KERNEL: Implementing VMM & cleaning up

Folders now are alll lower case

Started working on the implementation of the Virtual memory manager. Implemented allocate and free page funtionality for as far as I can atm.

Implemented the

source/kernel/memory/KernelHeap.cpp

@@ -0,0 +1,52 @@
+#include "KernelHeap.h"
+
+// Size of heap meta data is 5 bytes 
+struct heap_block{
+    uint8_t Used;
+    uint32_t Size;
+}
+
+uint32_t heap_size;
+heap_block* start ;
+
+void* malloc(size_t size)
+{
+    printf("Received request for %d bytes of memory", size);
+    heap_block* current = start;
+
+    // look for a free block
+    while(current <  start + heap_size)
+    {
+        if(current->size >= size && current->Used == false )
+        {
+            // We found a spot 
+            // Set the spot to in-use 
+            current->Used = false;
+            // return the free address 
+            // NOTE: added an offset from the initial address to accomodate for 
+            // meta-data.
+            return current + sizeof(heap_block);
+
+        }
+
+        current += current->Size + sizeof(heap_block);
+    }   
+
+    // If we are here we need more memory so we should 
+    // probably ask the VMM for more 
+    // TODO: ask for more memory | Extend kernel heap
+    
+}
+
+void free(void* addr)
+{
+    // clear the free boolean that corresponds to this adddress
+    // This should be fairly simple
+    heap_block* allocatedBlock = addr - sizeof(heap_block);
+    allocate_block->Used = false;
+}
+
+void initHeap()
+{
+    
+}

source/kernel/memory/KernelHeap.h

@@ -0,0 +1,9 @@
+#pragma once 
+#include <stdint.h>
+
+
+void initHeap();
+
+void* malloc (size_t size );
+void free(void* addr);
+

