[PATCH] MdePkg/BaseLib: implement SpeculationBarrier() for ARM and AArch64

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

Replace the dummy C implementation of SpeculationBarrier() with
implementations consisting of the recommended DSB SY + ISB sequence,
as recommended by ARM in the whitepaper "Cache Speculation Side-channels"
version 2.4, dated October 2018.

Contributed-under: TianoCore Contribution Agreement 1.1
Signed-off-by: Ard Biesheuvel <ard.biesheuvel@linaro.org>
---
 MdePkg/Library/BaseLib/AArch64/SpeculationBarrier.S   | 39 ++++++++++++++++++++
 MdePkg/Library/BaseLib/AArch64/SpeculationBarrier.asm | 38 +++++++++++++++++++
 MdePkg/Library/BaseLib/Arm/SpeculationBarrier.S       | 39 ++++++++++++++++++++
 MdePkg/Library/BaseLib/Arm/SpeculationBarrier.asm     | 39 ++++++++++++++++++++
 MdePkg/Library/BaseLib/Arm/SpeculationBarrier.c       | 30 ---------------
 MdePkg/Library/BaseLib/BaseLib.inf                    |  7 +++-
 6 files changed, 160 insertions(+), 32 deletions(-)

diff --git a/MdePkg/Library/BaseLib/AArch64/SpeculationBarrier.S b/MdePkg/Library/BaseLib/AArch64/SpeculationBarrier.S
new file mode 100644
index 000000000000..500bdadca5d2
--- /dev/null
+++ b/MdePkg/Library/BaseLib/AArch64/SpeculationBarrier.S
@@ -0,0 +1,39 @@
+##------------------------------------------------------------------------------
+#
+# SpeculationBarrier() for AArch64
+#
+# Copyright (c) 2019, Linaro Ltd. All rights reserved.
+#
+# This program and the accompanying materials
+# are licensed and made available under the terms and conditions of the BSD License
+# which accompanies this distribution.  The full text of the license may be found at
+# http://opensource.org/licenses/bsd-license.php.
+#
+# THE PROGRAM IS DISTRIBUTED UNDER THE BSD LICENSE ON AN "AS IS" BASIS,
+# WITHOUT WARRANTIES OR REPRESENTATIONS OF ANY KIND, EITHER EXPRESS OR IMPLIED.
+#
+##------------------------------------------------------------------------------
+
+.text
+.p2align 2
+
+GCC_ASM_EXPORT(SpeculationBarrier)
+
+
+#/**
+#  Uses as a barrier to stop speculative execution.
+#
+#  Ensures that no later instruction will execute speculatively, until all prior
+#  instructions have completed.
+#
+#**/
+#VOID
+#EFIAPI
+#SpeculationBarrier (
+#  VOID
+#  );
+#
+ASM_PFX(SpeculationBarrier):
+    dsb  sy
+    isb
+    ret
diff --git a/MdePkg/Library/BaseLib/AArch64/SpeculationBarrier.asm b/MdePkg/Library/BaseLib/AArch64/SpeculationBarrier.asm
new file mode 100644
index 000000000000..0c4b915b7798
--- /dev/null
+++ b/MdePkg/Library/BaseLib/AArch64/SpeculationBarrier.asm
@@ -0,0 +1,38 @@
+;------------------------------------------------------------------------------
+;
+; SpeculationBarrier() for AArch64
+;
+; Copyright (c) 2019, Linaro Ltd. All rights reserved.
+;
+; This program and the accompanying materials
+; are licensed and made available under the terms and conditions of the BSD License
+; which accompanies this distribution.  The full text of the license may be found at
+; http://opensource.org/licenses/bsd-license.php.
+;
+; THE PROGRAM IS DISTRIBUTED UNDER THE BSD LICENSE ON AN "AS IS" BASIS,
+; WITHOUT WARRANTIES OR REPRESENTATIONS OF ANY KIND, EITHER EXPRESS OR IMPLIED.
+;
+;------------------------------------------------------------------------------
+
+  EXPORT SpeculationBarrier
+  AREA BaseLib_LowLevel, CODE, READONLY
+
+;/**
+;  Uses as a barrier to stop speculative execution.
+;
+;  Ensures that no later instruction will execute speculatively, until all prior
+;  instructions have completed.
+;
+;**/
+;VOID
+;EFIAPI
+;SpeculationBarrier (
+;  VOID
+;  );
+;
+SpeculationBarrier
+    dsb   sy
+    isb
+    ret
+
+  END
diff --git a/MdePkg/Library/BaseLib/Arm/SpeculationBarrier.S b/MdePkg/Library/BaseLib/Arm/SpeculationBarrier.S
new file mode 100644
index 000000000000..7857558aba17
--- /dev/null
+++ b/MdePkg/Library/BaseLib/Arm/SpeculationBarrier.S
