perf top: Handle kptr_restrict

Reported-by: Ingo Molnar <mingo@elte.hu>
Cc: Frederic Weisbecker <fweisbec@gmail.com>
Cc: Mike Galbraith <efault@gmx.de>
Cc: Paul Mackerras <paulus@samba.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Stephane Eranian <eranian@google.com>
Cc: Tom Zanussi <tzanussi@gmail.com>
Link: http://lkml.kernel.org/n/tip-cyl5zmi1nu35vyu7l5im2pyv@git.kernel.org
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>

1 files changed, 15 insertions, 0 deletions

diff --git a/tools/perf/builtin-top.c b/tools/perf/builtin-top.c
index 375ed160d936..472f62790022 100644
--- a/tools/perf/builtin-top.c
+++ b/tools/perf/builtin-top.c
@@ -80,6 +80,7 @@ static bool			use_tui, use_stdio;
 
 static int                      default_interval                =      0;
 
+static bool                     kptr_restrict_warned;
 static bool                     inherit                         =  false;
 static int                      realtime_prio                   =      0;
 static bool                     group                           =  false;
@@ -738,6 +739,20 @@ static void perf_event__process_sample(const union perf_event *event,
             al.filtered)
                 return;
 
+        if (!kptr_restrict_warned &&
+            symbol_conf.kptr_restrict &&
+            al.cpumode == PERF_RECORD_MISC_KERNEL) {
+                ui__warning(
+"Kernel address maps (/proc/{kallsyms,modules}) are restricted.\n\n"
+"Check /proc/sys/kernel/kptr_restrict.\n\n"
+"Kernel%s samples will not be resolved.\n",
+                          !RB_EMPTY_ROOT(&al.map->dso->symbols[MAP__FUNCTION]) ?
+                          " modules" : "");
+                if (use_browser <= 0)
+                        sleep(5);
+                kptr_restrict_warned = true;
+        }
+
         if (al.sym == NULL) {
                 /*
                  * As we do lazy loading of symtabs we only will know if the