uefi-raw: fix layout of HII keyboard layout types

The spec defines EFI_HII_KEYBOARD_LAYOUT and EFI_KEY_DESCRIPTOR with
1-byte packing (UEFI 2.11, 34.8.10; EDK2 declares them inside
#pragma pack(1)).

uefi-raw/CHANGELOG.md

@@ -8,6 +8,9 @@
 - **Breaking**: The USB descriptor types in `protocol::usb` are now packed to
   match their layout in the USB specification. `ConfigDescriptor` and
   `EndpointDescriptor` previously had a too-large `size_of`.
+- **Breaking**: `HiiKeyboardLayout` and `KeyDescriptor` are now packed to
+  match the layout mandated by the UEFI specification. Previously, all
+  `HiiKeyboardLayout` fields after `layout_length` were at wrong offsets.
 
 ## Removed
 

uefi-raw/src/protocol/hii/database.rs

@@ -4,10 +4,11 @@
 
 use super::{HiiHandle, HiiPackageHeader, HiiPackageListHeader, KeyDescriptor};
 use crate::{Guid, Handle, Status, guid, newtype_enum};
+use core::mem::offset_of;
 
 /// EFI_HII_KEYBOARD_LAYOUT
 #[derive(Debug)]
-#[repr(C)]
+#[repr(C, packed)]
 pub struct HiiKeyboardLayout {
     pub layout_length: u16,
     pub guid: Guid,
@@ -16,6 +17,14 @@ pub struct HiiKeyboardLayout {
     pub descriptors: [KeyDescriptor; 0],
 }
 
+// Compile-time ABI check.
+const _: () = {
+    assert!(offset_of!(HiiKeyboardLayout, guid) == 2);
+    assert!(offset_of!(HiiKeyboardLayout, layout_descriptor_string_offset) == 18);
+    assert!(offset_of!(HiiKeyboardLayout, descriptor_count) == 22);
+    assert!(offset_of!(HiiKeyboardLayout, descriptors) == 23);
+};
+
 newtype_enum! {
     /// EFI_HII_DATABASE_NOTIFY_TYPE
     pub enum HiiDatabaseNotifyType: usize => {

uefi-raw/src/protocol/hii/mod.rs

@@ -208,8 +208,8 @@ newtype_enum! {
 }
 
 /// EFI_KEY_DESCRIPTOR
-#[derive(Debug)]
-#[repr(C)]
+#[derive(Clone, Copy, Debug)]
+#[repr(C, packed)]
 pub struct KeyDescriptor {
     pub key: Key,
     pub unicode: Char16,
@@ -219,3 +219,9 @@ pub struct KeyDescriptor {
     pub modifier: u16,
     pub affected_attribute: u16,
 }
+
+// Compile-time ABI check.
+const _: () = {
+    assert!(size_of::<KeyDescriptor>() == 16);
+    assert!(align_of::<KeyDescriptor>() == 1);
+};