forked from Bananymous/banan-os
430 lines
11 KiB
C++
430 lines
11 KiB
C++
#include <BAN/Errors.h>
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#include <kernel/Arch.h>
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#include <kernel/LockGuard.h>
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#include <kernel/Memory/kmalloc.h>
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#include <kernel/Memory/PageTable.h>
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#define CLEANUP_STRUCTURE(s) \
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do { \
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for (uint64_t i = 0; i < 512; i++) \
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if ((s)[i] & Flags::Present) \
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return; \
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kfree(s); \
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} while (false)
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extern uint8_t g_kernel_start[];
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extern uint8_t g_kernel_end[];
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namespace Kernel
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{
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static PageTable* s_kernel = nullptr;
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static PageTable* s_current = nullptr;
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static constexpr inline bool is_canonical(uintptr_t addr)
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{
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constexpr uintptr_t mask = 0xFFFF800000000000;
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addr &= mask;
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return addr == mask || addr == 0;
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}
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static constexpr inline uintptr_t uncanonicalize(uintptr_t addr)
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{
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if (addr & 0x0000800000000000)
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return addr & ~0xFFFF000000000000;
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return addr;
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}
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static constexpr inline uintptr_t canonicalize(uintptr_t addr)
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{
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if (addr & 0x0000800000000000)
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return addr | 0xFFFF000000000000;
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return addr;
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}
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void PageTable::initialize()
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{
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ASSERT(s_kernel == nullptr);
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s_kernel = new PageTable();
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ASSERT(s_kernel);
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s_kernel->initialize_kernel();
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s_kernel->load();
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}
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PageTable& PageTable::kernel()
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{
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ASSERT(s_kernel);
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return *s_kernel;
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}
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PageTable& PageTable::current()
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{
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ASSERT(s_current);
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return *s_current;
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}
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static uint64_t* allocate_page_aligned_page()
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{
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void* page = kmalloc(PAGE_SIZE, PAGE_SIZE);
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ASSERT(page);
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memset(page, 0, PAGE_SIZE);
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return (uint64_t*)page;
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}
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void PageTable::initialize_kernel()
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{
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m_highest_paging_struct = V2P(allocate_page_aligned_page());
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memset((void*)P2V(m_highest_paging_struct), 0, PAGE_SIZE);
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// Identity map 4 KiB -> kernel end. We don't map the first page since nullptr derefs should
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// page fault. Also there isn't anything useful in that memory.
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map_range_at(0, KERNEL_OFFSET, (uintptr_t)g_kernel_end - KERNEL_OFFSET, Flags::ReadWrite | Flags::Present);
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}
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BAN::ErrorOr<PageTable*> PageTable::create_userspace()
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{
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// Here we copy the s_kernel paging structs since they are
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// global for every process
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LockGuard _(s_kernel->m_lock);
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uint64_t* global_pml4 = (uint64_t*)P2V(s_kernel->m_highest_paging_struct);
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uint64_t* pml4 = allocate_page_aligned_page();
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for (uint32_t pml4e = 0; pml4e < 512; pml4e++)
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{
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if (!(global_pml4[pml4e] & Flags::Present))
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continue;
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uint64_t* global_pdpt = (uint64_t*)P2V(global_pml4[pml4e] & PAGE_ADDR_MASK);
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uint64_t* pdpt = allocate_page_aligned_page();
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pml4[pml4e] = V2P(pdpt) | (global_pml4[pml4e] & PAGE_FLAG_MASK);
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for (uint32_t pdpte = 0; pdpte < 512; pdpte++)
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{
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if (!(global_pdpt[pdpte] & Flags::Present))
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continue;
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uint64_t* global_pd = (uint64_t*)P2V(global_pdpt[pdpte] & PAGE_ADDR_MASK);
