perf annotate browser: Handle NULL jump targets

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 <[email protected]>
Reported-by: Ingo Molnar <[email protected]>
Cc: David Ahern <[email protected]>
Cc: Frederic Weisbecker <[email protected]>
Cc: Mike Galbraith <[email protected]>
Cc: Namhyung Kim <[email protected]>
Cc: Paul Mackerras <[email protected]>
Cc: Peter Zijlstra <[email protected]>
Cc: Stephane Eranian <[email protected]>
Link: http://lkml.kernel.org/n/[email protected]
Signed-off-by: Arnaldo Carvalho de Melo <[email protected]>

Author: acmel

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;
 	}