linux-kernel - Re: [PATCH 0/6] kexec: A new system call to allow in kernel loading

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Date:	Fri, 22 Nov 2013 11:48:14 -0800
From:	Greg KH <greg@...ah.com>
To:	Vivek Goyal <vgoyal@...hat.com>
Cc:	"Eric W. Biederman" <ebiederm@...ssion.com>,
	linux-kernel@...r.kernel.org, kexec@...ts.infradead.org,
	hpa@...or.com, mjg59@...f.ucam.org
Subject: Re: [PATCH 0/6] kexec: A new system call to allow in kernel loading

On Fri, Nov 22, 2013 at 09:19:46AM -0500, Vivek Goyal wrote:
> On Fri, Nov 22, 2013 at 05:34:03AM -0800, Eric W. Biederman wrote:
> 
> [..]
> > > Why ELF case is so interesting. I have not use kexec to boot ELF
> > > images in years and have not seen others using it too. In fact bzImage
> > > seems to be the most common kernel image format for x86, most of the distros
> > > ship and use.
> > 
> > ELF is interesting because it is the minimal file format that does
> > everything you need.   So especially for a proof of concept ELF needs to
> > come first.  There is an extra virtual address field in the ELF segment
> > header but otherwise ELF does not have any unnecessary fields.
> > 
> > ELF is interesting because it is the native kernel file format on all
> > architectures linux supports including x86.
> > 
> > ELF is interesting because producing an ELF image in practice requires
> > a trivial amount of tooling so it is a good general purpose format to
> > support.
> 
> Ok. I will have a look at ELF loader too. I was hoping to keep only one
> loader in initial patch. But looks like that's not acceptable.

I totally disagree.  I think what you have done now is fine.  If it
works for bzImage, it's a good sense that this is usable as-is.

And, if someone else cares about signed elf images, hey, let them
implement the loader for it :)

Either way, the syscall interface wouldn't change, which is the
important thing to get right, so you should be fine for now.

thanks,

greg k-h
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