Implementation of simplistic physical memory manager

Makefile

@@ -5,7 +5,7 @@ CC = ${HOME}/opt/cross/bin/i686-elf-gcc
 CPP = ${HOME}/opt/cross/bin/i686-elf-g++ 
 CFLAGS =  -ffreestanding -O2 -Wall -Wextra
 
-OFILES =	$(BUILD_DIR)/boot.o $(BUILD_DIR)/kterm.o $(BUILD_DIR)/kernel.o  $(BUILD_DIR)/PageFrameAllocator.o $(BUILD_DIR)/io.o $(BUILD_DIR)/PageDirectory.o $(BUILD_DIR)/idt.o $(BUILD_DIR)/pic.o $(BUILD_DIR)/string.o
+OFILES =	$(BUILD_DIR)/boot.o $(BUILD_DIR)/kterm.o $(BUILD_DIR)/kernel.o  $(BUILD_DIR)/PhysicalMemoryManager.o $(BUILD_DIR)/io.o $(BUILD_DIR)/PageDirectory.o $(BUILD_DIR)/idt.o $(BUILD_DIR)/pic.o $(BUILD_DIR)/string.o
 
 SRC_DIR = src
 BUILD_DIR = build
@@ -83,5 +83,5 @@ $(BUILD_DIR)/pic.o:
 $(BUILD_DIR)/string.o:
 	$(CC) -c $(SRC_DIR)/libc/include/string.c  -o $(BUILD_DIR)/string.o $(CFLAGS) -std=gnu99
 
-$(BUILD_DIR)/PageFrameAllocator.o:
-	$(CPP) -c $(SRC_DIR)/kernel/memory/PageFrameAllocator.cpp  -o $(BUILD_DIR)/PageFrameAllocator.o $(CFLAGS) -fno-exceptions -fno-rtti
+$(BUILD_DIR)/PhysicalMemoryManager.o:
+	$(CPP) -c $(SRC_DIR)/kernel/memory/PhysicalMemoryManager.cpp  -o $(BUILD_DIR)/PhysicalMemoryManager.o $(CFLAGS) -fno-exceptions -fno-rtti

src/kernel/bootcheck.h

@@ -67,5 +67,10 @@ void CheckMBT ( multiboot_info_t*  mbt  ){
             
         }
 
+        /* Draw diagonal blue line */
+        if (CHECK_FLAG (mbt->flags, 12)){
+            printf("Can draw!");
+        } 
+
 
 }

src/kernel/kernel.cpp

@@ -1,6 +1,6 @@
 #include "kernel.h"
-#include "memory/PageFrameAllocator.h"
-
+#define GB4 524288
+#define GB2 262144
     extern "C" void early_main(unsigned long magic, unsigned long addr){
         /** initialize terminal interface */ 
         kterm_init();
@@ -16,14 +16,16 @@
 
         /* Are mmap_* valid? */
         if (CHECK_FLAG(mbt->flags, 6)){
-            mapMultibootMemoryMap(mbt);
+            PhysicalMemoryManager_initialise( mbt->mmap_addr,  GB2/* Seriously dangerous hardcoded memory value*/);
+            PhysicalMemoryManager_initialise_available_regions(mbt->mmap_addr, mbt->mmap_addr + mbt->mmap_length);
+            PhysicalMemoryManager_deinitialise_kernel();
+            extern uint8_t* kernel_begin;
+            extern uint8_t* kernel_end;
 
+            printf("Kernel MemoryMap:\n");
+            printf("kernel: 0x%x - 0x%x\n", &kernel_begin , &kernel_end);         
         }
 
-        /* Draw diagonal blue line */
-        if (CHECK_FLAG (mbt->flags, 12)){
-            printf("Can draw!");
-        } 
 
         //setupGdt();
 

src/kernel/kernel.h

@@ -6,8 +6,8 @@ extern "C"{
 #include "arch/i386/tty/kterm.h"
 
 #include "./bootloader/multiboot.h"
-
 #include "bootcheck.h"
+#include "memory/PhysicalMemoryManager.h"
 
 #include "arch/i386/gdt/gdtc.h"
 #include "arch/i386/idt/idt.h"

src/kernel/kstructures/bitmap.h

@@ -0,0 +1,40 @@
+#pragma once 
+#include <stddef.h>
+#include <stdint.h>
+
+
+inline void bitmap_set( uint32_t* map , int index )
+{
+    map[index/32] |= (1 << (index % 32));
+}
+
+inline void bitmap_unset(uint32_t* map , int index)
+{
+    map[index/32] &= ~(1 << (index % 32));
+}
+
+inline int bitmap_first_unset( uint32_t* map , int size)
+{
+    uint32_t rem_bits = size % 32;
+    for(uint32_t i = 0; i < size/32; i++)
+    {
+        if(map[i] != 0xFFFFFFFF){
+            for(int j = 0; j < 32; j++){
+                if(!(map[i] & (1<< j))){
+                    return (i*32) + j;
+                }
+            }
+        }
+    }
+
+    if(rem_bits){
+        for(uint32_t j = 0; j < rem_bits; j++){
+            if(!(map[size/32] & (1 << j ))){
+                return size + j; // Original author divided size by 32 and then multiplied it by 32 which is a net zero calculation ?!?
+            }
+        }
+    }
+
+    return -1;
+    
+}

