linux-kernel - Re: [PATCH AUTOSEL 4.4 3/5] of: Fix reserved-memory overlap detection

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Date:   Tue, 3 Nov 2020 12:11:10 +0100
From:   Vincent Whitchurch <vincent.whitchurch@...s.com>
To:     Sasha Levin <sashal@...nel.org>
CC:     "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "stable@...r.kernel.org" <stable@...r.kernel.org>,
        Rob Herring <robh@...nel.org>,
        "devicetree@...r.kernel.org" <devicetree@...r.kernel.org>
Subject: Re: [PATCH AUTOSEL 4.4 3/5] of: Fix reserved-memory overlap detection

On Tue, Nov 03, 2020 at 02:21:16AM +0100, Sasha Levin wrote:
> From: Vincent Whitchurch <vincent.whitchurch@...s.com>
> 
> [ Upstream commit ca05f33316559a04867295dd49f85aeedbfd6bfd ]
> 
> The reserved-memory overlap detection code fails to detect overlaps if
> either of the regions starts at address 0x0.  The code explicitly checks
> for and ignores such regions, apparently in order to ignore dynamically
> allocated regions which have an address of 0x0 at this point.  These
> dynamically allocated regions also have a size of 0x0 at this point, so
> fix this by removing the check and sorting the dynamically allocated
> regions ahead of any static regions at address 0x0.
> 
> For example, there are two overlaps in this case but they are not
> currently reported:
> 
> 	foo@0 {
> 	        reg = <0x0 0x2000>;
> 	};
> 
> 	bar@0 {
> 	        reg = <0x0 0x1000>;
> 	};
> 
> 	baz@...0 {
> 	        reg = <0x1000 0x1000>;
> 	};
> 
> 	quux {
> 	        size = <0x1000>;
> 	};
> 
> but they are after this patch:
> 
>  OF: reserved mem: OVERLAP DETECTED!
>  bar@0 (0x00000000--0x00001000) overlaps with foo@0 (0x00000000--0x00002000)
>  OF: reserved mem: OVERLAP DETECTED!
>  foo@0 (0x00000000--0x00002000) overlaps with baz@...0 (0x00001000--0x00002000)
> 
> Signed-off-by: Vincent Whitchurch <vincent.whitchurch@...s.com>
> Link: https://lore.kernel.org/r/ded6fd6b47b58741aabdcc6967f73eca6a3f311e.1603273666.git-series.vincent.whitchurch@axis.com
> Signed-off-by: Rob Herring <robh@...nel.org>
> Signed-off-by: Sasha Levin <sashal@...nel.org>

I'm not sure if this really needs to be backported.  It's only fixing
what is essentially a minor debugging feature.