[BOOT] Multiboot compliant kernel which runs 64 bit code

kernel/include/gdt.h

@@ -0,0 +1,12 @@
+#pragma once
+
+#define   GDT_WRITE      (1<<41)
+#define   GDT_EXECUTE    (1<<43)
+#define   GDT_CODEDATA   (1<<44)
+#define   GDT_PRESENT    (1<<47)
+#define   GDT_64BIT      (1<<53)
+
+#ifndef __ASSEMBLER__
+#include <stdint.h>
+extern uint64_t BootGDT;
+#endif

kernel/include/mem.h

@@ -0,0 +1,27 @@
+#pragma once
+
+#define KERNEL_OFFSET 0xFFFFFF8000000000
+
+#ifdef __ASSEMBLER__
+  #define V2P(a) ((a) - KERNEL_OFFSET)
+  #define P2V(a) ((a) + KERNEL_OFFSET)
+  #define P1_OFFSET(p) (((p) >> 12) & 0x1FF)
+  #define P2_OFFSET(p) (((p) >> 21) & 0x1FF)
+  #define P3_OFFSET(p) (((p) >> 30) & 0x1FF)
+  #define P4_OFFSET(p) (((p) >> 39) & 0x1FF)
+#else
+  #include <stdint.h>
+  #define V2P(a) ((uintptr_t)(a) - KERNEL_OFFSET)
+  #define P2V(a) ((void *)((uintptr_t)(a) + KERNEL_OFFSET))
+#endif
+
+// Paging
+#define   PAGE_PRESENT        0x001
+#define   PAGE_WRITE          0x002
+#define   PAGE_USER           0x004
+#define   PAGE_WRITETHROUGH   0x008
+#define   PAGE_NOCACHE        0x010
+#define   PAGE_ACCESSED       0x020
+#define   PAGE_DIRTY          0x040
+#define   PAGE_HUGE           0x080
+#define   PAGE_GLOBAL         0x100

kernel/include/multiboot.h

@@ -0,0 +1,14 @@
+#pragma once
+#define MBOOT1_MAGIC 0x1BADB002
+#define MBOOT1_MAGIC2 0x2BADB002
+#define MBOOT1_FLAG_PAGE_ALIGN 0x01
+#define MBOOT1_FLAG_MEM_INFO 0x02
+#define MBOOT1_HEADER_FLAGS (MBOOT1_FLAG_PAGE_ALIGN | MBOOT1_FLAG_MEM_INFO)
+#define MBOOT1_HEADER_CHECKSUM -(MBOOT1_HEADER_FLAGS + MBOOT1_MAGIC)
+
+#define MBOOT2_MAGIC 0xE85250D6
+#define MBOOT2_MAGIC2 0x36D76289
+#define MBOOT2_ARCH 0
+#define MBOOT2_LENGTH (MultiBootHeaderEnd - MultiBootHeader)
+#define MBOOT2_CHECKSUM -(MBOOT2_MAGIC + MBOOT2_ARCH + MBOOT2_LENGTH)
+