From aa71f8e70b06444b96ad009c6d5c611b32891396 Mon Sep 17 00:00:00 2001
From: Braiden Vasco <braiden-vasco@users.noreply.github.com>
Date: Wed, 1 Nov 2017 08:53:27 +0000
Subject: [PATCH] Support both Multiboot 1 and 2

---
 arch/Makefile  |  2 ++
 arch/boot.s    | 28 +++++++++++++++++++---------
 arch/linker.ld |  3 ++-
 3 files changed, 23 insertions(+), 10 deletions(-)

diff --git a/arch/Makefile b/arch/Makefile
index e9fc0af..5e9bf51 100644
--- a/arch/Makefile
+++ b/arch/Makefile
@@ -16,6 +16,8 @@ clean:
 
 kernel: $(OBJS)
 	$(CC) -T linker.ld -o $@ -ffreestanding -nostdlib -lgcc $(OBJS)
+	grub-file --is-x86-multiboot $@
+	grub-file --is-x86-multiboot2 $@
 
 %.c.o: %.c
 	$(CC) -c $< -o $@ -std=gnu99 -ffreestanding -fno-builtin -fno-stack-protector -Wall -Wextra -I$(I)
diff --git a/arch/boot.s b/arch/boot.s
index 2194064..3653c63 100644
--- a/arch/boot.s
+++ b/arch/boot.s
@@ -1,14 +1,24 @@
-.set ALIGN,    1<<0
-.set MEMINFO,  1<<1
-.set FLAGS,    ALIGN | MEMINFO
-.set MAGIC,    0x1BADB002
-.set CHECKSUM, -(MAGIC + FLAGS)
+.set MULTIBOOT_1_MAGIC, 0x1BADB002
+.set MULTIBOOT_1_FLAGS, (1 << 0) | (1 << 1) // Align, meminfo
+.set MULTIBOOT_1_CHECKSUM, -(MULTIBOOT_1_MAGIC + MULTIBOOT_1_FLAGS)
 
-.section .multiboot
+.set MULTIBOOT_2_MAGIC, 0xE85250D6
+.set MULTIBOOT_2_ARCH, 0
+.set MULTIBOOT_2_LENGTH, 16
+.set MULTIBOOT_2_CHECKSUM, -(MULTIBOOT_2_MAGIC + MULTIBOOT_2_ARCH + MULTIBOOT_2_LENGTH)
+
+.section .multiboot2
 .align 4
-.long MAGIC
-.long FLAGS
-.long CHECKSUM
+.long MULTIBOOT_2_MAGIC
+.long MULTIBOOT_2_ARCH
+.long MULTIBOOT_2_LENGTH
+.long MULTIBOOT_2_CHECKSUM
+
+.section .multiboot1
+.align 4
+.long MULTIBOOT_1_MAGIC
+.long MULTIBOOT_1_FLAGS
+.long MULTIBOOT_1_CHECKSUM
 
 .section .bss
 .align 16
diff --git a/arch/linker.ld b/arch/linker.ld
index 7569f55..fb05265 100644
--- a/arch/linker.ld
+++ b/arch/linker.ld
@@ -6,7 +6,8 @@ SECTIONS
 
     .text BLOCK(4K) : ALIGN(4K)
     {
-        *(.multiboot)
+        *(.multiboot2)
+        *(.multiboot1)
         *(.text)
     }