From: Michal Marek <mmarek@suse.com>
To: Nicholas Piggin <npiggin@gmail.com>, Ben Hutchings <ben@decadent.org.uk>
Cc: Linus Torvalds <torvalds@linux-foundation.org>,
linux-arch@vger.kernel.org, linux-kbuild@vger.kernel.org,
linux-kernel@vger.kernel.org,
Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
Arnd Bergmann <arnd@arndb.de>, Ingo Molnar <mingo@kernel.org>,
Adam Borowski <kilobyte@angband.pl>,
Debian kernel maintainers <debian-kernel@lists.debian.org>
Subject: Re: [PATCH] x86/kbuild: enable modversions for symbols exported from asm
Date: Tue, 29 Nov 2016 10:14:08 +0100 [thread overview]
Message-ID: <89fa3c90-dad3-b4f4-a343-6264f2d7b220@suse.com> (raw)
In-Reply-To: <20161129133130.164b4e2d@roar.ozlabs.ibm.com>
Dne 29.11.2016 v 03:31 Nicholas Piggin napsal(a):
> On Tue, 29 Nov 2016 01:15:48 +0000
> Ben Hutchings <ben@decadent.org.uk> wrote:
>
>> [I've had to guess at the cc list for this, because we no longer have
>> mail archives that preserve them.]
>
> You got it about right.
>
>> On Fri, 2016-11-25 at 10:01 -0800, Linus Torvalds wrote:
>>> On Thu, Nov 24, 2016 at 4:40 PM, Nicholas Piggin <npiggin@gmail.com> wrote:
>>>>>
>>>>> Yes, manual "marking" is never going to be a viable solution.
>>>>
>>>> I guess it really depends on how exactly you want to use it. For distros
>>>> that do stable ABI but rarely may have to break something for security
>>>> reasons, it should work and give exact control.
>>
>> This is roughly how Debian handles the kernel module ABI during a
>> stable release.
>>
>>> No. Because nobody else will care, so unless it's like a single symbol
>>> or something, it will just be a maintenance nightmare.
>>
>> I agree with this. We can explicitly "version" individual symbols
>> anyway by doing something like:
>>
>> -int foo(void);
>> +#define foo foo_2
>> +int foo_2(int);
>
> Yeah... Benefit being it's very simple and everybody can see exactly
> what it does and knows how it will work.
>
>>
>>>> What else do people *actually* use it for? Preventing mismatched modules
>>>> when .git version is not attached and release version of the kernel has
>>>> not been bumped. Is that it?
>>>
>>> It used to be very useful for avoiding loading stale modules and then
>>> wasting days on debugging something that wasn't the case when you had
>>> forgotten to do "make modules_install". Change some subtle internal
>>> ABI issue (add/remove a parameter, whatever) and it would really help.
>>>
>>> These days, for me, LOCALVERSION_AUTO and module signing are what I
>>> personally tend to use.
>>>
>>> The modversions stuff may just be too painful to bother with. Very few
>>> people probably use it, and the ones that do likely don't have any
>>> overriding reason why.
>> [...]
>>
>> Debian has some strong reasons:
I guess many distros have similar reasons.
>> 1. Changing the release string requires any out-of-tree modules to be
>> upgraded (at least rebuilt) on end-user systems. So we try to avoid
>> doing that during the lifetime of a stable release, i.e. we don't let
>> the release string change. Also, the release string is reflected in
>> package names (e.g. linux-image-4.8.0-1-amd64), and introducing new
>> package names requires manual approval by the Debian archive team.
>
> This is something I've noticed. Would it be better if the module loader
> ignores the kernel version and instead used some internal ABI version
> string to check against? Otherwise (AFAICT) you always have 4.8.0 versions
> despite being 4.8.7 kernel, and you can't upgrade a point release without
> overwriting your old kernel and modules.
The thing is - to maintain an ABI version string, you need some level of
certainty that two given ABIs are really interchangeable. Which means
you need to check whether the symbols _and_ types exposed are unchanged.
