src folder -> source folder; makes merging with dev a bit easier.

source/kernel/memory/PageDirectory.cpp

@@ -0,0 +1,43 @@
+#include "PageDirectory.h"
+
+void PageDirectory::enable()
+{
+
+
+    // https://wiki.osdev.org/Setting_Up_Paging
+    //set each entry to not present
+    // int i;
+    // for(i = 0; i < 1024; i++)
+    // {
+    //     // This sets the following flags to the pages:
+    //     //   Supervisor: Only kernel-mode can access them
+    //     //   Write Enabled: It can be both read from and written to
+    //     //   Not Present: The page table is not present
+    //     this->page_directory[i] = 0x00000002;
+    // }
+
+    // // holds the physical address where we want to start mapping these pages to.
+    // // in this case, we want to map these pages to the very beginning of memory.
+
+    // //we will fill all 1024 entries in the table, mapping 4 megabytes
+    // for(unsigned int i = 0; i < 1024; i++)
+    // {
+    //     // As the address is page aligned, it will always leave 12 bits zeroed.
+    //     // Those bits are used by the attributes ;)
+    //     first_page_table[i] = (i * 0x1000) | 3; // attributes: supervisor level, read/write, present.
+    // }
+
+    // // attributes: supervisor level, read/write, present
+    // this->page_directory[0] = ((unsigned int)first_page_table) | 3;
+
+    printf("Enable Paging!\n");
+
+    loadPageDirectory(this->page_directory);
+    enablePaging();
+}
+
+
+void PageDirectory::MapPhysicalToVirtualAddress ( address_t PAddress , address_t VAddress, uint32_t size  )
+{
+
+}

source/kernel/memory/PageDirectory.h

@@ -0,0 +1,31 @@
+#pragma once 
+#include <stdint.h>
+#include "./memory.h"
+#include "./../tty/kterm.h"
+#define KB 1024
+
+
+typedef uintptr_t address_t;
+
+static const int MAX_PAGES =  1024 * KB; // 4GB , 4kB/page
+static volatile address_t pmem_stack[MAX_PAGES];
+static volatile address_t pmem_stack_top = MAX_PAGES; // top down allocation
+
+extern "C" void loadPageDirectory (uint32_t* addr );
+extern "C" void enablePaging();
+
+struct page_directory_entry {};
+struct page_table_entry{};
+
+
+
+class PageDirectory {
+    public:
+    void enable ();
+    void MapPhysicalToVirtualAddress ( address_t PAddress , address_t VAddress, uint32_t size  );
+
+    private:
+    uint32_t page_directory[1024] __attribute__((aligned(4096))); // align on 4 kiloByte pages
+    uint32_t first_page_table[1024] __attribute__((aligned(4096))); // align on 4 kiloByte pages
+
+};

source/kernel/memory/memory.cpp

@@ -0,0 +1,142 @@
+#include "./memory.h"
+uint32_t* memoryBitMap;
+/*
+
+*/
+void PhysicalMemory::setup( MemoryInfo* memory) {
+
+    // calculate the maximum number of blocks
+    max_blocks = KB_TO_BLOCKS(memory->TotalMemory);
+
+    used_blocks = 0;
+
+    memoryBitMap = (uint32_t*) 0x00a00000;
+
+
+    printf("Maximum Number of blocks: 0x%x, Number of bytes for memMap: 0x%x\n", max_blocks , (max_blocks/8));
+
+    //Size of memory map 
+    uint32_t memMap_size = (max_blocks / 8 ) ; 
+    
+    printf("Memory Map size:  0x%x\n", memMap_size );
+    printf("size of int in bytes: 0x%x \n" , sizeof(int));
+
+    // Set all places in memory as free
+    memset(memoryBitMap, 0xFF, memMap_size  );
+}
+
+// NOTE: this can only give blocks of 4kb at a time!
+void* PhysicalMemory::allocate_block() {
+    uint8_t blocks_available = max_blocks - used_blocks;
+    // Are there any blocks available?
+    if( blocks_available <= 0)
+    {
+        printf("No blocks available. Blocks Delta: 0x%x\n", blocks_available);
+        return 0;
+    }
+
+    // Find 1 free block somewhere
+    int free_block_index = bitmap_first_unset(memoryBitMap, (max_blocks /8) /*memMap Size*/ );
+
+
+    
+    if(free_block_index == -1)
+    {
+        printf("Could not find a good block!\n");
+        // Could not find a block
+        return (void*)0xFFFF;
+    }
+
+    if(free_block_index == 0)
+        printf("Somethings wrong!!!\n");
+
+    // Set the block to be used!
+    bitmap_unset(memoryBitMap, free_block_index);
+    // Increase the used_block count!
+    used_blocks++;
+    printf("used blocks: 0x%x\n", used_blocks);
+    // return the pointer to the physical address
+    return (void*) (BLOCK_SIZE * free_block_index);
+}
+
+
+void PhysicalMemory::free_block(void* p) {
+    // If it is a null pointer we don't need to do anything.
+    if(p==0) {
+        return;
+    }
+    // calculate the index into the bitmap
+    int index  = ((uint32_t) p) / BLOCK_SIZE;
+    
+    // set the block to be free
+    bitmap_set(memoryBitMap, index);
+    used_blocks--;
+    printf("used blocks: 0x%x, after free\n", used_blocks);
+
+}
+
+
+
+void PhysicalMemory::allocate_region(uint32_t startAddress, uint32_t size) {
+    // every bit should be 4KiB 
+    // every byte is 8*4KiB = 32KiB
+    
+    int NumberOfBlocksToAllocate = ( size / 1024) / 4  / 8 + 1;
+    int startBlock = (startAddress / 1024) / 4 / 8 ;
+    
+   // printf("NumberOfBlocksToAllocate: 0x%x\n", NumberOfBlocksToAllocate);
+    //printf( "start block: 0x%x\n" , startBlock);
+    for( int i = 0; i < NumberOfBlocksToAllocate; i++)
+    {
+
+        //printf("ALLOCATE BLOCK: 0x%x\n" , startBlock + i );
+        bitmap_unset(memoryBitMap, startBlock+ i);
+        used_blocks++;
+    }
+
+
+}
+void PhysicalMemory::deallocate_region(uint32_t  StartAddress , uint32_t size ) {
+    // NOT IMPLEMENTED YET
+}
+
+
+void mapMultibootMemoryMap( MemoryInfo* memInfo , multiboot_info_t *mbt) {
+    printf("mmap_addr = 0x%x, mmap_length = 0x%x\n",
+    (unsigned) mbt->mmap_addr, (unsigned) mbt->mmap_length);
+    multiboot_memory_map_t *mmap = (multiboot_memory_map_t*) mbt->mmap_addr;
+
+    for (;  (unsigned long) mmap < mbt->mmap_addr + mbt->mmap_length;  mmap = (multiboot_memory_map_t *) ((unsigned long) mmap + mmap->size + sizeof(mmap->size))){
+
+            if ( mmap->type == MULTIBOOT_MEMORY_AVAILABLE){
+        
+                memInfo->TotalMemory +=  mmap->len;   
+            } else {
+                memInfo->ReservedMemory += mmap->len;
+            }
+            
+            print_Multiboot_memory_Map(mmap);
+            
+        }
+    
+}
+
+
+/**
+ * @brief Debug Verbose functions
+ * 
+ * @param mmap 
+ */
+
+void print_Multiboot_memory_Map(multiboot_memory_map_t* mmap) {
+    printf(
+        "size = 0x%x, base_addr = 0x%x%08x, length = 0x%x%08x, type = 0x%x\n",
+        (unsigned) mmap->size,
+        (unsigned) (mmap->addr >> 32),
+        (unsigned) (mmap->addr & 0xffffffff),
+        (unsigned) (mmap->len >> 32),
+        (unsigned) (mmap->len & 0xffffffff),
+        (unsigned) mmap->type
+    );
+}
+

