Re: [PATCH v2 06/21] DynamicTablesPkg: Set EndTag's Checksum if RdList is modified

["Sami Mujawar" <sami.mujawar@arm.com>]

Hi Pierre,

Thank you for this patch.

Reviewed-by: Sami Mujawar <sami.mujawar@arm.com>

Regards,

Sami Mujawar

On 07/10/2021 04:31 PM, Pierre.Gondois@arm.com wrote:
> From: Pierre Gondois <Pierre.Gondois@arm.com>
>
> ACPI 6.4, s6.4.2.9 "End Tag":
> "This checksum is generated such that adding it to the sum of all the data
> bytes will produce a zero sum."
> "If the checksum field is zero, the resource data is treated as if the
> checksum operation succeeded. Configuration proceeds normally."
>
> To avoid re-computing checksums, if a new resource data elements is
> added/removed/modified in a list of resource data elements, the AmlLib
> resets the checksum to 0.
>
> This patch also refactors the AmlAppendRdNode() function by getting the
> last Resource Data node directly instead of iterating over all the
> elements of the list of Resource Data node.
>
> Signed-off-by: Pierre Gondois <Pierre.Gondois@arm.com>
> ---
>   .../Common/AmlLib/Tree/AmlNodeInterface.c     |  7 ++
>   .../Library/Common/AmlLib/Tree/AmlTree.c      | 72 +++++++------------
>   2 files changed, 34 insertions(+), 45 deletions(-)
>
> diff --git a/DynamicTablesPkg/Library/Common/AmlLib/Tree/AmlNodeInterface.c b/DynamicTablesPkg/Library/Common/AmlLib/Tree/AmlNodeInterface.c
> index 870346c40a5d..f91bc5fd55d2 100644
> --- a/DynamicTablesPkg/Library/Common/AmlLib/Tree/AmlNodeInterface.c
> +++ b/DynamicTablesPkg/Library/Common/AmlLib/Tree/AmlNodeInterface.c
> @@ -513,6 +513,13 @@ AmlUpdateDataNode (
>           ASSERT (0);
>           return EFI_INVALID_PARAMETER;
>         }
> +
> +      Status = AmlSetRdListCheckSum (ParentNode, 0);
> +      if (EFI_ERROR (Status)) {
> +        ASSERT (0);
> +        return Status;
> +      }
> +
>         break;
>       }
>       case EAmlNodeDataTypeFieldPkgLen:
> diff --git a/DynamicTablesPkg/Library/Common/AmlLib/Tree/AmlTree.c b/DynamicTablesPkg/Library/Common/AmlLib/Tree/AmlTree.c
> index 0931e751709e..2772e915f468 100644
> --- a/DynamicTablesPkg/Library/Common/AmlLib/Tree/AmlTree.c
> +++ b/DynamicTablesPkg/Library/Common/AmlLib/Tree/AmlTree.c
> @@ -566,8 +566,7 @@ AmlAppendRdNode (
>     )
>   {
>     EFI_STATUS        Status;
> -  AML_DATA_NODE   * CurrRdNode;
> -  AML_RD_HEADER     RdDataType;
> +  AML_DATA_NODE   * LastRdNode;
>
>     if (!AmlNodeCompareOpCode (BufferOpNode, AML_BUFFER_OP, 0)  ||
>         !IS_AML_DATA_NODE (NewRdNode)                           ||
> @@ -576,56 +575,39 @@ AmlAppendRdNode (
>       return EFI_INVALID_PARAMETER;
>     }
>
> -  // Get the first Resource data node in the variable list of
> -  // argument of the BufferOp node.
> -  CurrRdNode = (AML_DATA_NODE*)AmlGetNextVariableArgument (
> +  // To avoid re-computing checksums, if a new resource data elements is
> +  // added/removed/modified in a list of resource data elements, the AmlLib
> +  // resets the checksum to 0.
> +  // It is possible to have only one Resource Data in a BufferOp with
> +  // no EndTag, but it should not be possible to add a new Resource Data
> +  // in the list in this case.
> +  Status = AmlSetRdListCheckSum (BufferOpNode, 0);
> +  if (EFI_ERROR (Status)) {
> +    ASSERT (0);
> +    return Status;
> +  }
> +
> +  // Get the last Resource data node in the variable list of argument of the
> +  // BufferOp node. This must be an EndTag, otherwise setting the checksum
> +  // would have failed.
> +  LastRdNode = (AML_DATA_NODE*)AmlGetPreviousVariableArgument (
>                                    (AML_NODE_HEADER*)BufferOpNode,
>                                    NULL
>                                    );
> -  if ((CurrRdNode == NULL)             ||
> -      !IS_AML_DATA_NODE (CurrRdNode)   ||
> -      (CurrRdNode->DataType != EAmlNodeDataTypeResourceData)) {
> +  if ((LastRdNode == NULL)             ||
> +      !IS_AML_DATA_NODE (LastRdNode)   ||
> +      (LastRdNode->DataType != EAmlNodeDataTypeResourceData)) {
>       ASSERT (0);
>       return EFI_INVALID_PARAMETER;
>     }
>
> -  // Iterate through the Resource Data nodes to find the End Tag.
> -  while (TRUE) {
> -    Status = AmlGetResourceDataType (CurrRdNode, &RdDataType);
> -    if (EFI_ERROR (Status)) {
> -      ASSERT (0);
> -      return Status;
> -    }
> -
> -    // If the Resource Data is an End Tag,
> -    // add the new node before and return.
> -    if (AmlRdCompareDescId (
> -          &RdDataType,
> -          AML_RD_BUILD_SMALL_DESC_ID (ACPI_SMALL_END_TAG_DESCRIPTOR_NAME))) {
> -      Status = AmlVarListAddBefore (
> -                 (AML_NODE_HEADER*)CurrRdNode,
> -                 (AML_NODE_HEADER*)NewRdNode)
> -                 ;
> -      if (EFI_ERROR (Status)) {
> -        ASSERT (0);
> -      }
> -      return Status;
> -    }
> -
> -    // Get the next Resource Data node.
> -    // If this was the last node and no End Tag was found, return error.
> -    // It is possible to have only one Resource Data in a BufferOp,
> -    // but it should not be possible to add a new Resource Data in the list
> -    // in this case.
> -    CurrRdNode = (AML_DATA_NODE*)AmlGetSiblingVariableArgument (
> -                                   (AML_NODE_HEADER*)CurrRdNode
> -                                   );
> -    if (!IS_AML_DATA_NODE (CurrRdNode)  ||
> -        (CurrRdNode->DataType != EAmlNodeDataTypeResourceData)) {
> -      ASSERT (0);
> -      return EFI_INVALID_PARAMETER;
> -    }
> -  } // while
> +  // Add NewRdNode before the EndTag.
> +  Status = AmlVarListAddBefore (
> +             (AML_NODE_HEADER*)LastRdNode,
> +             (AML_NODE_HEADER*)NewRdNode)
> +             ;
> +  ASSERT_EFI_ERROR (Status);
> +  return Status;
>   }
>
>   /** Replace the fixed argument at the Index of the ParentNode with the NewNode.

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