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

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#include <BAN/Errors.h>
#include <kernel/Arch.h>
#include <kernel/LockGuard.h>
#include <kernel/Memory/kmalloc.h>
#include <kernel/Memory/PageTable.h>
#define CLEANUP_STRUCTURE(s) \
do { \
for (uint64_t i = 0; i < 512; i++) \
if ((s)[i] & Flags::Present) \
return; \
kfree(s); \
} while (false)
extern uint8_t g_kernel_start[];
extern uint8_t g_kernel_end[];
namespace Kernel
{
static PageTable* s_kernel = nullptr;
static PageTable* s_current = nullptr;
static constexpr inline bool is_canonical(uintptr_t addr)
{
constexpr uintptr_t mask = 0xFFFF800000000000;
addr &= mask;
return addr == mask || addr == 0;
}
static constexpr inline uintptr_t uncanonicalize(uintptr_t addr)
{
if (addr & 0x0000800000000000)
return addr & ~0xFFFF000000000000;
return addr;
}
static constexpr inline uintptr_t canonicalize(uintptr_t addr)
{
if (addr & 0x0000800000000000)
return addr | 0xFFFF000000000000;
return addr;
}
void PageTable::initialize()
{
ASSERT(s_kernel == nullptr);
s_kernel = new PageTable();
ASSERT(s_kernel);
s_kernel->initialize_kernel();
s_kernel->load();
}
PageTable& PageTable::kernel()
{
ASSERT(s_kernel);
return *s_kernel;
}
PageTable& PageTable::current()
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{
ASSERT(s_current);
return *s_current;
}
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;
}
void PageTable::initialize_kernel()
{
m_highest_paging_struct = V2P(allocate_page_aligned_page());
memset((void*)P2V(m_highest_paging_struct), 0, PAGE_SIZE);
// Identity map 4 KiB -> kernel end. We don't map the first page since nullptr derefs should
// page fault. Also there isn't anything useful in that memory.
map_range_at(0, KERNEL_OFFSET, (uintptr_t)g_kernel_end - KERNEL_OFFSET, Flags::ReadWrite | Flags::Present);
}
BAN::ErrorOr<PageTable*> PageTable::create_userspace()
{
// Here we copy the s_kernel paging structs since they are
// global for every process
LockGuard _(s_kernel->m_lock);
uint64_t* global_pml4 = (uint64_t*)P2V(s_kernel->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*)P2V(global_pml4[pml4e] & PAGE_ADDR_MASK);
uint64_t* pdpt = allocate_page_aligned_page();
pml4[pml4e] = V2P(pdpt) | (global_pml4[pml4e] & PAGE_FLAG_MASK);
for (uint32_t pdpte = 0; pdpte < 512; pdpte++)
{
if (!(global_pdpt[pdpte] & Flags::Present))
continue;
uint64_t* global_pd = (uint64_t*)P2V(global_pdpt[pdpte] & PAGE_ADDR_MASK);
uint64_t* pd = allocate_page_aligned_page();
pdpt[pdpte] = V2P(pd) | (global_pdpt[pdpte] & PAGE_FLAG_MASK);
for (uint32_t pde = 0; pde < 512; pde++)
{
if (!(global_pd[pde] & Flags::Present))
continue;
uint64_t* global_pt = (uint64_t*)P2V(global_pd[pde] & PAGE_ADDR_MASK);
uint64_t* pt = allocate_page_aligned_page();
pd[pde] = V2P(pt) | (global_pd[pde] & PAGE_FLAG_MASK);
memcpy(pt, global_pt, PAGE_SIZE);
}
}
}
PageTable* result = new PageTable;
if (result == nullptr)
return BAN::Error::from_errno(ENOMEM);
result->m_highest_paging_struct = V2P(pml4);
return result;
}
PageTable::~PageTable()
{
uint64_t* pml4 = (uint64_t*)P2V(m_highest_paging_struct);
for (uint32_t pml4e = 0; pml4e < 512; pml4e++)
{
if (!(pml4[pml4e] & Flags::Present))
continue;
uint64_t* pdpt = (uint64_t*)P2V(pml4[pml4e] & PAGE_ADDR_MASK);
for (uint32_t pdpte = 0; pdpte < 512; pdpte++)
