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

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Date:   Thu, 24 Nov 2016 07:00:50 +0100
From:   Ingo Molnar <mingo@...nel.org>
To:     Nicholas Piggin <npiggin@...il.com>,
        Al Viro <viro@...iv.linux.org.uk>
Cc:     Adam Borowski <kilobyte@...band.pl>,
        Michal Marek <mmarek@...e.com>,
        Philip Muller <philm@...jaro.org>,
        linux-kernel@...r.kernel.org,
        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>,
        linux-arch <linux-arch@...r.kernel.org>
Subject: Re: [PATCH] x86/kbuild: enable modversions for symbols exported from
 asm


* Nicholas Piggin <npiggin@...il.com> wrote:

> >  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's still totally broken upstream and it didn't fix any regressions AFAICS (or if 
> > it did then its changelog was very silent on that fact).
> 
> Well it doesn't fix regression by itself, as discussed it needs architecture
> patches. I've tried keeping linux-arch on cc for all this modversion breakage
> stuff since it became clear it would require arch changes.
> 
> The actual x86 bug I suppose you would say is caused by 784d5699eddc5. But I
> should probably have included more background in the above initial crc support
> patch, e.g, at least reference 22823ab419d. So mea culpa for that.

Indeed 784d5699eddc5 makes more sense:

  784d5699eddc ("x86: move exports to actual definitions")
  22823ab419d8 ("EXPORT_SYMBOL() for asm")

... and sorry about coming down on you and Marek!

I've Cc:-ed Al.

I think what happened is that 22823ab419d8 and 784d5699eddc caused the boot 
regression (modular builds with modversions enabled not booting), and your fix 
half-fixed it - with the remaining fix (that adds the header to x86) fixing the 
rest.

Still the fact remains that modversions was broken in -rc1 which delayed testing 
done by a number of prominent testers. :-(

Thanks,

	Ingo