perf symbols: Handle NULL dso in dso__name_len

We should use "[unknown]" in this case, in concert with the code in
_hist_entry__dso_snprintf().

Otherwise we'll crash when recomputing the histogram column lengths in
hists__calc_col_len().

Signed-off-by: David S. Miller <davem@davemloft.net>
Link: http://lkml.kernel.org/r/20120325.162822.2267799792062571623.davem@davemloft.net
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>

1 files changed, 2 insertions, 0 deletions

diff --git a/tools/perf/util/symbol.c b/tools/perf/util/symbol.c
index d9e995bf8b6f..c0a028c3ebaf 100644
--- a/tools/perf/util/symbol.c
+++ b/tools/perf/util/symbol.c
@@ -50,6 +50,8 @@ struct symbol_conf symbol_conf = {
 
 int dso__name_len(const struct dso *dso)
 {
+        if (!dso)
+                return strlen("[unknown]");
         if (verbose)
                 return dso->long_name_len;