Re: [PATCH mips-next] vmlinux.lds.h: catch more UBSAN symbols into .data

From: Nick Desaulniers <ndesaulniers@google.com>
To: Alexander Lobakin <alobakin@pm.me>
Cc: Thomas Bogendoerfer <tsbogend@alpha.franken.de>,
	Arnd Bergmann <arnd@arndb.de>,
	Nathan Chancellor <natechancellor@gmail.com>,
	Huacai Chen <chenhuacai@kernel.org>,
	Pei Huang <huangpei@loongson.cn>,
	Kees Cook <keescook@chromium.org>,
	Sami Tolvanen <samitolvanen@google.com>,
	Fangrui Song <maskray@google.com>,
	Jiaxun Yang <jiaxun.yang@flygoat.com>,
	Ralf Baechle <ralf@linux-mips.org>,
	Corey Minyard <cminyard@mvista.com>,
	kernel test robot <lkp@intel.com>,
	linux-mips@vger.kernel.org, LKML <linux-kernel@vger.kernel.org>,
	linux-arch <linux-arch@vger.kernel.org>,
	clang-built-linux <clang-built-linux@googlegroups.com>
Subject: Re: [PATCH mips-next] vmlinux.lds.h: catch more UBSAN symbols into .data
Date: Tue, 16 Feb 2021 09:56:32 -0800	[thread overview]
Message-ID: <CAKwvOdnBgpRff6wa8u1_ogCm_pRey5d_Yro4UCa_O_=tib0FHQ@mail.gmail.com> (raw)
In-Reply-To: <20210216085442.2967-1-alobakin@pm.me>

On Tue, Feb 16, 2021 at 12:55 AM Alexander Lobakin <alobakin@pm.me> wrote:
>
> LKP triggered lots of LD orphan warnings [0]:

Thanks for the patch, just some questions.

With which linker?  Was there a particular config from the bot's
report that triggered this?

>
> mipsel-linux-ld: warning: orphan section `.data.$Lubsan_data299' from
> `init/do_mounts_rd.o' being placed in section `.data.$Lubsan_data299'
> mipsel-linux-ld: warning: orphan section `.data.$Lubsan_data183' from
> `init/do_mounts_rd.o' being placed in section `.data.$Lubsan_data183'
> mipsel-linux-ld: warning: orphan section `.data.$Lubsan_type3' from
> `init/do_mounts_rd.o' being placed in section `.data.$Lubsan_type3'
> mipsel-linux-ld: warning: orphan section `.data.$Lubsan_type2' from
> `init/do_mounts_rd.o' being placed in section `.data.$Lubsan_type2'
> mipsel-linux-ld: warning: orphan section `.data.$Lubsan_type0' from
> `init/do_mounts_rd.o' being placed in section `.data.$Lubsan_type0'
>
> [...]
>
> Seems like "unnamed data" isn't the only type of symbols that UBSAN
> instrumentation can emit.
> Catch these into .data with the wildcard as well.
>
> [0] https://lore.kernel.org/linux-mm/202102160741.k57GCNSR-lkp@intel.com
>
> Fixes: f41b233de0ae ("vmlinux.lds.h: catch UBSAN's "unnamed data" into data")
> Reported-by: kernel test robot <lkp@intel.com>
> Signed-off-by: Alexander Lobakin <alobakin@pm.me>
> ---
>  include/asm-generic/vmlinux.lds.h | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/include/asm-generic/vmlinux.lds.h b/include/asm-generic/vmlinux.lds.h
> index cc659e77fcb0..83537e5ee78f 100644
> --- a/include/asm-generic/vmlinux.lds.h
> +++ b/include/asm-generic/vmlinux.lds.h
> @@ -95,7 +95,7 @@
>   */
>  #ifdef CONFIG_LD_DEAD_CODE_DATA_ELIMINATION
>  #define TEXT_MAIN .text .text.[0-9a-zA-Z_]*
> -#define DATA_MAIN .data .data.[0-9a-zA-Z_]* .data..L* .data..compoundliteral* .data.$__unnamed_*
> +#define DATA_MAIN .data .data.[0-9a-zA-Z_]* .data..L* .data..compoundliteral* .data.$__unnamed_* .data.$Lubsan_*

Are these sections only created when
CONFIG_LD_DEAD_CODE_DATA_ELIMINATION is selected?  (Same with
.data.$__unnamed_*)

>  #define SDATA_MAIN .sdata .sdata.[0-9a-zA-Z_]*
>  #define RODATA_MAIN .rodata .rodata.[0-9a-zA-Z_]* .rodata..L*
>  #define BSS_MAIN .bss .bss.[0-9a-zA-Z_]* .bss..compoundliteral*
> --
> 2.30.1
>
>

-- 
Thanks,
~Nick Desaulniers