@@ -0,0 +1,39 @@
+##------------------------------------------------------------------------------
+#
+# SpeculationBarrier() for AArch64
+#
+# Copyright (c) 2019, Linaro Ltd. All rights reserved.
+#
+# This program and the accompanying materials
+# are licensed and made available under the terms and conditions of the BSD License
+# which accompanies this distribution.  The full text of the license may be found at
+# http://opensource.org/licenses/bsd-license.php.
+#
+# THE PROGRAM IS DISTRIBUTED UNDER THE BSD LICENSE ON AN "AS IS" BASIS,
+# WITHOUT WARRANTIES OR REPRESENTATIONS OF ANY KIND, EITHER EXPRESS OR IMPLIED.
+#
+##------------------------------------------------------------------------------
+
+.text
+.p2align 2
+
+GCC_ASM_EXPORT(SpeculationBarrier)
+
+
+#/**
+#  Uses as a barrier to stop speculative execution.
+#
+#  Ensures that no later instruction will execute speculatively, until all prior
+#  instructions have completed.
+#
+#**/
+#VOID
+#EFIAPI
+#SpeculationBarrier (
+#  VOID
+#  );
+#
+ASM_PFX(SpeculationBarrier):
+    dsb
+    isb
+    bx   lr
diff --git a/MdePkg/Library/BaseLib/Arm/SpeculationBarrier.asm b/MdePkg/Library/BaseLib/Arm/SpeculationBarrier.asm
new file mode 100644
index 000000000000..425cd3de9e22
--- /dev/null
+++ b/MdePkg/Library/BaseLib/Arm/SpeculationBarrier.asm
@@ -0,0 +1,39 @@
+;------------------------------------------------------------------------------
+;
+; SpeculationBarrier() for AArch64
+;
+; Copyright (c) 2019, Linaro Ltd. All rights reserved.
+;
+; This program and the accompanying materials
+; are licensed and made available under the terms and conditions of the BSD License
+; which accompanies this distribution.  The full text of the license may be found at
+; http://opensource.org/licenses/bsd-license.php.
+;
+; THE PROGRAM IS DISTRIBUTED UNDER THE BSD LICENSE ON AN "AS IS" BASIS,
+; WITHOUT WARRANTIES OR REPRESENTATIONS OF ANY KIND, EITHER EXPRESS OR IMPLIED.
+;
+;------------------------------------------------------------------------------
+
+    EXPORT SpeculationBarrier
+
+    AREA MemoryBarriers, CODE, READONLY
+
+;/**
+;  Uses as a barrier to stop speculative execution.
+;
+;  Ensures that no later instruction will execute speculatively, until all prior
+;  instructions have completed.
+;
+;**/
+;VOID
+;EFIAPI
+;SpeculationBarrier (
+;  VOID
+;  );
+;
+SpeculationBarrier
+    dsb
+    isb
+    bx    lr
+
+  END
diff --git a/MdePkg/Library/BaseLib/Arm/SpeculationBarrier.c b/MdePkg/Library/BaseLib/Arm/SpeculationBarrier.c
deleted file mode 100644
index 8a6165a10227..000000000000
--- a/MdePkg/Library/BaseLib/Arm/SpeculationBarrier.c
+++ /dev/null
@@ -1,30 +0,0 @@
-/** @file
-  SpeculationBarrier() function for ARM.
-
-  Copyright (C) 2018, Intel Corporation. All rights reserved.<BR>
-
-  This program and the accompanying materials are licensed and made available
-  under the terms and conditions of the BSD License which accompanies this
-  distribution.  The full text of the license may be found at
-  http://opensource.org/licenses/bsd-license.php.
-
-  THE PROGRAM IS DISTRIBUTED UNDER THE BSD LICENSE ON AN "AS IS" BASIS, WITHOUT
-  WARRANTIES OR REPRESENTATIONS OF ANY KIND, EITHER EXPRESS OR IMPLIED.
-
-**/
-
-
-/**
-  Uses as a barrier to stop speculative execution.
-
-  Ensures that no later instruction will execute speculatively, until all prior
-  instructions have completed.
-
-**/
-VOID
-EFIAPI
-SpeculationBarrier (
-  VOID
-  )
-{
-}
diff --git a/MdePkg/Library/BaseLib/BaseLib.inf b/MdePkg/Library/BaseLib/BaseLib.inf
index d195c5417b2e..f25a067a2335 100644
--- a/MdePkg/Library/BaseLib/BaseLib.inf
+++ b/MdePkg/Library/BaseLib/BaseLib.inf
@@ -552,7 +552,6 @@
 [Sources.ARM]
   Arm/InternalSwitchStack.c
   Arm/Unaligned.c
-  Arm/SpeculationBarrier.c
   Math64.c                   | RVCT
   Math64.c                   | MSFT
 
