Set alignment of XSDT table pointers to 4 instead of 8

src/hulk/acpi.d

@@ -28,8 +28,8 @@ struct Acpi
     static struct Xsdt
     {
         XsdtHeader header;
-        uint _pad;
-        ulong[0] tables;
+        /* Table pointers are not ulong-aligned! They begin at offset 36. */
+        align(4) ulong[1] tables;
     }
 
     static struct MadtHeader
@@ -73,16 +73,16 @@ struct Acpi
             ulong address = xsdt.tables[i];
             Hurl.identity_map_range(address, 4u, 0u);
             uint signature = *cast(const(uint) *)address;
-            if (signature == APIC_SIGNATURE)
-            {
-                parse_apic_table(address);
-            }
             Klog.writefln("Found ACPI table %08x (%c%c%c%c)",
                     signature,
                     signature & 0xFFu,
                     (signature >> 8u) & 0xFFu,
                     (signature >> 16u) & 0xFFu,
                     (signature >> 24u) & 0xFFu);
+            if (signature == APIC_SIGNATURE)
+            {
+                parse_apic_table(address);
+            }
         }
     }
 
@@ -100,8 +100,8 @@ struct Acpi
             if (madt_entry.type == 5u)
             {
                 /* Found a 64-bit Local APIC Address Override entry. */
-                memcpy(cast(void *)&apic_address, cast(const(void) *)madt_entry + 4u, 8u);
                 Klog.writefln("Found 64-bit APIC address: 0x%x", apic_address);
+                memcpy(cast(void *)&apic_address, cast(const(void) *)madt_entry + 4u, 8u);
             }
         }
     }

src/hulk/pagetable.d

@@ -183,3 +183,11 @@ struct PageTable
     }
 }
 static assert(PageTable.sizeof == 4096u);
+
+/**
+ * Get the base address of the page containing the given address.
+ */
+T page_address(T)(T address)
+{
+    return cast(T)(cast(ulong)address & ~(PAGE_SIZE - 1u));
+}