linux-kernel - Re: [V2 PATCH 2/3] dt-bindings: chosen: Document ima-kexec-buffer

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Date:   Mon, 13 Jul 2020 13:32:50 -0700
From:   Prakhar Srivastava <prsriva@...ux.microsoft.com>
To:     Thiago Jung Bauermann <bauerman@...ux.ibm.com>
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, robh+dt@...nel.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: [V2 PATCH 2/3] dt-bindings: chosen: Document ima-kexec-buffer



On 6/19/20 5:41 PM, Thiago Jung Bauermann wrote:
> 
> Prakhar Srivastava <prsriva@...ux.microsoft.com> writes:
> 
>> Integrity measurement architecture(IMA) validates if files
>> have been accidentally or maliciously altered, both remotely and
>> locally, appraise a file's measurement against a "good" value stored
>> as an extended attribute, and enforce local file integrity.
>>
>> IMA also measures singatures of kernel and initrd during kexec along with
>> the command line used for kexec.
>> These measurements are critical to verify the seccurity posture of the OS.
>>
>> Resering memory and adding the memory information to a device tree node
>> acts as the mechanism to carry over IMA measurement logs.
>>
>> Update devicetree documentation to reflect the addition of new property
>> under the chosen node.
> 
> Thank you for writing this documentation patch. It's something I should
> have done when I added the powerpc IMA kexec support.
> 
> You addressed Rob Herring's comments regarding the commit message, but
> not the ones regarding the patch contents.
> 
> When posting a new version of the patches, make sure to address all
> comments made so far. Addressing a comment doesn't necessarily mean
> implementing the requested change. If you don't then you should at least
> explain why you chose a different path.
> 
> I mention it because this has occurred before with this patch series,
> and it's hard to make forward progress if review comments get ignored.
> 
>> ---
>>   Documentation/devicetree/bindings/chosen.txt | 17 +++++++++++++++++
>>   1 file changed, 17 insertions(+)
>>
>> diff --git a/Documentation/devicetree/bindings/chosen.txt b/Documentation/devicetree/bindings/chosen.txt
>> index 45e79172a646..a15f70c007ef 100644
>> --- a/Documentation/devicetree/bindings/chosen.txt
>> +++ b/Documentation/devicetree/bindings/chosen.txt
>> @@ -135,3 +135,20 @@ e.g.
>>   		linux,initrd-end = <0x82800000>;
>>   	};
>>   };
>> +
>> +linux,ima-kexec-buffer
>> +----------------------
>> +
>> +This property(currently used by powerpc, arm64) holds the memory range,
> 
> space before the parenthesis.
> 
>> +the address and the size, of the IMA measurement logs that are being carried
> 
> Maybe it's because English isn't my first language, but IMHO it's
> clearer if "the address and the size" is between parentheses rather than
> commas.
> 
>> +over to the kexec session.
> 
> I don't think there's a "kexec session", but I'm not sure what a good
> term would be. "linux,booted-from-kexec" uses "new kernel" so perhaps
> that's a good option to use instead of "kexec session".
> 
>> +
>> +/ {
>> +	chosen {
>> +		linux,ima-kexec-buffer = <0x9 0x82000000 0x0 0x00008000>;
>> +	};
>> +};
>> +
>> +This porperty does not represent real hardware, but the memory allocated for
>> +carrying the IMA measurement logs. The address and the suze are expressed in
>> +#address-cells and #size-cells, respectively of the root node.
> 
> 
I will update the descriptions and ack the comments/changes in the 
patches as well.

Thankyou,
Prakhar Srivastava
> --
> Thiago Jung Bauermann
> IBM Linux Technology Center
>