Prepare for cloning address spaces, not there yet

kernel/include/memory/AddressSpace.h

@@ -7,13 +7,21 @@ struct AddressSpace
 
     void destroy();
 
-    void reset();
+    void detach();
+
+    AddressSpace clone();
 
     PageTable* get_pml4()
     {
         return m_pml4;
     }
 
+    bool is_cloned()
+    {
+        return m_cloned;
+    }
+
   private:
     PageTable* m_pml4;
+    bool m_cloned;
 };

kernel/include/thread/Scheduler.h

@@ -10,7 +10,8 @@ namespace Scheduler
     void exit(int status);
     void sleep(unsigned long ms);
     void add_kernel_task(void (*task)(void));
-    void add_user_task(void* task);
+
+    Task* create_user_task();
 
     void load_user_task(const char* filename);
 

kernel/src/memory/AddressSpace.cpp

@@ -15,6 +15,11 @@ AddressSpace AddressSpace::create()
 
 void AddressSpace::destroy()
 {
+    if (m_cloned)
+    {
+        kdbgln("Will not destroy a cloned address space, I don't own it");
+        return;
+    }
     uint64_t pages_freed = 0;
     for (int i = 0; i < 512; i++)
     {
@@ -71,60 +76,18 @@ void AddressSpace::destroy()
     kdbgln("Reclaimed %ld pages from address space!", pages_freed);
 }
 
-void AddressSpace::reset()
+void AddressSpace::detach()
 {
-    uint64_t pages_freed = 0;
-    for (int i = 0; i < 512; i++)
-    {
-        PageDirectoryEntry& pdp_pde = m_pml4->entries[i];
-        if (!pdp_pde.present) continue;
-        if (pdp_pde.larger_pages)
-        {
-            pages_freed++;
-            PMM::free_page((void*)pdp_pde.get_address());
-            continue;
-        }
-        PageTable* pdp = (PageTable*)pdp_pde.get_address();
-        for (int j = 0; j < 511; j++) // skip the last page directory, it's the kernel one
-        {
-            PageDirectoryEntry& pd_pde = pdp->entries[j];
-            if (!pd_pde.present) continue;
-            if (pd_pde.larger_pages)
-            {
-                pages_freed++;
-                PMM::free_page((void*)pd_pde.get_address());
-                continue;
-            }
-            PageTable* pd = (PageTable*)pd_pde.get_address();
-            for (int k = 0; k < 512; k++)
-            {
-                PageDirectoryEntry& pt_pde = pd->entries[k];
-                if (!pt_pde.present) continue;
-                if (pt_pde.larger_pages)
-                {
-                    pages_freed++;
-                    PMM::free_page((void*)pt_pde.get_address());
-                    continue;
-                }
-                PageTable* pt = (PageTable*)pt_pde.get_address();
-                for (int l = 0; l < 512; l++)
-                {
-                    PageDirectoryEntry& pde = pt->entries[l];
-                    if (!pde.present) continue;
-                    pages_freed++;
-                    PMM::free_page((void*)pde.get_address());
-                }
-                pages_freed++;
-                PMM::free_page(pt);
-            }
-            pages_freed++;
-            PMM::free_page(pd);
-        }
-        pages_freed++;
-        PMM::free_page(pdp);
-    }
-
+    if (!m_cloned) return;
+    m_pml4 = (PageTable*)PMM::request_page();
     VMM::install_kernel_page_directory_into_address_space(*this);
+    m_cloned = false;
+}
 
-    kdbgln("Reclaimed %ld pages from address space!", pages_freed);
+AddressSpace AddressSpace::clone()
+{
+    AddressSpace result;
+    result.m_pml4 = m_pml4;
+    result.m_cloned = true;
+    return result;
 }

kernel/src/sys/exec.cpp

@@ -75,10 +75,6 @@ void sys_exec(Context* context, const char* pathname)
 
     // At this point, pretty much nothing can fail.
 
-    // task->address_space.reset();
-
-    // VMM::switch_to_user_address_space(task->address_space);
-
     ELFImage* image = ELFLoader::load_elf_from_vfs(program);
     ASSERT(image); // If check_elf_image succeeded, load_elf_from_vfs MUST succeed, unless something has gone terribly
                    // wrong.

kernel/src/thread/Scheduler.cpp

@@ -87,21 +87,16 @@ void Scheduler::add_kernel_task(void (*task)(void))
             new_task->id, new_task->regs.rsp, task_num);
 }
 
-void Scheduler::add_user_task(void* task)
+Task* Scheduler::create_user_task()
 {
     Task* new_task = new Task;
     ASSERT(new_task);
     memset(&new_task->regs, 0, sizeof(Context));
     new_task->user_task = true;
     new_task->id = free_tid++;
-    new_task->regs.rip = (uint64_t)task;
     new_task->allocated_stack = (uint64_t)MemoryManager::get_pages(
         TASK_PAGES_IN_STACK, MAP_READ_WRITE | MAP_USER); // 16 KB is enough for everyone, right?
     new_task->regs.rsp = get_top_of_stack(new_task->allocated_stack, TASK_PAGES_IN_STACK);
-    new_task->regs.cs = 0x18 | 0x03;
-    new_task->regs.ss = 0x20 | 0x03;
-    new_task->regs.ds = 0x20 | 0x03;
-    new_task->regs.rflags = (1 << 21) | (1 << 9); // enable interrupts
     new_task->task_sleep = 0;
     new_task->task_time = 0;
     new_task->cpu_time = 0;
@@ -110,10 +105,7 @@ void Scheduler::add_user_task(void* task)
     base_task->prev_task = new_task;
     new_task->next_task = base_task;
     end_task = new_task;
-    new_task->state = new_task->Running;
     task_num++;
-    kinfoln("Adding user task: starts at %lx, tid %ld, stack at %lx, total tasks: %ld", new_task->regs.rip,
-            new_task->id, new_task->regs.rsp, task_num);
 }
 
 void Scheduler::load_user_task(const char* filename)