Re: [PATCH 4/4] perf-probe: Warn if the target function is GNU Indirect function

[Srikar Dronamraju]

* Masami Hiramatsu <mhiramat@xxxxxxxxxx> [2020-07-09 17:07:31]:

> Reported-by: Andi Kleen <andi@xxxxxxxxxxxxxx>
> Signed-off-by: Masami Hiramatsu <mhiramat@xxxxxxxxxx>
> ---
>  tools/perf/util/probe-event.c |    5 +++++
>  1 file changed, 5 insertions(+)
> 
> diff --git a/tools/perf/util/probe-event.c b/tools/perf/util/probe-event.c
> index 1e95a336862c..671176d39569 100644
> --- a/tools/perf/util/probe-event.c
> +++ b/tools/perf/util/probe-event.c
> @@ -379,6 +379,11 @@ static int find_alternative_probe_point(struct debuginfo *dinfo,
>  			address = sym->start;
>  		else
>  			address = map->unmap_ip(map, sym->start) - map->reloc;
> +		if (sym->type == STT_GNU_IFUNC) {
> +			pr_warning("Warning: The probe address (0x%lx) is in a GNU indirect function.\n"
> +				"This may not work as you expected unless you intend to probe the indirect function.\n",
> +				(unsigned long)address);
> +		}

Are these GNU indirect functions possible in kernel? If not we could move
this warning under if (uprobes)

Also instead of printing the address, can we print the pp->function?

>  		break;
>  	}
>  	if (!address) {
> 

-- 
Thanks and Regards
Srikar Dronamraju