linux-kernel - Re: [PATCH] x86/boot/compressed: Fix compressed kernel linking with lld

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Message-ID: <20200222181413.GA22627@ubuntu-m2-xlarge-x86>
Date:   Sat, 22 Feb 2020 11:14:13 -0700
From:   Nathan Chancellor <natechancellor@...il.com>
To:     Arvind Sankar <nivedita@...m.mit.edu>
Cc:     Fangrui Song <maskray@...gle.com>, Borislav Petkov <bp@...en8.de>,
        Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...hat.com>,
        "H. Peter Anvin" <hpa@...or.com>, x86@...nel.org,
        linux-kernel@...r.kernel.org, clang-built-linux@...glegroups.com,
        Michael Matz <matz@...e.de>
Subject: Re: [PATCH] x86/boot/compressed: Fix compressed kernel linking with
 lld

On Sat, Feb 22, 2020 at 12:18:59PM -0500, Arvind Sankar wrote:
> Commit TBD ("x86/boot/compressed: Remove unnecessary sections from
> bzImage") discarded unnecessary sections with *(*). While this works
> fine with the bfd linker, lld tries to also discard essential sections
> like .shstrtab, .symtab and .strtab, which results in the link failing
> since .shstrtab is required by the ELF specification. .symtab and
> .strtab are also necessary to generate the zoffset.h file for the
> bzImage header.
> 
> Since the only sizeable section that can be discarded is .eh_frame,
> restrict the discard to only .eh_frame to be safe.
> 
> Signed-off-by: Arvind Sankar <nivedita@...m.mit.edu>
> ---
> Sending as a fix on top of tip/x86/boot.
> 
>  arch/x86/boot/compressed/vmlinux.lds.S | 4 ++--
>  1 file changed, 2 insertions(+), 2 deletions(-)
> 
> diff --git a/arch/x86/boot/compressed/vmlinux.lds.S b/arch/x86/boot/compressed/vmlinux.lds.S
> index 12a20603d92e..469dcf800a2c 100644
> --- a/arch/x86/boot/compressed/vmlinux.lds.S
> +++ b/arch/x86/boot/compressed/vmlinux.lds.S
> @@ -74,8 +74,8 @@ SECTIONS
>  	. = ALIGN(PAGE_SIZE);	/* keep ZO size page aligned */
>  	_end = .;
>  
> -	/* Discard all remaining sections */
> +	/* Discard .eh_frame to save some space */
>  	/DISCARD/ : {
> -		*(*)
> +		*(.eh_frame)
>  	}
>  }
> -- 
> 2.24.1
> 

FWIW:

Tested-by: Nathan Chancellor <natechancellor@...il.com>