linux-kernel - Re: [PATCH v4 mips-next 6/7] vmlinux.lds.h: catch compound literals into data and BSS

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Message-ID: <202101071350.B643907EE@keescook>
Date:   Thu, 7 Jan 2021 13:51:03 -0800
From:   Kees Cook <keescook@...omium.org>
To:     Alexander Lobakin <alobakin@...me>
Cc:     Thomas Bogendoerfer <tsbogend@...ha.franken.de>,
        Arnd Bergmann <arnd@...db.de>,
        Nathan Chancellor <natechancellor@...il.com>,
        Nick Desaulniers <ndesaulniers@...gle.com>,
        Fangrui Song <maskray@...gle.com>,
        Huacai Chen <chenhuacai@...nel.org>,
        Pei Huang <huangpei@...ngson.cn>,
        Jiaxun Yang <jiaxun.yang@...goat.com>,
        Sami Tolvanen <samitolvanen@...gle.com>,
        Ingo Molnar <mingo@...nel.org>,
        Ralf Baechle <ralf@...ux-mips.org>,
        Corey Minyard <cminyard@...sta.com>,
        linux-mips@...r.kernel.org, linux-kernel@...r.kernel.org,
        linux-arch@...r.kernel.org, stable@...r.kernel.org,
        clang-built-linux@...glegroups.com
Subject: Re: [PATCH v4 mips-next 6/7] vmlinux.lds.h: catch compound literals
 into data and BSS

On Thu, Jan 07, 2021 at 01:20:55PM +0000, Alexander Lobakin wrote:
> When building kernel with LD_DEAD_CODE_DATA_ELIMINATION, LLVM stack
> generates separate sections for compound literals, just like in case
> with enabled LTO [0]:
> 
> ld.lld: warning: drivers/built-in.a(mtd/nand/spi/gigadevice.o):
> (.data..compoundliteral.14) is being placed in
> '.data..compoundliteral.14'
> ld.lld: warning: drivers/built-in.a(mtd/nand/spi/gigadevice.o):
> (.data..compoundliteral.15) is being placed in
> '.data..compoundliteral.15'
> ld.lld: warning: drivers/built-in.a(mtd/nand/spi/gigadevice.o):
> (.data..compoundliteral.16) is being placed in
> '.data..compoundliteral.16'
> ld.lld: warning: drivers/built-in.a(mtd/nand/spi/gigadevice.o):
> (.data..compoundliteral.17) is being placed in
> '.data..compoundliteral.17'
> 
> [...]
> 
> Handle this by adding the related sections to generic definitions
> as suggested by Sami [0].
> 
> [0] https://lore.kernel.org/lkml/20201211184633.3213045-3-samitolvanen@google.com
> 
> Suggested-by: Kees Cook <keescook@...omium.org>
> Signed-off-by: Alexander Lobakin <alobakin@...me>

Suggested-by: Sami Tolvanen <samitolvanen@...gle.com>
Reviewed-by: Kees Cook <keescook@...omium.org>

-- 
Kees Cook