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

Steven Rostedt
2022-11-14T17:20:54Z

On Wed, 2 Nov 2022 16:02:36 +0000
Jianlin Lv <iecedge@gmail.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@gmail.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);