selftests/bpf: Test_progs option for getting number of tests

It can be practial to get the number of tests that test_progs contain.
This could for example be used to create a shell for-loop construct that
runs the individual tests.

Like:
 for N in $(seq 1 $(./test_progs -c)); do
   ./test_progs -n $N 2>&1 > result_test_${N}.log &
 done ; wait

V2: Add the ability to return the count for the selected tests. This is
useful for getting a count e.g. after excluding some tests with option -b.
The current beakers test script like to report the max test count upfront.

Signed-off-by: Jesper Dangaard Brouer <brouer@redhat.com>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Acked-by: Andrii Nakryiko <andriin@fb.com>
Link: https://lore.kernel.org/bpf/159363985244.930467.12617117873058936829.stgit@firesoul

tools/testing/selftests/bpf/test_progs.c

@@ -366,6 +366,7 @@ enum ARG_KEYS {
 	ARG_TEST_NAME_BLACKLIST = 'b',
 	ARG_VERIFIER_STATS = 's',
 	ARG_VERBOSE = 'v',
+	ARG_GET_TEST_CNT = 'c',
 };
 
 static const struct argp_option opts[] = {
@@ -379,6 +380,8 @@ static const struct argp_option opts[] = {
 	  "Output verifier statistics", },
 	{ "verbose", ARG_VERBOSE, "LEVEL", OPTION_ARG_OPTIONAL,
 	  "Verbose output (use -vv or -vvv for progressively verbose output)" },
+	{ "count", ARG_GET_TEST_CNT, NULL, 0,
+	  "Get number of selected top-level tests " },
 	{},
 };
 
@@ -511,6 +514,9 @@ static error_t parse_arg(int key, char *arg, struct argp_state *state)
 			}
 		}
 		break;
+	case ARG_GET_TEST_CNT:
+		env->get_test_cnt = true;
+		break;
 	case ARGP_KEY_ARG:
 		argp_usage(state);
 		break;
@@ -654,6 +660,11 @@ int main(int argc, char **argv)
 				test->test_num, test->test_name))
 			continue;
 
+		if (env.get_test_cnt) {
+			env.succ_cnt++;
+			continue;
+		}
+
 		test->run_test();
 		/* ensure last sub-test is finalized properly */
 		if (test->subtest_name)
@@ -677,9 +688,16 @@ int main(int argc, char **argv)
 			cleanup_cgroup_environment();
 	}
 	stdio_restore();
+
+	if (env.get_test_cnt) {
+		printf("%d\n", env.succ_cnt);
+		goto out;
+	}
+
 	fprintf(stdout, "Summary: %d/%d PASSED, %d SKIPPED, %d FAILED\n",
 		env.succ_cnt, env.sub_succ_cnt, env.skip_cnt, env.fail_cnt);
 
+out:
 	free_str_set(&env.test_selector.blacklist);
 	free_str_set(&env.test_selector.whitelist);
 	free(env.test_selector.num_set);

tools/testing/selftests/bpf/test_progs.h

@@ -66,6 +66,7 @@ struct test_env {
 	enum verbosity verbosity;
 
 	bool jit_enabled;
+	bool get_test_cnt;
 
 	struct prog_test_def *test;
 	FILE *stdout;