A20, E820h, Real Mode Emulation

1 files changed, 49 insertions, 0 deletions

diff --git a/src/loader/gdt.c b/src/loader/gdt.c
new file mode 100644
index 0000000..853b793
--- /dev/null
+++ b/src/loader/gdt.c
@@ -0,0 +1,49 @@
+// MIT License, Copyright (c) 2021 Marvin Borner
+
+#include <gdt.h>
+
+static struct gdt_desc gdt_descs[] = { { 0 },
+
+				       { .limit = 0xffff,
+					 .base_low = 0x0000,
+					 .base_mid = 0x00,
+					 .access = 0x9a,
+					 .granularity = 0x00,
+					 .base_hi = 0x00 },
+
+				       { .limit = 0xffff,
+					 .base_low = 0x0000,
+					 .base_mid = 0x00,
+					 .access = 0x92,
+					 .granularity = 0x00,
+					 .base_hi = 0x00 },
+
+				       { .limit = 0xffff,
+					 .base_low = 0x0000,
+					 .base_mid = 0x00,
+					 .access = 0x9a,
+					 .granularity = 0xcf,
+					 .base_hi = 0x00 },
+
+				       { .limit = 0xffff,
+					 .base_low = 0x0000,
+					 .base_mid = 0x00,
+					 .access = 0x92,
+					 .granularity = 0xcf,
+					 .base_hi = 0x00 },
+
+				       { .limit = 0x0000,
+					 .base_low = 0x0000,
+					 .base_mid = 0x00,
+					 .access = 0x9a,
+					 .granularity = 0x20,
+					 .base_hi = 0x00 },
+
+				       { .limit = 0x0000,
+					 .base_low = 0x0000,
+					 .base_mid = 0x00,
+					 .access = 0x92,
+					 .granularity = 0x00,
+					 .base_hi = 0x00 } };
+
+REAL struct gdtr gdt = { sizeof(gdt_descs) - 1, (u32)gdt_descs, 0 };