linux-kernel - Re: [PATCH] x86/kbuild: enable modversions for symbols exported from asm

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Date:   Thu, 24 Nov 2016 10:25:05 +0100
From:   Michal Marek <mmarek@...e.com>
To:     Ingo Molnar <mingo@...nel.org>, Adam Borowski <kilobyte@...band.pl>
Cc:     Philip Muller <philm@...jaro.org>, linux-kernel@...r.kernel.org,
        Nicholas Piggin <npiggin@...il.com>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...hat.com>,
        "H. Peter Anvin" <hpa@...or.com>,
        Linus Torvalds <torvalds@...ux-foundation.org>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Peter Zijlstra <a.p.zijlstra@...llo.nl>
Subject: Re: [PATCH] x86/kbuild: enable modversions for symbols exported from
 asm

On 2016-11-24 05:40, Ingo Molnar wrote:
> 
> * Adam Borowski <kilobyte@...band.pl> wrote:
> 
>> Commit 4efca4ed ("kbuild: modversions for EXPORT_SYMBOL() for asm") adds
>> modversion support for symbols exported from asm files. Architectures
>> must include C-style declarations for those symbols in asm/asm-prototypes.h
>> in order for them to be versioned.
>>
>> Add these declarations for x86, and an architecture-independent file that
>> can be used for common symbols.
>>
>> User impact: kernels may fail to load modules at all when
>> CONFIG_MODVERSIONS=y.
>>
>> Signed-off-by: Adam Borowski <kilobyte@...band.pl>
>> Tested-by: Kalle Valo <kvalo@...eaurora.org>
>> Acked-by: Nicholas Piggin <npiggin@...il.com>
>> Tested-by: Peter Wu <peter@...ensteyn.nl>
>> Tested-by: Oliver Hartkopp <socketcan@...tkopp.net>
>> ---
>> Changes: corrected Peter Wu's address, added Tested-by: Oliver.
>> This is an unsplit version (x86/include/ and include/ together).
>>
>>  arch/x86/include/asm/asm-prototypes.h | 12 ++++++++++++
>>  include/asm-generic/asm-prototypes.h  |  7 +++++++
>>  2 files changed, 19 insertions(+)
>>  create mode 100644 arch/x86/include/asm/asm-prototypes.h
>>  create mode 100644 include/asm-generic/asm-prototypes.h
> 
> Michal, I'm quite unhappy about how the offending commit that broke modversions 
> for essentially _everyone_ who does more complex modular builds on x86 ended up 
> upstream:
> 
>   commit 4efca4ed05cbdfd13ec3e8cb623fb77d6e4ab187
>   Author:     Nicholas Piggin <npiggin@...il.com>
>   AuthorDate: Tue Nov 1 12:46:19 2016 +1100
>   Commit:     Michal Marek <mmarek@...e.com>
>   CommitDate: Tue Nov 1 16:20:17 2016 +0100
> 
>       kbuild: modversions for EXPORT_SYMBOL() for asm
> 
>       Allow architectures to create asm/asm-prototypes.h file that
>       provides C prototypes for exported asm functions, which enables
>       proper CRC versions to be generated for them.
> 
>  scripts/Makefile.build | 78 ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++------
>  1 file changed, 72 insertions(+), 6 deletions(-)
> 
> It was applied 4 hours after it was sent in the -rc3 timeframe, and then it went 
> upstream in -rc5:
> 
>      "Here are some regression fixes for kbuild:
>     
>        - modversion support for exported asm symbols (Nick Piggin). The
>          affected architectures need separate patches adding
>          asm-prototypes.h.
> 
> ... the fine merge log even says that the commit 'needs separate patches'!

It needs separate patches to finally fix the regression that happened in
-rc1.

Michal