linux-kernel - Re: [PATCH v5 3/3] livepatch: add transition notices

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Date:   Tue, 12 Sep 2017 11:29:20 +0200 (CEST)
From:   Miroslav Benes <mbenes@...e.cz>
To:     Joe Lawrence <joe.lawrence@...hat.com>
cc:     live-patching@...r.kernel.org, linux-kernel@...r.kernel.org,
        Josh Poimboeuf <jpoimboe@...hat.com>,
        Jessica Yu <jeyu@...nel.org>, Jiri Kosina <jikos@...nel.org>,
        Petr Mladek <pmladek@...e.com>,
        Chris J Arges <chris.j.arges@...onical.com>
Subject: Re: [PATCH v5 3/3] livepatch: add transition notices

On Thu, 31 Aug 2017, Joe Lawrence wrote:

> Log a few kernel debug messages at the beginning of the following livepatch
> transition functions:
> 
>   klp_complete_transition()
>   klp_cancel_transition()
>   klp_init_transition()
>   klp_reverse_transition()
> 
> Also update the log notice message in klp_start_transition() for similar
> verbiage as the above messages.
> 
> Suggested-by: Josh Poimboeuf <jpoimboe@...hat.com>
> Signed-off-by: Joe Lawrence <joe.lawrence@...hat.com>
> ---
>  kernel/livepatch/transition.c | 18 +++++++++++++++++-
>  1 file changed, 17 insertions(+), 1 deletion(-)
> 
> diff --git a/kernel/livepatch/transition.c b/kernel/livepatch/transition.c
> index 53887f0bca10..3d44a3cf27be 100644
> --- a/kernel/livepatch/transition.c
> +++ b/kernel/livepatch/transition.c
> @@ -82,6 +82,10 @@ static void klp_complete_transition(void)
>  	unsigned int cpu;
>  	bool immediate_func = false;
>  
> +	pr_debug("'%s': completing %s transition\n",
> +		 klp_transition_patch->mod->name,
> +		 klp_target_state == KLP_PATCHED ? "patching" : "unpatching");

The only downside here is that you can get a message about starting 
patching transition and then a message about completing unpatching 
transition, because the patching failed and klp_cancel_transition() was 
called. I think we can live with that, because there would be a message 
from klp_cancel_transition() as well and hopefully no one would be 
confused.

> @@ -163,6 +167,9 @@ void klp_cancel_transition(void)
>  	if (WARN_ON_ONCE(klp_target_state != KLP_PATCHED))
>  		return;
>  
> +	pr_debug("'%s': canceling transition, unpatching\n",
> +		 klp_transition_patch->mod->name);
> +

This one.

Acked-by: Miroslav Benes <mbenes@...e.cz>

Miroslav