mm: Add comments

Author: coditva

kernel/kernel.c

@@ -62,13 +62,19 @@ extern void kmain(multiboot_info_t *multiboot_info, uint32_t multiboot_magic)
     uintptr_t *  addr1 = (void *)0x00400000;
     uintptr_t *  addr2 = addr1 + 1024;
 
+    /* map both addresses to same physical memory page */
     paging_map_page(page, addr1, 0x02);
     paging_map_page(page, addr2, 0x02);
 
+    /* update the values at both addresses */
     *addr1 = 0xcafebabe;
     *addr2 = 0xdeadbeef;
+
+    /* the second update should overwrite the first since the physical address
+     * is same */
     kcheck(*addr1 == *addr2, "paging enabled");
 
+    /* cleanup */
     paging_unmap_page(page, addr1);
     paging_unmap_page(page, addr2);
     page_free(page);

kernel/mm/page_alloc.c

@@ -31,6 +31,8 @@ void page_alloc_init()
   size_t pages_array_page_count =
     page_address_to_index(pages_array_mem_size) + 1;
 
+  /* we have some unused memory at this point but we'll ignore it for now */
+
   /* allocate the pages for the array */
   pages = page_frame_n_alloc(pages_array_page_count);
 

kernel/mm/paging.c

@@ -188,7 +188,8 @@ int paging_map_page(struct page *page, void *virtual_address, uint32_t flags)
   page_table[page_tab_index].present = 1;
 
   klog(LOG_DEBUG,
-       "paging_map_page: new table entry: 0x%x\n",
+       "paging_map_page: new table entry: 0x%x 0x%x\n",
+       &page_table[page_tab_index],
        page_table_get_value(&page_table[page_tab_index]));
 
   /* increment the number of references for the page */