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universalisos/kernel
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Fábio Coutada 173b2c3330 feat(kernel): add Stage 1 bare-metal hypervisor skeleton for QEMU ARM virt 
- Add kernel/arch/arm/boot.S with ARMv7 assembly entry, stack setup, BSS clear
- Add kernel/arch/arm/linker.ld for QEMU virt memory layout (load at 0x40000000)
- Add kernel/arch/arm/uart.c/uart.h for PL011 serial output
- Add kernel/kernel.c with kernel_main() idle loop
- Add kernel/Makefile for arm-none-eabi-gcc cross-compile and QEMU launch
- Add kernel/README.md with build/run instructions
- Ignore kernel build artifacts in .gitignore
2026-07-06 22:51:56 +01:00
..
arch/arm feat(kernel): add Stage 1 bare-metal hypervisor skeleton for QEMU ARM virt 2026-07-06 22:51:56 +01:00
kernel.c feat(kernel): add Stage 1 bare-metal hypervisor skeleton for QEMU ARM virt 2026-07-06 22:51:56 +01:00
Makefile feat(kernel): add Stage 1 bare-metal hypervisor skeleton for QEMU ARM virt 2026-07-06 22:51:56 +01:00
README.md feat(kernel): add Stage 1 bare-metal hypervisor skeleton for QEMU ARM virt 2026-07-06 22:51:56 +01:00

README.md

Universalisos Kernel — Stage 1 Bare-Metal Skeleton

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

Building

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

cd kernel
make

Outputs:

  • kernel.elf — ELF image for debugging
  • kernel.bin — raw binary for QEMU -kernel

Running in QEMU

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 skeleton running on QEMU ARM virt.

Press Ctrl+A then X to exit QEMU.

Inspecting the binary

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.c PL011 UART driver
arch/arm/uart.h UART interface
kernel.c 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.