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From: Jessica Yu <jeyu@kernel.org>
To: Peter Zijlstra <peterz@infradead.org>
Cc: Miroslav Benes <mbenes@suse.cz>,
	Joe Lawrence <joe.lawrence@redhat.com>,
	Steven Rostedt <rostedt@goodmis.org>,
	x86@kernel.org, linux-kernel@vger.kernel.org,
	mhiramat@kernel.org, bristot@redhat.com, jbaron@akamai.com,
	torvalds@linux-foundation.org, tglx@linutronix.de,
	mingo@kernel.org, namit@vmware.com, hpa@zytor.com,
	luto@kernel.org, ard.biesheuvel@linaro.org, jpoimboe@redhat.com,
	live-patching@vger.kernel.org
Subject: Re: [PATCH v3 5/6] x86/ftrace: Use text_poke()
Date: Wed, 16 Oct 2019 11:36:10 +0200
Message-ID: <20191016093610.GA9193@linux-8ccs> (raw)
In-Reply-To: <20191016092304.GL2294@hirez.programming.kicks-ass.net>

+++ Peter Zijlstra [16/10/19 11:23 +0200]:
>On Wed, Oct 16, 2019 at 08:51:27AM +0200, Miroslav Benes wrote:
>> On Tue, 15 Oct 2019, Joe Lawrence wrote:
>>
>> > On 10/15/19 10:13 AM, Miroslav Benes wrote:
>> > > Yes, it does. klp_module_coming() calls module_disable_ro() on all
>> > > patching modules which patch the coming module in order to call
>> > > apply_relocate_add(). New (patching) code for a module can be relocated
>> > > only when the relevant module is loaded.
>> >
>> > FWIW, would the LPC blue-sky2 model (ie, Steve's suggestion @ plumber's where
>> > livepatches only patch a single object and updates are kept on disk to handle
>> > coming module updates as they are loaded) eliminate those outstanding
>> > relocations and the need to perform this late permission flipping?
>>
>> Yes, it should, but we don't have to wait for it. PeterZ proposed a
>> different solution to this specific issue in
>> https://lore.kernel.org/lkml/20191015141111.GP2359@hirez.programming.kicks-ass.net/
>>
>> It should not be a problem to create a live patch module like that and the
>> code in kernel/livepatch/ is almost ready. Something like
>> module_section_disable_ro(mod, section) (and similar for X protection)
>> should be enough. Module reloads would still require juggling with the
>> protections, but I think it is all feasible.
>
>Just had a browse around the module code, and while the section info is
>in load_info, it doesn't get retained for active modules.
>
>So I suppose I'll go add that for KLP enabled things.

Elf section info does get saved for livepatch modules though, see
mod->klp_info. And wouldn't this only be needed for livepatch modules?

  reply index

Thread overview: 45+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
     [not found] <20191007081945.10951536.8@infradead.org>
     [not found] ` <20191008104335.6fcd78c9@gandalf.local.home>
     [not found]   ` <20191009224135.2dcf7767@oasis.local.home>
     [not found]     ` <20191010092054.GR2311@hirez.programming.kicks-ass.net>
     [not found]       ` <20191010091956.48fbcf42@gandalf.local.home>
     [not found]         ` <20191010140513.GT2311@hirez.programming.kicks-ass.net>
     [not found]           ` <20191010115449.22044b53@gandalf.local.home>
     [not found]             ` <20191010172819.GS2328@hirez.programming.kicks-ass.net>
     [not found]               ` <20191011125903.GN2359@hirez.programming.kicks-ass.net>
     [not found]                 ` <20191015130739.GA23565@linux-8ccs>
     [not found]                   ` <20191015135634.GK2328@hirez.programming.kicks-ass.net>
2019-10-15 14:13                     ` Miroslav Benes
2019-10-15 15:06                       ` Joe Lawrence
2019-10-15 15:31                         ` Jessica Yu
2019-10-15 22:17                           ` Joe Lawrence
2019-10-15 22:27                             ` Steven Rostedt
2019-10-16  7:42                               ` Peter Zijlstra
2019-10-16 10:15                                 ` Miroslav Benes
2019-10-21 15:05                                 ` Josh Poimboeuf
2020-01-20 16:50                                   ` Josh Poimboeuf
2020-01-21  8:35                                     ` Miroslav Benes
2020-01-21 16:10                                       ` Josh Poimboeuf
2020-01-22 10:09                                         ` Miroslav Benes
2020-01-22 21:42                                           ` Josh Poimboeuf
2020-01-28  9:28                                             ` Miroslav Benes
2020-01-28 15:00                                               ` Josh Poimboeuf
2020-01-28 15:40                                                 ` Petr Mladek
2020-01-28 17:02                                                   ` Josh Poimboeuf
2020-01-29  0:46                                                     ` Jiri Kosina
2020-01-29  2:17                                                       ` Josh Poimboeuf
2020-01-29  3:14                                                         ` Jiri Kosina
2020-01-29 12:28                                                     ` Miroslav Benes
2020-01-29 15:59                                                       ` Josh Poimboeuf
2020-01-30  9:53                                                         ` Petr Mladek
2020-01-30 14:17                                                           ` Josh Poimboeuf
2020-01-31  7:17                                                             ` Petr Mladek
2020-01-22 12:15                                         ` Miroslav Benes
2020-01-22 15:05                                           ` Miroslav Benes
2020-01-22 22:03                                             ` Josh Poimboeuf
2020-01-23 10:19                                               ` Martin Jambor
2019-10-16  7:49                               ` Peter Zijlstra
2019-10-16 10:20                                 ` Miroslav Benes
2019-10-16 13:29                                   ` Miroslav Benes
2019-10-18 13:03                                     ` Jessica Yu
2019-10-18 13:40                                       ` Petr Mladek
2019-10-21 14:14                                         ` Jessica Yu
2019-10-21 15:31                                         ` Josh Poimboeuf
2019-10-22  8:27                                       ` Miroslav Benes
2019-10-22 14:31                                         ` Josh Poimboeuf
2019-10-23  9:04                                           ` Miroslav Benes
2019-10-16  6:51                         ` Miroslav Benes
2019-10-16  9:23                           ` Peter Zijlstra
2019-10-16  9:36                             ` Jessica Yu [this message]
2019-10-16  9:51                               ` Peter Zijlstra
2019-10-16 12:39                           ` Peter Zijlstra
2019-10-22  8:45                             ` Miroslav Benes

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