[PATCH 3/6] MdePkg/UefiLib: introduce EfiAllocatePeiAccessiblePages routine

[Ard Biesheuvel <ard.biesheuvel@linaro.org>]

Add a routine to UefiLib that abstracts the allocation of memory that
should be accessible by PEI after a warm reboot. We will use it to
replace open coded implementations that limit the address to < 4 GB,
which may not be possible on non-Intel systems that have no 32-bit
addressable memory at all.

Contributed-under: TianoCore Contribution Agreement 1.1
Signed-off-by: Ard Biesheuvel <ard.biesheuvel@linaro.org>
---
 MdePkg/Include/Library/UefiLib.h | 23 ++++++++++
 MdePkg/Library/UefiLib/UefiLib.c | 48 ++++++++++++++++++++
 2 files changed, 71 insertions(+)

diff --git a/MdePkg/Include/Library/UefiLib.h b/MdePkg/Include/Library/UefiLib.h
index 256498e3fd8d..8fa077af41e0 100644
--- a/MdePkg/Include/Library/UefiLib.h
+++ b/MdePkg/Include/Library/UefiLib.h
@@ -1520,4 +1520,27 @@ EfiLocateProtocolBuffer (
   OUT UINTN     *NoProtocols,
   OUT VOID      ***Buffer
   );
+
+/**
+  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
+  );
+
 #endif
diff --git a/MdePkg/Library/UefiLib/UefiLib.c b/MdePkg/Library/UefiLib/UefiLib.c
index ba449a1c34ce..3a9d75149dd7 100644
--- a/MdePkg/Library/UefiLib/UefiLib.c
+++ b/MdePkg/Library/UefiLib/UefiLib.c
@@ -1715,3 +1715,51 @@ 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