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Kernel: Stop taking MM lock while using regular quickmaps

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You're still required to disable interrupts though, as the mappings are
per-CPU. This exposed the fact that our CR3 lookup map is insufficiently
protected (but we'll address that in a separate commit.)
This commit is contained in:
Andreas Kling
2022-08-22 15:23:32 +02:00
parent c8375c51ff
commit 6cd3695761
5 changed files with 15 additions and 14 deletions
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8
Kernel/Memory/PageDirectory.cpp
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@@ -1,5 +1,5 @@
/*
* Copyright (c) 2018-2021, Andreas Kling <kling@serenityos.org>
* Copyright (c) 2018-2022, Andreas Kling <kling@serenityos.org>
*
* SPDX-License-Identifier: BSD-2-Clause
*/
@@ -7,6 +7,7 @@
#include <AK/Memory.h>
#include <AK/Singleton.h>
#include <Kernel/Arch/CPU.h>
#include <Kernel/Arch/InterruptDisabler.h>
#include <Kernel/Arch/PageDirectory.h>
#include <Kernel/Memory/MemoryManager.h>
#include <Kernel/Memory/PageDirectory.h>
@@ -29,9 +30,6 @@ ErrorOr<NonnullLockRefPtr<PageDirectory>> PageDirectory::try_create_for_userspac
{
auto directory = TRY(adopt_nonnull_lock_ref_or_enomem(new (nothrow) PageDirectory));
// NOTE: Take the MM lock since we need it for quickmap.
SpinlockLocker lock(s_mm_lock);
#if ARCH(X86_64)
directory->m_pml4t = TRY(MM.allocate_physical_page());
#endif
@@ -47,6 +45,7 @@ ErrorOr<NonnullLockRefPtr<PageDirectory>> PageDirectory::try_create_for_userspac
#if ARCH(X86_64)
{
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();
@@ -54,6 +53,7 @@ ErrorOr<NonnullLockRefPtr<PageDirectory>> PageDirectory::try_create_for_userspac
#endif
{
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]) {