added mm_map() to map addresses and mm_page_alloc() to allocate physical pages

git-svn-id: svn://anubis/hos/trunk@35 5b3e749e-e535-0410-8002-a9bb6afbdfca

kernel/mm/mm.cc

@@ -6,6 +6,8 @@
 
 #define MM_MAX_MMAP_ENTRIES 64
 
+static bool mm_use_virtual_offset;
+
 extern "C" {
 
 pagedirectory_t page_directory __attribute__ ((aligned (4096)));
@@ -43,6 +45,7 @@ void mm_record_mmap_entry(mb_mmap_t * mmap)
 void mm_bootstrap()
 {
     u32_t max_ram_address = KERNEL_PHYSICAL_ADDRESS + KERNEL_SIZE - 1;
+    mm_use_virtual_offset = true;
 
     if (mm_mmap_num_entries < 1)
     {
@@ -78,9 +81,10 @@ void mm_bootstrap()
         u32_t * last_page = NULL;
         while (base_address < address_limit)
         {
-            /* check to make sure the RAM page isn't overlapping the kernel */
+            /* check to make sure the RAM page is ok */
-            if (   base_address + PAGE_SIZE <= KERNEL_PHYSICAL_ADDRESS
+            if (   base_address > 0     /* don't map address 0 */
-                && base_address >= KERNEL_PHYSICAL_ADDRESS + KERNEL_SIZE )
+                && ( base_address + PAGE_SIZE <= KERNEL_PHYSICAL_ADDRESS
+                  || base_address >= KERNEL_PHYSICAL_ADDRESS + KERNEL_SIZE ) )
             {
                 /* we found a page to add to the free list */
                 u32_t * page_virtual_address =
@@ -101,11 +105,83 @@ void mm_bootstrap()
         }
     }
 
+    if (mm_num_free_pages < 10)
+    {
+        k_early_panic("Not enough free pages of RAM!");
+    }
+
     /* Clear the page directory */
     for (unsigned int i = 0; i < NUM_PAGETABLE_ENTRIES; i++)
     {
         page_directory[i] = 0;
     }
+
+    /* now map all of RAM into the virtual address space
+     * starting at address 0x0
+     */
+    for (u32_t page_base = 0;
+         page_base < max_ram_address;
+         page_base += PAGE_SIZE)
+    {
+        mm_map(page_base, page_base, 0, 1);
+    }
+
+    mm_use_virtual_offset = false;
 }
 
 } /* extern "C" */
+
+int mm_map(u32_t virtual_address, u32_t physical_address,
+           u32_t user_mode, u32_t writable)
+{
+    u32_t directory_index = (virtual_address >> 22) & 0x3FF;
+    u32_t table_index = (virtual_address >> 12) & 0x3FF;
+    if (page_directory[directory_index] == 0)
+    {
+        /* allocate a new page table */
+        u32_t page_table_address = mm_page_alloc();
+        if (page_table_address == 0)
+        {
+            return 1;
+        }
+        page_directory[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 = (u32_t *) page_table_address;
+    if (mm_use_virtual_offset)
+    {
+        page_table = (u32_t *)((u32_t)page_table + (u32_t)KERNEL_OFFSET);
+    }
+
+    page_table[table_index] = (physical_address & PAGE_HIGH_MASK)
+                            | (user_mode & 0x1) << 2
+                            | (writable & 0x1) << 1
+                            | 0x1;      /* present */
+
+    return 0;
+}
+
+/**************************************************************************
+ * Returns the physical base address of a page in RAM                     *
+ * or 0 if no pages were available                                        *
+ *************************************************************************/
+u32_t mm_page_alloc()
+{
+    if (mm_free_page_ptr == NULL)
+    {
+        return 0;
+    }
+    u32_t * page_ptr = mm_free_page_ptr;
+    if (mm_use_virtual_offset)
+    {
+        page_ptr = (u32_t *) ((u32_t)page_ptr + (u32_t)KERNEL_OFFSET);
+    }
+    u32_t page_address = (u32_t) mm_free_page_ptr;
+    mm_free_page_ptr = (u32_t *) *page_ptr;
+    mm_num_free_pages--;
+    return page_address;
+}

kernel/mm/mm.h

@@ -32,5 +32,10 @@ void mm_bootstrap();
 }
 #endif
 
+int mm_map(u32_t virtual_address, u32_t physical_address,
+           u32_t user_mode, u32_t writable);
+
+u32_t mm_page_alloc();
+
 #endif