linux-kernel - [PATCH v2 2/3] perf parse-events: Improve error location of terms cloned from an event

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Date: Wed, 31 Jan 2024 05:49:39 -0800
From: Ian Rogers <irogers@...gle.com>
To: Peter Zijlstra <peterz@...radead.org>, Ingo Molnar <mingo@...hat.com>, 
	Arnaldo Carvalho de Melo <acme@...nel.org>, Namhyung Kim <namhyung@...nel.org>, 
	Mark Rutland <mark.rutland@....com>, 
	Alexander Shishkin <alexander.shishkin@...ux.intel.com>, Jiri Olsa <jolsa@...nel.org>, 
	Ian Rogers <irogers@...gle.com>, Adrian Hunter <adrian.hunter@...el.com>, 
	Kan Liang <kan.liang@...ux.intel.com>, James Clark <james.clark@....com>, 
	linux-perf-users@...r.kernel.org, linux-kernel@...r.kernel.org, 
	tchen168@....edu, Michael Petlan <mpetlan@...hat.com>
Subject: [PATCH v2 2/3] perf parse-events: Improve error location of terms
 cloned from an event

A PMU event/alias will have a set of format terms that replace it when
an event is parsed. The location of the terms is their position when
parsed for the event/alias either from sysfs or json. This location is
of little use when an event fails to parse as the error will be given
in terms of the location in the string of events parsed not the json
or sysfs string. Fix this by making the cloned terms location that of
the event/alias.

If a cloned term from an event/alias is invalid the bad format is hard
to determine from the error string. Add the name of the bad format
into the error string.

Signed-off-by: Ian Rogers <irogers@...gle.com>
---
These fixes were inspired by the poor error output in:
https://lore.kernel.org/linux-perf-users/alpine.LRH.2.20.2401300733310.11354@Diego/
---
 tools/perf/util/pmu.c | 9 +++++----
 1 file changed, 5 insertions(+), 4 deletions(-)

diff --git a/tools/perf/util/pmu.c b/tools/perf/util/pmu.c
index 355f813f960d..437386dedd5c 100644
--- a/tools/perf/util/pmu.c
+++ b/tools/perf/util/pmu.c
@@ -657,7 +657,7 @@ static int pmu_aliases_parse(struct perf_pmu *pmu)
 	return 0;
 }
 
-static int pmu_alias_terms(struct perf_pmu_alias *alias, struct list_head *terms)
+static int pmu_alias_terms(struct perf_pmu_alias *alias, int err_loc, struct list_head *terms)
 {
 	struct parse_events_term *term, *cloned;
 	struct parse_events_terms clone_terms;
@@ -675,6 +675,7 @@ static int pmu_alias_terms(struct perf_pmu_alias *alias, struct list_head *terms
 		 * which we don't want for implicit terms in aliases.
 		 */
 		cloned->weak = true;
+		cloned->err_term = cloned->err_val = err_loc;
 		list_add_tail(&cloned->list, &clone_terms.terms);
 	}
 	list_splice_init(&clone_terms.terms, terms);
@@ -1363,8 +1364,8 @@ static int pmu_config_term(const struct perf_pmu *pmu,
 
 			parse_events_error__handle(err, term->err_val,
 				asprintf(&err_str,
-				    "value too big for format, maximum is %llu",
-				    (unsigned long long)max_val) < 0
+				    "value too big for format (%s), maximum is %llu",
+				    format->name, (unsigned long long)max_val) < 0
 				    ? strdup("value too big for format")
 				    : err_str,
 				    NULL);
@@ -1518,7 +1519,7 @@ int perf_pmu__check_alias(struct perf_pmu *pmu, struct parse_events_terms *head_
 		alias = pmu_find_alias(pmu, term);
 		if (!alias)
 			continue;
-		ret = pmu_alias_terms(alias, &term->list);
+		ret = pmu_alias_terms(alias, term->err_term, &term->list);
 		if (ret) {
 			parse_events_error__handle(err, term->err_term,
 						strdup("Failure to duplicate terms"),
-- 
2.43.0.429.g432eaa2c6b-goog