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

Jin, Yao
2020-03-23T13:59:20Z

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.

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