From: Arnd Bergmann <arnd@arndb.de>
To: Ben Hutchings <ben@decadent.org.uk>
Cc: Linus Torvalds <torvalds@linux-foundation.org>,
Adam Borowski <kilobyte@angband.pl>,
Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
Linux Kbuild mailing list <linux-kbuild@vger.kernel.org>,
Michal Marek <mmarek@suse.com>,
Debian kernel maintainers <debian-kernel@lists.debian.org>,
"linux-arch@vger.kernel.org" <linux-arch@vger.kernel.org>,
Ingo Molnar <mingo@kernel.org>,
Nicholas Piggin <npiggin@gmail.com>,
Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
Alan Modra <amodra@gmail.com>
Subject: Re: [RFC, PATCH, v3.9] default exported asm symbols to zero
Date: Sat, 03 Dec 2016 11:43:07 +0100 [thread overview]
Message-ID: <55460922.iQ4WX6OtHo@wuerfel> (raw)
In-Reply-To: <1480739797.16599.118.camel@decadent.org.uk>
On Saturday, December 3, 2016 4:36:37 AM CET Ben Hutchings wrote:
> On Fri, 2016-12-02 at 13:40 +0100, Arnd Bergmann wrote:
> > With binutils-2.16 and before, a weak missing symbol was kept during the
> > final link, and a missing CRC for an export would lead to that CRC
> > being treated as zero implicitly. With binutils-2.17, the crc
> > symbol gets dropped, and any module trying to use it will fail to
> > load.
> >
> > This sets the weak CRC symbol to zero explicitly, making it defined
> > in vmlinux, which in turn lets us load the modules referring to
> > that CRC.
> >
> > The comment above the __CRC_SYMBOL macro suggests that this was
> > always the intention, although it also seems that all symbols
> > defined in C have a correct CRC these days, and only the exports
> > that are now done in assembly need this.
> >
> > > Signed-off-by: Arnd Bergmann <arnd@arndb.de>
> > ---
> > Not sure if this is the correct way of doing it, but this seems trivial
> > enough and lets me build the kernel with missing CRCs with any binutils
> > version.
>
> I tried this along with Adam's patch on x86_64, with Debian's binutils
> 2.27.51.20161127. The result was that the kernel's __kcrctab held 0
> for several symbols, even though there was type information in asm-
> prototypes.h and Module.symvers and the modules had a non-zero CRC for
> those symbols. With just Adam's patch, the kernel and modules agreed.
Can you be more specific? Which symbols are those? I would have expected
modpost to generate Module.symvers from the vmlinux file, so I wonder
where that difference comes from.
Arnd
next prev parent reply other threads:[~2016-12-03 10:44 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
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 [this message]
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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