dolphin/Source/Core/Common/ucrtFreadWorkaround.cpp

// Copyright 2014 Dolphin Emulator Project
// Licensed under GPLv2+
// Refer to the license.txt file included.

#if defined(_WIN32)

#include <Windows.h>
#include "CommonTypes.h"

struct PatchInfo
{
  const wchar_t* module_name;
  u32 checksum;
  u32 rva;
  u32 length;
} static const s_patches[] = {
    // 10.0.10240.16384 (th1.150709-1700)
    {L"ucrtbase.dll", 0xF61ED, 0x6AE7B, 5},
    // 10.0.10240.16390 (th1_st1.150714-1601)
    {L"ucrtbase.dll", 0xF5ED9, 0x6AE7B, 5},
    // 10.0.10137.0 (th1.150602-2238)
    {L"ucrtbase.dll", 0xF8B5E, 0x63ED6, 2},
    // 10.0.10150.0 (th1.150616-1659)
    {L"ucrtbased.dll", 0x1C1915, 0x91905, 5},
};

bool ApplyPatch(const PatchInfo& patch)
{
  auto module = GetModuleHandleW(patch.module_name);
  if (module == nullptr)
  {
    return false;
  }

  auto ucrtbase_pe = (PIMAGE_NT_HEADERS)((uintptr_t)module + ((PIMAGE_DOS_HEADER)module)->e_lfanew);
  if (ucrtbase_pe->OptionalHeader.CheckSum != patch.checksum)
  {
    return false;
  }

  void* patch_addr = (void*)((uintptr_t)module + patch.rva);
  size_t patch_size = patch.length;

  DWORD old_protect;
  if (!VirtualProtect(patch_addr, patch_size, PAGE_EXECUTE_READWRITE, &old_protect))
  {
    return false;
  }

  memset(patch_addr, 0x90, patch_size);

  VirtualProtect(patch_addr, patch_size, old_protect, &old_protect);

  FlushInstructionCache(GetCurrentProcess(), patch_addr, patch_size);

  return true;
}

int __cdecl EnableucrtFreadWorkaround()
{
  // This patches ucrtbase such that fseek will always
  // synchronize the file object's internal buffer.

  bool applied_at_least_one = false;
  for (const auto& patch : s_patches)
  {
    if (ApplyPatch(patch))
    {
      applied_at_least_one = true;
    }
  }

  /* For forward compat, do not fail if patches don't apply (e.g. version mismatch)
  if (!applied_at_least_one) {
    std::abort();
  }
  //*/

  return 0;
}

// Create a segment which is recognized by the linker to be part of the CRT
// initialization. XI* = C startup, XC* = C++ startup. "A" placement is reserved
// for system use. Thus, the earliest we can get is XIB (C startup is before
// C++).
#pragma section(".CRT$XIB", read)

// Place a symbol in the special segment, make it have C linkage so that
// referencing it doesn't require ugly decorated names.
// Use /include:EnableucrtFreadWorkaround linker flag to enable this.
extern "C" {
__declspec(allocate(".CRT$XIB")) decltype(&EnableucrtFreadWorkaround)
    ucrtFreadWorkaround = EnableucrtFreadWorkaround;
};

#endif