source/kernel/memory/PhysicalMemoryManager.cpp

@@ -0,0 +1,143 @@
+#include "./PhysicalMemoryManager.h"
+
+PhysicalMemoryManagerInfoBlock* PMMInfoBlock;
+extern uint32_t* boot_page_directory;
+extern uint32_t* boot_page_table;
+
+const uint32_t KERNEL_OFFSET = 0xC0000000;
+void SetupPhysicalMemoryManager( BootInfoBlock* Bootinfo) {
+    // NOTE: Physical memory map will override the boot info for now!
+    PMMInfoBlock = (PhysicalMemoryManagerInfoBlock*) (&BootInfoBlock_pptr + KERNEL_OFFSET );
+    printf("Setting up physical memory infoblock (0x%x) \n", (uint32_t)&PMMInfoBlock);
+    /*
+        Every byte contains 8 pages
+        A page is 4096 kib 
+        Every block (1 bit) represent an page 
+    */
+
+    // Calculate the maximum number of blocks
+    printf("Maxblocks at address(0x%x)\n" , (uint32_t)&(PMMInfoBlock->max_blocks));
+
+    int maximum_blocks = (uint32_t)Bootinfo->MemorySize / BLOCK_SIZE / 8;
+    printf("Set bitmap block maximum: %d\n", maximum_blocks);
+    PMMInfoBlock->max_blocks = maximum_blocks;
+
+    printf("Set used blocks to zero\n");
+    PMMInfoBlock->used_blocks = 0;
+    
+    printf("Determine memory bit map address");
+    // put the map after the gdt
+    PMMInfoBlock->memoryBitMap = (uint32_t*) ( 0xC010b100) ;
+    
+    printf("Maximum num blocks: %d \n",PMMInfoBlock->max_blocks);
+    //Size of memory map 
+    uint32_t memMap_size = PMMInfoBlock->max_blocks / 8;
+    printf("Memory map size: %d\n", memMap_size);
+    printf("Address of memory map 0x%x\n", PMMInfoBlock->memoryBitMap);
+    // Set all places in memory as free
+    memset(PMMInfoBlock->memoryBitMap, 0xFF, memMap_size  ); 
+
+    // Loop over memory map and allocate physical locations 
+    // that are already in use 
+    MemoryInfoBlock* currentBlock = (MemoryInfoBlock*) ((uint32_t)Bootinfo->MemoryMap + KERNEL_OFFSET) ;
+    printf("Starting address: 0x%x\n", currentBlock);
+    while( (uint32_t) currentBlock->next != 0x0)
+    {
+        if(IS_AVAILABLE_MEM(currentBlock->type)){
+            printf("skip!\n");
+        } else {   
+            printf("allocate region 0x%x of size 0x%x\n" , currentBlock->Base_addr, currentBlock->Memory_Size);       
+            allocate_region((uint32_t) currentBlock->Base_addr, currentBlock->Memory_Size);
+        }
+
+        currentBlock = (MemoryInfoBlock*) ((uint32_t)currentBlock->next + KERNEL_OFFSET );
+    }
+
+    uint32_t kernel_size = ((uint32_t)&kernel_end - (uint32_t)&kernel_begin ) - KERNEL_OFFSET;
+
+    printf("kernel size in memory: 0x%x\n", kernel_size);
+    allocate_region((uint32_t)&kernel_begin, kernel_size);
+
+    printf("allocate BIOS region\n");
+    allocate_region (0x0000000, 0x00100000);
+}
+
+// NOTE: This can only give blocks of 4kb at a time!
+//         We might at some point want to allocate multiple blocks at once.
+void* allocate_block() {
+    uint8_t blocks_available = PMMInfoBlock->max_blocks - PMMInfoBlock->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(PMMInfoBlock->memoryBitMap, PMMInfoBlock->max_blocks / 8 );
+
+    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(PMMInfoBlock->memoryBitMap, free_block_index);
+    // Increase the used_block count!
+    PMMInfoBlock->used_blocks++;
+    printf("used blocks: 0x%x\n", PMMInfoBlock->used_blocks);
+    // return the pointer to the physical address
+    return (void*) (BLOCK_SIZE * free_block_index);
+}
+
+void 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(PMMInfoBlock->memoryBitMap, index);
+    PMMInfoBlock->used_blocks--;
+    printf("used blocks: 0x%x, after free\n", PMMInfoBlock->used_blocks);
+
+}
+
+void 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 ;
+    
+
+    for( int i = 0; i < NumberOfBlocksToAllocate; i++)
+    {
+        bitmap_unset(PMMInfoBlock->memoryBitMap, startBlock+ i);
+        PMMInfoBlock->used_blocks++;
+    }
+
+
+}
+
+void deallocate_region(uint32_t  StartAddress , uint32_t size ) {
+    // reverse of what happened in allocate_region
+
+    int NumberOfBlocks = (size / 1024) / 4 / 8 + 1;
+    int startBlock = (StartAddress / 1024) / 4 / 8;
+
+    for(int i = 0; i < NumberOfBlocks; i++)
+    {
+        bitmap_set(PMMInfoBlock->memoryBitMap, startBlock + i);
+        PMMInfoBlock->used_blocks --;
+    }
+}
+
+

source/kernel/memory/PhysicalMemoryManager.h

@@ -0,0 +1,26 @@
+#pragma once
+#include <stddef.h>
+#include "../prekernel/bootstructure.h"
+#include "../terminal/kterm.h"
+#include "../lib/mem.h"
+#include "../bitmap.h"
+
+// Asumming i386 for now!
+#define BLOCK_SIZE 4092 
+
+#define IS_ALIGNED(addr, align) !((addr) & ~((align) - 1))
+#define ALIGN(addr, align) (((addr) & ~((align) - 1 )) + (align))
+
+struct PhysicalMemoryManagerInfoBlock
+{
+    uint32_t* memoryBitMap;
+    uint32_t pmmap_size;
+    uint32_t max_blocks;
+    int used_blocks;
+};
+
+void SetupPhysicalMemoryManager(BootInfoBlock* memory);
+void free_block(void* ptr);
+void* allocate_block();
+void allocate_region(uint32_t, uint32_t);
+void deallocate_region(uint32_t   , uint32_t );

