Re: [PATCH 18/29] arm64: Move EXCEPTION_TABLE to RO_DATA segment

[Will Deacon]

Hi Kees,

On Thu, Sep 26, 2019 at 10:55:51AM -0700, Kees Cook wrote:
> The EXCEPTION_TABLE is read-only, so collapse it into RO_DATA.
> 
> Signed-off-by: Kees Cook <keescook@xxxxxxxxxxxx>
> ---
>  arch/arm64/kernel/vmlinux.lds.S | 6 ++++--
>  1 file changed, 4 insertions(+), 2 deletions(-)
> 
> diff --git a/arch/arm64/kernel/vmlinux.lds.S b/arch/arm64/kernel/vmlinux.lds.S
> index 81d94e371c95..c6ba2eee0ee8 100644
> --- a/arch/arm64/kernel/vmlinux.lds.S
> +++ b/arch/arm64/kernel/vmlinux.lds.S
> @@ -5,6 +5,8 @@
>   * Written by Martin Mares <mj@xxxxxxxxxxxxxxxxxxxxxxxx>
>   */
>  
> +#define RO_DATA_EXCEPTION_TABLE_ALIGN	8
> +
>  #include <asm-generic/vmlinux.lds.h>
>  #include <asm/cache.h>
>  #include <asm/kernel-pgtable.h>
> @@ -135,8 +137,8 @@ SECTIONS
>  	. = ALIGN(SEGMENT_ALIGN);
>  	_etext = .;			/* End of text section */
>  
> -	RO_DATA(PAGE_SIZE)		/* everything from this point to     */
> -	EXCEPTION_TABLE(8)		/* __init_begin will be marked RO NX */
> +	/* everything from this point to __init_begin will be marked RO NX */
> +	RO_DATA(PAGE_SIZE)
>  
>  	. = ALIGN(PAGE_SIZE);

Do you reckon it would be worth merging this last ALIGN directive into the
RO_DATA definition too? Given that we want to map the thing read-only, it
really has to be aligned either side.

Anyway, that's only a nit, so:

Acked-by: Will Deacon <will@xxxxxxxxxx>

Will

P.S. Please CC the arm64 maintainers on arm64 patches -- I nearly missed
this one!