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

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Date:   Thu, 1 Dec 2016 22:09:07 +1100
From:   Nicholas Piggin <npiggin@...il.com>
To:     Stanislav Kozina <skozina@...hat.com>
Cc:     Don Zickus <dzickus@...hat.com>,
        Linus Torvalds <torvalds@...ux-foundation.org>,
        Ben Hutchings <ben@...adent.org.uk>,
        Michal Marek <mmarek@...e.com>,
        Adam Borowski <kilobyte@...band.pl>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Linux Kbuild mailing list <linux-kbuild@...r.kernel.org>,
        Debian kernel maintainers <debian-kernel@...ts.debian.org>,
        "linux-arch@...r.kernel.org" <linux-arch@...r.kernel.org>,
        Arnd Bergmann <arnd@...db.de>, Ingo Molnar <mingo@...nel.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] x86/kbuild: enable modversions for symbols exported
 from asm

On Thu, 1 Dec 2016 11:48:09 +0100
Stanislav Kozina <skozina@...hat.com> wrote:

> On 12/01/2016 05:13 AM, Don Zickus wrote:
> 
> ...
> 
> > I think GregKH pointed to one such tool, libabigail?  We are working on
> > others too.  
> 
> I should mention one of the others here:
> https://github.com/skozina/kabi-dw
> 
> It's quite comparable to libabigail in the way it works, the main 
> differences are:
>   - written in pure C
>   - depends only on elf-utils and flex/yacc
>   - it's much simpler (4k LOC)
>   - stores the type information in the text files and compares those 
> instead of directly comparing two sets of DWARF data

Now this seems much better for distro ABI checking.

The next question is, do they need any kernel support for rare cases
where they do have to break the ABI of an export? Simple rename of the
function with a _v2 postfix might be enough. We could retain some per
symbol versioning in the kernel if needed, but how much would it
actually help?

Thanks,
Nick