[Xen-devel] [PATCH v3 21/27] Ovmf/Xen: add ARM and AArch64 support to XenBusDxe

[Ard Biesheuvel <ard.biesheuvel@xxxxxxxxxx>]

This patch adds support to XenBusDxe for executing on ARM and AArch64
machines (the former only when built with GCC).

Contributed-under: TianoCore Contribution Agreement 1.0
Signed-off-by: Ard Biesheuvel <ard.biesheuvel@xxxxxxxxxx>
---
 OvmfPkg/XenBusDxe/AtomicsGcc.c  | 44 +++++++++++++++++++++++++++++++++++++++++
 OvmfPkg/XenBusDxe/XenBusDxe.inf |  3 +++
 2 files changed, 47 insertions(+)
 create mode 100644 OvmfPkg/XenBusDxe/AtomicsGcc.c

diff --git a/OvmfPkg/XenBusDxe/AtomicsGcc.c b/OvmfPkg/XenBusDxe/AtomicsGcc.c
new file mode 100644
index 000000000000..a0bdcbf67440
--- /dev/null
+++ b/OvmfPkg/XenBusDxe/AtomicsGcc.c
@@ -0,0 +1,44 @@
+/** @file
+  Arch-independent implementations of XenBusDxe atomics using GCC __builtins
+
+  Copyright (C) 2014, Linaro Ltd.
+
+  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.
+
+**/
+
+UINT16
+EFIAPI
+InternalSyncCompareExchange16 (
+  IN      volatile UINT16           *Value,
+  IN      UINT16                    CompareValue,
+  IN      UINT16                    ExchangeValue
+  )
+{
+  return __sync_val_compare_and_swap_2 (Value, CompareValue, ExchangeValue);
+}
+
+INT32
+EFIAPI
+TestAndClearBit (
+  IN INT32            Bit,
+  IN volatile VOID    *Address
+  )
+{
+  //
+  // Calculate the effective address relative to 'Address' based on the
+  // higher order bits of 'Bit'. Use signed shift instead of division to
+  // ensure we round towards -Inf, and end up with a positive shift in 'Bit',
+  // even if 'Bit' itself is negative.
+  //
+  Address += (Bit >> 5) * sizeof(INT32);
+  Bit &= 31;
+
+  return (__sync_fetch_and_and_4 (Address, ~(1U << Bit)) & (1U << Bit)) != 0;
+}
diff --git a/OvmfPkg/XenBusDxe/XenBusDxe.inf b/OvmfPkg/XenBusDxe/XenBusDxe.inf
index 31553ac5a64a..949ec0a0c732 100644
--- a/OvmfPkg/XenBusDxe/XenBusDxe.inf
+++ b/OvmfPkg/XenBusDxe/XenBusDxe.inf
@@ -54,6 +54,9 @@
   X64/InterlockedCompareExchange16.nasm
   X64/TestAndClearBit.nasm
 
+[Sources.AARCH64, Sources.ARM]
+  AtomicsGcc.c | GCC
+
 [LibraryClasses]
   UefiDriverEntryPoint
   UefiBootServicesTableLib
-- 
1.8.3.2


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