kernel/linux.git/tools/perf/util/cap.c, branch v6.19.11

perf bpf-filter: Improve error messages

2025-06-09T18:18:17+00:00

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 [] [] or: perf record [] -- [] --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 [] [] or: perf record [] -- [] --filter event filter Reviewed-by: Ian Rogers Link: https://lore.kernel.org/r/20250604174835.1852481-1-namhyung@kernel.org Signed-off-by: Namhyung Kim

perf cap: Add __NR_capget to arch/x86 unistd

2024-10-28T16:04:52+00:00

As there are duplicated kernel headers in tools/include libc can pick up the wrong definitions. This was causing the wrong system call for capget in perf. Reported-by: Adrian Hunter Fixes: e25ebda78e230283 ("perf cap: Tidy up and improve capability testing") Closes: https://lore.kernel.org/lkml/cc7d6bdf-1aeb-4179-9029-4baf50b59342@intel.com/ Signed-off-by: Ian Rogers Tested-by: Adrian Hunter Cc: Alexander Shishkin Cc: Ingo Molnar Cc: Jiri Olsa Cc: Kan Liang Cc: Mark Rutland Cc: Namhyung Kim Cc: Peter Zijlstra Link: https://lore.kernel.org/r/20241026055448.312247-1-irogers@google.com Signed-off-by: Arnaldo Carvalho de Melo

perf cap: Tidy up and improve capability testing

2024-08-20T20:53:12+00:00

Remove dependence on libcap. libcap is only used to query whether a capability is supported, which is just 1 capget system call. If the capget system call fails, fall back on root permission checking. Previously if libcap fails then the permission is assumed not present which may be pessimistic/wrong. Add a used_root out argument to perf_cap__capable to say whether the fall back root check was used. This allows the correct error message, "root" vs "users with the CAP_PERFMON or CAP_SYS_ADMIN capability", to be selected. Tidy uses of perf_cap__capable so that tests aren't repeated if capget isn't supported. Signed-off-by: Ian Rogers Cc: Adrian Hunter Cc: Alexander Shishkin Cc: Athira Rajeev Cc: Changbin Du Cc: Ingo Molnar Cc: James Clark Cc: Jiri Olsa Cc: Kan Liang Cc: Leo Yan Cc: Mark Rutland Cc: Namhyung Kim Cc: Oliver Upton Cc: Peter Zijlstra Link: https://lore.kernel.org/r/20240806220614.831914-1-irogers@google.com Signed-off-by: Arnaldo Carvalho de Melo

perf tools: Add helpers to use capabilities if present

2019-08-14T13:48:39+00:00

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 "", line 1, in 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 Acked-by: Jiri Olsa Cc: Alexander Shishkin Cc: Alexey Budankov Cc: James Morris Cc: Mathieu Poirier Cc: Namhyung Kim Cc: Peter Zijlstra Cc: Suzuki Poulouse 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