linux-kernel - Re: [PATCH] x86: Remove excess calculations for heap_end

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Message-ID: <20141226143532.GB28213@newt.localdomain>
Date:	Fri, 26 Dec 2014 06:35:32 -0800
From:	Jeremiah Mahler <jmmahler@...il.com>
To:	Alexander Kuleshov <kuleshovmail@...il.com>
Cc:	"H. Peter Anvin" <hpa@...or.com>, x86@...nel.org,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH] x86: Remove excess calculations for heap_end_ptr

Alexander,

On Fri, Dec 26, 2014 at 06:22:42PM +0600, Alexander Kuleshov wrote:
> heap_end_ptr default value defined as _end+STACK_SZE-512, but
                                            STACK_SIZE 

> STACK_SIZE is already 512.
> 
> Signed-off-by: Alexander Kuleshov <kuleshovmail@...il.com>
> ---
>  arch/x86/boot/header.S | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/arch/x86/boot/header.S b/arch/x86/boot/header.S
> index 16ef025..c69b870 100644
> --- a/arch/x86/boot/header.S
> +++ b/arch/x86/boot/header.S
> @@ -342,7 +342,7 @@ ramdisk_size:	.long	0		# its size in bytes
>  bootsect_kludge:
>  		.long	0		# obsolete
>  
> -heap_end_ptr:	.word	_end+STACK_SIZE-512
> +heap_end_ptr:	.word	_end
>  					# (Header version 0x0201 or later)
>  					# space from here (exclusive) down to
>  					# end of setup code can be used by setup

So right now STACK_SIZE happens to be 512 so STACK_SIZE-512 is zero.
What happens if someone changes the size of STACK_SIZE?

This change doesn't fix any problem right now and creates potential
problems in the future.

> -- 
> 2.2.1.201.gbbcefff
> 
> --
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-- 
- Jeremiah Mahler
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