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/*
* Copyright (c) 2018-2021, Andreas Kling <kling@serenityos.org>
*
* SPDX-License-Identifier: BSD-2-Clause
*/
#include <AK/Memory.h>
#include <AK/Singleton.h>
#include <Kernel/Prekernel/Prekernel.h>
#include <Kernel/Process.h>
#include <Kernel/Random.h>
#include <Kernel/Sections.h>
#include <Kernel/VM/MemoryManager.h>
#include <Kernel/VM/PageDirectory.h>
extern u8 end_of_kernel_image[];
namespace Kernel {
static AK::Singleton<HashMap<FlatPtr, PageDirectory*>> s_cr3_map;
static HashMap<FlatPtr, PageDirectory*>& cr3_map()
{
VERIFY_INTERRUPTS_DISABLED();
return *s_cr3_map;
}
RefPtr<PageDirectory> PageDirectory::find_by_cr3(FlatPtr cr3)
{
ScopedSpinLock lock(s_mm_lock);
return cr3_map().get(cr3).value_or({});
}
UNMAP_AFTER_INIT PageDirectory::PageDirectory()
{
// make sure this starts in a new page directory to make MemoryManager::initialize_physical_pages() happy
FlatPtr start_of_range = ((FlatPtr)end_of_kernel_image & ~(FlatPtr)0x1fffff) + 0x200000;
m_range_allocator.initialize_with_range(VirtualAddress(start_of_range), KERNEL_PD_END - start_of_range);
m_identity_range_allocator.initialize_with_range(VirtualAddress(FlatPtr(0x00000000)), 0x00200000);
}
UNMAP_AFTER_INIT void PageDirectory::allocate_kernel_directory()
{
// Adopt the page tables already set up by boot.S
#if ARCH(X86_64)
dmesgln("MM: boot_pml4t @ {}", boot_pml4t);
m_pml4t = PhysicalPage::create(boot_pml4t, MayReturnToFreeList::No);
#endif
dmesgln("MM: boot_pdpt @ {}", boot_pdpt);
dmesgln("MM: boot_pd0 @ {}", boot_pd0);
dmesgln("MM: boot_pd_kernel @ {}", boot_pd_kernel);
m_directory_table = PhysicalPage::create(boot_pdpt, MayReturnToFreeList::No);
m_directory_pages[0] = PhysicalPage::create(boot_pd0, MayReturnToFreeList::No);
m_directory_pages[(kernel_base >> 30) & 0x1ff] = PhysicalPage::create(boot_pd_kernel, MayReturnToFreeList::No);
}
PageDirectory::PageDirectory(const RangeAllocator* parent_range_allocator)
{
constexpr FlatPtr userspace_range_base = 0x00800000;
FlatPtr userspace_range_ceiling = USER_RANGE_CEILING;
ScopedSpinLock lock(s_mm_lock);
if (parent_range_allocator) {
m_range_allocator.initialize_from_parent(*parent_range_allocator);
} else {
size_t random_offset = (get_fast_random<u8>() % 32 * MiB) & PAGE_MASK;
u32 base = userspace_range_base + random_offset;
m_range_allocator.initialize_with_range(VirtualAddress(base), userspace_range_ceiling - base);
}
// Set up a userspace page directory
#if ARCH(X86_64)
m_pml4t = MM.allocate_user_physical_page();
if (!m_pml4t)
return;
#endif
m_directory_table = MM.allocate_user_physical_page();
if (!m_directory_table)
return;
auto kernel_pd_index = (kernel_base >> 30) & 0x1ffu;
for (size_t i = 0; i < kernel_pd_index; i++) {
m_directory_pages[i] = MM.allocate_user_physical_page();
if (!m_directory_pages[i])
return;
}
// Share the top 1 GiB of kernel-only mappings (>=kernel_base)
m_directory_pages[kernel_pd_index] = MM.kernel_page_directory().m_directory_pages[kernel_pd_index];
#if ARCH(X86_64)
{
auto& table = *(PageDirectoryPointerTable*)MM.quickmap_page(*m_pml4t);
table.raw[0] = (FlatPtr)m_directory_table->paddr().as_ptr() | 7;
MM.unquickmap_page();
}
#endif
{
auto& table = *(PageDirectoryPointerTable*)MM.quickmap_page(*m_directory_table);
for (size_t i = 0; i < sizeof(m_directory_pages) / sizeof(m_directory_pages[0]); i++) {
if (m_directory_pages[i]) {
#if ARCH(I386)
table.raw[i] = (FlatPtr)m_directory_pages[i]->paddr().as_ptr() | 1;
#else
table.raw[i] = (FlatPtr)m_directory_pages[i]->paddr().as_ptr() | 7;
#endif
}
}
// 2 ** MAXPHYADDR - 1
// Where MAXPHYADDR = physical_address_bit_width
u64 max_physical_address = (1ULL << Processor::current().physical_address_bit_width()) - 1;
// bit 63 = no execute
// bit 7 = page size
// bit 5 = accessed
// bit 4 = cache disable
// bit 3 = write through
// bit 2 = user/supervisor
// bit 1 = read/write
// bit 0 = present
constexpr u64 pdpte_bit_flags = 0x80000000000000BF;
// This is to notify us of bugs where we're:
// 1. Going over what the processor is capable of.
// 2. Writing into the reserved bits (51:MAXPHYADDR), where doing so throws a GPF
// when writing out the PDPT pointer to CR3.
// The reason we're not checking the page directory's physical address directly is because
// we're checking for sign extension when putting it into a PDPTE. See issue #4584.
for (auto table_entry : table.raw)
VERIFY((table_entry & ~pdpte_bit_flags) <= max_physical_address);
MM.unquickmap_page();
}
// Clone bottom 2 MiB of mappings from kernel_page_directory
PageDirectoryEntry buffer;
auto* kernel_pd = MM.quickmap_pd(MM.kernel_page_directory(), 0);
memcpy(&buffer, kernel_pd, sizeof(PageDirectoryEntry));
auto* new_pd = MM.quickmap_pd(*this, 0);
memcpy(new_pd, &buffer, sizeof(PageDirectoryEntry));
// If we got here, we successfully created it. Set m_space now
m_valid = true;
cr3_map().set(cr3(), this);
}
PageDirectory::~PageDirectory()
{
ScopedSpinLock lock(s_mm_lock);
if (m_space)
cr3_map().remove(cr3());
}
}
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