Kernel: Store a pointer to the owner process in PageDirectory

This replaces the previous owning address space pointer. This commit
should not change any of the existing functionality, but it lays down
the groundwork needed to let us properly access the region table under
the address space spinlock during page fault handling.

Kernel/Arch/aarch64/PageDirectory.cpp

@@ -62,10 +62,12 @@ UNMAP_AFTER_INIT NonnullLockRefPtr<PageDirectory> PageDirectory::must_create_ker
     return adopt_lock_ref_if_nonnull(new (nothrow) PageDirectory).release_nonnull();
 }
 
-ErrorOr<NonnullLockRefPtr<PageDirectory>> PageDirectory::try_create_for_userspace()
+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_root_table = TRY(MM.allocate_physical_page());
 
     directory->m_directory_table = TRY(MM.allocate_physical_page());

Kernel/Arch/aarch64/PageDirectory.h

@@ -179,7 +179,7 @@ class PageDirectory final : public AtomicRefCounted<PageDirectory> {
     friend class MemoryManager;
 
 public:
-    static ErrorOr<NonnullLockRefPtr<PageDirectory>> try_create_for_userspace();
+    static ErrorOr<NonnullLockRefPtr<PageDirectory>> try_create_for_userspace(Process&);
     static NonnullLockRefPtr<PageDirectory> must_create_kernel_page_directory();
     static LockRefPtr<PageDirectory> find_current();
 
@@ -197,10 +197,7 @@ public:
         return m_root_table;
     }
 
-    AddressSpace* address_space() { return m_space; }
-    AddressSpace const* address_space() const { return m_space; }
-
-    void set_space(Badge<AddressSpace>, AddressSpace& space) { m_space = &space; }
+    Process* process() { return m_process; }
 
     RecursiveSpinlock<LockRank::None>& get_lock() { return m_lock; }
 
@@ -212,7 +209,7 @@ private:
     static void register_page_directory(PageDirectory* directory);
     static void deregister_page_directory(PageDirectory* directory);
 
-    AddressSpace* m_space { nullptr };
+    Process* m_process { nullptr };
     RefPtr<PhysicalPage> m_root_table;
     RefPtr<PhysicalPage> m_directory_table;
     RefPtr<PhysicalPage> m_directory_pages[512];

Kernel/Arch/x86_64/PageDirectory.cpp

@@ -61,10 +61,12 @@ UNMAP_AFTER_INIT NonnullLockRefPtr<PageDirectory> PageDirectory::must_create_ker
     return adopt_lock_ref_if_nonnull(new (nothrow) PageDirectory).release_nonnull();
 }
 
-ErrorOr<NonnullLockRefPtr<PageDirectory>> PageDirectory::try_create_for_userspace()
+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());

Kernel/Arch/x86_64/PageDirectory.h

@@ -162,7 +162,7 @@ class PageDirectory final : public AtomicRefCounted<PageDirectory> {
     friend class MemoryManager;
 
 public:
-    static ErrorOr<NonnullLockRefPtr<PageDirectory>> try_create_for_userspace();
+    static ErrorOr<NonnullLockRefPtr<PageDirectory>> try_create_for_userspace(Process& process);
     static NonnullLockRefPtr<PageDirectory> must_create_kernel_page_directory();
     static LockRefPtr<PageDirectory> find_current();
 
@@ -180,10 +180,7 @@ public:
         return m_pml4t;
     }
 
-    AddressSpace* address_space() { return m_space; }
-    AddressSpace const* address_space() const { return m_space; }
-
-    void set_space(Badge<AddressSpace>, AddressSpace& space) { m_space = &space; }
+    Process* process() { return m_process; }
 
     RecursiveSpinlock<LockRank::None>& get_lock() { return m_lock; }
 
@@ -195,7 +192,7 @@ private:
     static void register_page_directory(PageDirectory* directory);
     static void deregister_page_directory(PageDirectory* directory);
 
-    AddressSpace* m_space { nullptr };
+    Process* m_process { nullptr };
     RefPtr<PhysicalPage> m_pml4t;
     RefPtr<PhysicalPage> m_directory_table;
     RefPtr<PhysicalPage> m_directory_pages[512];

Kernel/Memory/AddressSpace.cpp

@@ -19,9 +19,9 @@
 
 namespace Kernel::Memory {
 
-ErrorOr<NonnullOwnPtr<AddressSpace>> AddressSpace::try_create(AddressSpace const* parent)
+ErrorOr<NonnullOwnPtr<AddressSpace>> AddressSpace::try_create(Process& process, AddressSpace const* parent)
 {
-    auto page_directory = TRY(PageDirectory::try_create_for_userspace());
+    auto page_directory = TRY(PageDirectory::try_create_for_userspace(process));
 
