MemArena: Prepare interface for proper memory reservation.

Source/Core/Common/MemArena.h

@@ -15,18 +15,87 @@ namespace Common
 {
 // This class lets you create a block of anonymous RAM, and then arbitrarily map views into it.
 // Multiple views can mirror the same section of the block, which makes it very convenient for
-// emulating
+// emulating memory mirrors.
-// memory mirrors.
+class MemArena final
-class MemArena
 {
 public:
+  MemArena();
+  ~MemArena();
+  MemArena(const MemArena&) = delete;
+  MemArena(MemArena&&) = delete;
+  MemArena& operator=(const MemArena&) = delete;
+  MemArena& operator=(MemArena&&) = delete;
+
+  ///
+  /// Allocate the singular memory segment handled by this MemArena. This will be the actual
+  /// 'physical' available memory for this arena. After allocation, it can be interacted with using
+  /// CreateView() and ReleaseView(). Used to make a mappable region for emulated memory.
+  ///
+  /// @param size The amount of bytes that should be allocated in this region.
+  ///
   void GrabSHMSegment(size_t size);
+
+  ///
+  /// Release the memory segment previously allocated with GrabSHMSegment().
+  /// Should not be called before all views have been released.
+  ///
   void ReleaseSHMSegment();
-  void* CreateView(s64 offset, size_t size, void* base = nullptr);
+
+  ///
+  /// Map a memory region in the memory segment previously allocated with GrabSHMSegment().
+  ///
+  /// @param offset Offset within the memory segment to map at.
+  /// @param size Size of the region to map.
+  ///
+  /// @return Pointer to the memory region, or nullptr on failure.
+  ///
+  void* CreateView(s64 offset, size_t size);
+
+  ///
+  /// Unmap a memory region previously mapped with CreateView().
+  /// Should not be called on a view that is still mapped into the virtual memory region.
+  ///
+  /// @param view Pointer returned by CreateView().
+  /// @param size Size passed to the corresponding CreateView() call.
+  ///
   void ReleaseView(void* view, size_t size);
 
-  // This finds 1 GB in 32-bit, 16 GB in 64-bit.
+  ///
-  static u8* FindMemoryBase();
+  /// Reserve the singular 'virtual' memory region handled by this MemArena. This is used to create
+  /// our 'fastmem' memory area for the emulated game code to access directly.
+  ///
+  /// @param memory_size Size in bytes of the memory region to reserve.
+  ///
+  /// @return Pointer to the memory region, or nullptr on failure.
+  ///
+  u8* ReserveMemoryRegion(size_t memory_size);
+
+  ///
+  /// Release the memory region previously reserved with ReserveMemoryRegion().
+  /// Should not be called while any memory region is still mapped.
+  ///
+  void ReleaseMemoryRegion();
+
+  ///
+  /// Map a section from the memory segment previously allocated with GrabSHMSegment()
+  /// into the region previously reserved with ReserveMemoryRegion().
+  ///
+  /// @param offset Offset within the memory segment previous allocated by GrabSHMSegment() to map
+  /// from.
+  /// @param size Size of the region to map.
+  /// @param base Address within the memory region from ReserveMemoryRegion() where to map it.
+  ///
+  /// @return The address we actually ended up mapping, which should be the given 'base'.
+  ///
+  void* MapInMemoryRegion(s64 offset, size_t size, void* base);
+
+  ///
+  /// Unmap a memory region previously mapped with MapInMemoryRegion().
+  ///
+  /// @param view Pointer returned by MapInMemoryRegion().
+  /// @param size Size passed to the corresponding MapInMemoryRegion() call.
+  ///
+  void UnmapFromMemoryRegion(void* view, size_t size);
 
 private:
 #ifdef _WIN32

Source/Core/Common/MemArenaAndroid.cpp

@@ -59,6 +59,9 @@ static int AshmemCreateFileMapping(const char* name, size_t size)
   return fd;
 }
 
+MemArena::MemArena() = default;
+MemArena::~MemArena() = default;
+
 void MemArena::GrabSHMSegment(size_t size)
 {
   fd = AshmemCreateFileMapping(("dolphin-emu." + std::to_string(getpid())).c_str(), size);
@@ -71,7 +74,37 @@ void MemArena::ReleaseSHMSegment()
   close(fd);
 }
 
