Add the newly introduced EfiAllocatePeiAccessiblePages() routine which
allocates memory in a way that guarantees that PEI can access it after
a warm reboot.

Contributed-under: TianoCore Contribution Agreement 1.1
Signed-off-by: Ard Biesheuvel <ard.biesheuvel@linaro.org>
---
 IntelFrameworkPkg/Library/FrameworkUefiLib/UefiLib.c | 48 ++++++++++++++++++++
 1 file changed, 48 insertions(+)

diff --git a/IntelFrameworkPkg/Library/FrameworkUefiLib/UefiLib.c b/IntelFrameworkPkg/Library/FrameworkUefiLib/UefiLib.c
index 443a73917215..a488fe780b04 100644
--- a/IntelFrameworkPkg/Library/FrameworkUefiLib/UefiLib.c
+++ b/IntelFrameworkPkg/Library/FrameworkUefiLib/UefiLib.c
@@ -1687,3 +1687,51 @@ EfiLocateProtocolBuffer (
 
   return EFI_SUCCESS;
 }
+
+/**
+  Allocates one or more 4KB pages of a given type from a memory region that is
+  accessible to PEI.
+
+  Allocates the number of 4KB pages of type 'MemoryType' and returns a
+  pointer to the allocated buffer.  The buffer returned is aligned on a 4KB
+  boundary.  If Pages is 0, then NULL is returned.  If there is not enough
+  memory remaining to satisfy the request, then NULL is returned.
+
+  @param[in]  MemoryType            The memory type to allocate
+  @param[in]  Pages                 The number of 4 KB pages to allocate.
+
+  @return A pointer to the allocated buffer or NULL if allocation fails.
+
+**/
+VOID *
+EFIAPI
+EfiAllocatePeiAccessiblePages (
+  IN EFI_MEMORY_TYPE  MemoryType,
+  IN UINTN            Pages
+  )
+{
+  EFI_STATUS            Status;
+  EFI_PHYSICAL_ADDRESS  Memory;
+  EFI_ALLOCATE_TYPE     AllocType;
+
+  if (Pages == 0) {
+    return NULL;
+  }
+
+#ifdef MDE_CPU_X64
+  //
+  // On X64 systems, a X64 build of DXE may be combined with a 32-bit build of
+  // PEI, and so we need to allocate below 4 GB to ensure that the allocation
+  // is accessible by PEI.
+  //
+  AllocType = AllocateMaxAddress;
+  Memory = MAX_UINT32;
+#else
+  AllocType = AllocateAnyPages;
+#endif
+  Status = gBS->AllocatePages (AllocType, MemoryType, Pages, &Memory);
+  if (EFI_ERROR (Status)) {
+    return NULL;
+  }
+  return (VOID *)(UINTN)Memory;
+}
-- 
2.17.0

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