From ca36e0ad0e6b5a7cfbc11937d638d0c3283f91aa Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Thomas=20Lov=C3=A9n?= <thomasloven@gmail.com>
Date: Tue, 31 Oct 2017 09:00:16 +0100
Subject: [PATCH] Indicate multiboot version on boot

---
 src/kernel/boot/boot.S | 26 +++++++++++++++++++++-----
 1 file changed, 21 insertions(+), 5 deletions(-)

diff --git a/src/kernel/boot/boot.S b/src/kernel/boot/boot.S
index 1fcb671..b4a0a83 100644
--- a/src/kernel/boot/boot.S
+++ b/src/kernel/boot/boot.S
@@ -7,11 +7,27 @@
 _start:
 cli
 
-# Save the multiboot magic number
 mov ecx, eax
 
-// Print a red exclamation mark in top left corner
-mov eax, 0x0421
-mov short [0xB8000], ax
-// and loop infinitely
+// Print a red digit in the upper left corner to indicate the multiboot version
+// If not loaded by multiboot, print an exclamation mark
+cmp eax, MBOOT1_REPLY
+je mboot1
+cmp eax, MBOOT2_REPLY
+je mboot2
+mov eax, 0x0421 // Red exclamation point
+jmp print
+
+mboot1:
+mov eax, 0x0431 // Red 1
+jmp print
+
+mboot2:
+mov eax, 0x0432 // Red 2
+jmp print
+
+print:
+mov short [0xB8000], ax // Place in upper left corner
+
+// loop infinitely
 jmp $