Get-HyperVVMGenerationNumberFromWithinVM.ps1

#region License
###############################################################################################
# Copyright 2020 Frank Lesniak

# Permission is hereby granted, free of charge, to any person obtaining a copy of this software
# and associated documentation files (the "Software"), to deal in the Software without
# restriction, including without limitation the rights to use, copy, modify, merge, publish,
# distribute, sublicense, and/or sell copies of the Software, and to permit persons to whom the
# Software is furnished to do so, subject to the following conditions:

# The above copyright notice and this permission notice shall be included in all copies or
# substantial portions of the Software.

# THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED, INCLUDING
# BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
# NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM,
# DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
# OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
###############################################################################################
#endregion License

function Split-StringOnLiteralString {
    # This function takes two positional arguments
    # The first argument is a string, and the string to be split
    # The second argument is a string or char, and it is that which is to split the string in the first parameter
    #
    # Note: This function always returns an array, even when there is zero or one element in it.
    #
    # Example:
    # $result = Split-StringOnLiteralString "foo" " "
    # # $result.GetType().FullName is System.Object[]
    # # $result.Count is 1
    #
    # Example 2:
    # $result = Split-StringOnLiteralString "What do you think of this function?" " "
    # # $result.Count is 7

    trap {
        Write-Error "An error occurred using the Split-StringOnLiteralString function. This was most likely caused by the arguments supplied not being strings"
    }

    if ($args.Length -ne 2) {
        Write-Error "Split-StringOnLiteralString was called without supplying two arguments. The first argument should be the string to be split, and the second should be the string or character on which to split the string."
    } else {
        if ($null -eq $args[0]) {
            # String to be split was $null; return an empty array. Leading comma ensures that
            # PowerShell cooperates and returns the array as desired (without collapsing it)
            , @()
        } elseif ($null -eq $args[1]) {
            # Splitter was $null; return string to be split within an array (of one element).
            # Leading comma ensures that PowerShell cooperates and returns the array as desired
            # (without collapsing it
            , ($args[0])
        } else {
            if (($args[0]).GetType().Name -ne "String") {
                Write-Warning "The first argument supplied to Split-StringOnLiteralString was not a string. It will be attempted to be converted to a string. To avoid this warning, cast arguments to a string before calling Split-StringOnLiteralString."
                $strToSplit = [string]$args[0]
            } else {
                $strToSplit = $args[0]
            }

            if ((($args[1]).GetType().Name -ne "String") -and (($args[1]).GetType().Name -ne "Char")) {
                Write-Warning "The second argument supplied to Split-StringOnLiteralString was not a string. It will be attempted to be converted to a string. To avoid this warning, cast arguments to a string before calling Split-StringOnLiteralString."
                $strSplitter = [string]$args[1]
            } elseif (($args[1]).GetType().Name -eq "Char") {
                $strSplitter = [string]$args[1]
            } else {
                $strSplitter = $args[1]
            }

            $strSplitterInRegEx = [regex]::Escape($strSplitter)

            # With the leading comma, force encapsulation into an array so that an array is
            # returned even when there is one element:
            , [regex]::Split($strToSplit, $strSplitterInRegEx)
        }
    }
}

function Get-PathToDotNetRuntimeEnvironment {
    $strPathToDotNetRuntimeEnvironment = [Runtime.InteropServices.RuntimeEnvironment]::GetRuntimeDirectory()
    # We have the path, but it has a trailing backslash. Let's remove it
    $guid = [guid]::NewGuid()
    $strGUID = $guid.Guid
    $strWorkingPath = Join-Path $strPathToDotNetRuntimeEnvironment $strGUID
    $arrPath = Split-StringOnLiteralString $strWorkingPath $strGUID
    $strPathWithSeparatorButWithoutGUID = $arrPath[0]
    $strScrubbedPath = $strPathWithSeparatorButWithoutGUID.Substring(0, $strPathWithSeparatorButWithoutGUID.Length - 1)
    $strScrubbedPath
}

function Build-CSharpInMemory {
    Param (
        [string]$strCSharpCodeToCompile,
        [array]$arrAdditionalReferences
    )

