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 20:57:25 +0000
From:   Alexander Lobakin <alobakin@...me>
To:     Kees Cook <keescook@...omium.org>
Cc:     Alexander Lobakin <alobakin@...me>,
        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

From: Kees Cook <keescook@...omium.org>
Date: Mon, 11 Jan 2021 11:53:39 -0800

> 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?

linux-mips/mips-next I guess, since 7 of 9 patches are related only
to this architecture.
This might need Arnd's Acked-bys or Reviewed-by for the two that
refer include/asm-generic, let's see what Thomas think.

> -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

Al