Re: [edk2-devel] [PATCH] RedfishPkg/JsonLib: fix JsonObjectGetValue issue

["Chang, Abner via groups.io" <abner.chang=amd.com@groups.io>]

[AMD Official Use Only - General]

Hi Nickle,
As we may use a protocol that provide the JSON interface for other packages or drivers, could you please have a comment around the hardcoded number says the hardcoded number would be removed when we have a protocol on top of jansson lib? People can still have the real hashtable seed if they use library directly.

Thanks
Abner

> -----Original Message-----
> From: Igor Kulchytskyy <igork@ami.com>
> Sent: Wednesday, September 20, 2023 11:19 PM
> To: Nickle Wang <nicklew@nvidia.com>; devel@edk2.groups.io
> Cc: Chang, Abner <Abner.Chang@amd.com>; Nick Ramirez
> <nramirez@nvidia.com>
> Subject: RE: [EXTERNAL] [PATCH] RedfishPkg/JsonLib: fix JsonObjectGetValue
> issue
>
> Caution: This message originated from an External Source. Use proper caution
> when opening attachments, clicking links, or responding.
>
>
> Reviewed-by: Igor Kulchytskyy <igork@ami.com>
>
> Regards,
> Igor
> -----Original Message-----
> From: Nickle Wang <nicklew@nvidia.com>
> Sent: Monday, September 18, 2023 9:09 AM
> To: devel@edk2.groups.io
> Cc: Abner Chang <abner.chang@amd.com>; Igor Kulchytskyy
> <igork@ami.com>; Nick Ramirez <nramirez@nvidia.com>
> Subject: [EXTERNAL] [PATCH] RedfishPkg/JsonLib: fix JsonObjectGetValue
> issue
>
>
> **CAUTION: The e-mail below is from an external source. Please exercise
> caution before opening attachments, clicking links, or following guidance.**
>
> JsonObjectGetValue() cannot find corresponding JSON value
> when the EDKII_JSON_VALUE object is created by another UEFI
> driver. This is because "hashtable_seed" is initialized by
> current time while JsonLib is loaded. So, "hashtable_seed"
> will be different in each individual UEFI driver.
>
> Signed-off-by: Nickle Wang <nicklew@nvidia.com>
> Cc: Abner Chang <abner.chang@amd.com>
> Cc: Igor Kulchytskyy <igork@ami.com>
> Cc: Nick Ramirez <nramirez@nvidia.com>
> ---
>  RedfishPkg/Library/JsonLib/JsonLib.inf |  1 +
>  RedfishPkg/Library/JsonLib/JsonLib.c   | 34
> ++++++++++++++++++++++++++
>  2 files changed, 35 insertions(+)
>
> diff --git a/RedfishPkg/Library/JsonLib/JsonLib.inf
> b/RedfishPkg/Library/JsonLib/JsonLib.inf
> index 9d52a622e13a..b0d1bcac7cb3 100644
> --- a/RedfishPkg/Library/JsonLib/JsonLib.inf
> +++ b/RedfishPkg/Library/JsonLib/JsonLib.inf
> @@ -15,6 +15,7 @@
>    MODULE_TYPE                    = DXE_DRIVER
>    VERSION_STRING                 = 1.0
>    LIBRARY_CLASS                  = JsonLib|DXE_DRIVER UEFI_APPLICATION
> UEFI_DRIVER
> +  CONSTRUCTOR                    = JsonLibConstructor
>
>  #
>  #  VALID_ARCHITECTURES           = IA32 X64 ARM AARCH64 RISCV64
> diff --git a/RedfishPkg/Library/JsonLib/JsonLib.c
> b/RedfishPkg/Library/JsonLib/JsonLib.c
> index 9b758b940293..a7ec2ab217a6 100644
> --- a/RedfishPkg/Library/JsonLib/JsonLib.c
> +++ b/RedfishPkg/Library/JsonLib/JsonLib.c
> @@ -19,6 +19,8 @@
>
>  #include "jansson.h"
>
> +extern volatile UINT32  hashtable_seed;
> +
>  /**
>    The function is used to initialize a JSON value which contains a new JSON
> array,
>    or NULL on error. Initially, the array is empty.
> @@ -1138,3 +1140,35 @@ JsonGetType (
>  {
>    return (EDKII_JSON_TYPE)(((json_t *)JsonValue)->type);
>  }
> +
> +/**
> +  JSON Library constructor.
> +
> +  @param ImageHandle     The image handle.
> +  @param SystemTable     The system table.
> +
> +  @retval  EFI_SUCCESS  Protocol listener is registered successfully.
> +
> +**/
> +EFI_STATUS
> +EFIAPI
> +JsonLibConstructor (
> +  IN EFI_HANDLE        ImageHandle,
> +  IN EFI_SYSTEM_TABLE  *SystemTable
> +  )
> +{
> +  //
> +  // hashtable_seed is initalized by current time while JsonLib is loaded.
> +  // Due to above mechanism, hashtable_seed will be different in each
> individual
> +  // UEFI driver. As the result, the hash of same key in different UEFI driver
> +  // would be different. This breaks JsonObjectGetValue() because
> +  // JsonObjectGetValue() won't be able to find corresponding JSON value if
> +  // this EDKII_JSON_VALUE is created by another UEFI driver.
> +  //
> +  // Initial the seed to a fixed magic value for JsonLib to be working in all
> +  // UEFI drivers.
> +  //
> +  hashtable_seed = 0xFDAE2143;
> +
> +  return EFI_SUCCESS;
> +}
> --
> 2.17.1
>
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