sel4-capdl-initializer

CapDL-based system initializer

This document assumes familiarity with the upstream capdl-loader-app.

capdl-initializer

capdl-initializer is simlar in purpose to the upstream capdl-loader-app. The main practical difference is how it fits into a build system, allowing for different approaches to distribution and integration. capdl-loader-app is a C program built using CMake and depends on the system CapDL spec at link-time. capdl-initializer itself is just the initializer without the spec, and thus does not depend on the spec at build time. Instead, it is accompanied by a CLI component called capdl-initializer-add-spec which is used to append the spec to the capdl-initializer ELF image in a seperate preparation phase.

capdl-initializer depends on the libsel4 headers. These are provided in the same way as they are for the sel4-config crate and its dependants (i.e. via SEL4_PREFIX or SEL4_INCLUDE_DIRS).

Here is an example of how to build and use this crate. First, independantly of the application, build the initializer and accompanying CLI tool:

url="https://github.com/seL4/rust-sel4"

RUST_TARGET_PATH=$my_rust_target_path \
SEL4_PREFIX=$my_sel4_prefix \
    cargo install \
        -Z unstable-options \
        -Z build-std=core,alloc,compiler_builtins \
        -Z build-std-features=compiler-builtins-mem \
        --target aarch64-sel4-minimal \
        --root $my_project_local_cargo_root \
        --git $url \
        capdl-initializer

cargo install \
    --root $my_project_local_cargo_root \
    --git $url \
    capdl-initializer-add-spec

Later, prepare the initializer by adding the CapDL spec. capdl-initializer-add-spec takes a CapDL spec in JSON format. This branch of the parse-capDL tool is capable of translating a .cdl file to JSON.

parse-capDL --object-sizes=$my_object_sizes --json=spec.json $my_capdl_spec

$my_project_local_cargo_root/bin/capdl-initializer-add-spec \
    -e $my_project_local_cargo_root/bin/capdl-initializer \
    -f spec.json \
    -d $my_fill_dir \
    -o app.efl

capdl-initializer-with-embedded-spec

capdl-initializer-with-embedded-spec shares most of its code with capdl-initializer, but is built more like the upsream capdl-loader-app. The resulting root-task memory footprint is smaller than that of capdl-initializer, but building it is more complex. Instead of building the binary independantly of the spec and then adding the spec later, the spec is provided to its build.rs script at compile time via environment variables.

url="https://github.com/seL4/rust-sel4"

RUST_TARGET_PATH=$my_rust_target_path \
SEL4_PREFIX=$my_sel4_prefix \
CAPDL_SPEC_FILE=spec.json \
CAPDL_FILL_DIR=$my_fill_dir \
    cargo install \
        -Z unstable-options \
        -Z build-std=core,alloc,compiler_builtins \
        -Z build-std-features=compiler-builtins-mem \
        --target aarch64-sel4-minimal \
        --root $my_project_local_cargo_root \
        --git $url \
        capdl-initializer-with-embedded-spec