[PATCH 09/11] perf report: Don't crash on invalid inline debug information

From: Arnaldo Carvalho de Melo
Date: Wed Oct 17 2018 - 18:55:54 EST

From: Milian Wolff <milian.wolff@xxxxxxxx>

When the function name for an inline frame is invalid, we must not try
to demangle this symbol, otherwise we crash with:

#0 0x0000555555895c01 in bfd_demangle ()
#1 0x0000555555823262 in demangle_sym (dso=0x555555d92b90, elf_name=0x0, kmodule=0) at util/symbol-elf.c:215
#2 dso__demangle_sym (dso=dso@entry=0x555555d92b90, kmodule=<optimized out>, kmodule@entry=0, elf_name=elf_name@entry=0x0) at util/symbol-elf.c:400
#3 0x00005555557fef4b in new_inline_sym (funcname=0x0, base_sym=0x555555d92b90, dso=0x555555d92b90) at util/srcline.c:89
#4 inline_list__append_dso_a2l (dso=dso@entry=0x555555c7bb00, node=node@entry=0x555555e31810, sym=sym@entry=0x555555d92b90) at util/srcline.c:264
#5 0x00005555557ff27f in addr2line (dso_name=dso_name@entry=0x555555d92430 "/home/milian/.debug/.build-id/f7/186d14bb94f3c6161c010926da66033d24fce5/elf", addr=addr@entry=2888, file=file@entry=0x0,
line=line@entry=0x0, dso=dso@entry=0x555555c7bb00, unwind_inlines=unwind_inlines@entry=true, node=0x555555e31810, sym=0x555555d92b90) at util/srcline.c:313
#6 0x00005555557ffe7c in addr2inlines (sym=0x555555d92b90, dso=0x555555c7bb00, addr=2888, dso_name=0x555555d92430 "/home/milian/.debug/.build-id/f7/186d14bb94f3c6161c010926da66033d24fce5/elf")
at util/srcline.c:358

So instead handle the case where we get invalid function names for
inlined frames and use a fallback '??' function name instead.

While this crash was originally reported by Hadrien for rust code, I can
now also reproduce it with trivial C++ code. Indeed, it seems like
libbfd fails to interpret the debug information for the inline frame
symbol name:

$ addr2line -e /home/milian/.debug/.build-id/f7/186d14bb94f3c6161c010926da66033d24fce5/elf -if b48

I've reported this bug upstream and also attached a patch there which
should fix this issue:


Reported-by: Hadrien Grasland <grasland@xxxxxxxxxxxx>
Signed-off-by: Milian Wolff <milian.wolff@xxxxxxxx>
Cc: Jin Yao <yao.jin@xxxxxxxxxxxxxxx>
Cc: Jiri Olsa <jolsa@xxxxxxxxxx>
Cc: Namhyung Kim <namhyung@xxxxxxxxxx>
Fixes: a64489c56c30 ("perf report: Find the inline stack for a given address")
[ The above 'Fixes:' cset is where originally the problem was
introduced, i.e. using a2l->funcname without checking if it is NULL,
but this current patch fixes the current codebase, i.e. multiple csets
were applied after a64489c56c30 before the problem was reported by Hadrien ]
Link: http://lkml.kernel.org/r/20180926135207.30263-3-milian.wolff@xxxxxxxx
Signed-off-by: Arnaldo Carvalho de Melo <acme@xxxxxxxxxx>
tools/perf/util/srcline.c | 3 +++
1 file changed, 3 insertions(+)

diff --git a/tools/perf/util/srcline.c b/tools/perf/util/srcline.c
index 09d6746e6ec8..e767c4a9d4d2 100644
--- a/tools/perf/util/srcline.c
+++ b/tools/perf/util/srcline.c
@@ -85,6 +85,9 @@ static struct symbol *new_inline_sym(struct dso *dso,
struct symbol *inline_sym;
char *demangled = NULL;

+ if (!funcname)
+ funcname = "??";
if (dso) {
demangled = dso__demangle_sym(dso, 0, funcname);
if (demangled)