linux-kernel - Re: EFI and multiboot2 devlopment work for Xen

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Date:	Tue, 22 Oct 2013 10:57:24 -0400
From:	Konrad Rzeszutek Wilk <konrad.wilk@...cle.com>
To:	"Woodhouse, David" <david.woodhouse@...el.com>
Cc:	Ian Campbell <ian.campbell@...rix.com>,
	Jan Beulich <JBeulich@...e.com>,
	"ross.philipson@...rix.com" <ross.philipson@...rix.com>,
	"stefano.stabellini@...citrix.com" <stefano.stabellini@...citrix.com>,
	"grub-devel@....org" <grub-devel@....org>,
	"Maliszewski, Richard L" <richard.l.maliszewski@...el.com>,
	"xen-devel@...ts.xen.org" <xen-devel@...ts.xen.org>,
	"boris.ostrovsky@...cle.com" <boris.ostrovsky@...cle.com>,
	Daniel Kiper <daniel.kiper@...cle.com>,
	Peter Jones <pjones@...hat.com>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"keir@....org" <keir@....org>
Subject: Re: EFI and multiboot2 devlopment work for Xen

On Tue, Oct 22, 2013 at 02:18:52PM +0000, Woodhouse, David wrote:
> 
> > I wonder why Linux can't make the EFI calls to fetch them itself?
> 
> It can. It does. It prefers to. This is what the "EFI boot stub" is all about. But grub2 is crack-inspired and likes to do all kinds of crap that it shouldn't. It is an exercise in complexity for complexity's sake. The 'linuxefi' method is actually not really Linux-specific; it just boots an EFI executable (which the bzImage *is* when compiled that way).

Perhaps I am reading the wrong code, but I am unable to find this
in the source.

I am looking in grub_cmd_linux in grub-core/loader/i386/efi/linux.c (Fedora 19 src RPM)
and I see:

                                                                               
  if (grub_file_read (file, &lh, sizeof (lh)) != sizeof (lh))                   
    {                                                                           
      if (!grub_errno)                                                          
        grub_error (GRUB_ERR_BAD_OS, N_("premature end of file %s"),            
                    argv[0]);                                                   
      goto fail;                                                                
    }                                                                           
                                                                                
  if (lh.boot_flag != grub_cpu_to_le16 (0xaa55))                                
    {                                                                           
      grub_error (GRUB_ERR_BAD_OS, N_("invalid magic number"));                 
      goto fail;                                                                
    }                                                                           
                                                                                
  if (lh.setup_sects > GRUB_LINUX_MAX_SETUP_SECTS)                              
    {                                                                           
      grub_error (GRUB_ERR_BAD_OS, N_("too many setup sectors"));               
      goto fail;                                                                
    }                                                                     
.. snip..

 if (!lh.handover_offset)                                                      
    {                                                                           
      grub_error (GRUB_ERR_BAD_OS, N_("kernel doesn't support EFI handover"));  
      goto fail;                                                                
    }                   


Which would imply that the header MUST have a Linux x86/boot header.

Which GRUB2 module can boot an non-Linux x86/boot header?

> 
> Seriously, forget bootloaders (especially grub2) and make it a COFF/PE executable.  Then everything should just work, including Secure Boot etc.
> 
> And bootloaders can still load that, of course.

That 'that' is a standard PE/COFF image?  Could you please point me
to the code that does that in GRUB2?

Thanks!
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