linux-kernel - Re: current objtool warnings from randconfig builds

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Date:   Tue, 7 Feb 2023 09:42:27 -0800
From:   Josh Poimboeuf <jpoimboe@...nel.org>
To:     Peter Zijlstra <peterz@...radead.org>
Cc:     Arnd Bergmann <arnd@...db.de>, linux-kernel@...r.kernel.org,
        llvm@...ts.linux.dev
Subject: Re: current objtool warnings from randconfig builds

On Tue, Feb 07, 2023 at 05:16:58PM +0100, Peter Zijlstra wrote:
> On Tue, Feb 07, 2023 at 11:25:27AM +0100, Arnd Bergmann wrote:
> > Hi Josh and Peter,
> > 
> > I've updated my randconfig test setup to use gcc-13 and clang-16, and
> > have sent fixes for all normal WERROR=y build warnings, but there are a
> > lot of objtool warnings that remain. I've reported some of them in
> > the past, some others are new. It would be nice to at least reduce
> > the number of warnings either through code changes or workarounds
> > in objtool for any false positives.
> > 
> > Out of 1500 builds, about a third had any warnings, this is the full
> > list sorted by frequency. Let me know if there are any that you haven't
> > seen before, I can provide the corresponding object and config files
> > for reproducing.
> > 
> >     Arnd
> > 
> > 8<---
> > 205 mm/kasan/shadow.o: warning: objtool: __asan_memset+0x2e: call to __memset() with UACCESS enabled
> > 205 mm/kasan/shadow.o: warning: objtool: __asan_memmove+0x48: call to __memmove() with UACCESS enabled
> > 205 mm/kasan/shadow.o: warning: objtool: __asan_memcpy+0x48: call to __memcpy() with UACCESS enabled
> 
> Patch pending here:
> 
>   https://git.kernel.org/pub/scm/linux/kernel/git/peterz/queue.git/commit/?h=sched/core-robot&id=79cdfdacd5b8d1ac77e24ccbc178bba0294d0d78
> 
> 
> > 80 vmlinux.o: warning: objtool: ibt_selftest+0x11: sibling call from callable instruction with modified stack frame
> 
> Can you provide details on how to reproduce this?

Arnd, thanks for rounding these up and posting them.

I agree we need to get these all cleaned up, but before we go too far
down the rabbit hole, is there some better way to track these?

Not that I would suggest using an external tracker, but maybe at least
put each set of related warnings (e.g., those having the same frequency)
in its own subthread with the config/compiler info included.

-- 
Josh