elf-binary

Code created during recording the Writing a Linux ELF Binary by Hand video.

We write a 164 bytes long x86-64 ELF binary. A proper hello world executable.

Requirements

Just a C compiler.

Build

gcc -std=c17 -o main ./main.c
gcc -std=c17 -static -o main ./main.c
nasm -felf64 -o hello_asm.o ./hello_asm.asm
ld -o hello_asm ./hello_asm.o
objdump -d -M intel ./hello_asm
gcc -std=c17 -o elf ./elf.c
./elf
chmod a+x ./bin
./bin

Useful Commands

readelf -h ./bin
readelf -l ./bin
hexdump -C ./bin
cat /proc/[pid]/maps

Documentation

man 5 elf
man 2 write
man 2 exit

Links

Online man page: man 5 elf

To Download the Intel Manuals: Intel Manuals

Linux Kernel's program loader code: https://github.com/torvalds/linux/blob/master/fs/binfmt_elf.c