaked C runtime).
Does LLVM provide any infrastructure ready for doing this?
Or do you know of any other open source project that could be used for this?
After some weeks searching, my best matches have been:
1- Google NaCl : I think all or almost all of the architectures listed
above are supported. However, NaCl seems to be facing an abandonware
status (they're migrating to WebAssembly, but wasm cannot manage
native code from the architectures above if I'm reading the specs
correctly). Maybe NaCl would be the way to go, but their migration
plan makes me doubt.
2- The Linux compatibility layer in NetBSD. Its main difficulties
would be that not all of the 8 architectures listed above are
supported (I believe only x86, x86_64, ARM32 and PPC32 are supported),
and that it's more complex than necessary because it performs syscall
protocol emulation. Also another difficulty is that it depends on the
NetBSD kernel to work, but, anyway, it's a start, and it could
probably be done from it.
3- Today I just found a project I didn't know: Angr
(http://angr.io/index.html) which has CLE (a loader that stands for
"CLE Loads Everything", and that is capable of loading not only ELF,
but also PE, and some subset of Mach-o). However, I only gave a quick
glimpse at it, and I'm not really sure that CLE is capable of putting
the executable in memory so that it's "ready to be executed" (with all
relocation, linked to required symbols from dynamic libraries,
Would you recommend any of these 3 approaches that I found? Or do you
know of any other, better suited for the task?
Or maybe LLVM already has infrastructure for this?