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From: Miroslav Benes <mbenes@suse.cz>
To: Josh Poimboeuf <jpoimboe@redhat.com>
Cc: Petr Mladek <pmladek@suse.com>,
	Joe Lawrence <joe.lawrence@redhat.com>,
	jikos@kernel.org, linux-kernel@vger.kernel.org,
	live-patching@vger.kernel.org
Subject: Re: [RFC PATCH 2/2] livepatch: Clear relocation targets on a module removal
Date: Thu, 5 Sep 2019 14:49:00 +0200 (CEST)
Message-ID: <alpine.LSU.2.21.1909051445410.25712@pobox.suse.cz> (raw)
In-Reply-To: <20190905123558.d4zh4h5pnej6pcuk@treble>

On Thu, 5 Sep 2019, Josh Poimboeuf wrote:

> On Thu, Sep 05, 2019 at 02:03:34PM +0200, Miroslav Benes wrote:
> > > >   + I would like to better understand the scope of the current
> > > >     problems. It is about modifying code in the livepatch that
> > > >     depends on position of the related code:
> > > > 
> > > >       + relocations are rather clear; we will need them anyway
> > > > 	to access non-public (static) API from the original code.
> > > > 
> > > >       + What are the other changes?
> > > 
> > > I think the .klp.arch sections are the big ones:
> > > 
> > >   .klp.arch.altinstructions
> > >   .klp.arch.parainstructions
> > >   .klp.arch.jump_labels (doesn't exist yet)
> > > 
> > > And that's just x86...
> > 
> > I may misunderstand, but we have .klp.arch sections because para and 
> > alternatives have to be processed after relocations. And if we cannot get 
> > rid of relocations completely, because of static symbols, then we cannot 
> > get rid of .klp.arch sections either.
> 
> With late module patching gone, the module code can just process the klp
> relocations at the same time it processes normal relocations.
> 
> Then the normal module alt/para/jump_label processing code can be used
> instead of arch_klp_init_object_loaded().

Ah, of course. I obviously cannot grasp the idea of not having late module 
patching :)
 
> Note this also means that Joe's patches can remove copy_module_elf() and
> free_module_elf().  And module_arch_freeing_init() in s390.

Correct.

So yes, it would simplify the code a lot. I am still worried about the 
consequences.

> > > And then of course there's the klp coming/going notifiers which have
> > > also been an additional source of complexity.
> > 
> > True, but I think we (me and Petr) do not consider it as much of a problem 
> > as you.
> 
> It's less of an issue than .klp.arch and all the related code which can
> be removed.

Ok.

Miroslav

  reply index

Thread overview: 44+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2019-07-19 12:28 [RFC PATCH 0/2] " Miroslav Benes
2019-07-19 12:28 ` [PATCH 1/2] livepatch: Nullify obj->mod in klp_module_coming()'s error path Miroslav Benes
2019-07-28 19:45   ` Josh Poimboeuf
2019-08-19 11:26     ` Petr Mladek
2019-07-19 12:28 ` [RFC PATCH 2/2] livepatch: Clear relocation targets on a module removal Miroslav Benes
2019-07-22  9:33   ` Petr Mladek
2019-08-14 12:33     ` Miroslav Benes
2019-07-28 20:04   ` Josh Poimboeuf
2019-08-14 11:06     ` Miroslav Benes
2019-08-14 15:12       ` Josh Poimboeuf
2019-08-16  9:46         ` Petr Mladek
2019-08-22 22:36           ` Josh Poimboeuf
2019-08-23  8:13             ` Petr Mladek
2019-08-26 14:54               ` Josh Poimboeuf
2019-08-27 15:05                 ` Joe Lawrence
2019-08-27 15:37                   ` Josh Poimboeuf
2019-09-02 16:13                 ` Miroslav Benes
2019-09-02 17:05                   ` Joe Lawrence
2019-09-03 13:02                     ` Miroslav Benes
2019-09-04  8:49                       ` Petr Mladek
2019-09-04 16:26                         ` Joe Lawrence
2019-09-05  2:50                         ` Josh Poimboeuf
2019-09-05 11:09                           ` Petr Mladek
2019-09-05 11:19                             ` Jiri Kosina
2019-09-05 13:23                               ` Josh Poimboeuf
2019-09-05 13:31                                 ` Jiri Kosina
2019-09-05 13:42                                   ` Josh Poimboeuf
2019-09-05 11:39                             ` Joe Lawrence
2019-09-05 13:08                             ` Josh Poimboeuf
2019-09-05 13:15                               ` Josh Poimboeuf
2019-09-05 13:52                                 ` Petr Mladek
2019-09-05 14:28                                   ` Josh Poimboeuf
2019-09-05 12:03                           ` Miroslav Benes
2019-09-05 12:35                             ` Josh Poimboeuf
2019-09-05 12:49                               ` Miroslav Benes [this message]
2019-09-05 11:52                         ` Miroslav Benes
2019-09-05  2:32                       ` Josh Poimboeuf
2019-09-05 12:16                         ` Miroslav Benes
2019-09-05 12:54                           ` Josh Poimboeuf
2019-09-06 12:51                             ` Miroslav Benes
2019-09-06 15:38                               ` Joe Lawrence
2019-09-06 16:45                               ` Josh Poimboeuf
2019-08-26 13:44         ` Nicolai Stange
2019-08-26 15:02           ` Josh Poimboeuf

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