uefi: Add OwnedEvent abstraction

- Events are going to become quite important for Networking, so needed
  owned abstractions.
- Switch to OwnedEvent abstraction for Exit boot services event.

Signed-off-by: Ayush Singh <[email protected]>

Author: Ayush1325

library/std/src/sys/pal/uefi/helpers.rs

@@ -120,39 +120,6 @@ pub(crate) fn open_protocol<T>(
     }
 }
 
-pub(crate) fn create_event(
-    signal: u32,
-    tpl: efi::Tpl,
-    handler: Option<efi::EventNotify>,
-    context: *mut crate::ffi::c_void,
-) -> io::Result<NonNull<crate::ffi::c_void>> {
-    let boot_services: NonNull<efi::BootServices> =
-        boot_services().ok_or(BOOT_SERVICES_UNAVAILABLE)?.cast();
-    let mut event: r_efi::efi::Event = crate::ptr::null_mut();
-    let r = unsafe {
-        let create_event = (*boot_services.as_ptr()).create_event;
-        (create_event)(signal, tpl, handler, context, &mut event)
-    };
-    if r.is_error() {
-        Err(crate::io::Error::from_raw_os_error(r.as_usize()))
-    } else {
-        NonNull::new(event).ok_or(const_error!(io::ErrorKind::Other, "null protocol"))
-    }
-}
-
-/// # SAFETY
-/// - The supplied event must be valid
-pub(crate) unsafe fn close_event(evt: NonNull<crate::ffi::c_void>) -> io::Result<()> {
-    let boot_services: NonNull<efi::BootServices> =
-        boot_services().ok_or(BOOT_SERVICES_UNAVAILABLE)?.cast();
-    let r = unsafe {
-        let close_event = (*boot_services.as_ptr()).close_event;
-        (close_event)(evt.as_ptr())
-    };
-
-    if r.is_error() { Err(crate::io::Error::from_raw_os_error(r.as_usize())) } else { Ok(()) }
-}
-
 /// Gets the Protocol for current system handle.
 ///
 /// Note: Some protocols need to be manually freed. It is the caller's responsibility to do so.
@@ -559,3 +526,56 @@ impl Drop for ServiceProtocol {
         }
     }
 }
+
+#[repr(transparent)]
+pub(crate) struct OwnedEvent(NonNull<crate::ffi::c_void>);
+
+impl OwnedEvent {
+    pub(crate) fn new(
+        signal: u32,
+        tpl: efi::Tpl,
+        handler: Option<efi::EventNotify>,
+        context: Option<NonNull<crate::ffi::c_void>>,
+    ) -> io::Result<Self> {
+        let boot_services: NonNull<efi::BootServices> =
+            boot_services().ok_or(BOOT_SERVICES_UNAVAILABLE)?.cast();
+        let mut event: r_efi::efi::Event = crate::ptr::null_mut();
+        let context = context.map(NonNull::as_ptr).unwrap_or(crate::ptr::null_mut());
+
+        let r = unsafe {
+            let create_event = (*boot_services.as_ptr()).create_event;
+            (create_event)(signal, tpl, handler, context, &mut event)
+        };
+
+        if r.is_error() {
+            Err(crate::io::Error::from_raw_os_error(r.as_usize()))
+        } else {
+            NonNull::new(event)
+                .ok_or(const_error!(io::ErrorKind::Other, "failed to create event"))
+                .map(Self)
+        }
+    }
+
+    pub(crate) fn into_raw(self) -> *mut crate::ffi::c_void {
+        let r = self.0.as_ptr();
+        crate::mem::forget(self);
+        r
+    }
+
+    /// SAFETY: Assumes that ptr is a non-null valid UEFI event
+    pub(crate) unsafe fn from_raw(ptr: *mut crate::ffi::c_void) -> Self {
+        Self(unsafe { NonNull::new_unchecked(ptr) })
+    }
+}
+
+impl Drop for OwnedEvent {
+    fn drop(&mut self) {
+        if let Some(boot_services) = boot_services() {
+            let bt: NonNull<r_efi::efi::BootServices> = boot_services.cast();
+            unsafe {
+                let close_event = (*bt.as_ptr()).close_event;
+                (close_event)(self.0.as_ptr())
+            };
+        }
+    }
+}

library/std/src/sys/pal/uefi/mod.rs

@@ -49,17 +49,17 @@ pub(crate) unsafe fn init(argc: isize, argv: *const *const u8, _sigpipe: u8) {
     unsafe { uefi::env::init_globals(image_handle, system_table) };
 
     // Register exit boot services handler
-    match helpers::create_event(
+    match helpers::OwnedEvent::new(
         r_efi::efi::EVT_SIGNAL_EXIT_BOOT_SERVICES,
         r_efi::efi::TPL_NOTIFY,
         Some(exit_boot_service_handler),
-        crate::ptr::null_mut(),
+        None,
     ) {
         Ok(x) => {
             if EXIT_BOOT_SERVICE_EVENT
                 .compare_exchange(
                     crate::ptr::null_mut(),
-                    x.as_ptr(),
+                    x.into_raw(),
                     Ordering::Release,
                     Ordering::Acquire,
                 )
@@ -79,7 +79,7 @@ pub unsafe fn cleanup() {
     if let Some(exit_boot_service_event) =
         NonNull::new(EXIT_BOOT_SERVICE_EVENT.swap(crate::ptr::null_mut(), Ordering::Acquire))
     {
-        let _ = unsafe { helpers::close_event(exit_boot_service_event) };
+        let _ = unsafe { helpers::OwnedEvent::from_raw(exit_boot_service_event.as_ptr()) };
     }
 }
 
@@ -145,7 +145,7 @@ pub fn abort_internal() -> ! {
     if let Some(exit_boot_service_event) =
         NonNull::new(EXIT_BOOT_SERVICE_EVENT.load(Ordering::Acquire))
     {
-        let _ = unsafe { helpers::close_event(exit_boot_service_event) };
+        let _ = unsafe { helpers::OwnedEvent::from_raw(exit_boot_service_event.as_ptr()) };
     }
 
     if let (Some(boot_services), Some(handle)) =