1 files changed, 74 insertions, 0 deletions
diff --git a/kernel/mm/virtual_mm/page_table_allocator.cc b/kernel/mm/virtual_mm/page_table_allocator.cc
new file mode 100644
index 0000000..3ec4896
--- /dev/null
+++ b/kernel/mm/virtual_mm/page_table_allocator.cc
@@ -0,0 +1,74 @@
+/*
+ * bubbl
+ * Copyright (C) 2025  Raghuram Subramani <raghus2247@gmail.com>
+ *
+ * This program is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation, either version 3 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program.  If not, see <http://www.gnu.org/licenses/>.
+ */
+
+#include <common.h>
+#include <kernel/halt.h>
+#include <libk/stdio.h>
+#include <mm/page_table_allocator.h>
+#include <mm/physical_mm.h>
+#include <mm/virtual_mm.h>
+#include <stddef.h>
+
+namespace PageTableAllocator
+{
+
+uint32_t *l_page_directory = 0;
+uint32_t *l_heap = NULL;
+uint16_t l_table_index = 0;
+
+static void
+make_table(uint32_t *table_address)
+{
+  uint32_t *table = table_address;
+  for (uint32_t i = 0; i < 1024; i++)
+    table[i] = PTE_FRAME((uint32_t) PhysicalMM::allocate_block())
+               | PTE_PRESENT(1) | PTE_WRITABLE(1);
+
+  void *starting_address = VirtualMM::find_free_addresses(4 * KiB);
+  uint32_t *pd_entry = &l_page_directory[GET_PD_INDEX(starting_address)];
+  *pd_entry = PDE_FRAME((uint32_t) table) | PDE_PRESENT(1) | PDE_WRITABLE(1);
+
+  l_heap = (uint32_t *) starting_address;
+  l_table_index = 0;
+}
+
+void
+prepare(void)
+{
+  if (l_page_directory != VirtualMM::get_page_directory())
+    l_page_directory = VirtualMM::get_page_directory();
+
+  /* Initial table */
+  if (l_heap == NULL)
+    make_table((uint32_t *) (7 * MiB));
+
+  /* If we're gonna run out of space, allocate a new table with the remaining
+   * page */
+  if (l_table_index == 1023)
+    make_table(allocate());
+}
+
+uint32_t *
+allocate(void)
+{
+  uint32_t *next_table = l_heap + (l_table_index * 4 * KiB);
+  l_table_index++;
+  return next_table;
+}
+
+}