From: Mathieu Desnoyers <mathieu.desnoyers@polymtl.ca>
To: Ingo Molnar <mingo@elte.hu>
Cc: Linus Torvalds <torvalds@linux-foundation.org>,
Jiri Slaby <jirislaby@gmail.com>,
David Miller <davem@davemloft.net>,
zdenek.kabelac@gmail.com, rjw@sisk.pl,
paulmck@linux.vnet.ibm.com, akpm@linux-foundation.org,
linux-ext4@vger.kernel.org, herbert@gondor.apana.org.au,
penberg@cs.helsinki.fi, clameter@sgi.com,
linux-kernel@vger.kernel.org, Andi Kleen <andi@firstfloor.org>,
pageexec@freemail.hu, "H. Peter Anvin" <hpa@zytor.com>,
Jeremy Fitzhardinge <jeremy@goop.org>
Subject: Re: [PATCH 1/1] x86: fix text_poke
Date: Fri, 25 Apr 2008 12:11:36 -0400 [thread overview]
Message-ID: <20080425161136.GD9503@Krystal> (raw)
In-Reply-To: <20080425155953.GA11243@elte.hu>
* Ingo Molnar (mingo@elte.hu) wrote:
>
> * Mathieu Desnoyers <mathieu.desnoyers@polymtl.ca> wrote:
>
> > Woooow, just a sec here. I removed the atomicity test _because_ there
> > happen to be a case where it's safe to do non-atomic instruction
> > modification. If we do :
> >
> > 1) replace the instruction first byte by a breakpoint, execute an
> > instruction bypass (see the immediate values patches for detail)
> > 2) modify the instruction non-atomically
> > 3) put back the original instruction first byte.
> >
> > That's why I removed the BUG_ONs at the beginning of the function.
> > That's also why it's required to deal with page crossing.
>
> but the code as-is is nonsensical. It checks for:
>
> BUG_ON(len > sizeof(long));
>
> but then deals with page crossing...
>
That was in the initial version, before my patch, yes. I dealt with page
crossing at first, then added a more restrictive test to "play safe" (I
should have removed the page-crossing code at that point), but later on
noticed that there was a single case where it's valid to do non-atomic
updates, and it's when the execution flow is bypassed by a breakpoint
(as the immediate values are doing), so the last patch you have removes
the restrictive test and lets the page-crossing code in place.
> it should also rename text_poke_early() to text_poke_core(), and call
> _that_ from text_poke() if core_kernel_text(). From that alone the whole
> poke_text() function would look a whole lot cleaner.
>
hrm, I am not convinced it's safe to call vmap() very early at boot
time. In the immediate values implementation, I do call text_poke very
very early at boot to populate the initial values. Or maybe are you
proposing something different from what I currently understand ?
Mathieu
> Ingo
--
Mathieu Desnoyers
Computer Engineering Ph.D. Student, Ecole Polytechnique de Montreal
OpenPGP key fingerprint: 8CD5 52C3 8E3C 4140 715F BA06 3F25 A8FE 3BAE 9A68
next prev parent reply other threads:[~2008-04-25 16:16 UTC|newest]
Thread overview: 183+ messages / expand[flat|nested] mbox.gz Atom feed top
2008-04-19 13:22 2.6.25-git1: Solid hang on HP nx6325 (64-bit) Rafael J. Wysocki
2008-04-20 19:04 ` 2.6.25-git2: BUG: unable to handle kernel paging request at ffffffffffffffff Rafael J. Wysocki
2008-04-20 19:14 ` Rafael J. Wysocki
2008-04-20 21:31 ` Linus Torvalds
2008-04-21 1:18 ` Herbert Xu
2008-04-21 2:08 ` Paul E. McKenney
2008-04-21 4:59 ` Paul E. McKenney
2008-04-21 5:47 ` Paul E. McKenney
