Channer OS

A hand-written 32-bit x86 operating system: custom bootloader, protected mode, paging, a heap, preemptive multitasking, a persistent filesystem, a TCP/IP-ish network stack (ARP + ICMP), and an interactive shell — all from scratch, no libraries.

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            Channer OS  v0.1
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channer> ping 10.0.2.2
PING 10.0.2.2 32 bytes of data
reply from 10.0.2.2: icmp_seq=1 time=0 ms
channer> ps
ID  STATE    SWITCHES  WORK       NAME
0   running  35        0          shell
1   ready    35        91637780   miner
2   ready    22        69682784   render

Features

• Bootloader (boot/mbr.asm) — a 512-byte MBR that loads the kernel from disk in 32 KB chunks via INT13h LBA reads, so the kernel can grow large.
• Protected mode — GDT, a runtime-built IDT (interrupts/idt.c), and PIC remapping. Interrupt stubs (interrupts/isr.asm) save a full register frame and iret correctly.
• Memory — E820 RAM detection, paging with a recursive page directory and a demand-paging fault handler, a bitmap frame allocator, and a kalloc/kfree heap.
• Preemptive multitasking (proc/task.c) — round-robin kernel threads context-switched from the timer IRQ by swapping the saved stack pointer.
• Console (screen.c) — 80x25 VGA text with scrolling, a hardware cursor, and colors. All output is mirrored to COM1 serial for headless debugging.
• Keyboard (drivers/char/keyboard.c) — scancode set 1, shift/caps, and a type-ahead ring buffer feeding a blocking readLine.
• Filesystem (filesystem/fs.c) — ChannerFS, a small persistent filesystem stored on disk (LBA 2048+) via an ATA PIO driver (drivers/block/disk.c). Create, read, write, append, delete; survives reboots.
• Networking (drivers/net/rtl8139.c, net/net.c) — an RTL8139 NIC driver (PCI discovery, DMA RX ring, TX), plus Ethernet / ARP / IPv4 / ICMP echo. It can resolve MACs and ping.
• Shell (shell.c) — an interactive CLI tying it all together.

Build & run

Requires a cross toolchain + QEMU (macOS/Homebrew):

brew install x86_64-elf-gcc nasm qemu

Then:

make build     # -> out/os_image.img
make run       # boot in QEMU (VGA window + serial on your terminal)
make debug     # headless: serial -> out/serial.log, CPU trace -> out/qemu.log

build.sh uses x86_64-elf-gcc -m32 because the system i386-elf-gcc install here is missing its own assembler/linker.

Shell commands

help                 list commands           ls                 list files
clear                clear the screen        cat <file>         print a file
echo <text>          print text              write <file> <txt> (over)write a file
about                about this OS           append <file> <txt> append to a file
mem                  memory info             touch <file>       create empty file
uptime / ticks       time since boot         rm <file>          delete a file
peek <hexaddr>       read memory             sync               flush FS to disk
color <0-15>         set text color          format             reformat the FS
reboot               restart
                                             ps                 list tasks
net                  NIC / IP info           spawn [name]       start a worker task
arp <ip>             resolve a MAC           kill <id>          stop a task
ping <ip>            ICMP echo

Layout

boot/mbr.asm                 stage-1 bootloader (LBA chunked loader)
linker.ld                    flat binary, loaded at 0x8200
kernel/kernel_entry.asm      real mode -> protected mode entry
kernel/kernel.c              unity build: #includes the C sources in order
kernel/screen.c              VGA text console + serial mirror
kernel/shell.c               interactive shell
kernel/stubs.c               weak fallbacks for optional subsystem hooks
kernel/interrupts/           isr.asm stubs + idt.c (runtime IDT + dispatch)
kernel/drivers/              port I/O, serial, keyboard, ATA disk, PCI, RTL8139
kernel/memory/               paging, frame allocator, heap
kernel/proc/task.c           preemptive scheduler
kernel/filesystem/fs.c       ChannerFS
kernel/net/net.c             ARP / IPv4 / ICMP

The earlier ext4 / DMA-ATA / old-scheduler experiments are left in the tree (filesystem/ext4.c, drivers/block/ata/, proc/process.c, proc/scheduler.c, interrupts/interrupt_handlers.c) but are not compiled into the current build.

Known limitations / next steps

• Kernel threads run in ring 0; there is no user mode (ring 3) or syscall layer yet. The IDT + TSS scaffolding to add it is in place.
• ChannerFS uses fixed per-file slots (30 files, 8 KB each) — simple and fragmentation-free, but not a general allocator.
• The network stack does ARP + ICMP; no UDP/TCP/DHCP yet (the static IP matches QEMU's user-net default, 10.0.2.15).
• Networking RX is polled, not interrupt-driven.