banan-os/kernel/arch/x86_64/MMU.cpp

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#include <BAN/Errors.h>
#include <kernel/Memory/kmalloc.h>
#include <kernel/Memory/MMU.h>
#define PAGE_SIZE 0x1000
#define PAGE_MASK ~(PAGE_SIZE - 1)
#define CLEANUP_STRUCTURE(s) \
for (uint64_t i = 0; i < 512; i++) \
if (s[i] & Flags::Present) \
goto cleanup_done; \
kfree(s)
static MMU* s_instance = nullptr;
void MMU::intialize()
{
ASSERT(s_instance == nullptr);
s_instance = new MMU();
}
MMU& MMU::get()
{
ASSERT(s_instance);
return *s_instance;
}
static uint64_t* allocate_page_aligned_page()
{
void* page = kmalloc(PAGE_SIZE, PAGE_SIZE);
ASSERT(page);
memset(page, 0, PAGE_SIZE);
return (uint64_t*)page;
}
MMU::MMU()
{
// Identity map from 4 KiB -> 6 MiB
m_highest_paging_struct = allocate_page_aligned_page();
uint64_t* pdpt = allocate_page_aligned_page();
m_highest_paging_struct[0] = (uint64_t)pdpt | Flags::ReadWrite | Flags::Present;
uint64_t* pd = allocate_page_aligned_page();
pdpt[0] = (uint64_t)pd | Flags::ReadWrite | Flags::Present;
for (uint32_t i = 0; i < 3; i++)
{
uint64_t* pt = allocate_page_aligned_page();
for (uint64_t j = 0; j < 512; j++)
pt[j] = (i << 21) | (j << 12) | Flags::ReadWrite | Flags::Present;
pd[i] = (uint64_t)pt | Flags::ReadWrite | Flags::Present;
}
// Unmap 0 -> 4 KiB
uint64_t* pt1 = (uint64_t*)(pd[0] & PAGE_MASK);
pt1[0] = 0;
// Load the new pml4
asm volatile("movq %0, %%cr3" :: "r"(m_highest_paging_struct));
}
MMU::~MMU()
{
uint64_t* pml4 = m_highest_paging_struct;
for (uint32_t pml4e = 0; pml4e < 512; pml4e++)
{
if (!(pml4[pml4e] & Flags::Present))
continue;
uint64_t* pdpt = (uint64_t*)(pml4[pml4e] & PAGE_MASK);
for (uint32_t pdpte = 0; pdpte < 512; pdpte++)
{
if (!(pdpt[pdpte] & Flags::Present))
continue;
uint64_t* pd = (uint64_t*)(pdpt[pdpte] & PAGE_MASK);
for (uint32_t pde = 0; pde < 512; pde++)
{
if (!(pd[pde] & Flags::Present))
continue;
kfree((void*)(pd[pde] & PAGE_MASK));
}
kfree(pd);
}
kfree(pdpt);
}
kfree(pml4);
}
void MMU::allocate_page(uintptr_t address, uint8_t flags)
{
ASSERT((address >> 48) == 0);
ASSERT(flags & Flags::Present);
bool should_invalidate = false;
address &= PAGE_MASK;
uint64_t pml4e = (address >> 39) & 0x1FF;
uint64_t pdpte = (address >> 30) & 0x1FF;
uint64_t pde = (address >> 21) & 0x1FF;
uint64_t pte = (address >> 12) & 0x1FF;
uint64_t* pml4 = m_highest_paging_struct;
if ((pml4[pml4e] & flags) != flags)
{
if (!(pml4[pml4e] & Flags::Present))
pml4[pml4e] = (uint64_t)allocate_page_aligned_page();
pml4[pml4e] = (pml4[pml4e] & PAGE_MASK) | flags;
should_invalidate = true;
}
uint64_t* pdpt = (uint64_t*)(pml4[pml4e] & PAGE_MASK);
if ((pdpt[pdpte] & flags) != flags)
{
if (!(pdpt[pdpte] & Flags::Present))
pdpt[pdpte] = (uint64_t)allocate_page_aligned_page();
pdpt[pdpte] = (pdpt[pdpte] & PAGE_MASK) | flags;
should_invalidate = true;
}
uint64_t* pd = (uint64_t*)(pdpt[pdpte] & PAGE_MASK);
if ((pd[pde] & flags) != flags)
{
if (!(pd[pde] & Flags::Present))
pd[pde] = (uint64_t)allocate_page_aligned_page();
pd[pde] = (pd[pde] & PAGE_MASK) | flags;
should_invalidate = true;
}
uint64_t* pt = (uint64_t*)(pd[pde] & PAGE_MASK);
if ((pt[pte] & flags) != flags)
{
pt[pte] = address | flags;
should_invalidate = true;
}
if (should_invalidate)
asm volatile("invlpg (%0)" :: "r"(address) : "memory");
}
void MMU::allocate_range(uintptr_t address, ptrdiff_t size, uint8_t flags)
{
uintptr_t s_page = address & PAGE_MASK;
uintptr_t e_page = (address + size - 1) & PAGE_MASK;
for (uintptr_t page = s_page; page <= e_page; page += PAGE_SIZE)
allocate_page(page, flags);
}
void MMU::unallocate_page(uintptr_t address)
{
ASSERT((address >> 48) == 0);
address &= PAGE_MASK;
uint64_t pml4e = (address >> 39) & 0x1FF;
uint64_t pdpte = (address >> 30) & 0x1FF;
uint64_t pde = (address >> 21) & 0x1FF;
uint64_t pte = (address >> 12) & 0x1FF;
uint64_t* pml4 = m_highest_paging_struct;
if (!(pml4[pml4e] & Flags::Present))
return;
uint64_t* pdpt = (uint64_t*)(pml4[pml4e] & PAGE_MASK);
if (!(pdpt[pdpte] & Flags::Present))
return;
uint64_t* pd = (uint64_t*)(pdpt[pdpte] & PAGE_MASK);
if (!(pd[pde] & Flags::Present))
return;
uint64_t* pt = (uint64_t*)(pd[pde] & PAGE_MASK);
if (!(pt[pte] & Flags::Present))
return;
pt[pte] = 0;
CLEANUP_STRUCTURE(pt);
pd[pde] = 0;
CLEANUP_STRUCTURE(pd);
pdpt[pdpte] = 0;
CLEANUP_STRUCTURE(pdpt);
pml4[pml4e] = 0;
cleanup_done:
asm volatile("invlpg (%0)" :: "r"(address) : "memory");
}
void MMU::unallocate_range(uintptr_t address, ptrdiff_t size)
{
uintptr_t s_page = address & PAGE_MASK;
uintptr_t e_page = (address + size - 1) & PAGE_MASK;
for (uintptr_t page = s_page; page <= e_page; page += PAGE_SIZE)
unallocate_page(page);
}