linux-kernel - Re: [PATCH 1/2] powerpc: Discard .rela* sections if CONFIG

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Date:   Tue, 28 Apr 2020 07:31:38 +0200
From:   Christophe Leroy <christophe.leroy@....fr>
To:     "H.J. Lu" <hjl.tools@...il.com>, linux-kernel@...r.kernel.org
Cc:     linux-arch@...r.kernel.org, Yu-cheng Yu <yu-cheng.yu@...el.com>,
        Kees Cook <keescook@...omium.org>,
        Arnd Bergmann <arnd@...db.de>,
        Paul Mackerras <paulus@...ba.org>,
        "Naveen N . Rao" <naveen.n.rao@...ux.vnet.ibm.com>,
        Borislav Petkov <bp@...e.de>, linuxppc-dev@...ts.ozlabs.org
Subject: Re: [PATCH 1/2] powerpc: Discard .rela* sections if
 CONFIG_RELOCATABLE is undefined

Hi,

Le 28/04/2020 à 03:48, H.J. Lu a écrit :
> arch/powerpc/kernel/vmlinux.lds.S has
> 
>          DISCARDS
>          /DISCARD/ : {
>                  *(*.EMB.apuinfo)
>                  *(.glink .iplt .plt .rela* .comment)
>                  *(.gnu.version*)
>                  *(.gnu.attributes)
>                  *(.eh_frame)
>          }
> 
> Since .rela* sections are needed when CONFIG_RELOCATABLE is defined,
> change to discard .rela* sections if CONFIG_RELOCATABLE is undefined.

Your explanation and especially the subject are unclear.

 From the subject you understand that you are adding a discard of the 
.rela* sections if CONFIG_RELOCATABLE is undefined.

But when reading the patch, you see that it is the contrary: you are 
removing a discard of the .rela* sections if CONFIG_RELOCATABLE is defined.


So I think the subject could instead be:

	Only discard .rela* sections when CONFIG_RELOCATABLE is undefined

Or maybe better:

	Keep .rela* sections when CONFIG_RELOCATABLE is defined

And the explanation could be:

	Since .rela* sections are needed when CONFIG_RELOCATABLE
	is defined, don't discard .rela* sections if
	CONFIG_RELOCATABLE is defined.

> 
> Signed-off-by: H.J. Lu <hjl.tools@...il.com>
> Acked-by: Michael Ellerman <mpe@...erman.id.au> (powerpc)
> ---
>   arch/powerpc/kernel/vmlinux.lds.S | 5 ++++-
>   1 file changed, 4 insertions(+), 1 deletion(-)
> 
> diff --git a/arch/powerpc/kernel/vmlinux.lds.S b/arch/powerpc/kernel/vmlinux.lds.S
> index 31a0f201fb6f..4ba07734a210 100644
> --- a/arch/powerpc/kernel/vmlinux.lds.S
> +++ b/arch/powerpc/kernel/vmlinux.lds.S
> @@ -366,9 +366,12 @@ SECTIONS
>   	DISCARDS
>   	/DISCARD/ : {
>   		*(*.EMB.apuinfo)
> -		*(.glink .iplt .plt .rela* .comment)
> +		*(.glink .iplt .plt .comment)
>   		*(.gnu.version*)
>   		*(.gnu.attributes)
>   		*(.eh_frame)
> +#ifndef CONFIG_RELOCATABLE
> +		*(.rela*)
> +#endif
>   	}
>   }
> 

Christophe