linux-kernel - Re: [RFC PATCH 19/20] coresight: etm3x: implementing perf's user/kernel mode

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Message-ID: <87mvw4jjps.fsf@ashishki-desk.ger.corp.intel.com>
Date:	Wed, 30 Sep 2015 13:16:15 +0300
From:	Alexander Shishkin <alexander.shishkin@...ux.intel.com>
To:	Mathieu Poirier <mathieu.poirier@...aro.org>,
	gregkh@...uxfoundation.org, a.p.zijlstra@...llo.nl,
	acme@...nel.org, mingo@...hat.com, corbet@....net
Cc:	adrian.hunter@...el.com, zhang.chunyan@...aro.org,
	mike.leach@....com, tor@...com, al.grant@....com,
	pawel.moll@....com, linux-arm-kernel@...ts.infradead.org,
	linux-doc@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [RFC PATCH 19/20] coresight: etm3x: implementing perf's user/kernel mode

Mathieu Poirier <mathieu.poirier@...aro.org> writes:

> Configure tracers in accordance with the specification conveyed
> by the perf cmd line tool.  For example if only user space is
> requested, configure the address range comparator with the kerne's
> address range and set the 'exclude' bit, which will result in
> tracing everything except the kernel.
>
> Signed-off-by: Mathieu Poirier <mathieu.poirier@...aro.org>
> ---
>  drivers/hwtracing/coresight/coresight-etm3x.c | 36 +++++++++++++++++++++++++++
>  1 file changed, 36 insertions(+)
>
> diff --git a/drivers/hwtracing/coresight/coresight-etm3x.c b/drivers/hwtracing/coresight/coresight-etm3x.c
> index 077b49714259..2f818dbde099 100644
> --- a/drivers/hwtracing/coresight/coresight-etm3x.c
> +++ b/drivers/hwtracing/coresight/coresight-etm3x.c
> @@ -320,6 +320,41 @@ static int etm_parse_event_config(struct etm_drvdata *drvdata,
>  {
>  	u64 config = event->attr.config;
>  
> +	if (event->attr.exclude_kernel || event->attr.exclude_user) {
> +		u32 event_encoding;
> +		u32 flags = (1 << 0 | /* instruction execute*/
> +			     3 << 3 | /* ARM instruction */
> +			     0 << 5 | /* No data value comparison */
> +			     0 << 7 | /* No exact mach */
> +			     0 << 8 | /* Ignore context ID */
> +			     0 << 10); /* Security ignored */
> +
> +		/* Bit 0 is address range comparator 1 */
> +		drvdata->enable_ctrl1 = ETMTECR1_ADDR_COMP_1;
> +
> +		/* Bit 24 controls whether the address range should be
> +		 * included or excluded.
> +		 */
> +		if (event->attr.exclude_kernel)
> +			drvdata->enable_ctrl1 |= BIT(24);

Isn't there a privilege level based filtering (OS/USR) in ETM? Shouldn't
ETMACTRn[10:12] have a setting for that?

> +
> +		/* No need to worry about single address comparators */
> +		drvdata->enable_ctrl2 = 0x0;
> +
> +		drvdata->addr_val[0] = (u32) _stext;
> +		drvdata->addr_val[1] = (u32) _etext;

This doesn't cover kernel modules, afaict.

> +		drvdata->addr_acctype[0] = flags;
> +		drvdata->addr_acctype[1] = flags;
> +		drvdata->addr_type[0] = ETM_ADDR_TYPE_RANGE;
> +		drvdata->addr_type[1] = ETM_ADDR_TYPE_RANGE;
> +
> +		event_encoding = 0x00 << 14 | /* Boolean function select A */
> +				 0x01 << 4  | /* Addr range comparator 0-7 */
> +				 0x00 << 0;   /* Addr range comparator 1 */
> +
> +		drvdata->enable_event = event_encoding;
> +	}
> +
>  	/*
>  	 * At this time only cycle accurate and timestamp options are
>  	 * available.  As such clear everything else that may have been
> @@ -362,6 +397,7 @@ static void etm_configure_cpu(void *info)
>  	etm_writel(drvdata, drvdata->startstop_ctrl, ETMTSSCR);
>  	etm_writel(drvdata, drvdata->enable_event, ETMTEEVR);
>  	etm_writel(drvdata, drvdata->enable_ctrl1, ETMTECR1);
> +	etm_writel(drvdata, drvdata->enable_ctrl2, ETMTECR2);
>  	etm_writel(drvdata, drvdata->fifofull_level, ETMFFLR);
>  	for (i = 0; i < drvdata->nr_addr_cmp; i++) {
>  		etm_writel(drvdata, drvdata->addr_val[i], ETMACVRn(i));
> -- 
> 1.9.1
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