    $CSharpCodeProvider = New-Object Microsoft.CSharp.CSharpCodeProvider

    $ArrayListReferences = New-Object Collections.ArrayList
    $ArrayListReferences.AddRange( `
        @( `
            (Join-Path (Get-PathToDotNetRuntimeEnvironment) "System.dll"),
            [PSObject].Assembly.Location
        )
    )
    if ($arrAdditionalReferences -ne $null)	{
        if ($arrAdditionalReferences.Count -ge 1) {
            $ArrayListReferences.AddRange($arrAdditionalReferences)
        }
    }

    $CompilerParameters = New-Object System.CodeDom.Compiler.CompilerParameters
    $CompilerParameters.GenerateInMemory = $true
    $CompilerParameters.GenerateExecutable = $false
    $CompilerParameters.OutputAssembly = "custom"
    $CompilerParameters.ReferencedAssemblies.AddRange($ArrayListReferences)
    $CompilerResults = $CSharpCodeProvider.CompileAssemblyFromSource($CompilerParameters, $strCSharpCodeToCompile)

    if ($CompilerResults.Errors.Count) {
        $arrCSharpCodeLines = $strCSharpCodeToCompile.Split("`n")
        foreach ($CompilerError in $CompilerResults.Errors) {
            Write-Host "Error: $($arrCSharpCodeLines[$($CompilerError.Line - 1)])"
            $CompilerError | Out-Default
        }
        Throw "INVALID DATA: Errors encountered while compiling code"
    }
}

function Get-PSVersion {
    if (Test-Path variable:\PSVersionTable) {
        $PSVersionTable.PSVersion
    } else {
        [version]("1.0")
    }
}

function Test-Windows {
    $versionPS = Get-PSVersion
    if ($versionPS.Major -ge 6) {
        $IsWindows
    } else {
        $true
    }
}

function Get-WindowsOSVersion {
    $boolWindows = Test-Windows
    if ($boolWindows) {
        $versionPS = Get-PSVersion
        if ($versionPS.Major -ge 3) {
            $arrCIMInstanceOS = @(Get-CimInstance -Query "Select Version from Win32_OperatingSystem")
            if ($arrCIMInstanceOS.Count -eq 0) {
                Write-Error "No instances of Win32_OperatingSystem found!"
                $null
            }
            if ($arrCIMInstanceOS.Count -gt 1) {
                Write-Warning "More than one instance of Win32_OperatingSystem returned. Will only use first instance."
            }
            if ($arrCIMInstanceOS.Count -ge 1) {
                [System.Version](($arrCIMInstanceOS[0]).Version)
            }
        } else {
            $arrManagementObjectOS = @(Get-WmiObject -Query "Select Version from Win32_OperatingSystem")
            if ($arrManagementObjectOS.Count -eq 0) {
                Write-Error "No instances of Win32_OperatingSystem found!"
                $null
            }
            if ($arrManagementObjectOS.Count -gt 1) {
                Write-Warning "More than one instance of Win32_OperatingSystem returned. Will only use first instance."
            }
            if ($arrManagementObjectOS.Count -ge 1) {
                [System.Version](($arrManagementObjectOS[0]).Version)
            }
        }
    } else {
        $null
    }
}

function Get-PathToWindowsFolder {
    $boolWindows = Test-Windows
    if ($boolWindows) {
        $env:windir
    } else {
        $null
    }
}

function Get-PathToWindowsSetupLog {
    $strWindowsPath = Get-PathToWindowsFolder
    if ($null -ne $strWindowsPath) {
        $strWorkingPath = Join-Path $strWindowsPath "Panther"
        $strWorkingPath = Join-Path $strWorkingPath "setupact.log"
        $strWorkingPath
    } else {
        $null
    }
}

