[PATCH] tools/perf/tests: Skip perf BPF test if clang is not present

[Athira Rajeev]

> On 05-May-2022, at 10:51 PM, Arnaldo Carvalho de Melo <acme at kernel.org> wrote:
> 
> Em Thu, May 05, 2022 at 03:30:39PM +0530, Athira Rajeev escreveu:
>> Perf BPF filter test fails in environment where "clang"
>> is not installed.
>> 
>> Test failure logs:
>> 
>> <<>>
>> 42: BPF filter                    :
>> 42.1: Basic BPF filtering         : Skip
>> 42.2: BPF pinning                 : FAILED!
>> 42.3: BPF prologue generation     : FAILED!
>> <<>>
>> 
>> Enabling verbose option provided debug logs which says
>> clang/llvm needs to be installed. Snippet of verbose logs:
>> 
>> <<>>
>> 42.2: BPF pinning                  :
>> --- start ---
>> test child forked, pid 61423
>> ERROR:	unable to find clang.
>> Hint:	Try to install latest clang/llvm to support BPF.
>>        Check your $PATH
>> 
>> <<logs_here>>
>> 
>> Failed to compile test case: 'Basic BPF llvm compile'
>> Unable to get BPF object, fix kbuild first
>> test child finished with -1
>> ---- end ----
>> BPF filter subtest 2: FAILED!
>> <<>>
>> 
>> Here subtests, "BPF pinning" and "BPF prologue generation"
>> failed and logs shows clang/llvm is needed. After installing
>> clang, testcase passes.
>> 
>> Reason on why subtest failure happens though logs has proper
>> debug information:
>> Main function __test__bpf calls test_llvm__fetch_bpf_obj by
>> passing 4th argument as true ( 4th arguments maps to parameter
>> "force" in test_llvm__fetch_bpf_obj ). But this will cause
>> test_llvm__fetch_bpf_obj to skip the check for clang/llvm.
>> 
>> Snippet of code part which checks for clang based on
>> parameter "force" in test_llvm__fetch_bpf_obj:
>> 
>> <<>>
>> if (!force && (!llvm_param.user_set_param &&
>> <<>>
>> 
>> Since force is set to "false", test won't get skipped and
>> fails to compile test case. The BPF code compilation needs
>> clang, So pass the fourth argument as "false" and also skip
>> the test if reason for return is "TEST_SKIP"
>> 
>> After the patch:
>> 
>> <<>>
>> 42: BPF filter                    :
>> 42.1: Basic BPF filtering         : Skip
>> 42.2: BPF pinning                 : Skip
>> 42.3: BPF prologue generation     : Skip
>> <<>>
> 
> Wouldn't it be better to add the reason for the skip, like other tests
> do?
> 
> E.g.:
> 
> 23: Watchpoint                                                      :
> 23.1: Read Only Watchpoint                                          : Skip (missing hardware support)
> 23.2: Write Only Watchpoint                                         : Ok
> 23.3: Read / Write Watchpoint                                       : Ok
> 23.4: Modify Watchpoint
> 
> Something like:
> 
> After the patch:
> 
> <<>>
> 42: BPF filter                    :
> 42.1: Basic BPF filtering         : Skip (clang not installed)
> 42.2: BPF pinning                 : Skip (clang not installed)
> 42.3: BPF prologue generation     : Skip (clang not installed)


Hi Arnaldo,

I tried to use TEST_CASE_REASON("BPF pinning", bpf_pinning, "clang not installed")

The clang check is done in test_llvm__fetch_bpf_obj under some condition checks:

<<>>
         /*
         * Skip this test if user's .perfconfig doesn't set [llvm] section
         * and clang is not found in $PATH
         */
        if (!force && (!llvm_param.user_set_param &&
                       llvm__search_clang())) {
                pr_debug("No clang, skip this test\n");
                return TEST_SKIP;
        }
<<>>

But the reason for BPF skip could happen at other places also ie non-root user, bpf support checks from check_env.
So can't exactly print the skip reason to be clang since It could get skipped from other environment checks too. Any suggestions Arnaldo ?

Thanks
Athira

> <<>>
> 
>> Signed-off-by: Athira Rajeev <atrajeev at linux.vnet.ibm.com>
>> ---
>> tools/perf/tests/bpf.c | 4 ++--
>> 1 file changed, 2 insertions(+), 2 deletions(-)
>> 
>> diff --git a/tools/perf/tests/bpf.c b/tools/perf/tests/bpf.c
>> index 57b9591f7cbb..ae62f01239e3 100644
>> --- a/tools/perf/tests/bpf.c
>> +++ b/tools/perf/tests/bpf.c
>> @@ -222,11 +222,11 @@ static int __test__bpf(int idx)
>> 
>> 	ret = test_llvm__fetch_bpf_obj(&obj_buf, &obj_buf_sz,
>> 				       bpf_testcase_table[idx].prog_id,
>> -				       true, NULL);
>> +				       false, NULL);
>> 	if (ret != TEST_OK || !obj_buf || !obj_buf_sz) {
>> 		pr_debug("Unable to get BPF object, %s\n",
>> 			 bpf_testcase_table[idx].msg_compile_fail);
>> -		if (idx == 0)
>> +		if ((idx == 0) || (ret == TEST_SKIP))
>> 			return TEST_SKIP;
>> 		else
>> 			return TEST_FAIL;
>> -- 
>> 2.35.1
> 
> -- 
> 
> - Arnaldo