From: Sergey Senozhatsky <sergey.senozhatsky.work@gmail.com>
To: Helge Deller <deller@gmx.de>
Cc: Sergey Senozhatsky <sergey.senozhatsky.work@gmail.com>,
linux-kernel@vger.kernel.org,
Sergey Senozhatsky <sergey.senozhatsky@gmail.com>,
Petr Mladek <pmladek@suse.com>,
Andrew Morton <akpm@linux-foundation.org>,
Tony Luck <tony.luck@intel.com>,
Fenghua Yu <fenghua.yu@intel.com>,
Benjamin Herrenschmidt <benh@kernel.crashing.org>,
Paul Mackerras <paulus@samba.org>,
Michael Ellerman <mpe@ellerman.id.au>
Subject: Re: [PATCH 00/14] Fix wrong %pF and %pS printk format specifier usages
Date: Thu, 7 Sep 2017 18:36:31 +0900 [thread overview]
Message-ID: <20170907093631.GD533@jagdpanzerIV.localdomain> (raw)
In-Reply-To: <667b8849-fb60-a312-2483-505252ff737e@gmx.de>
(Cc Tony, Fenghua, Benjamin, Paul, Michael)
a brief description:
original patch set:
lkml.kernel.org/r/1504729681-3504-1-git-send-email-deller@gmx.de
start of this discussion:
lkml.kernel.org/r/20170907075653.GA533@jagdpanzerIV.localdomain
basically we are looking at possibilities to make %pF/%pS differences
less disturbing. Helge has discovered a number of wrong usages in the
kernel and has fixed the currently existing call sites; the question
is what we can do to avoid this type of the patch sets in the future?
/* assuming that no one reads printk documentation */
Hopefully you guys can help.
On (09/07/17 11:12), Helge Deller wrote:
[..]
> > - ptr = dereference_function_descriptor(ptr);
> > + ptr = __dereference_function_descriptor(ptr);
>
> This is not needed.
> All affected arches (ia64, ppc64, parisc64) already call
> probe_kernel_address() inside their dereference_function_descriptor() function.
> So this patch just adds unnecessary overhead for all arches.
good, thanks. honestly, I obviously didn't check what each platform
does. guilty! sort of.
> > ... here is a question, does function descriptor belong to a special
> > section? can we check that supplied ptr belongs to a descriptor section
> > and avoid dereference_function_descriptor() if it doesn't? (just fall
> > through directly to symbol_string() in this case). is this possible?
>
> I think theoretically yes.
> On parisc ptr does *not* point to any code segment, and most likely it
> points to the .data segment. I don't know if that's the case for ia64 and
> ppc64 too.
> I can look into adding such check-code, but even then the warning will
> only show up if you run on ia64, ppc64 and parisc64.
ok. personally I think that we need to start doing "does ptr belong to
descriptor segment/section/etc" thing and skip
dereference_function_descriptor() when it doesn't. [well, where possible.
hopefully on every affected platform... if this problem actually bothers
any one]. that seems like the way to fix the root cause of the problem.
because it's you, Petr and may be 7 more guys who knows the difference
between %pF/%pS. no one else has any idea at all. and no one actually
reads the printk() documentation, let's be real :)
-ss
next prev parent reply other threads:[~2017-09-07 9:39 UTC|newest]
Thread overview: 62+ messages / expand[flat|nested] mbox.gz Atom feed top
2017-09-06 20:27 [PATCH 00/14] Fix wrong %pF and %pS printk format specifier usages Helge Deller
2017-09-06 20:27 ` [PATCH 01/14] arm: Use %pS printk format for symbols from direct addresses Helge Deller
2017-09-06 20:27 ` [PATCH 02/14] um: " Helge Deller
2017-09-12 12:10 ` Petr Mladek
2017-09-21 20:13 ` Richard Weinberger
2017-09-06 20:27 ` [PATCH 03/14] x86: " Helge Deller
2017-09-06 20:27 ` [PATCH 04/14] ti_sci: Use %pS printk format for " Helge Deller
2017-09-08 23:30 ` Nishanth Menon
2017-09-09 0:30 ` Santosh Shilimkar
2017-09-06 20:27 ` [PATCH 05/14] i915: " Helge Deller
2017-09-27 12:24 ` [Intel-gfx] " Daniel Vetter
2017-09-06 20:27 ` [PATCH 06/14] md/bcache: " Helge Deller
2017-09-07 4:50 ` Coly Li
2017-09-07 7:42 ` Helge Deller
2017-09-07 7:49 ` Coly Li
2017-09-07 8:05 ` Sergey Senozhatsky
2017-09-06 20:27 ` [PATCH 07/14] power/avs: " Helge Deller
2017-09-08 23:37 ` Nishanth Menon
2017-09-06 20:27 ` [PATCH 08/14] fs/f2fs: " Helge Deller
2017-09-06 20:27 ` [PATCH 09/14] fs/pstore: " Helge Deller
2018-11-29 23:26 ` Kees Cook
2018-11-29 23:49 ` Luck, Tony
2018-11-30 0:40 ` Kees Cook
2017-09-06 20:27 ` [PATCH 10/14] fs/xfs: " Helge Deller
2017-09-08 7:38 ` Christoph Hellwig
2017-09-18 18:37 ` Darrick J. Wong
2017-09-06 20:27 ` [PATCH 11/14] smp: Use %pF printk format specifier for function pointers Helge Deller
2017-09-06 20:27 ` [PATCH 12/14] mm/memblock: Use %pS printk format for direct addresses Helge Deller
2017-09-06 20:28 ` [PATCH 13/14] netfilter/ipvs: " Helge Deller
2017-10-09 5:52 ` Simon Horman
2017-11-06 13:46 ` Pablo Neira Ayuso
2017-09-06 20:28 ` [PATCH 14/14] sound/core: " Helge Deller
2017-09-07 8:36 ` Takashi Iwai
2017-09-07 0:45 ` [PATCH 00/14] Fix wrong %pF and %pS printk format specifier usages Sergey Senozhatsky
2017-09-07 6:01 ` Helge Deller
2017-09-07 7:56 ` Sergey Senozhatsky
2017-09-07 8:32 ` Sergey Senozhatsky
2017-09-07 9:12 ` Helge Deller
2017-09-07 9:36 ` Sergey Senozhatsky [this message]
2017-09-07 9:51 ` Sergey Senozhatsky
2017-09-07 12:38 ` Helge Deller
2017-09-07 16:05 ` Luck, Tony
2017-09-08 6:18 ` Sergey Senozhatsky
2017-09-08 17:25 ` Luck, Tony
2017-09-08 18:28 ` Helge Deller
2017-09-14 7:40 ` Sergey Senozhatsky
2017-09-14 8:03 ` Sergey Senozhatsky
2017-09-14 8:39 ` Helge Deller
2017-09-14 9:27 ` Sergey Senozhatsky
2017-09-14 9:47 ` Helge Deller
2017-09-14 16:01 ` Luck, Tony
2017-09-18 7:03 ` Sergey Senozhatsky
2017-09-14 6:53 ` Sergey Senozhatsky
2017-09-08 20:49 ` Helge Deller
2017-09-12 11:18 ` Petr Mladek
2017-09-14 6:44 ` Sergey Senozhatsky
2017-09-08 22:23 ` Yu, Fenghua
2017-09-14 6:35 ` Sergey Senozhatsky
2017-09-07 16:50 ` Joe Perches
2017-09-08 6:23 ` Sergey Senozhatsky
2017-09-08 20:39 ` Helge Deller
2017-09-12 12:23 ` Petr Mladek
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