On Tue, Sep 29, 2020 at 07:03:46PM +0530, Naresh Kamboju wrote: > 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 I thought Sasha had dropped all of the offending patches. I'll go drop this one and push out a new 4.19-rc release. But note, the latest 4.19.y tree doesn't even build perf for me, so I can't really check this locally :( thanks, greg k-h
