Elfkit

An elf read and manipulation library in pure Rust (written from scratch, no bfd, no gnu code, no license infections), intended to be used in binary manipulation utils such as strip, chrpath, objcopy and ld. The end goal is to build a well designed library that facilitates all sorts of binary manipulation magic.

elfkit can now link elfkit, so it's reasonably complete for x86_64. But it's definitely not stable yet and might produce incorrect code.

Using the linker

The quickest way to use elfkit with Rust is with korhal/stasis.

You can also either build from source or download binaries. GCC does not have an option to use a foreign linker, so we need to pretend we're ld.gold, like so:

curl -L https://github.com/aep/elfkit/releases/download/0.0.4/elfkit-0.0.4.tar.xz | tar xvjf -
export PATH="$PWD/elfkit-0.0.4/:$PATH"
musl-gcc -fuse-ld=gold main.c

For using elfkit for compiling Rust code, add the following to ~/.cargo/config:

[target.x86_64-unknown-linux-musl]
rustflags = [
    "-C", "link-arg=-fuse-ld=gold",
    "-C", "link-arg=-Wl,-dynamic-linker,/usr/local/musl/lib/libc.so",
]

When compiling from source, create the ld.gold symlink manually:

cargo build --release --bin ld
ln -s "$PWD/target/release/ld" /usr/local/bin/ld.gold

Other binutils

readelf:

implementation status

binutils

type	status	gnu compatible
ldd	done	no
readelf	done	no
ld	wip	wip
objdump	-	-
ar	-	-
as	-	-
nm	-	-
strip	-	-

section parsers

type	read	write
symbols	done	done
strtab	done	done
relocations	done	done
dynamic	done	done
note	-	-
gnu_hash	-	-
hash	-	mvp
versym	-	-
verneed	-	-

architectures

abi	parser	linker
x86_64	done	wip
mips32r2 o32	done
arm eabi	done

modular linker toolkit

• Loader: loads elf objects from disk
• Linker: produces a link graph of sections from a loader
• Collector: bakes multiple sections into a single object
• Relocator: applies relocations to a combined object

alternatives

• goblin mach-o and archive support, no-std support, very low level
• elf most popular, most generic use case, no writing, no section parsing
• xmas-elf zero alloc (good for writing an OS), read only

references

• https://en.wikipedia.org/wiki/Executable_and_Linkable_Format
• https://github.com/hjl-tools/x86-psABI/wiki/x86-64-psABI-r252.pdf
• https://software.intel.com/sites/default/files/article/402129/mpx-linux64-abi.pdf
• http://infocenter.arm.com/help/topic/com.arm.doc.ihi0044f/IHI0044F_aaelf.pdf
• https://dmz-portal.imgtec.com/wiki/MIPS_ABI_Project
• https://dmz-portal.imgtec.com/wiki/MIPS_O32_ABI_-_FR0_and_FR1_Interlinking
• http://www.mindfruit.co.uk/2012/06/relocations-relocations.html#reloc_types_table
• https://www.akkadia.org/drepper/tls.pdf