On Thu, 18 Jun 2020 18:33:01 +0200
Sascha Ortmann <sascha.ortmann@xxxxxxxxxxxxxxxxxxxx> wrote:
> Fix boottime kprobe events to report and abort after each failure when
> adding probes.
>
> As an example, when we try to set multiprobe kprobe events in
> bootconfig like this:
>
> ftrace.event.kprobes.vfsevents {
> probes = "vfs_read $arg1 $arg2,,
> !error! not reported;?", // leads to error
> "vfs_write $arg1 $arg2"
> }
>
> This will not work as expected. After
> commit da0f1f4167e3af69e ("tracing/boottime: Fix kprobe event API usage"),
> the function trace_boot_add_kprobe_event will not produce any error
> message when adding a probe fails at kprobe_event_gen_cmd_start.
> Furthermore, we continue to add probes when kprobe_event_gen_cmd_end fails
> (and kprobe_event_gen_cmd_start did not fail). In this case the function
> even returns successfully when the last call to kprobe_event_gen_cmd_end
> is successful.
>
> The behaviour of reporting and aborting after failures is not
> consistent.
>
> The function trace_boot_add_kprobe_event now reports each failure and
> stops adding probes immediately.
Thanks for updating. This looks good to me.
Acked-by: Masami Hiramatsu <mhiramat@xxxxxxxxxx>
and
Fixes: da0f1f4167e3 ("tracing/boottime: Fix kprobe event API usage")
Thank you!
>
> Cc: linux-kernel@xxxxxxxxxxxx
> Co-developed-by: Maximilian Werner <maximilian.werner96@xxxxxxxxx>
> Signed-off-by: Maximilian Werner <maximilian.werner96@xxxxxxxxx>
> Signed-off-by: Sascha Ortmann <sascha.ortmann@xxxxxxxxxxxxxxxxxxxx>
> ---
> kernel/trace/trace_boot.c | 8 ++++++--
> 1 file changed, 6 insertions(+), 2 deletions(-)
>
> diff --git a/kernel/trace/trace_boot.c b/kernel/trace/trace_boot.c
> index 9de29bb45a27..be893eb22071 100644
> --- a/kernel/trace/trace_boot.c
> +++ b/kernel/trace/trace_boot.c
> @@ -101,12 +101,16 @@ trace_boot_add_kprobe_event(struct xbc_node *node, const char *event)
> kprobe_event_cmd_init(&cmd, buf, MAX_BUF_LEN);
>
> ret = kprobe_event_gen_cmd_start(&cmd, event, val);
> - if (ret)
> + if (ret) {
> + pr_err("Failed to generate probe: %s\n", buf);
> break;
> + }
>
> ret = kprobe_event_gen_cmd_end(&cmd);
> - if (ret)
> + if (ret) {
> pr_err("Failed to add probe: %s\n", buf);
> + break;
> + }
> }
>
> return ret;
> --
> 2.17.1
>
--
Masami Hiramatsu <mhiramat@xxxxxxxxxx>
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