StandaloneMmPkg/Core: Limit FwVol encapsulation section recursion

MmCoreFfsFindMmDriver() is called recursively for encapsulation sections.
Currently this recursion is not limited. Introduce a new PCD
(fixed-at-build, or patchable-in-module), and make MmCoreFfsFindMmDriver()
track the section nesting depth against that PCD.

Cc: Laszlo Ersek <lersek@redhat.com>
Cc: Ard Biesheuvel <ardb+tianocore@kernel.org>
Cc: Sami Mujawar <sami.mujawar@arm.com>
Cc: Ray Ni <ray.ni@intel.com>
Signed-off-by: Wei6 Xu <wei6.xu@intel.com>
Reviewed-by: Ray Ni <ray.ni@intel.com>
Reviewed-by: Laszlo Ersek <lersek@redhat.com>

StandaloneMmPkg/Core/StandaloneMmCore.h

@@ -846,6 +846,32 @@ DumpMmramInfo (
   VOID
   );
 
+/**
+  Given the pointer to the Firmware Volume Header find the
+  MM driver and return its PE32 image.
+
+  @param [in] FwVolHeader   Pointer to memory mapped FV
+  @param [in] Depth         Nesting depth of encapsulation sections. Callers
+                            different from MmCoreFfsFindMmDriver() are
+                            responsible for passing in a zero Depth.
+
+  @retval  EFI_SUCCESS            Success.
+  @retval  EFI_INVALID_PARAMETER  Invalid parameter.
+  @retval  EFI_NOT_FOUND          Could not find section data.
+  @retval  EFI_OUT_OF_RESOURCES   Out of resources.
+  @retval  EFI_VOLUME_CORRUPTED   Firmware volume is corrupted.
+  @retval  EFI_UNSUPPORTED        Operation not supported.
+  @retval  EFI_ABORTED            Recursion aborted because Depth has been
+                                  greater than or equal to
+                                  PcdFwVolMmMaxEncapsulationDepth.
+
+**/
+EFI_STATUS
+MmCoreFfsFindMmDriver (
+  IN  EFI_FIRMWARE_VOLUME_HEADER  *FwVolHeader,
+  IN  UINT32                      Depth
+  );
+
 extern UINTN                 mMmramRangeCount;
 extern EFI_MMRAM_DESCRIPTOR  *mMmramRanges;
 extern EFI_SYSTEM_TABLE      *mEfiSystemTable;