feat(apps): permission manager equips apps (manifest+consent+decisions in /system), launches via init w/ file grant; shell unprivileged (/home); install/apps/allow/revoke; revoke stops running app; app-image tool; counter app

crates/libkos/src/fs.rs

@@ -49,6 +49,8 @@ impl DirEntry {
 pub struct Storage {
     ep: CapSlot,
     buf: &'static mut [u8],
+    /// What maps `buf`; dropping it unmaps it.
+    region: CapSlot,
 }
 
 impl Storage {
@@ -66,7 +68,12 @@ impl Storage {
         };
         let mapped = crate::window::map_buffer(region, va).map_err(|_| FsError::Failed)?;
         let buf = mapped.get_mut(..size).ok_or(FsError::Failed)?;
-        Ok(Self { ep, buf })
+        Ok(Self { ep, buf, region })
+    }
+
+    /// Unmaps the buffer, freeing its address for another connection.
+    pub fn detach(self) {
+        syscall::drop_cap(self.region);
     }
 
     fn call(&self, words: [usize; 4]) -> Result<[usize; 4]> {