uefi-helpers: remove exit hook

No need for the complicated and error-prone approach using an event.

Author: phip1611

uefi-services/src/lib.rs

@@ -9,5 +9,5 @@ pub use uefi::{print, println};
 
 #[deprecated = "WARNING: `uefi-services` is deprecated. Functionality was moved to `uefi::helpers::init`."]
 pub fn init(st: &mut SystemTable<Boot>) -> Result<Option<Event>> {
-    uefi::helpers::init(st)
+    uefi::helpers::init(st).map(|_| None)
 }

uefi/src/helpers/mod.rs

@@ -13,16 +13,13 @@
 //! epoch.
 
 use crate::prelude::{Boot, SystemTable};
-use crate::Event;
 use crate::Result;
 use crate::StatusExt;
 use core::ffi::c_void;
 use core::ptr;
-use core::ptr::NonNull;
 use core::sync::atomic::{AtomicPtr, Ordering};
 #[doc(hidden)]
 pub use println::_print;
-use uefi_raw::table::boot::{EventType, Tpl};
 use uefi_raw::Status;
 
 #[cfg(feature = "global_allocator")]
@@ -73,10 +70,10 @@ fn system_table() -> SystemTable<Boot> {
 ///
 /// **PLEASE NOTE** that these helpers are meant for the pre exit boot service
 /// epoch.
-pub fn init(st: &mut SystemTable<Boot>) -> Result<Option<Event>> {
+pub fn init(st: &mut SystemTable<Boot>) -> Result<()> {
     if system_table_opt().is_some() {
         // Avoid double initialization.
-        return Status::SUCCESS.to_result_with_val(|| None);
+        return Status::SUCCESS.to_result_with_val(|| ());
     }
 
     // Setup the system table singleton
@@ -89,23 +86,12 @@ pub fn init(st: &mut SystemTable<Boot>) -> Result<Option<Event>> {
         logger::init(st);
 
         uefi::allocator::init(st);
-
-        // Schedule these tools to be disabled on exit from UEFI boot services
-        let boot_services = st.boot_services();
-        boot_services
-            .create_event(
-                EventType::SIGNAL_EXIT_BOOT_SERVICES,
-                Tpl::NOTIFY,
-                Some(exit_boot_services),
-                None,
-            )
-            .map(Some)
     }
+
+    Ok(())
 }
 
-/// Notify the utility library that boot services are not safe to call anymore
-/// As this is a callback, it must be `extern "efiapi"`.
-unsafe extern "efiapi" fn exit_boot_services(_e: Event, _ctx: Option<NonNull<c_void>>) {
+pub(crate) fn exit() {
     // DEBUG: The UEFI spec does not guarantee that this printout will work, as
     //        the services used by logging might already have been shut down.
     //        But it works on current OVMF, and can be used as a handy way to

uefi/src/table/system.rs

@@ -206,12 +206,10 @@ impl SystemTable<Boot> {
     /// live until the program ends. The lifetime of the memory map is therefore
     /// `'static`.
     ///
-    /// Once boot services are exited, the logger and allocator provided by
-    /// this crate can no longer be used. The logger should be disabled using
-    /// the [`Logger::disable`] method, and the allocator should be disabled by
-    /// calling [`allocator::exit_boot_services`]. Note that if the logger and
-    /// allocator were initialized with [`uefi_services::init`], they will be
-    /// disabled automatically when `exit_boot_services` is called.
+    /// Note that once the boot services are exited, associated loggers and
+    /// allocators can't use the boot services anymore. For the corresponding
+    /// abstractions provided by this crate, invoking this function will 
+    /// automatically disable them.
     ///
     /// # Errors
     ///
@@ -222,14 +220,13 @@ impl SystemTable<Boot> {
     /// All errors are treated as unrecoverable because the system is
     /// now in an undefined state. Rather than returning control to the
     /// caller, the system will be reset.
-    ///
-    /// [`allocator::exit_boot_services`]: crate::allocator::exit_boot_services
-    /// [`Logger::disable`]: crate::logger::Logger::disable
     #[must_use]
     pub fn exit_boot_services(
         self,
         memory_type: MemoryType,
     ) -> (SystemTable<Runtime>, MemoryMap<'static>) {
+        crate::helpers::exit();
+
         let boot_services = self.boot_services();
 
         // Reboot the device.