linux-kernel - Re: [PATCH] arm: get rid of hardcoded assumptions about kernel stack size

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Date:	Wed, 18 Jun 2014 10:40:02 -0400 (EDT)
From:	Nicolas Pitre <nicolas.pitre@...aro.org>
To:	Andrey Ryabinin <a.ryabinin@...sung.com>
cc:	Russell King <linux@....linux.org.uk>,
	Catalin Marinas <catalin.marinas@....com>,
	Will Deacon <will.deacon@....com>,
	linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] arm: get rid of hardcoded assumptions about kernel stack
 size

On Wed, 18 Jun 2014, Andrey Ryabinin wrote:

> Changing kernel stack size on arm is not as simple as it should be:
> 1) THRED_SIZE macro doen't respect PAGE_SIZE and THREAD_SIZE_ORDER
> 2) stack size is hardcoded in get_thread_info macro
> 
> This patch fixes it by caculating THREAD_SIZE and thread_info address
> taking into account PAGE_SIZE and THREAD_SIZE_ORDER.
> 
> Now changing stack size becomes simply changing THREAD_SIZE_ORDER.
> 
> Signed-off-by: Andrey Ryabinin <a.ryabinin@...sung.com>

Acked-by: Nicolas Pitre <nico@...aro.org>


> ---
>  arch/arm/include/asm/assembler.h   | 8 +++++---
>  arch/arm/include/asm/thread_info.h | 3 ++-
>  2 files changed, 7 insertions(+), 4 deletions(-)
> 
> diff --git a/arch/arm/include/asm/assembler.h b/arch/arm/include/asm/assembler.h
> index 57f0584..906703a 100644
> --- a/arch/arm/include/asm/assembler.h
> +++ b/arch/arm/include/asm/assembler.h
> @@ -24,6 +24,8 @@
>  #include <asm/domain.h>
>  #include <asm/opcodes-virt.h>
>  #include <asm/asm-offsets.h>
> +#include <asm/page.h>
> +#include <asm/thread_info.h>
>  
>  #define IOMEM(x)	(x)
>  
> @@ -179,10 +181,10 @@
>   * Get current thread_info.
>   */
>  	.macro	get_thread_info, rd
> - ARM(	mov	\rd, sp, lsr #13	)
> + ARM(	mov	\rd, sp, lsr #THREAD_SIZE_ORDER + PAGE_SHIFT	)
>   THUMB(	mov	\rd, sp			)
> - THUMB(	lsr	\rd, \rd, #13		)
> -	mov	\rd, \rd, lsl #13
> + THUMB(	lsr	\rd, \rd, #THREAD_SIZE_ORDER + PAGE_SHIFT	)
> +	mov	\rd, \rd, lsl #THREAD_SIZE_ORDER + PAGE_SHIFT
>  	.endm
>  
>  /*
> diff --git a/arch/arm/include/asm/thread_info.h b/arch/arm/include/asm/thread_info.h
> index f989d7c..f85d2b0 100644
> --- a/arch/arm/include/asm/thread_info.h
> +++ b/arch/arm/include/asm/thread_info.h
> @@ -14,9 +14,10 @@
>  
>  #include <linux/compiler.h>
>  #include <asm/fpstate.h>
> +#include <asm/page.h>
>  
>  #define THREAD_SIZE_ORDER	1
> -#define THREAD_SIZE		8192
> +#define THREAD_SIZE		(PAGE_SIZE << THREAD_SIZE_ORDER)
>  #define THREAD_START_SP		(THREAD_SIZE - 8)
>  
>  #ifndef __ASSEMBLY__
> -- 
> 1.8.5.5
> 
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