linux-hardening - Re: [PATCH v4 1/2] dt-bindings: ramoops: Inherit reserve memory property

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Date:   Fri, 27 Jan 2023 21:03:15 +0100
From:   Krzysztof Kozlowski <krzysztof.kozlowski@...aro.org>
To:     Mukesh Ojha <quic_mojha@...cinc.com>,
        linux-hardening@...r.kernel.org, linux-doc@...r.kernel.org,
        linux-kernel@...r.kernel.org, devicetree@...r.kernel.org
Cc:     Kees Cook <keescook@...omium.org>, Tony Luck <tony.luck@...el.com>,
        "Guilherme G . Piccoli" <gpiccoli@...lia.com>,
        Rob Herring <robh+dt@...nel.org>,
        Krzysztof Kozlowski <krzysztof.kozlowski+dt@...aro.org>
Subject: Re: [PATCH v4 1/2] dt-bindings: ramoops: Inherit reserve memory
 property

On 27/01/2023 17:00, Mukesh Ojha wrote:
> The reserved memory region for ramoops is assumed to be at a
> fixed and known location when read from the devicetree. This
> is not desirable in an environment where it is preferred the
> region to be dynamically allocated at runtime, as opposed to
> being fixed at compile time.
> 
> So, update the ramoops binding by inheriting some reserve memory
> property to allocate the ramoops region dynamically.

Where is the update which adds "inheriting"?

> 
> Cc: Kees Cook <keescook@...omium.org>
> Cc: Tony Luck <tony.luck@...el.com>
> Cc: Guilherme G. Piccoli <gpiccoli@...lia.com>
> Cc: Rob Herring <robh+dt@...nel.org>
> Cc: Krzysztof Kozlowski <krzysztof.kozlowski+dt@...aro.org>
> Signed-off-by: Mukesh Ojha <quic_mojha@...cinc.com>
> ---
> Changes in v4:
>  - Addressed comment made by Krzysztof on ramoops node name.
> 
> Changes in v3:
>  - Fixed yaml error and updated commit text as per comment.
> 
> Change in v2:
>   - Added this patch as per changes going to be done in patch 3/3
> 
>  .../bindings/reserved-memory/ramoops.yaml          | 34 ++++++++++++++++++++--
>  1 file changed, 32 insertions(+), 2 deletions(-)
> 
> diff --git a/Documentation/devicetree/bindings/reserved-memory/ramoops.yaml b/Documentation/devicetree/bindings/reserved-memory/ramoops.yaml
> index 0391871..8741626 100644
> --- a/Documentation/devicetree/bindings/reserved-memory/ramoops.yaml
> +++ b/Documentation/devicetree/bindings/reserved-memory/ramoops.yaml
> @@ -10,7 +10,8 @@ description: |
>    ramoops provides persistent RAM storage for oops and panics, so they can be
>    recovered after a reboot. This is a child-node of "/reserved-memory", and
>    is named "ramoops" after the backend, rather than "pstore" which is the
> -  subsystem.
> +  subsystem. This region can be reserved both statically or dynamically by
> +  using appropriate property in device tree.
>  
>    Parts of this storage may be set aside for other persistent log buffers, such
>    as kernel log messages, or for optional ECC error-correction data.  The total
> @@ -112,7 +113,13 @@ unevaluatedProperties: false
>  
>  required:
>    - compatible
> -  - reg

This is okay, but:

> +
> +oneOf:
> +  - required:
> +      - reg
> +
> +  - required:
> +      - size

I now keep wondering - why do you need this?

>  
>  anyOf:
>    - required: [record-size]
> @@ -142,3 +149,26 @@ examples:
>              };
>          };
>      };
> +
> +  - |
> +    / {
> +        compatible = "foo";
> +        model = "foo";
> +        #address-cells = <1>;
> +        #size-cells = <1>;
> +
> +        reserved-memory {
> +            #address-cells = <1>;
> +            #size-cells = <1>;
> +            ranges;
> +
> +            ramoops_region: ramoops {
> +                compatible = "ramoops";
> +                alloc-ranges = <0x00000000 0xffffffff>;
> +                size = <0x0 0x10000>;       /* 64kB */
> +                console-size = <0x8000>;    /* 32kB */
> +                record-size = <0x400>;      /*  1kB */
> +                ecc-size = <16>;
> +            };
> +        };
> +    };

This example does not bring anything new for the ramoops. It's an
example for reserved-memory to show usage with alloc-ranges. There is
nothing useful here in terms of ramoops, so I think it should be dropped.

Best regards,
Krzysztof