Which is a thing that genksyms, the tool behind CONFIG_MODVERSIONS, does
quite well. So yes, you could do a testbuild with CONFIG_MODVERSIONS=y
and a production build with some global ABI string, but what's the point
then.
> It would be nice to get upstream to the point where 4.9 modversions
> works if you just patch out depends BROKEN. That would require reverting
> a few more of Al's arch patches.
>
> Then in 4.10 we can re-add all those arch patches (which are less
> controversial without the asm-prototypes.h workaround), and implement a
> simple stable ABI version string check, and then in 4.11 we can remove
> modversions.
I'd rather change the kconfig to
depends on BROKEN || <archs that have asm/asm-prototypes.h>
and eventuallly remove the dependency again. PPC has the header already,
so it can be added right away. I do not know why the x86 patch has not
been merged yet.
Michal
next prev parent reply other threads:[~2016-11-29 9:14 UTC|newest]
Thread overview: 113+ messages / expand[flat|nested] mbox.gz Atom feed top
[not found] <a73aec83-ddad-2bdf-e612-178c9936a16f@manjaro.org>
[not found] ` <20161102004639.6870806d@roar.ozlabs.ibm.com>
2016-11-23 20:08 ` BUG: 4.9-rc6 Still "no symbol version" on boot Philip Müller
2016-11-23 20:14 ` Robert LeBlanc
2016-11-23 20:27 ` Philip Müller
2016-11-23 20:53 ` Adam Borowski
2016-11-23 21:01 ` Robert LeBlanc
2016-11-23 21:02 ` [PATCH] x86/kbuild: enable modversions for symbols exported from asm Adam Borowski
2016-11-23 23:10 ` Philip Müller
2016-11-24 4:40 ` Ingo Molnar
2016-11-24 5:20 ` Nicholas Piggin
2016-11-24 6:00 ` Ingo Molnar
2016-11-24 7:20 ` Nicholas Piggin
2016-11-24 7:36 ` Greg Kroah-Hartman
2016-11-24 7:53 ` Nicholas Piggin
2016-11-24 9:32 ` Michal Marek
2016-11-24 10:03 ` Nicholas Piggin
2016-11-24 10:51 ` Michal Marek
2016-11-24 9:38 ` Arnd Bergmann
2016-11-24 10:01 ` Nicholas Piggin
2016-11-24 9:56 ` Greg Kroah-Hartman
2016-11-24 10:31 ` Nicholas Piggin
2016-11-24 15:24 ` Greg Kroah-Hartman
2016-11-25 0:40 ` Nicholas Piggin
2016-11-25 18:00 ` Linus Torvalds
2016-11-26 0:37 ` Nicholas Piggin
2016-11-29 1:15 ` Ben Hutchings
2016-11-29 2:31 ` Nicholas Piggin
2016-11-29 9:14 ` Michal Marek [this message]
2016-11-29 4:08 ` Linus Torvalds
2016-11-29 13:19 ` Adam Borowski
2016-11-29 13:29 ` Ingo Molnar
2016-11-29 14:24 ` Adam Borowski
2016-11-29 13:51 ` Adam Borowski
[not found] ` <CA+55aFyZiB4YkwvqzrXO=HD8bcnc2xHkAYrek2QHVnhVvAi3Fw@mail.gmail.com>
2016-11-29 16:03 ` Michal Marek
2016-11-29 16:17 ` Linus Torvalds
2016-11-29 19:57 ` Ben Hutchings
2016-11-29 20:35 ` Linus Torvalds
2016-11-30 18:18 ` Nicholas Piggin
2016-11-30 18:40 ` Linus Torvalds
2016-11-30 21:33 ` Ben Hutchings
2016-12-01 1:55 ` Nicholas Piggin
