linux-kernel - Re: [PATCH v3] x86/boot: discard .eh

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Message-ID: <CAKwvOdn0x4jc0=25O+Xy5BsUisAPrz_hjzmBbMS0ubpfPMLgrg@mail.gmail.com>
Date:   Tue, 26 Nov 2019 09:16:08 -0800
From:   Nick Desaulniers <ndesaulniers@...gle.com>
To:     Ilie Halip <ilie.halip@...il.com>
Cc:     LKML <linux-kernel@...r.kernel.org>, Andy <luto@...nel.org>,
        Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...hat.com>, Borislav Petkov <bp@...en8.de>,
        "H. Peter Anvin" <hpa@...or.com>,
        "maintainer:X86 ARCHITECTURE (32-BIT AND 64-BIT)" <x86@...nel.org>,
        clang-built-linux <clang-built-linux@...glegroups.com>
Subject: Re: [PATCH v3] x86/boot: discard .eh_frame sections

On Tue, Nov 26, 2019 at 6:46 AM Ilie Halip <ilie.halip@...il.com> 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 GCC generates .eh_frame sections for most
> of the files in that directory, then ld.lld places the merged
> section before __end_init, triggering an assert in the linker
> script.
>
> Fix this by discarding the .eh_frame sections, as suggested by
> Boris. The kernel proper linker script discards them too.
>
> Signed-off-by: Ilie Halip <ilie.halip@...il.com>
> Link: https://lore.kernel.org/lkml/20191118175223.GM6363@zn.tnic/
> Link: https://github.com/ClangBuiltLinux/linux/issues/760
> Suggested-by: Borislav Petkov <bp@...en8.de>

Ilie, thanks for following up with a v3.
Reviewed-by: Nick Desaulniers <ndesaulniers@...gle.com>

> ---
>
> Changes in V3:
>  * discard .eh_frame instead of placing it after .rodata
>
> Changes in V2:
>  * removed wildcard for input sections (.eh_frame* -> .eh_frame)
>
>  arch/x86/boot/setup.ld | 5 ++++-
>  1 file changed, 4 insertions(+), 1 deletion(-)
>
> diff --git a/arch/x86/boot/setup.ld b/arch/x86/boot/setup.ld
> index 0149e41d42c2..3da1c37c6dd5 100644
> --- a/arch/x86/boot/setup.ld
> +++ b/arch/x86/boot/setup.ld
> @@ -51,7 +51,10 @@ SECTIONS
>         . = ALIGN(16);
>         _end = .;
>
> -       /DISCARD/ : { *(.note*) }
> +       /DISCARD/       : {
> +               *(.eh_frame)
> +               *(.note*)
> +       }
>
>         /*
>          * The ASSERT() sink to . is intentional, for binutils 2.14 compatibility:
> --
> 2.17.1
>


-- 
Thanks,
~Nick Desaulniers