tools lib traceevent: Introduce pevent_strerror

The pevent_strerror() sets @buf to a string that describes the
(libtraceevent-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.

To sync error string with its code, define PEVENT_ERRORS with _PE()
macro and use it as suggested by Steven.

Signed-off-by: Namhyung Kim <namhyung@kernel.org>
Acked-by: Steven Rostedt <rostedt@goodmis.org>
Cc: Frederic Weisbecker <fweisbec@gmail.com>
Cc: Ingo Molnar <mingo@kernel.org>
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Steven Rostedt <rostedt@goodmis.org>
Link: http://lkml.kernel.org/r/1345618831-9148-4-git-send-email-namhyung@kernel.org
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>

2 files changed, 57 insertions, 6 deletions

diff --git a/tools/lib/traceevent/event-parse.c b/tools/lib/traceevent/event-parse.c
index a46cae701db7..1373e4cf109e 100644
--- a/tools/lib/traceevent/event-parse.c
+++ b/tools/lib/traceevent/event-parse.c
@@ -4795,6 +4795,49 @@ enum pevent_errno pevent_parse_event(struct pevent *pevent, const char *buf,
         return ret;
 }
 
+#undef _PE
+#define _PE(code, str) str
+static const char * const pevent_error_str[] = {
+        PEVENT_ERRORS
+};
+#undef _PE
+
+int pevent_strerror(struct pevent *pevent, enum pevent_errno errnum,
+                    char *buf, size_t buflen)
+{
+        int idx;
+        const char *msg;
+
+        if (errnum >= 0) {
+                strerror_r(errnum, buf, buflen);
+                return 0;
+        }
+
+        if (errnum <= __PEVENT_ERRNO__START ||
+            errnum >= __PEVENT_ERRNO__END)
+                return -1;
+
+        idx = errnum - __PEVENT_ERRNO__START;
+        msg = pevent_error_str[idx];
+
+        switch (errnum) {
+        case PEVENT_ERRNO__MEM_ALLOC_FAILED:
+        case PEVENT_ERRNO__PARSE_EVENT_FAILED:
+        case PEVENT_ERRNO__READ_ID_FAILED:
+        case PEVENT_ERRNO__READ_FORMAT_FAILED:
+        case PEVENT_ERRNO__READ_PRINT_FAILED:
+        case PEVENT_ERRNO__OLD_FTRACE_ARG_FAILED:
+                snprintf(buf, buflen, "%s", msg);
+                break;
+
+        default:
+                /* cannot reach here */
+                break;
+        }
+
+        return 0;
+}
+
 int get_field_val(struct trace_seq *s, struct format_field *field,
                   const char *name, struct pevent_record *record,
                   unsigned long long *val, int err)
diff --git a/tools/lib/traceevent/event-parse.h b/tools/lib/traceevent/event-parse.h
index 3c48229a7bce..527df038a25f 100644
--- a/tools/lib/traceevent/event-parse.h
+++ b/tools/lib/traceevent/event-parse.h
@@ -345,6 +345,16 @@ enum pevent_flag {
         PEVENT_NSEC_OUTPUT              = 1,    /* output in NSECS */
 };
 
+#define PEVENT_ERRORS                                                         \
+        _PE(MEM_ALLOC_FAILED,   "failed to allocate memory"),                 \
+        _PE(PARSE_EVENT_FAILED, "failed to parse event"),                     \
+        _PE(READ_ID_FAILED,     "failed to read event id"),                   \
+        _PE(READ_FORMAT_FAILED, "failed to read event format"),               \
+        _PE(READ_PRINT_FAILED,  "failed to read event print fmt"),            \
+        _PE(OLD_FTRACE_ARG_FAILED,"failed to allocate field name for ftrace")
+
+#undef _PE
+#define _PE(__code, __str) PEVENT_ERRNO__ ## __code
 enum pevent_errno {
         PEVENT_ERRNO__SUCCESS                   = 0,
 
@@ -357,15 +367,11 @@ enum pevent_errno {
          */
         __PEVENT_ERRNO__START                   = -100000,
 
-        PEVENT_ERRNO__MEM_ALLOC_FAILED          = __PEVENT_ERRNO__START,
-        PEVENT_ERRNO__PARSE_EVENT_FAILED,
-        PEVENT_ERRNO__READ_ID_FAILED,
-        PEVENT_ERRNO__READ_FORMAT_FAILED,
-        PEVENT_ERRNO__READ_PRINT_FAILED,
-        PEVENT_ERRNO__OLD_FTRACE_ARG_FAILED,
+        PEVENT_ERRORS,
 
         __PEVENT_ERRNO__END,
 };
+#undef _PE
 
 struct cmdline;
 struct cmdline_list;
@@ -583,6 +589,8 @@ int pevent_data_pid(struct pevent *pevent, struct pevent_record *rec);
 const char *pevent_data_comm_from_pid(struct pevent *pevent, int pid);
 void pevent_event_info(struct trace_seq *s, struct event_format *event,
                        struct pevent_record *record);
+int pevent_strerror(struct pevent *pevent, enum pevent_errno errnum,
+                    char *buf, size_t buflen);
 
 struct event_format **pevent_list_events(struct pevent *pevent, enum event_sort_type);
 struct format_field **pevent_event_common_fields(struct event_format *event);