linux-kernel - Re: [PATCH 02/35] perf probe: Clarify error message about not finding kernel modules debuginfo

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Message-Id: <20190308083033.cd4aceb08983875d07cabc1a@kernel.org>
Date:   Fri, 8 Mar 2019 08:30:33 +0900
From:   Masami Hiramatsu <mhiramat@...nel.org>
To:     Arnaldo Carvalho de Melo <acme@...nel.org>
Cc:     Ingo Molnar <mingo@...nel.org>, Jiri Olsa <jolsa@...nel.org>,
        Namhyung Kim <namhyung@...nel.org>,
        Clark Williams <williams@...hat.com>,
        linux-kernel@...r.kernel.org, linux-perf-users@...r.kernel.org,
        Arnaldo Carvalho de Melo <acme@...hat.com>,
        Adrian Hunter <adrian.hunter@...el.com>,
        Marcelo Ricardo Leitner <mleitner@...hat.com>,
        Masami Hiramatsu <mhiramat@...nel.org>
Subject: Re: [PATCH 02/35] perf probe: Clarify error message about not
 finding kernel modules debuginfo

On Thu,  7 Mar 2019 14:44:00 -0300
Arnaldo Carvalho de Melo <acme@...nel.org> wrote:

> From: Arnaldo Carvalho de Melo <acme@...hat.com>
> 
> 'perf probe' supports using just the kernel module name, but that will
> work only when the module is loaded, or using the full pathname to the
> file with the DWARF debug info, but the warning was cryptic:

Agreed, this looks good to me.

Acked-by: Masami Hiramatsu <mhiramat@...nel.org>

Thank you!

> 
> Before:
> 
>   # perf probe -m cls_flower -L fl_change
>   Failed to find the path for cls_flower: No such file or directory
>     Error: Failed to show lines.
>   #
> 
> After:
> 
>   # perf probe -m cls_flower -L fl_change
>   Module cls_flower is not loaded, please specify its full path name.
>     Error: Failed to show lines.
>   # perf probe -m /lib/modules/5.0.0-rc7+/kernel/net/sched/cls_flower.ko -L fl_change | head -7
>   <fl_change@...me/acme/git/linux/net/sched/cls_flower.c:0>
>         0  static int fl_change(struct net *net, struct sk_buff *in_skb,
>          		       struct tcf_proto *tp, unsigned long base,
>          		       u32 handle, struct nlattr **tca,
>          		       void **arg, bool ovr, struct netlink_ext_ack *extack)
>         4  {
>         5  	struct cls_fl_head *head = rtnl_dereference(tp->root);
>   #
> 
> The behaviour doesn't change when the module is loaded:
> 
>   # modprobe cls_flower
>   # perf probe -m cls_flower -L fl_change | head -7
>   <fl_change@...me/acme/git/linux/net/sched/cls_flower.c:0>
>         0  static int fl_change(struct net *net, struct sk_buff *in_skb,
>                                struct tcf_proto *tp, unsigned long base,
>                                u32 handle, struct nlattr **tca,
>                                void **arg, bool ovr, struct netlink_ext_ack *extack)
>         4  {
>         5         struct cls_fl_head *head = rtnl_dereference(tp->root);
>   #
> 
> Cc: Adrian Hunter <adrian.hunter@...el.com>
> Cc: Jiri Olsa <jolsa@...nel.org>
> Cc: Marcelo Ricardo Leitner <mleitner@...hat.com>
> Cc: Masami Hiramatsu <mhiramat@...nel.org>
> Cc: Namhyung Kim <namhyung@...nel.org>
> Link: https://lkml.kernel.org/n/tip-q4njvk9mshra00jacqjbzfn5@git.kernel.org
> Signed-off-by: Arnaldo Carvalho de Melo <acme@...hat.com>
> ---
>  tools/perf/util/probe-event.c | 9 ++++++---
>  1 file changed, 6 insertions(+), 3 deletions(-)
> 
> diff --git a/tools/perf/util/probe-event.c b/tools/perf/util/probe-event.c
> index 0030f9b9bf7e..a1b8d9649ca7 100644
> --- a/tools/perf/util/probe-event.c
> +++ b/tools/perf/util/probe-event.c
> @@ -472,9 +472,12 @@ static struct debuginfo *open_debuginfo(const char *module, struct nsinfo *nsi,
>  					strcpy(reason, "(unknown)");
>  			} else
>  				dso__strerror_load(dso, reason, STRERR_BUFSIZE);
> -			if (!silent)
> -				pr_err("Failed to find the path for %s: %s\n",
> -					module ?: "kernel", reason);
> +			if (!silent) {
> +				if (module)
> +					pr_err("Module %s is not loaded, please specify its full path name.\n", module);
> +				else
> +					pr_err("Failed to find the path for the kernel: %s\n", reason);
> +			}
>  			return NULL;
>  		}
>  		path = dso->long_name;
> -- 
> 2.20.1
> 


-- 
Masami Hiramatsu <mhiramat@...nel.org>