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Date: Wed, 30 May 2007 18:51:37 +0300
From: Constantine Kousoulos <wuwei@freemail.gr>
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Subject: Re: multiboot header error
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Here is a sample kernel, built as elf64, that simply refuses to 
boot. It consists of only two files: boot.S and multiboot.h. It 
does absolutely nothing and it is a cut-down version of the kernel 
found at 
http://www.gnu.org/software/grub/manual/multiboot/multiboot.html#Example-OS-code 
or in grub-0.97/docs.

boot.S:
#include "multiboot.h"
	.text
	.globl	start, _start
start:
_start:
	jmp	multiboot_entry

	/* Align 64 bits boundary.  */
	.align	8
	
multiboot_header:
	.long	MULTIBOOT_HEADER_MAGIC
	.long	MULTIBOOT_HEADER_FLAGS
/*	.long	-(MULTIBOOT_HEADER_MAGIC + MULTIBOOT_HEADER_FLAGS)*/

multiboot_entry:
	/* Initialize the stack pointer.  */
	movq	$(stack + STACK_SIZE), %rsp

	/* Reset EFLAGS.  */
	pushq	$0
	popf

	/* Push the pointer to the Multiboot information structure.  */
	pushq	%rbx
	/* Push the magic value.  */
	pushq	%rax

loop:	hlt
	jmp	loop

	/* Our stack area.  */
	.comm	stack, STACK_SIZE
	
multiboot.h:
#define MULTIBOOT_HEADER_MAGIC		0xe85250d6
#define MULTIBOOT_HEADER_FLAGS		0x00000000
#define STACK_SIZE			0x4000

Makefile.am:
noinst_PROGRAMS = kernel
kernel_SOURCES = boot.S multiboot.h
kernel_CFLAGS = -fno-builtin -nostdinc -O -g -Wall
kernel_LDFLAGS = -nostdlib


All i get from GRUB2 is "error: No multiboot header found". I have 
tried changing the magic number to 0xd65052e8 to make sure i got 
it ok, but it still doesn't boot. The flags are all zero according 
to the next version of the Multiboot Spec. The same document 
doesn't say anything about a checksum in the multiboot header, so 
i commented it out.

What do you think is to blame for this behaviour?

Thanks,
Constantine