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Date:   Wed, 15 Jun 2022 10:45:29 -0700
From:   Kees Cook <keescook@chromium.org>
To:     Daniel Latypov <dlatypov@google.com>
Cc:     kernel test robot <lkp@intel.com>, kbuild-all@lists.01.org,
        linux-kernel@vger.kernel.org,
        Vitor Massaru Iha <vitor@massaru.org>,
        David Gow <davidgow@google.com>
Subject: Re: lib/overflow_kunit.c:644:1: warning: the frame size of 2832
 bytes is larger than 1024 bytes
Message-ID: <202206151045.36F7623B@keescook>
References: <202206120046.YKeKzlVN-lkp@intel.com>
 <CAGS_qxquSGoHD2NeRiS-basVg-nOP8s4kSGi90e2QuMc-Pt0Pg@mail.gmail.com>
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On Mon, Jun 13, 2022 at 10:55:02AM -0700, Daniel Latypov wrote:
> On Sat, Jun 11, 2022 at 9:44 AM kernel test robot <lkp@intel.com> wrote:
> >
> > Hi Kees,
> >
> > First bad commit (maybe != root cause):
> >
> > tree:   https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git master
> > head:   0885eacdc81f920c3e0554d5615e69a66504a28d
> > commit: 617f55e20743fc50c989b498f9dee289eb644cfd lib: overflow: Convert to Kunit
> > date:   3 months ago
> > config: powerpc-buildonly-randconfig-r006-20220611 (https://download.01.org/0day-ci/archive/20220612/202206120046.YKeKzlVN-lkp@intel.com/config)
> > compiler: powerpc-linux-gcc (GCC) 11.3.0
> > reproduce (this is a W=1 build):
> >         wget https://raw.githubusercontent.com/intel/lkp-tests/master/sbin/make.cross -O ~/bin/make.cross
> >         chmod +x ~/bin/make.cross
> >         # https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=617f55e20743fc50c989b498f9dee289eb644cfd
> >         git remote add linus https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git
> >         git fetch --no-tags linus master
> >         git checkout 617f55e20743fc50c989b498f9dee289eb644cfd
> >         # save the config file
> >         mkdir build_dir && cp config build_dir/.config
> >         COMPILER_INSTALL_PATH=$HOME/0day COMPILER=gcc-11.3.0 make.cross W=1 O=build_dir ARCH=powerpc SHELL=/bin/bash
> >
> > If you fix the issue, kindly add following tag where applicable
> > Reported-by: kernel test robot <lkp@intel.com>
> >
> > All warnings (new ones prefixed by >>):
> >
> >    lib/overflow_kunit.c:191:19: warning: 's64_tests' defined but not used [-Wunused-const-variable=]
> >      191 | DEFINE_TEST_ARRAY(s64) = {
> >          |                   ^~~
> >    lib/overflow_kunit.c:24:11: note: in definition of macro 'DEFINE_TEST_ARRAY'
> >       24 |         } t ## _tests[]
> >          |           ^
> >    lib/overflow_kunit.c:94:19: warning: 'u64_tests' defined but not used [-Wunused-const-variable=]
> >       94 | DEFINE_TEST_ARRAY(u64) = {
> >          |                   ^~~
> >    lib/overflow_kunit.c:24:11: note: in definition of macro 'DEFINE_TEST_ARRAY'
> >       24 |         } t ## _tests[]
> >          |           ^
> >    lib/overflow_kunit.c: In function 'overflow_size_helpers_test':
> > >> lib/overflow_kunit.c:644:1: warning: the frame size of 2832 bytes is larger than 1024 bytes [-Wframe-larger-than=]
> >      644 | }
> >          | ^
> >    lib/overflow_kunit.c: In function 'overflow_shift_test':
> >    lib/overflow_kunit.c:451:1: warning: the frame size of 7232 bytes is larger than 1024 bytes [-Wframe-larger-than=]
> >      451 | }
> >          | ^
> 
> I have an RFC series out to reduce the stack usage of KUNIT_EXPECT_*
> even further, but they won't help enough here.
> https://lore.kernel.org/linux-kselftest/20220525154442.1438081-1-dlatypov@google.com/
> 
> So If we want to try and "fix" this, I think the only answer would be
> to split up the test funcs as appropriate.
> But I don't really know if that's warranted to fix this warning here,
> which largely indicates a compiler quality problem over a code quality
> one.

I'm happy to review patches, but it does seem more like a compiler
issue. Hmmm.

-- 
Kees Cook