dolphin/Source/Core/Common/MemArena.cpp

// Copyright 2008 Dolphin Emulator Project
// Licensed under GPLv2+
// Refer to the license.txt file included.

#include <cstddef>
#include <cstdlib>
#include <set>
#include <string>

#include "Common/CommonTypes.h"
#include "Common/Logging/Log.h"
#include "Common/MemArena.h"
#include "Common/MsgHandler.h"
#include "Common/StringUtil.h"

#ifdef _WIN32
#include <windows.h>
#else
#include <cerrno>
#include <cstring>
#include <fcntl.h>
#include <sys/mman.h>
#include <unistd.h>
#ifdef ANDROID
#include <linux/ashmem.h>
#include <sys/ioctl.h>
#endif
#endif

#ifdef ANDROID
#define ASHMEM_DEVICE "/dev/ashmem"

static int AshmemCreateFileMapping(const char* name, size_t size)
{
  int fd, ret;
  fd = open(ASHMEM_DEVICE, O_RDWR);
  if (fd < 0)
    return fd;

  // We don't really care if we can't set the name, it is optional
  ioctl(fd, ASHMEM_SET_NAME, name);

  ret = ioctl(fd, ASHMEM_SET_SIZE, size);
  if (ret < 0)
  {
    close(fd);
    NOTICE_LOG(MEMMAP, "Ashmem returned error: 0x%08x", ret);
    return ret;
  }
  return fd;
}
#endif

void MemArena::GrabSHMSegment(size_t size)
{
#ifdef _WIN32
  hMemoryMapping =
      CreateFileMapping(INVALID_HANDLE_VALUE, nullptr, PAGE_READWRITE, 0, (DWORD)(size), nullptr);
#elif defined(ANDROID)
  fd = AshmemCreateFileMapping("Dolphin-emu", size);
  if (fd < 0)
  {
    NOTICE_LOG(MEMMAP, "Ashmem allocation failed");
    return;
  }
#else
  for (int i = 0; i < 10000; i++)
  {
    std::string file_name = StringFromFormat("/dolphinmem.%d", i);
    fd = shm_open(file_name.c_str(), O_RDWR | O_CREAT | O_EXCL, 0600);
    if (fd != -1)
    {
      shm_unlink(file_name.c_str());
      break;
    }
    else if (errno != EEXIST)
    {
      ERROR_LOG(MEMMAP, "shm_open failed: %s", strerror(errno));
      return;
    }
  }
  if (ftruncate(fd, size) < 0)
    ERROR_LOG(MEMMAP, "Failed to allocate low memory space");
#endif
}

void MemArena::ReleaseSHMSegment()
{
#ifdef _WIN32
  CloseHandle(hMemoryMapping);
  hMemoryMapping = 0;
#else
  close(fd);
#endif
}

void* MemArena::CreateView(s64 offset, size_t size, void* base)
{
#ifdef _WIN32
  return MapViewOfFileEx(hMemoryMapping, FILE_MAP_ALL_ACCESS, 0, (DWORD)((u64)offset), size, base);
#else
  void* retval = mmap(base, size, PROT_READ | PROT_WRITE,
                      MAP_SHARED | ((base == nullptr) ? 0 : MAP_FIXED), fd, offset);

  if (retval == MAP_FAILED)
  {
    NOTICE_LOG(MEMMAP, "mmap failed");
    return nullptr;
  }
  else
  {
    return retval;
  }
#endif
}

void MemArena::ReleaseView(void* view, size_t size)
{
#ifdef _WIN32
  UnmapViewOfFile(view);
#else
  munmap(view, size);
#endif
}

u8* MemArena::FindMemoryBase()
{
#if _ARCH_64
#ifdef _WIN32
  // 64 bit
  u8* base = (u8*)VirtualAlloc(0, 0x400000000, MEM_RESERVE, PAGE_READWRITE);
  VirtualFree(base, 0, MEM_RELEASE);
  return base;
#else
  // Very precarious - mmap cannot return an error when trying to map already used pages.
  // This makes the Windows approach above unusable on Linux, so we will simply pray...
  return reinterpret_cast<u8*>(0x2300000000ULL);
#endif

