uefi: allocator: test page-aligned allocation

We can look at the TRACE messages of `cargo xtask run` to
verify that the shortcut is taken.

Author: phip1611

uefi-test-runner/src/boot/memory.rs

@@ -58,9 +58,12 @@ mod bootservices {
 /// Tests that use [`uefi::allocator::Allocator`], which is configured as the
 /// global allocator.
 mod global {
+    use alloc::boxed::Box;
+    use uefi_raw::table::boot::PAGE_SIZE;
+
     /// Simple test to ensure our custom allocator works with the `alloc` crate.
     pub fn alloc_vec() {
-        info!("Allocating a vector through the `alloc` crate");
+        info!("Allocating a vector using the global allocator");
 
         #[allow(clippy::useless_vec)]
         let mut values = vec![-5, 16, 23, 4, 0];
@@ -71,17 +74,27 @@ mod global {
     }
 
     /// Simple test to ensure our custom allocator works with correct alignment.
+    #[allow(dead_code)] // Ignore warning due to field not being read.
     pub fn alloc_alignment() {
-        info!("Allocating a structure with alignment to 0x100");
-
-        #[repr(align(0x100))]
-        struct Block(
-            // Ignore warning due to field not being read.
-            #[allow(dead_code)] [u8; 0x100],
-        );
+        {
+            info!("Allocating a structure with alignment of 0x100 using the global allocator");
+            #[repr(align(0x100))]
+            struct Block([u8; 0x100]);
 
-        let value = vec![Block([1; 0x100])];
-        assert_eq!(value.as_ptr() as usize % 0x100, 0, "Wrong alignment");
+            let value = vec![Block([1; 0x100])];
+            assert_eq!(value.as_ptr() as usize % 0x100, 0, "Wrong alignment");
+        }
+        {
+            info!("Allocating a memory page ({PAGE_SIZE}) using the global allocator");
+            #[repr(align(4096))]
+            struct Page([u8; PAGE_SIZE]);
+            let value = Box::new(Page([0; PAGE_SIZE]));
+            assert_eq!(
+                value.0.as_ptr().align_offset(PAGE_SIZE),
+                0,
+                "Wrong alignment"
+            );
+        }
     }
 }