From 57d2931b96decb77da9cd62116aa800d3b6adcf7 Mon Sep 17 00:00:00 2001
From: Ruslan Isaev <ubijca16@gmail.com>
Date: Wed, 5 Nov 2025 20:52:58 +0300
Subject: [PATCH] mm: fix mapping memory in non-present PDEs

---
 src/kernel/kernel.c  |  2 +-
 src/mm/page_tables.c | 21 ++++++++++++++++-----
 src/mm/paging.c      |  2 +-
 3 files changed, 18 insertions(+), 7 deletions(-)

diff --git a/src/kernel/kernel.c b/src/kernel/kernel.c
index 13fd8e5..3d87ec6 100644
--- a/src/kernel/kernel.c
+++ b/src/kernel/kernel.c
@@ -134,7 +134,7 @@ void kmain(unsigned int magic, unsigned int info)
 	l9660_dir dir;
 	l9660_file file;
 
-	follow_path("/katau/caller.", &file, &dir);
+	follow_path("/katau/dash.", &file, &dir);
 
 	exec_from_file(&file, &dir);
 
diff --git a/src/mm/page_tables.c b/src/mm/page_tables.c
index c4c3bdc..80a157e 100644
--- a/src/mm/page_tables.c
+++ b/src/mm/page_tables.c
@@ -48,11 +48,22 @@ void map_page(void *physaddr, void *virtualaddr, unsigned int flags) {
     // adjust the PDE accordingly.
 
     if (!(pd[pdindex] & 0x1)) { // If PDE not present
-        unsigned long *new_pt = alloc_page();
-        unsigned long *virt_pt = (unsigned long *)(0xC0000000 + new_pt);
-        memset(virt_pt, 0, 4096);
-        //pd[pdindex] = (uint32_t)new_pt | 0x3; // Present, R/W
-        pd[pdindex] = (uint32_t)new_pt | (flags & 0x7); // Add User bit if needed
+        void *new_pt_phys = alloc_page();
+        if (!new_pt_phys) {
+            printf("failed to allocate a new page table\n");
+            return;
+        }
+
+        unsigned int pde_flags = PAGE_PRESENT | PAGE_RW;
+        if (flags & PAGE_USER) {
+            pde_flags |= PAGE_USER;
+        }
+        pd[pdindex] = (unsigned long)new_pt_phys | pde_flags;
+
+        uint32_t *pt_virt = (uint32_t*)(0xFFC00000 + (pdindex << 12));
+        asm volatile("invlpg (%0)" : : "r" (pt_virt) : "memory");
+
+        memset(pt_virt, 0, 4096);
     }
 
     uint32_t *pt = (uint32_t*)(0xFFC00000 + (pdindex << 12));
diff --git a/src/mm/paging.c b/src/mm/paging.c
index 467eeb3..91325b4 100644
--- a/src/mm/paging.c
+++ b/src/mm/paging.c
@@ -138,7 +138,7 @@ uint32_t* create_page_dir()
     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++)
+    for(int i = 768; i < 1024; i++)
     {
         if(current_pd[i] & PAGE_PRESENT) {
             new_pd[i] = current_pd[i];