kernel: Move gdt to its own subdirectory

1 files changed, 51 insertions, 0 deletions

diff --git a/kernel/boot/gdt/gdt.c b/kernel/boot/gdt/gdt.c
new file mode 100644
index 0000000..4644b3d
--- /dev/null
+++ b/kernel/boot/gdt/gdt.c
@@ -0,0 +1,51 @@
+/*
+ * CMOS
+ * Copyright (C) 2024-2025 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 <kernel/io.h>
+
+#include <boot/gdt.h>
+
+GDT_entry GDT[] = {
+  /* NULL Descriptor */
+  GDT_ENTRY(0, 0, 0, 0),
+
+  /* Kernel Mode Code Segment */
+  GDT_ENTRY(0, 0xfffff, KERNEL_CODE_SEGMENT_ACCESS_FLAGS, FLAGS),
+
+  /* Kernel Mode Data Segment */
+  GDT_ENTRY(0, 0xfffff, KERNEL_DATA_SEGMENT_ACCESS_FLAGS, FLAGS),
+
+  /* User Mode Code Segment */
+  GDT_ENTRY(0, 0xfffff, USER_CODE_SEGMENT_ACCESS_FLAGS, FLAGS),
+
+  /* User Mode Data Segment */
+  GDT_ENTRY(0, 0xfffff, USER_DATA_SEGMENT_ACCESS_FLAGS, FLAGS)
+
+  /* TODO: TSS? */
+  /* TODO: LDT? */
+};
+
+GDT_descriptor g_GDT_descriptor = { sizeof(GDT_entry) * 5 - 1, &GDT[0] };
+
+void
+GDT_load(void)
+{
+  _GDT_flush(&g_GDT_descriptor);
+}