linux-kernel - Re: [PATCH V2] x86/boot: explicitly place .eh

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Date:   Mon, 18 Nov 2019 15:35:53 +0100
From:   Borislav Petkov <bp@...en8.de>
To:     Ilie Halip <ilie.halip@...il.com>
Cc:     linux-kernel@...r.kernel.org,
        Nick Desaulniers <ndesaulniers@...gle.com>,
        Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...hat.com>,
        "H. Peter Anvin" <hpa@...or.com>, x86@...nel.org,
        clang-built-linux@...glegroups.com
Subject: Re: [PATCH V2] x86/boot: explicitly place .eh_frame after .rodata

On Wed, Nov 06, 2019 at 02:06:28PM +0200, Ilie Halip wrote:
> When using GCC as compiler and LLVM's lld as linker, linking
> setup.elf fails:
>       LD      arch/x86/boot/setup.elf
>     ld.lld: error: init sections too big!
> 
> This happens because ld.lld has different rules for placing
> orphan sections (i.e. sections not mentioned in a linker script)
> compared to ld.bfd.
> 
> Particularly, in this case, the merged .eh_frame section is
> placed before __end_init, which triggers an assert in the script.
> 
> Explicitly place this section after .rodata, in accordance with
> ld.bfd's behavior.
> 
> Signed-off-by: Ilie Halip <ilie.halip@...il.com>
> Link: https://github.com/ClangBuiltLinux/linux/issues/760
> ---
> 
> Changes in V2:
>  * removed wildcard for input sections (.eh_frame* -> .eh_frame)
> 
>  arch/x86/boot/setup.ld | 1 +
>  1 file changed, 1 insertion(+)
> 
> diff --git a/arch/x86/boot/setup.ld b/arch/x86/boot/setup.ld
> index 0149e41d42c2..30ce52635cd0 100644
> --- a/arch/x86/boot/setup.ld
> +++ b/arch/x86/boot/setup.ld
> @@ -25,6 +25,7 @@ SECTIONS
>  
>  	. = ALIGN(16);
>  	.rodata		: { *(.rodata*) }
> +	.eh_frame	: { *(.eh_frame) }

The kernel proper linker script does

        /DISCARD/ : {
                *(.eh_frame)
        }

with the .eh_frame section.

Wouldn't that solve your issue too, if you add it to the /DISCARD/
section in that linker script too?

-- 
Regards/Gruss,
    Boris.

https://people.kernel.org/tglx/notes-about-netiquette