From 7d173913a6420f2818afeca70b268f064441f69b Mon Sep 17 00:00:00 2001 From: Arnaldo Carvalho de Melo Date: Thu, 12 May 2016 15:44:55 -0300 Subject: [PATCH] perf evsel: Improve EPERM error handling in open_strerror() We were showing a hardcoded default value for the kernel.perf_event_paranoid sysctl, now that it became more paranoid (1 -> 2 [1]), this would need to be updated, instead show the current value: [acme@jouet linux]$ perf record ls 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_SYS_ADMIN). The current value is 2: -1: Allow use of (almost) all events by all users >= 0: Disallow raw tracepoint access by users without CAP_IOC_LOCK >= 1: Disallow CPU event access by users without CAP_SYS_ADMIN >= 2: Disallow kernel profiling by users without CAP_SYS_ADMIN [acme@jouet linux]$ [1] 0161028b7c8a ("perf/core: Change the default paranoia level to 2") Reported-by: Ingo Molnar Cc: Adrian Hunter Cc: Andy Lutomirski Cc: David Ahern Cc: Jiri Olsa Cc: Kees Cook Cc: Linus Torvalds Cc: Masami Hiramatsu Cc: Namhyung Kim Cc: Peter Zijlstra Cc: Wang Nan Link: http://lkml.kernel.org/n/tip-0gc4rdpg8d025r5not8s8028@git.kernel.org Signed-off-by: Arnaldo Carvalho de Melo --- tools/perf/util/evsel.c | 5 +++-- 1 file changed, 3 insertions(+), 2 deletions(-) diff --git a/tools/perf/util/evsel.c b/tools/perf/util/evsel.c index 738ce226002b..a5f339d447cc 100644 --- a/tools/perf/util/evsel.c +++ b/tools/perf/util/evsel.c @@ -2382,12 +2382,13 @@ int perf_evsel__open_strerror(struct perf_evsel *evsel, struct target *target, "Consider tweaking /proc/sys/kernel/perf_event_paranoid,\n" "which controls use of the performance events system by\n" "unprivileged users (without CAP_SYS_ADMIN).\n\n" - "The default value is 1:\n\n" + "The current value is %d:\n\n" " -1: Allow use of (almost) all events by all users\n" ">= 0: Disallow raw tracepoint access by users without CAP_IOC_LOCK\n" ">= 1: Disallow CPU event access by users without CAP_SYS_ADMIN\n" ">= 2: Disallow kernel profiling by users without CAP_SYS_ADMIN", - target->system_wide ? "system-wide " : ""); + target->system_wide ? "system-wide " : "", + perf_event_paranoid()); case ENOENT: return scnprintf(msg, size, "The %s event is not supported.", perf_evsel__name(evsel)); -- 2.20.1