linux-kernel - Re: objtool warning breaks build for fs/dlm/lock.o

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Message-ID: <CAK8P3a0pY+tu=3hvWTZVwD7nbA7UhaaCGWbBVba0eDuNcpt2Sg@mail.gmail.com>
Date:   Fri, 8 May 2020 11:27:39 +0200
From:   Arnd Bergmann <arnd@...db.de>
To:     Josh Poimboeuf <jpoimboe@...hat.com>
Cc:     Peter Zijlstra <peterz@...radead.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: Re: objtool warning breaks build for fs/dlm/lock.o

On Fri, May 8, 2020 at 1:29 AM Josh Poimboeuf <jpoimboe@...hat.com> wrote:
>
> On Wed, May 06, 2020 at 04:07:25PM +0200, Arnd Bergmann wrote:
> > Hi,
> >
> > During randconfig testing with clang-10 I came across a number
> > of additional objtool warnings, I'll send another mail about those
> > when I have collected more information and some object files.
> >
> > This one sticks out however, as objtool returns an error code that
> > stops the build:
>
> > fs/dlm/lock.o: warning: objtool: __receive_convert_reply()+0x1e5: can't find jump dest instruction at .text+0xcaa7
>
> Thanks for sending the patch for this one.  Objtool always gets confused
> by new compiler versions, I really think we need to revert
>
>   644592d32837 ("objtool: Fail the kernel build on fatal errors")
>
> because objtool is never going to be reliable enough such that we can be
> confident that failing the build is the right thing to do.

Right, makes sense. It would be nice though to have a way of intentionally
turning all objtool warnings into errors. I do my randconfig tests
with '-Werror'
at the moment in order to catch all new warnings, but this does not catch
objtool errors at the moment. For now, this is probably the right thing to do,
as there are a couple of warnings that I have no patches for, but at some point
I would prefer to trap immediately when a new warning pops up.

     Arnd