The BPF filter needs libbpf/BPF-skeleton support and root privilege.
Add error messages to help users understand the problem easily.
When it's not build with BPF support (make BUILD_BPF_SKEL=0).
$ sudo perf record -e cycles --filter "pid != 0" true
Error: BPF filter is requested but perf is not built with BPF.
Please make sure to build with libbpf and BPF skeleton.
Usage: perf record [<options>] [<command>]
or: perf record [<options>] -- <command> [<options>]
--filter <filter>
event filter
When it supports BPF but runs without root or CAP_BPF. Note that it
also checks pinned BPF filters.
$ perf record -e cycles --filter "pid != 0" -o /dev/null true
Error: BPF filter only works for users with the CAP_BPF capability!
Please run 'perf record --setup-filter pin' as root first.
Usage: perf record [<options>] [<command>]
or: perf record [<options>] -- <command> [<options>]
--filter <filter>
event filter
Reviewed-by: Ian Rogers <irogers@google.com>
Link: https://lore.kernel.org/r/20250604174835.1852481-1-namhyung@kernel.org
Signed-off-by: Namhyung Kim <namhyung@kernel.org>
Add utilities to help checking capabilities of the running procss. Make
perf link with libcap, if it is available. If no libcap-dev[el],
fallback to the geteuid() == 0 test used before.
Committer notes:
$ perf test python
18: 'import perf' in python : FAILED!
$ perf test -v python
Couldn't bump rlimit(MEMLOCK), failures may take place when creating BPF maps, etc
18: 'import perf' in python :
--- start ---
test child forked, pid 23288
Traceback (most recent call last):
File "<stdin>", line 1, in <module>
ImportError: /tmp/build/perf/python/perf.so: undefined symbol: cap_get_flag
test child finished with -1
---- end ----
'import perf' in python: FAILED!
$
This happens because differently from the perf binary generated with
this patch applied:
$ ldd /tmp/build/perf/perf | grep libcap
libcap.so.2 => /lib64/libcap.so.2 (0x00007f724a4ef000)
$
The python binding isn't linking with libcap:
$ ldd /tmp/build/perf/python/perf.so | grep libcap
$
So add 'cap' to the 'extra_libraries' variable in
tools/perf/util/setup.py, and rebuild:
$ perf test python
18: 'import perf' in python : Ok
$
If we explicitely disable libcap it also continues to work:
$ make NO_LIBCAP=1 -C tools/perf O=/tmp/build/perf install-bin
$ ldd /tmp/build/perf/perf | grep libcap
$ ldd /tmp/build/perf/python/perf.so | grep libcap
$ perf test python
18: 'import perf' in python : Ok
$
Signed-off-by: Igor Lubashev <ilubashe@akamai.com>
Acked-by: Jiri Olsa <jolsa@kernel.org>
Cc: Alexander Shishkin <alexander.shishkin@linux.intel.com>
Cc: Alexey Budankov <alexey.budankov@linux.intel.com>
Cc: James Morris <jmorris@namei.org>
Cc: Mathieu Poirier <mathieu.poirier@linaro.org>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Suzuki Poulouse <suzuki.poulose@arm.com>
Cc: linux-arm-kernel@lists.infradead.org
[ split from a larger patch ]
Link: http://lkml.kernel.org/r/8a1e76cf5c7c9796d0d4d240fbaa85305298aafa.1565188228.git.ilubashe@akamai.com
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>
