Date:   Mon, 13 Mar 2023 14:40:50 -0600
From:   Ross Zwisler <zwisler@google.com>
To:     Steven Rostedt <rostedt@goodmis.org>
Cc:     zwisler@kernel.org, bpf@vger.kernel.org,
        linux-kernel@vger.kernel.org, Alexei Starovoitov <ast@kernel.org>,
        Andrii Nakryiko <andrii@kernel.org>,
        Daniel Borkmann <daniel@iogearbox.net>,
        Hao Luo <haoluo@google.com>, Jason Gunthorpe <jgg@ziepe.ca>,
        Jiri Olsa <jolsa@kernel.org>,
        John Fastabend <john.fastabend@gmail.com>,
        KP Singh <kpsingh@kernel.org>,
        Leon Romanovsky <leon@kernel.org>,
        Martin KaFai Lau <martin.lau@linux.dev>,
        Mykola Lysenko <mykolal@fb.com>, Shuah Khan <shuah@kernel.org>,
        Song Liu <song@kernel.org>,
        Stanislav Fomichev <sdf@google.com>,
        Yonghong Song <yhs@fb.com>, linux-kselftest@vger.kernel.org,
        linux-rdma@vger.kernel.org, linux-trace-kernel@vger.kernel.org,
        "Michael S . Tsirkin" <mst@redhat.com>
Subject: Re: [PATCH bpf-next v3 2/2] selftests/bpf: use canonical ftrace path
Message-ID: <20230313204050.GA592900@google.com>
References: <20230310175209.2130880-1-zwisler@kernel.org>
 <20230310175209.2130880-2-zwisler@kernel.org>
 <20230310183352.2943e633@gandalf.local.home>
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On Fri, Mar 10, 2023 at 06:33:52PM -0500, Steven Rostedt wrote:
> On Fri, 10 Mar 2023 10:52:09 -0700
> zwisler@kernel.org wrote:
> 
> > diff --git a/tools/testing/selftests/bpf/get_cgroup_id_user.c b/tools/testing/selftests/bpf/get_cgroup_id_user.c
> > index 156743cf5870..4fa61ac8a0ee 100644
> > --- a/tools/testing/selftests/bpf/get_cgroup_id_user.c
> > +++ b/tools/testing/selftests/bpf/get_cgroup_id_user.c
> > @@ -86,8 +86,12 @@ int main(int argc, char **argv)
> >  	pid = getpid();
> >  	bpf_map_update_elem(pidmap_fd, &key, &pid, 0);
> >  
> > -	snprintf(buf, sizeof(buf),
> > -		 "/sys/kernel/debug/tracing/events/%s/id", probe_name);
> > +	if (access("/sys/kernel/tracing/trace", F_OK) == 0)
> > +		snprintf(buf, sizeof(buf),
> > +			 "/sys/kernel/tracing/events/%s/id", probe_name);
> > +	else
> > +		snprintf(buf, sizeof(buf),
> > +			 "/sys/kernel/debug/tracing/events/%s/id", probe_name);
> 
> I don't know how the BPF folks feel, but I do know some kernel developers
> prefer that if you need to break a single command into multiple lines that
> you then need to add brackets around it. As it makes it easier to read.
> 
> 	if (access("/sys/kernel/tracing/trace", F_OK) == 0) {
> 		snprintf(buf, sizeof(buf),
> 			 "/sys/kernel/tracing/events/%s/id", probe_name);
> 	} else {
> 		snprintf(buf, sizeof(buf),
> 			 "/sys/kernel/debug/tracing/events/%s/id", probe_name);
> 	}
> 
> 
> 
> >  	efd = open(buf, O_RDONLY, 0);
> >  	if (CHECK(efd < 0, "open", "err %d errno %d\n", efd, errno))
> >  		goto close_prog;
> > diff --git a/tools/testing/selftests/bpf/prog_tests/kprobe_multi_test.c b/tools/testing/selftests/bpf/prog_tests/kprobe_multi_test.c
> > index 113dba349a57..22be0a9a5a0a 100644
> > --- a/tools/testing/selftests/bpf/prog_tests/kprobe_multi_test.c
> > +++ b/tools/testing/selftests/bpf/prog_tests/kprobe_multi_test.c
> > @@ -338,7 +338,12 @@ static int get_syms(char ***symsp, size_t *cntp, bool kernel)
> >  	 * Filtering out duplicates by using hashmap__add, which won't
> >  	 * add existing entry.
> >  	 */
> > -	f = fopen("/sys/kernel/debug/tracing/available_filter_functions", "r");
> > +
> > +	if (access("/sys/kernel/tracing/trace", F_OK) == 0)
> > +		f = fopen("/sys/kernel/tracing/available_filter_functions", "r");
> > +	else
> > +		f = fopen("/sys/kernel/debug/tracing/available_filter_functions", "r");
> > +
> >  	if (!f)
> >  		return -EINVAL;
> >  
> > diff --git a/tools/testing/selftests/bpf/prog_tests/task_fd_query_tp.c b/tools/testing/selftests/bpf/prog_tests/task_fd_query_tp.c
> > index c717741bf8b6..60f92fd3c37a 100644
> > --- a/tools/testing/selftests/bpf/prog_tests/task_fd_query_tp.c
> > +++ b/tools/testing/selftests/bpf/prog_tests/task_fd_query_tp.c
> > @@ -17,8 +17,12 @@ static void test_task_fd_query_tp_core(const char *probe_name,
> >  	if (CHECK(err, "bpf_prog_test_load", "err %d errno %d\n", err, errno))
> >  		goto close_prog;
> >  
> > -	snprintf(buf, sizeof(buf),
> > -		 "/sys/kernel/debug/tracing/events/%s/id", probe_name);
> > +	if (access("/sys/kernel/tracing/trace", F_OK) == 0)
> > +		snprintf(buf, sizeof(buf),
> > +			 "/sys/kernel/tracing/events/%s/id", probe_name);
> > +	else
> > +		snprintf(buf, sizeof(buf),
> > +			 "/sys/kernel/debug/tracing/events/%s/id", probe_name);
> 
> Same here.
> 
> >  	efd = open(buf, O_RDONLY, 0);
> >  	if (CHECK(efd < 0, "open", "err %d errno %d\n", efd, errno))
> >  		goto close_prog;
> > diff --git a/tools/testing/selftests/bpf/prog_tests/tp_attach_query.c b/tools/testing/selftests/bpf/prog_tests/tp_attach_query.c
> > index 770fcc3bb1ba..d3e377fa8e9b 100644
> > --- a/tools/testing/selftests/bpf/prog_tests/tp_attach_query.c
> > +++ b/tools/testing/selftests/bpf/prog_tests/tp_attach_query.c
> > @@ -16,8 +16,12 @@ void serial_test_tp_attach_query(void)
> >  	for (i = 0; i < num_progs; i++)
> >  		obj[i] = NULL;
> >  
> > -	snprintf(buf, sizeof(buf),
> > -		 "/sys/kernel/debug/tracing/events/sched/sched_switch/id");
> > +	if (access("/sys/kernel/tracing/trace", F_OK) == 0)
> > +		snprintf(buf, sizeof(buf),
> > +			 "/sys/kernel/tracing/events/sched/sched_switch/id");
> > +	else
> > +		snprintf(buf, sizeof(buf),
> > +			 "/sys/kernel/debug/tracing/events/sched/sched_switch/id");
> 
> and here.
> 
> But perhaps the BPF folks don't care?

Sure, I agree that this is more readable.  I'll gather your Reviewed-by for
patch #1, make this change, rebase to the current bpf/bpf-next and send out
v4.