linux-hardening - Re: [PATCH v5 13/17] firmware: qcom_scm: provide a read-modify-write function

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Message-ID: <32c6708d-a5a9-420e-bfb8-08ea11b3eb1e@quicinc.com>
Date:   Mon, 11 Sep 2023 13:41:56 +0530
From:   Kathiravan Thirumoorthy <quic_kathirav@...cinc.com>
To:     Mukesh Ojha <quic_mojha@...cinc.com>, <corbet@....net>,
        <agross@...nel.org>, <andersson@...nel.org>,
        <konrad.dybcio@...aro.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 13/17] firmware: qcom_scm: provide a read-modify-write
 function


On 9/11/2023 1:38 PM, Kathiravan Thirumoorthy wrote:
>
> On 9/10/2023 1:46 AM, Mukesh Ojha wrote:
>> It was realized by Srinivas K. that there is a need of
>> read-modify-write scm exported function so that it can
>> be used by multiple clients.
>>
>> Let's introduce qcom_scm_io_update_field() which masks
>> out the bits and write the passed value to that
>> bit-offset. Subsequent patch will use this function.
>>
>> Suggested-by: Srinivas Kandagatla <srinivas.kandagatla@...aro.org>
>> Signed-off-by: Mukesh Ojha <quic_mojha@...cinc.com>
>> ---
>
>
> Validated this change on IPQ9574 and IPQ53332 and system is entering 
> into the download mode.
>
> Tested-by: Kathiravan Thirumoorthy <quic_kathirav@...cinc.com> # 
> IP9574 and IPQ5332


Couple of typos. Apologize...

Validated this change on IPQ9574 and IPQ5332 and system is entering into 
the download mode.

Tested-by: Kathiravan Thirumoorthy <quic_kathirav@...cinc.com> # IPQ9574 
and IPQ5332


>
>
>>   drivers/firmware/qcom_scm.c            | 20 ++++++++++++++++++++
>>   include/linux/firmware/qcom/qcom_scm.h |  2 ++
>>   2 files changed, 22 insertions(+)
>>
>> diff --git a/drivers/firmware/qcom_scm.c b/drivers/firmware/qcom_scm.c
>> index fde33acd46b7..5ea8fc4fd4e8 100644
>> --- a/drivers/firmware/qcom_scm.c
>> +++ b/drivers/firmware/qcom_scm.c
>> @@ -78,6 +78,7 @@ static const char * const 
>> qcom_scm_convention_names[] = {
>>   };
>>     static struct qcom_scm *__scm;
>> +static DEFINE_SPINLOCK(lock);
>>     static int qcom_scm_clk_enable(void)
>>   {
>> @@ -407,6 +408,25 @@ int qcom_scm_set_remote_state(u32 state, u32 id)
>>   }
>>   EXPORT_SYMBOL(qcom_scm_set_remote_state);
>>   +int qcom_scm_io_update_field(phys_addr_t addr, unsigned int mask, 
>> unsigned int val)
>> +{
>> +    unsigned int old, new;
>> +    int ret;
>> +
>> +    spin_lock(&lock);
>> +    ret = qcom_scm_io_readl(addr, &old);
>> +    if (ret)
>> +        goto unlock;
>> +
>> +    new = (old & ~mask) | (val & mask);
>> +
>> +    ret = qcom_scm_io_writel(addr, new);
>> +unlock:
>> +    spin_unlock(&lock);
>> +    return ret;
>> +}
>> +EXPORT_SYMBOL_GPL(qcom_scm_io_update_field);
>> +
>>   static int __qcom_scm_set_dload_mode(struct device *dev, bool enable)
>>   {
>>       struct qcom_scm_desc desc = {
>> diff --git a/include/linux/firmware/qcom/qcom_scm.h 
>> b/include/linux/firmware/qcom/qcom_scm.h
>> index 250ea4efb7cb..ca41e4eb33ad 100644
>> --- a/include/linux/firmware/qcom/qcom_scm.h
>> +++ b/include/linux/firmware/qcom/qcom_scm.h
>> @@ -84,6 +84,8 @@ extern bool qcom_scm_pas_supported(u32 peripheral);
>>     extern int qcom_scm_io_readl(phys_addr_t addr, unsigned int *val);
>>   extern int qcom_scm_io_writel(phys_addr_t addr, unsigned int val);
>> +extern int qcom_scm_io_update_field(phys_addr_t addr, unsigned int 
>> mask,
>> +                    unsigned int val);
>>     extern bool qcom_scm_restore_sec_cfg_available(void);
>>   extern int qcom_scm_restore_sec_cfg(u32 device_id, u32 spare);