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

From: Masami Hiramatsu
Date: Thu Mar 07 2019 - 18:30:42 EST


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

> From: Arnaldo Carvalho de Melo <acme@xxxxxxxxxx>
>
> '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@xxxxxxxxxx>

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@/home/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@/home/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@xxxxxxxxx>
> Cc: Jiri Olsa <jolsa@xxxxxxxxxx>
> Cc: Marcelo Ricardo Leitner <mleitner@xxxxxxxxxx>
> Cc: Masami Hiramatsu <mhiramat@xxxxxxxxxx>
> Cc: Namhyung Kim <namhyung@xxxxxxxxxx>
> Link: https://lkml.kernel.org/n/tip-q4njvk9mshra00jacqjbzfn5@xxxxxxxxxxxxxx
> Signed-off-by: Arnaldo Carvalho de Melo <acme@xxxxxxxxxx>
> ---
> 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@xxxxxxxxxx>