function Get-DetectedBootEnvironmentFromWindowsSetupLog {
    # Returns a string containing the "detected boot environment" from the Windows Setup log.
    # If the log could not be read, or if this function is run on non-Windows, the function
    # returns $null
    #
    #region OriginalLicense
    # Although substantial modifications have been made, the original portions of
    # Get-LogFileFirmwareType that are incorporated into
    # Get-DetectedBootEnvironmentFromWindowsSetupLog are subject to the following license:
    ###########################################################################################
    # Copyright (c) 2015 Chris Warwick
    #
    # Permission is hereby granted, free of charge, to any person obtaining a copy of this
    # software and associated documentation files (the "Software"), to deal in the Software
    # without restriction, including without limitation the rights to use, copy, modify, merge,
    # publish, distribute, sublicense, and/or sell copies of the Software, and to permit
    # persons to whom the Software is furnished to do so, subject to the following conditions:
    #
    # The above copyright notice and this permission notice shall be included in all copies or
    # substantial portions of the Software.
    #
    # THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED,
    # INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR
    # PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE
    # FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR
    # OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER
    # DEALINGS IN THE SOFTWARE.
    ###########################################################################################
    #endregion OriginalLicense

    $versionPS = Get-PSVersion
    $strPathToWindowsSetupLog = Get-PathToWindowsSetupLog
    if ($null -ne $strPathToWindowsSetupLog) {
        if ($versionPS.Major -ge 3) {
            $arrMatchInfo = @(Select-String 'Detected boot environment' $strPathToWindowsSetupLog -AllMatches -ErrorAction Ignore)
        } else {
            $arrMatchInfo = @(Select-String 'Detected boot environment' $strPathToWindowsSetupLog -AllMatches -ErrorAction SilentlyContinue)
        }
        if ($arrMatchInfo.Count -ge 1) {
            $arrStrBootEnvironments = @($arrMatchInfo | ForEach-Object {
                    ($_.Line) -replace ".*:\s+"
                })

            if ($arrStrBootEnvironments.Count -gt 1) {
                Write-Warning ("More than one detected boot environment found in Windows Setup Log (" + $strPathToWindowsSetupLog + "). Returning only first one.")
            }

            $arrStrBootEnvironments[0]
        } else {
            Write-Warning ("Read access to file " + $strPathToWindowsSetupLog + " was denied; try running PowerShell as an administrator (elevated)")
            $null
        }
    } else {
        $null
    }
}

function Test-FirmwareEnvironmentVariableAWin32API {
    # Returns $true if the GetFirmwareEnvironmentVariableA Win32 API is able to be called,
    # which indicates that the system is UEFI. Returns $false otherwise.
    #
    # NOTE: Returns $null if run on non-Windows system
    #
    #region OriginalLicense
    # Although substantial modifications have been made, the original portions of
    # Get-FirmwareEnvironmentVariableAPI that are incorporated into
    # Test-FirmwareEnvironmentVariableAWin32API are subject to the following license:
    ###########################################################################################
    # Copyright (c) 2015 Chris Warwick
    #
    # Permission is hereby granted, free of charge, to any person obtaining a copy of this
    # software and associated documentation files (the "Software"), to deal in the Software
    # without restriction, including without limitation the rights to use, copy, modify, merge,
    # publish, distribute, sublicense, and/or sell copies of the Software, and to permit
    # persons to whom the Software is furnished to do so, subject to the following conditions:
    #
    # The above copyright notice and this permission notice shall be included in all copies or
    # substantial portions of the Software.
    #
    # THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED,
    # INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR
    # PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE
    # FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR
    # OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER
    # DEALINGS IN THE SOFTWARE.
    ###########################################################################################
    #endregion OriginalLicense

