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Date: Wed, 10 Jan 2024 08:11:55 +1100
From: Stephen Rothwell <sfr@rothwell.id.au>
To: Lucas De Marchi <lucas.demarchi@intel.com>
Cc: "Paul E. McKenney" <paulmck@kernel.org>, Stephen Rothwell
 <sfr@canb.auug.org.au>, <lucas.dimarchi@intel.com>,
 <linux-kernel@vger.kernel.org>, <intel-xe@lists.freedesktop.org>
Subject: Re: [BUG] allmodconfig build error in next-20240108
Message-ID: <20240110081155.48bb0cbd@oak>
In-Reply-To: <atbx7mspjbymkzgstk4l64qz3uky3wpmx4isrfg3ixgtvebdd2@cktpe4ejfk7k>
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Hi Lucas,

On Tue, 9 Jan 2024 10:58:40 -0600 Lucas De Marchi <lucas.demarchi@intel.com=
> wrote:
>
> On Mon, Jan 08, 2024 at 03:15:23PM -0800, Paul E. McKenney wrote:
> >On Tue, Jan 09, 2024 at 09:57:57AM +1100, Stephen Rothwell wrote: =20
> >> Hi Paul,
> >>
> >> On Mon, 8 Jan 2024 13:33:36 -0800 "Paul E. McKenney" <paulmck@kernel.o=
rg> wrote: =20
> >> >
> >> > Recent -next trees get the following build error for allmodconfig bu=
ilds:
> >> >
> >> > --------------------------------------------------------------------=
----
> >> >
> >> > drivers/gpu/drm/xe/xe_gt_pagefault.c: In function =E2=80=98xe_guc_pa=
gefault_handler=E2=80=99:
> >> > ./include/linux/fortify-string.h:57:33: error: writing 16 bytes into=
 a region of =C2=A0size 0 [-Werror=3Dstringop-overflow=3D]
> >> > =C2=A0=C2=A0=C2=A057 | #define __underlying_memcpy =C2=A0 =C2=A0 __b=
uiltin_memcpy
> >> > =C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0| =C2=A0 =C2=A0 =C2=A0 =C2=A0 =
=C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=
=A0 =C2=A0 ^
> >> > ./include/linux/fortify-string.h:644:9: note: in expansion of macro =
=E2=80=98__underlying_memcpy=E2=80=99
> >> > =C2=A0=C2=A0644 | =C2=A0 =C2=A0 =C2=A0 =C2=A0 __underlying_##op(p, q=
, __fortify_size); \
> >> > =C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0| =C2=A0 =C2=A0 =C2=A0 =C2=A0 ^~=
~~~~~~~~~~~
> >> > ./include/linux/fortify-string.h:689:26: note: in expansion of macro=
 =E2=80=98__fortify_memcpy_chk=E2=80=99
> >> > =C2=A0=C2=A0689 | #define memcpy(p, q, s)=C2=A0 __fortify_memcpy_chk=
(p, q, s, \
> >> > =C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0|=C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=
=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 ^~~~~~~~~~~~~~~=
~~~~~
> >> > drivers/gpu/drm/xe/xe_gt_pagefault.c:340:17: note: in expansion of m=
acro =E2=80=98memcpy=E2=80=99
> >> > =C2=A0=C2=A0340 | =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =
=C2=A0 memcpy(pf_queue->data + pf_queue->tail, msg, len * sizeof(u32));
> >> > =C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0| =C2=A0 =C2=A0 =C2=A0 =C2=A0 =
=C2=A0 =C2=A0 =C2=A0 =C2=A0 ^~~~~~
> >> > In file included from drivers/gpu/drm/xe/xe_device_types.h:17,
> >> > =C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=
=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0from drivers/gpu/drm/xe/xe_vm_types.h:1=
6,
> >> > =C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=
=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0from drivers/gpu/drm/xe/xe_bo.h:13,
> >> > =C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=
=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0from drivers/gpu/drm/xe/xe_gt_pagefault=
