BarinkOS/source/kernel/memory/PhysicalMemoryManager.cpp

116 lines
3.2 KiB
C++

#include "./PhysicalMemoryManager.h"
#define IS_ALIGNED(addr, align) !((addr) & ~((align) - 1))
#define ALIGN(addr, align) (((addr) & ~((align) - 1 )) + (align))
const uint32_t KERNEL_OFFSET = 0xC0000000;
uint32_t* memoryBitMap;
uint32_t pmmap_size;
uint32_t max_blocks;
int used_blocks;
void SetupPhysicalMemoryManager(uint32_t mapAddress, uint32_t memorySize )
{
/*
Every byte contains 8 pages
A page is 4096 kib
Every block (1 bit) represent an page
*/
// Set the maximum number of blocks
max_blocks = (uint32_t)memorySize / BLOCK_SIZE ;
printf("Max Blocks: %d\n", max_blocks);
// Set size of the bitmap
uint32_t bitmap_size = max_blocks / 32;
printf("Bitmap size: %d bytes\n",bitmap_size);
// Set blocks used to zero
used_blocks = max_blocks;
// set the address of the memory bitmap
memoryBitMap = (uint32_t*) mapAddress;
// Set all places in memory as free
memset(memoryBitMap, 0xFFFFFFFF, max_blocks / 32 );
}
// 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 = 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 );
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 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 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(memoryBitMap, startBlock + i);// allocate region causes #PF Exception
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(memoryBitMap, startBlock + i);
used_blocks --;
}
}
int GetUsedBlocks (){
return used_blocks;
}