    # Use the GetFirmwareEnvironmentVariable Win32 API.
    # From MSDN
    # (http://msdn.microsoft.com/en-ca/library/windows/desktop/ms724325%28v=vs.85%29.aspx):
    # "Firmware variables are not supported on a legacy BIOS-based system. The
    # GetFirmwareEnvironmentVariable function will always fail on a legacy BIOS-based system,
    # or if Windows was installed using legacy BIOS on a system that supports both legacy BIOS
    # and UEFI."
    # "To identify these conditions, call the function with a dummy firmware environment name
    # such as an empty string ("") for the lpName parameter and a dummy GUID such as
    # "{00000000-0000-0000-0000-000000000000}" for the lpGuid parameter. On a legacy BIOS-based
    # system, or on a system that supports both legacy BIOS and UEFI where Windows was
    # installed using legacy BIOS, the function will fail with ERROR_INVALID_FUNCTION. On a
    # UEFI-based system, the function will fail with an error specific to the firmware, such as
    # ERROR_NOACCESS, to indicate that the dummy GUID namespace does not exist."
    #
    # From PowerShell, we can call the API via P/Invoke from a compiled C# class using
    # Add-Type.  In Win32 any resulting API error is retrieved using GetLastError(), however,
    # this is not reliable in .Net (see
    # blogs.msdn.com/b/adam_nathan/archive/2003/04/25/56643.aspx), instead we mark the pInvoke
    # signature for GetFirmwareEnvironmentVariableA with SetLastError=true and use
    # Marshal.GetLastWin32Error()
    #
    # Note: The GetFirmwareEnvironmentVariable API requires the SE_SYSTEM_ENVIRONMENT_NAME
    # privilege.  In the Security Policy editor this equates to "User Rights Assignment":
    # "Modify firmware environment values" and is granted to Administrators by default. Because
    # we don't actually read any variables this permission appears to be optional.

    $boolWindows = Test-Windows

    if ($boolWindows) {
        $versionWindows = Get-WindowsOSVersion
        if ($versionWindows -ge ([System.Version]"6.1")) {
            $strCSharpCode = @"
using System;
using System.Runtime.InteropServices;
namespace FrankLesniak
{
    public class CheckUEFI
    {
        [DllImport("kernel32.dll", SetLastError=true)]
        static extern UInt32 
        GetFirmwareEnvironmentVariableA(string lpName, string lpGuid, IntPtr pBuffer, UInt32 nSize);
        const int ERROR_INVALID_FUNCTION = 1; 
        public static bool IsUEFI()
        {
            // Try to call the GetFirmwareEnvironmentVariable API.  This is invalid on legacy BIOS.
            GetFirmwareEnvironmentVariableA("","{00000000-0000-0000-0000-000000000000}",IntPtr.Zero,0);
            if (Marshal.GetLastWin32Error() == ERROR_INVALID_FUNCTION)
                return false;     // API not supported (INVALID_FUNCTION); this is a legacy BIOS
            else
                return true;      // Call to API is supported.  This is UEFI.
        }
    }
}
"@
            $versionPS = Get-PSVersion
            if ($versionPS.Major -ge 2) {
                Add-Type -Language CSharp -TypeDefinition $strCSharpCode
            } else {
                Build-CSharpInMemory $strCSharpCode
            }

            [FrankLesniak.CheckUEFI]::IsUEFI()
        } else {
            # Is Windows, but is a version that does not support
            # GetFirmwareEnvironmentVariableA API
            $null
        }
    } else {
        # Not Windows
        $null
    }
}

function Get-FirmwareTypeFromGetFirmwareTypeWin32API {
    # Returns an integer that indicates the firmware type on the system.
    # Returns:
    #   0 if the type is unknown
    #   1 if the type is BIOS
    #   2 if the type is UEFI
    #   3 if the type is "Max"
    #
    # NOTE: Returns $null if run on non-Windows system
    #
    #region OriginalLicense
    # Although substantial modifications have been made, the original portions of
    # Get-FirmwareTypeAPI that are incorporated into
    # Get-FirmwareTypeFromGetFirmwareTypeWin32API are subject to the following license:
    ###########################################################################################
    # Copyright (c) 2015 Chris Warwick
    #
    # Permission is hereby granted, free of charge, to any person obtaining a copy of this
    # software and associated documentation files (the "Software"), to deal in the Software
    # without restriction, including without limitation the rights to use, copy, modify, merge,
    # publish, distribute, sublicense, and/or sell copies of the Software, and to permit
    # persons to whom the Software is furnished to do so, subject to the following conditions:
    #
    # The above copyright notice and this permission notice shall be included in all copies or
    # substantial portions of the Software.
    #
    # THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED,
    # INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR
    # PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE
    # FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR
    # OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER
    # DEALINGS IN THE SOFTWARE.
    ###########################################################################################
    #endregion OriginalLicense
    #
    # In Windows 8/Server 2012 and above there's an API that directly returns the firmware type
    # and doesn't rely on a hack. GetFirmwareType() in kernel32.dll
    # (http://msdn.microsoft.com/en-us/windows/desktop/hh848321%28v=vs.85%29.aspx) returns a
    # pointer to a FirmwareType enum that defines the following:
    #
    # typedef enum _FIRMWARE_TYPE {
    #   FirmwareTypeUnknown = 0,
    #   FirmwareTypeBios = 1,
    #   FirmwareTypeUefi = 2,
    #   FirmwareTypeMax = 3
    # } FIRMWARE_TYPE, *PFIRMWARE_TYPE;
    # This API call can be called in .Net via P/Invoke.

