linux-kernel - Re: [PATCH] of: Fix reserved-memory overlap detection

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Date:   Tue, 20 Oct 2020 08:00:14 -0500
From:   Rob Herring <robh+dt@...nel.org>
To:     Vincent Whitchurch <vincent.whitchurch@...s.com>
Cc:     Frank Rowand <frowand.list@...il.com>, kernel@...s.com,
        Mitchel Humpherys <mitchelh@...eaurora.org>,
        devicetree@...r.kernel.org,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] of: Fix reserved-memory overlap detection

On Tue, Oct 20, 2020 at 2:36 AM Vincent Whitchurch
<vincent.whitchurch@...s.com> wrote:
>
> The reserved-memory overlap detection code fails to detect overlaps if
> either of the regions starts at address 0x0.  For some reason the code
> explicitly checks for and ignores such regions, but this check looks
> invalid.  Remove the check and fix this detection.

Wouldn't 'base' be 0 for nodes that have a 'size' and no address? The
base in those cases isn't set until later when
__reserved_mem_alloc_size() is called.

>
> For example, no overlap is currently reported for this case:
>
>         foo@0 {
>                 reg = <0x0000 0x2000>;
>         };
>
>         bar@...0 {
>                 reg = <0x1000 0x1000>;
>         };
>
> but it is after this patch:
>
>  OF: reserved mem: OVERLAP DETECTED!
>  foo@0 (0x00000000--0x00002000) overlaps with bar@...0 (0x00001000--0x00002000)
>
> Signed-off-by: Vincent Whitchurch <vincent.whitchurch@...s.com>
> ---
>  drivers/of/of_reserved_mem.c | 3 +--
>  1 file changed, 1 insertion(+), 2 deletions(-)
>
> diff --git a/drivers/of/of_reserved_mem.c b/drivers/of/of_reserved_mem.c
> index 46b9371c8a33..1c5259e3e81f 100644
> --- a/drivers/of/of_reserved_mem.c
> +++ b/drivers/of/of_reserved_mem.c
> @@ -217,8 +217,7 @@ static void __init __rmem_check_for_overlap(void)
>
>                 this = &reserved_mem[i];
>                 next = &reserved_mem[i + 1];
> -               if (!(this->base && next->base))
> -                       continue;
> +
>                 if (this->base + this->size > next->base) {
>                         phys_addr_t this_end, next_end;
>
> --
> 2.28.0
>