linux-kernel - Re: [PATCH V4 03/11] coresight: tmc: Extract device properties from AMBA pid based table lookup

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Message-ID: <0c65f3b0-a879-444c-b0a4-4af485e72166@arm.com>
Date: Tue, 13 Feb 2024 08:43:39 +0530
From: Anshuman Khandual <anshuman.khandual@....com>
To: Suzuki K Poulose <suzuki.poulose@....com>,
 linux-arm-kernel@...ts.infradead.org
Cc: Lorenzo Pieralisi <lpieralisi@...nel.org>,
 Sudeep Holla <sudeep.holla@....com>, Mike Leach <mike.leach@...aro.org>,
 James Clark <james.clark@....com>,
 Maxime Coquelin <mcoquelin.stm32@...il.com>,
 Alexandre Torgue <alexandre.torgue@...s.st.com>, linux-acpi@...r.kernel.org,
 linux-kernel@...r.kernel.org, coresight@...ts.linaro.org,
 linux-stm32@...md-mailman.stormreply.com
Subject: Re: [PATCH V4 03/11] coresight: tmc: Extract device properties from
 AMBA pid based table lookup



On 2/12/24 17:43, Suzuki K Poulose wrote:
> On 23/01/2024 05:46, Anshuman Khandual wrote:
>> This extracts device properties from AMBA pid based table lookup. This also
>> defers tmc_etr_setup_caps() after the coresight device has been initialized
>> so that PID value can be read.
>>
>> Cc: Suzuki K Poulose <suzuki.poulose@....com>
>> Cc: Mike Leach <mike.leach@...aro.org>
>> Cc: James Clark <james.clark@....com>
>> Cc: coresight@...ts.linaro.org
>> Cc: linux-arm-kernel@...ts.infradead.org
>> Cc: linux-kernel@...r.kernel.org
>> Signed-off-by: Anshuman Khandual <anshuman.khandual@....com>
>> ---
>>   .../hwtracing/coresight/coresight-tmc-core.c  | 19 +++++++++++++------
>>   1 file changed, 13 insertions(+), 6 deletions(-)
>>
>> diff --git a/drivers/hwtracing/coresight/coresight-tmc-core.c b/drivers/hwtracing/coresight/coresight-tmc-core.c
>> index 7ec5365e2b64..e71db3099a29 100644
>> --- a/drivers/hwtracing/coresight/coresight-tmc-core.c
>> +++ b/drivers/hwtracing/coresight/coresight-tmc-core.c
>> @@ -370,16 +370,24 @@ static inline bool tmc_etr_has_non_secure_access(struct tmc_drvdata *drvdata)
>>       return (auth & TMC_AUTH_NSID_MASK) == 0x3;
>>   }
>>   +#define TMC_AMBA_MASK 0xfffff
>> +
>> +static const struct amba_id tmc_ids[];
>> +
>>   /* Detect and initialise the capabilities of a TMC ETR */
>> -static int tmc_etr_setup_caps(struct device *parent, u32 devid, void *dev_caps)
>> +static int tmc_etr_setup_caps(struct device *parent, u32 devid)
>>   {
>>       int rc;
>> -    u32 dma_mask = 0;
>> +    u32 tmc_pid, dma_mask = 0;
>>       struct tmc_drvdata *drvdata = dev_get_drvdata(parent);
>> +    void *dev_caps;
>>         if (!tmc_etr_has_non_secure_access(drvdata))
>>           return -EACCES;
>>   +    tmc_pid = coresight_get_pid(&drvdata->csdev->access) & TMC_AMBA_MASK;
>> +    dev_caps = coresight_get_uci_data_from_amba(tmc_ids, tmc_pid);
>> +
>>       /* Set the unadvertised capabilities */
>>       tmc_etr_init_caps(drvdata, (u32)(unsigned long)dev_caps);
>>   @@ -497,10 +505,6 @@ static int tmc_probe(struct amba_device *adev, const struct amba_id *id)
>>           desc.type = CORESIGHT_DEV_TYPE_SINK;
>>           desc.subtype.sink_subtype = CORESIGHT_DEV_SUBTYPE_SINK_SYSMEM;
>>           desc.ops = &tmc_etr_cs_ops;
>> -        ret = tmc_etr_setup_caps(dev, devid,
>> -                     coresight_get_uci_data(id));
>> -        if (ret)
>> -            goto out;
>>           idr_init(&drvdata->idr);
>>           mutex_init(&drvdata->idr_mutex);
>>           dev_list = &etr_devs;
>> @@ -539,6 +543,9 @@ static int tmc_probe(struct amba_device *adev, const struct amba_id *id)
>>           goto out;
>>       }
>>   +    if (drvdata->config_type == TMC_CONFIG_TYPE_ETR)
>> +        ret = tmc_etr_setup_caps(dev, devid);
>> +
> 
> With this change, we silently accept an ETR that may only have "SECURE" access only and crash later while we try to enable tracing. You could
> pass in the "access" (which is already in 'desc.access' in the original
> call site and deal with it ?

Just wondering, if something like the following will help ? A failed tmc_etr_setup_caps()
because of failed tmc_etr_has_non_secure_access(), will unregister the coresight device
before returning.

--- a/drivers/hwtracing/coresight/coresight-tmc-core.c
+++ b/drivers/hwtracing/coresight/coresight-tmc-core.c
@@ -538,8 +538,13 @@ static int __tmc_probe(struct device *dev, struct resource *res)
                goto out;
        }
 
-       if (drvdata->config_type == TMC_CONFIG_TYPE_ETR)
+       if (drvdata->config_type == TMC_CONFIG_TYPE_ETR) {
                ret = tmc_etr_setup_caps(dev, devid);
+               if (ret) {
+                       coresight_unregister(drvdata->csdev);
+                       goto out;
+               }
+       }
 
        drvdata->miscdev.name = desc.name;
        drvdata->miscdev.minor = MISC_DYNAMIC_MINOR;