[PATCH v3 1/3] perf: Skip and warn on unknown format 'configN' attrs

[Rob Herring]

If the kernel exposes a new perf_event_attr field in a format attr, perf
will return an error stating the specified PMU can't be found. For
example, a format attr with 'config3:0-63' causes an error as config3 is
unknown to perf. This causes a compatibility issue between a newer
kernel with older perf tool.

Before this change with a kernel adding 'config3' I get:

$ perf record -e arm_spe// -- true
event syntax error: 'arm_spe//'
                     \___ Cannot find PMU `arm_spe'. Missing kernel support?
Run 'perf list' for a list of valid events

 Usage: perf record [<options>] [<command>]
    or: perf record [<options>] -- <command> [<options>]

    -e, --event <event>   event selector. use 'perf list' to list
available events

After this change, I get:

$ perf record -e arm_spe// -- true
WARNING: 'arm_spe_0' format 'inv_event_filter' requires 'perf_event_attr::config3' which is not supported by this version of perf!
[ perf record: Woken up 2 times to write data ]
[ perf record: Captured and wrote 0.091 MB perf.data ]

To support unknown configN formats, rework the YACC implementation to
pass any config[0-9]+ format to perf_pmu__new_format() to handle with a
warning.

Cc: stable@xxxxxxxxxxxxxxx
Signed-off-by: Rob Herring <robh@xxxxxxxxxx>
---
v3:
 - Move warning from format scanning to when PMU is selected
 - Add and use PERF_PMU_FORMAT_VALUE_CONFIG_END

v2: https://lore.kernel.org/all/20220909204509.2169512-1-robh@xxxxxxxxxx/
 - Rework YACC code to handle configN formats in C code
 - Add a warning when an unknown configN attr is found

v1: https://lore.kernel.org/all/20220901184709.2179309-1-robh@xxxxxxxxxx/

diff --git a/tools/perf/util/parse-events.c b/tools/perf/util/parse-events.c
index f05e15acd33f..e2305fca0f95 100644
--- a/tools/perf/util/parse-events.c
+++ b/tools/perf/util/parse-events.c
@@ -215,6 +215,9 @@ __add_event(struct list_head *list, int *idx,
 	struct perf_cpu_map *cpus = pmu ? perf_cpu_map__get(pmu->cpus) :
 			       cpu_list ? perf_cpu_map__new(cpu_list) : NULL;
 
+	if (pmu)
+		perf_pmu__warn_invalid_formats(pmu);
+
 	if (pmu && attr->type == PERF_TYPE_RAW)
 		perf_pmu__warn_invalid_config(pmu, attr->config, name);
 
diff --git a/tools/perf/util/pmu.c b/tools/perf/util/pmu.c
index 89655d53117a..2a0d1415dd55 100644
--- a/tools/perf/util/pmu.c
+++ b/tools/perf/util/pmu.c
@@ -1005,6 +1005,19 @@ static struct perf_pmu *pmu_lookup(const char *lookup_name)
 	return NULL;
 }
 
+void perf_pmu__warn_invalid_formats(struct perf_pmu *pmu)
+{
+	struct perf_pmu_format *format;
+
+	list_for_each_entry(format, &pmu->format, list)
+		if (format->value >= PERF_PMU_FORMAT_VALUE_CONFIG_END) {
+			pr_warning("WARNING: '%s' format '%s' requires 'perf_event_attr::config%d'"
+				   "which is not supported by this version of perf!\n",
+				   pmu->name, format->name, format->value);
+			return;
+		}
+}
+
 static struct perf_pmu *pmu_find(const char *name)
 {
 	struct perf_pmu *pmu;
diff --git a/tools/perf/util/pmu.h b/tools/perf/util/pmu.h
index a7b0f9507510..68e15c38ae71 100644
--- a/tools/perf/util/pmu.h
+++ b/tools/perf/util/pmu.h
@@ -17,6 +17,7 @@ enum {
 	PERF_PMU_FORMAT_VALUE_CONFIG,
 	PERF_PMU_FORMAT_VALUE_CONFIG1,
 	PERF_PMU_FORMAT_VALUE_CONFIG2,
+	PERF_PMU_FORMAT_VALUE_CONFIG_END,
 };
 
 #define PERF_PMU_FORMAT_BITS 64
@@ -139,6 +140,7 @@ int perf_pmu__caps_parse(struct perf_pmu *pmu);
 
 void perf_pmu__warn_invalid_config(struct perf_pmu *pmu, __u64 config,
 				   const char *name);
+void perf_pmu__warn_invalid_formats(struct perf_pmu *pmu);
 
 bool perf_pmu__has_hybrid(void);
 int perf_pmu__match(char *pattern, char *name, char *tok);
diff --git a/tools/perf/util/pmu.l b/tools/perf/util/pmu.l
index a15d9fbd7c0e..58b4926cfaca 100644
--- a/tools/perf/util/pmu.l
+++ b/tools/perf/util/pmu.l
@@ -27,8 +27,6 @@ num_dec         [0-9]+
 
 {num_dec}	{ return value(10); }
 config		{ return PP_CONFIG; }
-config1		{ return PP_CONFIG1; }
-config2		{ return PP_CONFIG2; }
 -		{ return '-'; }
 :		{ return ':'; }
 ,		{ return ','; }
diff --git a/tools/perf/util/pmu.y b/tools/perf/util/pmu.y
index bfd7e8509869..283efe059819 100644
--- a/tools/perf/util/pmu.y
+++ b/tools/perf/util/pmu.y
@@ -20,7 +20,7 @@ do { \
 
 %}
 
-%token PP_CONFIG PP_CONFIG1 PP_CONFIG2
+%token PP_CONFIG
 %token PP_VALUE PP_ERROR
 %type <num> PP_VALUE
 %type <bits> bit_term
@@ -47,18 +47,11 @@ PP_CONFIG ':' bits
 				      $3));
 }
 |
-PP_CONFIG1 ':' bits
+PP_CONFIG PP_VALUE ':' bits
 {
 	ABORT_ON(perf_pmu__new_format(format, name,
-				      PERF_PMU_FORMAT_VALUE_CONFIG1,
-				      $3));
-}
-|
-PP_CONFIG2 ':' bits
-{
-	ABORT_ON(perf_pmu__new_format(format, name,
-				      PERF_PMU_FORMAT_VALUE_CONFIG2,
-				      $3));
+				      $2,
+				      $4));
 }
 
 bits:

-- 
b4 0.10.0-dev