# Universalisos Kernel — Stage 1 Bare-Metal Skeleton (C++)

This is the first bootable type-1 hypervisor milestone for Universalisos: a
minimal bare-metal kernel written in **C++** that runs on QEMU's ARM `virt`
machine and prints to the PL011 UART.

## Building

Requires `arm-none-eabi-gcc` and `qemu-system-arm`.

```bash
cd kernel
make
```

Outputs:
- `kernel.elf` — ELF image for debugging
- `kernel.bin` — raw binary for QEMU `-kernel`

## Running in QEMU

```bash
make run
```

This runs `qemu-system-arm` with the ELF image so that QEMU loads the kernel
at the address specified in the linker script.

Expected output:

```
Universalisos type-1 hypervisor booted.
Stage 1: bare-metal C++ skeleton running on QEMU ARM virt.
```

Press `Ctrl+A` then `X` to exit QEMU.

## Inspecting the binary

```bash
make dump
```

## Layout

| File | Purpose |
|------|---------|
| `arch/arm/boot.S` | Assembly entry point, stack/BSS setup |
| `arch/arm/linker.ld` | Memory layout for QEMU virt (load at 0x40000000) |
| `arch/arm/uart.cpp` | PL011 UART driver |
| `arch/arm/uart.h` | UART interface |
| `kernel.cpp` | `kernel_main()` entry point |

## Design notes

- The kernel is loaded by QEMU at RAM base `0x40000000`.
- A 64 KiB stack is reserved immediately after the BSS section.
- Interrupts are disabled in the boot stub; the kernel idles with `wfi`.