linux-kernel - Re: [PATCH -tip] x86: smp_scan_config - use signed long as scan area size

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Message-ID: <20090821160426.GA17731@elte.hu>
Date:	Fri, 21 Aug 2009 18:04:26 +0200
From:	Ingo Molnar <mingo@...e.hu>
To:	Cyrill Gorcunov <gorcunov@...nvz.org>
Cc:	"H. Peter Anvin" <hpa@...or.com>,
	Thomas Gleixner <tglx@...utronix.de>,
	LKML <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH -tip] x86: smp_scan_config - use signed long as scan
	area size


* Cyrill Gorcunov <gorcunov@...nvz.org> wrote:

> Unsigned value potentially could be overlapped
> if length parameter is that: length % 16 != 0.
> 
> This is not a problem at moment since all values
> we pass now are 16 divisible (0x400 and 0x10000).
> 
> Though there is no need unsigned value anyway.
> Max range pointed out by MP specification is
> in kilobytes so plain "signed long" is enough.
> 
> This allow us to be on a safe side.
> 
> Signed-off-by: Cyrill Gorcunov <gorcunov@...nvz.org>
> ---
> 
> (I doubt if we ever will need to scan 1G of physical
>  memory with 16 byte step at booting procedure 'xcept
>  memtest case)
> 
> Please review. Not sure if the patch is that worth
> but anyway :)
> 
>  arch/x86/kernel/mpparse.c |    2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> Index: linux-2.6.git/arch/x86/kernel/mpparse.c
> =====================================================================
> --- linux-2.6.git.orig/arch/x86/kernel/mpparse.c
> +++ linux-2.6.git/arch/x86/kernel/mpparse.c
> @@ -705,7 +705,7 @@ static void __init smp_reserve_bootmem(s
>  #endif
>  }
>  
> -static int __init smp_scan_config(unsigned long base, unsigned long length,
> +static int __init smp_scan_config(unsigned long base, long length,
>  				  unsigned reserve)
>  {
>  	unsigned int *bp = phys_to_virt(base);

Hm, does a BUILD_BUG_ON((length & 15) != 0) line catch incorrectly 
aligned length parameters?

	Ingo
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