linux-kernel - Re: [PATCH 0/1] x86/boot: lld fix

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Date:   Wed, 20 May 2020 19:12:17 -0700
From:   Fangrui Song <maskray@...gle.com>
To:     Arvind Sankar <nivedita@...m.mit.edu>
Cc:     clang-built-linux@...glegroups.com, x86@...nel.org,
        Nick Desaulniers <ndesaulniers@...gle.com>,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH 0/1] x86/boot: lld fix

On 2020-05-20, Arvind Sankar wrote:
>On Wed, May 20, 2020 at 06:56:53PM -0400, Arvind Sankar wrote:
>> arch/x86/boot/setup.elf currently has an orphan section .text.startup,
>> and lld git as of ebf14d9b6d8b is breaking on 64-bit due to what seems
>> to be a change in behavior on orphan section placement (details in patch
>> commit message).
>>
>> I'm not sure if this was an intentional change in lld, but it seems like
>> a good idea to explicitly include .text.startup anyway.
>>
>> Arvind Sankar (1):
>>   x86/boot: Add .text.startup to setup.ld
>>
>>  arch/x86/boot/setup.ld | 2 +-
>>  1 file changed, 1 insertion(+), 1 deletion(-)
>>
>> --
>> 2.26.2
>>

I found your PATCH 1/1 on https://lkml.org/lkml/2020/5/20/1491 

-	.text		: { *(.text) }
+	.text		: { *(.text.startup) *(.text) }

The LLD behavior change was introduced in
https://reviews.llvm.org/D75225 (will be included in 11.0.0)
It was intended to match GNU ld.

But yes, orphan section placement is still different in the two linkers.

Placing .text.startup before .text seems good.
In GNU ld's internal linker script (ld --verbose),
.text.startup is placed before .text

Reviewed-by: Fangrui Song <maskray@...gle.com>