Merge pull request #9834 from AdmiralCurtiss/fastmem-reserve-region-l…

…inux

MemArena: Keep fastmem memory region mapped on Linux to ensure nothing allocates within the fastmem space.

Source/Core/Common/MemArena.h

@@ -113,7 +113,13 @@ class MemArena final
   void* m_address_VirtualAlloc2 = nullptr;
   void* m_address_MapViewOfFile3 = nullptr;
 #else
+#ifdef ANDROID
   int fd;
+#else
+  int m_shm_fd;
+  void* m_reserved_region;
+  std::size_t m_reserved_region_size;
+#endif
 #endif
 };
 

Source/Core/Common/MemArenaUnix.cpp

@@ -28,30 +28,39 @@ MemArena::~MemArena() = default;
 void MemArena::GrabSHMSegment(size_t size)
 {
   const std::string file_name = "/dolphin-emu." + std::to_string(getpid());
-  fd = shm_open(file_name.c_str(), O_RDWR | O_CREAT | O_EXCL, 0600);
-  if (fd == -1)
+  m_shm_fd = shm_open(file_name.c_str(), O_RDWR | O_CREAT | O_EXCL, 0600);
+  if (m_shm_fd == -1)
   {
     ERROR_LOG_FMT(MEMMAP, "shm_open failed: {}", strerror(errno));
     return;
   }
   shm_unlink(file_name.c_str());
-  if (ftruncate(fd, size) < 0)
+  if (ftruncate(m_shm_fd, size) < 0)
     ERROR_LOG_FMT(MEMMAP, "Failed to allocate low memory space");
 }
 
 void MemArena::ReleaseSHMSegment()
 {
-  close(fd);
+  close(m_shm_fd);
 }
 
 void* MemArena::CreateView(s64 offset, size_t size)
 {
-  return MapInMemoryRegion(offset, size, nullptr);
+  void* retval = mmap(nullptr, size, PROT_READ | PROT_WRITE, MAP_SHARED, m_shm_fd, offset);
+  if (retval == MAP_FAILED)
+  {
+    NOTICE_LOG_FMT(MEMMAP, "mmap failed");
+    return nullptr;
+  }
+  else
+  {
+    return retval;
+  }
 }
 
 void MemArena::ReleaseView(void* view, size_t size)
 {
-  UnmapFromMemoryRegion(view, size);
+  munmap(view, size);
 }
 
 u8* MemArena::ReserveMemoryRegion(size_t memory_size)
@@ -63,19 +72,23 @@ u8* MemArena::ReserveMemoryRegion(size_t memory_size)
     PanicAlertFmt("Failed to map enough memory space: {}", LastStrerrorString());
     return nullptr;
   }
-  munmap(base, memory_size);
+  m_reserved_region = base;
+  m_reserved_region_size = memory_size;
   return static_cast<u8*>(base);
 }
 
 void MemArena::ReleaseMemoryRegion()
 {
+  if (m_reserved_region)
+  {
+    munmap(m_reserved_region, m_reserved_region_size);
+    m_reserved_region = nullptr;
+  }
 }
 
 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);
-
+  void* retval = mmap(base, size, PROT_READ | PROT_WRITE, MAP_SHARED | MAP_FIXED, m_shm_fd, offset);
   if (retval == MAP_FAILED)
   {
     NOTICE_LOG_FMT(MEMMAP, "mmap failed");
@@ -89,6 +102,8 @@ void* MemArena::MapInMemoryRegion(s64 offset, size_t size, void* base)
 
 void MemArena::UnmapFromMemoryRegion(void* view, size_t size)
 {
-  munmap(view, size);
+  void* retval = mmap(view, size, PROT_NONE, MAP_PRIVATE | MAP_ANONYMOUS | MAP_FIXED, -1, 0);
+  if (retval == MAP_FAILED)
+    NOTICE_LOG_FMT(MEMMAP, "mmap failed");
 }
 }  // namespace Common