A update

lib/mm/paging.c

@@ -0,0 +1,82 @@
+#include <string.h>
+#include <stdio.h>
+
+#include <mm/paging.h>
+#include <mm/pmm.h>
+
+#define PAGE_DIRECTORY_ENTRIES 1024
+#define PAGE_TABLE_ENTRIES     1024
+#define PAGE_SIZE              4096
+
+typedef uint32_t page_directory_entry_t;
+typedef uint32_t page_table_entry_t;
+
+static page_directory_entry_t* page_directory = (page_directory_entry_t*)0x9C000; /* Must be page-aligned */
+static page_table_entry_t* page_tables[PAGE_DIRECTORY_ENTRIES];
+
+extern void _enable_paging_asm(void);
+
+void paging_init(void)
+{
+  /* Allocate and clear the page directory */
+  page_directory = (uint32_t*)alloc_page();
+  memset(page_directory, 0, 4096);
+
+  /* Allocate and set up the first identity-mapped page table (0–4MB) */
+  uint32_t* first_table = (uint32_t*)alloc_page();
+  memset(first_table, 0, 4096);
+  for (uint32_t i = 0; i < 1024; i++)
+  {
+    first_table[i] = (i * 0x1000) | 3; /* Present | RW */
+  }
+  page_directory[0] = ((uint32_t)first_table) | 3;
+
+  /* --- Map 4MB heap at 0xC0000000 --- */
+  uint32_t* heap_table = (uint32_t*)alloc_page();
+  memset(heap_table, 0, 4096);
+
+  for (uint32_t i = 0; i < 1024; i++) /* 256 pages = 1MB */
+  {
+    uint32_t phys = (uint32_t)alloc_page();
+    if (phys == 0)
+    {
+      printf("Out of physical memory during heap mapping!\n");
+      while (1);
+    }
+    heap_table[i] = phys | 3; /* Present | RW */
+  }
+
+  /* 0xC0000000 >> 22 == 768 */
+  page_directory[768] = ((uint32_t)heap_table) | 3;
+
+  // Load page directory
+  asm volatile ("mov %0, %%cr3" : : "r"(page_directory));
+
+  /* Enable paging */
+  _enable_paging_asm();
+}
+
+void map_page(void* phys_addr, void* virt_addr)
+{
+  uint32_t pd_index = ((uint32_t)virt_addr >> 22) & 0x3FF;
+  uint32_t pt_index = ((uint32_t)virt_addr >> 12) & 0x3FF;
+
+  /* Allocate page table if necessary */
+  if (!(page_directory[pd_index] & 1))
+  {
+    void* pt_phys = alloc_page();
+    page_tables[pd_index] = (page_table_entry_t*)((uint32_t)pt_phys + 0xC0000000); /* Map it higher */
+    
+    for (int i = 0; i < PAGE_TABLE_ENTRIES; i++)
+    {
+      page_tables[pd_index][i] = 0x00000002; /* Not present */
+    }
+    
+    page_directory[pd_index] = ((uint32_t)pt_phys) | 0x3; /* Present, R/W */
+  }
+
+  page_table_entry_t* page_table = (page_table_entry_t*)((page_directory[pd_index] & 0xFFFFF000) | 0xC0000000);
+  page_table[pt_index] = ((uint32_t)phys_addr & 0xFFFFF000) | 0x3; /* Present, R/W */
+
+  asm volatile ("invlpg (%0)" :: "r" (virt_addr) : "memory");
+}