windows: prefer os version from registry

this value is not modified by compatibility mode
drop reporting service pack numbers. no longer used

Source/Core/Common/WindowsRegistry.cpp

@@ -0,0 +1,72 @@
+#include "Common/WindowsRegistry.h"
+
+#include <Windows.h>
+#include <string>
+#include <type_traits>
+#include "Common/StringUtil.h"
+
+namespace WindowsRegistry
+{
+template <typename T>
+bool ReadValue(T* value, const std::string& subkey, const std::string& name)
+{
+  DWORD flags = 0;
+  static_assert(std::is_integral_v<T> && (sizeof(T) == sizeof(u32) || sizeof(T) == sizeof(u64)),
+                "Unsupported type");
+  if constexpr (sizeof(T) == sizeof(u32))
+    flags = RRF_RT_REG_DWORD;
+  else if constexpr (sizeof(T) == sizeof(u64))
+    flags = RRF_RT_REG_QWORD;
+
+  DWORD value_len = sizeof(*value);
+  return RegGetValueA(HKEY_LOCAL_MACHINE, subkey.c_str(), name.c_str(), flags, nullptr, value,
+                      &value_len) == ERROR_SUCCESS;
+}
+
+template <>
+bool ReadValue(std::string* value, const std::string& subkey, const std::string& name)
+{
+  const DWORD flags = RRF_RT_REG_SZ | RRF_NOEXPAND;
+  DWORD value_len = 0;
+  auto status = RegGetValueA(HKEY_LOCAL_MACHINE, subkey.c_str(), name.c_str(), flags, nullptr,
+                             nullptr, &value_len);
+  if (status != ERROR_SUCCESS && status != ERROR_MORE_DATA)
+    return false;
+
+  value->resize(value_len);
+  status = RegGetValueA(HKEY_LOCAL_MACHINE, subkey.c_str(), name.c_str(), flags, nullptr,
+                        value->data(), &value_len);
+  if (status != ERROR_SUCCESS)
+  {
+    value->clear();
+    return false;
+  }
+
+  TruncateToCString(value);
+  return true;
+}
+
+OSVERSIONINFOW GetOSVersion()
+{
+  // PEB may have faked data if the binary is launched with "compatibility mode" enabled.
+  // Try to read real OS version from registry.
+  const char* subkey = R"(SOFTWARE\Microsoft\Windows NT\CurrentVersion)";
+  OSVERSIONINFOW info{.dwOSVersionInfoSize = sizeof(info)};
+  std::string build_str;
+  if (!ReadValue(&info.dwMajorVersion, subkey, "CurrentMajorVersionNumber") ||
+      !ReadValue(&info.dwMinorVersion, subkey, "CurrentMinorVersionNumber") ||
+      !ReadValue(&build_str, subkey, "CurrentBuildNumber") ||
+      !TryParse(build_str, &info.dwBuildNumber))
+  {
+    // Fallback to version from PEB
+    typedef DWORD(WINAPI * RtlGetVersion_t)(PRTL_OSVERSIONINFOW);
+    auto RtlGetVersion =
+        (RtlGetVersion_t)GetProcAddress(GetModuleHandle(TEXT("ntdll")), "RtlGetVersion");
+    RtlGetVersion(&info);
+    // Clear fields which would not be filled in by registry query
+    info.dwPlatformId = 0;
+    info.szCSDVersion[0] = L'\0';
+  }
+  return info;
+}
+};  // namespace WindowsRegistry