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) \
return; \
kfree(s)
static MMU* s_instance = nullptr;
void MMU::initialize()
{
ASSERT(s_instance == nullptr);
s_instance = new MMU();
ASSERT(s_instance);
s_instance->initialize_kernel();
s_instance->load();
}
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;
}
extern uint8_t g_kernel_end[];
void MMU::initialize_kernel()
{
// FIXME: We should just identity map until g_kernel_end
ASSERT((uintptr_t)g_kernel_end <= 6 * (1 << 20));
// Identity map from 0 -> 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;
}
MMU::MMU()
{
if (s_instance == nullptr)
return;
// Here we copy the s_instances paging structs since they are
// global for every process
uint64_t* global_pml4 = s_instance->m_highest_paging_struct;
uint64_t* pml4 = allocate_page_aligned_page();
for (uint32_t pml4e = 0; pml4e < 512; pml4e++)
{
if (!(global_pml4[pml4e] & Flags::Present))
continue;
uint64_t* global_pdpt = (uint64_t*)(global_pml4[pml4e] & PAGE_MASK);
uint64_t* pdpt = allocate_page_aligned_page();
pml4[pml4e] = (uint64_t)pdpt | (global_pml4[pml4e] & ~PAGE_MASK);
for (uint32_t pdpte = 0; pdpte < 512; pdpte++)
{
if (!(global_pdpt[pdpte] & Flags::Present))
continue;
uint64_t* global_pd = (uint64_t*)(global_pdpt[pdpte] & PAGE_MASK);
uint64_t* pd = allocate_page_aligned_page();
pdpt[pdpte] = (uint64_t)pd | (global_pdpt[pdpte] & ~PAGE_MASK);
for (uint32_t pde = 0; pde < 512; pde++)
{
if (!(global_pd[pde] & Flags::Present))
continue;
uint64_t* global_pt = (uint64_t*)(global_pd[pde] & PAGE_MASK);
uint64_t* pt = allocate_page_aligned_page();
pd[pde] = (uint64_t)pt | (global_pd[pde] & ~PAGE_MASK);
memcpy(pt, global_pt, PAGE_SIZE);
}
}
}
m_highest_paging_struct = pml4;
}
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::load()
{
asm volatile("movq %0, %%cr3" :: "r"(m_highest_paging_struct));
}
void MMU::map_page(uintptr_t address, uint8_t flags)
{
address &= PAGE_MASK;
map_page_at(address, address, flags);
}
void MMU::map_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)
map_page(page, flags);
}
void MMU::unmap_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;
}
void MMU::unmap_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)
unmap_page(page);
}
void MMU::map_page_at(paddr_t paddr, vaddr_t vaddr, uint8_t flags)
{
ASSERT((paddr >> 48) == 0);
ASSERT((vaddr >> 48) == 0);
ASSERT((paddr & ~PAGE_MASK) == 0);
ASSERT((vaddr & ~PAGE_MASK) == 0);;
ASSERT(flags & Flags::Present);
uint64_t pml4e = (vaddr >> 39) & 0x1FF;
uint64_t pdpte = (vaddr >> 30) & 0x1FF;
uint64_t pde = (vaddr >> 21) & 0x1FF;
uint64_t pte = (vaddr >> 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;
}
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;
}
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;
}
uint64_t* pt = (uint64_t*)(pd[pde] & PAGE_MASK);
if ((pt[pte] & flags) != flags)
pt[pte] = paddr | flags;
}