Kernel: Protect the PageDirectory from concurrent access

fleximus · Nov 11, 2020 · 5b38132 · 5b38132
1 parent 2b25a89
commit 5b38132
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Showing 4 changed files with 14 additions and 3 deletions.
diff --git a/Kernel/VM/MemoryManager.cpp b/Kernel/VM/MemoryManager.cpp
@@ -87,6 +87,7 @@ MemoryManager::~MemoryManager()
 
 void MemoryManager::protect_kernel_image()
 {
+ ScopedSpinLock page_lock(kernel_page_directory().get_lock());
  // Disable writing to the kernel text and rodata segments.
  for (size_t i = (FlatPtr)&start_of_kernel_text; i < (FlatPtr)&start_of_kernel_data; i += PAGE_SIZE) {
  auto& pte = *ensure_pte(kernel_page_directory(), VirtualAddress(i));
@@ -193,10 +194,11 @@ void MemoryManager::parse_memory_map()
  ASSERT(m_user_physical_pages > 0);
 }
 
-PageTableEntry* MemoryManager::pte(const PageDirectory& page_directory, VirtualAddress vaddr)
+PageTableEntry* MemoryManager::pte(PageDirectory& page_directory, VirtualAddress vaddr)
 {
  ASSERT_INTERRUPTS_DISABLED();
  ASSERT(s_mm_lock.own_lock());
+ ASSERT(page_directory.get_lock().own_lock());
  u32 page_directory_table_index = (vaddr.get() >> 30) & 0x3;
  u32 page_directory_index = (vaddr.get() >> 21) & 0x1ff;
  u32 page_table_index = (vaddr.get() >> 12) & 0x1ff;
@@ -213,6 +215,7 @@ PageTableEntry* MemoryManager::ensure_pte(PageDirectory& page_directory, Virtual
 {
  ASSERT_INTERRUPTS_DISABLED();
  ASSERT(s_mm_lock.own_lock());
+ ASSERT(page_directory.get_lock().own_lock());
  u32 page_directory_table_index = (vaddr.get() >> 30) & 0x3;
  u32 page_directory_index = (vaddr.get() >> 21) & 0x1ff;
  u32 page_table_index = (vaddr.get() >> 12) & 0x1ff;
@@ -259,6 +262,7 @@ void MemoryManager::release_pte(PageDirectory& page_directory, VirtualAddress va
 {
  ASSERT_INTERRUPTS_DISABLED();
  ASSERT(s_mm_lock.own_lock());
+ ASSERT(page_directory.get_lock().own_lock());
  u32 page_directory_table_index = (vaddr.get() >> 30) & 0x3;
  u32 page_directory_index = (vaddr.get() >> 21) & 0x1ff;
  u32 page_table_index = (vaddr.get() >> 12) & 0x1ff;

diff --git a/Kernel/VM/MemoryManager.h b/Kernel/VM/MemoryManager.h
@@ -191,7 +191,7 @@ class MemoryManager {
  PageDirectoryEntry* quickmap_pd(PageDirectory&, size_t pdpt_index);
  PageTableEntry* quickmap_pt(PhysicalAddress);
 
- PageTableEntry* pte(const PageDirectory&, VirtualAddress);
+ PageTableEntry* pte(PageDirectory&, VirtualAddress);
  PageTableEntry* ensure_pte(PageDirectory&, VirtualAddress);
  void release_pte(PageDirectory&, VirtualAddress, bool);
 

diff --git a/Kernel/VM/PageDirectory.h b/Kernel/VM/PageDirectory.h
@@ -57,6 +57,8 @@ class PageDirectory : public RefCounted<PageDirectory> {
  Process* process() { return m_process; }
  const Process* process() const { return m_process; }
 
+ RecursiveSpinLock& get_lock() { return m_lock; }
+
 private:
  PageDirectory(Process&, const RangeAllocator* parent_range_allocator);
  PageDirectory();
@@ -67,6 +69,7 @@ class PageDirectory : public RefCounted<PageDirectory> {
  RefPtr<PhysicalPage> m_directory_table;
  RefPtr<PhysicalPage> m_directory_pages[4];
  HashMap<u32, RefPtr<PhysicalPage>> m_page_tables;
+ RecursiveSpinLock m_lock;
 };
 
 }
diff --git a/Kernel/VM/Region.cpp b/Kernel/VM/Region.cpp
@@ -229,6 +229,7 @@ Bitmap& Region::ensure_cow_map() const
 
 bool Region::map_individual_page_impl(size_t page_index)
 {
+ ASSERT(m_page_directory->get_lock().own_lock());
  auto page_vaddr = vaddr_from_page_index(page_index);
  auto* pte = MM.ensure_pte(*m_page_directory, page_vaddr);
  if (!pte) {
@@ -260,8 +261,9 @@ bool Region::map_individual_page_impl(size_t page_index)
 
 bool Region::remap_page(size_t page_index, bool with_flush)
 {
- ASSERT(m_page_directory);
  ScopedSpinLock lock(s_mm_lock);
+ ASSERT(m_page_directory);
+ ScopedSpinLock page_lock(m_page_directory->get_lock());
  ASSERT(physical_page(page_index));
  bool success = map_individual_page_impl(page_index);
  if (with_flush)
@@ -273,6 +275,7 @@ void Region::unmap(ShouldDeallocateVirtualMemoryRange deallocate_range)
 {
  ScopedSpinLock lock(s_mm_lock);
  ASSERT(m_page_directory);
+ ScopedSpinLock page_lock(m_page_directory->get_lock());
  size_t count = page_count();
  for (size_t i = 0; i < count; ++i) {
  auto vaddr = vaddr_from_page_index(i);
@@ -302,6 +305,7 @@ void Region::set_page_directory(PageDirectory& page_directory)
 bool Region::map(PageDirectory& page_directory)
 {
  ScopedSpinLock lock(s_mm_lock);
+ ScopedSpinLock page_lock(page_directory.get_lock());
  set_page_directory(page_directory);
 #ifdef MM_DEBUG
  dbg() << "MM: Region::map() will map VMO pages " << first_page_index() << " - " << last_page_index() << " (VMO page count: " << vmobject().page_count() << ")";