linux-kernel - Re: [PATCH] ubsan: Implement __ubsan_handle_alignment

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Message-ID: <20210113013130.GA3446359@ubuntu-m3-large-x86>
Date:   Tue, 12 Jan 2021 18:31:30 -0700
From:   Nathan Chancellor <natechancellor@...il.com>
To:     kernel test robot <lkp@...el.com>
Cc:     Kees Cook <keescook@...omium.org>,
        Andrew Morton <akpm@...ux-foundation.org>,
        kbuild-all@...ts.01.org, clang-built-linux@...glegroups.com,
        Linux Memory Management List <linux-mm@...ck.org>,
        Nick Desaulniers <ndesaulniers@...gle.com>,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH] ubsan: Implement __ubsan_handle_alignment_assumption

On Wed, Jan 13, 2021 at 08:39:52AM +0800, kernel test robot wrote:
> Hi Nathan,
> 
> I love your patch! Perhaps something to improve:
> 
> [auto build test WARNING on 7c53f6b671f4aba70ff15e1b05148b10d58c2837]
> 
> url:    https://github.com/0day-ci/linux/commits/Nathan-Chancellor/ubsan-Implement-__ubsan_handle_alignment_assumption/20210113-055714
> base:    7c53f6b671f4aba70ff15e1b05148b10d58c2837
> config: arm64-randconfig-r031-20210112 (attached as .config)
> compiler: clang version 12.0.0 (https://github.com/llvm/llvm-project 32bcfcda4e28375e5a85268d2acfabcfcc011abf)
> 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
>         # install arm64 cross compiling tool for clang build
>         # apt-get install binutils-aarch64-linux-gnu
>         # https://github.com/0day-ci/linux/commit/775adad26a60878926c0ee6cd460a1375bbe51e6
>         git remote add linux-review https://github.com/0day-ci/linux
>         git fetch --no-tags linux-review Nathan-Chancellor/ubsan-Implement-__ubsan_handle_alignment_assumption/20210113-055714
>         git checkout 775adad26a60878926c0ee6cd460a1375bbe51e6
>         # save the attached .config to linux build tree
>         COMPILER_INSTALL_PATH=$HOME/0day COMPILER=clang make.cross ARCH=arm64 
> 
> If you fix the issue, kindly add following tag as appropriate
> Reported-by: kernel test robot <lkp@...el.com>
> 
> All warnings (new ones prefixed by >>):
> 
>    lib/ubsan.c:192:6: warning: no previous prototype for function '__ubsan_handle_add_overflow' [-Wmissing-prototypes]
>    void __ubsan_handle_add_overflow(void *data,
>         ^
>    lib/ubsan.c:192:1: note: declare 'static' if the function is not intended to be used outside of this translation unit
>    void __ubsan_handle_add_overflow(void *data,
>    ^
>    static 
>    lib/ubsan.c:200:6: warning: no previous prototype for function '__ubsan_handle_sub_overflow' [-Wmissing-prototypes]
>    void __ubsan_handle_sub_overflow(void *data,
>         ^
>    lib/ubsan.c:200:1: note: declare 'static' if the function is not intended to be used outside of this translation unit
>    void __ubsan_handle_sub_overflow(void *data,
>    ^

Given that these are compiler inserted functions, there is not much of a
point to having prototypes to them. If people feel shutting these
warnings up is worthwhile, we can just add the prototypes right above
the function definition in a follow up patch.

Cheers,
Nathan