[edk2-devel] [PATCH v1 3/7] MdePkg/BaseRngLib: Prefer ArmReadIdAA64Isar0Reg() over ArmReadIdIsar0()

["PierreGondois" <pierre.gondois@arm.com>]

A ArmReadIdAA64Isar0Reg() function was recently added
to BaseLib. Use it instead of its ArmReadIdIsar0() equivalent,
which was private to the BaseRngLib library.

This also allows to avoid the confusion between the following
registers:
- ID_ISAR0_EL1: allows to probe for Divide instructions, Debug
  instructions, ...
- ID_AA64ISAR0_EL1: AARCH64 specific register allowing to probe
  for AESE, RNDR, ... instructions

Signed-off-by: Pierre Gondois <pierre.gondois@arm.com>
---
 .../BaseRngLib/AArch64/ArmReadIdIsar0.S       | 30 -------------------
 .../BaseRngLib/AArch64/ArmReadIdIsar0.asm     | 30 -------------------
 MdePkg/Library/BaseRngLib/AArch64/ArmRng.h    | 12 --------
 MdePkg/Library/BaseRngLib/AArch64/Rndr.c      | 14 ++-------
 MdePkg/Library/BaseRngLib/BaseRngLib.inf      |  2 --
 5 files changed, 3 insertions(+), 85 deletions(-)
 delete mode 100644 MdePkg/Library/BaseRngLib/AArch64/ArmReadIdIsar0.S
 delete mode 100644 MdePkg/Library/BaseRngLib/AArch64/ArmReadIdIsar0.asm

diff --git a/MdePkg/Library/BaseRngLib/AArch64/ArmReadIdIsar0.S b/MdePkg/Library/BaseRngLib/AArch64/ArmReadIdIsar0.S
deleted file mode 100644
index d30b63fe5c68..000000000000
--- a/MdePkg/Library/BaseRngLib/AArch64/ArmReadIdIsar0.S
+++ /dev/null
@@ -1,30 +0,0 @@
-#------------------------------------------------------------------------------
-#
-# ArmReadIdIsar0() for AArch64
-#
-# Copyright (c) 2021, NUVIA Inc. All rights reserved.<BR>
-#
-# SPDX-License-Identifier: BSD-2-Clause-Patent
-#
-#------------------------------------------------------------------------------
-
-.text
-.p2align 2
-GCC_ASM_EXPORT(ArmReadIdIsar0)
-
-#/**
-#  Reads the ID_AA64ISAR0 Register.
-#
-#  @return The contents of the ID_AA64ISAR0 register.
-#
-#**/
-#UINT64
-#EFIAPI
-#ArmReadIdIsar0 (
-#  VOID
-#  );
-#
-ASM_PFX(ArmReadIdIsar0):
-  AARCH64_BTI(c)
-  mrs  x0, id_aa64isar0_el1 // Read ID_AA64ISAR0 Register
-  ret
diff --git a/MdePkg/Library/BaseRngLib/AArch64/ArmReadIdIsar0.asm b/MdePkg/Library/BaseRngLib/AArch64/ArmReadIdIsar0.asm
deleted file mode 100644
index 1d9f9a808c0c..000000000000
--- a/MdePkg/Library/BaseRngLib/AArch64/ArmReadIdIsar0.asm
+++ /dev/null
@@ -1,30 +0,0 @@
-;------------------------------------------------------------------------------
-;
-; ArmReadIdIsar0() for AArch64
-;
-; Copyright (c) 2021, NUVIA Inc. All rights reserved.<BR>
-;
-; SPDX-License-Identifier: BSD-2-Clause-Patent
-;
-;------------------------------------------------------------------------------
-
-  EXPORT ArmReadIdIsar0
-  AREA BaseLib_LowLevel, CODE, READONLY
-
-;/**
-;  Reads the ID_AA64ISAR0 Register.
-;
-; @return The contents of the ID_AA64ISAR0 register.
-;
-;**/
-;UINT64
-;EFIAPI
-;ArmReadIdIsar0 (
-;  VOID
-;  );
-;
-ArmReadIdIsar0
-  mrs  x0, id_aa64isar0_el1 // Read ID_AA64ISAR0 Register
-  ret
-
-  END
diff --git a/MdePkg/Library/BaseRngLib/AArch64/ArmRng.h b/MdePkg/Library/BaseRngLib/AArch64/ArmRng.h
index 2d6ef48ab941..b4b3c97071bb 100644
--- a/MdePkg/Library/BaseRngLib/AArch64/ArmRng.h
+++ b/MdePkg/Library/BaseRngLib/AArch64/ArmRng.h
@@ -27,16 +27,4 @@ ArmRndr (
   OUT UINT64  *Rand
   );
 
-/**
-  Reads the ID_AA64ISAR0 Register.
-
-  @return The contents of the ID_AA64ISAR0 register.
-
-**/
-UINT64
-EFIAPI
-ArmReadIdIsar0 (
-  VOID
-  );
-
 #endif /* ARM_RNG_H_ */
diff --git a/MdePkg/Library/BaseRngLib/AArch64/Rndr.c b/MdePkg/Library/BaseRngLib/AArch64/Rndr.c
index d39db62153ee..684b02f018b6 100644
--- a/MdePkg/Library/BaseRngLib/AArch64/Rndr.c
+++ b/MdePkg/Library/BaseRngLib/AArch64/Rndr.c
@@ -21,11 +21,6 @@
 
 STATIC BOOLEAN  mRndrSupported;
 
-//
-// Bit mask used to determine if RNDR instruction is supported.
-//
-#define RNDR_MASK  ((UINT64)MAX_UINT16 << 60U)
-
 /**
   The constructor function checks whether or not RNDR instruction is supported
   by the host hardware.
@@ -43,16 +38,13 @@ BaseRngLibConstructor (
   VOID
   )
 {
-  UINT64  Isar0;
-
   //
   // Determine RNDR support by examining bits 63:60 of the ISAR0 register returned by
   // MSR. A non-zero value indicates that the processor supports the RNDR instruction.
   //
-  Isar0 = ArmReadIdIsar0 ();
-  ASSERT ((Isar0 & RNDR_MASK) != 0);
-
-  mRndrSupported = ((Isar0 & RNDR_MASK) != 0);
+  mRndrSupported = !((ArmReadIdAA64Isar0Reg () >> ARM_ID_AA64ISAR0_EL1_AES_SHIFT) &
+                     ARM_ID_AA64ISAR0_EL1_AES_MASK);
+  ASSERT (mRndrSupported);
 
   return EFI_SUCCESS;
 }
diff --git a/MdePkg/Library/BaseRngLib/BaseRngLib.inf b/MdePkg/Library/BaseRngLib/BaseRngLib.inf
index 49503b139be9..bd89cf3a1927 100644
--- a/MdePkg/Library/BaseRngLib/BaseRngLib.inf
+++ b/MdePkg/Library/BaseRngLib/BaseRngLib.inf
@@ -38,10 +38,8 @@ [Sources.AARCH64]
   AArch64/Rndr.c
   AArch64/ArmRng.h
 
-  AArch64/ArmReadIdIsar0.S   | GCC
   AArch64/ArmRng.S           | GCC
 
-  AArch64/ArmReadIdIsar0.asm | MSFT
   AArch64/ArmRng.asm         | MSFT
 
 [Guids.AARCH64]
-- 
2.25.1



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