linux-kernel - Re: [PATCH v2 2/4] firmware: scm: Modify only the DLOAD bit in TCSR register for download mode

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Date:   Fri, 3 Mar 2023 13:24:48 +0530
From:   Mukesh Ojha <quic_mojha@...cinc.com>
To:     Dmitry Baryshkov <dmitry.baryshkov@...aro.org>,
        <agross@...nel.org>, <andersson@...nel.org>,
        <konrad.dybcio@...aro.org>
CC:     <linux-arm-msm@...r.kernel.org>, <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v2 2/4] firmware: scm: Modify only the DLOAD bit in TCSR
 register for download mode



On 3/1/2023 4:09 PM, Dmitry Baryshkov wrote:
> On 01/03/2023 11:55, Mukesh Ojha wrote:
>> CrashDump collection is based on the DLOAD bit of TCSR register.
>> To retain other bits, we read the register and modify only the
>> DLOAD bit as the other bits have their own significance.
>>
>> Originally-by: Poovendhan Selvaraj <quic_poovendh@...cinc.com>
>> Signed-off-by: Mukesh Ojha <quic_mojha@...cinc.com>
>> ---
>> Changes in v2:
>>   - Addressed comment made by Bjorn.
>>   - Added download mask from patch 3 to this.
>>
>>   drivers/firmware/qcom_scm.c | 17 +++++++++++++++--
>>   1 file changed, 15 insertions(+), 2 deletions(-)
>>
>> diff --git a/drivers/firmware/qcom_scm.c b/drivers/firmware/qcom_scm.c
>> index 51eb853..c9f1fad 100644
>> --- a/drivers/firmware/qcom_scm.c
>> +++ b/drivers/firmware/qcom_scm.c
>> @@ -27,6 +27,8 @@ module_param(download_mode, bool, 0);
>>   #define SCM_HAS_IFACE_CLK    BIT(1)
>>   #define SCM_HAS_BUS_CLK        BIT(2)
>> +#define QCOM_DOWNLOAD_MODE_MASK 0x30
>> +
>>   struct qcom_scm {
>>       struct device *dev;
>>       struct clk *core_clk;
>> @@ -419,6 +421,7 @@ static void qcom_scm_set_download_mode(bool enable)
>>   {
>>       bool avail;
>>       int ret = 0;
>> +    u32 val;
>>       avail = __qcom_scm_is_call_available(__scm->dev,
>>                            QCOM_SCM_SVC_BOOT,
>> @@ -426,8 +429,18 @@ static void qcom_scm_set_download_mode(bool enable)
>>       if (avail) {
>>           ret = __qcom_scm_set_dload_mode(__scm->dev, enable);
>>       } else if (__scm->dload_mode_addr) {
>> -        ret = qcom_scm_io_writel(__scm->dload_mode_addr,
>> -                enable ? QCOM_SCM_BOOT_SET_DLOAD_MODE : 0);
>> +        ret = qcom_scm_io_readl(__scm->dload_mode_addr, &val);
>> +        if (ret) {
>> +            dev_err(__scm->dev,
>> +                "failed to read dload mode address value: %d\n", ret);
>> +            return;
>> +        }
>> +
>> +        val &= ~QCOM_DOWNLOAD_MODE_MASK;
>> +        if (enable)
>> +            val |= QCOM_SCM_BOOT_SET_DLOAD_MODE;
>> +
>> +        ret = qcom_scm_io_writel(__scm->dload_mode_addr, val);
> 
> Any locking for this RMW?

While you ask this, i thought about who all are the user of this 
function. Only, multiple calls to module param callback where
this race could be possible.

I am doubtful, if introducing global mutex lock will be allowed to 
handle this. Any comments.


-Mukesh
> 
>>       } else {
>>           dev_err(__scm->dev,
>>               "No available mechanism for setting download mode\n");
>