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uint64_t* pd = allocate_page_aligned_page();
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pdpt[pdpte] = V2P(pd) | (global_pdpt[pdpte] & PAGE_FLAG_MASK);
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for (uint32_t pde = 0; pde < 512; pde++)
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{
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if (!(global_pd[pde] & Flags::Present))
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continue;
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uint64_t* global_pt = (uint64_t*)P2V(global_pd[pde] & PAGE_ADDR_MASK);
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uint64_t* pt = allocate_page_aligned_page();
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pd[pde] = V2P(pt) | (global_pd[pde] & PAGE_FLAG_MASK);
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memcpy(pt, global_pt, PAGE_SIZE);
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}
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}
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}
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PageTable* result = new PageTable;
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if (result == nullptr)
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return BAN::Error::from_errno(ENOMEM);
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result->m_highest_paging_struct = V2P(pml4);
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return result;
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}
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PageTable::~PageTable()
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{
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uint64_t* pml4 = (uint64_t*)P2V(m_highest_paging_struct);
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for (uint32_t pml4e = 0; pml4e < 512; pml4e++)
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{
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if (!(pml4[pml4e] & Flags::Present))
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continue;
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uint64_t* pdpt = (uint64_t*)P2V(pml4[pml4e] & PAGE_ADDR_MASK);
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for (uint32_t pdpte = 0; pdpte < 512; pdpte++)
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{
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if (!(pdpt[pdpte] & Flags::Present))
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continue;
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uint64_t* pd = (uint64_t*)P2V(pdpt[pdpte] & PAGE_ADDR_MASK);
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for (uint32_t pde = 0; pde < 512; pde++)
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{
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if (!(pd[pde] & Flags::Present))
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continue;
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kfree((void*)P2V(pd[pde] & PAGE_ADDR_MASK));
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}
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kfree(pd);
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}
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kfree(pdpt);
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}
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kfree(pml4);
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}
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void PageTable::load()
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{
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asm volatile("movq %0, %%cr3" :: "r"(m_highest_paging_struct));
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s_current = this;
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}
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void PageTable::invalidate(vaddr_t vaddr)
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{
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ASSERT(this == s_current);
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asm volatile("invlpg (%0)" :: "r"(vaddr) : "memory");
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}
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void PageTable::identity_map_page(paddr_t address, flags_t flags)
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{
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address &= PAGE_ADDR_MASK;
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map_page_at(address, address, flags);
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}
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void PageTable::identity_map_range(paddr_t address, size_t size, flags_t flags)
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{
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LockGuard _(m_lock);
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paddr_t s_page = address / PAGE_SIZE;
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paddr_t e_page = (address + size - 1) / PAGE_SIZE;
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for (paddr_t page = s_page; page <= e_page; page++)
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identity_map_page(page * PAGE_SIZE, flags);
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}
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void PageTable::unmap_page(vaddr_t vaddr)
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{
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LockGuard _(m_lock);
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ASSERT(is_canonical(vaddr));
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vaddr = uncanonicalize(vaddr);
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vaddr &= PAGE_ADDR_MASK;
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if (is_page_free(vaddr))
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{
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dwarnln("unmapping unmapped page {8H}", vaddr);
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return;
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}
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uint64_t pml4e = (vaddr >> 39) & 0x1FF;
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uint64_t pdpte = (vaddr >> 30) & 0x1FF;
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uint64_t pde = (vaddr >> 21) & 0x1FF;
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uint64_t pte = (vaddr >> 12) & 0x1FF;
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uint64_t* pml4 = (uint64_t*)P2V(m_highest_paging_struct);
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uint64_t* pdpt = (uint64_t*)P2V(pml4[pml4e] & PAGE_ADDR_MASK);
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uint64_t* pd = (uint64_t*)P2V(pdpt[pdpte] & PAGE_ADDR_MASK);
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uint64_t* pt = (uint64_t*)P2V(pd[pde] & PAGE_ADDR_MASK);
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pt[pte] = 0;
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CLEANUP_STRUCTURE(pt);
