Moving components modules to a more proper directory

components/gdt/gdt.c

@@ -0,0 +1,43 @@
+#include "gdt.h"
+// Congirures a given gdt entry base on the entry index given
+void gdt_configure_entry(u32 entry, u32 base, u32 limit, u8 access, u8 gran) {
+	// base address
+	gdt_entries[entry].low_base = (base & 0xffff);
+	gdt_entries[entry].middle_base = (base >> 16) & 0xff;
+	gdt_entries[entry].high_base = (base >> 24) & 0xff;
+
+	// descriptor limits
+	gdt_entries[entry].low_limit = (limit & 0xffff);
+	gdt_entries[entry].granular = ((limit >> 16) & 0x0f);
+
+	gdt_entries[entry].granular |= (gran & 0xf0);
+	gdt_entries[entry].access = access;
+}
+
+// Configure the gdt pointer desribed in gdt.h as type GDT_PTR
+void gdt_configure() {
+	// gdt_ptr configuration
+	gdt_ptr.size = (sizeof(struct GDT_Entry) * NO_GDT_ENTRIES) - 1;
+
+	// First entry is just the null descriptor and is left along overall
+	gdt_configure_entry(0, 0, 0, 0, 0);
+
+	// Second entry: code segment base adders
+	// Base address: 0 
+	// limit: 4GB
+	// Granularity: 4KB
+	// 32-bit opcodes
+	// Code segment selector
+	gdt_configure_entry(1, 0, 0xffffffff, 0x9a, 0xcf); // code segment
+
+	// Finally the data segment
+	// All the same except the desriptor type specifies that its data
+	gdt_configure_entry(2, 0, 0xffffffff, 0x92, 0xcf); // data segment
+
+	// user mode segments
+	gdt_configure_entry(3, 0, 0xffffffff, 0xfa, 0xcf);
+	gdt_configure_entry(4, 0, 0xffffffff, 0xf2, 0xcf);
+
+	// Load in the new changes to the gdt
+	load_gdt();
+}

components/gdt/gdt.h

@@ -0,0 +1,32 @@
+#ifndef GDT_H
+#define GDT_H
+#include "types.h"
+
+#define NO_GDT_ENTRIES 5
+
+struct GDT_Entry {
+	u16 low_limit;
+	u16 low_base;
+	u8 middle_base;
+	u8 access;
+	u8 granular;
+	u8 high_base;
+}__attribute__((packed));
+
+// Contains the pointer to the first gdt entry as well as the size(of the whole table(?))
+struct GDT_PTR {
+	u16 size;
+	u32 address;
+}__attribute__((packed));
+
+struct GDT_Entry gdt_entries[NO_GDT_ENTRIES];
+struct GDT_PTR gdt_ptr;
+
+// this func is actually taken care of in gdt_seg.s
+extern void load_gdt();
+
+void gdt_configure_entry(u32 entry, u32 base, u32 limit, u8 access, u8 gran);
+
+void gdt_configure();
+
+#endif

components/gdt/gdt_seg.s

@@ -0,0 +1,17 @@
+global load_gdt
+extern gdt_ptr
+
+load_gdt:
+	mov ax, 0x10 	; offset in the gdt to our data segment
+	mov ds, ax
+	mov es, ax
+	mov fs, ax
+	mov gs, ax
+	mov ss, ax
+	jmp 0x08:flush_cs ; far jump to the code segment
+
+flush_cs:
+	lgdt [gdt_ptr]
+	ret 
+
+