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

["Igor Kulchytskyy via groups.io" <igork=ami.com@groups.io>]

Hi Nickle,
Does that mean, that json_object_seed function is useless anymore with those changes?
And there is no need for other module to call json_object_seed?
Thank you,
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


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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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