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pd[pde] = 0;
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CLEANUP_STRUCTURE(pd);
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pdpt[pdpte] = 0;
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CLEANUP_STRUCTURE(pdpt);
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pml4[pml4e] = 0;
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}
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void PageTable::unmap_range(vaddr_t vaddr, size_t size)
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{
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LockGuard _(m_lock);
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vaddr_t s_page = vaddr / PAGE_SIZE;
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vaddr_t e_page = (vaddr + size - 1) / PAGE_SIZE;
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for (vaddr_t page = s_page; page <= e_page; page++)
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unmap_page(page * PAGE_SIZE);
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}
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void PageTable::map_page_at(paddr_t paddr, vaddr_t vaddr, flags_t flags)
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{
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LockGuard _(m_lock);
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ASSERT(is_canonical(vaddr));
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vaddr = uncanonicalize(vaddr);
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ASSERT(paddr % PAGE_SIZE == 0);
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ASSERT(vaddr % PAGE_SIZE == 0);;
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ASSERT(flags & Flags::Present);
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uint64_t pml4e = (vaddr >> 39) & 0x1FF;
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uint64_t pdpte = (vaddr >> 30) & 0x1FF;
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uint64_t pde = (vaddr >> 21) & 0x1FF;
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uint64_t pte = (vaddr >> 12) & 0x1FF;
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uint64_t* pml4 = (uint64_t*)P2V(m_highest_paging_struct);
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if ((pml4[pml4e] & flags) != flags)
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{
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if (!(pml4[pml4e] & Flags::Present))
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pml4[pml4e] = V2P(allocate_page_aligned_page());
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pml4[pml4e] = (pml4[pml4e] & PAGE_ADDR_MASK) | flags;
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}
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uint64_t* pdpt = (uint64_t*)P2V(pml4[pml4e] & PAGE_ADDR_MASK);
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if ((pdpt[pdpte] & flags) != flags)
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{
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if (!(pdpt[pdpte] & Flags::Present))
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pdpt[pdpte] = V2P(allocate_page_aligned_page());
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pdpt[pdpte] = (pdpt[pdpte] & PAGE_ADDR_MASK) | flags;
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}
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uint64_t* pd = (uint64_t*)P2V(pdpt[pdpte] & PAGE_ADDR_MASK);
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if ((pd[pde] & flags) != flags)
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{
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if (!(pd[pde] & Flags::Present))
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pd[pde] = V2P(allocate_page_aligned_page());
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pd[pde] = (pd[pde] & PAGE_ADDR_MASK) | flags;
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}
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uint64_t* pt = (uint64_t*)P2V(pd[pde] & PAGE_ADDR_MASK);
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pt[pte] = paddr | flags;
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}
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void PageTable::map_range_at(paddr_t paddr, vaddr_t vaddr, size_t size, flags_t flags)
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{
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LockGuard _(m_lock);
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ASSERT(is_canonical(vaddr));
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ASSERT(paddr % PAGE_SIZE == 0);
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ASSERT(vaddr % PAGE_SIZE == 0);
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size_t first_page = vaddr / PAGE_SIZE;
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size_t last_page = (vaddr + size - 1) / PAGE_SIZE;
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size_t page_count = last_page - first_page + 1;
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for (size_t page = 0; page < page_count; page++)
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map_page_at(paddr + page * PAGE_SIZE, vaddr + page * PAGE_SIZE, flags);
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}
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uint64_t PageTable::get_page_data(vaddr_t vaddr) const
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{
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LockGuard _(m_lock);
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ASSERT(is_canonical(vaddr));
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vaddr = uncanonicalize(vaddr);
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ASSERT(vaddr % PAGE_SIZE == 0);
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uint64_t pml4e = (vaddr >> 39) & 0x1FF;
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uint64_t pdpte = (vaddr >> 30) & 0x1FF;
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uint64_t pde = (vaddr >> 21) & 0x1FF;
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uint64_t pte = (vaddr >> 12) & 0x1FF;
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uint64_t* pml4 = (uint64_t*)P2V(m_highest_paging_struct);
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if (!(pml4[pml4e] & Flags::Present))
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return 0;
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uint64_t* pdpt = (uint64_t*)P2V(pml4[pml4e] & PAGE_ADDR_MASK);
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if (!(pdpt[pdpte] & Flags::Present))
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return 0;
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uint64_t* pd = (uint64_t*)P2V(pdpt[pdpte] & PAGE_ADDR_MASK);
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if (!(pd[pde] & Flags::Present))
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return 0;
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uint64_t* pt = (uint64_t*)P2V(pd[pde] & PAGE_ADDR_MASK);
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if (!(pt[pte] & Flags::Present))
