linux-kernel - [tip:perf/core] perf probe: Allow weak symbols to be probed

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Message-ID: <tip-e578da3b2009da2a9ae2d25fd0f78c7b76ca5e56@git.kernel.org>
Date:	Sat, 14 Mar 2015 00:03:41 -0700
From:	tip-bot for Namhyung Kim <tipbot@...or.com>
To:	linux-tip-commits@...r.kernel.org
Cc:	linux-kernel@...r.kernel.org, namhyung@...nel.org, hpa@...or.com,
	naota@...sp.net, acme@...hat.com, tglx@...utronix.de,
	mingo@...nel.org, peterz@...radead.org,
	masami.hiramatsu.pt@...achi.com, dsahern@...il.com,
	jolsa@...hat.com
Subject: [tip:perf/core] perf probe: Allow weak symbols to be probed

Commit-ID:  e578da3b2009da2a9ae2d25fd0f78c7b76ca5e56
Gitweb:     http://git.kernel.org/tip/e578da3b2009da2a9ae2d25fd0f78c7b76ca5e56
Author:     Namhyung Kim <namhyung@...nel.org>
AuthorDate: Fri, 6 Mar 2015 16:31:29 +0900
Committer:  Arnaldo Carvalho de Melo <acme@...hat.com>
CommitDate: Thu, 12 Mar 2015 12:39:55 -0300

perf probe: Allow weak symbols to be probed

It currently prevents adding probes in weak symbols.  But there're cases
that given name is an only weak symbol so that we cannot add probe.

  $ perf probe -x /usr/lib/libc.so.6 -a calloc
  Failed to find symbol calloc in /usr/lib/libc-2.21.so
    Error: Failed to add events.

  $ nm /usr/lib/libc.so.6 | grep calloc
  000000000007b1f0 t __calloc
  000000000007b1f0 T __libc_calloc
  000000000007b1f0 W calloc

This change will result in duplicate probes when strong and weak symbols
co-exist in a binary.  But I think it's not a big problem since probes
at the weak symbol will never be hit anyway.

Signed-off-by: Namhyung Kim <namhyung@...nel.org>
Tested-by: Arnaldo Carvalho de Melo <acme@...hat.com>
Cc: David Ahern <dsahern@...il.com>
Cc: Jiri Olsa <jolsa@...hat.com>
Cc: Naohiro Aota <naota@...sp.net>
Cc: Peter Zijlstra <peterz@...radead.org>
Link: http://lkml.kernel.org/r/20150306073129.6904.41078.stgit@localhost.localdomain
Signed-off-by: Masami Hiramatsu <masami.hiramatsu.pt@...achi.com>
Signed-off-by: Arnaldo Carvalho de Melo <acme@...hat.com>
---
 tools/perf/util/probe-event.c | 12 ++++--------
 1 file changed, 4 insertions(+), 8 deletions(-)

diff --git a/tools/perf/util/probe-event.c b/tools/perf/util/probe-event.c
index 9feba0e..8af8e7f 100644
--- a/tools/perf/util/probe-event.c
+++ b/tools/perf/util/probe-event.c
@@ -310,10 +310,8 @@ static int find_alternative_probe_point(struct debuginfo *dinfo,
 
 	/* Find the address of given function */
 	map__for_each_symbol_by_name(map, pp->function, sym) {
-		if (sym->binding == STB_GLOBAL || sym->binding == STB_LOCAL) {
-			address = sym->start;
-			break;
-		}
+		address = sym->start;
+		break;
 	}
 	if (!address) {
 		ret = -ENOENT;
@@ -2485,8 +2483,7 @@ static int find_probe_functions(struct map *map, char *name)
 	struct symbol *sym;
 
 	map__for_each_symbol_by_name(map, name, sym) {
-		if (sym->binding == STB_GLOBAL || sym->binding == STB_LOCAL)
-			found++;
+		found++;
 	}
 
 	return found;
@@ -2846,8 +2843,7 @@ static struct strfilter *available_func_filter;
 static int filter_available_functions(struct map *map __maybe_unused,
 				      struct symbol *sym)
 {
-	if ((sym->binding == STB_GLOBAL || sym->binding == STB_LOCAL) &&
-	    strfilter__compare(available_func_filter, sym->name))
+	if (strfilter__compare(available_func_filter, sym->name))
 		return 0;
 	return 1;
 }
--
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