Add multiboot 2 header file

src/arch/x86_64/multiboot_header.asm

@@ -0,0 +1,29 @@
+; Copyright 2015 Philipp Oppermann
+;
+; Licensed under the Apache License, Version 2.0 (the "License");
+; you may not use this file except in compliance with the License.
+; You may obtain a copy of the License at
+;
+;    http://www.apache.org/licenses/LICENSE-2.0
+;
+; Unless required by applicable law or agreed to in writing, software
+; distributed under the License is distributed on an "AS IS" BASIS,
+; WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+; See the License for the specific language governing permissions and
+; limitations under the License.
+
+section .multiboot
+header_start:
+    dd 0xe85250d6                ; magic number (multiboot 2)
+    dd 0                         ; architecture 0 (protected mode i386)
+    dd header_end - header_start ; header length
+    ; checksum
+    dd 0x100000000 - (0xe85250d6 + 0 + (header_end - header_start))
+
+    ; insert optional multiboot tags here
+
+    ; required end tag
+    dw 0    ; type
+    dw 0    ; flags
+    dd 8    ; size
+header_end: