linux-kernel - Re: linux-next: Tree for Aug 20 (Wno-alloc-size-larger-than)

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Message-ID: <20210823203742.5169ad54@canb.auug.org.au>
Date:   Mon, 23 Aug 2021 20:37:42 +1000
From:   Stephen Rothwell <sfr@...b.auug.org.au>
To:     Randy Dunlap <rdunlap@...radead.org>
Cc:     Kees Cook <keescook@...omium.org>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Linux Next Mailing List <linux-next@...r.kernel.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        Nathan Chancellor <nathan@...nel.org>
Subject: Re: linux-next: Tree for Aug 20 (Wno-alloc-size-larger-than)

Hi all,

On Sat, 21 Aug 2021 12:09:48 -0700 Randy Dunlap <rdunlap@...radead.org> wrote:
>
> On 8/20/21 10:48 PM, Kees Cook wrote:
> > On Fri, Aug 20, 2021 at 02:54:05PM -0700, Randy Dunlap wrote:  
> >> On 8/20/21 2:26 AM, Stephen Rothwell wrote:  
> >>> Hi all,
> >>>
> >>> Changes since 20210819:
> >>>  
> >>
> >> Both linux-next and mmotm have many of these warnings when using
> >> gcc (SUSE Linux) 7.5.0:
> >>
> >> cc1: warning: unrecognized command line option '-Wno-alloc-size-larger-than'  
> > 
> > Ew. Thanks for letting me know. I thought I'd verified this existed in
> > gcc going back to 4.9, but it looks like I did something wrong in that
> > test.
> > 
> > I think this should fix it:
> > 
> > diff --git a/Makefile b/Makefile
> > index b0fafc41b686..e33ffa05899e 100644
> > --- a/Makefile
> > +++ b/Makefile
> > @@ -1097,7 +1097,7 @@ endif
> >   ifdef CONFIG_CC_IS_GCC
> >   # The allocators already balk at large sizes, so silence the compiler
> >   # warnings for bounds checks involving those possible values.
> > -KBUILD_CFLAGS += -Wno-alloc-size-larger-than
> > +KBUILD_CFLAGS += $(call cc-option, -Wno-alloc-size-larger-than)
> >   endif  
> >   >   # disable invalid "can't wrap" optimizations for signed / pointers  
> >   
> 
> Well. That didn't help. This is very weird.
> 
> This -Wno... option works (is accepted, no warning) on most files
> that are being built, but a few files report an error with it:
> 
> ../drivers/gpu/drm/radeon/radeon_object.c: At top level:
> cc1: warning: unrecognized command line option '-Wno-alloc-size-larger-than'
> 
> ../drivers/gpu/drm/amd/amdgpu/amdgpu_object.c: At top level:
> cc1: warning: unrecognized command line option '-Wno-alloc-size-larger-than'
> 
> ../drivers/hwmon/dell-smm-hwmon.c: At top level:
> cc1: warning: unrecognized command line option '-Wno-alloc-size-larger-than'
> 
>    CC      arch/x86/kernel/cpu/proc.o
> cc1: warning: unrecognized command line option '-Wno-alloc-size-larger-than'
> 
> ../arch/x86/kvm/mmu/mmu.c: At top level:
> cc1: error: unrecognized command line option '-Wno-alloc-size-larger-than' [-Werror]
> 
> ../drivers/gpu/drm/amd/amdgpu/../amdkfd/kfd_chardev.c: At top level:
> cc1: warning: unrecognized command line option '-Wno-alloc-size-larger-than'
> 
> ../kernel/trace/trace_osnoise.c: At top level:
> cc1: warning: unrecognized command line option '-Wno-alloc-size-larger-than'
> 
>    CC      kernel/dma/mapping.o
> cc1: warning: unrecognized command line option '-Wno-alloc-size-larger-than'
> 
> 
> It seems like it might be related to some .config option.
> 
> I did a couple of partial builds with V=1 but that info didn't help me any.
> 
> 
> If I am the only person seeing (reporting) this build warning, it could
> just be (another) SUSE GCC-ism. (had one just last week with  -Wmain and
> kernel/trace/trace_osnoise.c)

Today, I am also seeing thsese, but only with my sparc{,64} defconfig
cross builds.  This is with gcc 7.3.1 built from sources.  I also just
get a few of them.

Also, I have the above "fix" patch applied (Andrew added it to mmots
today).

So something weird is happening.
-- 
Cheers,
Stephen Rothwell

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