kernel: mm: virtual_mm: Init

2 files changed, 85 insertions, 0 deletions

diff --git a/kernel/include/mm/virtual_mm.h b/kernel/include/mm/virtual_mm.h
new file mode 100644
index 0000000..9806c4c
--- /dev/null
+++ b/kernel/include/mm/virtual_mm.h
@@ -0,0 +1,58 @@
+/*
+ * 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/>.
+ */
+
+#ifndef __mm_virtual_mm_h
+#define __mm_virtual_mm_h
+
+#define PAGE_SIZE (4096 * KiB)
+#define PAGE_DIRECTORY_SIZE 1024
+#define PAGE_TABLE_SIZE 1024
+
+#define PDE_PRESENT 1
+#define PDE_WRITABLE (1 << 2)
+#define PDE_USER (1 << 2)
+#define PDE_WRITETHROUGH (1 << 3)
+#define PDE_CACHE_DISABLE (1 << 4)
+#define PDE_ACCESSED (1 << 5)
+/* Never set (reserved by Intel) */
+#define PDE_RESERVED (0 << 6)
+#define PDE_PAGE_SIZE (1 << 7)
+#define PDE_GLOBAL (1 << 8)
+/* NOTE: Unused by the CPU, free to be used by us! */
+#define PDE_UNUSED(x) (x << 11)
+/* Page table address */
+#define PDE_FRAME(x) (x << 31)
+
+#define PTE_PRESENT 1
+#define PTE_WRITABLE (1 << 2)
+#define PTE_USER (1 << 2)
+#define PTE_WRITETHROUGH (1 << 3)
+#define PTE_CACHE_DISABLE (1 << 4)
+#define PTE_ACCESSED (1 << 5)
+#define PTE_DIRTY (1 << 6)
+#define PTE_PAT (1 << 7)
+#define PTE_GLOBAL (1 << 8)
+/* NOTE: Unused by the CPU, free to be used by us! */
+#define PTE_UNUSED(x) (x << 11)
+/* MAX: 0xFFFFF000 */
+#define PTE_FRAME(x) (x << 31)
+
+#define ADD_ATTRIB(entry, attribute) (entry |= attribute)
+#define SET_FRAME(entry, frame) (PTE_ADD_ATRIB(PTE_FRAME(frame)))
+
+#endif
diff --git a/kernel/mm/virtual_mm/virtual_mm.c b/kernel/mm/virtual_mm/virtual_mm.c
new file mode 100644
index 0000000..278a491
--- /dev/null
+++ b/kernel/mm/virtual_mm/virtual_mm.c
@@ -0,0 +1,27 @@
+/*
+ * 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 <stdint.h>
+
+#include <mm/virtual_mm.h>
+
+extern uint32_t kernel_start;
+extern uint32_t kernel_end;
+
+uint32_t page_directory[PAGE_DIRECTORY_SIZE];
+uint32_t initial_page_table[PAGE_TABLE_SIZE];