HelenOS sources
abi/arch/abs32le/include/abi/arch/elf.h
abi/arch/amd64/include/abi/arch/elf.h
abi/arch/arm32/include/abi/arch/elf.h
abi/arch/arm64/include/abi/arch/elf.h
abi/arch/ia32/include/abi/arch/elf.h
abi/arch/ia64/include/abi/arch/elf.h
abi/arch/mips32/include/abi/arch/elf.h
abi/arch/ppc32/include/abi/arch/elf.h
abi/arch/riscv64/include/abi/arch/elf.h
abi/arch/sparc64/include/abi/arch/elf.h
abi/include/abi/elf.h
kernel/generic/include/lib/elf.h
uspace/lib/c/include/elf/elf.h
uspace/lib/posix/include/libc/elf/elf.h
HelenOS homepage, sources at GitHub