[edk2-devel] [PATCH v2 1/7] MdePkg/BaseLib: AARCH64: Add ArmReadCntPctReg()

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

To enable AARCH64 native instruction support for Openssl,
some interfaces must be implemented. OPENSSL_rdtsc() requests
an access to a counter to get some non-trusted entropy.

Add ArmReadCntPctReg() to read system count.
A similar ArmReadCntPct() function is available in the ArmPkg,
but the CryptoPkg where OPENSSL_rdtsc will reside cannot rely
on the ArmPkg.

Signed-off-by: Pierre Gondois <Pierre.Gondois@arm.com>
---
 MdePkg/Include/Library/BaseLib.h              | 14 +++++++++
 .../BaseLib/AArch64/ArmReadCntPctReg.S        | 30 +++++++++++++++++++
 .../BaseLib/AArch64/ArmReadCntPctReg.asm      | 30 +++++++++++++++++++
 MdePkg/Library/BaseLib/BaseLib.inf            |  4 ++-
 4 files changed, 77 insertions(+), 1 deletion(-)
 create mode 100644 MdePkg/Library/BaseLib/AArch64/ArmReadCntPctReg.S
 create mode 100644 MdePkg/Library/BaseLib/AArch64/ArmReadCntPctReg.asm

diff --git a/MdePkg/Include/Library/BaseLib.h b/MdePkg/Include/Library/BaseLib.h
index 5d7067ee854e..b81c9dd83508 100644
--- a/MdePkg/Include/Library/BaseLib.h
+++ b/MdePkg/Include/Library/BaseLib.h
@@ -126,6 +126,20 @@ typedef struct {
 
 #define BASE_LIBRARY_JUMP_BUFFER_ALIGNMENT  8
 
+/**
+  Reads the current value of CNTPCT_EL0 register.
+
+  Reads and returns the current value of CNTPCT_EL0.
+  This function is only available on AARCH64.
+
+  @return The current value of CNTPCT_EL0
+**/
+UINT64
+EFIAPI
+ArmReadCntPctReg (
+  VOID
+  );
+
 #endif // defined (MDE_CPU_AARCH64)
 
 #if defined (MDE_CPU_RISCV64)
diff --git a/MdePkg/Library/BaseLib/AArch64/ArmReadCntPctReg.S b/MdePkg/Library/BaseLib/AArch64/ArmReadCntPctReg.S
new file mode 100644
index 000000000000..d5f3a0082a99
--- /dev/null
+++ b/MdePkg/Library/BaseLib/AArch64/ArmReadCntPctReg.S
@@ -0,0 +1,30 @@
+#------------------------------------------------------------------------------
+#
+# ArmReadCntPctReg() for AArch64
+#
+# Copyright (c) 2023, Arm Limited. All rights reserved.<BR>
+#
+# SPDX-License-Identifier: BSD-2-Clause-Patent
+#
+#------------------------------------------------------------------------------
+
+.text
+.p2align 2
+GCC_ASM_EXPORT(ArmReadCntPctReg)
+
+#/**
+#  Reads the CNTPCT_EL0 Register.
+#
+#  @return The contents of the CNTPCT_EL0 register.
+#
+#**/
+#UINT64
+#EFIAPI
+#ArmReadCntPctReg (
+#  VOID
+#  );
+#
+ASM_PFX(ArmReadCntPctReg):
+  AARCH64_BTI(c)
+  mrs   x0, cntpct_el0
+  ret
diff --git a/MdePkg/Library/BaseLib/AArch64/ArmReadCntPctReg.asm b/MdePkg/Library/BaseLib/AArch64/ArmReadCntPctReg.asm
new file mode 100644
index 000000000000..cfdfe4cea4eb
--- /dev/null
+++ b/MdePkg/Library/BaseLib/AArch64/ArmReadCntPctReg.asm
@@ -0,0 +1,30 @@
+;------------------------------------------------------------------------------
+;
+; ArmReadCntPctReg() for AArch64
+;
+; Copyright (c) 2023, Arm Limited. All rights reserved.<BR>
+;
+; SPDX-License-Identifier: BSD-2-Clause-Patent
+;
+;------------------------------------------------------------------------------
+
+  EXPORT ArmReadCntPctReg
+  AREA BaseLib_LowLevel, CODE, READONLY
+
+;/**
+;  Reads the CNTPCT_EL0 Register.
+;
+; @return The contents of the CNTPCT_EL0 register.
+;
+;**/
+;UINT64
+;EFIAPI
+;ArmReadCntPctReg (
+;  VOID
+;  );
+;
+ArmReadCntPctReg
+  mrs   x0, cntpct_el0
+  ret
+
+  END
diff --git a/MdePkg/Library/BaseLib/BaseLib.inf b/MdePkg/Library/BaseLib/BaseLib.inf
index 03c7b02e828b..24e5e6c3ecb5 100644
--- a/MdePkg/Library/BaseLib/BaseLib.inf
+++ b/MdePkg/Library/BaseLib/BaseLib.inf
@@ -3,7 +3,7 @@
 #
 #  Copyright (c) 2007 - 2021, Intel Corporation. All rights reserved.<BR>
 #  Portions copyright (c) 2008 - 2009, Apple Inc. All rights reserved.<BR>
-#  Portions copyright (c) 2011 - 2013, ARM Ltd. All rights reserved.<BR>
+#  Portions copyright (c) 2011 - 2023, Arm Limited. All rights reserved.<BR>
 #  Copyright (c) 2020 - 2021, Hewlett Packard Enterprise Development LP. All rights reserved.<BR>
 #
 #  SPDX-License-Identifier: BSD-2-Clause-Patent
@@ -376,6 +376,7 @@ [Sources.AARCH64]
   AArch64/SetJumpLongJump.S         | GCC
   AArch64/CpuBreakpoint.S           | GCC
   AArch64/SpeculationBarrier.S      | GCC
+  AArch64/ArmReadCntPctReg.S        | GCC
 
   AArch64/MemoryFence.asm           | MSFT
   AArch64/SwitchStack.asm           | MSFT
@@ -385,6 +386,7 @@ [Sources.AARCH64]
   AArch64/SetJumpLongJump.asm       | MSFT
   AArch64/CpuBreakpoint.asm         | MSFT
   AArch64/SpeculationBarrier.asm    | MSFT
+  AArch64/ArmReadCntPctReg.asm      | MSFT
 
 [Sources.RISCV64]
   Math64.c
-- 
2.25.1



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