linux-kernel - Re: [RFC][PATCH 1/2] Add a layer of abstraction to use the memory reserved by device tree for ima buffer pass.

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Message-ID: <8b8bb74b-a3ac-1eb8-4b21-d00402a2bf62@linux.microsoft.com>
Date:   Mon, 18 May 2020 13:34:28 -0700
From:   Prakhar Srivastava <prsriva@...ux.microsoft.com>
To:     Rob Herring <robh@...nel.org>
Cc:     linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org,
        linuxppc-dev@...ts.ozlabs.org, devicetree@...r.kernel.org,
        linux-integrity@...r.kernel.org,
        linux-security-module@...r.kernel.org, catalin.marinas@....com,
        will@...nel.org, mpe@...erman.id.au, benh@...nel.crashing.org,
        paulus@...ba.org, frowand.list@...il.com, zohar@...ux.ibm.com,
        dmitry.kasatkin@...il.com, jmorris@...ei.org, serge@...lyn.com,
        pasha.tatashin@...een.com, allison@...utok.net,
        kstewart@...uxfoundation.org, takahiro.akashi@...aro.org,
        tglx@...utronix.de, vincenzo.frascino@....com,
        mark.rutland@....com, masahiroy@...nel.org, james.morse@....com,
        bhsharma@...hat.com, mbrugger@...e.com, hsinyi@...omium.org,
        tao.li@...o.com, christophe.leroy@....fr,
        gregkh@...uxfoundation.org, nramas@...ux.microsoft.com,
        tusharsu@...ux.microsoft.com, balajib@...ux.microsoft.com
Subject: Re: [RFC][PATCH 1/2] Add a layer of abstraction to use the memory
 reserved by device tree for ima buffer pass.



On 5/12/20 4:09 PM, Rob Herring wrote:
> On Mon, May 04, 2020 at 01:38:28PM -0700, Prakhar Srivastava wrote:
>> Introduce a device tree layer for to read and store ima buffer
>> from the reserved memory section of a device tree.
> 
> But why do I need 'a layer of abstraction'? I don't like them.
> 
This is a common path for the all architectures to carry over the
IMA measurement logs. A single layer will avoid any code duplication.

>> Signed-off-by: Prakhar Srivastava <prsriva@...ux.microsoft.com>
>> ---
>>   drivers/of/Kconfig  |   6 ++
>>   drivers/of/Makefile |   1 +
>>   drivers/of/of_ima.c | 165 ++++++++++++++++++++++++++++++++++++++++++++
> 
> Who are the users of this code and why does it need to be here? Most
> code for specific bindings are not in drivers/of/ but with the user. It
> doesn't sound like there's more than 1 user.
> 
Currently the path is exercised by arm64 kexec_file_load path. A slight
restructuring is needed on the powerpc side to use the same code path 
and other architectures can follow to add carrying over IMA logs over
kexec with just a few function calls.

I have attempted to bring the code path down to the highest common 
layer, however please do suggest if i can move this some where else.

Thanks,
Prakhar

>>   include/linux/of.h  |  34 +++++++++
>>   4 files changed, 206 insertions(+)
>>   create mode 100644 drivers/of/of_ima.c