x86_64 kernel written in Rust, following Philipp Oppermann's blog series.

Setup

• Rust nightly (required for build-std and custom JSON target)
• QEMU (for running)

Structure

• kernel/ — the kernel crate (no_std, custom target x86_64-bill.json). Has both lib.rs (shared test infrastructure, serial, VGA buffer) and main.rs (entry point via entry_point! macro from bootloader_api 0.11.17).
• runner/ — a host-side helper that wraps the kernel ELF into a bootable disk image and runs it in QEMU. Used both for cargo run (via root build.rs) and cargo test.
• Root build.rs — builds the kernel subcrate, then creates a bootable disk image using bootloader::BiosBoot.

Done

• Freestanding binary (no_std, no_main, custom entry point _start, panic handler)
• Custom x86_64 target spec (x86_64-unknown-none, LLD linker, panic=abort, no SIMD, soft-float)
• Build-std config for core/compiler_builtins recompilation
• Hello World via VGA text buffer at 0xb8000
• Bootable disk image via bootloader 0.11.17 + bootloader_api 0.11.17
• cargo run boots in QEMU
• Serial port driver (COM1, 0x3F8) via raw x86_64 port I/O
• print!/println! macros (VGA text + framebuffer)
• serial_print!/serial_println! macros (COM1 serial)
• Testing framework: custom_test_frameworks, test_runner, exit_qemu via isa-debug-exit
• Test runner crate: creates bootable disk image + runs QEMU with test args, maps exit code 33 -> 0
• cargo test --bin kernel --no-run compiles
• VGA text mode driver (safe wrapper around VGA buffer)
• println macro

Next

• cargo test --bin kernel — in progress (runner compilation inherits build-std/target config from kernel)
• Interrupt handling (IDT, PIC, CPU exceptions)
• Memory management (page tables, heap allocator)

Run

cargo run

Boots the kernel in QEMU. The disk image is created by build.rs using bootloader::BiosBoot.

Test

cd kernel
cargo test --bin kernel --no-run   # compiles test binary
cargo test --bin kernel             # also runs in QEMU (WIP)

Tests run inside QEMU via isa-debug-exit. Results are reported over serial. Exit code 0x21 (33) from QEMU is mapped to exit code 0 by the runner.

Notes

• Uses bootloader 0.11.17 (not the deprecated bootimage crate). The kernel entry point uses bootloader_api::entry_point!.
• .cargo/config.toml in kernel/ uses [target.'cfg(target_os = "none")'] for the runner, matching the custom target's "os": "none".
• QEMU must be in PATH.
• The kernel workspace includes runner/ as a member for builds, but the runner must be compiled for the host (not the custom bare-metal target).