From 9000d7644196f365232b7de947253d070e3575b4 Mon Sep 17 00:00:00 2001
From: Ruslan Isaev <ubijca16@gmail.com>
Date: Sat, 31 May 2025 19:43:38 +0300
Subject: [PATCH] tasking: continue working on page directory switching

---
 include/paging.h       |  2 ++
 src/mm/paging.c        | 23 +++++++++++++++++++++++
 src/tasking/switch.asm |  3 +++
 src/tasking/task.c     |  2 +-
 4 files changed, 29 insertions(+), 1 deletion(-)

diff --git a/include/paging.h b/include/paging.h
index 8131e02..40e5d31 100644
--- a/include/paging.h
+++ b/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);
 
diff --git a/src/mm/paging.c b/src/mm/paging.c
index 47867ab..73ccfad 100644
--- a/src/mm/paging.c
+++ b/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"
diff --git a/src/tasking/switch.asm b/src/tasking/switch.asm
index 12e79ca..9fd51cd 100644
--- a/src/tasking/switch.asm
+++ b/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
diff --git a/src/tasking/task.c b/src/tasking/task.c
index d872dca..75912ed 100644
--- a/src/tasking/task.c
+++ b/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;