int MMU::pfree(void *startOfMemoryRange, size_t numberOfPages)
{
uint32_t virtualAddress = (uint32_t) startOfMemoryRange;
if (!numberOfPages) return -1;
while (numberOfPages--) {
uint32_t pdeIndex = virtualAddress >> 22;
uint32_t pteIndex = virtualAddress >> 12 & 0x03FF;
PageTable table = PageTableForDirectoryIndex(pdeIndex);
PageEntry pte = table.entryAtIndex(pteIndex);
_pageFrameAllocator.free(pte.address());
table.setEntry(pteIndex, PageEntry(0));
virtualAddress += 0x1000;
}
_flush();
return 0;
}
void MMU::allocatePages(void *address, size_t numberOfPages)
{
uintptr_t virtualAddress = reinterpret_cast<uintptr_t>(address);
uint32_t currpde = virtualAddress >> 22;
uint32_t currpte = virtualAddress >> 12 & 0x03FF;
size_t pagesLeft = numberOfPages;
while (pagesLeft > 0) { // map the pages
PageTable table = PageTableForDirectoryIndex(currpde);
PageEntry entry = PageEntry(_pageFrameAllocator.alloc());
entry.setFlags(kPresentBit | kReadWriteBit);
table.setEntry(currpte, entry);
++currpte;
--pagesLeft;
// move to next PDE if needed
if (currpte > 1023) {
++currpde;
currpte = 0;
}
}
_flush();
}
