1 files changed, 53 insertions, 0 deletions
diff --git a/kernel/src/cpu/gdt.c b/kernel/src/cpu/gdt.c
new file mode 100644
index 0000000..b4f1ec0
--- /dev/null
+++ b/kernel/src/cpu/gdt.c
@@ -0,0 +1,53 @@
+#include <gdt.h>
+#include <tss.h>
+
+gdt_seg_entry gdt[7];
+gdt_p gdt_pointer;
+
+void add_gdt_entry(uint32_t num, uint32_t offset, uint32_t limit, uint8_t access, uint8_t flags)
+{
+	gdt[num].offset1 = offset & 0xffff;
+	gdt[num].offset2 = (offset >> 16) & 0xff;
+	gdt[num].offset3 = (uint8_t)(offset >> 24) & 0xff;
+	gdt[num].limit = limit & 0xffff;
+	gdt[num].limitflags = (limit >> 16) & 0xf;
+	gdt[num].access = access;
+	gdt[num].limitflags = flags << 4;
+}
+
+void add_gdt_tss(uint32_t num, uint64_t offset, uint32_t limit, uint8_t access, uint8_t flags)
+{
+	add_gdt_entry(num, offset & 0xffffffff, limit, access, flags);
+}
+
+void reload_gdt()
+{
+	__asm__ volatile (
+			"mov $0x10, %ax;"
+			"mov %ax, %ds;"
+			"mov %ax, %es;"
+			"mov %ax, %ss;"
+			);
+}
+
+void load_gdt(gdt_p* pointer)
+{
+	__asm__ volatile ("lgdt (%0);" : : "r"(pointer) : );
+	reload_gdt();
+}
+
+void init_gdt()
+{
+	gdt_pointer.offset = (uint64_t)&gdt;
+	gdt_pointer.size = sizeof(gdt) - 1;
+
+	add_gdt_entry(0, 0, 0, 0, 0);
+	add_gdt_entry(1, 0, 0xfffff, 0x9a, 0xa);
+	add_gdt_entry(2, 0, 0xfffff, 0x92, 0xc);
+	add_gdt_entry(3, 0, 0xfffff, 0xfa, 0xa);
+	add_gdt_entry(4, 0, 0xfffff, 0xf2, 0xc);
+	add_gdt_tss(5, (uint64_t)&tss, sizeof(tss_type), 0x89, 0);
+
+	load_gdt(&gdt_pointer);
+	init_tss();
+}