linux-kernel - Re: [PATCH] ARM: drop unused DEBUG_RODATA from XIP

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Date:	Tue, 16 Feb 2016 15:41:41 -0500 (EST)
From:	Nicolas Pitre <nicolas.pitre@...aro.org>
To:	Kees Cook <keescook@...omium.org>
cc:	Russell King <linux@....linux.org.uk>,
	Ard Biesheuvel <ard.biesheuvel@...aro.org>,
	Arnd Bergmann <arnd@...db.de>,
	Geert Uytterhoeven <geert@...ux-m68k.org>,
	Chris Brandt <Chris.Brandt@...esas.com>,
	Will Deacon <will.deacon@....com>,
	Marc Zyngier <marc.zyngier@....com>,
	linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] ARM: drop unused DEBUG_RODATA from XIP_KERNEL

On Tue, 16 Feb 2016, Kees Cook wrote:

> With CONFIG_DEBUG_RODATA not being sensible under XIP_KERNEL, remove it
> from the XIP linker script.

If so you should also make DEBUG_RODATA depend on !XIP_KERNEL in Kconfig 
to avoid offering a config option that does nothing.

> Signed-off-by: Kees Cook <keescook@...omium.org>
> ---
> Effectively the patch after Arnd's "ARM: mm: hide
> __start_rodata_section_aligned for non-debug builds"
> ---
>  arch/arm/kernel/vmlinux-xip.lds.S | 10 ----------
>  1 files changed, 0 insertions(+), 10 deletions(-)
> 
> diff --git a/arch/arm/kernel/vmlinux-xip.lds.S b/arch/arm/kernel/vmlinux-xip.lds.S
> index 40bc4cadb959..cba1ec899a69 100644
> --- a/arch/arm/kernel/vmlinux-xip.lds.S
> +++ b/arch/arm/kernel/vmlinux-xip.lds.S
> @@ -8,9 +8,6 @@
>  #include <asm/thread_info.h>
>  #include <asm/memory.h>
>  #include <asm/page.h>
> -#ifdef CONFIG_DEBUG_RODATA
> -#include <asm/pgtable.h>
> -#endif
>  
>  #define PROC_INFO							\
>  	. = ALIGN(4);							\
> @@ -92,10 +89,6 @@ SECTIONS
>  		HEAD_TEXT
>  	}
>  
> -#ifdef CONFIG_DEBUG_RODATA
> -	. = ALIGN(1<<SECTION_SHIFT);
> -#endif
> -
>  	.text : {			/* Real text segment		*/
>  		_stext = .;		/* Text and read-only data	*/
>  			IDMAP_TEXT
> @@ -115,9 +108,6 @@ SECTIONS
>  			ARM_CPU_KEEP(PROC_INFO)
>  	}
>  
> -#ifdef CONFIG_DEBUG_RODATA
> -	. = ALIGN(1<<SECTION_SHIFT);
> -#endif
>  	RO_DATA(PAGE_SIZE)
>  
>  	. = ALIGN(4);
> -- 
> 2.6.3
> 
> 
> -- 
> Kees Cook
> Chrome OS & Brillo Security
> 
>