@@ -564,6 +563,7 @@
   Arm/CpuPause.asm           | RVCT
   Arm/CpuBreakpoint.asm      | RVCT
   Arm/MemoryFence.asm        | RVCT
+  Arm/SpeculationBarrier.S   | RVCT
 
   Arm/SwitchStack.asm        | MSFT
   Arm/SetJumpLongJump.asm    | MSFT
@@ -573,6 +573,7 @@
   Arm/CpuPause.asm           | MSFT
   Arm/CpuBreakpoint.asm      | MSFT
   Arm/MemoryFence.asm        | MSFT
+  Arm/SpeculationBarrier.asm | MSFT
 
   Arm/Math64.S                  | GCC
   Arm/SwitchStack.S             | GCC
@@ -582,11 +583,11 @@
   Arm/SetJumpLongJump.S         | GCC
   Arm/CpuBreakpoint.S           | GCC
   Arm/MemoryFence.S             | GCC
+  Arm/SpeculationBarrier.S      | GCC
 
 [Sources.AARCH64]
   Arm/InternalSwitchStack.c
   Arm/Unaligned.c
-  Arm/SpeculationBarrier.c
   Math64.c
 
   AArch64/MemoryFence.S             | GCC
@@ -596,6 +597,7 @@
   AArch64/GetInterruptsState.S      | GCC
   AArch64/SetJumpLongJump.S         | GCC
   AArch64/CpuBreakpoint.S           | GCC
+  AArch64/SpeculationBarrier.S      | GCC
 
   AArch64/MemoryFence.asm           | MSFT
   AArch64/SwitchStack.asm           | MSFT
@@ -604,6 +606,7 @@
   AArch64/GetInterruptsState.asm    | MSFT
   AArch64/SetJumpLongJump.asm       | MSFT
   AArch64/CpuBreakpoint.asm         | MSFT
+  AArch64/SpeculationBarrier.asm    | MSFT
 
 [Packages]
   MdePkg/MdePkg.dec
-- 
2.17.1