duckstation/src/common/memmap.cpp

// SPDX-FileCopyrightText: 2019-2023 Connor McLaughlin <stenzek@gmail.com>
// SPDX-License-Identifier: (GPL-3.0 OR CC-BY-NC-ND-4.0)

#include "memmap.h"
#include "align.h"
#include "assert.h"
#include "log.h"
#include "string_util.h"

#include "fmt/format.h"

#if defined(_WIN32)
#include "windows_headers.h"
#elif !defined(__ANDROID__)
#include <cerrno>
#include <fcntl.h>
#include <sys/mman.h>
#include <unistd.h>
#endif

Log_SetChannel(MemoryArena);

#ifdef _WIN32

bool MemMap::MemProtect(void* baseaddr, size_t size, PageProtect mode)
{
  DebugAssert((size & (HOST_PAGE_SIZE - 1)) == 0);

  DWORD old_protect;
  if (!VirtualProtect(baseaddr, size, static_cast<DWORD>(mode), &old_protect))
  {
    Log_ErrorPrintf("VirtualProtect() failed with error %u", GetLastError());
    return false;
  }

  return true;
}

std::string MemMap::GetFileMappingName(const char* prefix)
{
  const unsigned pid = GetCurrentProcessId();
  return fmt::format("{}_{}", prefix, pid);
}

void* MemMap::CreateSharedMemory(const char* name, size_t size)
{
  return static_cast<void*>(CreateFileMappingW(INVALID_HANDLE_VALUE, NULL, PAGE_READWRITE,
                                               static_cast<DWORD>(size >> 32), static_cast<DWORD>(size),
                                               StringUtil::UTF8StringToWideString(name).c_str()));
}

void MemMap::DestroySharedMemory(void* ptr)
{
  CloseHandle(static_cast<HANDLE>(ptr));
}

void* MemMap::MapSharedMemory(void* handle, size_t offset, void* baseaddr, size_t size, PageProtect mode)
{
  void* ret = MapViewOfFileEx(static_cast<HANDLE>(handle), FILE_MAP_READ | FILE_MAP_WRITE,
                              static_cast<DWORD>(offset >> 32), static_cast<DWORD>(offset), size, baseaddr);
  if (!ret)
    return nullptr;

  if (mode != PageProtect::ReadWrite)
  {
    DWORD old_prot;
    if (!VirtualProtect(ret, size, static_cast<DWORD>(mode), &old_prot))
      Panic("Failed to protect memory mapping");
  }
  return ret;
}

void MemMap::UnmapSharedMemory(void* baseaddr, size_t size)
{
  if (!UnmapViewOfFile(baseaddr))
    Panic("Failed to unmap shared memory");
}

SharedMemoryMappingArea::SharedMemoryMappingArea() = default;

SharedMemoryMappingArea::~SharedMemoryMappingArea()
{
  Destroy();
}

SharedMemoryMappingArea::PlaceholderMap::iterator SharedMemoryMappingArea::FindPlaceholder(size_t offset)
{
  if (m_placeholder_ranges.empty())
    return m_placeholder_ranges.end();

  // this will give us an iterator equal or after page
  auto it = m_placeholder_ranges.lower_bound(offset);
  if (it == m_placeholder_ranges.end())
  {
    // check the last page
    it = (++m_placeholder_ranges.rbegin()).base();
  }

  // it's the one we found?
  if (offset >= it->first && offset < it->second)
    return it;

  // otherwise try the one before
  if (it == m_placeholder_ranges.begin())
    return m_placeholder_ranges.end();

  --it;
  if (offset >= it->first && offset < it->second)
    return it;
  else
    return m_placeholder_ranges.end();
}

bool SharedMemoryMappingArea::Create(size_t size)
{
  Destroy();

  AssertMsg(Common::IsAlignedPow2(size, HOST_PAGE_SIZE), "Size is page aligned");

  m_base_ptr = static_cast<u8*>(VirtualAlloc2(GetCurrentProcess(), nullptr, size, MEM_RESERVE | MEM_RESERVE_PLACEHOLDER,
                                              PAGE_NOACCESS, nullptr, 0));
  if (!m_base_ptr)
    return false;

  m_size = size;
  m_num_pages = size / HOST_PAGE_SIZE;
  m_placeholder_ranges.emplace(0, size);
  return true;
}

void SharedMemoryMappingArea::Destroy()
{
  AssertMsg(m_num_mappings == 0, "No mappings left");

  // hopefully this will be okay, and we don't need to coalesce all the placeholders...
  if (m_base_ptr && !VirtualFreeEx(GetCurrentProcess(), m_base_ptr, 0, MEM_RELEASE))
    Panic("Failed to release shared memory area");

  m_placeholder_ranges.clear();
  m_base_ptr = nullptr;
  m_size = 0;
  m_num_pages = 0;
  m_num_mappings = 0;
}

u8* SharedMemoryMappingArea::Map(void* file_handle, size_t file_offset, void* map_base, size_t map_size,
                                 PageProtect mode)
{
  DebugAssert(static_cast<u8*>(map_base) >= m_base_ptr && static_cast<u8*>(map_base) < (m_base_ptr + m_size));

  const size_t map_offset = static_cast<u8*>(map_base) - m_base_ptr;
  DebugAssert(Common::IsAlignedPow2(map_offset, HOST_PAGE_SIZE));
  DebugAssert(Common::IsAlignedPow2(map_size, HOST_PAGE_SIZE));

  // should be a placeholder. unless there's some other mapping we didn't free.
  PlaceholderMap::iterator phit = FindPlaceholder(map_offset);
  DebugAssertMsg(phit != m_placeholder_ranges.end(), "Page we're mapping is a placeholder");
  DebugAssertMsg(map_offset >= phit->first && map_offset < phit->second, "Page is in returned placeholder range");
  DebugAssertMsg((map_offset + map_size) <= phit->second, "Page range is in returned placeholder range");

  // do we need to split to the left? (i.e. is there a placeholder before this range)
  const size_t old_ph_end = phit->second;
  if (map_offset != phit->first)
  {
    phit->second = map_offset;

    // split it (i.e. left..start and start..end are now separated)
    if (!VirtualFreeEx(GetCurrentProcess(), OffsetPointer(phit->first), (map_offset - phit->first),
                       MEM_RELEASE | MEM_PRESERVE_PLACEHOLDER))
    {
      Panic("Failed to left split placeholder for map");
    }
  }
  else
  {
    // start of the placeholder is getting used, we'll split it right below if there's anything left over
    m_placeholder_ranges.erase(phit);
  }

  // do we need to split to the right? (i.e. is there a placeholder after this range)
  if ((map_offset + map_size) != old_ph_end)
  {
    // split out end..ph_end
    m_placeholder_ranges.emplace(map_offset + map_size, old_ph_end);

    if (!VirtualFreeEx(GetCurrentProcess(), OffsetPointer(map_offset), map_size,
                       MEM_RELEASE | MEM_PRESERVE_PLACEHOLDER))
    {
      Panic("Failed to right split placeholder for map");
    }
  }

  // actually do the mapping, replacing the placeholder on the range
  if (!MapViewOfFile3(static_cast<HANDLE>(file_handle), GetCurrentProcess(), map_base, file_offset, map_size,
                      MEM_REPLACE_PLACEHOLDER, PAGE_READWRITE, nullptr, 0))
  {
    Log_ErrorPrintf("MapViewOfFile3() failed: %u", GetLastError());
    return nullptr;
  }

  if (mode != PageProtect::ReadWrite)
  {
    DWORD old_prot;
    if (!VirtualProtect(map_base, map_size, static_cast<DWORD>(mode), &old_prot))
      Panic("Failed to protect memory mapping");
  }

  m_num_mappings++;
  return static_cast<u8*>(map_base);
}

bool SharedMemoryMappingArea::Unmap(void* map_base, size_t map_size)
{
  DebugAssert(static_cast<u8*>(map_base) >= m_base_ptr && static_cast<u8*>(map_base) < (m_base_ptr + m_size));

  const size_t map_offset = static_cast<u8*>(map_base) - m_base_ptr;
  DebugAssert(Common::IsAlignedPow2(map_offset, HOST_PAGE_SIZE));
  DebugAssert(Common::IsAlignedPow2(map_size, HOST_PAGE_SIZE));

  // unmap the specified range
  if (!UnmapViewOfFile2(GetCurrentProcess(), map_base, MEM_PRESERVE_PLACEHOLDER))
  {
    Log_ErrorPrintf("UnmapViewOfFile2() failed: %u", GetLastError());
    return false;
  }

  // can we coalesce to the left?
  PlaceholderMap::iterator left_it = (map_offset > 0) ? FindPlaceholder(map_offset - 1) : m_placeholder_ranges.end();
  if (left_it != m_placeholder_ranges.end())
  {
    // the left placeholder should end at our start
    DebugAssert(map_offset == left_it->second);
    left_it->second = map_offset + map_size;

    // combine placeholders before and the range we're unmapping, i.e. to the left
    if (!VirtualFreeEx(GetCurrentProcess(), OffsetPointer(left_it->first), left_it->second - left_it->first,
                       MEM_RELEASE | MEM_COALESCE_PLACEHOLDERS))
    {
      Panic("Failed to coalesce placeholders left for unmap");
    }
  }
  else
  {
    // this is a new placeholder
    left_it = m_placeholder_ranges.emplace(map_offset, map_offset + map_size).first;
  }

  // can we coalesce to the right?
  PlaceholderMap::iterator right_it =
    ((map_offset + map_size) < m_size) ? FindPlaceholder(map_offset + map_size) : m_placeholder_ranges.end();
  if (right_it != m_placeholder_ranges.end())
  {
    // should start at our end
    DebugAssert(right_it->first == (map_offset + map_size));
    left_it->second = right_it->second;
    m_placeholder_ranges.erase(right_it);

    // combine our placeholder and the next, i.e. to the right
    if (!VirtualFreeEx(GetCurrentProcess(), OffsetPointer(left_it->first), left_it->second - left_it->first,
                       MEM_RELEASE | MEM_COALESCE_PLACEHOLDERS))
    {
      Panic("Failed to coalescae placeholders right for unmap");
    }
  }

  m_num_mappings--;
  return true;
}

#else

bool MemMap::MemProtect(void* baseaddr, size_t size, PageProtect mode)
{
  DebugAssertMsg((size & (HOST_PAGE_SIZE - 1)) == 0, "Size is page aligned");

  const int result = mprotect(baseaddr, size, static_cast<int>(mode));
  if (result != 0)
  {
    Log_ErrorPrintf("mprotect() for %zu at %p failed", size, baseaddr);
    return false;
  }

  return true;
}

std::string MemMap::GetFileMappingName(const char* prefix)
{
  const unsigned pid = static_cast<unsigned>(getpid());
#if defined(__FreeBSD__)
  // FreeBSD's shm_open(3) requires name to be absolute
  return fmt::format("/tmp/{}_{}", prefix, pid);
#else
  return fmt::format("{}_{}", prefix, pid);
#endif
}

void* MemMap::CreateSharedMemory(const char* name, size_t size)
{
  const int fd = shm_open(name, O_CREAT | O_EXCL | O_RDWR, 0600);
  if (fd < 0)
  {
    Log_ErrorPrintf("shm_open failed: %d\n", errno);
    return nullptr;
  }

  // we're not going to be opening this mapping in other processes, so remove the file
  shm_unlink(name);

  // ensure it's the correct size
  if (ftruncate(fd, static_cast<off_t>(size)) < 0)
  {
    Log_ErrorPrintf("ftruncate(%zu) failed: %d\n", size, errno);
    return nullptr;
  }

  return reinterpret_cast<void*>(static_cast<intptr_t>(fd));
}

void MemMap::DestroySharedMemory(void* ptr)
{
  close(static_cast<int>(reinterpret_cast<intptr_t>(ptr)));
}

void* MemMap::MapSharedMemory(void* handle, size_t offset, void* baseaddr, size_t size, PageProtect mode)
{
  const int flags = (baseaddr != nullptr) ? (MAP_SHARED | MAP_FIXED) : MAP_SHARED;
  void* ptr = mmap(baseaddr, size, static_cast<int>(mode), flags, static_cast<int>(reinterpret_cast<intptr_t>(handle)),
                   static_cast<off_t>(offset));
  if (ptr == MAP_FAILED)
    return nullptr;

  return ptr;
}

void MemMap::UnmapSharedMemory(void* baseaddr, size_t size)
{
  if (mmap(baseaddr, size, PROT_NONE, MAP_PRIVATE | MAP_ANONYMOUS | MAP_FIXED, -1, 0) == MAP_FAILED)
    Panic("Failed to unmap shared memory");
}

SharedMemoryMappingArea::SharedMemoryMappingArea() = default;

SharedMemoryMappingArea::~SharedMemoryMappingArea()
{
  Destroy();
}

bool SharedMemoryMappingArea::Create(size_t size)
{
  AssertMsg(Common::IsAlignedPow2(size, HOST_PAGE_SIZE), "Size is page aligned");
  Destroy();

  void* alloc = mmap(nullptr, size, PROT_NONE, MAP_ANONYMOUS | MAP_PRIVATE, -1, 0);
  if (alloc == MAP_FAILED)
    return false;

  m_base_ptr = static_cast<u8*>(alloc);
  m_size = size;
  m_num_pages = size / HOST_PAGE_SIZE;
  return true;
}

void SharedMemoryMappingArea::Destroy()
{
  AssertMsg(m_num_mappings == 0, "No mappings left");

  if (m_base_ptr && munmap(m_base_ptr, m_size) != 0)
    Panic("Failed to release shared memory area");

  m_base_ptr = nullptr;
  m_size = 0;
  m_num_pages = 0;
}

u8* SharedMemoryMappingArea::Map(void* file_handle, size_t file_offset, void* map_base, size_t map_size,
                                 PageProtect mode)
{
  DebugAssert(static_cast<u8*>(map_base) >= m_base_ptr && static_cast<u8*>(map_base) < (m_base_ptr + m_size));

  void* const ptr = mmap(map_base, map_size, static_cast<int>(mode), MAP_SHARED | MAP_FIXED,
                         static_cast<int>(reinterpret_cast<intptr_t>(file_handle)), static_cast<off_t>(file_offset));
  if (ptr == MAP_FAILED)
    return nullptr;

  m_num_mappings++;
  return static_cast<u8*>(ptr);
}

bool SharedMemoryMappingArea::Unmap(void* map_base, size_t map_size)
{
  DebugAssert(static_cast<u8*>(map_base) >= m_base_ptr && static_cast<u8*>(map_base) < (m_base_ptr + m_size));

  if (mmap(map_base, map_size, PROT_NONE, MAP_PRIVATE | MAP_ANONYMOUS | MAP_FIXED, -1, 0) == MAP_FAILED)
    return false;

  m_num_mappings--;
  return true;
}

#endif