src/kernel/memory/PhysicalMemoryManager.cpp

@@ -0,0 +1,118 @@
+#include "PhysicalMemoryManager.h"
+
+size_t mem_size = 0;
+int used_blocks = 0;
+size_t max_blocks = 0;
+uint32_t* pmmap = 0;
+size_t pmmap_size = 0; 
+
+
+void PhysicalMemoryManager_initialise(uint32_t physicalmemorymap_address, size_t size )
+{
+    mem_size = size;
+    max_blocks = KB_TO_BLOCKS(mem_size);
+
+    used_blocks = max_blocks;
+
+    pmmap = (uint32_t*) physicalmemorymap_address;
+
+    if(max_blocks % BLOCKS_PER_WORD)
+        pmmap_size++;
+    
+    memset(pmmap, 0xFF, pmmap_size);
+}
+
+void PhysicalMemoryManager_region_initialise(uint32_t base, size_t size)
+{
+    size_t blocks = size /BLOCK_SIZE;
+    uint32_t align = base / BLOCK_SIZE;
+
+    for(size_t i = 0 ; i < blocks; i ++)
+    {
+        bitmap_unset(pmmap, align++);
+        used_blocks--;
+    }
+
+    bitmap_set(pmmap, 0);
+
+}
+
+void PhysicalMemoryManager_region_deinitialise(uint32_t base, size_t size )
+{
+    size_t blocks = size / BLOCK_SIZE;
+    uint32_t align = base / BLOCK_SIZE;
+
+    for(size_t i = 0 ; i < blocks; i++ )
+    {
+        bitmap_set(pmmap, align++);
+        used_blocks++;
+    }
+
+
+}
+
+void PhysicalMemoryManager_initialise_available_regions(uint32_t mmap_, uint32_t mmap_end_)
+{
+    multiboot_memory_map_t *mmap = (multiboot_memory_map_t*)mmap_;
+    multiboot_memory_map_t *mmap_end= (multiboot_memory_map_t*) mmap_end_;
+
+    for(int i = 0; mmap < mmap_end ; mmap++, i++)
+    {   
+        if(mmap->type == MULTIBOOT_MEMORY_AVAILABLE)
+        {
+            PhysicalMemoryManager_region_initialise((uint32_t) mmap->addr, (size_t) mmap->len);
+        }
+    }
+
+}
+
+void PhysicalMemoryManager_deinitialise_kernel()
+{
+    extern uint8_t kernel_begin;
+    extern uint8_t kernel_end;
+
+    size_t kernel_size = (size_t) &kernel_end - (size_t) &kernel_begin;
+
+    uint32_t pmmap_size_aligned = pmmap_size;
+    if(!IS_ALIGNED(pmmap_size_aligned, BLOCK_SIZE))
+    {
+        pmmap_size_aligned = ALIGN(pmmap_size_aligned, BLOCK_SIZE);
+    }
+    
+    PhysicalMemoryManager_region_deinitialise((uint32_t) &kernel_begin, kernel_size);
+    PhysicalMemoryManager_region_deinitialise((uint32_t) &kernel_end, pmmap_size_aligned);
+    
+}
+
+void* PhysicalMemoryManager_allocate_block()
+{
+    if(used_blocks - max_blocks <= 0)
+    {
+        return 0;
+    }
+
+    int p_index = bitmap_first_unset(pmmap, p_index );
+
+    if(p_index == -1){
+        return 0;
+    }
+
+    bitmap_set(pmmap, p_index);
+    used_blocks++;
+
+    return (void*) (BLOCK_SIZE * p_index);
+}
+
+void PhysicalMemoryManager_free_block(void* p){
+    if(p==0){
+        return ;
+    }
+
+    uint32_t p_addr = (uint32_t) p;
+
+    int index  = p_addr / BLOCK_SIZE;
+    bitmap_unset(pmmap, index);
+
+    used_blocks--;
+
+}

src/kernel/memory/PhysicalMemoryManager.h

@@ -0,0 +1,34 @@
+#pragma once
+
+#include "../bootloader/multiboot.h"
+#include <stdint.h>
+#include <stddef.h>
+#include "../../libc/include/mem.h"
+#include "../kstructures/bitmap.h"
+
+
+#define BLOCK_SIZE 4092
+#define BLOCKS_PER_WORD 32
+
+#define KB_TO_BLOCKS(x) (((x) * 1024 ) / BLOCK_SIZE)
+#define IS_ALIGNED(addr, align) !((addr) & ~((align) - 1))
+#define ALIGN(addr, align) (((addr) & ~((align) - 1 )) + (align))
+
+
+extern void PhysicalMemoryManager_initialise(uint32_t, size_t);
+
+extern void PhysicalMemoryManager_region_initialise(uint32_t, size_t);
+extern void PhysicalMemoryManager_region_deinitialise(uint32_t,size_t);
+
+extern void PhysicalMemoryManager_initialise_available_regions(uint32_t, uint32_t);
+extern void PhysicalMemoryManager_deinitialise_kernel();
+
+extern void* PhysicalMemoryManager_allocate_block();
+extern void PhysicalMemoryManager_free_block(void* p);
+
+
+extern size_t mem_size;
+extern int used_blocks;
+extern size_t max_blocks;
+extern uint32_t* pmmap;
+extern size_t pmmap_size ; 

src/libc/include/mem.h

@@ -0,0 +1,8 @@
+inline void* memset (void* ptr, int value, size_t num){
+    for( int i = 0; i < num; i++ )
+    {
+        int* data  = (int*)ptr+ i;
+        *data = value;
+    }
+    return ptr;
+}