KERNEL: First Kernel heap implementation

source/kernel/memory/KernelHeap.cpp

@@ -1,4 +1,5 @@
 #include "KernelHeap.h"
+#include "VirtualMemoryManager.h"
 
 // Size of heap meta data is 5 bytes 
 struct heap_block{
@@ -11,7 +12,7 @@ heap_block* start ;
 
 void* malloc(size_t size)
 {
-    printf("Received request for %d bytes of memory", size);
+    printf("Received request for %d bytes of memory\n", size);
     heap_block* current = start;
 
     // look for a free block
@@ -20,8 +21,21 @@ void* malloc(size_t size)
         if(current->Size >= size && current->Used == false )
         {
             // We found a spot 
+            printf("Block found!\n");
+
             // Set the spot to in-use 
-            current->Used = false;
+            current->Used = true;
+
+
+            // split the block 
+            printf("Split block.\n");
+            uint32_t oldSize = current->Size;
+            current->Size = size;
+
+            heap_block* new_block = current + sizeof(heap_block) + current->Size;
+            new_block->Size = oldSize - ( sizeof(heap_block) + size);
+            new_block->Used = false;
+
             // return the free address 
             // NOTE: added an offset from the initial address to accomodate for 
             // meta-data.
@@ -36,6 +50,7 @@ void* malloc(size_t size)
     // probably ask the VMM for more 
     // TODO: ask for more memory | Extend kernel heap
     
+    printf("ERROR: OUT OF HEAP MEMORY CONDITION IS NOT IMPLEMENTED. HEAP NEEDS TO BE EXTENDED!\n");
 }
 
 void free(void* addr)
@@ -48,6 +63,26 @@ void free(void* addr)
 
 void initHeap()
 {
-    // NOTE: What to do now??
-    
+    // put the start of our kernel heap 1 page after the kernel_end address
+    // Lets calculate the address 
+    printf("FIND SUITABLE HEAP_ADDRESS\n");
+    uint32_t alligned_k_end = (uint32_t) &kernel_end + ((uint32_t)&kernel_end % BLOCK_SIZE == 0 ? 4096 : 0);
+    uint32_t HEAP_ADDRESS = (uint32_t) alligned_k_end + 4096;
+    printf("HEAP_ADDRESS: 0x%x\n", HEAP_ADDRESS);
+
+    // NOTE: we can't check if the mapping has failed or not here!
+    AllocatePage(HEAP_ADDRESS);
+    start = (heap_block*) HEAP_ADDRESS;
+    heap_size = 4096;
+
+    printf("Clear heap\n");
+    // Clear the heap 
+    printf("set at 0x%x %d bytes to zero\n", start , heap_size);
+    memset((void*)start, 0x00,  heap_size /4);
+
+    printf("Init first heap block\n");
+    // initialzie 
+    start->Size = heap_size - sizeof(heap_block);
+    start->Used = false;
+
 }

source/kernel/memory/PhysicalMemoryManager.cpp

@@ -1,5 +1,4 @@
 #include "./PhysicalMemoryManager.h"
-#define BLOCK_SIZE 4092 
 #define IS_ALIGNED(addr, align) !((addr) & ~((align) - 1))
 #define ALIGN(addr, align) (((addr) & ~((align) - 1 )) + (align))
 
@@ -28,7 +27,7 @@ void SetupPhysicalMemoryManager(uint32_t mapAddress, uint32_t memorySize )
     printf("Bitmap size: %d bytes\n",bitmap_size);
 
     // Set blocks used to zero
-    used_blocks = 0;
+    used_blocks = max_blocks;
     
     // set the address of the memory bitmap
     memoryBitMap = (uint32_t*) mapAddress;

source/kernel/memory/PhysicalMemoryManager.h

@@ -5,6 +5,7 @@
 #include "../lib/mem.h"
 #include "../bitmap.h"
 
+#define BLOCK_SIZE 4092 
 
 
 void SetupPhysicalMemoryManager(uint32_t mapAddress, uint32_t memorySize);

source/kernel/memory/VirtualMemoryManager.cpp

@@ -1,9 +1,16 @@
 #include "VirtualMemoryManager.h"
 #define ALIGN(addr, align) (((addr) & ~((align) - 1 )) + (align))
+
 extern uint32_t boot_page_directory[1024] ;
 extern uint32_t boot_page_table[1024];
 
 
+void flush_cr3(){
+    asm volatile("movl %cr3, %ecx;"
+	             "movl %ecx, %cr3");
+}
+
+
 void AllocatePage(uint32_t vaddr)
 {
     uint32_t page_aligned_address = ALIGN(vaddr, 4096);
@@ -15,23 +22,31 @@ void AllocatePage(uint32_t vaddr)
     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);
+    if (boot_page_directory[PageDirectoryEntryIndex] & 0x1 ) 
+    {
+        printf("Directory entry is marked as present\n");
+        uint32_t* page_table = (uint32_t*)((boot_page_directory[PageDirectoryEntryIndex]) & 0xFFFFE000) ;
+        page_table = (uint32_t*) ((uint32_t)page_table + 0xC0000000); // Add kernel offset
+        printf("Page table address: 0x%x\n", (uint32_t)page_table);
 
         // check if the page table entry is marked as present 
         if ( page_table[PageTableEntryIndex] & 0x1 )
         {   
+            printf("page already present!\n");
+            return;
+        } else{
+            printf("Mapping a physical page.\n");
             // Map the entry to a physical page
             page_table[PageTableEntryIndex] = (uint32_t)(allocate_block() + 0x3);
-        } else{
-            // mark page as present
-            page_table[PageTableEntryIndex] =   0x3;
+            flush_cr3();
         }
 
     } else {
+        printf("Mapping a new page directory entry with a page table\n");
         // mark the page table as present and allocate a physical block for it
         boot_page_directory[PageDirectoryEntryIndex] = (uint32_t)(allocate_block() + 0x3);
+        flush_cr3();
+   
     }
 
 
@@ -56,7 +71,8 @@ void FreePage(uint32_t vaddr )
 
 }
 
-void Map (  uint32_t vaddr, uint32_t paddr)
+
+void Immediate_Map (  uint32_t vaddr, uint32_t paddr)
 {
     uint32_t page_aligned_address = ALIGN(vaddr, 4096);
 
@@ -66,7 +82,7 @@ void Map (  uint32_t vaddr, uint32_t paddr)
 
 }
 
-void Unmap(uint32_t vaddr)
+void Immediate_Unmap(uint32_t vaddr)
 {
     // NOTE: I will implement lazy unmapping for now 
     uint32_t page_aligned_address = ALIGN(vaddr, 4096);

source/kernel/memory/VirtualMemoryManager.h

@@ -1,10 +1,16 @@
 #pragma once 
-#include "PhysicalMemoryManager.h"
 #include "../terminal/kterm.h"
 #include "../cpu.h"
+#include "PhysicalMemoryManager.h"
+
+
+void SetupVMM();
 
 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);
+void Immediate_Map(uint32_t p_addr, uint32_t v_addr);
+void Immediate_Unmap (uint32_t v_addr);
+
+// void Demand_map(uint32_t p_addr, uint32_t v_addr);
+// void Demand_Unmap (uint32_t v_addr);