BarinkOS/source/kernel/memory/KernelHeap.cpp

88 lines
2.5 KiB
C++

#include "KernelHeap.h"
#include "VirtualMemoryManager.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\n", 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
printf("Block found!\n");
// Set the spot to in-use
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.
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
printf("ERROR: OUT OF HEAP MEMORY CONDITION IS NOT IMPLEMENTED. HEAP NEEDS TO BE EXTENDED!\n");
}
void free(void* addr)
{
// clear the free boolean that corresponds to this adddress
// This should be fairly simple
heap_block* allocatedBlock = (heap_block*)(addr - sizeof(heap_block));
allocatedBlock->Used = false;
}
void initHeap()
{
// 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;
}