linux-kernel - [PATCH v3 4/7] perf probe: Generate event name with line number

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Date:   Mon, 18 Nov 2019 17:12:20 +0900
From:   Masami Hiramatsu <mhiramat@...nel.org>
To:     Arnaldo Carvalho de Melo <acme@...nel.org>
Cc:     Masami Hiramatsu <mhiramat@...nel.org>,
        Ingo Molnar <mingo@...hat.com>,
        Steven Rostedt <rostedt@...dmis.org>,
        linux-kernel@...r.kernel.org,
        Tom Zanussi <tom.zanussi@...ux.intel.com>,
        Ravi Bangoria <ravi.bangoria@...ux.ibm.com>,
        Namhyung Kim <namhyung@...nel.org>
Subject: [PATCH v3 4/7] 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

# perf probe -l
  probe:kernel_read    (on kernel_read@...ux-5.0.0/fs/read_write.c)
  probe:kernel_read_L2 (on kernel_read:2@...ux-5.0.0/fs/read_write.c)

Signed-off-by: Masami Hiramatsu <mhiramat@...nel.org>
---
 Changes in v3:
  - Update samples according to previous fixes.
 Changes in v2:
  - Do not add _L* suffix for the event which has no line
    number or line #0.
---
 tools/perf/util/probe-event.c |    8 ++++++++
 1 file changed, 8 insertions(+)

diff --git a/tools/perf/util/probe-event.c b/tools/perf/util/probe-event.c
index e29948b8fcab..5c86d2cf6338 100644
--- a/tools/perf/util/probe-event.c
+++ b/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);