src/kernel/cpu.h

@@ -51,3 +51,12 @@ extern "C" uint32_t GetCR0();
 
 
 #define GET_PG_BIT(CONTROL_REGISTER_0) (CONTROL_REGISTER_0>>31)
+
+/*
+*       CONTROL_REGISTER_4 FUNCTIONS
+*/
+
+extern "C" uint32_t GetCR4();
+
+#define GET_PSE_BIT(CONTROL_REGISTER_4) (CONTROL_REGISTER_4&0x4)
+#define GET_PAE_BIT(CONTROL_REGISTER_4) (CONTROL_REGISTER_4&0x5)

src/kernel/cpu.s

@@ -11,6 +11,20 @@ GetCR0:
 	pop %ebp
 	ret
 
+.globl GetCR4
+GetCR4:
+	push %ebp
+	mov %esp, %ebp
+
+	xor %eax, %eax
+	mov %cr4, %eax 
+
+	mov %ebp, %esp 
+	pop %ebp
+	ret
+
+
+
 .globl GetEFLAGS
 GetEFLAGS:
 	push %ebp 

src/kernel/idt/idt.cpp

@@ -128,9 +128,24 @@ void irs_handler (registers regs) {
         case 14:
             // Page Fault Exception #PF
             printf("#PF\n");
-            printf("EIP: 0x%x\n", regs.eip);
+
+            printf("EIP: 0x%x\n", regs.eip); // Points to faulting instruction ???
             printf("EAX: 0x%x\n", regs.eax); 
-            printf("EBP: 0x%x\n", regs.ebp);
+            printf("EBP: 0x%x\n", regs.ebp); // Base pointer pointing to the bottom of the stack 
+ 
+
+            // Error code of 32 bits are on the stack
+            // CR2 register contains the 32-bit linear address that generated the exception
+            // See Intel Software Developers manual Volume 3A Part 1 page 236 for more info
+                   
+
+            /*
+                Check the error code to figure out what happened here
+            */
+
+
+            
+    
         break;
         
         case 16:

src/kernel/kernel.cpp

@@ -105,8 +105,9 @@ extern "C" void early_main(unsigned long magic, unsigned long addr){
 
 
 
-       // memAlloc.free_block((void*) memory);
+        //memAlloc.free_block((void*) memory);
-        InitializePaging();
+        //InitializePaging();
+        IdentityMap();
         Enable();
     }
     

src/kernel/memory/paging.cpp

@@ -1,19 +1,9 @@
 #include "paging.h"
 PageDirectoryEntry kernel_directory[MAX_DIRECTORY_ENTRIES]__attribute__((aligned(4096)));
-PageTableEntry first_page_table[1024]__attribute__((aligned(4096)));
-
-
-
-
-#define KERNEL_VRT_MEMORY_BEGIN 0xC0000000
-#define KERNEL_VRT_MEMORY_END   0xCFFFFFFF
-#define PAGE_SIZE  0xFA0;
-
-
-void InitializePaging()
-{
 
+PageTableEntry first_page_table[MAX_PAGE_TABLE_ENTRIES]__attribute__((aligned(4096)));
 
+void IdentityMap (){
         printf("\nInit paging\n");
     // The basics as explained by wiki.osdev.org
 
@@ -21,7 +11,7 @@ void InitializePaging()
     int i = 0;
     while ( i < 1024)
     {
-        kernel_directory[i] = 0x00000002;
+        kernel_directory[i] = 0x2;
         i++;
     }
 
@@ -31,12 +21,12 @@ void InitializePaging()
     for( j = 0;  j < 1024; j++ )
     {
         first_page_table[j] = (j * 0x1000) | 3 ;
-        /*
+        
-        Attributes: 
+        //Attributes: 
-        Supervisor Level ,
+        //Supervisor Level ,
-        read/write,
+        //read/write,
-        present,
+        //present,
-        */ 
+        
 
     }
 
@@ -45,39 +35,76 @@ void InitializePaging()
     kernel_directory[0] = ((unsigned int)first_page_table) | 3;
 
     printf("Init paging DONE\n");
-    // NOTE: Adjust this as needed 
+}
+
+void InitializePaging()
+{
+    /*
+        Initial kernel page directory
+         set all page tables to not present
+    */
+    for (int i = 0; i < MAX_DIRECTORY_ENTRIES; i++)
+    {
+        kernel_directory[i] = 0x2;
+    }
 
     // BIOS Address Identity mapping 
-    // Identity map the first 8MB ... Physical addresses 0x00000000 to 0x007A1200
+    // Identity map the first 8MiB ... Physical addresses 0x00000000 to 0x007A1200
-    /*
-    
     PHYSICAL_ADDRESS BIOSAddr = 0x00000000;
-    PHYSICAL_ADDRESS BIOSAddr_Max = 0x007A1200;
+    PHYSICAL_ADDRESS BIOSAddr_Max = 0x800000;
 
