[PATCH 5/7] perf tools: Introduce perf_target__strerror()

[Namhyung Kim <namhyung.kim@lge.com>]

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.

Suggested-by: Arnaldo Carvalho de Melo <acme@ghostprotocols.net>
Reviewed-by: David Ahern <dsahern@gmail.com>
Signed-off-by: Namhyung Kim <namhyung.kim@lge.com>
---
 tools/perf/builtin-record.c |   18 +++++++++++++--
 tools/perf/builtin-top.c    |   19 +++++++++++++---
 tools/perf/util/debug.c     |    1 +
 tools/perf/util/target.c    |   51 +++++++++++++++++++++++++++++++++++++++++++
 tools/perf/util/target.h    |    3 +++
 5 files changed, 87 insertions(+), 5 deletions(-)

diff --git a/tools/perf/builtin-record.c b/tools/perf/builtin-record.c
index d26a279796d9..211d28f01eff 100644
--- a/tools/perf/builtin-record.c
+++ b/tools/perf/builtin-record.c
@@ -831,6 +831,7 @@ int cmd_record(int argc, const char **argv, const char *prefix __used)
 	struct perf_evsel *pos;
 	struct perf_evlist *evsel_list;
 	struct perf_record *rec = &record;
+	char errbuf[BUFSIZ];
 
 	perf_header__set_cmdline(argc, argv);
 
@@ -884,11 +885,24 @@ int cmd_record(int argc, const char **argv, const char *prefix __used)
 		goto out_symbol_exit;
 	}
 
-	perf_target__validate(&rec->opts.target);
+	err = perf_target__validate(&rec->opts.target);
+	if (err != PERF_ERRNO_TARGET__SUCCESS) {
+		perf_target__strerror(&rec->opts.target, err, errbuf, BUFSIZ);
+		ui__warning("%s", errbuf);
+	}
+
+	err = perf_target__parse_uid(&rec->opts.target);
+	if (err != PERF_ERRNO_TARGET__SUCCESS) {
+		int saved_errno = errno;
 
-	if (perf_target__parse_uid(&rec->opts.target) < 0)
+		perf_target__strerror(&rec->opts.target, err, errbuf, BUFSIZ);
+		ui__warning("%s", errbuf);
+
+		err = -saved_errno;
 		goto out_free_fd;
+	}
 
+	err = -ENOMEM;
 	if (perf_evlist__create_maps(evsel_list, &rec->opts.target) < 0)
 		usage_with_options(record_usage, record_options);
 
diff --git a/tools/perf/builtin-top.c b/tools/perf/builtin-top.c
index 59883c8c5817..a2518fc0626a 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 = {
 		.target		     = {
 			.system_wide = true,
@@ -1255,10 +1256,22 @@ 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_ERRNO_TARGET__SUCCESS) {
+		perf_target__strerror(&top.target, status, errbuf, BUFSIZ);
+		ui__warning("%s", errbuf);
+	}
+
+	status = perf_target__parse_uid(&top.target);
+	if (status != PERF_ERRNO_TARGET__SUCCESS) {
+		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 (perf_evlist__create_maps(top.evlist, &top.target) < 0)
 		usage_with_options(top_usage, options);
diff --git a/tools/perf/util/debug.c b/tools/perf/util/debug.c
index 26817daa2961..efb1fce259a4 100644
--- a/tools/perf/util/debug.c
+++ b/tools/perf/util/debug.c
@@ -11,6 +11,7 @@
 #include "event.h"
 #include "debug.h"
 #include "util.h"
+#include "target.h"
 
 int verbose;
 bool dump_trace = false, quiet = false;
diff --git a/tools/perf/util/target.c b/tools/perf/util/target.c
index 02a6bedb69a3..1064d5b148ad 100644
--- a/tools/perf/util/target.c
+++ b/tools/perf/util/target.c
@@ -10,6 +10,7 @@
 #include "debug.h"
 
 #include <pwd.h>
+#include <string.h>
 
 
 enum perf_target_errno perf_target__validate(struct perf_target *target)
@@ -89,3 +90,53 @@ enum perf_target_errno perf_target__parse_uid(struct perf_target *target)
 	target->uid = result->pw_uid;
 	return PERF_ERRNO_TARGET__SUCCESS;
 }
+
+/*
+ * This must have a same ordering as the enum perf_target_errno.
+ */
+static const char *perf_target__error_str[] = {
+	"PID/TID switch overriding CPU",
+	"PID/TID switch overriding UID",
+	"UID switch overriding CPU",
+	"PID/TID switch overriding SYSTEM",
+	"UID switch overriding SYSTEM",
+	"Invalid User: %s",
+	"Problems obtaining information for user %s",
+};
+
+int perf_target__strerror(struct perf_target *target, int errnum,
+			  char *buf, size_t buflen)
+{
+	int idx;
+	const char *msg;
+
+	if (errnum >= 0) {
+		strerror_r(errnum, buf, buflen);
+		return 0;
+	}
+
+	if (errnum <  __PERF_ERRNO_TARGET__START ||
+	    errnum >= __PERF_ERRNO_TARGET__END)
+		return -1;
+
+	idx = errnum - __PERF_ERRNO_TARGET__START;
+	msg = perf_target__error_str[idx];
+
+	switch (errnum) {
+	case PERF_ERRNO_TARGET__PID_OVERRIDE_CPU
+	 ... PERF_ERRNO_TARGET__UID_OVERRIDE_SYSTEM:
+		snprintf(buf, buflen, "%s", msg);
+		break;
+
+	case PERF_ERRNO_TARGET__INVALID_UID:
+	case PERF_ERRNO_TARGET__USER_NOT_FOUND:
+		snprintf(buf, buflen, msg, target->uid_str);
+		break;
+
+	default:
+		/* cannot reach here */
+		break;
+	}
+
+	return 0;
+}
diff --git a/tools/perf/util/target.h b/tools/perf/util/target.h
index d4aabdaba42a..6fcd01c440a9 100644
--- a/tools/perf/util/target.h
+++ b/tools/perf/util/target.h
@@ -43,4 +43,7 @@ enum perf_target_errno {
 enum perf_target_errno perf_target__validate(struct perf_target *target);
 enum perf_target_errno perf_target__parse_uid(struct perf_target *target);
 
+int perf_target__strerror(struct perf_target *target, int errnum, char *buf,
+			  size_t buflen);
+
 #endif /* _PERF_TARGET_H */
-- 
1.7.10.1