Allow variants to specify extra kernel parameters

Dockerfile

@@ -155,7 +155,8 @@ ARG VARIANT
 ARG PRETTY_NAME
 ARG IMAGE_NAME
 ARG IMAGE_FORMAT
-ENV VARIANT=${VARIANT} VERSION_ID=${VERSION_ID} BUILD_ID=${BUILD_ID} PRETTY_NAME=${PRETTY_NAME} IMAGE_NAME=${IMAGE_NAME} IMAGE_FORMAT=${IMAGE_FORMAT}
+ARG KERNEL_PARAMETERS
+ENV VARIANT=${VARIANT} VERSION_ID=${VERSION_ID} BUILD_ID=${BUILD_ID} PRETTY_NAME=${PRETTY_NAME} IMAGE_NAME=${IMAGE_NAME} IMAGE_FORMAT=${IMAGE_FORMAT} KERNEL_PARAMETERS=${KERNEL_PARAMETERS}
 WORKDIR /root
 
 USER root

tools/buildsys/src/builder.rs

@@ -80,7 +80,11 @@ pub(crate) struct VariantBuilder;
 
 impl VariantBuilder {
     /// Build a variant with the specified packages installed.
-    pub(crate) fn build(packages: &[String], image_format: Option<&ImageFormat>) -> Result<Self> {
+    pub(crate) fn build(
+        packages: &[String],
+        image_format: Option<&ImageFormat>,
+        kernel_parameters: Option<&Vec<String>>,
+    ) -> Result<Self> {
         let output_dir: PathBuf = getenv("BUILDSYS_OUTPUT_DIR")?.into();
 
         let variant = getenv("BUILDSYS_VARIANT")?;
@@ -102,6 +106,12 @@ impl VariantBuilder {
                 Some(ImageFormat::Vmdk) => "vmdk",
             },
         );
+        args.build_arg(
+            "KERNEL_PARAMETERS",
+            kernel_parameters
+                .map(|v| v.join(" "))
+                .unwrap_or_else(|| "".to_string()),
+        );
 
         // Always rebuild variants since they are located in a different workspace,
         // and don't directly track changes in the underlying packages.

tools/buildsys/src/main.rs

@@ -192,7 +192,9 @@ fn build_variant() -> Result<()> {
 
     if let Some(packages) = manifest.included_packages() {
         let image_format = manifest.image_format();
-        VariantBuilder::build(&packages, image_format).context(error::BuildAttempt)?;
+        let kernel_parameters = manifest.kernel_parameters();
+        VariantBuilder::build(&packages, image_format, kernel_parameters)
+            .context(error::BuildAttempt)?;
     } else {
         println!("cargo:warning=No included packages in manifest. Skipping variant build.");
     }

tools/buildsys/src/manifest.rs

@@ -58,6 +58,30 @@ variant-sensitive = true
 [package.metadata.build-variant]
 included-packages = ["release"]
 ```
+
+`image-format` is the desired format of the built image.
+This can be `raw` (the default), `vmdk`, or `qcow2`.
+```
+[package.metadata.build-variant]
+image-format = "vmdk"
+```
+
+`supported-arches` is the list of architectures the variant is able to run on.
+The values can be `x86_64` and `aarch64`.
+If not specified, the variant can run on any of those architectures.
+```
+[package.metadata.build-variant]
+supported-arches = ["x86_64"]
+```
+
+`kernel-parameters` is a list of extra parameters to be added to the kernel command line.
+The given parameters are inserted at the start of the command line.
+```
+[package.metadata.build-variant]
+kernel-parameters = [
+   "console=ttyS42",
+]
+```
 */
 
 pub(crate) mod error;
@@ -123,6 +147,12 @@ impl ManifestInfo {
             .and_then(|b| b.supported_arches.as_ref())
     }
 
+    /// Convenience method to return the kernel parameters for this variant.
+    pub(crate) fn kernel_parameters(&self) -> Option<&Vec<String>> {
+        self.build_variant()
+            .and_then(|b| b.kernel_parameters.as_ref())
+    }
+
     /// Helper methods to navigate the series of optional struct fields.
     fn build_package(&self) -> Option<&BuildPackage> {
         self.package
@@ -167,6 +197,7 @@ pub(crate) struct BuildVariant {
     pub(crate) included_packages: Option<Vec<String>>,
     pub(crate) image_format: Option<ImageFormat>,
     pub(crate) supported_arches: Option<HashSet<SupportedArch>>,
+    pub(crate) kernel_parameters: Option<Vec<String>>,
 }
 
 #[derive(Deserialize, Debug)]

tools/rpm2img

@@ -177,7 +177,9 @@ set default="0"
 set timeout="0"
 
 menuentry "${PRETTY_NAME} ${VERSION_ID}" {
-   linux (\$root)/vmlinuz root=/dev/dm-0 rootwait ro \\
+   linux (\$root)/vmlinuz \\
+       ${KERNEL_PARAMETERS} \\
+       root=/dev/dm-0 rootwait ro \\
        console=tty0 console=ttyS0 random.trust_cpu=on selinux=1 enforcing=1 \\
        systemd.log_target=journal-or-kmsg systemd.log_color=0 net.ifnames=0 \\
        biosdevname=0 dm_verity.max_bios=-1 dm_verity.dev_wait=1 \\