136 lines
3.8 KiB
C++
136 lines
3.8 KiB
C++
#include "memory/paging_util.h"
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#include "boot/boot_info.h"
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#include "debug/debug.h"
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#include "memory/physical_memory.h"
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#define PRESENT_BIT 0x1
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#define READ_WRITE_BIT 0x2
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#define SIGN_EXT 0xFFFF0000'00000000
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#define RECURSIVE ((uint64_t)0x1FE)
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#define PML_OFFSET 39
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#define PDP_OFFSET 30
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#define PD_OFFSET 21
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#define PT_OFFSET 12
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// How to recursively index into each page table structure assuming
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// the PML4 is recursively mapped at the 510th entry (0x1FE).
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#define PML_RECURSE 0xFFFFFF7F'BFDFE000
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#define PDP_RECURSE 0xFFFFFF7F'BFC00000
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#define PD_RECURSE 0xFFFFFF7F'80000000
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#define PT_RECURSE 0xFFFFFF00'00000000
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namespace {
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uint64_t PageAlign(uint64_t addr) { return addr & ~0xFFF; }
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uint64_t* PageAlign(uint64_t* addr) {
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return reinterpret_cast<uint64_t*>(reinterpret_cast<uint64_t>(addr) & ~0xFFF);
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}
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void ZeroOutPage(uint64_t* ptr) {
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ptr = PageAlign(ptr);
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for (uint64_t i = 0; i < 512; i++) {
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ptr[i] = 0;
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}
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}
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uint64_t ShiftForEntryIndexing(uint64_t addr, uint64_t offset) {
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addr &= ~0xFFFF0000'00000000;
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addr >>= offset;
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addr <<= 3;
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return addr;
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}
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void MapPage(uint64_t virt, uint64_t phys) {
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if (PageLoaded(virt)) {
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panic("Allocating Over Existing Page: %m", virt);
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}
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if (!PageDirectoryPointerLoaded(virt)) {
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uint64_t page = phys_mem::AllocatePage();
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*Pml4Entry(virt) = page | PRESENT_BIT | READ_WRITE_BIT;
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ZeroOutPage(PageDirectoryPointerEntry(virt));
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}
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if (!PageDirectoryLoaded(virt)) {
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uint64_t page = phys_mem::AllocatePage();
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*PageDirectoryPointerEntry(virt) = page | PRESENT_BIT | READ_WRITE_BIT;
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ZeroOutPage(PageDirectoryEntry(virt));
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}
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if (!PageTableLoaded(virt)) {
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uint64_t page = phys_mem::AllocatePage();
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*PageDirectoryEntry(virt) = page | PRESENT_BIT | READ_WRITE_BIT;
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ZeroOutPage(PageTableEntry(virt));
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}
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*PageTableEntry(virt) = PageAlign(phys) | PRESENT_BIT | READ_WRITE_BIT;
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ZeroOutPage(reinterpret_cast<uint64_t*>(virt));
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}
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} // namespace
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void InitPaging() {
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uint64_t pml4_addr = 0;
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asm volatile("mov %%cr3, %0;" : "=r"(pml4_addr));
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InitializePml4(pml4_addr);
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}
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void InitializePml4(uint64_t pml4_physical_addr) {
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uint64_t* pml4_virtual = reinterpret_cast<uint64_t*>(
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boot::GetHigherHalfDirectMap() + pml4_physical_addr);
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uint64_t recursive_entry = pml4_physical_addr | PRESENT_BIT | READ_WRITE_BIT;
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pml4_virtual[0x1FE] = recursive_entry;
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}
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void AllocatePage(uint64_t addr) {
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uint64_t physical_page = phys_mem::AllocatePage();
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MapPage(addr, physical_page);
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}
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void EnsureResident(uint64_t addr, uint64_t size) {
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uint64_t max = addr + size;
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addr = PageAlign(addr);
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while (addr < max) {
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if (!PageLoaded(addr)) {
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AllocatePage(addr);
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}
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addr += 0x1000;
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}
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}
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uint64_t* Pml4Entry(uint64_t addr) {
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return reinterpret_cast<uint64_t*>(PML_RECURSE |
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ShiftForEntryIndexing(addr, PML_OFFSET));
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}
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uint64_t* PageDirectoryPointerEntry(uint64_t addr) {
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return reinterpret_cast<uint64_t*>(PDP_RECURSE |
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ShiftForEntryIndexing(addr, PDP_OFFSET));
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}
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uint64_t* PageDirectoryEntry(uint64_t addr) {
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return reinterpret_cast<uint64_t*>(PD_RECURSE |
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ShiftForEntryIndexing(addr, PD_OFFSET));
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}
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uint64_t* PageTableEntry(uint64_t addr) {
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return reinterpret_cast<uint64_t*>(PT_RECURSE |
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ShiftForEntryIndexing(addr, PT_OFFSET));
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}
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bool PageDirectoryPointerLoaded(uint64_t addr) {
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return *Pml4Entry(addr) & PRESENT_BIT;
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}
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bool PageDirectoryLoaded(uint64_t addr) {
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return PageDirectoryPointerLoaded(addr) &&
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(*PageDirectoryPointerEntry(addr) & PRESENT_BIT);
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}
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bool PageTableLoaded(uint64_t addr) {
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return PageDirectoryLoaded(addr) && (*PageDirectoryEntry(addr) & PRESENT_BIT);
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}
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bool PageLoaded(uint64_t addr) {
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return PageTableLoaded(addr) && (*PageTableEntry(addr) & PRESENT_BIT);
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}
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