linux-kernel - Re: [PATCH v5 mips-next 0/9] MIPS: vmlinux.lds.S sections fixes & cleanup

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Date:   Mon, 11 Jan 2021 11:53:39 -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>,
        Huacai Chen <chenhuacai@...nel.org>,
        Pei Huang <huangpei@...ngson.cn>,
        Fangrui Song <maskray@...gle.com>,
        Jiaxun Yang <jiaxun.yang@...goat.com>,
        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 v5 mips-next 0/9] MIPS: vmlinux.lds.S sections fixes &
 cleanup

On Sun, Jan 10, 2021 at 11:53:50AM +0000, Alexander Lobakin wrote:
> This series hunts the problems discovered after manual enabling of
> ARCH_WANT_LD_ORPHAN_WARN. Notably:
>  - adds the missing PAGE_ALIGNED_DATA() section affecting VDSO
>    placement (marked for stable);
>  - stops blind catching of orphan text sections with .text.*
>    directive;
>  - properly stops .eh_frame section generation.
> 
> Compile and runtime tested on MIPS32R2 CPS board with no issues
> using two different toolkits:
>  - Binutils 2.35.1, GCC 10.2.1 (with Alpine patches);
>  - LLVM stack: 11.0.0 and from latest Git snapshot.
> 
> Since v4 [3]:
>  - new: drop redundant .text.cps-vec creation and blind inclusion
>    of orphan text sections via .text.* directive in vmlinux.lds.S;
>  - don't assert SIZEOF(.rel.dyn) as it's reported that it may be not
>    empty on certain machines and compilers (Thomas);
>  - align GOT table like it's done for ARM64;
>  - new: catch UBSAN's "unnamed data" sections in generic definitions
>    when building with LD_DEAD_CODE_DATA_ELIMINATION;
>  - collect Reviewed-bys (Kees, Nathan).

Looks good; which tree will this land through?

-Kees

> 
> Since v3 [2]:
>  - fix the third patch as GNU stack emits .rel.dyn into VDSO for
>    some reason if .cfi_sections is specified.
> 
> Since v2 [1]:
>  - stop discarding .eh_frame and just prevent it from generating
>    (Kees);
>  - drop redundant sections assertions (Fangrui);
>  - place GOT table in .text instead of asserting as it's not empty
>    when building with LLVM (Nathan);
>  - catch compound literals in generic definitions when building with
>    LD_DEAD_CODE_DATA_ELIMINATION (Kees);
>  - collect two Reviewed-bys (Kees).
> 
> Since v1 [0]:
>  - catch .got entries too as LLD may produce it (Nathan);
>  - check for unwanted sections to be zero-sized instead of
>    discarding (Fangrui).
> 
> [0] https://lore.kernel.org/linux-mips/20210104121729.46981-1-alobakin@pm.me
> [1] https://lore.kernel.org/linux-mips/20210106200713.31840-1-alobakin@pm.me
> [2] https://lore.kernel.org/linux-mips/20210107115120.281008-1-alobakin@pm.me
> [3] https://lore.kernel.org/linux-mips/20210107123331.354075-1-alobakin@pm.me
> 
> Alexander Lobakin (9):
>   MIPS: vmlinux.lds.S: add missing PAGE_ALIGNED_DATA() section
>   MIPS: CPS: don't create redundant .text.cps-vec section
>   MIPS: vmlinux.lds.S: add ".gnu.attributes" to DISCARDS
>   MIPS: properly stop .eh_frame generation
>   MIPS: vmlinux.lds.S: explicitly catch .rel.dyn symbols
>   MIPS: vmlinux.lds.S: explicitly declare .got table
>   vmlinux.lds.h: catch compound literals into data and BSS
>   vmlinux.lds.h: catch UBSAN's "unnamed data" into data
>   MIPS: select ARCH_WANT_LD_ORPHAN_WARN
> 
>  arch/mips/Kconfig                 |  1 +
>  arch/mips/include/asm/asm.h       | 18 ++++++++++++++++++
>  arch/mips/kernel/cps-vec.S        |  1 -
>  arch/mips/kernel/vmlinux.lds.S    | 11 +++++++++--
>  include/asm-generic/vmlinux.lds.h |  6 +++---
>  5 files changed, 31 insertions(+), 6 deletions(-)
> 
> -- 
> 2.30.0
> 
> 

-- 
Kees Cook