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

[Prakhar Srivastava <prsriva@linux.microsoft.com>]

On 6/19/20 5:41 PM, Thiago Jung Bauermann wrote:
> 
> Prakhar Srivastava <prsriva@linux.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
>