[PATCH 16/18] perf metric: Add recursion check when processing nested metrics

[Jiri Olsa <jolsa@kernel.org>]

Keeping the stack of nested metrics via 'struct expr_id' objecs
and checking if we are in recursion via already processed metric.

The stack is implemented as static array within the struct egroup
with 100 entries, which should be enough nesting depth for any
metric we have or plan to have at the moment.

Adding test that simulates the recursion and checks we can
detect it.

Signed-off-by: Jiri Olsa <jolsa@kernel.org>
---
 tools/perf/tests/parse-metric.c |  27 ++++++++-
 tools/perf/util/expr.c          |   2 +
 tools/perf/util/expr.h          |   9 ++-
 tools/perf/util/metricgroup.c   | 101 +++++++++++++++++++++++++++++---
 4 files changed, 128 insertions(+), 11 deletions(-)

diff --git a/tools/perf/tests/parse-metric.c b/tools/perf/tests/parse-metric.c
index b50e2a3f3b73..238a805edd55 100644
--- a/tools/perf/tests/parse-metric.c
+++ b/tools/perf/tests/parse-metric.c
@@ -57,6 +57,14 @@ static struct pmu_event pme_test[] = {
 	.metric_expr	= "d_ratio(DCache_L2_All_Miss, DCache_L2_All)",
 	.metric_name	= "DCache_L2_Misses",
 },
+{
+	.metric_expr	= "IPC + M2",
+	.metric_name	= "M1",
+},
+{
+	.metric_expr	= "IPC + M1",
+	.metric_name	= "M2",
+},
 };
 
 static struct pmu_events_map map = {
@@ -139,8 +147,8 @@ static int compute_metric(const char *name, struct value *vals, double *ratio)
 	err = metricgroup__parse_groups_test(evlist, &map, name,
 					     false, false,
 					     &metric_events);
-
-	TEST_ASSERT_VAL("failed to parse metric", err == 0);
+	if (err)
+		return err;
 
 	if (perf_evlist__alloc_stats(evlist, false))
 		return -1;
@@ -264,11 +272,26 @@ static int test_dcache_l2(void)
 	return 0;
 }
 
+static int test_recursion_fail(void)
+{
+	double ratio;
+	struct value vals[] = {
+		{ .event = "inst_retired.any",        .val = 300 },
+		{ .event = "cpu_clk_unhalted.thread", .val = 200 },
+		{ 0 },
+	};
+
+	TEST_ASSERT_VAL("failed to find recursion",
+			compute_metric("M1", vals, &ratio) == -1);
+	return 0;
+}
+
 int test__parse_metric(struct test *test __maybe_unused, int subtest __maybe_unused)
 {
 	TEST_ASSERT_VAL("IPC failed", test_ipc() == 0);
 	TEST_ASSERT_VAL("frontend failed", test_frontend() == 0);
 	TEST_ASSERT_VAL("cache_miss_cycles failed", test_cache_miss_cycles() == 0);
 	TEST_ASSERT_VAL("DCache_L2 failed", test_dcache_l2() == 0);
+	TEST_ASSERT_VAL("recursion fail failed", test_recursion_fail() == 0);
 	return 0;
 }
diff --git a/tools/perf/util/expr.c b/tools/perf/util/expr.c
index 2784df38f8c2..d23d8897bc61 100644
--- a/tools/perf/util/expr.c
+++ b/tools/perf/util/expr.c
@@ -45,6 +45,8 @@ int expr__add_id(struct expr_parse_ctx *ctx, const char *id)
 	if (!data_ptr)
 		return -ENOMEM;
 
+	data_ptr->parent = ctx->parent;
+
 	ret = hashmap__set(&ctx->ids, id, data_ptr,
 			   (const void **)&old_key, (void **)&old_data);
 	free(old_key);
diff --git a/tools/perf/util/expr.h b/tools/perf/util/expr.h
index b6d1fba64eaa..e5fdeab928c7 100644
--- a/tools/perf/util/expr.h
+++ b/tools/perf/util/expr.h
@@ -13,8 +13,14 @@
 
 struct metric_ref;
 