2008-04-21 13:00 ` Ingo Molnar
2008-04-21 16:06 ` Linus Torvalds
2008-04-21 16:24 ` Rafael J. Wysocki
2008-04-21 15:49 ` Linus Torvalds
2008-04-21 17:05 ` Paul E. McKenney
2008-04-21 17:30 ` Linus Torvalds
2008-04-21 17:43 ` Paul E. McKenney
2008-04-22 1:03 ` Herbert Xu
2008-04-22 13:36 ` Paul E. McKenney
2008-04-21 16:12 ` Rafael J. Wysocki
2008-04-21 16:54 ` Linus Torvalds
2008-04-21 17:06 ` Jiri Slaby
2008-04-21 17:19 ` Rafael J. Wysocki
2008-04-21 17:48 ` Linus Torvalds
2008-04-21 18:22 ` Rafael J. Wysocki
2008-04-21 19:38 ` Jiri Slaby
2008-04-21 20:39 ` David Miller
2008-04-21 21:18 ` Jiri Slaby
2008-04-21 21:58 ` Jiri Slaby
2008-04-21 22:26 ` Jiri Slaby
2008-04-21 22:54 ` Paul E. McKenney
2008-04-21 23:02 ` Jiri Slaby
2008-04-21 23:11 ` Zdenek Kabelac
2008-04-21 23:17 ` Jiri Slaby
2008-04-22 0:54 ` Rafael J. Wysocki
2008-04-22 1:14 ` Linus Torvalds
2008-04-22 1:30 ` Rafael J. Wysocki
2008-04-22 9:49 ` Jiri Slaby
2008-04-22 9:53 ` Ingo Molnar
2008-04-22 18:35 ` Zdenek Kabelac
2008-04-22 18:48 ` Linus Torvalds
2008-04-22 20:34 ` device_pm_add (was: Re: 2.6.25-git2: BUG: unable to handle kernel paging request at ffffffffffffffff) Rafael J. Wysocki
2008-04-22 20:57 ` Rafael J. Wysocki
2008-04-22 22:11 ` Greg KH
2008-04-22 20:58 ` Linus Torvalds
2008-04-22 22:12 ` Greg KH
2008-04-22 22:48 ` Rafael J. Wysocki
2008-04-23 0:50 ` Rafael J. Wysocki
2008-04-23 14:56 ` Alan Stern
2008-04-23 8:50 ` 2.6.25-git2: BUG: unable to handle kernel paging request at ffffffffffffffff Zdenek Kabelac
2008-04-23 15:53 ` Linus Torvalds
2008-04-23 16:58 ` Pekka Enberg
2008-04-23 17:28 ` Zdenek Kabelac
2008-04-23 17:40 ` Ingo Molnar
2008-04-23 18:52 ` Pekka Enberg
2008-04-23 19:05 ` Christoph Lameter
2008-04-23 19:19 ` Pekka J Enberg
2008-04-23 19:28 ` Christoph Lameter
2008-04-23 20:27 ` Zdenek Kabelac
2008-04-24 22:26 ` Jiri Slaby
2008-04-24 22:41 ` Linus Torvalds
2008-04-25 0:57 ` Jiri Slaby
2008-04-24 23:45 ` Linus Torvalds
2008-04-25 7:36 ` Jiri Slaby
2008-04-25 14:09 ` Pavel Machek
2008-04-25 15:30 ` Rafael J. Wysocki
2008-04-25 17:10 ` Jiri Slaby
2008-04-25 9:13 ` David Miller
2008-04-25 12:15 ` Zdenek Kabelac
2008-04-25 12:27 ` Zdenek Kabelac
2008-04-28 0:51 ` [PATCH 1/1] x86: fix text_poke Jiri Slaby
2008-04-25 15:03 ` Linus Torvalds
2008-04-25 15:17 ` Andi Kleen
2008-04-25 19:36 ` Christoph Lameter
2008-04-26 9:59 ` Andi Kleen
2008-04-26 11:16 ` Jiri Slaby
2008-04-26 11:34 ` Andi Kleen
2008-04-28 20:24 ` VIRTUAL_BUG_ON() Christoph Lameter
2008-05-01 19:22 ` [RFC 1/1] mm: add virt to phys debug Jiri Slaby
2008-05-01 20:18 ` Christoph Lameter
2008-05-06 21:54 ` Jiri Slaby
2008-05-07 17:30 ` Christoph Lameter
2008-05-13 14:38 ` Jiri Slaby
2008-04-25 15:19 ` [PATCH 1/1] x86: fix text_poke Ingo Molnar
2008-04-25 15:26 ` Ingo Molnar
2008-04-25 15:32 ` Ingo Molnar
2008-04-25 15:33 ` Linus Torvalds
2008-04-25 15:48 ` Andi Kleen
2008-04-25 16:06 ` Linus Torvalds
2008-04-25 16:19 ` Andi Kleen
2008-04-25 16:24 ` Linus Torvalds
2008-04-25 16:33 ` Ingo Molnar
2008-04-25 18:13 ` Jeremy Fitzhardinge
2008-05-05 2:36 ` Nick Piggin
2008-04-25 16:30 ` Mathieu Desnoyers
2008-04-25 16:42 ` H. Peter Anvin
2008-04-25 17:09 ` Mathieu Desnoyers
2008-04-25 18:37 ` Mathieu Desnoyers
2008-04-25 18:47 ` H. Peter Anvin
