From ab98db445d67491ac63196686b73fb279f71984f Mon Sep 17 00:00:00 2001
From: "Admiral H. Curtiss" <pikachu025@gmail.com>
Date: Thu, 11 May 2023 02:41:40 +0200
Subject: [PATCH] Common/MemArenaAndroid: Keep fastmem region mapped.

---
 Source/Core/Common/MemArena.h          | 10 +++-----
 Source/Core/Common/MemArenaAndroid.cpp | 35 ++++++++++++++++++--------
 2 files changed, 28 insertions(+), 17 deletions(-)

diff --git a/Source/Core/Common/MemArena.h b/Source/Core/Common/MemArena.h
index e365b78e0b..01b1b5c06b 100644
--- a/Source/Core/Common/MemArena.h
+++ b/Source/Core/Common/MemArena.h
@@ -113,13 +113,9 @@ private:
   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
+  int m_shm_fd = 0;
+  void* m_reserved_region = nullptr;
+  std::size_t m_reserved_region_size = 0;
 #endif
 };
 
diff --git a/Source/Core/Common/MemArenaAndroid.cpp b/Source/Core/Common/MemArenaAndroid.cpp
index aca94db173..721925d213 100644
--- a/Source/Core/Common/MemArenaAndroid.cpp
+++ b/Source/Core/Common/MemArenaAndroid.cpp
@@ -64,24 +64,33 @@ MemArena::~MemArena() = default;
 
 void MemArena::GrabSHMSegment(size_t size)
 {
-  fd = AshmemCreateFileMapping(("dolphin-emu." + std::to_string(getpid())).c_str(), size);
-  if (fd < 0)
+  m_shm_fd = AshmemCreateFileMapping(("dolphin-emu." + std::to_string(getpid())).c_str(), size);
+  if (m_shm_fd < 0)
     NOTICE_LOG_FMT(MEMMAP, "Ashmem allocation failed");
 }
 
 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)
@@ -96,19 +105,23 @@ 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");
@@ -122,6 +135,8 @@ 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_SHARED | MAP_ANONYMOUS | MAP_FIXED, -1, 0);
+  if (retval == MAP_FAILED)
+    NOTICE_LOG_FMT(MEMMAP, "mmap failed");
 }
 }  // namespace Common