feat(boot): add the bls-strict-mode option

Add --bls-strict-mode and bls-strict-mode in the options of sprout.toml.
It does nothing yet; the behaviors it controls follow.

crates/boot/src/main.rs

@@ -199,6 +199,13 @@ fn run(reboot_on_error: &mut bool) -> Result<()> {
             .context("unable to set loader path in bootloader interface"),
     );
 
+    // Strict mode can be asked for on the command line or in the configuration.
+    let mut options = options;
+    options.bls_strict_mode |= config.options.bls_strict_mode;
+    if options.bls_strict_mode {
+        info!("BLS strict mode is enabled");
+    }
+
     // Create the root context.
     let mut root = RootContext::new(loaded_image_path, timer, options);
 

crates/boot/src/options.rs

@@ -29,6 +29,8 @@ pub struct SproutOptions {
     pub menu_style: Option<MenuStyle>,
     /// Retains the boot console before boot.
     pub retain_boot_console: bool,
+    /// Makes Sprout follow the Boot Loader Specification and systemd-boot exactly.
+    pub bls_strict_mode: bool,
 }
 
 /// The default Sprout options.
@@ -42,6 +44,7 @@ impl Default for SproutOptions {
             menu_timeout: None,
             menu_style: None,
             retain_boot_console: false,
+            bls_strict_mode: false,
         }
     }
 }
@@ -60,6 +63,7 @@ impl SproutOptions {
             MenuTimeout,
             MenuStyle,
             RetainBootConsole,
+            BlsStrictMode,
         }
 
         // All the options for the Sprout executable.
@@ -78,6 +82,8 @@ impl SproutOptions {
                 .help_text("Boot menu style, basic, simple or graphical"),
             Opt::flag(ArgID::RetainBootConsole, &["--retain-boot-console"])
                 .help_text("Retain boot console before boot"),
+            Opt::flag(ArgID::BlsStrictMode, &["--bls-strict-mode"])
+                .help_text("Follow the BLS specification and systemd-boot exactly"),
         ]);
 
         // Acquire the arguments as determined by the UEFI core.
@@ -141,6 +147,10 @@ impl SproutOptions {
                             // Retain the boot console before booting.
                             result.retain_boot_console = true;
                         }
+                        ArgID::BlsStrictMode => {
+                            // Follow the BLS specification and systemd-boot exactly.
+                            result.bls_strict_mode = true;
+                        }
                         ArgID::Help => {
                             let ctx = HelpWriterContext {
                                 options: &OPTIONS,

crates/config/src/lib.rs

@@ -91,6 +91,12 @@ pub struct OptionsConfiguration {
     /// Enables autoconfiguration of Sprout based on the environment.
     #[serde(default)]
     pub autoconfigure: bool,
+    /// Makes Sprout follow the Boot Loader Specification and systemd-boot exactly where it
+    /// otherwise differs for convenience or safety. For example, the extended boot loader
+    /// partition is always read, a one-shot entry only sets the default entry, and entries with
+    /// missing files are hidden. See the README for everything it changes.
+    #[serde(rename = "bls-strict-mode", default)]
+    pub bls_strict_mode: bool,
 }
 
 /// The default configuration, which matches an empty configuration file.
@@ -118,6 +124,7 @@ impl Default for OptionsConfiguration {
             menu_timeout: None,
             menu_style: Default::default(),
             autoconfigure: false,
+            bls_strict_mode: false,
         }
     }
 }
@@ -164,6 +171,12 @@ mod tests {
         assert_eq!(default.options.autoconfigure, empty.options.autoconfigure);
     }
 
+    #[test]
+    fn bls_strict_mode_is_off_by_default() {
+        assert!(!RootConfiguration::default().options.bls_strict_mode);
+        assert!(!empty().options.bls_strict_mode);
+    }
+
     #[test]
     fn menu_timeout_is_unset_by_default() {
         assert_eq!(RootConfiguration::default().options.menu_timeout, None);