+struct expr_id {
+	char		*id;
+	struct expr_id	*parent;
+};
+
 struct expr_parse_ctx {
-	struct hashmap ids;
+	struct hashmap	 ids;
+	struct expr_id	*parent;
 };
 
 struct expr_id_data {
@@ -27,6 +33,7 @@ struct expr_id_data {
 			const char *metric_expr;
 			bool counted;
 		} ref;
+		struct expr_id	*parent;
 	};
 };
 
diff --git a/tools/perf/util/metricgroup.c b/tools/perf/util/metricgroup.c
index 66f25362702d..69ec20dd737b 100644
--- a/tools/perf/util/metricgroup.c
+++ b/tools/perf/util/metricgroup.c
@@ -24,6 +24,7 @@
 #include <subcmd/parse-options.h>
 #include <api/fs/fs.h>
 #include "util.h"
+#include <asm/bug.h>
 
 struct metric_event *metricgroup__lookup(struct rblist *metric_events,
 					 struct evsel *evsel,
@@ -109,6 +110,8 @@ struct metric_ref_node {
 	struct list_head list;
 };
 
+#define RECURSION_ID_MAX 100
+
 struct egroup {
 	struct list_head nd;
 	struct expr_parse_ctx pctx;
@@ -119,6 +122,11 @@ struct egroup {
 	int refs_cnt;
 	int runtime;
 	bool has_constraint;
+
+	struct {
+		struct expr_id	id[RECURSION_ID_MAX];
+		int		cnt;
+	} recursion;
 };
 
 /**
@@ -609,7 +617,8 @@ static int __add_metric(struct list_head *group_list,
 			struct pmu_event *pe,
 			bool metric_no_group,
 			int runtime,
-		        struct egroup **egp)
+			struct egroup **egp,
+			struct expr_id *parent)
 {
 	struct metric_ref_node *ref;
 	struct egroup *eg;
@@ -619,7 +628,7 @@ static int __add_metric(struct list_head *group_list,
 		 * We got in here for the master group,
 		 * allocate it and put it on the list.
 		 */
-		eg = malloc(sizeof(*eg));
+		eg = zalloc(sizeof(*eg));
 		if (!eg)
 			return -ENOMEM;
 
@@ -632,6 +641,16 @@ static int __add_metric(struct list_head *group_list,
 		INIT_LIST_HEAD(&eg->refs);
 		eg->refs_cnt = 0;
 		*egp = eg;
+
+		/* Initialize first recursion exr id with base name. */
+		parent = &eg->recursion.id[0];
+		eg->recursion.cnt = 1;
+
+		parent->id = strdup(pe->metric_name);
+		if (!parent->id) {
+			free(eg);
+			return -ENOMEM;
+		}
 	} else {
 		/*
 		 * We got here for the referenced metric, via the
@@ -651,6 +670,10 @@ static int __add_metric(struct list_head *group_list,
 		eg->has_constraint |= metricgroup__has_constraint(pe);
 	}
 
+	/* Force all found IDs in metric to have us as parent ID. */
+	WARN_ON_ONCE(!parent);
+	eg->pctx.parent = parent;
+
 	/*
 	 * For both the master and referenced metrics, we parse
 	 * all the metric's IDs and add it to the parent context.
@@ -707,10 +730,56 @@ static struct pmu_event *find_metric(const char *metric, struct pmu_events_map *
 	return NULL;
 }
 
