i80k

i80k is a small kernel targeting vintage Intel CPUs like the 8086 (for now). It runs on a custom homemade board.

Note: the code is still under heavy development and must be used with caution.

Build

The kernel uses Bazel and a IA16 version of GCC compiler from tkchia/gcc-ia16 project. The toolchain can be built using the Docker container provided or by pulling the binaries from the toolchain maintainer website.

Build the toolchain

The GCC IA16 toolchain is expected to be located in toolchains/ia16-elf directory. The instructions below tell how to build it from scratch using the a Docker container.

Create the toolchain directory:

cd toolchains/
mdkir ia16-elf

Create the container image:

docker build -t build-gcc-ia16 --build-arg USER_ID=$(id -u) --build-arg GROUP_ID=$(id -g) .

Build the toolchain (that's where you take a cup of coffee):

docker run -v `pwd`/ia16-elf:/out build-gcc-ia16

Now the toolchain is available in ia16-elf directory, remove the docker image:

docker image rm build-gcc-ia16

Build the kernel

To build the kernel, install Bazel first, then run:

bazel build --config=8088-rev2 //kernel:kernel.bin

the resulting ROM image is then available in bazel-bin/kernel/kernel.bin. The --config= flags helps selecting the right build configuration for the board you want to target. Valid configurations are 8088-rev2 or 8088-rev3.

The custom Bazel toolchain declaration is located under toolchains/, see Bazel Tutorial: Configure C++ Toolchains for more details.

Run tests

To build and run a test suite, run:

bazel test --cxxopt=-std=c++14 --test_output=all <target>

For instance:

bazel test --cxxopt=-std=c++14 --test_output=all //kernel/utils:utils_test

Board configuration

The build is configured for a specific board using Bazel configurations, the parameters are located in .bazelrc. For now only one board is supported.

ROM image

The build product is a ROM image ready to be flashed on a 32kB ROM, typically an EEPROM. The ROM is layered for an EEPROM physically starting at address 0xF8000 (0xF000:0x8000). The code will run in this address space while data (initialized and uninitialized) will be relocated in the first memory segment during the early boot phase.