linux-hardening - Re: [PATCH v4 08/21] dt-bindings: reserved-memory: Add qcom,ramoops binding

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Message-ID: <87ba1c2d-fa0b-4ac5-ba79-b3556101b612@quicinc.com>
Date:   Wed, 28 Jun 2023 19:40:54 +0530
From:   Pavan Kondeti <quic_pkondeti@...cinc.com>
To:     Mukesh Ojha <quic_mojha@...cinc.com>
CC:     <corbet@....net>, <agross@...nel.org>, <andersson@...nel.org>,
        <konrad.dybcio@...aro.org>, <robh+dt@...nel.org>,
        <krzysztof.kozlowski+dt@...aro.org>, <conor+dt@...nel.org>,
        <keescook@...omium.org>, <tony.luck@...el.com>,
        <gpiccoli@...lia.com>, <mathieu.poirier@...aro.org>,
        <catalin.marinas@....com>, <will@...nel.org>,
        <linus.walleij@...aro.org>, <andy.shevchenko@...il.com>,
        <linux-doc@...r.kernel.org>, <linux-kernel@...r.kernel.org>,
        <linux-arm-msm@...r.kernel.org>, <devicetree@...r.kernel.org>,
        <linux-hardening@...r.kernel.org>,
        <linux-remoteproc@...r.kernel.org>,
        <linux-arm-kernel@...ts.infradead.org>,
        <linux-gpio@...r.kernel.org>
Subject: Re: [PATCH v4 08/21] dt-bindings: reserved-memory: Add qcom,ramoops
 binding

On Wed, Jun 28, 2023 at 06:04:35PM +0530, Mukesh Ojha wrote:
> Qualcomm ramoops minidump logger provide a means of storing
> the ramoops data to some dynamically reserved memory instead
> of traditionally implemented ramoops where the region should
> be statically fixed ram region. Its device tree binding
> would be exactly same as ramoops device tree binding and is
> going to contain traditional ramoops frontend data and this
> content will be collected via Qualcomm minidump infrastructure
> provided from the boot firmware.
> 
> Signed-off-by: Mukesh Ojha <quic_mojha@...cinc.com>
> ---
>  .../devicetree/bindings/soc/qcom/qcom,ramoops.yaml | 126 +++++++++++++++++++++
>  1 file changed, 126 insertions(+)
>  create mode 100644 Documentation/devicetree/bindings/soc/qcom/qcom,ramoops.yaml
> 
> diff --git a/Documentation/devicetree/bindings/soc/qcom/qcom,ramoops.yaml b/Documentation/devicetree/bindings/soc/qcom/qcom,ramoops.yaml
> new file mode 100644
> index 000000000000..b1fdcf3f8ad4
> --- /dev/null
> +++ b/Documentation/devicetree/bindings/soc/qcom/qcom,ramoops.yaml
> @@ -0,0 +1,126 @@
> +# SPDX-License-Identifier: (GPL-2.0 OR BSD-2-Clause)
> +%YAML 1.2
> +---
> +$id: "http://devicetree.org/schemas/soc/qcom/qcom,ramoops.yaml#"
> +$schema: "http://devicetree.org/meta-schemas/core.yaml#"
> +
> +title: Qualcomm Ramoops minidump logger
> +
> +description: |
> +  Qualcomm ramoops minidump logger provide a means of storing the ramoops
> +  data to some dynamically reserved memory instead of traditionally
> +  implemented ramoops where the region should be statically fixed ram
> +  region. Because of its similarity with ramoops it will also have same
> +  set of property what ramoops have it in its schema and is going to
> +  contain traditional ramoops frontend data and this region will be
> +  collected via Qualcomm minidump infrastructure provided from the
> +  boot firmware.
> +
> +maintainers:
> +  - Mukesh Ojha <quic_mojha@...cinc.com>
> +
> +properties:
> +  compatible:
> +    items:
> +      - enum:
> +          - qcom,sm8450-ramoops
> +      - const: qcom,ramoops
> +
> +  memory-region:
> +    maxItems: 1
> +    description: handle to memory reservation for qcom,ramoops region.
> +
> +  ecc-size:
> +    $ref: /schemas/types.yaml#/definitions/uint32
> +    description: enables ECC support and specifies ECC buffer size in bytes
> +    default: 0 # no ECC
> +
> +  record-size:
> +    $ref: /schemas/types.yaml#/definitions/uint32
> +    description: maximum size in bytes of each kmsg dump
> +    default: 0
> +
> +  console-size:
> +    $ref: /schemas/types.yaml#/definitions/uint32
> +    description: size in bytes of log buffer reserved for kernel messages
> +    default: 0
> +
> +  ftrace-size:
> +    $ref: /schemas/types.yaml#/definitions/uint32
> +    description: size in bytes of log buffer reserved for function tracing and profiling
> +    default: 0
> +
> +  pmsg-size:
> +    $ref: /schemas/types.yaml#/definitions/uint32
> +    description: size in bytes of log buffer reserved for userspace messages
> +    default: 0
> +
> +  mem-type:
> +    $ref: /schemas/types.yaml#/definitions/uint32
> +    description: if present, sets the type of mapping is to be used to map the reserved region.
> +    default: 0
> +    oneOf:
> +      - const: 0
> +        description: write-combined
> +      - const: 1
> +        description: unbuffered
> +      - const: 2
> +        description: cached
> +
> +  max-reason:
> +    $ref: /schemas/types.yaml#/definitions/uint32
> +    default: 2 # log oopses and panics
> +    maximum: 0x7fffffff
> +    description: |
> +      If present, sets maximum type of kmsg dump reasons to store.
> +      This can be set to INT_MAX to store all kmsg dumps.
> +      See include/linux/kmsg_dump.h KMSG_DUMP_* for other kmsg dump reason values.
> +      Setting this to 0 (KMSG_DUMP_UNDEF), means the reason filtering will be
> +      controlled by the printk.always_kmsg_dump boot param.
> +      If unset, it will be 2 (KMSG_DUMP_OOPS), otherwise 5 (KMSG_DUMP_MAX).
> +
> +  flags:
> +    $ref: /schemas/types.yaml#/definitions/uint32
> +    default: 0
> +    description: |
> +      If present, pass ramoops behavioral flags
> +      (see include/linux/pstore_ram.h RAMOOPS_FLAG_* for flag values).
> +
> +  no-dump-oops:
> +    deprecated: true
> +    type: boolean
> +    description: |
> +      Use max_reason instead. If present, and max_reason is not specified,
> +      it is equivalent to max_reason = 1 (KMSG_DUMP_PANIC).
> +
> +  unbuffered:
> +    deprecated: true
> +    type: boolean
> +    description: |
> +      Use mem_type instead. If present, and mem_type is not specified,
> +      it is equivalent to mem_type = 1 and uses unbuffered mappings to map
> +      the reserved region (defaults to buffered mappings mem_type = 0).
> +      If both are specified -- "mem_type" overrides "unbuffered".
> +

Most of the properties you added here are already documented at
Documentation/devicetree/bindings/reserved-memory/ramoops.yaml 

Can't we just reference them here? would something like work?

max-reason:
  $ref: "../../reserved-memory/ramoops.yaml#/properties/max-reason

> +unevaluatedProperties: false
> +

will there be any additional properties be added dynamically? if not,
should not we use "additionalProperties: false" here?

Thanks,
Pavan