88 lines
2.5 KiB
C++
88 lines
2.5 KiB
C++
#include "KernelHeap.h"
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#include "VirtualMemoryManager.h"
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// Size of heap meta data is 5 bytes
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struct heap_block{
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uint8_t Used;
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uint32_t Size;
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};
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uint32_t heap_size;
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heap_block* start ;
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void* malloc(size_t size)
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{
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printf("Received request for %d bytes of memory\n", size);
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heap_block* current = start;
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// look for a free block
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while(current < start + heap_size)
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{
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if(current->Size >= size && current->Used == false )
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{
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// We found a spot
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printf("Block found!\n");
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// Set the spot to in-use
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current->Used = true;
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// split the block
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printf("Split block.\n");
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uint32_t oldSize = current->Size;
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current->Size = size;
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heap_block* new_block = current + sizeof(heap_block) + current->Size;
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new_block->Size = oldSize - ( sizeof(heap_block) + size);
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new_block->Used = false;
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// return the free address
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// NOTE: added an offset from the initial address to accomodate for
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// meta-data.
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return current + sizeof(heap_block);
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}
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current += current->Size + sizeof(heap_block);
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}
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// If we are here we need more memory so we should
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// probably ask the VMM for more
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// TODO: ask for more memory | Extend kernel heap
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printf("ERROR: OUT OF HEAP MEMORY CONDITION IS NOT IMPLEMENTED. HEAP NEEDS TO BE EXTENDED!\n");
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}
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void free(void* addr)
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{
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// clear the free boolean that corresponds to this adddress
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// This should be fairly simple
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heap_block* allocatedBlock = (heap_block*)(addr - sizeof(heap_block));
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allocatedBlock->Used = false;
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}
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void initHeap()
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{
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// put the start of our kernel heap 1 page after the kernel_end address
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// Lets calculate the address
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printf("FIND SUITABLE HEAP_ADDRESS\n");
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uint32_t alligned_k_end = (uint32_t) &kernel_end + ((uint32_t)&kernel_end % BLOCK_SIZE == 0 ? 4096 : 0);
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uint32_t HEAP_ADDRESS = (uint32_t) alligned_k_end + 4096;
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printf("HEAP_ADDRESS: 0x%x\n", HEAP_ADDRESS);
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// NOTE: we can't check if the mapping has failed or not here!
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AllocatePage(HEAP_ADDRESS);
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start = (heap_block*) HEAP_ADDRESS;
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heap_size = 4096;
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printf("Clear heap\n");
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// Clear the heap
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printf("set at 0x%x %d bytes to zero\n", start , heap_size);
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memset((void*)start, 0x00, heap_size /4);
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printf("Init first heap block\n");
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// initialzie
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start->Size = heap_size - sizeof(heap_block);
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start->Used = false;
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} |