Subject: Re: [PATCH 14/29] vmlinux.lds.h: Allow EXCEPTION_TABLE to live in RO_DATA

From: Borislav Petkov <[email-masked]>
Date: Thu, 10 Oct 2019 17:25:16 +0200

On Thu, Sep 26, 2019 at 10:55:47AM -0700, Kees Cook wrote:
> Many architectures have an EXCEPTION_TABLE that needs only to be
> read-only. As such, it should live in RO_DATA. This creates a macro to
> identify this case for the architectures that can move EXCEPTION_TABLE
> into RO_DATA.
> 
> Signed-off-by: Kees Cook <[email-masked]>
> ---
>  include/asm-generic/vmlinux.lds.h | 12 ++++++++++++
>  1 file changed, 12 insertions(+)
> 
> diff --git a/include/asm-generic/vmlinux.lds.h b/include/asm-generic/vmlinux.lds.h
> index d57a28786bb8..35a6cba39d9f 100644
> --- a/include/asm-generic/vmlinux.lds.h
> +++ b/include/asm-generic/vmlinux.lds.h
> @@ -69,6 +69,17 @@
>  #define NOTES_HEADERS_RESTORE
>  #endif
>  
> +/*
> + * Some architectures have non-executable read-only exception tables.
> + * They can be added to the RO_DATA segment by specifying their desired
> + * alignment.
> + */
> +#ifdef RO_DATA_EXCEPTION_TABLE_ALIGN
> +#define RO_DATA_EXCEPTION_TABLE	EXCEPTION_TABLE(RO_DATA_EXCEPTION_TABLE_ALIGN)
> +#else
> +#define RO_DATA_EXCEPTION_TABLE
> +#endif
> +
>  /* Align . to a 8 byte boundary equals to maximum function alignment. */
>  #define ALIGN_FUNCTION()  . = ALIGN(8)
>  
> @@ -508,6 +519,7 @@
>  		__stop___modver = .;					\
>  	}								\
>  									\
> +	RO_DATA_EXCEPTION_TABLE						\
>  	NOTES								\
>  									\
>  	. = ALIGN((align));						\
> -- 

I think you can drop the "DATA" from the names as it is kinda clear
where the exception table lands:

RO_EXCEPTION_TABLE_ALIGN
RO_EXCEPTION_TABLE

The "read-only" part is the important one.

-- 
Regards/Gruss,
    Boris.

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