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

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Message-ID: <8b9cb816-9d8a-2633-1afa-f5c4597a8314@infradead.org>
Date:   Sat, 21 Aug 2021 12:09:48 -0700
From:   Randy Dunlap <rdunlap@...radead.org>
To:     Kees Cook <keescook@...omium.org>,
        Andrew Morton <akpm@...ux-foundation.org>
Cc:     Stephen Rothwell <sfr@...b.auug.org.au>,
        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)

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)


-- 
~Randy