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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: James Clark <james.clark@arm.com>
Reviewed-by: Mike Leach <mike.leach@linaro.org>
Signed-off-by: Suzuki K Poulose <suzuki.poulose@arm.com>
Link: https://lore.kernel.org/r/20220511144601.2257870-2-james.clark@arm.com
This commit is contained in:
James Clark 2022-05-11 15:45:58 +01:00 committed by Suzuki K Poulose
parent c06475910b
commit 2d693ed436
3 changed files with 18 additions and 0 deletions
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2
drivers/hwtracing/coresight/coresight-etm-perf.c
View File

@ -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,
};

14
drivers/hwtracing/coresight/coresight-etm4x-core.c
View File

@ -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;
}

2
include/linux/coresight-pmu.h
View File

@ -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