linux-kernel - Re: [PATCH] arm64 module: remove (NOLOAD)

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Message-ID: <20220218085016.jv4qcfaxav5fxhrs@google.com>
Date:   Fri, 18 Feb 2022 00:50:16 -0800
From:   Fangrui Song <maskray@...gle.com>
To:     Ard Biesheuvel <ardb@...nel.org>
Cc:     Catalin Marinas <catalin.marinas@....com>,
        Will Deacon <will@...nel.org>,
        Linux ARM <linux-arm-kernel@...ts.infradead.org>,
        Nathan Chancellor <nathan@...nel.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        llvm@...ts.linux.dev
Subject: Re: [PATCH] arm64 module: remove (NOLOAD)

On 2022-02-18, Ard Biesheuvel wrote:
>On Fri, 18 Feb 2022 at 09:12, Fangrui Song <maskray@...gle.com> wrote:
>>
>> On ELF, (NOLOAD) sets the section type to SHT_NOBITS[1]. It is conceptually
>> inappropriate for .plt and .text.* sections which are always
>> SHT_PROGBITS.
>>
>> In GNU ld, if PLT entries are needed, .plt will be SHT_PROGBITS anyway
>> and (NOLOAD) will be essentially ignored. In ld.lld, since
>> https://reviews.llvm.org/D118840 ("[ELF] Support (TYPE=<value>) to
>> customize the output section type"), ld.lld will report a `section type
>> mismatch` error. Just remove (NOLOAD) to fix the error.
>>
>> [1] https://lld.llvm.org/ELF/linker_script.html As of today, "The
>> section should be marked as not loadable" on
>> https://sourceware.org/binutils/docs/ld/Output-Section-Type.html is
>> outdated for ELF.
>
>This patch lacks a SOB line.
>
>With one added,
>
>Acked-by: Ard Biesheuvel <ardb@...nel.org>

Ah, yes. Sorry, I haven't sent a kernel patch for a while...

Reported-by: Nathan Chancellor <nathan@...nel.org>
Signed-off-by: Fangrui Song <maskray@...gle.com>
Acked-by: Ard Biesheuvel <ardb@...nel.org>

>> ---
>>  arch/arm64/include/asm/module.lds.h | 6 +++---
>>  1 file changed, 3 insertions(+), 3 deletions(-)
>>
>> diff --git a/arch/arm64/include/asm/module.lds.h b/arch/arm64/include/asm/module.lds.h
>> index a11ccadd47d2..094701ec5500 100644
>> --- a/arch/arm64/include/asm/module.lds.h
>> +++ b/arch/arm64/include/asm/module.lds.h
>> @@ -1,8 +1,8 @@
>>  SECTIONS {
>>  #ifdef CONFIG_ARM64_MODULE_PLTS
>> -       .plt 0 (NOLOAD) : { BYTE(0) }
>> -       .init.plt 0 (NOLOAD) : { BYTE(0) }
>> -       .text.ftrace_trampoline 0 (NOLOAD) : { BYTE(0) }
>> +       .plt 0 : { BYTE(0) }
>> +       .init.plt 0 : { BYTE(0) }
>> +       .text.ftrace_trampoline 0 : { BYTE(0) }
>>  #endif
>>
>>  #ifdef CONFIG_KASAN_SW_TAGS
>> --
>> 2.35.1.265.g69c8d7142f-goog
>>