+static int recursion_check(struct egroup *eg, const char *id, struct expr_id **parent)
+{
+	struct expr_id_data *data;
+	struct expr_id *p;
+	int ret;
+
+	/*
+	 * We get the parent referenced by 'id' argument and
+	 * traverse through all the parent object IDs to check
+	 * if we already processed 'id', if we did, it's recursion
+	 * and we fail.
+	 */
+	ret = expr__get_id(&eg->pctx, id, &data);
+	if (ret)
+		return ret;
+
+	p = data->parent;
+
+	while (p->parent) {
+		if (!strcmp(p->id, id)) {
+			pr_err("failed: recursion detected for %s\n", id);
+			return -1;
+		}
+		p = p->parent;
+	}
+
+	/*
+	 * If we are over the limit of static entris, the metric
+	 * is too difficult/nested to process, fail as well.
+	 */
+	if (eg->recursion.cnt + 1 >= RECURSION_ID_MAX) {
+		pr_err("failed: too many nested metrics\n");
+		return -EINVAL;
+	}
+
+	p = &eg->recursion.id[eg->recursion.cnt];
+	eg->recursion.cnt++;
+
+	p->id     = strdup(id);
+	p->parent = data->parent;
+	*parent   = p;
+
+	return p->id ? 0 : -ENOMEM;
+}
+
 static int add_metric(struct list_head *group_list,
 		      struct pmu_event *pe,
 		      bool metric_no_group,
-		      struct egroup **egp);
+		      struct egroup **egp,
+		      struct expr_id *parent);
 
 static int resolve_metric(struct egroup *eg,
 			  bool metric_no_group,
@@ -729,18 +798,23 @@ static int resolve_metric(struct egroup *eg,
 	do {
 		all = true;
 		hashmap__for_each_entry((&eg->pctx.ids), cur, bkt) {
+			struct expr_id *parent;
 			struct pmu_event *pe;
 
 			pe = find_metric(cur->key, map);
 			if (!pe)
 				continue;
 
+			ret = recursion_check(eg, cur->key, &parent);
+			if (ret)
+				return ret;
+
 			all = false;
 			/* The metric key itself needs to go out.. */
 			expr__del_id(&eg->pctx, cur->key);
 
 			/* ... and it gets resolved to the parent context. */
-			ret = add_metric(group_list, pe, metric_no_group, &eg);
+			ret = add_metric(group_list, pe, metric_no_group, &eg, parent);
 			if (ret)
 				return ret;
 
@@ -758,14 +832,15 @@ static int resolve_metric(struct egroup *eg,
 static int add_metric(struct list_head *group_list,
 		      struct pmu_event *pe,
 		      bool metric_no_group,
-		      struct egroup **egp)
+		      struct egroup **egp,
+		      struct expr_id *parent)
 {
 	int ret = 0;
 
 	pr_debug("metric expr %s for %s\n", pe->metric_expr, pe->metric_name);
 
 	if (!strstr(pe->metric_expr, "?")) {
-		ret = __add_metric(group_list, pe, metric_no_group, 1, egp);
+		ret = __add_metric(group_list, pe, metric_no_group, 1, egp, parent);
 	} else {
 		int j, count;
 
@@ -777,7 +852,7 @@ static int add_metric(struct list_head *group_list,
 		 */
 
 		for (j = 0; j < count && !ret; j++) {
-			ret = __add_metric(group_list, pe, metric_no_group, j, egp);
+			ret = __add_metric(group_list, pe, metric_no_group, j, egp, parent);
 		}
 	}
 
@@ -798,7 +873,7 @@ static int metricgroup__add_metric(const char *metric, bool metric_no_group,
 	if (!pe)
 		return -EINVAL;
 
-	ret = add_metric(group_list, pe, metric_no_group, &eg);
+	ret = add_metric(group_list, pe, metric_no_group, &eg, NULL);
 	if (ret)
 		return ret;
 
@@ -871,11 +946,21 @@ static void egroup__free_refs(struct egroup *egroup)
 	}
 }
 
+static void egroup__free_recursion(struct egroup *egroup)
+{
+	int i;
+
+	for (i = 0; i < egroup->recursion.cnt; i++) {
+		free(egroup->recursion.id[i].id);
+	}
+}
+
 static void metricgroup__free_egroups(struct list_head *group_list)
 {
 	struct egroup *eg, *egtmp;
 
 	list_for_each_entry_safe (eg, egtmp, group_list, nd) {
+		egroup__free_recursion(eg);
 		egroup__free_refs(eg);
 		expr__ctx_clear(&eg->pctx);
 		list_del_init(&eg->nd);
-- 
2.25.4