feat(bls): boot counting (#107)

* feat(bls): parse and render boot counters

* feat(bls): sort entries with no boot tries left last

* feat(boot): strip boot counters from bls entry ids

* feat(boot): consume bls boot counter tries before booting

* fix(boot): never default to a bad boot counter entry while a good one exists

crates/boot/src/main.rs

@@ -36,6 +36,9 @@ pub mod actions;
 /// autoconfigure: Autoconfigure Sprout based on the detected environment.
 pub mod autoconfigure;
 
+/// boot_counter: Consume the boot counter tries of BLS entries.
+pub mod boot_counter;
+
 /// config: Sprout configuration mechanism.
 pub mod config;
 
@@ -407,11 +410,20 @@ fn run() -> Result<()> {
         force_boot_entry = Some(bootloader_interface_oneshot_entry.clone());
     }
 
-    // If no entries were the default, pick the first entry as the default entry.
-    if entries.iter().all(|entry| !entry.is_default())
-        && let Some(entry) = entries.first_mut()
-    {
-        entry.mark_default();
+    // Entries that have no boot counter tries left are never picked automatically.
+    // If no entries are the default, pick the first usable entry as the default entry.
+    let default_flags = edera_sprout_bls::resolve_default_flags(
+        &entries
+            .iter()
+            .map(|entry| (entry.is_default(), entry.is_bad()))
+            .collect::<Vec<_>>(),
+    );
+    for (entry, default) in entries.iter_mut().zip(default_flags) {
+        if default {
+            entry.mark_default();
+        } else {
+            entry.unmark_default();
+        }
     }
 
     // Convert the menu timeout to a duration.
@@ -465,6 +477,21 @@ fn run() -> Result<()> {
     // Execute the late phase, now that the entry is chosen but before its actions are executed.
     phase(context.clone(), &config.phases.late).context("unable to execute late phase")?;
 
+    // Consume a try from the boot counter of the selected entry.
+    // Failing to do so must not prevent the entry from booting.
+    if let Some(target) = entry.boot_counter()
+        && !target.counter.is_bad()
+    {
+        match target.consume() {
+            Ok(path) => info!("updated boot counter of entry {}: {}", entry.name(), path),
+            Err(error) => warn!(
+                "unable to update boot counter of entry {}: {:#}",
+                entry.name(),
+                error
+            ),
+        }
+    }
+
     // Execute all the actions for the selected entry.
     for action in &entry.declaration().actions {
         let action = entry.context().stamp(action);