linux-kernel - [PATCH 1/4] perf annotate browser: Handle NULL jump targets

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Date:	Thu, 26 Apr 2012 12:06:14 -0300
From:	Arnaldo Carvalho de Melo <acme@...radead.org>
To:	Ingo Molnar <mingo@...nel.org>
Cc:	linux-kernel@...r.kernel.org,
	Arnaldo Carvalho de Melo <acme@...hat.com>,
	David Ahern <dsahern@...il.com>,
	Frederic Weisbecker <fweisbec@...il.com>,
	Mike Galbraith <efault@....de>,
	Namhyung Kim <namhyung@...il.com>,
	Paul Mackerras <paulus@...ba.org>,
	Peter Zijlstra <peterz@...radead.org>,
	Stephane Eranian <eranian@...gle.com>
Subject: [PATCH 1/4] perf annotate browser: Handle NULL jump targets

From: Arnaldo Carvalho de Melo <acme@...hat.com>

In annotate_browser__mark_jump_targets

702                     dlt = browser->offsets[dl->ops.target];
703                     bdlt = disasm_line__browser(dlt);
704                     bdlt->jump_target = true;
705             }
706
707     }

(gdb) p size
$5 = 2415
(gdb) p offset
$6 = 140
(gdb) p dl->ops.target
$7 = 143
(gdb) p browser->offsets[143]
$8 = (struct disasm_line *) 0x0
(gdb) p dl->name
$9 = 0x2363bd0 "je"
(gdb)

Really strange, the code assumed that at the jump target we would have
an assembly line, but only in the previous instruction offset we have a
'lock':

(gdb) p browser->offsets[144]
$10 = (struct disasm_line *) 0x0
(gdb) p browser->offsets[142]
$11 = (struct disasm_line *) 0x27bd620
(gdb) p browser->offsets[142]->name
$12 = 0x237a8a0 "lock"
(gdb)

I'll study this more, but for now I'll just check if there is a
disasm_line at dl->ops.target, i.e. a valid jump target.

Reported-by: Hagen Paul Pfeifer <hagen@...u.net>
Reported-by: Ingo Molnar <mingo@...nel.org>
Cc: David Ahern <dsahern@...il.com>
Cc: Frederic Weisbecker <fweisbec@...il.com>
Cc: Mike Galbraith <efault@....de>
Cc: Namhyung Kim <namhyung@...il.com>
Cc: Paul Mackerras <paulus@...ba.org>
Cc: Peter Zijlstra <peterz@...radead.org>
Cc: Stephane Eranian <eranian@...gle.com>
Link: http://lkml.kernel.org/n/tip-inzjrzyqhkzyv78met2vula6@git.kernel.org
Signed-off-by: Arnaldo Carvalho de Melo <acme@...hat.com>
---
 tools/perf/ui/browsers/annotate.c |    7 +++++++
 1 file changed, 7 insertions(+)

diff --git a/tools/perf/ui/browsers/annotate.c b/tools/perf/ui/browsers/annotate.c
index 9e3310c..4c83fe3 100644
--- a/tools/perf/ui/browsers/annotate.c
+++ b/tools/perf/ui/browsers/annotate.c
@@ -700,6 +700,13 @@ static void annotate_browser__mark_jump_targets(struct annotate_browser *browser
 		}
 
 		dlt = browser->offsets[dl->ops.target];
+		/*
+ 		 * FIXME: Oops, no jump target? Buggy disassembler? Or do we
+ 		 * have to adjust to the previous offset?
+ 		 */
+		if (dlt == NULL)
+			continue;
+
 		bdlt = disasm_line__browser(dlt);
 		bdlt->jump_target = true;
 	}
-- 
1.7.9.2.358.g22243

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