linux-kernel - [PATCH 23/27] perf probe: Ignore the error of finding inline instance

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Date:   Thu, 29 Sep 2016 11:35:52 -0300
From:   Arnaldo Carvalho de Melo <acme@...nel.org>
To:     Ingo Molnar <mingo@...nel.org>
Cc:     linux-kernel@...r.kernel.org, Linux Weekly News <lwn@....net>,
        Masami Hiramatsu <mhiramat@...nel.org>,
        David Ahern <dsahern@...il.com>,
        Namhyung Kim <namhyung@...nel.org>,
        Peter Zijlstra <peterz@...radead.org>,
        Thomas Gleixner <tglx@...utronix.de>,
        Arnaldo Carvalho de Melo <acme@...hat.com>
Subject: [PATCH 23/27] perf probe: Ignore the error of finding inline instance

From: Masami Hiramatsu <mhiramat@...nel.org>

Ignore the error when the perf probe failed to find inline function
instances. This can happen when we search a method in C++ debuginfo.  If
there is completely no instance in target, perf probe can return an
error.

E.g. without this fix:
  ----
  $ perf probe -x /usr/lib64/libstdc++.so.6 -vD showmanyc
  probe-definition(0): showmanyc
  symbol:showmanyc file:(null) line:0 offset:0 return:0 lazy:(null)
  0 arguments
  symbol:catch file:(null) line:0 offset:0 return:0 lazy:(null)
  symbol:throw file:(null) line:0 offset:0 return:0 lazy:(null)
  symbol:rethrow file:(null) line:0 offset:0 return:0 lazy:(null)
  Open Debuginfo file: /usr/lib/debug/usr/lib64/libstdc++.so.6.0.22.debug
  Try to find probe point from debuginfo.
  Matched function: showmanyc
  An error occurred in debuginfo analysis (-2).
  Trying to use symbols.
  Failed to find symbol showmanyc in /usr/lib64/libstdc++.so.6.0.22
    Error: Failed to add events. Reason: No such file or directory (Code: -2)
  ----

This is because one of showmanyc is defined as inline but no instance
found. With this fix, it is succeeded to show as below.
  ----
  $ perf probe -x /usr/lib64/libstdc++.so.6 -D showmanyc
  p:probe_libstdc++/showmanyc /usr/lib64/libstdc++.so.6.0.22:0xb0e50
  p:probe_libstdc++/showmanyc_1 /usr/lib64/libstdc++.so.6.0.22:0xc7c40
  p:probe_libstdc++/showmanyc_2 /usr/lib64/libstdc++.so.6.0.22:0xecfa0
  p:probe_libstdc++/showmanyc_3 /usr/lib64/libstdc++.so.6.0.22:0x115fc0
  p:probe_libstdc++/showmanyc_4 /usr/lib64/libstdc++.so.6.0.22:0x121a90
  ----

Signed-off-by: Masami Hiramatsu <mhiramat@...nel.org>
Tested-by: Arnaldo Carvalho de Melo <acme@...hat.com>
Tested-by: Jiri Olsa <jolsa@...nel.org>
Cc: David Ahern <dsahern@...il.com>
Cc: Namhyung Kim <namhyung@...nel.org>
Cc: Peter Zijlstra <peterz@...radead.org>
Cc: Thomas Gleixner <tglx@...utronix.de>
Link: http://lkml.kernel.org/r/147464489775.29804.3190419491209875936.stgit@devbox
Signed-off-by: Arnaldo Carvalho de Melo <acme@...hat.com>
---
 tools/perf/util/probe-finder.c | 5 +++--
 1 file changed, 3 insertions(+), 2 deletions(-)

diff --git a/tools/perf/util/probe-finder.c b/tools/perf/util/probe-finder.c
index 8daca4fc1f8d..5fe8325e81f2 100644
--- a/tools/perf/util/probe-finder.c
+++ b/tools/perf/util/probe-finder.c
@@ -988,7 +988,8 @@ static int probe_point_search_cb(Dwarf_Die *sp_die, void *data)
 	if (pp->file && strtailcmp(pp->file, dwarf_decl_file(sp_die)))
 		return DWARF_CB_OK;
 
-	pr_debug("Matched function: %s\n", dwarf_diename(sp_die));
+	pr_debug("Matched function: %s [%lx]\n", dwarf_diename(sp_die),
+		 (unsigned long)dwarf_dieoffset(sp_die));
 	pf->fname = dwarf_decl_file(sp_die);
 	if (pp->line) { /* Function relative line */
 		dwarf_decl_line(sp_die, &pf->lno);
@@ -1011,7 +1012,7 @@ static int probe_point_search_cb(Dwarf_Die *sp_die, void *data)
 		param->retval = die_walk_instances(sp_die,
 					probe_point_inline_cb, (void *)pf);
 		/* This could be a non-existed inline definition */
-		if (param->retval == -ENOENT && strisglob(pp->function))
+		if (param->retval == -ENOENT)
 			param->retval = 0;
 	}
 
-- 
2.7.4