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return 0;
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return pt[pte];
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}
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PageTable::flags_t PageTable::get_page_flags(vaddr_t addr) const
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{
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return get_page_data(addr) & PAGE_FLAG_MASK;
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}
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paddr_t PageTable::physical_address_of(vaddr_t addr) const
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{
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return get_page_data(addr) & PAGE_ADDR_MASK;
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}
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vaddr_t PageTable::get_free_page() const
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{
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LockGuard _(m_lock);
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// Try to find free page that can be mapped without
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// allocations (page table with unused entries)
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uint64_t* pml4 = (uint64_t*)P2V(m_highest_paging_struct);
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for (uint64_t pml4e = 0; pml4e < 512; pml4e++)
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{
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if (!(pml4[pml4e] & Flags::Present))
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continue;
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uint64_t* pdpt = (uint64_t*)P2V(pml4[pml4e] & PAGE_ADDR_MASK);
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for (uint64_t pdpte = 0; pdpte < 512; pdpte++)
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{
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if (!(pdpt[pdpte] & Flags::Present))
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continue;
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uint64_t* pd = (uint64_t*)P2V(pdpt[pdpte] & PAGE_ADDR_MASK);
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for (uint64_t pde = 0; pde < 512; pde++)
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{
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if (!(pd[pde] & Flags::Present))
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continue;
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uint64_t* pt = (uint64_t*)P2V(pd[pde] & PAGE_ADDR_MASK);
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for (uint64_t pte = !(pml4e + pdpte + pde); pte < 512; pte++)
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{
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if (!(pt[pte] & Flags::Present))
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{
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vaddr_t vaddr = 0;
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vaddr |= pml4e << 39;
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vaddr |= pdpte << 30;
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vaddr |= pde << 21;
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vaddr |= pte << 12;
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return canonicalize(vaddr);
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}
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}
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}
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}
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}
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// Find any free page page (except for page 0)
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vaddr_t vaddr = PAGE_SIZE;
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while ((vaddr >> 48) == 0)
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{
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if (!(get_page_flags(vaddr) & Flags::Present))
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return vaddr;
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vaddr += PAGE_SIZE;
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}
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ASSERT_NOT_REACHED();
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}
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vaddr_t PageTable::get_free_contiguous_pages(size_t page_count) const
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{
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LockGuard _(m_lock);
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for (vaddr_t vaddr = PAGE_SIZE; !(vaddr >> 48); vaddr += PAGE_SIZE)
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{
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bool valid { true };
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for (size_t page = 0; page < page_count; page++)
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{
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if (get_page_flags(vaddr + page * PAGE_SIZE) & Flags::Present)
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{
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vaddr += page * PAGE_SIZE;
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valid = false;
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break;
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}
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}
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if (valid)
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return vaddr;
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}
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ASSERT_NOT_REACHED();
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}
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bool PageTable::is_page_free(vaddr_t page) const
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{
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ASSERT(page % PAGE_SIZE == 0);
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return !(get_page_flags(page) & Flags::Present);
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}
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bool PageTable::is_range_free(vaddr_t start, size_t size) const
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{
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LockGuard _(m_lock);
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vaddr_t first_page = start / PAGE_SIZE;
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vaddr_t last_page = (start + size - 1) / PAGE_SIZE;
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for (vaddr_t page = first_page; page <= last_page; page++)
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if (!is_page_free(page * PAGE_SIZE))
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return false;
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return true;
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}
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}
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