kernel: Move Thread::self_directory to UserVM

Since this is only used by user threads, UserVM is a convenient/related place to store the PageDirectory in a RAII manner.

kernel/src/memory/UserVM.cpp

@@ -15,6 +15,8 @@ Result<OwnedPtr<UserVM>> UserVM::try_create()
     TRY(ptr->create_null_region());
     TRY(ptr->create_default_region());
 
+    ptr->m_directory = TRY(MMU::create_page_directory_for_userspace());
+
     return move(ptr);
 }
 
@@ -54,6 +56,8 @@ Result<OwnedPtr<UserVM>> UserVM::clone()
         ptr->m_regions.append(new_region);
     }
 
+    ptr->m_directory = TRY(MMU::clone_userspace_page_directory(m_directory));
+
     return move(ptr);
 }
 
@@ -61,6 +65,19 @@ UserVM::UserVM()
 {
 }
 
+UserVM& UserVM::operator=(UserVM&& other)
+{
+    if (&other == this) return *this;
+
+    m_regions.consume([](VMRegion* region) { delete region; });
+    MMU::delete_userspace_page_directory(m_directory);
+
+    m_regions = other.m_regions;
+    m_directory = other.m_directory;
+
+    return *this;
+}
+
 Result<u64> UserVM::alloc_region(usize count, bool persistent)
 {
     for (auto* region = m_regions.expect_last(); region; region = m_regions.previous(region).value_or(nullptr))
@@ -198,4 +215,5 @@ Result<VMRegion*> UserVM::split_region(VMRegion* parent, u64 boundary)
 UserVM::~UserVM()
 {
     m_regions.consume([](VMRegion* region) { delete region; });
+    MMU::delete_userspace_page_directory(m_directory);
 }

kernel/src/memory/UserVM.h

@@ -1,4 +1,5 @@
 #pragma once
+#include "arch/MMU.h"
 #include <luna/LinkedList.h>
 #include <luna/OwnedPtr.h>
 #include <luna/Result.h>
@@ -19,6 +20,8 @@ class UserVM
     UserVM();
     ~UserVM();
 
+    UserVM& operator=(UserVM&& other);
+
     Result<u64> alloc_region(usize count, bool persistent = false);
 
     Result<bool> test_and_alloc_region(u64 address, usize count, bool persistent = false)
@@ -35,6 +38,11 @@ class UserVM
 
     Result<OwnedPtr<UserVM>> clone();
 
+    PageDirectory* page_directory() const
+    {
+        return m_directory;
+    }
+
   private:
     Result<bool> set_region(u64 address, usize count, bool used, bool persistent);
     Result<void> create_default_region();
@@ -43,4 +51,5 @@ class UserVM
     void merge_contiguous_regions(VMRegion* a, VMRegion* b);
     Result<VMRegion*> split_region(VMRegion* parent, u64 boundary);
     LinkedList<VMRegion> m_regions;
+    PageDirectory* m_directory;
 };

kernel/src/sys/exec.cpp

@@ -70,7 +70,7 @@ Result<u64> sys_execve(Registers* regs, SyscallArgs args)
     kdbgln("exec: attempting to replace current image with %s", path.chars());
 #endif
 
-    auto guard = make_scope_guard([current] { MMU::switch_page_directory(current->self_directory); });
+    auto guard = make_scope_guard([current] { MMU::switch_page_directory(current->self_directory()); });
 
     auto image = TRY(ThreadImage::try_load_from_elf(inode));
 
@@ -99,8 +99,6 @@ Result<u64> sys_execve(Registers* regs, SyscallArgs args)
         }
     }
 
-    MMU::delete_userspace_page_directory(current->self_directory);
-
     if (VFS::is_setuid(inode)) current->auth.euid = current->auth.suid = inode->uid();
     if (VFS::is_setgid(inode)) current->auth.egid = current->auth.sgid = inode->gid();
 
@@ -108,7 +106,7 @@ Result<u64> sys_execve(Registers* regs, SyscallArgs args)
 
     image->apply(current);
 
