Subject: Re: [RFC PATCH v2 13/18] livepatch: separate enabled and patched states

From: Petr Mladek <[email-masked]>
Date: Tue, 3 May 2016 11:30:12 +0200

On Thu 2016-04-28 15:44:44, Josh Poimboeuf wrote:
> Once we have a consistency model, patches and their objects will be
> enabled and disabled at different times.  For example, when a patch is
> disabled, its loaded objects' funcs can remain registered with ftrace
> indefinitely until the unpatching operation is complete and they're no
> longer in use.
> 
> It's less confusing if we give them different names: patches can be
> enabled or disabled; objects (and their funcs) can be patched or
> unpatched:
> 
> - Enabled means that a patch is logically enabled (but not necessarily
>   fully applied).
> 
> - Patched means that an object's funcs are registered with ftrace and
>   added to the klp_ops func stack.
> 
> Also, since these states are binary, represent them with booleans
> instead of ints.
> 
> Signed-off-by: Josh Poimboeuf <[email-masked]>
> ---
>  include/linux/livepatch.h | 17 ++++-------
>  kernel/livepatch/core.c   | 72 +++++++++++++++++++++++------------------------
>  2 files changed, 42 insertions(+), 47 deletions(-)
> 
> diff --git a/kernel/livepatch/core.c b/kernel/livepatch/core.c
> index 6ea6880..2b59230 100644
> --- a/kernel/livepatch/core.c
> +++ b/kernel/livepatch/core.c
> @@ -622,20 +622,20 @@ static ssize_t enabled_store(struct kobject *kobj, struct kobj_attribute *attr,
>  	if (ret)
>  		return -EINVAL;
>  
> -	if (val != KLP_DISABLED && val != KLP_ENABLED)
> +	if (val > 1)
>  		return -EINVAL;

It would be cleaner to get "val" via kstrtobool(). It guarantees that
the value is true or false. Another nice win is that it accepts
Y/y/1/N/n/0 as the input.

>  	patch = container_of(kobj, struct klp_patch, kobj);
>  
>  	mutex_lock(&klp_mutex);
>  
> -	if (val == patch->state) {
> +	if (patch->enabled == val) {

Also this check will be cleaner if "val" is a boolean.

Best Regards,
Petr