Advance HH, GDT, IDT (details below)

- Implement higher-half in loader with paging (using 4Mb pages)
- Add GDT installation code
- Add IDT installation code (spend a loong time debugging the ISRs!)
- Add CDROM generation scripts
- Add scripts to launch bochs (debug) and qemu (debug)

1 files changed, 35 insertions, 0 deletions

diff --git a/kernel/l0/gdt.c b/kernel/l0/gdt.c
new file mode 100644
index 0000000..9ed5210
--- /dev/null
+++ b/kernel/l0/gdt.c
@@ -0,0 +1,35 @@
+#include <gdt.h>
+#include <string.h>
+
+#define GDT_ENTRIES 6	// The contents of each entry is defined in gdt_init.
+
+static gdt_entry_t gdt_entries[GDT_ENTRIES];
+static gdt_ptr_t gdt_ptr;
+
+/*	For internal use only. Writes one entry of the GDT with given parameters. */
+static void gdt_setGate(int num, uint32_t base, uint32_t limit, uint8_t access, uint8_t gran) {
+	gdt_entries[num].base_low = (base & 0xFFFF);
+	gdt_entries[num].base_middle = (base >> 16) & 0xFF;
+	gdt_entries[num].base_high = (base >> 24) & 0xFF;
+
+	gdt_entries[num].limit_low = (limit & 0xFFFF);
+	gdt_entries[num].granularity = (limit >> 16) & 0x0F;
+	gdt_entries[num].granularity |= gran & 0xF0;
+	gdt_entries[num].access = access;
+}
+
+/*	Write data to the GDT and enable it. */
+void gdt_init() {
+	gdt_ptr.limit = (sizeof(gdt_entry_t) * GDT_ENTRIES) - 1;
+	gdt_ptr.base = (uint32_t)&gdt_entries;
+
+	gdt_setGate(0, 0, 0, 0, 0);					//Null segment
+	gdt_setGate(1, 0, 0xFFFFFFFF, 0x9A, 0xCF);	//Kernel code segment	0x08
+	gdt_setGate(2, 0, 0xFFFFFFFF, 0x92, 0xCF);	//Kernel data segment	0x10
+	gdt_setGate(3, 0, 0xFFFFFFFF, 0xFA, 0xCF);	//User code segment		0x18
+	gdt_setGate(4, 0, 0xFFFFFFFF, 0xF2, 0xCF);	//User data segment		0x20
+
+	asm volatile ("lgdt %0"::"m"(gdt_ptr):"memory");
+}
+
+/* vim: set ts=4 sw=4 tw=0 noet :*/