On Tue, 29 Sep 2020 at 17:54, Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx> wrote: > > From: Stephane Eranian <eranian@xxxxxxxxxx> > > [ Upstream commit bec49a9e05db3dbdca696fa07c62c52638fb6371 ] > > When it is not possible for a non-privilege perf command to monitor at > the kernel level (:k), the fallback code forces a :u. That works if the > event was previously monitoring both levels. But if the event was > already constrained to kernel only, then it does not make sense to > restrict it to user only. > > Given the code works by exclusion, a kernel only event would have: > > attr->exclude_user = 1 > > The fallback code would add: > > attr->exclude_kernel = 1 > > In the end the end would not monitor in either the user level or kernel > level. In other words, it would count nothing. > > An event programmed to monitor kernel only cannot be switched to user > only without seriously warning the user. > > This patch forces an error in this case to make it clear the request > cannot really be satisfied. > > Behavior with paranoid 1: > > $ sudo bash -c "echo 1 > /proc/sys/kernel/perf_event_paranoid" > $ perf stat -e cycles:k sleep 1 > > Performance counter stats for 'sleep 1': > > 1,520,413 cycles:k > > 1.002361664 seconds time elapsed > > 0.002480000 seconds user > 0.000000000 seconds sys > > Old behavior with paranoid 2: > > $ sudo bash -c "echo 2 > /proc/sys/kernel/perf_event_paranoid" > $ perf stat -e cycles:k sleep 1 > Performance counter stats for 'sleep 1': > > 0 cycles:ku > > 1.002358127 seconds time elapsed > > 0.002384000 seconds user > 0.000000000 seconds sys > > New behavior with paranoid 2: > > $ sudo bash -c "echo 2 > /proc/sys/kernel/perf_event_paranoid" > $ perf stat -e cycles:k sleep 1 > Error: > You may not have permission to collect stats. > > Consider tweaking /proc/sys/kernel/perf_event_paranoid, > which controls use of the performance events system by > unprivileged users (without CAP_PERFMON or CAP_SYS_ADMIN). > > The current value is 2: > > -1: Allow use of (almost) all events by all users > Ignore mlock limit after perf_event_mlock_kb without CAP_IPC_LOCK > >= 0: Disallow ftrace function tracepoint by users without CAP_PERFMON or CAP_SYS_ADMIN > Disallow raw tracepoint access by users without CAP_SYS_PERFMON or CAP_SYS_ADMIN > >= 1: Disallow CPU event access by users without CAP_PERFMON or CAP_SYS_ADMIN > >= 2: Disallow kernel profiling by users without CAP_PERFMON or CAP_SYS_ADMIN > > To make this setting permanent, edit /etc/sysctl.conf too, e.g.: > > kernel.perf_event_paranoid = -1 > > v2 of this patch addresses the review feedback from jolsa@xxxxxxxxxx. > > Signed-off-by: Stephane Eranian <eranian@xxxxxxxxxx> > Reviewed-by: Ian Rogers <irogers@xxxxxxxxxx> > Acked-by: Jiri Olsa <jolsa@xxxxxxxxxx> > Tested-by: Arnaldo Carvalho de Melo <acme@xxxxxxxxxx> > Cc: Alexander Shishkin <alexander.shishkin@xxxxxxxxxxxxxxx> > Cc: Jiri Olsa <jolsa@xxxxxxxxxx> > Cc: Mark Rutland <mark.rutland@xxxxxxx> > Cc: Namhyung Kim <namhyung@xxxxxxxxxx> > Cc: Peter Zijlstra <peterz@xxxxxxxxxxxxx> > Link: http://lore.kernel.org/lkml/20200414161550.225588-1-irogers@xxxxxxxxxx > Signed-off-by: Arnaldo Carvalho de Melo <acme@xxxxxxxxxx> > Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx> perf failed on stable rc branch 4.19 on all devices. Reported-by: Naresh Kamboju <naresh.kamboju@xxxxxxxxxx> build warning and errors, ----------------------------------- In file included from util/evlist.h:15:0, from util/evsel.c:30: util/evsel.c: In function 'perf_evsel__exit': util/util.h:25:28: warning: passing argument 1 of 'free' discards 'const' qualifier from pointer target type [-Wdiscarded-qualifiers] #define zfree(ptr) ({ free(*ptr); *ptr = NULL; }) ^ util/evsel.c:1293:2: note: in expansion of macro 'zfree' zfree(&evsel->pmu_name); ^~~~~ In file included from /srv/oe/build/tmp-lkft-glibc/work/intel_corei7_64-linaro-linux/perf/1.0-r9/perf-1.0/tools/perf/arch/x86/include/perf_regs.h:5:0, from util/perf_regs.h:27, from util/event.h:11, from util/callchain.h:8, from util/evsel.c:26: perf/1.0-r9/recipe-sysroot/usr/include/stdlib.h:563:13: note: expected 'void *' but argument is of type 'const char *' extern void free (void *__ptr) __THROW; ^~~~ util/evsel.c: In function 'perf_evsel__fallback': util/evsel.c:2802:14: error: 'struct perf_evsel' has no member named 'core'; did you mean 'node'? if (evsel->core.attr.exclude_user) ^~~~ node > --- > tools/perf/util/evsel.c | 4 ++++ > 1 file changed, 4 insertions(+) > > diff --git a/tools/perf/util/evsel.c b/tools/perf/util/evsel.c > index 68c5ab0e1800b..e8586957562b3 100644 > --- a/tools/perf/util/evsel.c > +++ b/tools/perf/util/evsel.c > @@ -2796,6 +2796,10 @@ bool perf_evsel__fallback(struct perf_evsel *evsel, int err, > char *new_name; > const char *sep = ":"; > > + /* If event has exclude user then don't exclude kernel. */ > + if (evsel->core.attr.exclude_user) > + return false; > + > /* Is there already the separator in the name. */ > if (strchr(name, '/') || > strchr(name, ':')) > -- > 2.25.1 > > >
