From 1aace858da49c9688965d904a5f758cecc07094b Mon Sep 17 00:00:00 2001
From: josh <josh@5b3e749e-e535-0410-8002-a9bb6afbdfca>
Date: Mon, 6 Jul 2009 21:48:04 +0000
Subject: [PATCH] Moved page_directory from an allocated object to a pointer to
 a run-time allocated page of RAM

git-svn-id: svn://anubis/hos/trunk@42 5b3e749e-e535-0410-8002-a9bb6afbdfca
---
 kernel/mm/mm.cc | 33 +++++++++++++++++++++++----------
 kernel/mm/mm.h  |  5 +----
 2 files changed, 24 insertions(+), 14 deletions(-)

diff --git a/kernel/mm/mm.cc b/kernel/mm/mm.cc
index ba15fec..c8a088a 100644
--- a/kernel/mm/mm.cc
+++ b/kernel/mm/mm.cc
@@ -8,8 +8,7 @@
 
 static bool mm_use_virtual_offset;
 
-pagedirectory_t page_directory __attribute__ ((aligned (4096)));
-
+static pagedirectory_entry_t * page_directory;
 static mm_mem_range_t mm_mmap_entries[MM_MAX_MMAP_ENTRIES];
 static int mm_mmap_num_entries = 0;
 static int mm_num_free_pages = 0;
@@ -108,10 +107,18 @@ void mm_bootstrap()
         k_early_panic("Not enough free pages of RAM!");
     }
 
+    /* ok, now mm_page_alloc() should be functional */
+
+    /* allocate the page directory */
+    u32_t page_directory_phys = mm_page_alloc();
+    page_directory = (pagedirectory_entry_t *) page_directory_phys;
+    pagedirectory_entry_t * page_dir_virt =
+        (pagedirectory_entry_t *) (page_directory_phys + KERNEL_OFFSET);
+
     /* Clear the page directory */
     for (unsigned int i = 0; i < NUM_PAGETABLE_ENTRIES; i++)
     {
-        page_directory[i] = 0;
+        page_dir_virt[i] = 0;
     }
 
     /*
@@ -135,7 +142,7 @@ void mm_bootstrap()
     }
 
     /* set the page directory base register */
-    set_cr3(&page_directory);
+    set_cr3(page_directory);
 
     mm_use_virtual_offset = false;
 }
@@ -149,7 +156,13 @@ int mm_map(u32_t virtual_address, u32_t physical_address,
 {
     u32_t directory_index = (virtual_address >> 22) & 0x3FF;
     u32_t table_index = (virtual_address >> 12) & 0x3FF;
-    if (page_directory[directory_index] == 0)
+    pagedirectory_entry_t * page_dir = page_directory;
+    if (mm_use_virtual_offset)
+    {
+        page_dir = (pagedirectory_entry_t *)((u32_t)page_dir + KERNEL_OFFSET);
+    }
+
+    if (page_dir[directory_index] == 0)
     {
         /* allocate a new page table */
         u32_t page_table_address = mm_page_alloc();
@@ -157,12 +170,12 @@ int mm_map(u32_t virtual_address, u32_t physical_address,
         {
             return 0;
         }
-        page_directory[directory_index] = page_table_address
-                                        | 0x1 << 2  /* PTs can be user mode */
-                                        | 0x1 << 1  /* writable */
-                                        | 0x1;      /* present */
+        page_dir[directory_index] = page_table_address
+                                  | 0x1 << 2  /* PTs can be user mode */
+                                  | 0x1 << 1  /* writable */
+                                  | 0x1;      /* present */
     }
-    u32_t page_table_address = page_directory[directory_index] & PAGE_HIGH_MASK;
+    u32_t page_table_address = page_dir[directory_index] & PAGE_HIGH_MASK;
 
     u32_t * page_table = (u32_t *) page_table_address;
     if (mm_use_virtual_offset)
diff --git a/kernel/mm/mm.h b/kernel/mm/mm.h
index a7ef217..daa0eda 100644
--- a/kernel/mm/mm.h
+++ b/kernel/mm/mm.h
@@ -10,10 +10,7 @@ typedef u32_t pagedirectory_entry_t;
 
 #define NUM_PAGETABLE_ENTRIES (PAGE_SIZE / sizeof(pagedirectory_entry_t))
 
-typedef pagedirectory_entry_t
-    pagedirectory_t[NUM_PAGETABLE_ENTRIES];
-
-extern pagedirectory_t page_directory;
+typedef pagedirectory_entry_t pagedirectory_t[NUM_PAGETABLE_ENTRIES];
 
 typedef struct
 {