linux-kernel - Re: [PATCH] perf probe: Improve error message when function not found

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Date:	Thu, 26 Dec 2013 08:43:49 -0500
From:	David Ahern <dsahern@...il.com>
To:	acme@...stprotocols.net, linux-kernel@...r.kernel.org
CC:	David Ahern <dsahern@...il.com>,
	Masami Hiramatsu <masami.hiramatsu.pt@...achi.com>,
	Srikar Dronamraju <srikar@...ux.vnet.ibm.com>
Subject: Re: [PATCH] perf probe: Improve error message when function not found

Masami:

If you do not have any problems with this version please Ack so Arnaldo 
will pick it up.

Thanks,

David

On 12/20/13, 1:04 PM, David Ahern wrote:
> When requesting a function from a userspace library the error message to
> the user is less than helpful. e.g.,
>
>      perf probe -x /lib64/libpthread-2.14.90.so -a 'lock_full=__pthread_mutex_lock_full'
>      no symbols found in /lib64/libpthread-2.14.90.so, maybe install a debug package?
>      Failed to load map.
>         Error: Failed to add events. (-22)
>
> yet the symbol really does exist but is a local symbol which is filtered:
>
> nm /lib64/libpthread-2.14.90.so | grep __pthread_mutex_lock_full
> 0000000000005700 t __pthread_mutex_lock_full
>
> With this patch:
>      perf probe -x /lib64/libpthread-2.14.90.so -a 'lock_full=__pthread_mutex_lock_full'
>
>      no symbols found in /lib64/libpthread-2.14.90.so, maybe install a debug package?
>      Failed to find function in /lib64/libpthread-2.14.90.so. Perhaps it is a local variable?
>        Error: Failed to add events. (-22)
>
> Signed-off-by: David Ahern <dsahern@...il.com>
> Cc: Masami Hiramatsu <masami.hiramatsu.pt@...achi.com>
> Cc: Srikar Dronamraju <srikar@...ux.vnet.ibm.com>
>
> diff --git a/tools/perf/util/probe-event.c b/tools/perf/util/probe-event.c
> index 9c6989ca2bea..2eac49096840 100644
> --- a/tools/perf/util/probe-event.c
> +++ b/tools/perf/util/probe-event.c
> @@ -2309,7 +2309,8 @@ static int convert_name_to_addr(struct perf_probe_event *pev, const char *exec)
>   	}
>   	available_func_filter = strfilter__new(function, NULL);
>   	if (map__load(map, filter_available_functions)) {
> -		pr_err("Failed to load map.\n");
> +		pr_err("Failed to find requested symbol in %s. Is it a global variable?\n",
> +		       name);
>   		goto out;
>   	}
>
>

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