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 for kexec@lists.infradead.org; Tue, 04 Mar 2014 04:03:57 +0000
Date: Tue, 4 Mar 2014 13:03:31 +0900
From: Simon Horman <horms@verge.net.au>
Subject: Re: PATCH: bug in locate_hole()
Message-ID: <20140304040331.GG18200@verge.net.au>
References: <CAMBSHm_fvPTjdEwgVdyMGPi=3et+JEP-G5TNV986yXWYw35YYw@mail.gmail.com>
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To: Matthew Fleming <mdf356@gmail.com>
Cc: kexec@lists.infradead.org

Thanks Matthew.

Could you provide a signed-off-by line?

On Mon, Mar 03, 2014 at 04:34:35PM -0800, Matthew Fleming wrote:
> In upgrading to kexec-tools 2.0.5 I first got the error "Overlapping
> memory segments at 0xbeff000"
> 
> Adding some debugging I found locate_hole was returning incorrect
> values.  The below is from the debug I added:
> 
> XXXMDF: look for hole size 100000, cur range [52b3000, bffffff] size 6d4cfff
> XXXMDF: look for hole memsz=100000, found beff000
> 
> Hmm, if we wanted 0x100000 bytes ending at 0xbffffff, that should be
> 0xbf00000, not 0xbef000.  Continuing to the second invocation:
> 
> XXXMDF: look for hole size 1000, cur range [52b3000, befefff] size 6c4bfff
> XXXMDF: look for hole size 1000, cur range [bfff000, bffffff] size fff
> XXXMDF: look for hole memsz=1000, found bffe000
> 
> Now we die with overlapping ranges, since the 0x100000 bytes at
> 0xbeff000 overlaps 0x1000 bytes at 0xbffe000.
> 
> The attached patch fixes the off-by-one that causes the later overlap.
> 
> Thanks,
> matthew

> --- kexec.c.orig	2014-03-03 16:08:53.289844106 -0800
> +++ kexec.c	2014-03-03 16:09:04.960844107 -0800
> @@ -272,17 +272,17 @@ unsigned long locate_hole(struct kexec_i
>  		}
>  		/* Is there enough space left so we can use it? */
>  		size = end - start;
>  		if (!hole_size || size >= hole_size - 1) {
>  			if (hole_end > 0) {
>  				hole_base = start;
>  				break;
>  			} else {
> -				hole_base = _ALIGN_DOWN(end - hole_size,
> +				hole_base = _ALIGN_DOWN(end - hole_size + 1,
>  					hole_align);
>  			}
>  		}
>  	}
>  	free(mem_range);
>  	if (hole_base == ULONG_MAX) {
>  		fprintf(stderr, "Could not find a free area of memory of "
>  			"0x%lx bytes...\n", hole_size);

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