boot page table works

kernel/memory/mm.c

@@ -1,3 +1,4 @@
+#include "lib/print.h"
 #include "multiboot.h"
 
 #include <stddef.h>
@@ -5,10 +6,21 @@
 extern uint8_t __kernel_start;
 extern uint8_t __kernel_end;
 
+extern uint32_t page_directory[1024];
+extern void flush_tlb();
+extern void disable_pae();
+
 #define PAGE_SIZE 4096
 #define MAX_RAM   0xFFFFFFFF // 4GB
 #define BITMAP_SIZE ((MAX_RAM / PAGE_SIZE) / 8)
 
+#define PAGE_TABLES  0xFFC00000
+#define PAGE_DIRECTORY  0xFFFFF000
+
+#define PAGE_PRESENT  0x1
+#define PAGE_WRITABLE 0x2
+#define PAGE_USER     0x4
+
 static uint32_t max_address = 0;
 static uint32_t total_available_memory = 0;
 static uint8_t memory_bitmap[BITMAP_SIZE];
@@ -57,7 +69,7 @@ static void parse_multiboot_mmap(void* base, uint32_t limit) {
             uint32_t kernel_phys_start = (uint32_t)&__kernel_start - 0xC0000000;
             uint32_t kernel_phys_end   = (uint32_t)&__kernel_end - 0xC0000000;
             for (uint32_t addr = usable_start; addr < usable_end; addr += 4096) {
-                if (addr <= (uint32_t)&kernel_phys_end && addr >= (uint32_t)&kernel_phys_start) {
+                if (addr <= kernel_phys_end && addr >= kernel_phys_start) {
                     continue;
                 }
 
@@ -78,22 +90,7 @@ static void parse_multiboot_mmap(void* base, uint32_t limit) {
     }
 }
 
-void init_pmm(void* mmap_base, uint32_t mmap_limit) {
-    for (int i = 0; i < BITMAP_SIZE; i++) {
-        memory_bitmap[i] = 0xFF;
-    }
-
-    if (mmap_base != NULL && mmap_limit > 0) {
-        parse_multiboot_mmap(mmap_base, mmap_limit);
-    }
-}
-
-uint32_t total_free_memory() {
-    return total_available_memory;
-}
-
-// this returns the virtual address of the physical page allocated
-void* alloc_phys_page() {
+static void* p_alloc_frame() {
     for (uint32_t i = 0; i < BITMAP_SIZE; i++) {
         uint8_t b = memory_bitmap[i];
         if (b == 0xFF) {
@@ -104,7 +101,7 @@ void* alloc_phys_page() {
             if ((b & (1 << bit)) == 0) {
                 uint32_t page_addr = (i * 8 + bit) * PAGE_SIZE;
                 mark_used(page_addr);
-                return (void*)(page_addr + 0xC0000000);
+                return (void*)page_addr;
             }
         }
     }
@@ -112,19 +109,59 @@ void* alloc_phys_page() {
     return 0;
 }
 
-void free_phys_page(void* addr) {
+static void p_free_frame(void* addr) {
     mark_free((uint32_t)addr);
 }
 
-extern uint32_t page_directory[1024];
-extern void flush_tlb();
-extern void disable_pae();
+static void map_page(uint32_t vaddr, uint32_t paddr, uint32_t flags) {
+    uint32_t pde_entry = vaddr >> 22;
+    uint32_t pte_entry = (vaddr >> 12) & 0x3FF;
+
+    uint32_t* page_directory = (uint32_t*)PAGE_DIRECTORY;
+    if (page_directory[pde_entry] & PAGE_PRESENT == 0) {
+        uint32_t* new_table = (uint32_t*)p_alloc_frame();
+        page_directory[pde_entry] = (uint32_t)new_table | flags;
+    }
+}
+
+static void* p_alloc(uint32_t size_b, uint32_t vstart) {
+    uint32_t pages = (size_b + PAGE_SIZE - 1) / PAGE_SIZE;
+    
+    for (uint32_t i = 0; i < pages; i++) {
+        uint32_t vaddr = vstart + i * PAGE_SIZE;
+        uint32_t paddr = (uint32_t)p_alloc_frame();
+        
+        map_page(vaddr, paddr, PAGE_PRESENT | PAGE_WRITABLE);
+    }
+
+    return (void*)vstart;
+}
+
+void init_pmm(void* mmap_base, uint32_t mmap_limit) {
+    for (int i = 0; i < BITMAP_SIZE; i++) {
+        memory_bitmap[i] = 0xFF;
+    }
+
+    if (mmap_base != NULL && mmap_limit > 0) {
+        parse_multiboot_mmap(mmap_base, mmap_limit);
+    }
+}
+
 void init_page_tables() {
-    uint32_t* kernel_table = alloc_phys_page();
+    uint32_t* kernel_table = p_alloc_frame();
     for (int i = 0; i < 1024; i++) {
         kernel_table[i] = (i * PAGE_SIZE) | 0x3;
     }
-    uint32_t* phys_table = kernel_table - 0xC000000;
-    page_directory[768] = (uint32_t)(phys_table) | 0x3;
+    page_directory[768] = (uint32_t)(kernel_table) | 0x3;
+    page_directory[0] = 0;
+    disable_pae();
     flush_tlb();
+}
+
+void* init_kheap() {
+
+}
+
+uint32_t total_free_memory() {
+    return total_available_memory;
 }

kernel/memory/mm.h

@@ -8,11 +8,9 @@ typedef struct __attribute__((packed)) {
 } mem_page_t;
 
 void init_pmm(void* mmap_base, uint32_t mmap_limit);
+void init_page_tables();
+void* init_kheap();
+
 uint32_t total_free_memory();
 
-void* alloc_page();
-void free_page(void* addr);
-
-void init_page_tables();
-
 #endif 

kernel/memory/mm_stubs.S

@@ -7,5 +7,8 @@ flush_tlb:
      
 .global disable_pae
 disable_pae: 
+    mov %cr4, %edx
+    and $0xFFFFFFEF, %edx
+    mov %edx, %cr4
     ret