-    do
+    // How many PDE's do we need
+    uint8_t NUM_PDE = BIOSAddr_Max / (4 * 1024 * 1024);
+
+    printf("The first 8MiB require %d Page Directory Entries\n", NUM_PDE);
+/*
+    for( int i = 0; i < NUM_PDE; i++)
     {
-        Map( BIOSAddr, BIOSAddr, *kernel_directory);
+        // setup a page table 
-        BIOSAddr += PAGE_SIZE 
+        PageTableEntry pagetable[MAX_PAGE_TABLE_ENTRIES] = PhysicalMemory::allocate_block(); // TODO :: Physical memory manager functions should be available here.
-    } while(BIOSAddr <= BIOSAddr_Max);
 
-    // Identity map the kernel space 
+        for(int j = 0; j < MAX_PAGE_TABLE_ENTRIES; j++)
+        {
+            pagetable[j] = ( j  *  4096 ) | 3;
+        }
+
+        // add page table as page directory entry 
+        kernel_directory[i] =  ( (unsigned int) pagetable ) | 3;
+    }
+*/
+    //  map the kernel space 
     VIRTUAL_ADDRESS Vaddr = KERNEL_VRT_MEMORY_BEGIN;
     PHYSICAL_ADDRESS KernelAddr = kernel_begin;
+    PHYSICAL_ADDRESS KernelEndAddr = kernel_end;
 
-    do
+    uint32_t KernelSizeInBytes = (KernelEndAddr - KernelAddr);
+    printf("Kernel is 0x%x bytes\n", KernelSizeInBytes);
+    NUM_PDE = KernelSizeInBytes / (4 * 1024* 1024);
+    printf("Kernel requires %d Page Directory Entries\n", NUM_PDE);
+
+/*
+    for(int i = 0; i < NUM_PDE; i++)
     {
-        Map(KernelAddr, Vaddr , *kernel_directory);
+        PageTableEntry pageTable [MAX_PAGE_TABLE_ENTRIES] = PhysicalMemory::allocate_block();
+
+        for(int j = 0; j < MAX_PAGE_TABLE_ENTRIES; j++)
+        {
+            pageTable[j] = ( j * 4096) | 3; // NOTE: Check if page is actually supposed to be present
+        }
+
+        // TODO: Calculate Page Directory index 
+        
 
-        Vaddr += PAGE_SIZE;
-        KernelAddr += PAGE_SIZE 
 
     }
-    while(KernelAddr < kernel_end);
-
-
-    //TODO: Identity map VGA memory
     */
 
+    
+
+
+    // Identity map VGA memory
+    // Calc which PDE adn 
+    
 }
 
 
@@ -86,13 +113,11 @@ void AllocatePage(VIRTUAL_ADDRESS vaddr, PageDirectoryEntry& page_directory)
 
 }
 
-
 void FreePage(VIRTUAL_ADDRESS vaddr , PageDirectoryEntry& page_directory)
 {
 
 }
 
-
 void Map ( PHYSICAL_ADDRESS paddr, VIRTUAL_ADDRESS vaddr, PageDirectoryEntry& page_directory)
 {
 
@@ -106,7 +131,6 @@ void Unmap(VIRTUAL_ADDRESS vaddr, PageDirectoryEntry& page_directory)
     
 }
 
-
 void Enable()
 { 
 
@@ -127,10 +151,20 @@ void Enable()
 
 
     CR0 = GetCR0();
-    printf("PG bit = %d \n" , GET_PG_BIT(CR0) );
+    uint32_t CR4 = GetCR4();
+    printf("PG bit = %d\n" , GET_PG_BIT(CR0) );
+    printf("PAE bit = %d\n", GET_PAE_BIT(CR4));
 
+    if(GET_PAE_BIT(CR4) == 0){
+        printf("Using 32bit paging\n");
 
-    uint32_t EFLAGS = GetEFLAGS();
+        if(GET_PSE_BIT(CR4) == 0 ){
-
+            printf("Page size is 4KiB\n");
+        } else { 
+            printf("Page size is 4MiB\n");
+        }
+    }  else {
+        printf("Using some extended version for paging\n");
+    }
 
 }

src/kernel/memory/paging.definitions.h

@@ -6,8 +6,6 @@
     also 64 bit mode.
 */
 
-
-
 #define MAX_DIRECTORY_ENTRIES 1024
 #define MAX_PAGE_TABLE_ENTRIES 1024
 #define MAX_PAGES 1024
@@ -19,6 +17,9 @@
 #define PageTableEntry uint32_t
 
 
+#define KERNEL_VRT_MEMORY_BEGIN 0xC0000000
+#define KERNEL_VRT_MEMORY_END   0xCFFFFFFF
+#define PAGE_SIZE  4096;
 
 
 // NOTE: FIXME: I am fairly certain these masks are off by one!

src/kernel/memory/paging.h

@@ -7,6 +7,8 @@
 extern "C" void loadPageDirectory (uint32_t* addr );
 extern "C" void enablePaging();
 
+
+void IdentityMap();
 void InitializePaging();
 
 void Enable();