perf evsel: Introduce perf_evsel__open_strerror method

That consolidates the error messages in 'record', 'stat' and 'top', that
now get a consistent set of messages and allow other tools to use the
new method to report problems using whatever UI toolkit.

Cc: David Ahern <dsahern@gmail.com>
Cc: Frederic Weisbecker <fweisbec@gmail.com>
Cc: Jiri Olsa <jolsa@redhat.com>
Cc: Mike Galbraith <efault@gmx.de>
Cc: Namhyung Kim <namhyung@gmail.com>
Cc: Paul Mackerras <paulus@samba.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Stephane Eranian <eranian@google.com>
Link: http://lkml.kernel.org/n/tip-1cudb7wl996kz7ilz83ctvhr@git.kernel.org
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>

tools/perf/builtin-record.c

@@ -224,7 +224,7 @@ static bool perf_evlist__equal(struct perf_evlist *evlist,
 
 static int perf_record__open(struct perf_record *rec)
 {
-	char msg[128];
+	char msg[512];
 	struct perf_evsel *pos;
 	struct perf_evlist *evlist = rec->evlist;
 	struct perf_session *session = rec->session;
@@ -234,60 +234,18 @@ static int perf_record__open(struct perf_record *rec)
 	perf_evlist__config(evlist, opts);
 
 	list_for_each_entry(pos, &evlist->entries, node) {
-		struct perf_event_attr *attr = &pos->attr;
 try_again:
 		if (perf_evsel__open(pos, evlist->cpus, evlist->threads) < 0) {
-			int err = errno;
-
-			if (err == EPERM || err == EACCES) {
-				ui__error_paranoid();
-				rc = -err;
-				goto out;
-			} else if (err ==  ENODEV && opts->target.cpu_list) {
-				pr_err("No such device - did you specify"
-				       " an out-of-range profile CPU?\n");
-				rc = -err;
-				goto out;
-			}
-
-			if (perf_evsel__fallback(pos, err, msg, sizeof(msg))) {
+			if (perf_evsel__fallback(pos, errno, msg, sizeof(msg))) {
 				if (verbose)
 					ui__warning("%s\n", msg);
 				goto try_again;
 			}
 
-			if (err == ENOENT) {
-				ui__error("The %s event is not supported.\n",
-					  perf_evsel__name(pos));
-				rc = -err;
-				goto out;
-			} else if ((err == EOPNOTSUPP) && (attr->precise_ip)) {
-				ui__error("\'precise\' request may not be supported. "
-					  "Try removing 'p' modifier\n");
-				rc = -err;
-				goto out;
-			}
-
-			printf("\n");
-			error("sys_perf_event_open() syscall returned with %d "
-			      "(%s) for event %s. /bin/dmesg may provide "
-			      "additional information.\n",
-			      err, strerror(err), perf_evsel__name(pos));
-
-#if defined(__i386__) || defined(__x86_64__)
-			if (attr->type == PERF_TYPE_HARDWARE &&
-			    err == EOPNOTSUPP) {
-				pr_err("No hardware sampling interrupt available."
-				       " No APIC? If so then you can boot the kernel"
-				       " with the \"lapic\" boot parameter to"
-				       " force-enable it.\n");
-				rc = -err;
-				goto out;
-			}
-#endif
-
-			pr_err("No CONFIG_PERF_EVENTS=y kernel support configured?\n");
-			rc = -err;
+			rc = -errno;
+			perf_evsel__open_strerror(pos, &opts->target,
+						  errno, msg, sizeof(msg));
+			ui__error("%s\n", msg);
 			goto out;
 		}
 	}

tools/perf/builtin-stat.c

@@ -247,6 +247,7 @@ static int read_counter(struct perf_evsel *counter)
 
 static int __run_perf_stat(int argc __maybe_unused, const char **argv)
 {
+	char msg[512];
 	unsigned long long t0, t1;
 	struct perf_evsel *counter;
 	int status = 0;
@@ -324,20 +325,13 @@ static int __run_perf_stat(int argc __maybe_unused, const char **argv)
 				continue;
 			}
 
-			if (errno == EPERM || errno == EACCES) {
-				error("You may not have permission to collect %sstats.\n"
-				      "\t Consider tweaking"
-				      " /proc/sys/kernel/perf_event_paranoid or running as root.",
-				      target.system_wide ? "system-wide " : "");
-			} else {
-				error("open_counter returned with %d (%s). "
-				      "/bin/dmesg may provide additional information.\n",
-				       errno, strerror(errno));
-			}
+			perf_evsel__open_strerror(counter, &target,
+						  errno, msg, sizeof(msg));
+			ui__error("%s\n", msg);
+
 			if (child_pid != -1)
 				kill(child_pid, SIGTERM);
 
