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

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Message-ID: <20200521152036.GB502432@rani.riverdale.lan>
Date:   Thu, 21 May 2020 11:20:36 -0400
From:   Arvind Sankar <nivedita@...m.mit.edu>
To:     Fangrui Song <maskray@...gle.com>
Cc:     Arvind Sankar <nivedita@...m.mit.edu>,
        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 Wed, May 20, 2020 at 07:12:17PM -0700, Fangrui Song wrote:
> 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>

Thanks. I'll reword the commit message to include a reference to that
change. It's also not just 64-bit, on 32-bit it currently fails before
it gets around to linking setup.elf due to the text relocs issues,
that's why this one doesn't show up, but they are in fact at least
consistent.