1 files changed, 25 insertions, 0 deletions
diff --git a/arch/i386/lgdt.c b/arch/i386/lgdt.c
new file mode 100644
index 0000000..473a91d
--- /dev/null
+++ b/arch/i386/lgdt.c
@@ -0,0 +1,25 @@
+#include "gdt.h"
+
+struct __attribute__((packed)) Pointer {
+  uint16_t limit;
+  uint32_t base;
+};
+
+static struct SegmentDescriptor_t segments[8] __attribute__((aligned(32)));
+
+void
+gdt_install()
+{
+  const struct Pointer ptr = {sizeof(segments) - 1, (unsigned)&segments};
+  SegmentDescriptor(&segments[0], 0, 0, 0);             /* null segment */
+  SegmentDescriptor(&segments[2], 0, 0xffffffff, 0x9a); /* ktext segment */
+  SegmentDescriptor(&segments[3], 0, 0xffffffff, 0x92); /* kdata segment */
+
+  __asm__("lgdt (%0)" : : "a"(&ptr));
+
+  /* load the kernel data segment */
+  __asm__("mov %0, %%ds; mov %0, %%es; mov %0, %%fs; mov %0, %%gs; mov %0, %%ss" : : "ax"(kdataDescriptor));
+
+  /* load the kernel code segment */
+  __asm__("ljmp %0, $1f\n1:" : : "i"(ktextDescriptor));
+}