{
if (!(pdpt[pdpte] & Flags::Present))
continue;
uint64_t* pd = (uint64_t*)P2V(pdpt[pdpte] & PAGE_ADDR_MASK);
for (uint32_t pde = 0; pde < 512; pde++)
{
if (!(pd[pde] & Flags::Present))
continue;
kfree((void*)P2V(pd[pde] & PAGE_ADDR_MASK));
}
kfree(pd);
}
kfree(pdpt);
}
kfree(pml4);
}
void PageTable::load()
{
asm volatile("movq %0, %%cr3" :: "r"(m_highest_paging_struct));
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s_current = this;
}
void PageTable::invalidate(vaddr_t vaddr)
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{
ASSERT(this == s_current);
asm volatile("invlpg (%0)" :: "r"(vaddr) : "memory");
}
void PageTable::identity_map_page(paddr_t address, flags_t flags)
{
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address &= PAGE_ADDR_MASK;
map_page_at(address, address, flags);
}
void PageTable::identity_map_range(paddr_t address, size_t size, flags_t flags)
{
LockGuard _(m_lock);
paddr_t s_page = address / PAGE_SIZE;
paddr_t e_page = (address + size - 1) / PAGE_SIZE;
for (paddr_t page = s_page; page <= e_page; page++)
identity_map_page(page * PAGE_SIZE, flags);
}
void PageTable::unmap_page(vaddr_t vaddr)
{
LockGuard _(m_lock);
ASSERT(is_canonical(vaddr));
vaddr = uncanonicalize(vaddr);
vaddr &= PAGE_ADDR_MASK;
if (is_page_free(vaddr))
{
dwarnln("unmapping unmapped page {8H}", vaddr);
return;
}
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 = (uint64_t*)P2V(m_highest_paging_struct);
uint64_t* pdpt = (uint64_t*)P2V(pml4[pml4e] & PAGE_ADDR_MASK);
uint64_t* pd = (uint64_t*)P2V(pdpt[pdpte] & PAGE_ADDR_MASK);
uint64_t* pt = (uint64_t*)P2V(pd[pde] & PAGE_ADDR_MASK);
pt[pte] = 0;
CLEANUP_STRUCTURE(pt);
pd[pde] = 0;
CLEANUP_STRUCTURE(pd);
pdpt[pdpte] = 0;
CLEANUP_STRUCTURE(pdpt);
pml4[pml4e] = 0;
}
void PageTable::unmap_range(vaddr_t vaddr, size_t size)
{
LockGuard _(m_lock);
vaddr_t s_page = vaddr / PAGE_SIZE;
vaddr_t e_page = (vaddr + size - 1) / PAGE_SIZE;
for (vaddr_t page = s_page; page <= e_page; page++)
unmap_page(page * PAGE_SIZE);
}
void PageTable::map_page_at(paddr_t paddr, vaddr_t vaddr, flags_t flags)
{
LockGuard _(m_lock);
ASSERT(is_canonical(vaddr));
vaddr = uncanonicalize(vaddr);
ASSERT(paddr % PAGE_SIZE == 0);
ASSERT(vaddr % PAGE_SIZE == 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 = (uint64_t*)P2V(m_highest_paging_struct);
if ((pml4[pml4e] & flags) != flags)
{
if (!(pml4[pml4e] & Flags::Present))
pml4[pml4e] = V2P(allocate_page_aligned_page());
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pml4[pml4e] = (pml4[pml4e] & PAGE_ADDR_MASK) | flags;
}
uint64_t* pdpt = (uint64_t*)P2V(pml4[pml4e] & PAGE_ADDR_MASK);
if ((pdpt[pdpte] & flags) != flags)
{
if (!(pdpt[pdpte] & Flags::Present))
pdpt[pdpte] = V2P(allocate_page_aligned_page());
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pdpt[pdpte] = (pdpt[pdpte] & PAGE_ADDR_MASK) | flags;
}
uint64_t* pd = (uint64_t*)P2V(pdpt[pdpte] & PAGE_ADDR_MASK);
if ((pd[pde] & flags) != flags)
{
if (!(pd[pde] & Flags::Present))
pd[pde] = V2P(allocate_page_aligned_page());
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pd[pde] = (pd[pde] & PAGE_ADDR_MASK) | flags;
}
uint64_t* pt = (uint64_t*)P2V(pd[pde] & PAGE_ADDR_MASK);
pt[pte] = paddr | flags;
}
void PageTable::map_range_at(paddr_t paddr, vaddr_t vaddr, size_t size, flags_t flags)
{
LockGuard _(m_lock);
