linux-kernel - Re: [PATCH 1/7] ima: on soft reboot, restore the measurement list

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Message-Id: <18857164.IzlezsQllh@hactar>
Date:	Wed, 10 Aug 2016 02:05:53 -0300
From:	Thiago Jung Bauermann <bauerman@...ux.vnet.ibm.com>
To:	Michael Ellerman <mpe@...erman.id.au>
Cc:	Mimi Zohar <zohar@...ux.vnet.ibm.com>,
	linux-security-module@...r.kernel.org,
	linuxppc-dev@...ts.ozlabs.org, kexec@...ts.infradead.org,
	linux-kernel@...r.kernel.org,
	linux-ima-devel@...ts.sourceforge.net,
	Dave Young <dyoung@...hat.com>
Subject: Re: [PATCH 1/7] ima: on soft reboot, restore the measurement list

Am Mittwoch, 10 August 2016, 13:41:08 schrieb Michael Ellerman:
> Thiago Jung Bauermann <bauerman@...ux.vnet.ibm.com> writes:
> > Am Dienstag, 09 August 2016, 09:01:13 schrieb Mimi Zohar:
> >> On Tue, 2016-08-09 at 20:59 +1000, Michael Ellerman wrote:
> >> > Mimi Zohar <zohar@...ux.vnet.ibm.com> writes: 
> >> > > +/* Some details preceding the binary serialized measurement list
> >> > > */
> >> > > +struct ima_kexec_hdr {
> >> > > +	unsigned short version;
> >> > > +	unsigned long buffer_size;
> >> > > +	unsigned long count;
> >> > > +} __packed;
> >> > > +
> >> > 
> >> > Am I understanding it correctly that this structure is passed between
> >> > kernels?
> >> 
> >> Yes, the header prefixes the measurement list, which is being passed on
> >> the same computer to the next kernel.  Could the architecture (eg.
> >> LE/BE) change between soft re-boots?
> > 
> > Yes. I am able to boot a BE kernel from an LE kernel with my patches.
> > Whether we want to support that or not is another question...
> 
> Yes you must support that. BE -> LE and vice versa.

I didn't test BE - LE yet, but will do.

> You should also consider the possibility that the next kernel is not
> Linux.

If the next kernel is an ELF binary and it supports the kexec "calling 
convention", it should work too. What could possibly go wrong? I can try 
FreeBSD (I suppose it's an ELF kernel) and see what happens.

-- 
[]'s
Thiago Jung Bauermann
IBM Linux Technology Center