cleonos/docs/stage5.md

CLeonOS Stage5

Stage Goal

• Add ELF64 parsing and loading framework for CLKS.
• Add executable-file probe path via Limine executable request.
• Add syscall framework with int 0x80 dispatcher.
• Keep scheduler + interrupt flow integrated with syscall path.

Acceptance Criteria

• Kernel logs CLEONOS STAGE5 START.
• ELF runner initializes and probes kernel ELF metadata (entry/phnum/segments).
• Syscall framework initializes and int 0x80 returns timer ticks.
• IRQ timer and scheduler still run without panic/reboot.

Build Targets

• make setup
• make iso
• make run
• make debug

QEMU Command

• qemu-system-x86_64 -M q35 -m 1024M -cdrom build/CLeonOS-x86_64.iso -serial stdio

Common Bugs and Debugging

• KERNEL ELF PROBE FAILED:
  • Verify Limine executable file request is present in .limine_requests section.
• Syscall always returns -1:
  • Check clks_syscall_init() call order and vector 0x80 IDT gate.
• int 0x80 causes exception:
  • Ensure vector 128 stub exists and IDT gate uses DPL3-capable flags (0xEE).
• Linker undefined symbols for ELF/syscall:
  • Confirm elf64.c, elfrunner.c, syscall.c are listed in C_SOURCES.
• Interrupt instability after syscall integration:
  • Confirm timer IRQ EOI path is untouched and syscall vector path returns early.