2008-04-25 19:19 ` H. Peter Anvin
2008-04-25 20:04 ` Mathieu Desnoyers
2008-04-25 20:09 ` H. Peter Anvin
2008-04-25 20:18 ` H. Peter Anvin
2008-04-25 20:37 ` Mathieu Desnoyers
2008-04-25 20:41 ` H. Peter Anvin
2008-04-25 20:51 ` Linus Torvalds
2008-04-25 21:12 ` Mathieu Desnoyers
2008-04-25 21:15 ` H. Peter Anvin
2008-04-25 21:47 ` Mathieu Desnoyers
2008-04-25 22:07 ` H. Peter Anvin
2008-04-25 22:30 ` Mathieu Desnoyers
2008-04-25 22:36 ` Linus Torvalds
2008-04-28 20:21 ` Ingo Molnar
2008-04-28 20:55 ` Jeremy Fitzhardinge
2008-04-28 21:01 ` H. Peter Anvin
2008-04-28 22:42 ` Mathieu Desnoyers
2008-04-28 20:43 ` Mathieu Desnoyers
2008-04-28 21:02 ` Jeremy Fitzhardinge
2008-05-04 15:03 ` Mathieu Desnoyers
2008-05-04 16:18 ` H. Peter Anvin
2008-04-25 22:38 ` H. Peter Anvin
2008-04-25 22:04 ` Linus Torvalds
2008-04-25 23:00 ` Mathieu Desnoyers
2008-04-25 23:13 ` Jeremy Fitzhardinge
2008-04-25 23:34 ` Masami Hiramatsu
2008-04-26 6:21 ` Jeremy Fitzhardinge
2008-04-26 11:56 ` Arnaldo Carvalho de Melo
2008-04-26 23:38 ` Jeremy Fitzhardinge
2008-04-27 1:00 ` Arnaldo Carvalho de Melo
2008-04-26 2:12 ` Frank Ch. Eigler
2008-06-05 17:44 ` Frank Ch. Eigler
2008-04-26 6:50 ` Jeremy Fitzhardinge
2008-04-28 0:49 ` Masami Hiramatsu
2008-04-25 21:02 ` David Miller
2008-04-25 21:11 ` H. Peter Anvin
2008-04-25 16:22 ` Ingo Molnar
2008-04-25 16:37 ` Linus Torvalds
2008-04-25 16:43 ` Ingo Molnar
2008-04-25 16:45 ` Ingo Molnar
2008-04-25 16:51 ` Linus Torvalds
2008-04-25 17:02 ` Ingo Molnar
2008-04-25 17:13 ` Linus Torvalds
2008-04-25 17:26 ` Andi Kleen
2008-04-25 17:29 ` Linus Torvalds
2008-04-25 17:53 ` Ingo Molnar
2008-04-25 18:04 ` Ingo Molnar
2008-04-25 18:09 ` Linus Torvalds
2008-04-25 18:19 ` Ingo Molnar
2008-04-25 18:56 ` Ingo Molnar
2008-04-25 18:13 ` Ingo Molnar
2008-04-25 16:52 ` Ingo Molnar
2008-04-25 16:56 ` Andi Kleen
2008-04-25 15:50 ` Ingo Molnar
2008-04-25 15:57 ` H. Peter Anvin
2008-04-25 18:53 ` Pavel Machek
2008-04-25 16:11 ` Linus Torvalds
2008-04-25 15:54 ` Mathieu Desnoyers
2008-04-25 15:59 ` Ingo Molnar
2008-04-25 16:11 ` Mathieu Desnoyers [this message]
2008-04-25 15:27 ` Andi Kleen
2008-04-25 20:18 ` David Miller
2008-04-25 1:35 ` 2.6.25-git2: BUG: unable to handle kernel paging request at ffffffffffffffff David Miller
2008-04-25 1:48 ` Linus Torvalds
2008-04-25 1:57 ` David Miller
2008-04-25 7:41 ` Jiri Slaby
2008-04-25 7:45 ` David Miller
2008-04-25 8:02 ` Jiri Slaby
2008-04-25 8:18 ` pci commands resume order [Was: 2.6.25-git2: BUG: unable to handle kernel paging request at ffffffffffffffff] Jiri Slaby
2008-04-25 17:11 ` Jesse Barnes
2008-04-25 10:53 ` 2.6.25-git2: BUG: unable to handle kernel paging request at ffffffffffffffff Craig Schlenter
2008-04-25 7:42 ` Jiri Slaby
2008-04-25 7:49 ` David Miller
2008-04-25 7:56 ` Jiri Slaby
2008-04-25 7:58 ` David Miller
2008-04-25 8:00 ` Jiri Slaby
2008-04-25 15:47 ` Randy Dunlap
2008-04-22 21:46 ` Rafael J. Wysocki
2008-04-22 19:09 ` Ingo Molnar
2008-04-22 1:15 ` Rafael J. Wysocki
2008-04-22 1:25 ` [ProbableSpam]Re: " Paul E. McKenney
2008-04-21 21:19 ` Linus Torvalds
2008-04-21 21:54 ` David Miller
2008-04-21 13:17 ` Ingo Molnar
2008-04-21 13:35 ` Rafael J. Wysocki
2008-04-21 18:56 ` Ingo Molnar
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