Hello,
while trying to figure out uefi, I wrote a multiboot2 header. It's an
exercise, but I'll share it anyway.
I think that keeping both headers is ok, because they are very small and
have different magic numbers. You can choose which one to use at grub2,
since "multiboot" and "multiboot2" are different commands.
I checked that both headers get recognized by the boot loader, but
couldn't see if the boot completed because of console not working, as
usual. Please test if interested.
Warmly,
Andrea Monaco
diff --git a/i386/i386at/boothdr.S b/i386/i386at/boothdr.S
index 9339cb91..50a1f73b 100644
--- a/i386/i386at/boothdr.S
+++ b/i386/i386at/boothdr.S
@@ -14,15 +14,22 @@ start:
_start:
jmp boot_entry
- /* MultiBoot header - see multiboot.h. */
+
+/* multiboot 1 and 2 headers - see multiboot.h. */
+
#define MULTIBOOT_MAGIC 0x1BADB002
+
#ifdef __ELF__
#define MULTIBOOT_FLAGS 0x00000003
#else /* __ELF__ */
#define MULTIBOOT_FLAGS 0x00010003
#endif /* __ELF__ */
- P2ALIGN(2)
-boot_hdr:
+
+#define MULTIBOOT2_MAGIC 0xE85250D6
+#define MULTIBOOT2_ARCHITECTURE 0x00000000 /* protected mode of i386 */
+
+ P2ALIGN(2)
+multiboot_hdr:
.long MULTIBOOT_MAGIC
.long MULTIBOOT_FLAGS
/*
@@ -31,13 +38,65 @@ boot_hdr:
*/
.long - (MULTIBOOT_MAGIC+MULTIBOOT_FLAGS)
#ifndef __ELF__ /* a.out kludge */
- .long boot_hdr /* header_addr */
+ .long multiboot_hdr /* header_addr */
.long _start /* load_addr */
.long _edata /* load_end_addr */
.long _end /* bss_end_addr */
.long boot_entry /* entry */
#endif /* __ELF__ */
+
+ P2ALIGN(3)
+multiboot2_hdr:
+ .long MULTIBOOT2_MAGIC
+ .long MULTIBOOT2_ARCHITECTURE
+ .long (boot_entry - multiboot2_hdr) /* total header length,
including magic */
+ .long -(MULTIBOOT2_MAGIC + MULTIBOOT2_ARCHITECTURE + boot_entry -
multiboot2_hdr) /* checksum */
+ /* mb2 information request about memory */
+ P2ALIGN(3)
+ .short 0x1
+ .short 0x0 /* required */
+ .long 0xC /* size */
+ .long 0x4
+
+ /* flags tag */
+ P2ALIGN(3)
+ .short 0x4
+ .short 0x0 /* required */
+ .long 0xC /* size */
+ .long 0x3 /* ega text support */
+
+ /* module alignment tag */
+ P2ALIGN(3)
+ .short 0x6
+ .short 0x0 /* required */
+ .long 0x8 /* size */
+
+#ifndef __ELF__ /* a.out stuff */
+ /* address tag */
+ P2ALIGN(3)
+ .short 0x2
+ .short 0x0 /* required */
+ .long 0x18 /* size */
+ .long multiboot2_hdr /* header_addr */
+ .long _start /* load_addr */
+ .long _edata /* load_end_addr */
+ .long _end /* bss_end_addr */
+
+ /* entry address tag */
+ P2ALIGN(3)
+ .short 0x3
+ .short 0x0 /* required */
+ .long 0xc /* size */
+ .long boot_entry
+#endif /* __ELF__ */
+
+ /* closing tag */
+ P2ALIGN(3)
+ .short 0x0
+ .short 0x0
+ .long 0x8
+
boot_entry:
/* use segmentation to offset ourself. */
lgdt boot_gdt_descr - KERNELBASE
