1 files changed, 71 insertions, 0 deletions
diff --git a/src/VBox/Runtime/common/asm/ASMAtomicReadU64.asm b/src/VBox/Runtime/common/asm/ASMAtomicReadU64.asm
new file mode 100644
index 00000000..2213d8fb
--- /dev/null
+++ b/src/VBox/Runtime/common/asm/ASMAtomicReadU64.asm
@@ -0,0 +1,71 @@
+; $Id: ASMAtomicReadU64.asm $
+;; @file
+; IPRT - ASMAtomicReadU64().
+;
+
+;
+; Copyright (C) 2006-2019 Oracle Corporation
+;
+; This file is part of VirtualBox Open Source Edition (OSE), as
+; available from http://www.virtualbox.org. This file is free software;
+; you can redistribute it and/or modify it under the terms of the GNU
+; General Public License (GPL) as published by the Free Software
+; Foundation, in version 2 as it comes in the "COPYING" file of the
+; VirtualBox OSE distribution. VirtualBox OSE is distributed in the
+; hope that it will be useful, but WITHOUT ANY WARRANTY of any kind.
+;
+; The contents of this file may alternatively be used under the terms
+; of the Common Development and Distribution License Version 1.0
+; (CDDL) only, as it comes in the "COPYING.CDDL" file of the
+; VirtualBox OSE distribution, in which case the provisions of the
+; CDDL are applicable instead of those of the GPL.
+;
+; You may elect to license modified versions of this file under the
+; terms and conditions of either the GPL or the CDDL or both.
+;
+
+;*******************************************************************************
+;* Header Files                                                                *
+;*******************************************************************************
+%include "iprt/asmdefs.mac"
+
+BEGINCODE
+
+;;
+; Atomically reads 64-bit value.
+;
+; @param   pu64     x86:ebp+8
+;
+; @returns The current value. (x86:eax+edx)
+;
+;
+BEGINPROC_EXPORTED ASMAtomicReadU64
+%ifdef RT_ARCH_AMD64
+        mfence                          ; ASSUME its present.
+ %ifdef ASM_CALL64_MSC
+        mov     rax, [rcx]
+ %else
+        mov     rax, [rdi]
+ %endif
+        ret
+%endif
+%ifdef RT_ARCH_X86
+        push    ebp
+        mov     ebp, esp
+        push    ebx
+        push    edi
+
+        xor     eax, eax
+        xor     edx, edx
+        mov     edi, [ebp+08h]
+        xor     ecx, ecx
+        xor     ebx, ebx
+        lock cmpxchg8b [edi]
+
+        pop     edi
+        pop     ebx
+        leave
+        ret
+%endif
+ENDPROC ASMAtomicReadU64
+