2016-12-01 2:35 ` Ben Hutchings
2016-12-01 3:39 ` Nicholas Piggin
2016-12-01 16:12 ` Michal Marek
2016-12-02 14:36 ` Hannes Frederic Sowa
2016-12-09 3:33 ` Nicholas Piggin
2016-12-09 15:21 ` Ian Campbell
2016-12-09 16:15 ` Nicholas Piggin
2016-12-09 22:46 ` Dodji Seketeli
2016-12-10 12:41 ` Greg Kroah-Hartman
2016-12-12 3:50 ` Nicholas Piggin
2016-12-12 9:08 ` Ian Campbell
2016-12-14 17:59 ` Don Zickus
2016-12-13 1:07 ` Stanislav Kozina
2016-12-13 22:51 ` Michal Marek
2016-12-14 8:58 ` Dodji Seketeli
2016-12-14 9:15 ` Michal Marek
2016-12-14 9:36 ` Dodji Seketeli
2016-12-14 9:44 ` Michal Marek
2016-12-14 10:02 ` Dodji Seketeli
2016-12-14 10:15 ` Michal Marek
2016-12-14 9:56 ` Dodji Seketeli
2016-12-14 9:37 ` Michal Marek
2016-12-01 4:13 ` Don Zickus
2016-12-01 4:32 ` Nicholas Piggin
2016-12-01 15:20 ` Don Zickus
2016-12-01 15:26 ` Christoph Hellwig
2016-12-01 15:40 ` Don Zickus
2016-12-01 16:06 ` Greg Kroah-Hartman
2016-12-01 18:42 ` Don Zickus
2016-12-09 3:50 ` Nicholas Piggin
2016-12-09 7:55 ` Stanislav Kozina
2016-12-09 8:14 ` Nicholas Piggin
2016-12-09 14:36 ` Stanislav Kozina
2016-12-09 15:56 ` Nicholas Piggin
2016-12-09 16:03 ` Greg Kroah-Hartman
2016-12-12 9:48 ` Stanislav Kozina
2016-12-13 7:25 ` Nicholas Piggin
2016-12-14 14:04 ` Hannes Frederic Sowa
2016-12-15 2:06 ` Nicholas Piggin
2016-12-15 11:19 ` Hannes Frederic Sowa
2016-12-15 12:03 ` Nicholas Piggin
2016-12-15 13:15 ` Hannes Frederic Sowa
2016-12-15 14:15 ` Nicholas Piggin
2016-12-15 15:17 ` Hannes Frederic Sowa
2016-12-15 13:35 ` Stanislav Kozina
2016-12-09 16:16 ` Don Zickus
2016-12-01 10:48 ` Stanislav Kozina
2016-12-01 11:09 ` Nicholas Piggin
2016-12-01 11:33 ` Stanislav Kozina
2016-12-01 12:39 ` Nicholas Piggin
2016-12-01 15:19 ` Dodji Seketeli
2016-12-01 16:14 ` Michal Marek
2016-11-29 17:05 ` Adam Borowski
2016-11-29 17:10 ` Linus Torvalds
2016-11-29 17:14 ` Linus Torvalds
2016-12-01 13:58 ` Arnd Bergmann
2016-12-01 16:21 ` Michal Marek
2016-12-01 18:26 ` Linus Torvalds
2016-12-02 10:55 ` Arnd Bergmann
2016-12-02 12:40 ` [RFC, PATCH, v3.9] default exported asm symbols to zero Arnd Bergmann
2016-12-02 12:59 ` Geert Uytterhoeven
2016-12-02 14:51 ` Arnd Bergmann
2016-12-02 15:35 ` Adam Borowski
2016-12-03 4:36 ` Ben Hutchings
2016-12-03 10:43 ` Arnd Bergmann
2016-12-02 17:04 ` [PATCH] x86/kbuild: enable modversions for symbols exported from asm Linus Torvalds
2016-12-04 7:44 ` Alan Modra
2016-12-04 20:44 ` Linus Torvalds
2016-11-29 21:23 ` Michal Marek
2016-11-24 9:25 ` Michal Marek
2016-11-24 11:42 ` Regression: " Kalle Valo
2016-11-23 23:07 ` BUG: 4.9-rc6 Still "no symbol version" on boot Philip Müller
2016-11-28 17:10 ` Robert LeBlanc
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