#else  // 32 bit
#ifdef ANDROID
  // 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 support a full SELinux implementation.
  const int flags = MAP_ANON | MAP_SHARED;
#else
  const int flags = MAP_ANON | MAP_PRIVATE;
#endif
  const u32 MemSize = 0x31000000;
  void* base = mmap(0, MemSize, PROT_NONE, flags, -1, 0);
  if (base == MAP_FAILED)
  {
    PanicAlert("Failed to map 1 GB of memory space: %s", strerror(errno));
    return 0;
  }
  munmap(base, MemSize);
  return static_cast<u8*>(base);
#endif
}

// yeah, this could also be done in like two bitwise ops...
#define SKIP(a_flags, b_flags)                                                                     \
  if (!(a_flags & MV_WII_ONLY) && (b_flags & MV_WII_ONLY))                                         \
    continue;                                                                                      \
  if (!(a_flags & MV_FAKE_VMEM) && (b_flags & MV_FAKE_VMEM))                                       \
    continue;

static bool Memory_TryBase(u8* base, MemoryView* views, int num_views, u32 flags, MemArena* arena)
{
  // OK, we know where to find free space. Now grab it!
  // We just mimic the popular BAT setup.

  int i;
  for (i = 0; i < num_views; i++)
  {
    MemoryView* view = &views[i];
    void* view_base;
    bool use_sw_mirror;

    SKIP(flags, view->flags);

#if _ARCH_64
    // On 64-bit, we map the same file position multiple times, so we
    // don't need the software fallback for the mirrors.
    view_base = base + view->virtual_address;
    use_sw_mirror = false;
#else
    // On 32-bit, we don't have the actual address space to store all
    // the mirrors, so we just map the fallbacks somewhere in our address
    // space and use the software fallbacks for mirroring.
    view_base = base + (view->virtual_address & 0x3FFFFFFF);
    use_sw_mirror = true;
#endif

    if (use_sw_mirror && (view->flags & MV_MIRROR_PREVIOUS))
    {
      view->view_ptr = views[i - 1].view_ptr;
    }
    else
    {
      view->mapped_ptr = arena->CreateView(view->shm_position, view->size, view_base);
      view->view_ptr = view->mapped_ptr;
    }

    if (!view->view_ptr)
    {
      // Argh! ERROR! Free what we grabbed so far so we can try again.
      MemoryMap_Shutdown(views, i + 1, flags, arena);
      return false;
    }

    if (view->out_ptr)
      *(view->out_ptr) = (u8*)view->view_ptr;
  }

  return true;
}

static u32 MemoryMap_InitializeViews(MemoryView* views, int num_views, u32 flags)
{
  u32 shm_position = 0;
  u32 last_position = 0;

  for (int i = 0; i < num_views; i++)
  {
    // Zero all the pointers to be sure.
    views[i].mapped_ptr = nullptr;

    SKIP(flags, views[i].flags);

    if (views[i].flags & MV_MIRROR_PREVIOUS)
      shm_position = last_position;
    views[i].shm_position = shm_position;
    last_position = shm_position;
    shm_position += views[i].size;
  }

  return shm_position;
}

u8* MemoryMap_Setup(MemoryView* views, int num_views, u32 flags, MemArena* arena)
{
  u32 total_mem = MemoryMap_InitializeViews(views, num_views, flags);

  arena->GrabSHMSegment(total_mem);

  // Now, create views in high memory where there's plenty of space.
  u8* base = MemArena::FindMemoryBase();
  // This really shouldn't fail - in 64-bit, there will always be enough
  // address space.
  if (!Memory_TryBase(base, views, num_views, flags, arena))
  {
    PanicAlert("MemoryMap_Setup: Failed finding a memory base.");
    exit(0);
    return nullptr;
  }

  return base;
}

void MemoryMap_Shutdown(MemoryView* views, int num_views, u32 flags, MemArena* arena)
{
  std::set<void*> freeset;
  for (int i = 0; i < num_views; i++)
  {
    MemoryView* view = &views[i];
    if (view->mapped_ptr && !freeset.count(view->mapped_ptr))
    {
      arena->ReleaseView(view->mapped_ptr, view->size);
      freeset.insert(view->mapped_ptr);
      view->mapped_ptr = nullptr;
    }
  }
}