linux-kernel - Re: [PATCH] tracepoint: Allow livepatch module add trace event

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Message-ID: <20221114122040.59ac8265@gandalf.local.home>
Date:   Mon, 14 Nov 2022 12:20:40 -0500
From:   Steven Rostedt <rostedt@...dmis.org>
To:     Jianlin Lv <iecedge@...il.com>
Cc:     alison.schofield@...el.com, davidgow@...gle.com,
        thunder.leizhen@...wei.com, jianlv@...y.com,
        linux-kernel@...r.kernel.org,
        Masami Hiramatsu <mhiramat@...nel.org>,
        Linux Trace Kernel <linux-trace-kernel@...r.kernel.org>
Subject: Re: [PATCH] tracepoint: Allow livepatch module add trace event

On Wed,  2 Nov 2022 16:02:36 +0000
Jianlin Lv <iecedge@...il.com> wrote:

> In the case of keeping the system running, the preferred method for
> tracing the kernel is dynamic tracing (kprobe), but the drawback of
> this method is that events are lost, especially when tracing packages
> in the network stack.
> 
> Livepatching provides a potential solution, which is to reimplement the
> function you want to replace and insert a static tracepoint.
> In such a way, custom stable static tracepoints can be expanded without
> rebooting the system.

Well that's definitely one way to implement dynamic trace events! :-D

-- Steve

> 
> Signed-off-by: Jianlin Lv <iecedge@...il.com>
> ---
>  kernel/tracepoint.c | 4 ++--
>  1 file changed, 2 insertions(+), 2 deletions(-)
> 
> diff --git a/kernel/tracepoint.c b/kernel/tracepoint.c
> index f23144af5743..8d1507dd0724 100644
> --- a/kernel/tracepoint.c
> +++ b/kernel/tracepoint.c
> @@ -571,8 +571,8 @@ static void for_each_tracepoint_range(
>  bool trace_module_has_bad_taint(struct module *mod)
>  {
>  	return mod->taints & ~((1 << TAINT_OOT_MODULE) | (1 << TAINT_CRAP) |
> -			       (1 << TAINT_UNSIGNED_MODULE) |
> -			       (1 << TAINT_TEST));
> +				(1 << TAINT_UNSIGNED_MODULE) | (1 << TAINT_TEST) |
> +				(1 << TAINT_LIVEPATCH));
>  }
>  
>  static BLOCKING_NOTIFIER_HEAD(tracepoint_notify_list);