bpf/tests: Allow different number of runs per test case

This patch allows a test cast to specify the number of runs to use. For
compatibility with existing test case definitions, the default value 0
is interpreted as MAX_TESTRUNS.

A reduced number of runs is useful for complex test programs where 1000
runs may take a very long time. Instead of reducing what is tested, one
can instead reduce the number of times the test is run.

Signed-off-by: Johan Almbladh <johan.almbladh@anyfinetworks.com>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Link: https://lore.kernel.org/bpf/20210914091842.4186267-2-johan.almbladh@anyfinetworks.com

lib/test_bpf.c

@@ -80,6 +80,7 @@ struct bpf_test {
 	int expected_errcode; /* used when FLAG_EXPECTED_FAIL is set in the aux */
 	__u8 frag_data[MAX_DATA];
 	int stack_depth; /* for eBPF only, since tests don't call verifier */
+	int nr_testruns; /* Custom run count, defaults to MAX_TESTRUNS if 0 */
 };
 
 /* Large test cases need separate allocation and fill handler. */
@@ -8631,6 +8632,9 @@ static int run_one(const struct bpf_prog *fp, struct bpf_test *test)
 {
 	int err_cnt = 0, i, runs = MAX_TESTRUNS;
 
+	if (test->nr_testruns)
+		runs = min(test->nr_testruns, MAX_TESTRUNS);
+
 	for (i = 0; i < MAX_SUBTESTS; i++) {
 		void *data;
 		u64 duration;