physical_mm: Set the first 4MiB to unusable

... consequently, move from using dynamic memory to static memory for
the page table and directory

3 files changed, 12 insertions, 21 deletions

diff --git a/kernel/include/common.h b/kernel/include/common.h
index 7f7f50f..7c5270a 100644
--- a/kernel/include/common.h
+++ b/kernel/include/common.h
@@ -21,6 +21,7 @@
 
 #define ALWAYS_INLINE __attribute__((always_inline)) inline
 #define PACKED __attribute__((packed))
+#define ALIGNED(x) __attribute__((aligned(x)))
 
 #define KiB 1024
 #define MiB (KiB * KiB)
diff --git a/kernel/mm/physical_mm/physical_mm.c b/kernel/mm/physical_mm/physical_mm.c
index e93593d..81656ed 100644
--- a/kernel/mm/physical_mm/physical_mm.c
+++ b/kernel/mm/physical_mm/physical_mm.c
@@ -22,17 +22,14 @@
 
 /* TODO: Stack based allocation? */
 
-#include <stdatomic.h>
-#include <stdbool.h>
-#include <stdint.h>
-
+#include <kernel/halt.h>
+#include <kernel/spinlock.h>
 #include <libk/stdio.h>
-
 #include <mm/memory_map.h>
 #include <mm/physical_mm.h>
-
-#include <kernel/halt.h>
-#include <kernel/spinlock.h>
+#include <stdatomic.h>
+#include <stdbool.h>
+#include <stdint.h>
 
 extern uint32_t kernel_start;
 extern uint32_t kernel_end;
diff --git a/kernel/mm/virtual_mm/virtual_mm.c b/kernel/mm/virtual_mm/virtual_mm.c
index 4bdb4ab..3043686 100644
--- a/kernel/mm/virtual_mm/virtual_mm.c
+++ b/kernel/mm/virtual_mm/virtual_mm.c
@@ -16,20 +16,22 @@
  * along with this program.  If not, see <http://www.gnu.org/licenses/>.
  */
 
-#include <stdint.h>
-
 #include <kernel/halt.h>
-
 #include <libk/stdio.h>
-
 #include <mm/physical_mm.h>
 #include <mm/virtual_mm.h>
+#include <stdint.h>
 
 extern uint32_t kernel_start;
 extern uint32_t kernel_end;
 
 uint32_t *current_page_directory = 0;
 
+/* Kernel's page directory */
+uint32_t page_directory[1024] ALIGNED(4096);
+/* Page table for the first 4 MiB */
+uint32_t table[1024] ALIGNED(4096);
+
 ALWAYS_INLINE void
 virtual_mm_load_page_directory(uint32_t *page_directory)
 {
@@ -59,10 +61,6 @@ virtual_mm_enable_paging(void)
 void
 virtual_mm_initialize(void)
 {
-  uint32_t *table = physical_mm_allocate_block();
-  if (!table)
-    ASSERT_NOT_REACHED();
-
   for (uint32_t i = 0; i < 1024; i++)
     table[i] = 0;
 
@@ -71,11 +69,6 @@ virtual_mm_initialize(void)
   for (uint32_t i = 0; i < 1024; i++)
     table[i] = PTE_FRAME(i) | PTE_PRESENT(1) | PTE_WRITABLE(1);
 
-  uint32_t *page_directory = physical_mm_allocate_block();
-  if (!page_directory)
-    ASSERT_NOT_REACHED();
-  printk("debug", "Page directory is at: 0x%x", page_directory);
-
   for (uint32_t i = 0; i < 1024; i++)
     page_directory[i] = 0;