-			pr_err("Not all events could be opened.\n");
 			return -1;
 		}
 		counter->supported = true;

tools/perf/builtin-top.c

@@ -892,7 +892,7 @@ static void perf_top__mmap_read(struct perf_top *top)
 
 static void perf_top__start_counters(struct perf_top *top)
 {
-	char msg[128];
+	char msg[512];
 	struct perf_evsel *counter;
 	struct perf_evlist *evlist = top->evlist;
 	struct perf_record_opts *opts = &top->record_opts;
@@ -900,42 +900,18 @@ static void perf_top__start_counters(struct perf_top *top)
 	perf_evlist__config(evlist, opts);
 
 	list_for_each_entry(counter, &evlist->entries, node) {
-		struct perf_event_attr *attr = &counter->attr;
 try_again:
 		if (perf_evsel__open(counter, top->evlist->cpus,
 				     top->evlist->threads) < 0) {
-			int err = errno;
-
-			if (err == EPERM || err == EACCES) {
-				ui__error_paranoid();
-				goto out_err;
-			}
-
-			if (perf_evsel__fallback(counter, err, msg, sizeof(msg))) {
+			if (perf_evsel__fallback(counter, errno, msg, sizeof(msg))) {
 				if (verbose)
 					ui__warning("%s\n", msg);
 				goto try_again;
 			}
 
-			if (err == ENOENT) {
-				ui__error("The %s event is not supported.\n",
-					  perf_evsel__name(counter));
-				goto out_err;
-			} else if (err == EMFILE) {
-				ui__error("Too many events are opened.\n"
-					    "Try again after reducing the number of events\n");
-				goto out_err;
-			} else if ((err == EOPNOTSUPP) && (attr->precise_ip)) {
-				ui__error("\'precise\' request may not be supported. "
-					  "Try removing 'p' modifier\n");
-				goto out_err;
-			}
-
-			ui__error("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));
+			perf_evsel__open_strerror(counter, &opts->target,
+						  errno, msg, sizeof(msg));
+			ui__error("%s\n", msg);
 			goto out_err;
 		}
 	}

tools/perf/ui/util.c

@@ -52,17 +52,6 @@ int ui__warning(const char *format, ...)
 	return ret;
 }
 
-int ui__error_paranoid(void)
-{
-	return ui__error("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");
-}
-
-
 /**
  * perf_error__register - Register error logging functions
  * @eops: The pointer to error logging function struct

tools/perf/util/debug.h

@@ -16,6 +16,5 @@ void trace_event(union perf_event *event);
 
 int ui__error(const char *format, ...) __attribute__((format(printf, 1, 2)));
 int ui__warning(const char *format, ...) __attribute__((format(printf, 1, 2)));
-int ui__error_paranoid(void);
 
 #endif	/* __PERF_DEBUG_H */

tools/perf/util/evsel.c

@@ -1406,3 +1406,52 @@ bool perf_evsel__fallback(struct perf_evsel *evsel, int err,
 
 	return false;
 }
+
+int perf_evsel__open_strerror(struct perf_evsel *evsel,
+			      struct perf_target *target,
+			      int err, char *msg, size_t size)
+{
+	switch (err) {
+	case EPERM:
+	case EACCES:
+		return scnprintf(msg, size, "%s",
+		 "You may not have permission to collect %sstats.\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",
+				 target->system_wide ? "system-wide " : "");
+	case ENOENT:
+		return scnprintf(msg, size, "The %s event is not supported.",
+				 perf_evsel__name(evsel));
+	case EMFILE:
+		return scnprintf(msg, size, "%s",
+			 "Too many events are opened.\n"
+			 "Try again after reducing the number of events.");
+	case ENODEV:
+		if (target->cpu_list)
+			return scnprintf(msg, size, "%s",
+	 "No such device - did you specify an out-of-range profile CPU?\n");
+		break;
+	case EOPNOTSUPP:
+		if (evsel->attr.precise_ip)
+			return scnprintf(msg, size, "%s",
+	"\'precise\' request may not be supported. Try removing 'p' modifier.");
+#if defined(__i386__) || defined(__x86_64__)
+		if (evsel->attr.type == PERF_TYPE_HARDWARE)
+			return scnprintf(msg, size, "%s",
+	"No hardware sampling interrupt available.\n"
+	"No APIC? If so then you can boot the kernel with the \"lapic\" boot parameter to force-enable it.");
+#endif
+		break;
+	default:
+		break;
+	}
+
+	return scnprintf(msg, size,
+	"The sys_perf_event_open() syscall returned with %d (%s) for event (%s).  \n"
+	"/bin/dmesg may provide additional information.\n"
+	"No CONFIG_PERF_EVENTS=y kernel support configured?\n",
+			 err, strerror(err), perf_evsel__name(evsel));
+}

tools/perf/util/evsel.h

@@ -254,4 +254,7 @@ int perf_evsel__fprintf(struct perf_evsel *evsel,
 
 bool perf_evsel__fallback(struct perf_evsel *evsel, int err,
 			  char *msg, size_t msgsize);
+int perf_evsel__open_strerror(struct perf_evsel *evsel,
+			      struct perf_target *target,
+			      int err, char *msg, size_t size);
 #endif /* __PERF_EVSEL_H */