Re: [PATCH] perf probe: Show correct error about @symbol for uprobe

[Arnaldo Carvalho de Melo <acme@kernel.org>]

Em Fri, Jul 28, 2023 at 11:19:30PM +0900, Masami Hiramatsu (Google) escreveu:
> From: Masami Hiramatsu (Google) <mhiramat@kernel.org>
> 
> Since @symbol variable access is not supported by uprobe event, it must be
> correctly warn user instead of kernel version update.

Thanks, less cryptic now, applied.

But is that just a matter of writing code to support reading global
variables from an uprobe?

- Arnaldo

 
> Reported-by: Arnaldo Carvalho de Melo <acme@kernel.org>
> Closes: https://lore.kernel.org/all/ZLWDEjvFjrrEJODp@kernel.org/
> Signed-off-by: Masami Hiramatsu (Google) <mhiramat@kernel.org>
> ---
>  tools/perf/util/probe-event.c |   13 +++++++++----
>  1 file changed, 9 insertions(+), 4 deletions(-)
> 
> diff --git a/tools/perf/util/probe-event.c b/tools/perf/util/probe-event.c
> index 6e2110d605fb..c1ded85fe859 100644
> --- a/tools/perf/util/probe-event.c
> +++ b/tools/perf/util/probe-event.c
> @@ -2800,13 +2800,18 @@ static void warn_uprobe_event_compat(struct probe_trace_event *tev)
>  	if (!tev->uprobes || tev->nargs == 0 || !buf)
>  		goto out;
>  
> -	for (i = 0; i < tev->nargs; i++)
> -		if (strglobmatch(tev->args[i].value, "[$@+-]*")) {
> -			pr_warning("Please upgrade your kernel to at least "
> -				   "3.14 to have access to feature %s\n",
> +	for (i = 0; i < tev->nargs; i++) {
> +		if (strchr(tev->args[i].value, '@')) {
> +			pr_warning("%s accesses a variable by symbol name, but that is not supported for user application probe.\n",
> +				   tev->args[i].value);
> +			break;
> +		}
> +		if (strglobmatch(tev->args[i].value, "[$+-]*")) {
> +			pr_warning("Please upgrade your kernel to at least 3.14 to have access to feature %s\n",
>  				   tev->args[i].value);
>  			break;
>  		}
> +	}
>  out:
>  	free(buf);
>  }
> 

-- 

- Arnaldo