elf

std › formats › elf

ELF static executables, for Linux and the BSDs.

Invoke one header macro first thing in the program’s entry file, before any section statement, so its bytes start the image. This one is a complete Linux x86-64 program that exits with status 0:

from std.formats.elf import *
from std.x86_64.nasm import *

elf64_executable EM_X86_64, _start

_start:
    mov eax, 60     # exit
    xor edi, edi    # with status 0
    syscall

The header maps the whole image as one segment at load_address and starts execution at entry, a label in this file or imported from another one. Its sizes and entry point come from span over the linked image (std.bitter.link), so they stay correct however the program’s sections and files are laid out.

What this doesn’t produce: section headers, dynamic linking, or separate segments per section. The single segment is readable and executable by default; pass segment_flags (a combination of PF_R, PF_W, PF_X) to change that. Every multi-byte field is little-endian, as x86-64 and RISC-V are.

Macros

elf64_executable

A 64-bit ELF header and its one program header, 120 bytes. machine is EM_X86_64 or EM_RISCV, entry is the label execution starts at, and flags is the header’s e_flags, which some architectures give meaning.

elf32_executable

A 32-bit ELF header and its one program header, 84 bytes, e.g. for RV32. The parameters mean what they do for elf64_executable.

Constants