tasking: continue working on page directory switching

include/paging.h

@@ -41,6 +41,8 @@ extern uint32_t *kpage_dir;
 void grub_memory_map(unsigned int magic, struct multiboot_info* mbi);
 uint32_t* get_page_dir();
 void set_page_dir(uint32_t new_page_dir);
+uint32_t phys_to_virt(uint32_t phys);
+uint32_t create_page_dir();
 void enablePaging();
 void loadPageDirectory(uint32_t* page_directory);
 

src/mm/paging.c

@@ -123,6 +123,29 @@ void set_page_dir(uint32_t new_page_dir) {
     asm volatile("mov %0, %%cr3" : : "r" (new_page_dir));
 }
 
+uint32_t phys_to_virt(uint32_t phys)
+{
+    return phys+0xC0000000;
+}
+
+uint32_t create_page_dir()
+{
+    void* ppp = alloc_page();
+    memset(ppp, 0, 0x1000);
+
+    uint32_t* current_pd = (uint32_t*)0xFFFFF000;  // Current PD (self-mapped)
+    uint32_t* new_pd = (uint32_t*)phys_to_virt((uint32_t)ppp);
+
+    for(int i = 768; i < 1023; i++)
+    {
+        new_pd[i] = current_pd[i];
+    }
+
+    new_pd[1023] = (uint32_t)ppp | 0x03;  // Present + Read/Write
+
+    return (uint32_t)new_pd;
+}
+
 void enablePaging() {
     asm volatile (
         "mov %%cr0, %%eax\n"

src/tasking/switch.asm

@@ -32,6 +32,9 @@ switchProcess:
     mov esp, [edx + 4]      ; esp = next_process_ptr->kesp
     mov [current], edx      ; current = next_process_ptr
 
+    mov eax, [edx + 40]
+    mov cr3, eax
+
     pop edi
     pop esi
     pop ebx

src/tasking/task.c

@@ -71,7 +71,7 @@ Process* task_create(uint32_t func, void** args, uint32_t arg_count, uint32_t ri
     p->context->eip = (uint32_t)trapret;
     p->kesp = (uint32_t)sp;
 
-    p->page_directory = kpage_dir;
+    p->page_directory = ring == 0 ? kpage_dir : (uint32_t*)create_page_dir();
 
     p->next = 0;