linux-kernel - Re: [PATCH v2] coresight: etm3x: Fix cntr_val_show() to match cntr_val

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Message-ID: <d7c17bc4-a7dd-42fa-8dd3-16a404a6d713@linaro.org>
Date: Mon, 1 Dec 2025 10:25:25 +0000
From: James Clark <james.clark@...aro.org>
To: Kuan-Wei Chiu <visitorckw@...il.com>, suzuki.poulose@....com
Cc: mike.leach@...aro.org, alexander.shishkin@...ux.intel.com,
 gregkh@...uxfoundation.org, mathieu.poirier@...aro.org, leo.yan@....com,
 Al.Grant@....com, jserv@...s.ncku.edu.tw, marscheng@...gle.com,
 ericchancf@...gle.com, milesjiang@...gle.com, nickpan@...gle.com,
 coresight@...ts.linaro.org, linux-arm-kernel@...ts.infradead.org,
 linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2] coresight: etm3x: Fix cntr_val_show() to match
 cntr_val_store() behavior



On 01/12/2025 9:52 am, Kuan-Wei Chiu wrote:
> The cntr_val_show() function was intended to print the values of all
> counters using a loop. However, due to a buffer overwrite issue with
> sprintf(), it effectively only displayed the value of the last counter.
> 
> The companion function, cntr_val_store(), allows users to modify a
> specific counter selected by 'cntr_idx'. To maintain consistency
> between read and write operations and to align with the ETM4x driver
> behavior, modify cntr_val_show() to report only the value of the
> currently selected counter.
> 
> This change removes the loop and the "counter %d:" prefix, printing
> only the hexadecimal value. It also adopts sysfs_emit() for standard
> sysfs output formatting.
> 
> Fixes: a939fc5a71ad ("coresight-etm: add CoreSight ETM/PTM driver")
> Signed-off-by: Kuan-Wei Chiu <visitorckw@...il.com>
> ---
> Build test only.
> 
> Changes in v2:
> - Redesigned the fix to match cntr_val_store() logic (display only the
>    currently selected counter) instead of attempting to list all
>    counters.
> - Removed the loop and the "counter %d:" prefix.
> - Switched from sprintf() to sysfs_emit().
> - Refactored control flow to use a single return point.
> 
> v1: https://lore.kernel.org/lkml/20251121002350.1166758-1-visitorckw@gmail.com/
> 
>   .../hwtracing/coresight/coresight-etm3x-sysfs.c   | 15 ++++-----------
>   1 file changed, 4 insertions(+), 11 deletions(-)
> 
> diff --git a/drivers/hwtracing/coresight/coresight-etm3x-sysfs.c b/drivers/hwtracing/coresight/coresight-etm3x-sysfs.c
> index 762109307b86..a6a650331196 100644
> --- a/drivers/hwtracing/coresight/coresight-etm3x-sysfs.c
> +++ b/drivers/hwtracing/coresight/coresight-etm3x-sysfs.c
> @@ -717,26 +717,19 @@ static DEVICE_ATTR_RW(cntr_rld_event);
>   static ssize_t cntr_val_show(struct device *dev,
>   			     struct device_attribute *attr, char *buf)
>   {
> -	int i, ret = 0;
>   	u32 val;
>   	struct etm_drvdata *drvdata = dev_get_drvdata(dev->parent);
>   	struct etm_config *config = &drvdata->config;
>   
>   	if (!coresight_get_mode(drvdata->csdev)) {
>   		spin_lock(&drvdata->spinlock);
> -		for (i = 0; i < drvdata->nr_cntr; i++)
> -			ret += sprintf(buf, "counter %d: %x\n",
> -				       i, config->cntr_val[i]);
> +		val = config->cntr_val[config->cntr_idx];
>   		spin_unlock(&drvdata->spinlock);
> -		return ret;
> -	}
> -
> -	for (i = 0; i < drvdata->nr_cntr; i++) {
> -		val = etm_readl(drvdata, ETMCNTVRn(i));
> -		ret += sprintf(buf, "counter %d: %x\n", i, val);
> +	} else {
> +		val = etm_readl(drvdata, ETMCNTVRn(config->cntr_idx));
>   	}
>   
> -	return ret;
> +	return sysfs_emit(buf, "%x\n", val);

Sorry I missed this on the previous version, but this should be %#x to 
add the "0x" prefix. All the other ones in this file have it. Otherwise 
you can't tell the difference between decimal and hex.

>   }
>   
>   static ssize_t cntr_val_store(struct device *dev,