linux-hardening - Re: [PATCH v3 02/18] remoteproc: qcom: Move minidump specific data to qcom

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Date:   Thu, 4 May 2023 17:16:01 +0200
From:   Krzysztof Kozlowski <krzysztof.kozlowski@...aro.org>
To:     Mukesh Ojha <quic_mojha@...cinc.com>, agross@...nel.org,
        andersson@...nel.org, konrad.dybcio@...aro.org, corbet@....net,
        keescook@...omium.org, tony.luck@...el.com, gpiccoli@...lia.com,
        catalin.marinas@....com, will@...nel.org,
        krzysztof.kozlowski+dt@...aro.org, robh+dt@...nel.org,
        linus.walleij@...aro.org, linux-gpio@...r.kernel.org,
        srinivas.kandagatla@...aro.org
Cc:     linux-arm-msm@...r.kernel.org, linux-remoteproc@...r.kernel.org,
        linux-kernel@...r.kernel.org, linux-hardening@...r.kernel.org,
        linux-arm-kernel@...ts.infradead.org, linux-doc@...r.kernel.org
Subject: Re: [PATCH v3 02/18] remoteproc: qcom: Move minidump specific data to
 qcom_minidump.h

On 04/05/2023 14:57, Mukesh Ojha wrote:
> 
> 
> On 5/4/2023 6:06 PM, Krzysztof Kozlowski wrote:
>> On 04/05/2023 14:26, Mukesh Ojha wrote:
>>>
>>>
>>> On 5/4/2023 5:33 PM, Krzysztof Kozlowski wrote:
>>>> On 04/05/2023 13:58, Mukesh Ojha wrote:
>>>>>
>>>>>
>>>>> On 5/4/2023 5:08 PM, Krzysztof Kozlowski wrote:
>>>>>> On 03/05/2023 19:02, Mukesh Ojha wrote:
>>>>>>> Move minidump specific data types and macros to a separate internal
>>>>>>> header(qcom_minidump.h) so that it can be shared among different
>>>>>>> Qualcomm drivers.
>>>>>>
>>>>>> No, this is not internal header. You moved it to global header.
>>>>>>
>>>>>> There is no reason driver internals should be exposed to other unrelated
>>>>>> subsystems.
>>>>>>
>>>>>>>
>>>>>>> There is no change in functional behavior after this.
>>>>>>
>>>>>> It is. You made all these internal symbols available to others.
>>>>>>
>>>>>>>
>>>>>>
>>>>>> This comes without justification why other drivers needs to access
>>>>>> private and internal data. It does not look correct design. NAK.
>>>>>
>>>>> Thanks for catching outdated commit text, will fix the commit with
>>>>> more descriptive reasoning.
>>>>>
>>>>> It has to be global so that co-processor minidump and apss minidump can
>>>>> share data structure and they are lying in different directory.
>>>>>
>>>>
>>>> Then you should not share all the internals of memory layout but only
>>>> few pieces necessary to talk with minidump driver. The minidump driver
>>>> should organize everything how it wants.
>>>
>>> These are core data structure which is shared with boot firmware and the
>>> one's are moved here all are required by minidump driver .
>>
>> I am not sure if I understand correctly. If they are all required by
>> minidump driver, then this must not be in include, but stay with
>> minidump. Remoteproc then should not touch it.
>>
>> I don't understand why internals of minidump should be important for
>> remoteproc. If they are, means you broken encapsulation.
>>
>>>
>>> If you follow here[1], i raised by concern to make this particular one's
>>> as private and later to avoid confusion went with single header.
>>> But if others agree, I will keep the one that get shared with minidump
>>> as separate one or if relative path of headers are allowed that can make
>>> it private between these drivers(which i don't think, will be allowed or
>>> recommended).
>>
>> Let's be specific: why MD_REGION_VALID must be available for remoteproc
>> or any other driver after introducing qcom minidump driver?
> 
> Forget about this driver for a moment.
> 
> I am not sure  how much you know about existing qcom_minidump()
> implementation and why is it there in first place in remoteproc
> code in driver/remoteproc/qcom_common.c
> 
> The idea is, remoteproc co-processor like adsp/cdsp etc. may have their
> static predefined region (segments) to be collected on their crash which 
> is what exactly existing qcom_minidump() is doing.
> 
> Now, after this minidump series, APSS (linux) will have it's
> own of collecting linux client region independent of whether
> remoteproc minidump collection.
> 
> I think, are you hinting to move all minidump related code from 
> remoteproc to qcom_minidump driver, is this what are you trying
> to say ?

Close, not all but the ones not necessary to identify the
regions/storage/layout. If some variable about this
region/storage/layout is the same everywhere, it means it's basically a
property of qcom minidump and you have just exposed it to consumers
breaking encapsulation.

Best regards,
Krzysztof