boot: Add freestanding version of unload_image

Author: nicholasbishop

uefi/src/boot.rs

@@ -319,6 +319,19 @@ pub fn load_image(parent_image_handle: Handle, source: LoadImageSource) -> Resul
     }
 }
 
+/// Unloads a UEFI image.
+///
+/// # Errors
+///
+/// * [`Status::UNSUPPORTED`]: the image has been started, and does not support unload.
+/// * [`Status::INVALID_PARAMETER`]: `image_handle` is not valid.
+pub fn unload_image(image_handle: Handle) -> Result {
+    let bt = boot_services_raw_panicking();
+    let bt = unsafe { bt.as_ref() };
+
+    unsafe { (bt.unload_image)(image_handle.as_ptr()) }.to_result()
+}
+
 /// A buffer returned by [`locate_handle_buffer`] that contains an array of
 /// [`Handle`]s that support the requested protocol.
 #[derive(Debug, Eq, PartialEq)]