From: Ingo Molnar <mingo@kernel.org>
To: Pavel Machek <pavel@ucw.cz>
Cc: David Lang <david@lang.hm>, Josh Poimboeuf <jpoimboe@redhat.com>,
Frederic Weisbecker <fweisbec@gmail.com>,
Seth Jennings <sjenning@redhat.com>,
Masami Hiramatsu <masami.hiramatsu.pt@hitachi.com>,
Steven Rostedt <rostedt@goodmis.org>,
Ingo Molnar <mingo@redhat.com>, Jiri Slaby <jslaby@suse.cz>,
linux-kernel@vger.kernel.org,
Peter Zijlstra <a.p.zijlstra@chello.nl>,
Andrew Morton <akpm@linux-foundation.org>,
Linus Torvalds <torvalds@linux-foundation.org>,
Thomas Gleixner <tglx@linutronix.de>
Subject: Re: [RFC PATCH 0/2] kpatch: dynamic kernel patching
Date: Sun, 15 Jun 2014 08:57:31 +0200 [thread overview]
Message-ID: <20140615065731.GB20028@gmail.com> (raw)
In-Reply-To: <20140614203138.GA3853@xo-6d-61-c0.localdomain>
* Pavel Machek <pavel@ucw.cz> wrote:
> Hi!
>
> > > in terms of hit-patching kernels you are correct.
> > >
> > > but that's a far cry from what it sounded like you were demanding
> > > (that it must handle any kernel patch)
> >
> > No, I was not demanding that at all, my suggestion was:
> >
> > > My claim is that if a patch is correct/safe in the old fashioned
> > > way, then a fundamental principle is that a live patching
> > > subsystem must either safely apply, or safely reject the live
> > > patching attempt, independently from any user input.
> >
> > Note the 'if'. It could start simple and stupid, and only allow
> > cases where we know the patch must be trivially safe (because it
> > does not do much in terms of disturbing globally visible state).
> > That needs some tooling help, but apparently tooling help is in
> > place already.
>
> Actually, even if patch is very trivial, it will be difficult to
> determine if it is safe. Consider adding error check:
>
> int
> do_something(void)
> {
> #if 0
> if (1)
> return -1;
> #endif
> return 0;
> }
>
> void
> main(void)
> {
> if (do_something())
> printf("error happened\n");
> }
>
> Imagine changing that #if 0 to #if 1. But gcc at -O3 already
> optimized out the error message. So... do we compile whole second
> kernel and compare the binaries? I think I seen remark "don't try to
> do binary compares" somewhere...
Fair enough.
Thanks,
Ingo
next prev parent reply other threads:[~2014-06-15 6:57 UTC|newest]
Thread overview: 60+ messages / expand[flat|nested] mbox.gz Atom feed top
2014-05-01 15:52 [RFC PATCH 0/2] kpatch: dynamic kernel patching Josh Poimboeuf
2014-05-01 15:52 ` [RFC PATCH 1/2] kpatch: add TAINT_KPATCH flag Josh Poimboeuf
2014-05-01 15:52 ` [RFC PATCH 2/2] kpatch: add kpatch core module Josh Poimboeuf
2014-05-01 20:45 ` [RFC PATCH 0/2] kpatch: dynamic kernel patching Andi Kleen
2014-05-01 21:01 ` Josh Poimboeuf
2014-05-01 21:06 ` Andi Kleen
2014-05-01 21:27 ` Josh Poimboeuf
2014-05-01 21:39 ` Josh Poimboeuf
2014-05-02 1:30 ` Masami Hiramatsu
2014-05-02 8:37 ` Jiri Kosina
2014-05-02 13:29 ` Josh Poimboeuf
2014-05-02 13:10 ` Jiri Kosina
2014-05-02 13:37 ` Josh Poimboeuf
2014-05-05 23:34 ` David Lang
2014-05-05 23:52 ` Jiri Kosina
2014-05-06 1:59 ` David Lang
2014-05-06 12:17 ` Josh Poimboeuf
2014-05-06 7:32 ` Ingo Molnar
2014-05-06 8:03 ` Jiri Kosina
2014-05-06 12:23 ` Josh Poimboeuf
2014-05-07 12:19 ` Ingo Molnar
2014-05-09 1:46 ` David Lang
2014-05-09 2:45 ` Steven Rostedt
2014-05-09 4:07 ` Masami Hiramatsu
2014-05-05 8:55 ` Ingo Molnar
2014-05-05 13:26 ` Josh Poimboeuf
2014-05-05 14:10 ` Frederic Weisbecker
2014-05-05 18:43 ` Ingo Molnar
2014-05-05 21:49 ` Frederic Weisbecker
2014-05-06 12:12 ` Josh Poimboeuf
2014-05-06 12:33 ` Steven Rostedt
2014-05-06 22:49 ` Masami Hiramatsu
2014-05-06 14:05 ` Frederic Weisbecker
2014-05-06 14:50 ` Josh Poimboeuf
2014-05-07 12:24 ` Ingo Molnar
2014-05-07 15:41 ` Josh Poimboeuf
2014-05-07 15:57 ` Ingo Molnar
2014-05-07 16:43 ` Josh Poimboeuf
2014-05-07 22:56 ` David Lang
2014-05-08 6:12 ` Ingo Molnar
2014-05-08 6:50 ` David Lang
2014-05-08 7:08 ` Ingo Molnar
2014-05-08 7:29 ` Masami Hiramatsu
2014-05-08 12:48 ` Josh Poimboeuf
2014-05-09 6:21 ` Masami Hiramatsu
2014-06-14 20:31 ` Pavel Machek
2014-06-15 6:57 ` Ingo Molnar [this message]
2014-05-06 11:45 ` Masami Hiramatsu
2014-05-06 12:26 ` Steven Rostedt
2014-05-06 22:33 ` Masami Hiramatsu
2014-05-16 16:27 ` Jiri Kosina
2014-05-16 17:14 ` Josh Poimboeuf
2014-05-20 9:37 ` Jiri Kosina
2014-05-20 12:59 ` Josh Poimboeuf
2014-05-16 18:09 ` Masami Hiramatsu
2014-05-17 22:46 ` Vojtech Pavlik
2014-05-16 18:55 ` Steven Rostedt
2014-05-16 22:32 ` Jiri Kosina
2014-05-17 0:27 ` Steven Rostedt
2014-05-17 7:10 ` Jiri Kosina
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