-    MMU::switch_page_directory(current->self_directory);
+    MMU::switch_page_directory(current->self_directory());
 
     current->set_arguments(user_argc, user_argv, user_envc, user_envp);
 
@@ -123,7 +121,7 @@ Result<u64> sys_fork(Registers* regs, SyscallArgs)
 {
     auto current = Scheduler::current();
 
-    auto guard = make_scope_guard([current] { MMU::switch_page_directory(current->self_directory); });
+    auto guard = make_scope_guard([current] { MMU::switch_page_directory(current->self_directory()); });
 
     memcpy(&current->regs, regs, sizeof(*regs));
 

kernel/src/thread/Scheduler.cpp

@@ -191,8 +191,6 @@ namespace Scheduler
             }
         }
 
-        if (!thread->is_kernel) MMU::delete_userspace_page_directory(thread->self_directory);
-
         delete thread;
 
         CPU::enable_interrupts();

kernel/src/thread/Thread.h

@@ -97,7 +97,11 @@ struct Thread : public LinkedListNode<Thread>
     Thread* parent { nullptr };
     Option<pid_t> child_being_waited_for = {};
 
-    PageDirectory* self_directory;
+    PageDirectory* self_directory() const
+    {
+        return vm_allocator->page_directory();
+    }
+
     PageDirectory* active_directory { nullptr };
 
     [[noreturn]] void exit_and_signal_parent(u8 status);

kernel/src/thread/ThreadImage.cpp

@@ -36,14 +36,9 @@ Result<OwnedPtr<ThreadImage>> ThreadImage::try_load_from_elf(SharedPtr<VFS::Inod
 
     auto old_directory = MMU::get_page_directory();
 
-    auto new_directory = TRY(MMU::create_page_directory_for_userspace());
+    MMU::switch_page_directory(vm_allocator->page_directory());
 
-    MMU::switch_page_directory(new_directory);
-
-    auto guard = make_scope_guard([=] {
-        MMU::delete_userspace_page_directory(new_directory);
-        MMU::switch_page_directory(old_directory);
-    });
+    auto guard = make_scope_guard([=] { MMU::switch_page_directory(old_directory); });
 
     const ELFData data = TRY(ELFLoader::load(inode, vm_allocator.ptr()));
 
@@ -53,7 +48,6 @@ Result<OwnedPtr<ThreadImage>> ThreadImage::try_load_from_elf(SharedPtr<VFS::Inod
 
     guard.deactivate();
 
-    image->m_directory = new_directory;
     image->m_kernel_stack = kernel_stack;
     image->m_user_stack = user_stack;
     image->m_loaded_image_data = data;
@@ -69,14 +63,11 @@ Result<OwnedPtr<ThreadImage>> ThreadImage::clone_from_thread(Thread* parent)
 
     auto vm_allocator = TRY(parent->vm_allocator->clone());
 
-    auto new_directory = TRY(MMU::clone_userspace_page_directory(parent->self_directory));
-
     const ELFData data = { .entry = parent->ip() };
 
     const u64 kernel_stack_base = TRY(MemoryManager::alloc_for_kernel(4, MMU::ReadWrite | MMU::NoExecute));
     Stack kernel_stack { kernel_stack_base, 4 * ARCH_PAGE_SIZE };
 
-    image->m_directory = new_directory;
     image->m_kernel_stack = kernel_stack;
     image->m_user_stack = parent->stack;
     image->m_loaded_image_data = data;
@@ -124,8 +115,7 @@ void ThreadImage::apply(Thread* thread)
     thread->stack = m_user_stack;
     thread->set_sp(align_down<16>(m_sp));
 
-    thread->self_directory = m_directory;
-    thread->active_directory = m_directory;
+    thread->active_directory = m_vm_allocator->page_directory();
 
     thread->vm_allocator = move(m_vm_allocator);
 }

kernel/src/thread/ThreadImage.h

@@ -29,7 +29,6 @@ class ThreadImage
 
   private:
     OwnedPtr<UserVM> m_vm_allocator;
-    PageDirectory* m_directory { nullptr };
     Stack m_user_stack;
     Stack m_kernel_stack;
     ELFData m_loaded_image_data;