From: Michael Ellerman <mpe@ellerman•id.au>
To: Miroslav Benes <mbenes@suse•cz>
Cc: linuxppc-dev@ozlabs•org, bsingharora@gmail•com, duwe@lst•de,
linux-kernel@vger•kernel.org, rostedt@goodmis•org,
kamalesh@linux•vnet.ibm.com, pmladek@suse•com, jeyu@redhat•com,
jikos@kernel•org, live-patching@vger•kernel.org
Subject: Re: [PATCH 2/5] livepatch: Allow architectures to specify an alternate ftrace location
Date: Thu, 14 Apr 2016 23:06:18 +1000 [thread overview]
Message-ID: <1460639178.21066.3.camel@ellerman.id.au> (raw)
In-Reply-To: <alpine.LNX.2.00.1604141354130.10605@pobox.suse.cz>
On Thu, 2016-04-14 at 14:01 +0200, Miroslav Benes wrote:
> On Wed, 13 Apr 2016, Michael Ellerman wrote:
> > diff --git a/kernel/livepatch/core.c b/kernel/livepatch/core.c
> > index d68fbf63b083..b0476bb30f92 100644
> > --- a/kernel/livepatch/core.c
> > +++ b/kernel/livepatch/core.c
> > @@ -298,6 +298,19 @@ unlock:
> > rcu_read_unlock();
> > }
> >
> > +/*
> > + * Convert a function address into the appropriate ftrace location.
> > + *
> > + * Usually this is just the address of the function, but on some architectures
> > + * it's more complicated so allow them to provide a custom behaviour.
> > + */
> > +#ifndef klp_get_ftrace_location
> > +static unsigned long klp_get_ftrace_location(unsigned long faddr)
> > +{
> > + return faddr;
> > +}
> > +#endif
>
> Whoah, what an ugly hack :)
Hey it's a "cool trick" ;)
> Note to my future self - This is what you want to do if you need a weak
> static inline function.
>
> static inline is probably unnecessary here so __weak function would be
> enough. It would introduce powerpc-specific livepatch.c though because of
> it and this is not worth it.
Yeah that was my logic, at least for now. We can always change it in future
to be weak if anyone cares deeply.
> > static void klp_disable_func(struct klp_func *func)
> > {
> > struct klp_ops *ops;
> > @@ -312,8 +325,14 @@ static void klp_disable_func(struct klp_func *func)
> > return;
> >
> > if (list_is_singular(&ops->func_stack)) {
> > + unsigned long ftrace_loc;
>
> This is a nit, but could you move the definition up to have them all in
> one place to be consistent with the rest of the code? The same applies to
> klp_enable_func() below.
Hmm, actually I moved it in there because you pointed out we only needed it
inside the if:
http://lkml.kernel.org/r/alpine.LNX.2.00.1603151113020.20252@pobox.suse.cz
Thinking about it, we need ftrace_loc only in cases where we call
ftrace_set_filter_ip() right? So we can move klp_get_ftrace_location()
call to appropriate if branch both in klp_disable_func() and
klp_enable_func().
But I guess you meant the function call, not the variable declaration.
Personally I think it's better this way, as the variable is in scope for the
shortest possible amount of time, but I can change it if you want me to.
cheers
next prev parent reply other threads:[~2016-04-14 13:06 UTC|newest]
Thread overview: 37+ messages / expand[flat|nested] mbox.gz Atom feed top
2016-04-13 12:53 [PATCH 0/5] Live patching for powerpc Michael Ellerman
2016-04-13 12:53 ` [PATCH 1/5] ftrace: Make ftrace_location_range() global Michael Ellerman
2016-04-19 10:16 ` [1/5] " Michael Ellerman
2016-04-13 12:53 ` [PATCH 2/5] livepatch: Allow architectures to specify an alternate ftrace location Michael Ellerman
2016-04-14 12:01 ` Miroslav Benes
2016-04-14 13:06 ` Michael Ellerman [this message]
2016-04-14 14:06 ` Miroslav Benes
2016-04-19 10:16 ` [2/5] " Michael Ellerman
2016-04-13 12:53 ` [PATCH 3/5] powerpc/livepatch: Add livepatch header Michael Ellerman
2016-04-14 12:18 ` Miroslav Benes
2016-04-14 12:23 ` Miroslav Benes
2016-04-14 13:12 ` Michael Ellerman
2016-04-19 10:16 ` [3/5] " Michael Ellerman
2016-04-13 12:53 ` [PATCH 4/5] powerpc/livepatch: Add livepatch stack to struct thread_info Michael Ellerman
2016-04-19 10:16 ` [4/5] " Michael Ellerman
2016-04-13 12:53 ` [PATCH 5/5] powerpc/livepatch: Add live patching support on ppc64le Michael Ellerman
2016-04-19 10:16 ` [5/5] " Michael Ellerman
2016-04-13 13:01 ` [PATCH 0/5] Live patching for powerpc Miroslav Benes
2016-04-13 13:22 ` Jiri Kosina
2016-04-14 6:49 ` Michael Ellerman
2016-04-14 12:57 ` Torsten Duwe
2016-04-14 13:08 ` Michael Ellerman
2016-04-14 15:20 ` Torsten Duwe
2016-04-14 16:41 ` Josh Poimboeuf
2016-04-15 11:22 ` Michael Ellerman
2016-04-15 12:59 ` Josh Poimboeuf
2016-04-15 13:21 ` Michael Ellerman
2016-04-14 14:34 ` Jiri Kosina
2016-04-15 12:24 ` Michael Ellerman
2016-04-15 15:07 ` Jiri Kosina
2016-04-19 21:42 ` Balbir Singh
2016-04-19 21:52 ` Jiri Kosina
2016-04-13 18:22 ` Jessica Yu
2016-04-14 13:28 ` Miroslav Benes
2016-04-14 19:20 ` Jessica Yu
2016-04-15 8:28 ` Miroslav Benes
2016-04-15 10:01 ` Michael Ellerman
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