feat: kargs module

modules/kargs/README.md

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+# kargs
+
+The kargs module injects kernel arguments into the image.
+
+Kernel arguments can be used to define how kernel will interact with the hardware or software.
+
+Instead of modifying & rebuilding the kernel, it is much easier to just input the kernel arguments & `bootc` will do its job.
+
+You can see how `bootc` injects kernel arguments [here](https://containers.github.io/bootc/building/kernel-arguments.html).
+
+For this reason, it is required to have `bootc` installed & used in the image.  
+By usage, it means that instead of `rpm-ostree update`, you need to use `bootc update` for kargs to get applied on next boot.  
+
+To see which kargs are currently applied to the system in run-time, you can issue `rpm-ostree kargs` command.

modules/kargs/kargs.sh

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+#!/usr/bin/env bash
+
+set -euo pipefail
+
+if ! command -v bootc &> /dev/null; then
+  echo "ERROR: 'bootc' package is not installed, please install it, as it's necessary for injecting kargs."
+  exit 1
+fi
+
+KARGS_D="/usr/lib/bootc/kargs.d"
+BLUEBUILD_TOML="${KARGS_D}/bluebuild-kargs.toml"
+
+get_json_array KARGS 'try .["kargs"][]' "${1}"
+formatted_kargs=$(printf '"%s", ' "${KARGS[@]}")
+formatted_kargs=${formatted_kargs%, }
+
+ARCH=$(echo "${1}" | jq -r 'try .["arch"]')
+formatted_arch=$(echo "${ARCH}" | sed 's/[^, ]\+/"&"/g')
+
+if [[ ${#KARGS[@]} -gt 0 ]]; then
+  # Make kargs.d directory in case it doesn't exist
+  mkdir -p "${KARGS_D}"
+  # If bluebuild-kargs.toml already exists from the previous module run, append a new suffixed toml file instead
+  if [[ -f "${BLUEBUILD_TOML}" ]]; then
+    counter=1
+    new_filename="${KARGS_D}/bluebuild-kargs-${counter}.toml"
+    while [[ -f "${new_filename}" ]]; do
+        counter=$((counter + 1))
+        new_filename="${KARGS_D}/bluebuild-kargs-${counter}.toml"
+    done
+    BLUEBUILD_TOML="${new_filename}"
+  fi
+  # Write kargs to toml file
+  echo "Writing following kernel arguments to kargs.d TOML file: ${formatted_kargs}"
+  echo "kargs = [${formatted_kargs}]" > "${BLUEBUILD_TOML}"
+  if [[ "${ARCH}" != "null" ]]; then
+    echo "Those kernel arguments are applied to the following specific OS architecture(s): ${formatted_arch}"
+    echo "match-architectures = [${formatted_arch}]" >> "${BLUEBUILD_TOML}"
+  fi
+else
+  echo "ERROR: You did not include any kernel arguments to inject in the image."
+  exit 1
+fi

modules/kargs/kargs.tsp

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+import "@typespec/json-schema";
+using TypeSpec.JsonSchema;
+
+@jsonSchema("/modules/kargs-latest.json")
+model KargsModuleLatest {
+  ...KargsModuleV1;
+}
+
+@jsonSchema("/modules/kargs-v1.json")
+model KargsModuleV1 {
+  /** The kargs module injects kernel arguments into the image.
+   * https://blue-build.org/reference/modules/kargs/
+   */
+  type: "kargs" | "kargs@v1" | "kargs@latest";
+
+  /** Defines on which OS architectures are kargs applied. Defaults to all architectures if ommited. */
+  `arch`?: string;
+
+  /** Kargs to inject in the image. */
+  `kargs`: Array<string>;
+}

modules/kargs/module.yml

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+name: kargs
+shortdesc: The kargs module injects kernel arguments into the image.
+example: |
+  type: kargs
+  arch: x86_64, aarch64 # only injects kernel arguments to those specific OS architectures
+  kargs:
+    - console=ttyS0,114800n8
+    - mitigations=on
+    - systemd.unified_cgroup_hierarchy=0