linux-kernel - Re: [PATCH v2 1/2] perf: Suggest inbuilt commands for unknown command

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Date: Wed, 20 Mar 2024 08:25:54 -0700
From: Ian Rogers <irogers@...gle.com>
To: Arnaldo Carvalho de Melo <acme@...nel.org>
Cc: Peter Zijlstra <peterz@...radead.org>, Ingo Molnar <mingo@...hat.com>, 
	Namhyung Kim <namhyung@...nel.org>, Mark Rutland <mark.rutland@....com>, 
	Alexander Shishkin <alexander.shishkin@...ux.intel.com>, Jiri Olsa <jolsa@...nel.org>, 
	Adrian Hunter <adrian.hunter@...el.com>, linux-perf-users@...r.kernel.org, 
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2 1/2] perf: Suggest inbuilt commands for unknown command

On Wed, Mar 20, 2024 at 8:20 AM Arnaldo Carvalho de Melo
<acme@...nel.org> wrote:
>
> On Wed, Mar 20, 2024 at 08:12:56AM -0700, Ian Rogers wrote:
> > Ah, the change:
> >
> > -               static int done_help;
> > +               int done_help;
> >
> > created an uninitialized use. Compiler warning/sanitizers? Anyway,
> > done_help needs hoisting out of the loop and initializing to zero, or
> > being made static again (ugh).
>
> ⬢[acme@...lbox perf-tools-next]$ git diff
> diff --git a/tools/perf/perf.c b/tools/perf/perf.c
> index c719e6ccd9e27778..f9532b20e87cbf05 100644
> --- a/tools/perf/perf.c
> +++ b/tools/perf/perf.c
> @@ -459,7 +459,7 @@ static int libperf_print(enum libperf_print_level level,
>
>  int main(int argc, const char **argv)
>  {
> -       int err;
> +       int err, done_help = 0;
>         const char *cmd;
>         char sbuf[STRERR_BUFSIZE];
>
> @@ -558,8 +558,6 @@ int main(int argc, const char **argv)
>         pthread__block_sigwinch();
>
>         while (1) {
> -               int done_help;
> -
>                 run_argv(&argc, &argv);
>
>                 if (errno != ENOENT)
> ⬢[acme@...lbox perf-tools-next]$ perf raccord
>   Fatal: Out of memory, realloc failed
> ⬢[acme@...lbox perf-tools-next]$
>
> Then:
>
> diff --git a/tools/perf/perf.c b/tools/perf/perf.c
> index c719e6ccd9e27778..54f62aa6612bc290 100644
> --- a/tools/perf/perf.c
> +++ b/tools/perf/perf.c
> @@ -558,7 +558,7 @@ int main(int argc, const char **argv)
>         pthread__block_sigwinch();
>
>         while (1) {
> -               int done_help;
> +               static int done_help;
>
>                 run_argv(&argc, &argv);
>
> ⬢[acme@...lbox perf-tools-next]$ perf raccord
>   Fatal: Out of memory, realloc failed
> ⬢[acme@...lbox perf-tools-next]$


Similar issue on main_cmds, caught by memory sanitizer. I think the
following fixes it:

```
diff --git a/tools/perf/perf.c b/tools/perf/perf.c
index c719e6ccd9e2..bd3f80b5bb46 100644
--- a/tools/perf/perf.c
+++ b/tools/perf/perf.c
@@ -459,7 +459,7 @@ static int libperf_print(enum libperf_print_level level,

int main(int argc, const char **argv)
{
-       int err;
+       int err, done_help = 0;
       const char *cmd;
       char sbuf[STRERR_BUFSIZE];

@@ -558,15 +558,13 @@ int main(int argc, const char **argv)
       pthread__block_sigwinch();

       while (1) {
-               int done_help;
-
               run_argv(&argc, &argv);

               if (errno != ENOENT)
                       break;

               if (!done_help) {
-                       struct cmdnames main_cmds;
+                       struct cmdnames main_cmds = {};

                       for (unsigned int i = 0; i < ARRAY_SIZE(commands); i++) {
                               add_cmdname(&main_cmds,
```

Thanks,
Ian

> - Arnaldo