-void* MemArena::CreateView(s64 offset, size_t size, void* base)
+void* MemArena::CreateView(s64 offset, size_t size)
+{
+  return MapInMemoryRegion(offset, size, nullptr);
+}
+
+void MemArena::ReleaseView(void* view, size_t size)
+{
+  UnmapFromMemoryRegion(view, size);
+}
+
+u8* MemArena::ReserveMemoryRegion(size_t memory_size)
+{
+  // Android 4.3 changed how mmap works.
+  // if we map it private and then munmap it, we can't use the base returned.
+  // This may be due to changes in them to support a full SELinux implementation.
+  const int flags = MAP_ANON | MAP_SHARED;
+  void* base = mmap(nullptr, memory_size, PROT_NONE, flags, -1, 0);
+  if (base == MAP_FAILED)
+  {
+    PanicAlertFmt("Failed to map enough memory space: {}", LastStrerrorString());
+    return nullptr;
+  }
+  munmap(base, memory_size);
+  return static_cast<u8*>(base);
+}
+
+void MemArena::ReleaseMemoryRegion()
+{
+}
+
+void* MemArena::MapInMemoryRegion(s64 offset, size_t size, void* base)
 {
   void* retval = mmap(base, size, PROT_READ | PROT_WRITE,
                       MAP_SHARED | ((base == nullptr) ? 0 : MAP_FIXED), fd, offset);
@@ -87,30 +120,8 @@ void* MemArena::CreateView(s64 offset, size_t size, void* base)
   }
 }
 
-void MemArena::ReleaseView(void* view, size_t size)
+void MemArena::UnmapFromMemoryRegion(void* view, size_t size)
 {
   munmap(view, size);
 }
-
-u8* MemArena::FindMemoryBase()
-{
-#if _ARCH_32
-  const size_t memory_size = 0x31000000;
-#else
-  const size_t memory_size = 0x400000000;
-#endif
-
-  // Android 4.3 changed how mmap works.
-  // if we map it private and then munmap it, we can't use the base returned.
-  // This may be due to changes in them to support a full SELinux implementation.
-  const int flags = MAP_ANON | MAP_SHARED;
-  void* base = mmap(nullptr, memory_size, PROT_NONE, flags, -1, 0);
-  if (base == MAP_FAILED)
-  {
-    PanicAlertFmt("Failed to map enough memory space: {}", LastStrerrorString());
-    return nullptr;
-  }
-  munmap(base, memory_size);
-  return static_cast<u8*>(base);
-}
 }  // namespace Common

Source/Core/Common/MemArenaUnix.cpp

@@ -22,6 +22,9 @@
 
 namespace Common
 {
+MemArena::MemArena() = default;
+MemArena::~MemArena() = default;
+
 void MemArena::GrabSHMSegment(size_t size)
 {
   const std::string file_name = "/dolphin-emu." + std::to_string(getpid());
@@ -41,7 +44,34 @@ void MemArena::ReleaseSHMSegment()
   close(fd);
 }
 
-void* MemArena::CreateView(s64 offset, size_t size, void* base)
+void* MemArena::CreateView(s64 offset, size_t size)
+{
+  return MapInMemoryRegion(offset, size, nullptr);
+}
+
+void MemArena::ReleaseView(void* view, size_t size)
+{
+  UnmapFromMemoryRegion(view, size);
+}
+
+u8* MemArena::ReserveMemoryRegion(size_t memory_size)
+{
+  const int flags = MAP_ANON | MAP_PRIVATE;
+  void* base = mmap(nullptr, memory_size, PROT_NONE, flags, -1, 0);
+  if (base == MAP_FAILED)
+  {
+    PanicAlertFmt("Failed to map enough memory space: {}", LastStrerrorString());
+    return nullptr;
+  }
+  munmap(base, memory_size);
+  return static_cast<u8*>(base);
+}
+
+void MemArena::ReleaseMemoryRegion()
+{
+}
+
+void* MemArena::MapInMemoryRegion(s64 offset, size_t size, void* base)
 {
   void* retval = mmap(base, size, PROT_READ | PROT_WRITE,
                       MAP_SHARED | ((base == nullptr) ? 0 : MAP_FIXED), fd, offset);
@@ -57,27 +87,8 @@ void* MemArena::CreateView(s64 offset, size_t size, void* base)
   }
 }
 
-void MemArena::ReleaseView(void* view, size_t size)
+void MemArena::UnmapFromMemoryRegion(void* view, size_t size)
 {
   munmap(view, size);
 }
-
-u8* MemArena::FindMemoryBase()
-{
-#if _ARCH_32
-  const size_t memory_size = 0x31000000;
-#else
-  const size_t memory_size = 0x400000000;
-#endif
-
-  const int flags = MAP_ANON | MAP_PRIVATE;
-  void* base = mmap(nullptr, memory_size, PROT_NONE, flags, -1, 0);
-  if (base == MAP_FAILED)
-  {
-    PanicAlertFmt("Failed to map enough memory space: {}", LastStrerrorString());
-    return nullptr;
-  }
-  munmap(base, memory_size);
-  return static_cast<u8*>(base);
-}
 }  // namespace Common

