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 x86-64  |  Limine  |  ring-3  |  no libc

A 64-bit x86 kernel written from scratch in C and Assembly. Boots via Limine into higher half, brings up its own memory management, scheduler, syscall interface, and a RAM-backed filesystem — then drops into an interactive shell.

No libc. No shortcuts.

---

What's running

┌─────────────────────────────────────────┐
│  User Programs (Ring 3)                 │
├─────────────────────────────────────────┤
│  Syscall Interface  (int 0x80)          │
├─────────────────────────────────────────┤
│  Process Manager  │  RAM Filesystem     │
├───────────────────┼─────────────────────┤
│  Scheduler (PIT)  │  Shell              │
├───────────────────┴─────────────────────┤
│  Virtual Memory Manager (VMM)           │
├─────────────────────────────────────────┤
│  Physical Memory Manager (PMM)          │
├─────────────────────────────────────────┤
│  GDT/TSS │ IDT/PIC │ Keyboard │ Timer  │
├─────────────────────────────────────────┤
│  Limine Bootloader                      │
└─────────────────────────────────────────┘

• Bootloader — Limine v8, higher half kernel at 0xffffffff80000000
• GDT + TSS — flat 64-bit segments, kernel/user, TSS rsp0 per-process
• IDT + PIC — 256 vectors, remapped IRQs, installable IRQ handlers
• PMM — bitmap allocator over Limine memmap, 4KB page granularity
• VMM — 4-level page tables (PML4→PDPT→PD→PT), own CR3, identity + higher-half map
• PIT Timer — 1kHz IRQ0, tick counter, preemption foundation
• Process Manager — PCB, round-robin scheduler, ring 3 transition, context switch in asm
• Syscall — int 0x80 DPL=3 gate, dispatch table (write, exit, getpid)
• RAM Filesystem — flat in-memory FS, built-in test binaries
• Shell — ls, cat, exec, meminfo, ps, keyboard-driven

---

Boot

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Build & run

make all && make run

Requires: gcc, nasm, ld, xorriso, qemu-system-x86_64

Flash to hardware

./flash.sh
sudo ./prepare_flash.sh image.hdd /dev/sdX