linux-kernel - Re: [tip:core/urgent] objtool: Fix __unreachable section relocation size

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Date:   Wed, 1 Mar 2017 11:37:12 +0100
From:   Ingo Molnar <mingo@...nel.org>
To:     linux-kernel@...r.kernel.org, tglx@...utronix.de,
        jpoimboe@...hat.com, a.p.zijlstra@...llo.nl,
        torvalds@...ux-foundation.org, peterz@...radead.org, hpa@...or.com
Cc:     linux-tip-commits@...r.kernel.org
Subject: Re: [tip:core/urgent] objtool: Fix __unreachable section relocation
 size

* tip-bot for Josh Poimboeuf <tipbot@...or.com> wrote:

> Commit-ID:  90a7e63a31b8f7d630d12ef0d8d37d3ab87f76e5
> Gitweb:     http://git.kernel.org/tip/90a7e63a31b8f7d630d12ef0d8d37d3ab87f76e5
> Author:     Josh Poimboeuf <jpoimboe@...hat.com>
> AuthorDate: Wed, 1 Mar 2017 00:05:04 -0600
> Committer:  Ingo Molnar <mingo@...nel.org>
> CommitDate: Wed, 1 Mar 2017 07:38:25 +0100
> 
> objtool: Fix __unreachable section relocation size
> 
> Linus reported the following commit broke module loading on his laptop:
> 
>   d1091c7fa3d5 ("objtool: Improve detection of BUG() and other dead ends")
> 
> It showed errors like the following:
> 
>   module: overflow in relocation type 10 val ffffffffc02afc81
>   module: 'nvme' likely not compiled with -mcmodel=kernel

BTW., beyond inadequate testing, another mistake I failed to notice during review 
is that the title of the patch was actively misleading: an "objtool: " prefix 
suggests a change that only affects objtool, while the changes here were to 
compiler-gcc.h, affecting pretty much everyone...

So a better, more informative commit title would have been:

   objtool, compiler.h: Improve detection of BUG() and other dead ends

... to at least warn people about the wider impact. (To be honest I personally 
probably would still not have noticed the bug, but maybe others.)

Along the same lines I'll fix the title of this fix patch as well, once a final 
version has been reached.

Thanks,

	Ingo