[PATCH bpf-next v2 1/2] selftests/bpf: Skip jit_insns_arena tests if not supported

[Tiezhu Yang]

When loading a BPF skeleton program via test_loader, certain test cases
such as jit_insns/cast_to_user may fail if the underlying hardware lacks
specific execution extensions required by newer features like BPF Arena.

Use libbpf_probe_bpf_map_type() in prog_tests/jit_insns.c to explicitly
check for BPF_MAP_TYPE_ARENA support before loading the jit_insns_arena
test skeleton. If the JIT backend or hardware does not support Arena,
cleanly report the subtest status as SKIPPED via test__skip().

This prevents false-alarm test failures on unsupported hardware while
preserving the core verification coverage for the rest of the standard
JIT instruction tests (such as alu_imm, alu_reg).

Before:
  $ sudo ./test_progs -a jit_insns/cast_to_user
  ...
  libbpf: map 'arena': failed to create: -EOPNOTSUPP
  run_subtest:FAIL:unexpected_load_failure unexpected error: -95 (errno 95)
  ...
  Summary: 0/0 PASSED, 0 SKIPPED, 1/1 FAILED

After:
  $ sudo ./test_progs -a jit_insns/cast_to_user
  ...
  Summary: 1/0 PASSED, 1 SKIPPED, 0/0 FAILED

Signed-off-by: Tiezhu Yang <yangtiezhu@xxxxxxxxxxx>
---
 tools/testing/selftests/bpf/prog_tests/jit_insns.c | 9 ++++++++-
 1 file changed, 8 insertions(+), 1 deletion(-)

diff --git a/tools/testing/selftests/bpf/prog_tests/jit_insns.c b/tools/testing/selftests/bpf/prog_tests/jit_insns.c
index 0aaab23a2eef..e8a0e5ec2d6b 100644
--- a/tools/testing/selftests/bpf/prog_tests/jit_insns.c
+++ b/tools/testing/selftests/bpf/prog_tests/jit_insns.c
@@ -3688,7 +3688,14 @@ static void test_tail_call(void)
 
 void test_jit_insns(void)
 {
-	RUN_TESTS(jit_insns_arena);
+	if (libbpf_probe_bpf_map_type(BPF_MAP_TYPE_ARENA, NULL)) {
+		RUN_TESTS(jit_insns_arena);
+	} else {
+		if (test__start_subtest("arena_zero_off"))
+			test__skip();
+		if (test__start_subtest("cast_to_user"))
+			test__skip();
+	}
 	if (test__start_subtest("alu_imm"))
 		test_alu_imm();
 	if (test__start_subtest("alu_reg"))
-- 
2.42.0