From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from zztop.nucleusys.com (lan.nucleusys.com [92.247.61.126]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (No client certificate requested) by lists.ozlabs.org (Postfix) with ESMTPS id 3s8YXf50ndzDqJ5 for ; Thu, 11 Aug 2016 00:33:06 +1000 (AEST) Date: Wed, 10 Aug 2016 17:32:30 +0300 From: Petko Manolov To: Mimi Zohar Cc: Michael Ellerman , kexec@lists.infradead.org, linux-kernel@vger.kernel.org, linux-ima-devel@lists.sourceforge.net, linux-security-module@vger.kernel.org, Thiago Jung Bauermann , linuxppc-dev@lists.ozlabs.org Subject: Re: [Linux-ima-devel] [PATCH 1/7] ima: on soft reboot, restore the measurement list Message-ID: <20160810143230.GD4087@localhost> References: <1470313475-20090-1-git-send-email-zohar@linux.vnet.ibm.com> <3544655.o5QPxko4Ba@hactar> <87r39xthnv.fsf@concordia.ellerman.id.au> <18857164.IzlezsQllh@hactar> <87vaz9rlx2.fsf@concordia.ellerman.id.au> <1470833676.2881.183.camel@linux.vnet.ibm.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii In-Reply-To: <1470833676.2881.183.camel@linux.vnet.ibm.com> List-Id: Linux on PowerPC Developers Mail List List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , On 16-08-10 08:54:36, Mimi Zohar wrote: > On Wed, 2016-08-10 at 19:52 +1000, Michael Ellerman wrote: > > Thiago Jung Bauermann writes: > > > > > Am Mittwoch, 10 August 2016, 13:41:08 schrieb Michael Ellerman: > > >> Thiago Jung Bauermann 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 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. > > > > Thanks. > > Ok. There have been requests for making the binary_runtime_measurements > architecture independent. As this was not a network facing interface, > we left it in native format. With the kernel now consuming this data, > it makes sense for the binary_runtime_measurements to be in an > architecture independent format. > > Unfortunately, as the /ima/binary_runtime_measurements is > not prefixed with any metadata, this change would need to be Kconfig > based, but kexec would always use the architecture independent format. > > > >> You should also consider the possibility that the next kernel is not > > >> Linux. > > Oh! > > > > 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. > > > > At least for old style kexec (not sys_kexec_load()) I don't think it > > even needs to be an ELF binary. > > > > I think there are folks working on FreeBSD (or $?BSD), so I think the > > basic kexec part works. > > > > There's nothing (yet) that wants to use this measurement list obviously, > > but it should be designed such that it could be used by an unknown > > future kernel that knows the ABI. > > > > 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. cheers, Petko