Re: [PATCH 00/14] bpf: Add trampoline and dispatcher to /proc/kallsyms

On Mon, Feb 10, 2020 at 04:51:08PM +0100, Björn Töpel wrote:

On Sat, 8 Feb 2020 at 16:42, Jiri Olsa [off-list ref] wrote:

quoted

hi,
this patchset adds trampoline and dispatcher objects
to be visible in /proc/kallsyms. The last patch also
adds sorting for all bpf objects in /proc/kallsyms.

Thanks for working on this!

I'm probably missing something with my perf setup; I've applied your
patches, and everything seem to work fine from an kallsyms
perspective:

# grep bpf_dispatcher_xdp /proc/kallsyms
...
ffffffffc0511000 t bpf_dispatcher_xdp   [bpf]

However, when I run
# perf top

I still see the undecorated one:
0.90%  [unknown]                  [k] 0xffffffffc0511037

Any ideas?

heya,
the code is little rusty and needs some fixing :-\

with the patch below on top of Arnaldo's perf/urgent branch,
there's one workaround for now:

  # perf record --vmlinux /proc/kallsyms 
  ^C[ perf record: Woken up 0 times to write data ]
  [ perf record: Captured and wrote 18.954 MB perf.data (348693 samples) ]

  # perf report --kallsyms /proc/kallsyms | grep bpf_trampoline_13795
     0.01%  sched-messaging  kallsyms                                [k] bpf_trampoline_13795
     0.00%  perf             kallsyms                                [k] bpf_trampoline_13795
     0.00%  :47547           kallsyms                                [k] bpf_trampoline_13795
     0.00%  :47546           kallsyms                                [k] bpf_trampoline_13795
     0.00%  :47544           kallsyms                                [k] bpf_trampoline_13795

with recent kcore/vmlinux changes we neglected kallsyms fallback,
I'm preparing changes that will detect and use it automaticaly

jirka


---

diff --git a/tools/perf/util/machine.c b/tools/perf/util/machine.c
index fb5c2cd44d30..463ada5117f8 100644
--- a/tools/perf/util/machine.c
+++ b/tools/perf/util/machine.c

@@ -742,6 +742,7 @@ static int machine__process_ksymbol_register(struct machine *machine,
 		map->start = event->ksymbol.addr;
 		map->end = map->start + event->ksymbol.len;
 		maps__insert(&machine->kmaps, map);
+		dso__set_loaded(dso);
 	}
 
 	sym = symbol__new(map->map_ip(map, map->start),