linux-kernel - Re: [PATCH v4] MIPS: Truncate link address into 32bit for 32bit kernel

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Date:   Mon, 13 Apr 2020 15:32:05 +0800
From:   Jiaxun Yang <jiaxun.yang@...goat.com>
To:     "Maciej W. Rozycki" <macro@...ux-mips.org>
Cc:     linux-mips@...r.kernel.org, clang-built-linux@...glegroups.com,
        Fangrui Song <maskray@...gle.com>,
        Nathan Chancellor <natechancellor@...il.com>,
        Thomas Bogendoerfer <tsbogend@...ha.franken.de>,
        Borislav Petkov <bp@...e.de>,
        Kees Cook <keescook@...omium.org>,
        Heiko Carstens <heiko.carstens@...ibm.com>,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH v4] MIPS: Truncate link address into 32bit for 32bit
 kernel

On Mon, 13 Apr 2020 07:59:29 +0100 (BST)
"Maciej W. Rozycki" <macro@...ux-mips.org> wrote:

> On Mon, 13 Apr 2020, Jiaxun Yang wrote:
> 
> > LLD failed to link vmlinux with 64bit load address for 32bit ELF
> > while bfd will strip 64bit address into 32bit silently.
> > To fix LLD build, we should truncate load address provided by
> > platform into 32bit for 32bit kernel.  
> 
> Reviewed-by: Maciej W. Rozycki <macro@...ux-mips.org>
> 
> > diff --git a/arch/mips/kernel/vmlinux.lds.S
> > b/arch/mips/kernel/vmlinux.lds.S index a5f00ec73ea6..5226cd8e4bee
> > 100644 --- a/arch/mips/kernel/vmlinux.lds.S
> > +++ b/arch/mips/kernel/vmlinux.lds.S
> > @@ -55,7 +55,7 @@ SECTIONS
> >  	/* . = 0xa800000000300000; */
> >  	. = 0xffffffff80300000;
> >  #endif
> > -	. = VMLINUX_LOAD_ADDRESS;
> > +	. = VMLINUX_LINK_ADDRESS;  
> 
>  The CONFIG_BOOT_ELF64 cruft right above it looks interesting to me,
> never have ever been used.  We have had the current arrangement since:

It confused me either.
It's only used by SGI so probably it's time to rename it as
BOOT_SEG_ELF64.

Wish someone could clarify what is it.

Thanks.

> 
> commit 923ec3d20eef9e36456868b590873ce39f17fe71
> Author: Ralf Baechle <ralf@...ux-mips.org>
> Date:   Wed Nov 6 22:16:38 2002 +0000
> 
>     Define load address in linker script instead of relying on the
>     deprecated and notoriously unreliable option -Ttext.
> 
> and previously `-Ttext' was used with this script anyway, though not
> very long, as the script was entirely ignored until:
> 
> commit 7a782968041ffc4c2d89816238e2f8ea5cceddba
> Author: Ralf Baechle <ralf@...ux-mips.org>
> Date:   Thu Oct 31 23:54:21 2002 +0000
> 
>     Merge with Linux 2.5.36.
> 
>   Maciej

--
Jiaxun Yang