BarinkOS/source/kernel/memory/VirtualMemoryManager.cpp

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#include "VirtualMemoryManager.h"
extern uint32_t boot_page_directory[1024] ;
extern uint32_t boot_page_table[1024];
void AllocatePage(uint32_t vaddr)
{
uint32_t page_aligned_address = ALIGN(vaddr, 4096);
// allocate a page at virtual address
int PageDirectoryEntryIndex = vaddr >> 22;
int PageTableEntryIndex = (vaddr >> 12) & 0x1FFF;
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);
// check if the page table entry is marked as present
if ( page_table[PageTableEntryIndex] & 0x1 )
{
// Map the entry to a physical page
page_table[PageTableEntryIndex] = (uint32_t)(allocate_block() + 0x3);
} else{
// mark page as present
page_table[PageTableEntryIndex] = 0x3;
}
} else {
// mark the page table as present and allocate a physical block for it
boot_page_directory[PageDirectoryEntryIndex] = (uint32_t)(allocate_block() + 0x3);
}
}
void FreePage(uint32_t vaddr )
{
uint32_t page_aligned_address = ALIGN(vaddr, 4096);
// allocate a page at virtual address
int PageDirectoryEntryIndex = vaddr >> 22;
int PageTableEntryIndex = (vaddr >> 12) & 0x1FFF;
uint32_t* pageTable = (uint32_t*)(boot_page_directory[PageDirectoryEntryIndex] & 0xFFFFE000 + 0xC0000000);
void* physicalAddressToFree = (void*)(pageTable[PageTableEntryIndex] & 0xFFFFE000 + 0xC0000000);
free_block(physicalAddressToFree);
pageTable[PageTableEntryIndex] = 0x0;
}
void Map ( uint32_t vaddr, uint32_t paddr)
{
uint32_t page_aligned_address = ALIGN(vaddr, 4096);
// allocate a page at virtual address
int PageDirectoryEntryIndex = vaddr >> 22;
int PageTableEntryIndex = (vaddr >> 12) & 0x1FFF;
}
void Unmap(uint32_t vaddr)
{
// NOTE: I will implement lazy unmapping for now
uint32_t page_aligned_address = ALIGN(vaddr, 4096);
// allocate a page at virtual address
int PageDirectoryEntryIndex = vaddr >> 22;
int PageTableEntryIndex = (vaddr >> 12) & 0x1FFF;
}