[PATCH] perf test bpf: Skip test if kernel-debuginfo is not present

[Athira Rajeev]

> On 13-Dec-2022, at 12:27 AM, Arnaldo Carvalho de Melo <acme at kernel.org> wrote:
> 
> Em Thu, Nov 03, 2022 at 12:27:01PM +0530, Athira Rajeev escreveu:
>>> On 28-Oct-2022, at 9:12 PM, Kajol Jain <kjain at linux.ibm.com> wrote:
>>> 
>>> Perf BPF filter test fails in environment where "kernel-debuginfo"
>>> is not installed.
>>> 
>>> Test failure logs:
>>> <<>>
>>> 42: BPF filter                            :
>>> 42.1: Basic BPF filtering                 : Ok
>>> 42.2: BPF pinning                         : Ok
>>> 42.3: BPF prologue generation             : FAILED!
>>> <<>>
>>> 
>>> Enabling verbose option provided debug logs, which says debuginfo
>>> needs to be installed. Snippet of verbose logs:
>>> 
>>> <<>>
>>> 42.3: BPF prologue generation                                       :
>>> --- start ---
>>> test child forked, pid 28218
>>> <<>>
>>> Rebuild with CONFIG_DEBUG_INFO=y, or install an appropriate debuginfo
>>> package.
>>> bpf_probe: failed to convert perf probe events
>>> Failed to add events selected by BPF
>>> test child finished with -1
>>> ---- end ----
>>> BPF filter subtest 3: FAILED!
>>> <<>>
>>> 
>>> Here subtest, "BPF prologue generation" failed and
>>> logs shows debuginfo is needed. After installing
>>> kernel-debuginfo package, testcase passes.
>>> 
>>> Subtest "BPF prologue generation" failed because, the "do_test"
>>> function returns "TEST_FAIL" without checking the error type
>>> returned by "parse_events_load_bpf_obj" function.
>>> Function parse_events_load_bpf_obj can also return error of type
>>> "-ENOENT" incase kernel-debuginfo package is not installed. Fix this
>>> by adding check for -ENOENT error.
>>> 
>>> Test result after the patch changes:
>>> 
>>> Test failure logs:
>>> <<>>
>>> 42: BPF filter                 :
>>> 42.1: Basic BPF filtering      : Ok
>>> 42.2: BPF pinning              : Ok
>>> 42.3: BPF prologue generation  : Skip (clang/debuginfo isn't
>>> installed or environment missing BPF support)
>>> 
>>> Fixes: ba1fae431e74bb42 ("perf test: Add 'perf test BPF'")
>>> Signed-off-by: Kajol Jain <kjain at linux.ibm.com>
>>> Reviewed-by: Madhavan Srinivasan <maddy at linux.ibm.com>
>>> ---
>>> tools/perf/tests/bpf.c | 6 +++++-
>>> 1 file changed, 5 insertions(+), 1 deletion(-)
>>> 
>>> diff --git a/tools/perf/tests/bpf.c b/tools/perf/tests/bpf.c
>>> index 17c023823713..57cecadc1da2 100644
>>> --- a/tools/perf/tests/bpf.c
>>> +++ b/tools/perf/tests/bpf.c
>>> @@ -126,6 +126,10 @@ static int do_test(struct bpf_object *obj, int (*func)(void),
>>> 
>>> 	err = parse_events_load_bpf_obj(&parse_state, &parse_state.list, obj, NULL);
>>> 	parse_events_error__exit(&parse_error);
>>> +	if (err == -ENOENT) {
>>> +		pr_debug("Failed to add events selected by BPF, debuginfo package not installed\n");
>>> +		return TEST_SKIP;
>>> +	}
>> 
>> Hi Kajol,
>> 
>> Here, you have used ENOENT to skip the test. But there could be other places in the code path for “parse_events_load_bpf_obj”
>> which also returns ENOENT. In that case, for any exit that returns ENOENT, test will get skipped.
>> 
>> Can we look at the logs, example we have this in commit logs:
>> 
>> 	Rebuild with CONFIG_DEBUG_INFO=y, or install an appropriate debuginfo
>> 	package.
>> 
>> so as to decide whether to skip for debug info ?
> 
> Kajol?
> 
> - Arnaldo

Hi Arnaldo, looking for your suggestion on how to handle the case where debuginfo is missing.

Here the bpf test fails because of missing debuginfo. The function which goes through the debuginfo check is "parse_events_load_bpf_obj" . parse_events_load_bpf_obj internally calls "open_debuginfo" which returns ENOENT when debuginfo is missing. The patch fix from Kajol is to skip the test using error code ENOENT for debuginfo.

But issue with using this return code is that, there are other places in the code path for "parse_events_load_bpf_obj"
which also returns ENOENT. In that case, for any exit path that returns ENOENT, test will get skipped.
Hence looking for an alternative way to identify missing debuginfo to skip the test. Please share your thoughts on this.

Thanks
Athira


> 
>> Thanks
>> Athira
>> 
>>> 	if (err || list_empty(&parse_state.list)) {
>>> 		pr_debug("Failed to add events selected by BPF\n");
>>> 		return TEST_FAIL;
>>> @@ -368,7 +372,7 @@ static struct test_case bpf_tests[] = {
>>> 			"clang isn't installed or environment missing BPF support"),
>>> #ifdef HAVE_BPF_PROLOGUE
>>> 	TEST_CASE_REASON("BPF prologue generation", bpf_prologue_test,
>>> -			"clang isn't installed or environment missing BPF support"),
>>> +			"clang/debuginfo isn't installed or environment missing BPF support"),
>>> #else
>>> 	TEST_CASE_REASON("BPF prologue generation", bpf_prologue_test, "not compiled in"),
>>> #endif
>>> -- 
>>> 2.31.1