From f947205cee76a1ae9ddf555d7e2a45675fe333fd Mon Sep 17 00:00:00 2001
From: "Jason A. Donenfeld" <Jason@zx2c4.com>
Date: Fri, 30 Oct 2020 16:58:50 +0100
Subject: [PATCH] api: use proper iso atomic semantics

Signed-off-by: Jason A. Donenfeld <Jason@zx2c4.com>
---
 api/api.vcxproj         |  2 +-
 api/api.vcxproj.filters |  3 ---
 api/atomic.h            | 26 --------------------------
 api/pch.h               |  1 -
 api/session.c           | 10 +++++-----
 5 files changed, 6 insertions(+), 36 deletions(-)
 delete mode 100644 api/atomic.h

diff --git a/api/api.vcxproj b/api/api.vcxproj
index 12ae6ca..cea689d 100644
--- a/api/api.vcxproj
+++ b/api/api.vcxproj
@@ -146,6 +146,7 @@
       <PreprocessorDefinitions Condition="Exists('$(OutDir)whql\')">HAVE_WHQL;%(PreprocessorDefinitions)</PreprocessorDefinitions>
       <PrecompiledHeader>Use</PrecompiledHeader>
       <PrecompiledHeaderFile>pch.h</PrecompiledHeaderFile>
+      <AdditionalOptions>/volatile:iso %(AdditionalOptions)</AdditionalOptions>
     </ClCompile>
     <ResourceCompile>
       <AdditionalIncludeDirectories>..\$(Configuration)\$(WintunPlatform);..\$(Configuration);%(AdditionalIncludeDirectories)</AdditionalIncludeDirectories>
@@ -194,7 +195,6 @@
   <ItemGroup>
     <ClInclude Include="api.h" />
     <ClInclude Include="adapter.h" />
-    <ClInclude Include="atomic.h" />
     <ClInclude Include="elevate.h" />
     <ClInclude Include="logger.h" />
     <ClInclude Include="namespace.h" />
diff --git a/api/api.vcxproj.filters b/api/api.vcxproj.filters
index 090a1ef..c585527 100644
--- a/api/api.vcxproj.filters
+++ b/api/api.vcxproj.filters
@@ -52,9 +52,6 @@
     <ClInclude Include="wintun.h">
       <Filter>Header Files</Filter>
     </ClInclude>
-    <ClInclude Include="atomic.h">
-      <Filter>Header Files</Filter>
-    </ClInclude>
     <ClInclude Include="elevate.h">
       <Filter>Header Files</Filter>
     </ClInclude>
diff --git a/api/atomic.h b/api/atomic.h
deleted file mode 100644
index 011e53b..0000000
--- a/api/atomic.h
+++ /dev/null
@@ -1,26 +0,0 @@
-/* SPDX-License-Identifier: GPL-2.0
- *
- * Copyright (C) 2018-2020 WireGuard LLC. All Rights Reserved.
- */
-
-#pragma once
-
-#include <Windows.h>
-
-static __forceinline VOID
-InterlockedSetU(_Inout_ _Interlocked_operand_ ULONG volatile *Target, _In_ ULONG Value)
-{
-    *Target = Value;
-}
-
-static __forceinline LONG
-InterlockedGet(_In_ _Interlocked_operand_ LONG volatile *Value)
-{
-    return *Value;
-}
-
-static __forceinline ULONG
-InterlockedGetU(_In_ _Interlocked_operand_ ULONG volatile *Value)
-{
-    return *Value;
-}
diff --git a/api/pch.h b/api/pch.h
index bb5b3a1..45bf3b1 100644
--- a/api/pch.h
+++ b/api/pch.h
@@ -6,7 +6,6 @@
 #pragma once
 
 #include "adapter.h"
-#include "atomic.h"
 #include "api.h"
 #include "elevate.h"
 #include "logger.h"
diff --git a/api/session.c b/api/session.c
index 71849c3..e39f21b 100644
--- a/api/session.c
+++ b/api/session.c
@@ -172,7 +172,7 @@ WintunReceivePacket(_In_ TUN_SESSION *Session, _Out_bytecapcount_(*PacketSize) B
         Result = ERROR_HANDLE_EOF;
         goto cleanup;
     }
-    const ULONG BuffTail = InterlockedGetU(&Session->Descriptor.Send.Ring->Tail);
+    const ULONG BuffTail = ReadULongAcquire(&Session->Descriptor.Send.Ring->Tail);
     if (BuffTail >= Session->Capacity)
     {
         Result = ERROR_HANDLE_EOF;
@@ -226,7 +226,7 @@ WintunReceiveRelease(_In_ TUN_SESSION *Session, _In_ const BYTE *Packet)
         Session->Send.HeadRelease = TUN_RING_WRAP(Session->Send.HeadRelease + AlignedPacketSize, Session->Capacity);
         Session->Send.PacketsToRelease--;
     }
-    InterlockedSetU(&Session->Descriptor.Send.Ring->Head, Session->Send.HeadRelease);
+    WriteULongRelease(&Session->Descriptor.Send.Ring->Head, Session->Send.HeadRelease);
     LeaveCriticalSection(&Session->Send.Lock);
 }
 
@@ -241,7 +241,7 @@ WintunAllocateSendPacket(_In_ TUN_SESSION *Session, _In_ DWORD PacketSize, _Out_
         goto cleanup;
     }
     const ULONG AlignedPacketSize = TUN_ALIGN(sizeof(TUN_PACKET) + PacketSize);
-    const ULONG BuffHead = InterlockedGetU(&Session->Descriptor.Receive.Ring->Head);
+    const ULONG BuffHead = ReadULongAcquire(&Session->Descriptor.Receive.Ring->Head);
     if (BuffHead >= Session->Capacity)
     {
         Result = ERROR_HANDLE_EOF;
@@ -281,8 +281,8 @@ WintunSendPacket(_In_ TUN_SESSION *Session, _In_ const BYTE *Packet)
             TUN_RING_WRAP(Session->Receive.TailRelease + AlignedPacketSize, Session->Capacity);
         Session->Receive.PacketsToRelease--;
     }
-    InterlockedSetU(&Session->Descriptor.Receive.Ring->Tail, Session->Receive.TailRelease);
-    if (InterlockedGet(&Session->Descriptor.Receive.Ring->Alertable))
+    WriteULongRelease(&Session->Descriptor.Receive.Ring->Tail, Session->Receive.TailRelease);
+    if (ReadAcquire(&Session->Descriptor.Receive.Ring->Alertable))
         SetEvent(Session->Descriptor.Receive.TailMoved);
     LeaveCriticalSection(&Session->Receive.Lock);
 }