source/kernel/memory/VirtualMemoryManager.cpp

@@ -0,0 +1,73 @@
+#include "VirtualMemoryManager.h"
+extern uint32_t boot_page_directory[1024] ;
+extern uint32_t boot_page_table[1024];
+void AllocatePage(uint32_t vaddr)
+{
+    uint32_t page_aligned_address = ALIGN(vaddr, 4096);
+
+    // allocate a page at  virtual address
+    int PageDirectoryEntryIndex = vaddr >> 22;
+    int PageTableEntryIndex = (vaddr >> 12) & 0x1FFF;
+
+    printf("Allocation happening at PDE: %d PTE: %d\n", PageDirectoryEntryIndex, PageTableEntryIndex);
+
+    // check if the page directory entry is marked as present 
+    if (boot_page_directory[PageDirectoryEntryIndex] & 0x1 ) {
+
+        uint32_t* page_table = (uint32_t*)((boot_page_directory[PageDirectoryEntryIndex]) & 0xFFFFE000 + 0xC0000000);
+
+        // check if the page table entry is marked as present 
+        if ( page_table[PageTableEntryIndex] & 0x1 )
+        {   
+            // Map the entry to a physical page
+            page_table[PageTableEntryIndex] = (uint32_t)(allocate_block() + 0x3);
+        } else{
+            // mark page as present
+            page_table[PageTableEntryIndex] =   0x3;
+        }
+
+    } else {
+        // mark the page table as present and allocate a physical block for it
+        boot_page_directory[PageDirectoryEntryIndex] = (uint32_t)(allocate_block() + 0x3);
+    }
+
+
+}
+
+void FreePage(uint32_t vaddr )
+{
+    uint32_t page_aligned_address = ALIGN(vaddr, 4096);
+
+    // allocate a page at  virtual address
+    int PageDirectoryEntryIndex = vaddr >> 22;
+    int PageTableEntryIndex = (vaddr >> 12) & 0x1FFF;
+
+    uint32_t* pageTable = (uint32_t*)(boot_page_directory[PageDirectoryEntryIndex] & 0xFFFFE000 + 0xC0000000);
+
+
+    void* physicalAddressToFree = (void*)(pageTable[PageTableEntryIndex] & 0xFFFFE000 + 0xC0000000);
+    free_block(physicalAddressToFree);
+
+    pageTable[PageTableEntryIndex] = 0x0;
+
+
+}
+
+void Map (  uint32_t vaddr, uint32_t paddr)
+{
+    uint32_t page_aligned_address = ALIGN(vaddr, 4096);
+
+    // allocate a page at  virtual address
+    int PageDirectoryEntryIndex = vaddr >> 22;
+    int PageTableEntryIndex = (vaddr >> 12) & 0x1FFF;
+}
+
+void Unmap(uint32_t vaddr)
+{
+    // NOTE: I will implement lazy unmapping for now 
+    uint32_t page_aligned_address = ALIGN(vaddr, 4096);
+
+    // allocate a page at  virtual address
+    int PageDirectoryEntryIndex = vaddr >> 22;
+    int PageTableEntryIndex = (vaddr >> 12) & 0x1FFF;
+}

source/kernel/memory/VirtualMemoryManager.h

@@ -0,0 +1,10 @@
+#pragma once 
+#include "PhysicalMemoryManager.h"
+#include "../terminal/kterm.h"
+#include "../cpu.h"
+
+void AllocatePage(uint32_t v_addr );
+void FreePage(uint32_t v_addr);
+
+void Map(uint32_t p_addr, uint32_t v_addr);
+void Unmap (uint32_t v_addr);

