1 files changed, 141 insertions, 0 deletions
diff --git a/library/std/src/sys/uefi/helpers.rs b/library/std/src/sys/uefi/helpers.rs
new file mode 100644
index 000000000..126661bfc
--- /dev/null
+++ b/library/std/src/sys/uefi/helpers.rs
@@ -0,0 +1,141 @@
+//! Contains most of the shared UEFI specific stuff. Some of this might be moved to `std::os::uefi`
+//! if needed but no point in adding extra public API when there is not Std support for UEFI in the
+//! first place
+//!
+//! Some Nomenclature
+//! * Protocol:
+//! - Protocols serve to enable communication between separately built modules, including drivers.
+//! - Every protocol has a GUID associated with it. The GUID serves as the name for the protocol.
+//! - Protocols are produced and consumed.
+//! - More information about protocols can be found [here](https://edk2-docs.gitbook.io/edk-ii-uefi-driver-writer-s-guide/3_foundation/36_protocols_and_handles)
+
+use r_efi::efi::{self, Guid};
+
+use crate::mem::{size_of, MaybeUninit};
+use crate::os::uefi;
+use crate::ptr::NonNull;
+use crate::{
+    io::{self, const_io_error},
+    os::uefi::env::boot_services,
+};
+
+const BOOT_SERVICES_UNAVAILABLE: io::Error =
+    const_io_error!(io::ErrorKind::Other, "Boot Services are no longer available");
+
+/// Locate Handles with a particular Protocol GUID
+/// Implemented using `EFI_BOOT_SERVICES.LocateHandles()`
+///
+/// Returns an array of [Handles](r_efi::efi::Handle) that support a specified protocol.
+pub(crate) fn locate_handles(mut guid: Guid) -> io::Result<Vec<NonNull<crate::ffi::c_void>>> {
+    fn inner(
+        guid: &mut Guid,
+        boot_services: NonNull<r_efi::efi::BootServices>,
+        buf_size: &mut usize,
+        buf: *mut r_efi::efi::Handle,
+    ) -> io::Result<()> {
+        let r = unsafe {
+            ((*boot_services.as_ptr()).locate_handle)(
+                r_efi::efi::BY_PROTOCOL,
+                guid,
+                crate::ptr::null_mut(),
+                buf_size,
+                buf,
+            )
+        };
+
+        if r.is_error() { Err(crate::io::Error::from_raw_os_error(r.as_usize())) } else { Ok(()) }
+    }
+
+    let boot_services = boot_services().ok_or(BOOT_SERVICES_UNAVAILABLE)?.cast();
+    let mut buf_len = 0usize;
+
+    // This should always fail since the size of buffer is 0. This call should update the buf_len
+    // variable with the required buffer length
+    match inner(&mut guid, boot_services, &mut buf_len, crate::ptr::null_mut()) {
+        Ok(()) => unreachable!(),
+        Err(e) => match e.kind() {
+            io::ErrorKind::FileTooLarge => {}
+            _ => return Err(e),
+        },
+    }
+
+    // The returned buf_len is in bytes
+    assert_eq!(buf_len % size_of::<r_efi::efi::Handle>(), 0);
+    let num_of_handles = buf_len / size_of::<r_efi::efi::Handle>();
+    let mut buf: Vec<r_efi::efi::Handle> = Vec::with_capacity(num_of_handles);
+    match inner(&mut guid, boot_services, &mut buf_len, buf.as_mut_ptr()) {
+        Ok(()) => {
+            // This is safe because the call will succeed only if buf_len >= required length.
+            // Also, on success, the `buf_len` is updated with the size of bufferv (in bytes) written
+            unsafe { buf.set_len(num_of_handles) };
+            Ok(buf.into_iter().filter_map(|x| NonNull::new(x)).collect())
+        }
+        Err(e) => Err(e),
+    }
+}
+
+/// Open Protocol on a handle.
+/// Internally just a call to `EFI_BOOT_SERVICES.OpenProtocol()`.
+///
+/// Queries a handle to determine if it supports a specified protocol. If the protocol is
+/// supported by the handle, it opens the protocol on behalf of the calling agent.
+pub(crate) fn open_protocol<T>(
+    handle: NonNull<crate::ffi::c_void>,
+    mut protocol_guid: Guid,
+) -> io::Result<NonNull<T>> {
+    let boot_services: NonNull<efi::BootServices> =
+        boot_services().ok_or(BOOT_SERVICES_UNAVAILABLE)?.cast();
+    let system_handle = uefi::env::image_handle();
+    let mut protocol: MaybeUninit<*mut T> = MaybeUninit::uninit();
+
+    let r = unsafe {
+        ((*boot_services.as_ptr()).open_protocol)(
+            handle.as_ptr(),
+            &mut protocol_guid,
+            protocol.as_mut_ptr().cast(),
+            system_handle.as_ptr(),
+            crate::ptr::null_mut(),
+            r_efi::system::OPEN_PROTOCOL_GET_PROTOCOL,
+        )
+    };
+
+    if r.is_error() {
+        Err(crate::io::Error::from_raw_os_error(r.as_usize()))
+    } else {
+        NonNull::new(unsafe { protocol.assume_init() })
+            .ok_or(const_io_error!(io::ErrorKind::Other, "null protocol"))
+    }
+}
+
+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_io_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(()) }
+}