Source/Core/Common/MemArenaWin.cpp

@@ -18,6 +18,9 @@
 
 namespace Common
 {
+MemArena::MemArena() = default;
+MemArena::~MemArena() = default;
+
 void MemArena::GrabSHMSegment(size_t size)
 {
   const std::string name = "dolphin-emu." + std::to_string(GetCurrentProcessId());
@@ -31,24 +34,18 @@ void MemArena::ReleaseSHMSegment()
   hMemoryMapping = 0;
 }
 
-void* MemArena::CreateView(s64 offset, size_t size, void* base)
+void* MemArena::CreateView(s64 offset, size_t size)
 {
-  return MapViewOfFileEx(hMemoryMapping, FILE_MAP_ALL_ACCESS, 0, (DWORD)((u64)offset), size, base);
+  return MapInMemoryRegion(offset, size, nullptr);
 }
 
 void MemArena::ReleaseView(void* view, size_t size)
 {
-  UnmapViewOfFile(view);
+  UnmapFromMemoryRegion(view, size);
 }
 
-u8* MemArena::FindMemoryBase()
+u8* MemArena::ReserveMemoryRegion(size_t memory_size)
 {
-#if _ARCH_32
-  const size_t memory_size = 0x31000000;
-#else
-  const size_t memory_size = 0x400000000;
-#endif
-
   u8* base = static_cast<u8*>(VirtualAlloc(nullptr, memory_size, MEM_RESERVE, PAGE_READWRITE));
   if (!base)
   {
@@ -58,4 +55,18 @@ u8* MemArena::FindMemoryBase()
   VirtualFree(base, 0, MEM_RELEASE);
   return base;
 }
+
+void MemArena::ReleaseMemoryRegion()
+{
+}
+
+void* MemArena::MapInMemoryRegion(s64 offset, size_t size, void* base)
+{
+  return MapViewOfFileEx(hMemoryMapping, FILE_MAP_ALL_ACCESS, 0, (DWORD)((u64)offset), size, base);
+}
+
+void MemArena::UnmapFromMemoryRegion(void* view, size_t size)
+{
+  UnmapViewOfFile(view);
+}
 }  // namespace Common

Source/Core/Core/HW/Memmap.cpp

@@ -314,7 +314,12 @@ void Init()
 
 bool InitFastmemArena()
 {
-  physical_base = Common::MemArena::FindMemoryBase();
+#if _ARCH_32
+  const size_t memory_size = 0x31000000;
+#else
+  const size_t memory_size = 0x400000000;
+#endif
+  physical_base = g_arena.ReserveMemoryRegion(memory_size);
 
   if (!physical_base)
   {
@@ -328,7 +333,7 @@ bool InitFastmemArena()
       continue;
 
     u8* base = physical_base + region.physical_address;
-    u8* view = (u8*)g_arena.CreateView(region.shm_position, region.size, base);
+    u8* view = (u8*)g_arena.MapInMemoryRegion(region.shm_position, region.size, base);
 
     if (base != view)
     {
@@ -354,7 +359,7 @@ void UpdateLogicalMemory(const PowerPC::BatTable& dbat_table)
 
   for (auto& entry : logical_mapped_entries)
   {
-    g_arena.ReleaseView(entry.mapped_pointer, entry.mapped_size);
+    g_arena.UnmapFromMemoryRegion(entry.mapped_pointer, entry.mapped_size);
   }
   logical_mapped_entries.clear();
   for (u32 i = 0; i < dbat_table.size(); ++i)
@@ -381,7 +386,7 @@ void UpdateLogicalMemory(const PowerPC::BatTable& dbat_table)
           u8* base = logical_base + logical_address + intersection_start - translated_address;
           u32 mapped_size = intersection_end - intersection_start;
 
-          void* mapped_pointer = g_arena.CreateView(position, mapped_size, base);
+          void* mapped_pointer = g_arena.MapInMemoryRegion(position, mapped_size, base);
           if (!mapped_pointer)
           {
             PanicAlertFmt("Memory::UpdateLogicalMemory(): Failed to map memory region at 0x{:08X} "
@@ -439,15 +444,17 @@ void ShutdownFastmemArena()
       continue;
 
     u8* base = physical_base + region.physical_address;
-    g_arena.ReleaseView(base, region.size);
+    g_arena.UnmapFromMemoryRegion(base, region.size);
   }
 
   for (auto& entry : logical_mapped_entries)
   {
-    g_arena.ReleaseView(entry.mapped_pointer, entry.mapped_size);
+    g_arena.UnmapFromMemoryRegion(entry.mapped_pointer, entry.mapped_size);
   }
   logical_mapped_entries.clear();
 
+  g_arena.ReleaseMemoryRegion();
+
   physical_base = nullptr;
   logical_base = nullptr;