Yggdrasil is the name for my kernel and userspace development project which tries to follow the Unix principles (sheesh, yet another POSIX OS?) and is loosely inspired by stuff like Linux, BSD and other *nixes I've laid my hands on so far.

Building

    cp defconfig config
    export ARCH=amd64
    make

The result is build/sys/amd64/image.iso bootable ISO file. You can burn it on some physical drive or just use qemu. To run qemu, use

    make qemu

What works

Multithreading (kernel/user)
kill()/signal()
VFS implementation with non-resident ("mapper") filesystem support
ext2 driver supporting both read/write, directories and symlinks
VT100 basic control sequences for color/cursor control in tty.
ELF binary loading
fork()/exec()
ARP name resolution

What works: amd64-specific

SMP (though I haven't tested it well):
- APs are started up using InitIPI/SIPIs
- LAPIC config
- LAPIC timer for each processor
- Per-CPU scheduling queues
I/O APIC configuration:
- 8259 PIC -> I/O APIC mapping
- Trigger/polarity config from MADT table (for 8259 IRQs)
PCI:
- Device enumeration
- PCI-to-PCI bridge support
- Resolve INTA#/INTB#/INTC#/INTD# pin routing
ACPI:
- Integrated ACPICA into the kernel. Singlethreaded-only so far.
- PCI Interrupt Link Devices (_SB_.LNKx/GSIx) for dynamic PCI IRQ mapping
- Hard IRQ routes (for chipsets where there's no IRQ router and PCI traces are hardwired)
- Shutdown works (Sleep state 5)

What works: devices

RTL8139 Network Controller - both Tx/Rx
AHCI SATA controllers (R/O)
IDE controllers (R/O)