hello.elf and hello-no-hacks.elf are custom-generated ELF executable files for x86-64, System V compatible -- Linux, FreeBSD, MacOS -- systems. They print "Hello, World!" when executed.

My goal is to make them pretty small. The current sizes are:

The ELF files are generated using the gen_msg_elf.py script. It generates an ELF executable that prints a message of your choice. You can run it yourself by supplying a FILE_PATH and then MSG argument. Run ./gen_msg_elf.py --help for more details. The source code of gen_msg_elf.py may be educational if you're trying to generate your own ELF files from scratch. The bit that generates the executable is around 250 lines of mostly sequential code with added "explainer" variables.

hello.elf is generated using hacks that intentionally corrupt the ELF file but do not prevent it from executing. hello-no-hacks.elf does not use these hacks, producing a fully valid ELF file. The hacks allow hello.elf to be smaller as seen above. Similar and more extensive hacks can be found in this great article https://www.muppetlabs.com/~breadbox/software/tiny/teensy.html -- It's worth a read if you have the time.

The asm-reference/ directory contains a reference "Hello, World!" implementation is NASM.

• Wikipedia on ELF: https://en.wikipedia.org/wiki/Elf
• Linux Manpage on ELF: man elf
• Disassembly tools: readelf, objdump, hexdump

To learn more about ELF, Assembly and x86-64 instructions.

Treat all code in this repo as MIT licensed. Treat other assets as CC0 / Public Domain.

Attribution by linking to this repo would be appreciated but is not required.