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/*
* Copyright (c) 2018-2022, Andreas Kling <kling@serenityos.org>
* Copyright (c) 2018-2022, James Mintram <me@jamesrm.com>
*
* SPDX-License-Identifier: BSD-2-Clause
*/
#include <AK/Singleton.h>
#include <Kernel/Arch/CPU.h>
#include <Kernel/Arch/PageDirectory.h>
#include <Kernel/InterruptDisabler.h>
#include <Kernel/Memory/MemoryManager.h>
#include <Kernel/Prekernel/Prekernel.h>
#include <Kernel/Sections.h>
#include <Kernel/Security/Random.h>
#include <Kernel/Tasks/Process.h>
#include <Kernel/Tasks/Thread.h>
namespace Kernel::Memory {
struct CR3Map {
SpinlockProtected<IntrusiveRedBlackTree<&PageDirectory::m_tree_node>, LockRank::None> map {};
};
static Singleton<CR3Map> s_cr3_map;
void PageDirectory::register_page_directory(PageDirectory* directory)
{
s_cr3_map->map.with([&](auto& map) {
map.insert(directory->cr3(), *directory);
});
}
void PageDirectory::deregister_page_directory(PageDirectory* directory)
{
s_cr3_map->map.with([&](auto& map) {
map.remove(directory->cr3());
});
}
LockRefPtr<PageDirectory> PageDirectory::find_current()
{
return s_cr3_map->map.with([&](auto& map) {
return map.find(read_cr3());
});
}
void activate_kernel_page_directory(PageDirectory const& pgd)
{
write_cr3(pgd.cr3());
}
void activate_page_directory(PageDirectory const& pgd, Thread* current_thread)
{
current_thread->regs().cr3 = pgd.cr3();
write_cr3(pgd.cr3());
}
UNMAP_AFTER_INIT NonnullLockRefPtr<PageDirectory> PageDirectory::must_create_kernel_page_directory()
{
return adopt_lock_ref_if_nonnull(new (nothrow) PageDirectory).release_nonnull();
}
ErrorOr<NonnullLockRefPtr<PageDirectory>> PageDirectory::try_create_for_userspace(Process& process)
{
auto directory = TRY(adopt_nonnull_lock_ref_or_enomem(new (nothrow) PageDirectory));
directory->m_process = &process;
directory->m_pml4t = TRY(MM.allocate_physical_page());
directory->m_directory_table = TRY(MM.allocate_physical_page());
auto kernel_pd_index = (kernel_mapping_base >> 30) & 0x1ffu;
for (size_t i = 0; i < kernel_pd_index; i++) {
directory->m_directory_pages[i] = TRY(MM.allocate_physical_page());
}
// Share the top 1 GiB of kernel-only mappings (>=kernel_mapping_base)
directory->m_directory_pages[kernel_pd_index] = MM.kernel_page_directory().m_directory_pages[kernel_pd_index];
{
InterruptDisabler disabler;
auto& table = *(PageDirectoryPointerTable*)MM.quickmap_page(*directory->m_pml4t);
table.raw[0] = (FlatPtr)directory->m_directory_table->paddr().as_ptr() | 7;
MM.unquickmap_page();
}
{
InterruptDisabler disabler;
auto& table = *(PageDirectoryPointerTable*)MM.quickmap_page(*directory->m_directory_table);
for (size_t i = 0; i < sizeof(m_directory_pages) / sizeof(m_directory_pages[0]); i++) {
if (directory->m_directory_pages[i]) {
table.raw[i] = (FlatPtr)directory->m_directory_pages[i]->paddr().as_ptr() | 7;
}
}
// 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();
}
register_page_directory(directory);
return directory;
}
PageDirectory::PageDirectory() = default;
UNMAP_AFTER_INIT void PageDirectory::allocate_kernel_directory()
{
// Adopt the page tables already set up by boot.S
dmesgln("MM: boot_pml4t @ {}", boot_pml4t);
m_pml4t = PhysicalPage::create(boot_pml4t, MayReturnToFreeList::No);
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_mapping_base >> 30) & 0x1ff] = PhysicalPage::create(boot_pd_kernel, MayReturnToFreeList::No);
}
PageDirectory::~PageDirectory()
{
if (is_cr3_initialized()) {
deregister_page_directory(this);
}
}
}
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