#ifndef _NTPSAPI_H
#if (PHNT_MODE != PHNT_MODE_KERNEL)

typedef enum _SUBSYSTEM_INFORMATION_TYPE
{
    SubsystemInformationTypeWin32,
    SubsystemInformationTypeWSL,
    MaxSubsystemInformationType
} SUBSYSTEM_INFORMATION_TYPE;

#endif
#endif
View code on GitHub

// ntddk.h

typedef enum _SUBSYSTEM_INFORMATION_TYPE {
  SubsystemInformationTypeWin32,
  SubsystemInformationTypeWSL,
  MaxSubsystemInformationType
} SUBSYSTEM_INFORMATION_TYPE, *PSUBSYSTEM_INFORMATION_TYPE;
View the official Windows Driver Kit DDI reference

NtDoc

This enumeration is documented in Windows Driver Kit.

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Windows Driver Kit DDI reference (ne-ntddk-_subsystem_information_type)

_SUBSYSTEM_INFORMATION_TYPE enumeration

Description

Indicates the type of subsystem for a process or thread. This enumeration is used in NtQueryInformationProcess and NtQueryInformationThread calls.

Constants

`SubsystemInformationTypeWin32`

The subsystem type for the process or thread is Win32.

`SubsystemInformationTypeWSL`

The subsystem type for the process or thread is Windows Subsystem for Linux (WSL). For this process, these members of the PS_CREATE_NOTIFY_INFO structure are set as follows:

The FileObject member is the NTFS file object from LxFs or DriveFs, the file system that is used for interoperability with Windows.
The ImageFileName member is the Linux path of the image file.
The CommandLine member is the Linux NULL-separated command line.

The preceding member values may be NULL.

`MaxSubsystemInformationType`

Reserved.

SUBSYSTEM_INFORMATION_TYPE - NtDoc