Use either multiboot1 or multiboot2

src/kernel/boot/boot.S

@@ -4,6 +4,11 @@
 #define MBOOT1_FLAGS (MBOOT1_PALIGN | MBOOT1_MEMINFO)
 #define MBOOT1_CS -(MBOOT1_FLAGS + MBOOT1_MAGIC)
 
+#define MBOOT2_MAGIC 0xE85250D6
+#define MBOOT2_ARCH 0
+#define MBOOT2_LENGTH (MultiBootHeader2End - MultiBootHeader2)
+#define MBOOT2_CHECKSUM -(MBOOT2_MAGIC + MBOOT2_ARCH + MBOOT2_LENGTH)
+
 .intel_syntax noprefix
 
 .section .multiboot
@@ -13,6 +18,18 @@ MultiBootHeader1:
 .long MBOOT1_FLAGS
 .long MBOOT1_CS
 
+.align 0x1000
+MultiBootHeader2:
+.long MBOOT2_MAGIC
+.long MBOOT2_ARCH
+.long MBOOT2_LENGTH
+.long MBOOT2_CHECKSUM
+
+.short 0
+.short 0
+.long 8
+MultiBootHeader2End:
+
 .section .text
 .global _start
 .code32

toolchain/mkiso

@@ -13,6 +13,9 @@ set timeout=1
 set default=0
 
 menuentry "mittos64" {
+  multiboot2 /kernel
+}
+menuentry "mittos64 multiboot1" {
   multiboot /kernel
 }