selftests/bpf: implement and test custom testmod_seq iterator

Implement a trivial iterator returning same specified integer value
N times as part of bpf_testmod kernel module. Add selftests to validate
everything works end to end.

We also reuse these tests as "verification-only" tests to validate that
kernel prints the state of custom kernel module-defined iterator correctly:

  fp-16=iter_testmod_seq(ref_id=1,state=drained,depth=0)

"testmod_seq" part is an iterator type, and is coming from module's BTF
data dynamically at runtime.

Signed-off-by: Andrii Nakryiko <andrii@kernel.org>
Link: https://lore.kernel.org/r/20230308184121.1165081-9-andrii@kernel.org
Signed-off-by: Alexei Starovoitov <ast@kernel.org>

1 files changed, 42 insertions, 0 deletions

diff --git a/tools/testing/selftests/bpf/prog_tests/iters.c b/tools/testing/selftests/bpf/prog_tests/iters.c
index 2e7caff9523e..10804ae5ae97 100644
--- a/tools/testing/selftests/bpf/prog_tests/iters.c
+++ b/tools/testing/selftests/bpf/prog_tests/iters.c
@@ -7,6 +7,7 @@
 #include "iters_state_safety.skel.h"
 #include "iters_looping.skel.h"
 #include "iters_num.skel.h"
+#include "iters_testmod_seq.skel.h"
 
 static void subtest_num_iters(void)
 {
@@ -53,12 +54,53 @@ cleanup:
 	iters_num__destroy(skel);
 }
 
+static void subtest_testmod_seq_iters(void)
+{
+	struct iters_testmod_seq *skel;
+	int err;
+
+	if (!env.has_testmod) {
+		test__skip();
+		return;
+	}
+
+	skel = iters_testmod_seq__open_and_load();
+	if (!ASSERT_OK_PTR(skel, "skel_open_and_load"))
+		return;
+
+	err = iters_testmod_seq__attach(skel);
+	if (!ASSERT_OK(err, "skel_attach"))
+		goto cleanup;
+
+	usleep(1);
+	iters_testmod_seq__detach(skel);
+
+#define VALIDATE_CASE(case_name)					\
+	ASSERT_EQ(skel->bss->res_##case_name,				\
+		  skel->rodata->exp_##case_name,			\
+		  #case_name)
+
+	VALIDATE_CASE(empty);
+	VALIDATE_CASE(full);
+	VALIDATE_CASE(truncated);
+
+#undef VALIDATE_CASE
+
+cleanup:
+	iters_testmod_seq__destroy(skel);
+}
+
 void test_iters(void)
 {
 	RUN_TESTS(iters_state_safety);
 	RUN_TESTS(iters_looping);
 	RUN_TESTS(iters);
 
+	if (env.has_testmod)
+		RUN_TESTS(iters_testmod_seq);
+
 	if (test__start_subtest("num"))
 		subtest_num_iters();
+	if (test__start_subtest("testmod_seq"))
+		subtest_testmod_seq_iters();
 }