feat(initrd): support chaining multiple initrds (#101)

Add linux-initrd-chain to the chainload action and initrd-chain to the
edera action. Each file in the list is read in order and concatenated
into a single initrd. The chain can't be combined with the single
initrd option on the same action.

BLS entries with multiple initrds, either as repeated initrd lines or
as multiple paths on one line, previously only loaded the last one.
Parse all of them and set them in the initrd-0 through initrd-7 slots,
which the autoconfigured BLS action now chains. Unused slots stamp to
the filesystem root and are skipped. Entries with more than 8 initrds
are skipped with a warning.

crates/config/src/actions/chainload.rs

@@ -18,4 +18,9 @@ pub struct ChainloadConfiguration {
     /// generally better and safer as it can support additional load options in the future.
     #[serde(default, rename = "linux-initrd")]
     pub linux_initrd: Option<String>,
+    /// An optional list of paths to Linux initrds to chain together.
+    /// The contents of each initrd are concatenated in order and loaded as a single initrd
+    /// using the same mechanism as `linux-initrd`. This cannot be used with `linux-initrd`.
+    #[serde(default, rename = "linux-initrd-chain")]
+    pub linux_initrd_chain: Vec<String>,
 }

crates/config/src/actions/edera.rs

@@ -14,6 +14,11 @@ pub struct EderaConfiguration {
     /// The path to the initrd to load for dom0.
     #[serde(default)]
     pub initrd: Option<String>,
+    /// The paths to the initrds to chain together for dom0.
+    /// The contents of each initrd are concatenated in order and loaded as a single initrd.
+    /// This cannot be used with `initrd`.
+    #[serde(default, rename = "initrd-chain")]
+    pub initrd_chain: Vec<String>,
     /// The options to pass to the kernel.
     #[serde(default, rename = "kernel-options")]
     pub kernel_options: Vec<String>,