linux-kernel - [PATCH] Prevent infinite loop if unwind fails

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Date:	Fri, 22 Nov 2013 16:19:16 -0500
From:	Francis Giraldeau <francis.giraldeau@...il.com>
To:	linux-kernel@...r.kernel.org
Cc:	Francis Giraldeau <francis.giraldeau@...il.com>
Subject: [PATCH] Prevent infinite loop if unwind fails

Unwind may loop forever if sample is incomplete or bogus. Bound the number of
unw_step() that yield the same IP to prevent infinite loop.

Signed-off-by: Francis Giraldeau <francis.giraldeau@...il.com>
---
 tools/perf/util/unwind.c | 8 +++++++-
 1 file changed, 7 insertions(+), 1 deletion(-)

diff --git a/tools/perf/util/unwind.c b/tools/perf/util/unwind.c
index 958723b..bf45b6b 100644
--- a/tools/perf/util/unwind.c
+++ b/tools/perf/util/unwind.c
@@ -520,7 +520,8 @@ static int get_entries(struct unwind_info *ui, unwind_entry_cb_t cb,
 {
 	unw_addr_space_t addr_space;
 	unw_cursor_t c;
-	int ret;
+	unw_word_t prev_ip = 0;
+	int ret, rec = 0;
 
 	addr_space = unw_create_addr_space(&accessors, 0);
 	if (!addr_space) {
@@ -537,6 +538,11 @@ static int get_entries(struct unwind_info *ui, unwind_entry_cb_t cb,
 
 		unw_get_reg(&c, UNW_REG_IP, &ip);
 		ret = entry(ip, ui->thread, ui->machine, cb, arg);
+		if (prev_ip != ip)
+			rec = 0;
+		if (++rec >= 100)
+			break;
+		prev_ip = ip;
 	}
 
 	unw_destroy_addr_space(addr_space);
-- 
1.8.1.2

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