Commit 2d693ed4 authored by James Clark's avatar James Clark Committed by Suzuki K Poulose
Browse files

coresight: Add config flag to enable branch broadcast 



When enabled, all taken branch addresses are output, even if the branch
was because of a direct branch instruction. This enables reconstruction
of the program flow without having access to the memory image of the
code being executed.

Use bit 8 for the config option which would be the correct bit for
programming ETMv3. Although branch broadcast can't be enabled on ETMv3
because it's not in the define ETM3X_SUPPORTED_OPTIONS, using the
correct bit might help prevent future collisions or allow it to be
enabled if needed.

Signed-off-by: default avatarJames Clark <james.clark@arm.com>
Reviewed-by: default avatarMike Leach <mike.leach@linaro.org>
Signed-off-by: default avatarSuzuki K Poulose <suzuki.poulose@arm.com>
Link: https://lore.kernel.org/r/20220511144601.2257870-2-james.clark@arm.com
parent c0647591

drivers/hwtracing/coresight/coresight-etm-perf.c

+2 −0
Original line number Diff line number Diff line
@@ -52,6 +52,7 @@ static DEFINE_PER_CPU(struct coresight_device *, csdev_src); 
 * The PMU formats were orignally for ETMv3.5/PTM's ETMCR 'config';

 * now take them as general formats and apply on all ETMs.

 */

PMU_FORMAT_ATTR(branch_broadcast, "config:"__stringify(ETM_OPT_BRANCH_BROADCAST));

PMU_FORMAT_ATTR(cycacc,		"config:" __stringify(ETM_OPT_CYCACC));

/* contextid1 enables tracing CONTEXTIDR_EL1 for ETMv4 */

PMU_FORMAT_ATTR(contextid1,	"config:" __stringify(ETM_OPT_CTXTID));
@@ -97,6 +98,7 @@ static struct attribute *etm_config_formats_attr[] = { 
	&format_attr_sinkid.attr,

	&format_attr_preset.attr,

	&format_attr_configid.attr,

	&format_attr_branch_broadcast.attr,

	NULL,

};

drivers/hwtracing/coresight/coresight-etm4x-core.c

+14 −0
Original line number Diff line number Diff line
@@ -696,6 +696,20 @@ static int etm4_parse_event_config(struct coresight_device *csdev, 
		ret = cscfg_csdev_enable_active_config(csdev, cfg_hash, preset);

	}



	/* branch broadcast - enable if selected and supported */

	if (attr->config & BIT(ETM_OPT_BRANCH_BROADCAST)) {

		if (!drvdata->trcbb) {

			/*

			 * Missing BB support could cause silent decode errors

			 * so fail to open if it's not supported.

			 */

			ret = -EINVAL;

			goto out;

		} else {

			config->cfg |= BIT(ETM4_CFG_BIT_BB);

		}

	}



out:

	return ret;

}

include/linux/coresight-pmu.h

+2 −0
Original line number Diff line number Diff line
@@ -18,6 +18,7 @@ 
 * ETMv3.5/PTM doesn't define ETMCR config bits with prefix "ETM3_" and

 * directly use below macros as config bits.

 */

#define ETM_OPT_BRANCH_BROADCAST 8

#define ETM_OPT_CYCACC		12

#define ETM_OPT_CTXTID		14

#define ETM_OPT_CTXTID2		15
@@ -25,6 +26,7 @@ 
#define ETM_OPT_RETSTK		29



/* ETMv4 CONFIGR programming bits for the ETM OPTs */

#define ETM4_CFG_BIT_BB         3

#define ETM4_CFG_BIT_CYCACC	4

#define ETM4_CFG_BIT_CTXTID	6

#define ETM4_CFG_BIT_VMID	7