     VirtualRange total_range = [&]() -> VirtualRange {
         if (parent)
@@ -33,9 +33,7 @@ ErrorOr<NonnullOwnPtr<AddressSpace>> AddressSpace::try_create(AddressSpace const
         return VirtualRange(VirtualAddress { base }, userspace_range_ceiling - base);
     }();
 
-    auto space = TRY(adopt_nonnull_own_or_enomem(new (nothrow) AddressSpace(move(page_directory), total_range)));
-    space->page_directory().set_space({}, *space);
-    return space;
+    return adopt_nonnull_own_or_enomem(new (nothrow) AddressSpace(move(page_directory), total_range));
 }
 
 AddressSpace::AddressSpace(NonnullLockRefPtr<PageDirectory> page_directory, VirtualRange total_range)

Kernel/Memory/AddressSpace.h

@@ -21,7 +21,7 @@ namespace Kernel::Memory {
 
 class AddressSpace {
 public:
-    static ErrorOr<NonnullOwnPtr<AddressSpace>> try_create(AddressSpace const* parent);
+    static ErrorOr<NonnullOwnPtr<AddressSpace>> try_create(Process&, AddressSpace const* parent);
     ~AddressSpace();
 
     PageDirectory& page_directory() { return *m_page_directory; }

Kernel/Memory/MemoryManager.cpp

@@ -722,8 +722,11 @@ Region* MemoryManager::find_region_from_vaddr(VirtualAddress vaddr)
     auto page_directory = PageDirectory::find_current();
     if (!page_directory)
         return nullptr;
-    VERIFY(page_directory->address_space());
-    return find_user_region_from_vaddr(*page_directory->address_space(), vaddr);
+    auto* process = page_directory->process();
+    VERIFY(process);
+    return process->address_space().with([&](auto& space) {
+        return find_user_region_from_vaddr(*space, vaddr);
+    });
 }
 
 PageFaultResponse MemoryManager::handle_page_fault(PageFault const& fault)

Kernel/Process.cpp

@@ -286,20 +286,22 @@ void Process::unprotect_data()
 
 ErrorOr<Process::ProcessAndFirstThread> Process::create(NonnullOwnPtr<KString> name, UserID uid, GroupID gid, ProcessID ppid, bool is_kernel_process, RefPtr<Custody> current_directory, RefPtr<Custody> executable, RefPtr<TTY> tty, Process* fork_parent)
 {
-    OwnPtr<Memory::AddressSpace> new_address_space;
-    if (fork_parent) {
-        TRY(fork_parent->address_space().with([&](auto& parent_address_space) -> ErrorOr<void> {
-            new_address_space = TRY(Memory::AddressSpace::try_create(parent_address_space.ptr()));
-            return {};
-        }));
-    } else {
-        new_address_space = TRY(Memory::AddressSpace::try_create(nullptr));
-    }
     auto unveil_tree = UnveilNode { TRY(KString::try_create("/"sv)), UnveilMetadata(TRY(KString::try_create("/"sv))) };
     auto exec_unveil_tree = UnveilNode { TRY(KString::try_create("/"sv)), UnveilMetadata(TRY(KString::try_create("/"sv))) };
     auto credentials = TRY(Credentials::create(uid, gid, uid, gid, uid, gid, {}, fork_parent ? fork_parent->sid() : 0, fork_parent ? fork_parent->pgid() : 0));
 
     auto process = TRY(adopt_nonnull_ref_or_enomem(new (nothrow) Process(move(name), move(credentials), ppid, is_kernel_process, move(current_directory), move(executable), tty, move(unveil_tree), move(exec_unveil_tree))));
+
+    OwnPtr<Memory::AddressSpace> new_address_space;
+    if (fork_parent) {
+        TRY(fork_parent->address_space().with([&](auto& parent_address_space) -> ErrorOr<void> {
+            new_address_space = TRY(Memory::AddressSpace::try_create(*process, parent_address_space.ptr()));
+            return {};
+        }));
+    } else {
+        new_address_space = TRY(Memory::AddressSpace::try_create(*process, nullptr));
+    }
+
     auto first_thread = TRY(process->attach_resources(new_address_space.release_nonnull(), fork_parent));
 
     return ProcessAndFirstThread { move(process), move(first_thread) };

Kernel/Syscalls/execve.cpp

@@ -488,7 +488,7 @@ ErrorOr<void> Process::do_exec(NonnullRefPtr<OpenFileDescription> main_program_d
     auto new_process_name = TRY(KString::try_create(last_part));
     auto new_main_thread_name = TRY(new_process_name->try_clone());
 
-    auto allocated_space = TRY(Memory::AddressSpace::try_create(nullptr));
+    auto allocated_space = TRY(Memory::AddressSpace::try_create(*this, nullptr));
     OwnPtr<Memory::AddressSpace> old_space;
     auto& new_space = m_space.with([&](auto& space) -> Memory::AddressSpace& {
         old_space = move(space);