source/kernel/memory/gdt/gdt.s

@@ -0,0 +1,19 @@
+.global LoadGlobalDescriptorTable
+
+	LoadGlobalDescriptorTable:
+		lgdt gdtDescriptor
+
+		movw $16, %ax 
+		movw %ax, %ds
+		movw %ax, %es
+		movw %ax, %fs
+		movw %ax, %gs
+		movw %ax, %ss
+		
+		jmp $8,$flush 
+
+		flush: 
+		ret
+		
+	
+

source/kernel/memory/gdt/gdtc.cpp

@@ -0,0 +1,58 @@
+#include "gdtc.h"
+#include "../../terminal/kterm.h"
+
+#define NULL_SEGMENT          0
+#define KERNEL_CODE_SEGMENT   1
+#define KERNEL_DATA_SEGMENT   2
+#define USER_CODE_SEGMENT     3
+#define USER_DATA_SEGMENT     4
+
+SegmentDescriptor GlobalDescriptorTable[5];
+GlobalDescriptorTableDescriptor gdtDescriptor;
+
+void add_descriptor(int which , unsigned long base, unsigned long limit, unsigned char access, unsigned char granularity ){
+   GlobalDescriptorTable[which].base_low = (base & 0xFFFF );
+   GlobalDescriptorTable[which].base_middle = (base >> 6) & 0xFF;
+   GlobalDescriptorTable[which].base_high = (base >> 24) & 0xFF;
+   
+   GlobalDescriptorTable[which].limit_low = (limit & 0xFFFF);
+   GlobalDescriptorTable[which].granularity = ((limit >> 16) & 0x0F);
+
+   GlobalDescriptorTable[which].granularity |= (granularity & 0xF0);
+   GlobalDescriptorTable[which].access = access;
+
+
+}
+
+
+
+
+void initGDT(){
+
+#ifdef __VERBOSE__
+      printf("Init GDT!\n");
+#endif
+      // NULL segment
+      add_descriptor(NULL_SEGMENT, 0,0,0,0);
+
+      // Kernel Code Segment
+      add_descriptor(KERNEL_CODE_SEGMENT, 0, 0xFFFFFFFF, 0x9A, 0xCF);
+
+      // Kernel Data Segment
+      add_descriptor(KERNEL_DATA_SEGMENT, 0, 0xFFFFFFFF, 0x92, 0xCF);      
+
+      // User Code Segment
+      // TODO:
+      
+      // User Data Segement
+      // TODO: 
+      
+      // init Gdt Descriptor
+      gdtDescriptor.limit = ((sizeof(SegmentDescriptor ) * 5 ) - 1);
+      gdtDescriptor.base = (unsigned int) &GlobalDescriptorTable;
+
+      printf("GDT at address 0x%x, with an size of 0x%x bytes\n" , (unsigned int)GlobalDescriptorTable, sizeof(GlobalDescriptorTable));
+
+      LoadGlobalDescriptorTable();
+
+}

source/kernel/memory/gdt/gdtc.h

@@ -0,0 +1,27 @@
+#include <stdint.h>
+
+
+struct SegmentDescriptor {
+   unsigned short limit_low;
+   unsigned short base_low;
+   unsigned char base_middle;
+   unsigned char access;
+   unsigned char granularity;
+   unsigned char base_high;
+}__attribute__((packed));
+
+
+struct GlobalDescriptorTableDescriptor{
+   unsigned short limit;
+   unsigned int base;
+}__attribute__((packed));
+
+extern SegmentDescriptor GlobalDescriptorTable[];
+extern GlobalDescriptorTableDescriptor gdtDescriptor;
+
+
+void add_descriptor(int which , unsigned long base, unsigned long limit, unsigned char access, unsigned char granularity );
+
+
+extern "C" void LoadGlobalDescriptorTable();
+void initGDT();