Re: [PATCH v2 00/14] perf: Stream comparison

[Jiri Olsa <jolsa@redhat.com>]

On Mon, Mar 23, 2020 at 09:59:13PM +0800, Jin, Yao wrote:
> Hi Jiri,
> 
> On 3/23/2020 7:05 PM, Jiri Olsa wrote:
> > On Fri, Mar 13, 2020 at 03:11:04PM +0800, Jin Yao wrote:
> > > Sometimes, a small change in a hot function reducing the cycles of
> > > this function, but the overall workload doesn't get faster. It is
> > > interesting where the cycles are moved to.
> > 
> > I'm getting compilation fail:
> > 
> > 	  BUILD:   Doing 'make -j1' parallel build
> > 	  CC       util/srclist.o
> > 	util/srclist.c: In function ‘srclist__node_new’:
> > 	util/srclist.c:388:35: error: ‘%s’ directive output may be truncated writing up to 4095 bytes into a region of size 4091 [-Werror=format-truncation=]
> > 	  388 |  snprintf(cmd, sizeof(cmd), "diff %s %s",
> > 	      |                                   ^~
> > 	......
> > 	  456 |  ret = init_src_info(b_path, a_path, rel_path, &node->info);
> > 	      |                      ~~~~~~
> > 	In file included from /usr/include/stdio.h:867,
> > 			 from util/srclist.c:8:
> > 	/usr/include/bits/stdio2.h:67:10: note: ‘__builtin___snprintf_chk’ output between 7 and 8197 bytes into a destination of size 4096
> > 	   67 |   return __builtin___snprintf_chk (__s, __n, __USE_FORTIFY_LEVEL - 1,
> > 	      |          ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
> > 	   68 |        __bos (__s), __fmt, __va_arg_pack ());
> > 	      |        ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
> > 	cc1: all warnings being treated as errors
> > 	mv: cannot stat 'util/.srclist.o.tmp': No such file or directory
> > 	make[4]: *** [/home/jolsa/kernel/linux-perf/tools/build/Makefile.build:97: util/srclist.o] Error 1
> > 	make[3]: *** [/home/jolsa/kernel/linux-perf/tools/build/Makefile.build:139: util] Error 2
> > 	make[2]: *** [Makefile.perf:617: perf-in.o] Error 2
> > 	make[1]: *** [Makefile.perf:225: sub-make] Error 2
> > 	make: *** [Makefile:70: all] Error 2
> > 
> > 
> > [jolsa@krava ~]$ gcc --version
> > gcc (GCC) 9.3.1 20200317 (Red Hat 9.3.1-1)
> > 
> > jirka
> > 
> 
> Can you help to add following patch on top of the patch-set? Looks we need
> to check the return value of snprintf for truncation checking.

yep, that helped.. I'll apply it on top for now
and try to do the review soon ;-)

thanks,
jirka

> 
> jinyao@kbl:~/kbl-ws/perf-dev/lck-7589/acme/tools/perf$ git diff
> diff --git a/tools/perf/util/srclist.c b/tools/perf/util/srclist.c
> index 8060e4855d11..51ca69eaa9fd 100644
> --- a/tools/perf/util/srclist.c
> +++ b/tools/perf/util/srclist.c
> @@ -385,8 +385,12 @@ static int src_info__create_line_mapping(struct
> src_info *info, char *b_path,
>                 goto out;
>         }
> 
> -       snprintf(cmd, sizeof(cmd), "diff %s %s",
> -                b_path, a_path);
> +       ret = snprintf(cmd, PATH_MAX, "diff %s %s",
> +                      b_path, a_path);
> +       if (ret == PATH_MAX) {
> +               ret = -1;
> +               goto out;
> +       }
> 
>         pr_debug("Execute '%s'\n", cmd);
> 
> Thanks
> Jin Yao
>