linux-hardening - Re: [PATCH v5 06/17] soc: qcom: Add Qualcomm APSS minidump kernel driver

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Date:   Mon, 11 Sep 2023 21:33:43 +0200
From:   Konrad Dybcio <konrad.dybcio@...aro.org>
To:     Jeff Johnson <quic_jjohnson@...cinc.com>,
        Krzysztof Kozlowski <krzysztof.kozlowski@...aro.org>,
        Mukesh Ojha <quic_mojha@...cinc.com>, corbet@....net,
        agross@...nel.org, andersson@...nel.org, robh+dt@...nel.org,
        krzysztof.kozlowski+dt@...aro.org, conor+dt@...nel.org,
        keescook@...omium.org, tony.luck@...el.com, gpiccoli@...lia.com,
        mathieu.poirier@...aro.org, catalin.marinas@....com,
        will@...nel.org, linus.walleij@...aro.org,
        andy.shevchenko@...il.com, vigneshr@...com, nm@...com,
        matthias.bgg@...il.com, kgene@...nel.org, alim.akhtar@...sung.com,
        bmasney@...hat.com, quic_tsoni@...cinc.com
Cc:     linux-doc@...r.kernel.org, linux-kernel@...r.kernel.org,
        linux-arm-msm@...r.kernel.org, linux-hardening@...r.kernel.org,
        linux-remoteproc@...r.kernel.org,
        linux-arm-kernel@...ts.infradead.org, linux-gpio@...r.kernel.org,
        linux-mediatek@...ts.infradead.org,
        linux-samsung-soc@...r.kernel.org, kernel@...cinc.com
Subject: Re: [PATCH v5 06/17] soc: qcom: Add Qualcomm APSS minidump kernel
 driver

On 11.09.2023 21:09, Jeff Johnson wrote:
> On 9/11/2023 4:07 AM, Krzysztof Kozlowski wrote:
>> On 09/09/2023 22:16, Mukesh Ojha wrote:
>>> +/**
>>> + * qcom_minidump_region_register() - Register region in APSS Minidump table.
>>> + * @region: minidump region.
>>> + *
>>> + * Return: On success, it returns 0 and negative error value on failure.
>>> + */
>>> +int qcom_minidump_region_register(const struct qcom_minidump_region *region)
>>> +{
>>> +    struct minidump *md;
>>> +    int ret;
>>> +
>>> +    md = qcom_smem_minidump_ready();
>>> +    if (!md)
>>> +        return -EPROBE_DEFER;
>>> +
>>> +    if (!qcom_minidump_valid_region(region))
>>> +        return -EINVAL;
>>> +
>>> +    mutex_lock(&md->md_lock);
>>> +    ret = qcom_md_region_register(md, region);
>>> +    if (ret)
>>> +        goto unlock;
>>> +
>>> +    qcom_md_update_elfheader(md, region);
>>> +unlock:
>>> +    mutex_unlock(&md->md_lock);
>>> +    return ret;
>>> +}
>>> +EXPORT_SYMBOL_GPL(qcom_minidump_region_register);
>>
>> NAK, there is no user for this.
>>
>> Drop all exports from minidump drivers. Your upstream driver *must not*
>> expose stuff to your vendor drivers.
> 
> Do we not expect that upstream drivers would want to register?
> Mind you, in the downstream code the following was a bad limitation:
> #define MAX_NUM_OF_SS           10
No, Krzysztof meant that you are not allowed to export symbols
without immediately providing a user for them - meaning if the
functions are not going to be used upstream, this change will
not be accepted.

Konrad