From 1966047921e2958469f9faac1bd1f56d1fc5587a Mon Sep 17 00:00:00 2001
From: Anton Kling <anton@kling.gg>
Date: Mon, 13 Nov 2023 19:16:31 +0100
Subject: Memory: Fix problem where certain tables did not get marked as
 kernel.

This caused the tables to be cloned instead of having the pointer copied
on the new page directory creations.

This is just a solution to the symptom of having a bad design for
memory managment. Maybe I will figure out something better.
---
 kernel/arch/i386/mmu.c | 17 +++++++----------
 1 file changed, 7 insertions(+), 10 deletions(-)

(limited to 'kernel/arch')

diff --git a/kernel/arch/i386/mmu.c b/kernel/arch/i386/mmu.c
index 4ac17da..b403c8b 100644
--- a/kernel/arch/i386/mmu.c
+++ b/kernel/arch/i386/mmu.c
@@ -41,7 +41,7 @@ void *ksbrk(size_t s) {
   }
   // Determine whether we are approaching a unallocated table
   int table_index = 1 + (rc / (1024 * 0x1000));
-  if (!active_directory->tables[table_index]) {
+  if (!kernel_directory->tables[table_index]) {
     u32 physical;
     active_directory->tables[table_index] = (PageTable *)0xDEADBEEF;
     active_directory->tables[table_index] =
@@ -248,7 +248,7 @@ PageDirectory *clone_directory(PageDirectory *original) {
   new_directory->physical_address = physical_address + offset;
 
   for (int i = 0; i < 1024; i++) {
-    if (!original->tables[i]) {
+    if (!original->tables[i] && !kernel_directory->tables[i]) {
       new_directory->tables[i] = NULL;
       new_directory->physical_tables[i] = (u32)NULL;
       continue;
@@ -263,8 +263,9 @@ PageDirectory *clone_directory(PageDirectory *original) {
       continue;
     }
 
-    //    if (original->tables[i] == kernel_directory->tables[i]) {
-    if (i > 641) {
+    if (original->tables[i] == kernel_directory->tables[i] || i > 641) {
+      if (original->tables[i])
+        assert(kernel_directory->tables[i]);
       new_directory->tables[i] = kernel_directory->tables[i];
       new_directory->physical_tables[i] = kernel_directory->physical_tables[i];
       continue;
@@ -282,11 +283,7 @@ PageDirectory *clone_directory(PageDirectory *original) {
 void mmu_allocate_shared_kernel_region(void *rc, size_t n) {
   size_t num_pages = n / PAGE_SIZE;
   for (size_t i = 0; i <= num_pages; i++) {
-    Page *p = get_page((void *)(rc + i * 0x1000), NULL, PAGE_NO_ALLOCATE, 0);
-    if (!p) {
-      kprintf("don't have: %x\n", rc + i * 0x1000);
-      p = get_page((void *)(rc + i * 0x1000), NULL, PAGE_ALLOCATE, 0);
-    }
+    Page *p = get_page((void *)(rc + i * 0x1000), NULL, PAGE_ALLOCATE, 0);
     if (!p->present || !p->frame)
       allocate_frame(p, 0, 1);
   }
@@ -336,7 +333,7 @@ void *mmu_map_frames(void *const ptr, size_t s) {
   void *const r = mmu_find_unallocated_virtual_range((void *)0xEF000000, s);
   size_t num_pages = s / 0x1000;
   for (size_t i = 0; i <= num_pages; i++) {
-    Page *p = get_page((void *)(r + i * 0x1000), NULL, PAGE_ALLOCATE, 1);
+    Page *p = get_page((void *)(r + i * 0x1000), NULL, PAGE_ALLOCATE, 0);
     assert(p);
     int rw = 1;
     int is_kernel = 1;
-- 
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