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Kernel: Create page structures correctly in boot.s

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This commit is contained in:
etaIneLp 2020-05-25 17:19:37 -04:00 • committed by Andreas Kling
parent 4e607192c7
commit 826dc94187
3 changed files with 76 additions and 100 deletions
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70
Kernel/VM/MemoryManager.cpp
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@ -62,8 +62,6 @@ MemoryManager::MemoryManager()
m_kernel_page_directory = PageDirectory::create_kernel_page_directory();
parse_memory_map();
write_cr3(kernel_page_directory().cr3());
setup_low_identity_mapping();
setup_low_pseudo_identity_mapping();
protect_kernel_image();
m_shared_zero_page = allocate_user_physical_page();
@ -73,36 +71,6 @@ MemoryManager::~MemoryManager()
{
}
void MemoryManager::setup_low_pseudo_identity_mapping()
{
// This code switches the pseudo-identity mapping (8 first MB above 3G mark) from 2MB pages to 4KB pages.
// The boot code sets it up as 2MB huge pages for convenience. But we need 4KB pages to be able to protect
// the kernel soon!
for (size_t i = 0; i < 4; ++i) {
m_low_pseudo_identity_mapping_pages[i] = allocate_supervisor_physical_page();
FlatPtr base = i * (2 * MB);
auto* page_table = (PageTableEntry*)quickmap_page(*m_low_pseudo_identity_mapping_pages[i]);
for (size_t j = 0; j < 512; ++j) {
auto& pte = page_table[j];
pte.set_physical_page_base(base + j * PAGE_SIZE);
pte.set_writable(true);
pte.set_present(true);
pte.set_execute_disabled(false);
pte.set_user_allowed(false);
}
unquickmap_page();
}
auto* pd = quickmap_pd(*m_kernel_page_directory, 3);
for (size_t i = 0; i < 4; ++i) {
pd[i].set_huge(false);
pd[i].set_page_table_base(m_low_pseudo_identity_mapping_pages[i]->paddr().get());
}
flush_entire_tlb();
}
void MemoryManager::protect_kernel_image()
{
// Disable writing to the kernel text and rodata segments.
@ -120,34 +88,6 @@ void MemoryManager::protect_kernel_image()
}
}
void MemoryManager::setup_low_identity_mapping()
{
m_low_page_table = allocate_user_physical_page(ShouldZeroFill::Yes);
auto* pd_zero = quickmap_pd(kernel_page_directory(), 0);
pd_zero[1].set_present(false);
pd_zero[2].set_present(false);
pd_zero[3].set_present(false);
auto& pde_zero = pd_zero[0];
pde_zero.set_page_table_base(m_low_page_table->paddr().get());
pde_zero.set_present(true);
pde_zero.set_huge(false);
pde_zero.set_writable(true);
pde_zero.set_user_allowed(false);
if (g_cpu_supports_nx)
pde_zero.set_execute_disabled(true);
for (FlatPtr offset = (1 * MB); offset < (2 * MB); offset += PAGE_SIZE) {
auto& page_table_page = m_low_page_table;
auto& pte = quickmap_pt(page_table_page->paddr())[offset / PAGE_SIZE];
pte.set_physical_page_base(offset);
pte.set_user_allowed(false);
pte.set_present(offset != 0);
pte.set_writable(offset < (1 * MB));
}
}
void MemoryManager::parse_memory_map()
{
RefPtr<PhysicalRegion> region;
@ -574,11 +514,11 @@ void MemoryManager::flush_tlb(VirtualAddress vaddr)
: "memory");
}
extern "C" PageTableEntry boot_pd3_pde1023_pt[1024];
extern "C" PageTableEntry boot_pd3_pt1023[1024];
PageDirectoryEntry* MemoryManager::quickmap_pd(PageDirectory& directory, size_t pdpt_index)
{
auto& pte = boot_pd3_pde1023_pt[4];
auto& pte = boot_pd3_pt1023[4];
auto pd_paddr = directory.m_directory_pages[pdpt_index]->paddr();
if (pte.physical_page_base() != pd_paddr.as_ptr()) {
#ifdef MM_DEBUG
@ -595,7 +535,7 @@ PageDirectoryEntry* MemoryManager::quickmap_pd(PageDirectory& directory, size_t
PageTableEntry* MemoryManager::quickmap_pt(PhysicalAddress pt_paddr)
{
auto& pte = boot_pd3_pde1023_pt[8];
auto& pte = boot_pd3_pt1023[8];
if (pte.physical_page_base() != pt_paddr.as_ptr()) {
#ifdef MM_DEBUG
dbg() << "quickmap_pt: Mapping P" << (void*)pt_paddr.as_ptr() << " at 0xffe08000 in pte @ " << &pte;
@ -615,7 +555,7 @@ u8* MemoryManager::quickmap_page(PhysicalPage& physical_page)
ASSERT(!m_quickmap_in_use);
m_quickmap_in_use = true;
auto& pte = boot_pd3_pde1023_pt[0];
auto& pte = boot_pd3_pt1023[0];
if (pte.physical_page_base() != physical_page.paddr().as_ptr()) {
#ifdef MM_DEBUG
dbg() << "quickmap_page: Mapping P" << (void*)physical_page.paddr().as_ptr() << " at 0xffe00000 in pte @ " << &pte;
@ -633,7 +573,7 @@ void MemoryManager::unquickmap_page()
{
ASSERT_INTERRUPTS_DISABLED();
ASSERT(m_quickmap_in_use);
auto& pte = boot_pd3_pde1023_pt[0];
auto& pte = boot_pd3_pt1023[0];
pte.clear();
flush_tlb(VirtualAddress(0xffe00000));
m_quickmap_in_use = false;