    $boolWindows = Test-Windows

    if ($boolWindows) {
        $versionWindows = Get-WindowsOSVersion
        if ($versionWindows -ge ([System.Version]"6.2")) {
            $strCSharpCode = @"
using System;
using System.Runtime.InteropServices;
namespace FrankLesniak
{
    public class FirmwareType
    {
        [DllImport("kernel32.dll")]
        static extern bool GetFirmwareType(ref uint FirmwareType);
        public static uint GetFirmwareType()
        {
            uint firmwaretype = 0;
            if (GetFirmwareType(ref firmwaretype))
                return firmwaretype;
            else
                return 0;   // API call failed, just return 'unknown'
        }
    }
}
"@
            $versionPS = Get-PSVersion
            if ($versionPS.Major -ge 2) {
                Add-Type -Language CSharp -TypeDefinition $strCSharpCode
            } else {
                Build-CSharpInMemory $strCSharpCode
            }

            [FrankLesniak.FirmwareType]::GetFirmwareType()
        } else {
            # Is Windows, but is a version that does not support
            # GetFirmwareEnvironmentVariableA API
            $null
        }
    } else {
        # Not Windows
        $null
    }
}

function Test-UEFISystem {
    # Returns $true if the system is UEFI
    # Returns $false if the system is not UEFI (i.e., it is BIOS)
    # Returns $null if the system type could not be determined
    #
    #region OriginalLicense
    # Although substantial modifications have been made, the original portions of
    # Get-FirmwareType that are incorporated into Test-UEFISystem are subject to the following
    # license:
    ###########################################################################################
    # Copyright (c) 2015 Chris Warwick
    #
    # Permission is hereby granted, free of charge, to any person obtaining a copy of this
    # software and associated documentation files (the "Software"), to deal in the Software
    # without restriction, including without limitation the rights to use, copy, modify, merge,
    # publish, distribute, sublicense, and/or sell copies of the Software, and to permit
    # persons to whom the Software is furnished to do so, subject to the following conditions:
    #
    # The above copyright notice and this permission notice shall be included in all copies or
    # substantial portions of the Software.
    #
    # THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED,
    # INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR
    # PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE
    # FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR
    # OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER
    # DEALINGS IN THE SOFTWARE.
    ###########################################################################################
    #endregion OriginalLicense
    $boolWindows = Test-Windows
    if ($boolWindows) {
        $versionWindowsOS = Get-WindowsOSVersion
        if ($versionWindowsOS -lt ([System.Version]"6.0")) {
            # Windows 5.x running PowerShell - these do not support UEFI
            $false
        } elseif ($versionWindowsOS -ge ([System.Version]"6.2")) {
            # Windows 8 / Windows Server 2012, or newer
            $intFirmwareType = Get-FirmwareTypeFromGetFirmwareTypeWin32API
            if ($null -ne $intFirmwareType) {
                if ($intFirmwareType -eq 2) {
                    $true # UEFI
                } else {
                    $false # Not UEFI, must be BIOS
                }
            } else {
                # Error condition
                $null
            }
        } elseif ($versionWindowsOS -ge ([System.Version]"6.1")) {
            # Windows 7 / Windows Server 2008 R2
            Test-FirmwareEnvironmentVariableAWin32API
        } else {
            $strDetectedBootEnvironment = Get-DetectedBootEnvironmentFromWindowsSetupLog
            switch -Regex ($strDetectedBootEnvironment) {
                "^U?EFI$" {
                    $true
                }
                default {
                    $false
                }
            }
        }
    } else {
        # TO-DO: write code for FreeBSD/Linux
        # return $null for now
        $null
    }
}

