In my previous post Learning TinyCC, I tried to use tcc to compile xv6

The c compiler part works fine, and some asm code; the boot related code compiling, linking and objdump&objcopy jobs have to be done by gcc

So, in other to use tcc to build the whole xv6, below changes are required:

  1. assembler change to address below issues
    • mnemonics instructions like pushal, popal, ljmpl not supported by tcc
    • .comm pysedo instruction support or workaround

  2. compiler builtin functions like _sync_synchronize()

  3. special handling for boot:
    • linker support for -N -e start -Ttext 0x7C00
    • when entry.S, entryother.S are compiled by tcc with minor change, qemu won’t boot xv6.img
    • utility functions for objdump, objcopy, sign.pl, etc …
    • make sure bootblock size is less than 510 bytes, otherwise it won’t fit bootsector

Last updated: December 3, 2025