Add Hurl struct with map() method

src/hulk/hurl.d

@@ -5,6 +5,10 @@
  */
 module hulk.hurl;
 
+import hos.cpu;
+import hulk.hippo;
+import hos.memory;
+
 /** HULK virtual base address. */
 enum ulong HULK_VIRTUAL_BASE_ADDRESS = 0xFFFF_8000_0000_0000u;
 
@@ -13,3 +17,108 @@ enum ulong HULK_VIRTUAL_STACK_TOP_ADDRESS = 0xFFFF_A000_0000_0000u;
 
 /** HULK virtual framebuffer address. */
 enum ulong HULK_VIRTUAL_FRAMEBUFFER_ADDRESS = 0xFFFF_A000_0000_0000u;
+
+/** Page table entry attributes. @{ */
+enum ulong MAP_PRESENT = 0x1u;
+enum ulong MAP_WRITABLE = 0x2u;
+enum ulong MAP_USER = 0x4u;
+enum ulong MAP_WRITE_THROUGH = 0x8u;
+enum ulong MAP_DISABLE_CACHE = 0x10u;
+enum ulong MAP_HUGE_PAGE = 0x20u;
+enum ulong MAP_GLOBAL = 0x40u;
+enum ulong MAP_NO_EXECUTE = 0x8000_0000_0000_0000u;
+/** @} */
+
+struct Hurl
+{
+    private struct PageTableEntry
+    {
+        private ulong m_entry;
+
+        this(ulong address, ulong flags)
+        {
+            m_entry = address | flags;
+        }
+
+        this(void * address, ulong flags)
+        {
+            m_entry = cast(ulong)address | flags;
+        }
+
+        public @property bool present()
+        {
+            return (m_entry & MAP_PRESENT) != 0u;
+        }
+
+        public PageTable * follow()
+        {
+            return cast(PageTable *)(m_entry & 0x7FFF_FFFF_FFFF_F000u);
+        }
+    }
+
+    private struct PageTable
+    {
+        public PageTableEntry opIndex(ulong address, ulong level)
+        {
+            PageTableEntry * entries = cast(PageTableEntry *)&this;
+            return entries[pt_index(address, level)];
+        }
+
+        public PageTableEntry opIndex(void * address, ulong level)
+        {
+            return opIndex(cast(ulong)address, level);
+        }
+
+        public PageTableEntry opIndexAssign(PageTableEntry pte, ulong address, ulong level)
+        {
+            PageTableEntry * entries = cast(PageTableEntry *)&this;
+            entries[pt_index(address, level)] = pte;
+            return pte;
+        }
+
+        public PageTableEntry opIndexAssign(PageTableEntry pte, void * address, ulong level)
+        {
+            return opIndexAssign(pte, cast(ulong)address, level);
+        }
+
+        private ulong pt_index(ulong address, ulong level)
+        {
+            return (address >> (39u - (9u * level))) & 0x1FFu;
+        }
+    }
+
+    private static __gshared PageTable * m_pt_base;
+
+    public static void initialize()
+    {
+        m_pt_base = cast(PageTable *)read_cr3();
+    }
+
+    public static void map(ulong virtual, ulong physical, ulong flags)
+    {
+        size_t last_level = ((flags & MAP_HUGE_PAGE) != 0u) ? 2u : 3u;
+        PageTable * pt = m_pt_base;
+        for (size_t level = 0; level <= last_level; level++)
+        {
+            if (level < last_level)
+            {
+                PageTableEntry entry = (*pt)[virtual, level];
+                if (entry.present)
+                {
+                    pt = entry.follow();
+                }
+                else
+                {
+                    PageTable * next_pt = cast(PageTable *)hippo.allocate_page();
+                    memset32(next_pt, 0, 4096u / 4u);
+                    (*pt)[virtual, level] = PageTableEntry(next_pt, MAP_WRITABLE | MAP_PRESENT);
+                    pt = next_pt;
+                }
+            }
+            else
+            {
+                (*pt)[virtual, level] = PageTableEntry(physical, flags | MAP_PRESENT);
+            }
+        }
+    }
+}