c:16:
> >> > drivers/gpu/drm/xe/xe_gt_types.h:102:25: note: at offset [1144, 2653=
24] into destination object =E2=80=98tile=E2=80=99 of size 8
> >> > =C2=A0=C2=A0102 | =C2=A0 =C2=A0 =C2=A0 =C2=A0 struct xe_tile *tile;
> >> > =C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0| =20
> >>
> >> Which architecture?  What compiler and version?  Anything special in y=
our build
> >> setup?  I do x86_64 allmodconfig builds all day with gcc v13.2 and I d=
on't see
> >> this failure. =20
> >
> >Good point!
> >
> >I am using gcc version 11.3.1 20230605 (Red Hat 11.4.1-2) on x86_64.
> >I see the same behavior on gcc version 8.5.0, which for all I know might
> >be too old. =20
>=20
> I could reproduce it with allmodconfig and gcc 11.4.1 from rockylinux,
> but not with gcc 9.3 or 12.3. Also it's not reproduced with gcc 11.4.1
> when using defconfig + CONFIG_DRM_XE  (even if  -Wstringop-overflow is
> still added).
>=20
> I don't see a bug in the code, even if it inverts the head/tail
> convention.
>=20
> Searching around showed this which may be relevant: https://gcc.gnu.org/b=
ugzilla/show_bug.cgi?id=3D101854
> At least I can reproduce the same issue as in the snippet provided
> (https://gcc.gnu.org/bugzilla/show_bug.cgi?id=3D101854#c7) with the buggy
> compiler.
>=20
> So, maybe the best thing to do for now is to disable -Wstringop-overflow
> for gcc < 12?
>=20
>=20
> ------8<-----
> diff --git a/drivers/gpu/drm/xe/Makefile b/drivers/gpu/drm/xe/Makefile
> index 6952da8979ea..0433a3c6cbfd 100644
> --- a/drivers/gpu/drm/xe/Makefile
> +++ b/drivers/gpu/drm/xe/Makefile
> @@ -17,7 +17,7 @@ subdir-ccflags-y +=3D $(call cc-option, -Wunused-const-=
variable)
>   subdir-ccflags-y +=3D $(call cc-option, -Wpacked-not-aligned)
>   subdir-ccflags-y +=3D $(call cc-option, -Wformat-overflow)
>   subdir-ccflags-y +=3D $(call cc-option, -Wformat-truncation)
> -subdir-ccflags-y +=3D $(call cc-option, -Wstringop-overflow)
> +subdir-ccflags-$(call gcc-min-version, 120000) +=3D $(call cc-option, -W=
stringop-overflow)
>   subdir-ccflags-y +=3D $(call cc-option, -Wstringop-truncation)
>   # The following turn off the warnings enabled by -Wextra
>   ifeq ($(findstring 2, $(KBUILD_EXTRA_WARN)),)
> ------8<-----
>=20
> and if we are tweaking the warnings, then do similarly in scripts/Makefil=
e.extrawarn
> so it doesn't show up again with W=3D1 builds. Thoughts?

The top level Makefile (in linux-next) has:

#Currently, disable -Wstringop-overflow for GCC 11, globally.
KBUILD_CFLAGS-$(CONFIG_CC_NO_STRINGOP_OVERFLOW) +=3D $(call cc-option, -Wno=
-stringop-overflow)
KBUILD_CFLAGS-$(CONFIG_CC_STRINGOP_OVERFLOW) +=3D $(call cc-option, -Wstrin=
gop-overflow)

and init/Kconfig has:

# Currently, disable -Wstringop-overflow for GCC 11, globally.
config GCC11_NO_STRINGOP_OVERFLOW
        def_bool y

config CC_NO_STRINGOP_OVERFLOW
        bool
        default y if CC_IS_GCC && GCC_VERSION >=3D 110000 && GCC_VERSION < =
120000 && GCC11_NO_STRINGOP_OVERFLOW

config CC_STRINGOP_OVERFLOW
        bool
        default y if CC_IS_GCC && !CC_NO_STRINGOP_OVERFLOW

So, what does "grep -E '(STRINGOP_OVERFLOW|GCC_VERSION)' .config" show for =
your
breaking build(s)?

--=20
Cheers,
Stephen Rothwell

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