perf tools: Introduce perf_target__strerror()

The perf_target__strerror() sets @buf to a string that describes the
(perf_target-specific) error condition that is passed via @errnum.

This is similar to strerror_r() and does same thing if @errnum has a
standard errno value.

Signed-off-by: Namhyung Kim <namhyung.kim@lge.com>
Suggested-by: Arnaldo Carvalho de Melo <acme@ghostprotocols.net>
Reviewed-by: David Ahern <dsahern@gmail.com>
Cc: David Ahern <dsahern@gmail.com>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: Namhyung Kim <namhyung@gmail.com>
Cc: Paul Mackerras <paulus@samba.org>
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
Link: http://lkml.kernel.org/r/1336367344-28071-6-git-send-email-namhyung.kim@lge.com
[ committer note: No need to use PERF_ERRNO_TARGET__SUCCESS, use shorter idiom ]
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>

1 files changed, 16 insertions, 3 deletions

diff --git a/tools/perf/builtin-top.c b/tools/perf/builtin-top.c
index c9137ba580d..7ba0f03c013 100644
--- a/tools/perf/builtin-top.c
+++ b/tools/perf/builtin-top.c
@@ -1150,7 +1150,8 @@ static const char * const top_usage[] = {
 int cmd_top(int argc, const char **argv, const char *prefix __used)
 {
         struct perf_evsel *pos;
-        int status = -ENOMEM;
+        int status;
+        char errbuf[BUFSIZ];
         struct perf_top top = {
                 .count_filter        = 5,
                 .delay_secs          = 2,
@@ -1252,10 +1253,22 @@ int cmd_top(int argc, const char **argv, const char *prefix __used)
 
         setup_browser(false);
 
-        perf_target__validate(&top.target);
+        status = perf_target__validate(&top.target);
+        if (status) {
+                perf_target__strerror(&top.target, status, errbuf, BUFSIZ);
+                ui__warning("%s", errbuf);
+        }
+
+        status = perf_target__parse_uid(&top.target);
+        if (status) {
+                int saved_errno = errno;
 
-        if (perf_target__parse_uid(&top.target) < 0)
+                perf_target__strerror(&top.target, status, errbuf, BUFSIZ);
+                ui__warning("%s", errbuf);
+
+                status = -saved_errno;
                 goto out_delete_evlist;
+        }
 
         if (top.target.tid == 0 && top.target.pid == 0 &&
             top.target.uid_str == NULL)