lkml.org 
[lkml]   [2021]   [Jun]   [10]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
Date
From
SubjectRe: [PATCH] tools/perf probe: Print a hint if adding a probe fails
Hi Naveen,

On Thu, 10 Jun 2021 15:14:42 +0530
"Naveen N. Rao" <naveen.n.rao@linux.vnet.ibm.com> wrote:

> Adding a probe can fail in a few scenarios. perf already checks for the
> address in the kprobe blacklist. However, the address could still be a
> jump label, or have a BUG_ON(). In such cases, it isn't always evident
> why adding the probe failed. Add a hint so that the user knows how to
> proceed.
>

Thanks for the report.

Since now there is <tracefs>/error_log, if you see any errors in registering
probe-events, perf probe should dump the error_log for the hint message.
Also, kprobes should return the correct different error code for each
errors.

Thank you,

> Reported-by: Aneesh Kumar K.V <aneesh.kumar@linux.ibm.com>
> Signed-off-by: Naveen N. Rao <naveen.n.rao@linux.vnet.ibm.com>
> ---
> tools/perf/builtin-probe.c | 5 ++++-
> 1 file changed, 4 insertions(+), 1 deletion(-)
>
> diff --git a/tools/perf/builtin-probe.c b/tools/perf/builtin-probe.c
> index 6b150756677014..ff9f3fdce600dd 100644
> --- a/tools/perf/builtin-probe.c
> +++ b/tools/perf/builtin-probe.c
> @@ -352,8 +352,11 @@ static int perf_add_probe_events(struct perf_probe_event *pevs, int npevs)
> }
>
> ret = apply_perf_probe_events(pevs, npevs);
> - if (ret < 0)
> + if (ret < 0) {
> + pr_info("Hint: Check dmesg to understand reason for probe failure.\n"
> + " Consider probing at the next/previous instruction.\n");
> goto out_cleanup;
> + }
>
> for (i = k = 0; i < npevs; i++)
> k += pevs[i].ntevs;
>
> base-commit: 0808b3d5b7514dc856178dbc509929329bbf301d
> --
> 2.31.1
>


--
Masami Hiramatsu <mhiramat@kernel.org>

\
 
 \ /
  Last update: 2021-06-10 12:31    [W:0.057 / U:0.112 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site