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>

3 files changed, 55 insertions, 0 deletions

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 */