linux-kernel - [PATCH perf/core v2 5/5] perf probe: Allow weak symbols to be probed

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Date:	Fri, 06 Mar 2015 16:31:29 +0900
From:	Masami Hiramatsu <masami.hiramatsu.pt@...achi.com>
To:	Arnaldo Carvalho de Melo <acme@...nel.org>
Cc:	Naohiro Aota <naota@...sp.net>,
	Peter Zijlstra <peterz@...radead.org>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
	David Ahern <dsahern@...il.com>, namhyung@...nel.org,
	Jiri Olsa <jolsa@...hat.com>, Ingo Molnar <mingo@...nel.org>
Subject: [PATCH perf/core v2 5/5] perf probe: Allow weak symbols to be probed

From: Namhyung Kim <namhyung@...nel.org>

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: Masami Hiramatsu <masami.hiramatsu.pt@...achi.com>
Signed-off-by: Namhyung Kim <namhyung@...nel.org>
---
 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 c379ea0..f9c1e53 100644
--- a/tools/perf/util/probe-event.c
+++ b/tools/perf/util/probe-event.c
@@ -309,10 +309,8 @@ 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;
@@ -2484,8 +2482,7 @@ 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;
@@ -2845,8 +2842,7 @@ 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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