function Get-HardwareModel {
    $boolWindows = Test-Windows
    if ($boolWindows) {
        $versionPS = Get-PSVersion
        if ($versionPS.Major -ge 3) {
            $arrCIMInstanceComputerSystem = @(Get-CimInstance -Query "Select Model from Win32_ComputerSystem")
            if ($arrCIMInstanceComputerSystem.Count -eq 0) {
                Write-Error "No instances of Win32_ComputerSystem found!"
                $null
            }
            if ($arrCIMInstanceComputerSystem.Count -gt 1) {
                Write-Warning "More than one instance of Win32_ComputerSystem returned. Will only use first instance."
            }
            if ($arrCIMInstanceComputerSystem.Count -ge 1) {
                ($arrCIMInstanceComputerSystem[0]).Model
            }
        } else {
            $arrManagementObjectComputerSystem = @(Get-WmiObject -Query "Select Model from Win32_ComputerSystem")
            if ($arrManagementObjectComputerSystem.Count -eq 0) {
                Write-Error "No instances of Win32_ComputerSystem found!"
                $null
            }
            if ($arrManagementObjectComputerSystem.Count -gt 1) {
                Write-Warning "More than one instance of Win32_ComputerSystem returned. Will only use first instance."
            }
            if ($arrManagementObjectComputerSystem.Count -ge 1) {
                ($arrManagementObjectComputerSystem[0]).Model
            }
        }
    } else {
        # TO-DO: Find a way to do this on FreeBSD/Linux
        # Return $null for now
        $null
    }
}

function Test-ThisSystemIsAHyperVVM {
    $boolWindows = Test-Windows
    if ($boolWindows) {
        $strModel = Get-HardwareModel
        if ($null -ne $strModel) {
            if ($strModel -eq "Virtual Machine") {
                $true
            } else {
                $false
            }
        } else {
            $null # Error condition
        }
    } else {
        # TO-DO: Find a way to do this on FreeBSD/Linux
        # Return $null for now
        $null
    }
}

function Get-HyperVVMGenerationNumberFromWithinVM {
    # Returns an integer indicating the Hyper-V VM generation number of this system
    # Returns 2 if this system is a Hyper-V VM running as a "Generation 2" Hyper-V VM
    # Returns 1 if this system is a Hyper-V VM running as a "Generation 1" Hyper-V VM
    #   Note: Microsoft Virtual Server and Virtual PC VMs can also return 1
    # Returns 0 if this system is a Hyper-V VM, but the generation number could not be
    #   determined due to an error. Usually this would only occur if the VM is Vista/Windows
    #   Server 2008 system and the PowerShell script was run without administrative privileges.
    #   Check the Warning stream for more information.
    #   Note: Microsoft Virtual Server and Virtual PC VMs can also return 0
    # Returns -1 if this system is not a Hyper-V VM
    $boolHyperVVM = Test-ThisSystemIsAHyperVVM
    if ($null -ne $boolHyperVVM) {
        if ($boolHyperVVM) {
            $boolUEFI = Test-UEFISystem
            if ($null -ne $boolUEFI) {
                if ($boolUEFI) {
                    # Hyper-V VM with UEFI
                    # Generation 2
                    2
                } else {
                    # Hyper-V VM not running UEFI
                    # Generation 1
                    1
                }
            } else {
                # Is a Hyper-V VM but could not determine whether UEFI is running
                # Error condition
                0
            }
        } else {
            # Not a Hyper-V VM
            -1
        }
    } else {
        $null
    }
}