perf tools: Fixup exit path when not able to open events

We have to deal with the TUI mode in perf top, so that we don't end up
with a garbled screen when, say, a non root user on a machine with a
paranoid setting (the default) tries to use 'perf top'.

Introduce a ui__warning_paranoid() routine shared by top and record that
tells the user the valid values for /proc/sys/kernel/perf_event_paranoid.

Cc: David Ahern <daahern@cisco.com>
Cc: Frederic Weisbecker <fweisbec@gmail.com>
Cc: Ingo Molnar <mingo@elte.hu>
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>
LKML-Reference: <new-submission>
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>

4 files changed, 39 insertions, 19 deletions

diff --git a/tools/perf/builtin-record.c b/tools/perf/builtin-record.c
index 6febcc168a8c..623695e18254 100644
--- a/tools/perf/builtin-record.c
+++ b/tools/perf/builtin-record.c
@@ -275,11 +275,10 @@ try_again:
                                      !no_inherit) < 0) {
                         int err = errno;
 
-                        if (err == EPERM || err == EACCES)
-                                die("Permission error - are you root?\n"
-                                        "\t Consider tweaking"
-                                        " /proc/sys/kernel/perf_event_paranoid.\n");
-                        else if (err ==  ENODEV && cpu_list) {
+                        if (err == EPERM || err == EACCES) {
+                                ui__warning_paranoid();
+                                exit(EXIT_FAILURE);
+                        } else if (err ==  ENODEV && cpu_list) {
                                 die("No such device - did you specify"
                                         " an out-of-range profile CPU?\n");
                         } else if (err == EINVAL && sample_id_all_avail) {
diff --git a/tools/perf/builtin-top.c b/tools/perf/builtin-top.c
index 676b4fb0070f..935fc4fd878e 100644
--- a/tools/perf/builtin-top.c
+++ b/tools/perf/builtin-top.c
@@ -850,10 +850,10 @@ try_again:
                                      top.evlist->threads, group, inherit) < 0) {
                         int err = errno;
 
-                        if (err == EPERM || err == EACCES)
-                                die("Permission error - are you root?\n"
-                                        "\t Consider tweaking"
-                                        " /proc/sys/kernel/perf_event_paranoid.\n");
+                        if (err == EPERM || err == EACCES) {
+                                ui__warning_paranoid();
+                                goto out_err;
+                        }
                         /*
                          * If it's cycles then fall back to hrtimer
                          * based cpu-clock-tick sw counter, which
@@ -861,25 +861,35 @@ try_again:
                          */
                         if (attr->type == PERF_TYPE_HARDWARE &&
                             attr->config == PERF_COUNT_HW_CPU_CYCLES) {
-
                                 if (verbose)
-                                        warning(" ... trying to fall back to cpu-clock-ticks\n");
+                                        ui__warning("Cycles event not supported,\n"
+                                                    "trying to fall back to cpu-clock-ticks\n");
 
                                 attr->type = PERF_TYPE_SOFTWARE;
                                 attr->config = PERF_COUNT_SW_CPU_CLOCK;
                                 goto try_again;
                         }
-                        printf("\n");
-                        error("sys_perf_event_open() syscall returned with %d "
-                              "(%s).  /bin/dmesg may provide additional information.\n",
-                              err, strerror(err));
-                        die("No CONFIG_PERF_EVENTS=y kernel support configured?\n");
-                        exit(-1);
+
+                        ui__warning("The sys_perf_event_open() syscall "
+                                    "returned with %d (%s).  /bin/dmesg "
+                                    "may provide additional information.\n"
+                                    "No CONFIG_PERF_EVENTS=y kernel support "
+                                    "configured?\n", err, strerror(err));
+                        goto out_err;
                 }
         }
 
-        if (perf_evlist__mmap(evlist, mmap_pages, false) < 0)
-                die("failed to mmap with %d (%s)\n", errno, strerror(errno));
+        if (perf_evlist__mmap(evlist, mmap_pages, false) < 0) {
+                ui__warning("Failed to mmap with %d (%s)\n",
+                            errno, strerror(errno));
+                goto out_err;
+        }
+
+        return;
+
+out_err:
+        exit_browser(0);
+        exit(0);
 }
 
 static int __cmd_top(void)
diff --git a/tools/perf/util/debug.c b/tools/perf/util/debug.c
index d4536a9e0d8c..155749d74350 100644
--- a/tools/perf/util/debug.c
+++ b/tools/perf/util/debug.c
@@ -57,6 +57,16 @@ void ui__warning(const char *format, ...)
 }
 #endif
 
+void ui__warning_paranoid(void)
+{
+        ui__warning("Permission error - are you root?\n"
+                    "Consider tweaking /proc/sys/kernel/perf_event_paranoid:\n"
+                    " -1 - Not paranoid at all\n"
+                    "  0 - Disallow raw tracepoint access for unpriv\n"
+                    "  1 - Disallow cpu events for unpriv\n"
+                    "  2 - Disallow kernel profiling for unpriv\n");
+}
+
 void trace_event(union perf_event *event)
 {
         unsigned char *raw_event = (void *)event;
diff --git a/tools/perf/util/debug.h b/tools/perf/util/debug.h
index 93516cf4682c..fd53db47e3de 100644
--- a/tools/perf/util/debug.h
+++ b/tools/perf/util/debug.h
@@ -36,5 +36,6 @@ int ui_helpline__show_help(const char *format, va_list ap);
 #endif
 
 void ui__warning(const char *format, ...) __attribute__((format(printf, 1, 2)));
+void ui__warning_paranoid(void);
 
 #endif  /* __PERF_DEBUG_H */