source/kernel/memory/memory.h

@@ -0,0 +1,48 @@
+#pragma once
+#include <stdint.h>
+#include <stddef.h>
+
+#include "memoryinfo.h"
+#include "../bootloader/multiboot.h"
+#include "../tty/kterm.h"
+#include "../../libc/include/mem.h"
+#include "../kstructures/bitmap.h"
+
+#define BLOCK_SIZE 4092
+#define BLOCKS_PER_WORD 32 // A word is 16 bit in x86 machines according to my google search results!
+
+#define KB_TO_BLOCKS(x) (x  / BLOCK_SIZE)
+#define IS_ALIGNED(addr, align) !((addr) & ~((align) - 1))
+#define ALIGN(addr, align) (((addr) & ~((align) - 1 )) + (align))
+
+extern uint32_t kernel_begin;
+extern uint32_t kernel_end;
+
+void initialise_available_regions(uint32_t memoryMapAddr, uint32_t memoryMapLastAddr, uint32_t* memoryBitMap, int* used_blocks);
+
+extern uint32_t* memoryBitMap;
+
+class PhysicalMemory
+{
+    public:
+        void setup(MemoryInfo* memory);
+        void destroy();
+        void free_block(void* ptr);
+        void* allocate_block();
+        void allocate_region(uint32_t, uint32_t);
+        void deallocate_region(uint32_t   , uint32_t );
+    
+    private:
+        size_t pmmap_size;
+        size_t max_blocks;
+        int used_blocks;
+};
+
+void mapMultibootMemoryMap( MemoryInfo* memInfo , multiboot_info_t *mbt);
+
+/**
+ * @brief Debug Verbose Functions
+ * 
+ * @param mmap 
+ */
+void print_Multiboot_memory_Map(multiboot_memory_map_t* mmap);

source/kernel/memory/memoryinfo.h

@@ -0,0 +1,20 @@
+#pragma once
+#include <stdint.h>
+#include <stddef.h>
+
+struct MemoryArea{
+    void* StartAddress;
+    size_t Size;
+    unsigned int type;
+    MemoryArea* Next;
+
+}__attribute__((packed));
+
+struct MemoryInfo {
+    uint32_t TotalMemory;
+    uint32_t ReservedMemory;
+    MemoryArea* MemoryRegionList;
+}__attribute__((packed));
+
+
+

source/kernel/memory/paging.s

@@ -0,0 +1,20 @@
+.globl enablePaging
+enablePaging:
+	push %ebp
+	mov %esp, %ebp
+	mov %cr0, %eax
+	or $0x80000000, %eax
+	mov %eax, %cr0
+	mov %ebp, %esp
+	pop %ebp
+	ret
+
+.globl loadPageDirectory
+loadPageDirectory:
+	push %ebp
+	mov %esp, %ebp
+	mov 8(%esp), %eax
+	mov %eax, %cr3
+	mov %ebp, %esp
+	pop %ebp
+	ret