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

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Message-ID: <20160503134858.n6fto6tasih2rzmi@treble>
Date:	Tue, 3 May 2016 08:48:58 -0500
From:	Josh Poimboeuf <jpoimboe@...hat.com>
To:	Petr Mladek <pmladek@...e.com>
Cc:	Jessica Yu <jeyu@...hat.com>, Jiri Kosina <jikos@...nel.org>,
	Miroslav Benes <mbenes@...e.cz>,
	Ingo Molnar <mingo@...hat.com>,
	Peter Zijlstra <peterz@...radead.org>,
	Michael Ellerman <mpe@...erman.id.au>,
	Heiko Carstens <heiko.carstens@...ibm.com>,
	live-patching@...r.kernel.org, linux-kernel@...r.kernel.org,
	x86@...nel.org, linuxppc-dev@...ts.ozlabs.org,
	linux-s390@...r.kernel.org, Vojtech Pavlik <vojtech@...e.com>,
	Jiri Slaby <jslaby@...e.cz>,
	Chris J Arges <chris.j.arges@...onical.com>,
	Andy Lutomirski <luto@...nel.org>
Subject: Re: [RFC PATCH v2 13/18] livepatch: separate enabled and patched
 states

On Tue, May 03, 2016 at 11:30:12AM +0200, Petr Mladek wrote:
> 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 <jpoimboe@...hat.com>
> > ---
> >  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.

Good idea, thanks.

-- 
Josh