linux-kernel - Re: [RFC 0/3] extend kexec_file

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Date:	Wed, 13 Jul 2016 21:59:18 +0200
From:	Arnd Bergmann <arnd@...db.de>
To:	Thiago Jung Bauermann <bauerman@...ux.vnet.ibm.com>
Cc:	Mark Rutland <mark.rutland@....com>, linuxppc-dev@...ts.ozlabs.org,
	Dave Young <dyoung@...hat.com>,
	linux-arm-kernel@...ts.infradead.org, bhe@...hat.com,
	kexec@...ts.infradead.org, linux-kernel@...r.kernel.org,
	AKASHI Takahiro <takahiro.akashi@...aro.org>,
	"Eric W. Biederman" <ebiederm@...ssion.com>,
	Vivek Goyal <vgoyal@...hat.com>
Subject: Re: [RFC 0/3] extend kexec_file_load system call

On Wednesday, July 13, 2016 3:45:41 PM CEST Thiago Jung Bauermann wrote:
> Am Mittwoch, 13 Juli 2016, 15:13:42 schrieb Arnd Bergmann:
> > On Wednesday, July 13, 2016 10:41:28 AM CEST Mark Rutland wrote:
> > > On Wed, Jul 13, 2016 at 10:01:33AM +0200, Arnd Bergmann wrote:
> > > > - kboot/petitboot with all of the user space being part of the trusted
> > > > boot> > 
> > > >   chain: it would be good to allow these to modify the dtb as needed
> > > >   without breaking the trust chain, just like we allow grub or u-boot
> > > >   to modify the dtb before passing it to the kernel.
> > > 
> > > It depends on *what* we need to modify here. We can modify the bootargs
> > > and initrd properties as part of the kexec_file_load syscall, so what
> > > else would we want to alter?
> > 
> > I guess petitboot can also just use kexec_load() instead of
> > kexec_file_load(), as long as the initramfs containing petitboot is
> > trusted by the kernel.
> 
> For secure boot, Petitboot needs to use kexec_file_load, because of the 
> following two features which the system call enables:
> 
> 1. only allow loading of signed kernels.
> 2. "measure" (i.e., record the hashes of) the kernel, initrd, kernel
>    command line and other boot inputs for the Integrity Measurement
>    Architecture subsystem.
> 
> Those can't be done with kexec_load.

Can't petitboot do both of these in user space?

	Arnd