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

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Message-ID: <063D6719AE5E284EB5DD2968C1650D6D5F50F2BB@AcuExch.aculab.com>
Date:	Wed, 10 Aug 2016 14:40:13 +0000
From:	David Laight <David.Laight@...LAB.COM>
To:	'Petko Manolov' <petkan@...-labs.com>,
	Mimi Zohar <zohar@...ux.vnet.ibm.com>
CC:	"kexec@...ts.infradead.org" <kexec@...ts.infradead.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"Thiago Jung Bauermann" <bauerman@...ux.vnet.ibm.com>,
	"linux-security-module@...r.kernel.org" 
	<linux-security-module@...r.kernel.org>,
	"linux-ima-devel@...ts.sourceforge.net" 
	<linux-ima-devel@...ts.sourceforge.net>,
	"linuxppc-dev@...ts.ozlabs.org" <linuxppc-dev@...ts.ozlabs.org>
Subject: RE: [Linux-ima-devel] [PATCH 1/7] ima: on soft reboot, restore the
 measurement list

From: Linuxppc-dev [mailto:linuxppc-dev-bounces+david.laight=aculab.com@...ts.ozlabs.org] On Behalf Of
> > > So given what you have above, you'd use something like:
> > >
> > > struct ima_kexec_hdr {
> > > 	u16 version;
> > > 	u16 _reserved0;
> > > 	u32 _reserved1;
> > > 	u64 buffer_size;
> > > 	u64 count;
> > > };
> > >
> > > cheers
> >
> > Thanks, I'll make this change.
> 
> I would suggest:
> 
> struct ima_kexec_hdr {
> 	u64 buffer_size;
> 	u64 count;
> 	u16 version;
> };
> 
> and let the compiler add the proper padding, depending on the architecture.  On
> 32bit machine we'll have 4 bytes smaller allocations (compared to 64bit) while
> retaining the same functionality.

AAAArrrrgggg.....

That doesn't work for 32bit applications on 64bit hosts.
The extra bytes will make 0 difference to the allocation cost and
lots to the processing.

	David