ASSERT(is_canonical(vaddr));
ASSERT(paddr % PAGE_SIZE == 0);
ASSERT(vaddr % PAGE_SIZE == 0);
size_t first_page = vaddr / PAGE_SIZE;
size_t last_page = (vaddr + size - 1) / PAGE_SIZE;
size_t page_count = last_page - first_page + 1;
for (size_t page = 0; page < page_count; page++)
map_page_at(paddr + page * PAGE_SIZE, vaddr + page * PAGE_SIZE, flags);
}
uint64_t PageTable::get_page_data(vaddr_t vaddr) const
{
LockGuard _(m_lock);
ASSERT(is_canonical(vaddr));
vaddr = uncanonicalize(vaddr);
ASSERT(vaddr % PAGE_SIZE == 0);
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 = (uint64_t*)P2V(m_highest_paging_struct);
if (!(pml4[pml4e] & Flags::Present))
return 0;
uint64_t* pdpt = (uint64_t*)P2V(pml4[pml4e] & PAGE_ADDR_MASK);
if (!(pdpt[pdpte] & Flags::Present))
return 0;
uint64_t* pd = (uint64_t*)P2V(pdpt[pdpte] & PAGE_ADDR_MASK);
if (!(pd[pde] & Flags::Present))
return 0;
uint64_t* pt = (uint64_t*)P2V(pd[pde] & PAGE_ADDR_MASK);
if (!(pt[pte] & Flags::Present))
return 0;
return pt[pte];
}
PageTable::flags_t PageTable::get_page_flags(vaddr_t addr) const
{
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return get_page_data(addr) & PAGE_FLAG_MASK;
}
paddr_t PageTable::physical_address_of(vaddr_t addr) const
{
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return get_page_data(addr) & PAGE_ADDR_MASK;
}
vaddr_t PageTable::get_free_page() const
{
LockGuard _(m_lock);
// Try to find free page that can be mapped without
// allocations (page table with unused entries)
uint64_t* pml4 = (uint64_t*)P2V(m_highest_paging_struct);
for (uint64_t pml4e = 0; pml4e < 512; pml4e++)
{
if (!(pml4[pml4e] & Flags::Present))
continue;
uint64_t* pdpt = (uint64_t*)P2V(pml4[pml4e] & PAGE_ADDR_MASK);
for (uint64_t pdpte = 0; pdpte < 512; pdpte++)
{
if (!(pdpt[pdpte] & Flags::Present))
continue;
uint64_t* pd = (uint64_t*)P2V(pdpt[pdpte] & PAGE_ADDR_MASK);
for (uint64_t pde = 0; pde < 512; pde++)
{
if (!(pd[pde] & Flags::Present))
continue;
uint64_t* pt = (uint64_t*)P2V(pd[pde] & PAGE_ADDR_MASK);
for (uint64_t pte = !(pml4e + pdpte + pde); pte < 512; pte++)
{
if (!(pt[pte] & Flags::Present))
{
vaddr_t vaddr = 0;
vaddr |= pml4e << 39;
vaddr |= pdpte << 30;
vaddr |= pde << 21;
vaddr |= pte << 12;
return canonicalize(vaddr);
}
}
}
}
}
// Find any free page page (except for page 0)
vaddr_t vaddr = PAGE_SIZE;
while ((vaddr >> 48) == 0)
{
if (!(get_page_flags(vaddr) & Flags::Present))
return vaddr;
vaddr += PAGE_SIZE;
}
ASSERT_NOT_REACHED();
}
vaddr_t PageTable::get_free_contiguous_pages(size_t page_count) const
{
LockGuard _(m_lock);
for (vaddr_t vaddr = PAGE_SIZE; !(vaddr >> 48); vaddr += PAGE_SIZE)
{
bool valid { true };
for (size_t page = 0; page < page_count; page++)
{
if (get_page_flags(vaddr + page * PAGE_SIZE) & Flags::Present)
{
vaddr += page * PAGE_SIZE;
valid = false;
break;
}
}
if (valid)
return vaddr;
}
ASSERT_NOT_REACHED();
}
bool PageTable::is_page_free(vaddr_t page) const
{
ASSERT(page % PAGE_SIZE == 0);
return !(get_page_flags(page) & Flags::Present);
}
bool PageTable::is_range_free(vaddr_t start, size_t size) const
{
LockGuard _(m_lock);
vaddr_t first_page = start / PAGE_SIZE;
vaddr_t last_page = (start + size - 1) / PAGE_SIZE;
for (vaddr_t page = first_page; page <= last_page; page++)
if (!is_page_free(page * PAGE_SIZE))
return false;
return true;
}
}