perf probe: Generate event name with line number

Generate event name from function name with line number as
<function>_L<line_number>. Note that this is only for the new event
which is defined by the line number of function (except for line 0).

If there is another event on same line, you have to use
"-f" option. In that case, the new event has "_1" suffix.

 e.g.
  # perf probe -a kernel_read:2
  Added new event:
    probe:kernel_read_L2 (on kernel_read:2)

  You can now use it in all perf tools, such as:

  	perf record -e probe:kernel_read_L2 -aR sleep 1

But if we omit the line number or 0th line, it will
have no suffix.

  # perf probe -a kernel_read:0
  Added new event:
    probe:kernel_read (on kernel_read)

  You can now use it in all perf tools, such as:

  	perf record -e probe:kernel_read -aR sleep 1

  probe:kernel_read    (on kernel_read@linux-5.0.0/fs/read_write.c)
  probe:kernel_read_L2 (on kernel_read:2@linux-5.0.0/fs/read_write.c)
Signed-off-by: Masami Hiramatsu <mhiramat@kernel.org>
Tested-by: Arnaldo Carvalho de Melo <acme@redhat.com>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: Ravi Bangoria <ravi.bangoria@linux.ibm.com>
Cc: Steven Rostedt (VMware) <rostedt@goodmis.org>
Cc: Tom Zanussi <tom.zanussi@linux.intel.com>
Link: http://lore.kernel.org/lkml/157406474026.24476.2828897745502059569.stgit@devnote2Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>

tools/perf/util/probe-event.c

@@ -1679,6 +1679,14 @@ int parse_perf_probe_command(const char *cmd, struct perf_probe_event *pev)
 	if (ret < 0)
 		goto out;
 
+	/* Generate event name if needed */
+	if (!pev->event && pev->point.function && pev->point.line
+			&& !pev->point.lazy_line && !pev->point.offset) {
+		if (asprintf(&pev->event, "%s_L%d", pev->point.function,
+			pev->point.line) < 0)
+			return -ENOMEM;
+	}
+
 	/* Copy arguments and ensure return probe has no C argument */
 	pev->nargs = argc - 1;
 	pev->args = zalloc(sizeof(struct perf_probe_arg) * pev->nargs);