x86/x64 CPUID en C#

inline-assembly

Question

En relación con mi otra pregunta , ayúdame a depurar "Se produjo una excepción no controlada del tipo ''System.AccessViolationException'' en el Módulo desconocido. Información adicional: Intentó leer o escribir en la memoria protegida. Esto a menudo indica que otra memoria está dañada". Al recorrer el código, todo funciona hasta la llamada real a del () y falla en esa línea.

Este código se basa en la muestra de este artículo y este código python que funciona en python. No puedo obtener el ejemplo del código como está para funcionar tampoco (la misma excepción), pero tengo la esperanza de que esté un poco desactualizado o algo así.

EDITAR: vea el historial de edición si le importa cómo llegamos aquí, que no es interesante.

Versión de trabajo finalizada:

public static class CpuID
{
    public static byte[] Invoke(int level)
    {
        IntPtr codePointer = IntPtr.Zero;
        try
        {
            // compile
            byte[] codeBytes;
            if (IntPtr.Size == 4)
            {
                codeBytes = x86CodeBytes;
            }
            else
            {
                codeBytes = x64CodeBytes;
            }

            codePointer = VirtualAlloc(
                IntPtr.Zero,
                new UIntPtr((uint)codeBytes.Length),
                AllocationType.COMMIT | AllocationType.RESERVE,
                MemoryProtection.EXECUTE_READWRITE
            );

            Marshal.Copy(codeBytes, 0, codePointer, codeBytes.Length);

            CpuIDDelegate cpuIdDelg = (CpuIDDelegate)Marshal.GetDelegateForFunctionPointer(codePointer, typeof(CpuIDDelegate));

            // invoke
            GCHandle handle = default(GCHandle);
            var buffer = new byte[16];

            try
            {
                handle = GCHandle.Alloc(buffer, GCHandleType.Pinned);
                cpuIdDelg(level, buffer);
            }
            finally
            {
                if (handle != default(GCHandle))
                {
                    handle.Free();
                }
            }

            return buffer;
        }
        finally
        {
            if (codePointer != IntPtr.Zero)
            {
                VirtualFree(codePointer, 0, 0x8000);
                codePointer = IntPtr.Zero;
            }
        }
    }

    [UnmanagedFunctionPointerAttribute(CallingConvention.Cdecl)]
    private delegate void CpuIDDelegate(int level, byte[] buffer);

    [DllImport("kernel32.dll", SetLastError = true)]
    private static extern IntPtr VirtualAlloc(IntPtr lpAddress, UIntPtr dwSize, AllocationType flAllocationType,
        MemoryProtection flProtect);

    [DllImport("kernel32")]
    private static extern bool VirtualFree(IntPtr lpAddress, UInt32 dwSize, UInt32 dwFreeType);

    [Flags()]
    private enum AllocationType : uint
    {
        COMMIT = 0x1000,
        RESERVE = 0x2000,
        RESET = 0x80000,
        LARGE_PAGES = 0x20000000,
        PHYSICAL = 0x400000,
        TOP_DOWN = 0x100000,
        WRITE_WATCH = 0x200000
    }

    [Flags()]
    private enum MemoryProtection : uint
    {
        EXECUTE = 0x10,
        EXECUTE_READ = 0x20,
        EXECUTE_READWRITE = 0x40,
        EXECUTE_WRITECOPY = 0x80,
        NOACCESS = 0x01,
        READONLY = 0x02,
        READWRITE = 0x04,
        WRITECOPY = 0x08,
        GUARD_Modifierflag = 0x100,
        NOCACHE_Modifierflag = 0x200,
        WRITECOMBINE_Modifierflag = 0x400
    }

    // Basic ASM strategy --
    // void x86CpuId(int level, byte* buffer) 
    // {
    //    eax = level
    //    cpuid
    //    buffer[0] = eax
    //    buffer[4] = ebx
    //    buffer[8] = ecx
    //    buffer[12] = edx
    // }

    private readonly static byte[] x86CodeBytes = {
        0x55,                   // push        ebp  
        0x8B, 0xEC,             // mov         ebp,esp
        0x53,                   // push        ebx  
        0x57,                   // push        edi

        0x8B, 0x45, 0x08,       // mov         eax, dword ptr [ebp+8] (move level into eax)
        0x0F, 0xA2,              // cpuid

        0x8B, 0x7D, 0x0C,       // mov         edi, dword ptr [ebp+12] (move address of buffer into edi)
        0x89, 0x07,             // mov         dword ptr [edi+0], eax  (write eax, ... to buffer)
        0x89, 0x5F, 0x04,       // mov         dword ptr [edi+4], ebx 
        0x89, 0x4F, 0x08,       // mov         dword ptr [edi+8], ecx 
        0x89, 0x57, 0x0C,       // mov         dword ptr [edi+12],edx 

        0x5F,                   // pop         edi  
        0x5B,                   // pop         ebx  
        0x8B, 0xE5,             // mov         esp,ebp  
        0x5D,                   // pop         ebp 
        0xc3                    // ret
    };

    private readonly static byte[] x64CodeBytes = {
        0x53,                       // push rbx    this gets clobbered by cpuid

        // rcx is level
        // rdx is buffer.
        // Need to save buffer elsewhere, cpuid overwrites rdx
        // Put buffer in r8, use r8 to reference buffer later.

        // Save rdx (buffer addy) to r8
        0x49, 0x89, 0xd0,           // mov r8,  rdx

        // Move ecx (level) to eax to call cpuid, call cpuid
        0x89, 0xc8,                 // mov eax, ecx
        0x0F, 0xA2,                 // cpuid

        // Write eax et al to buffer
        0x41, 0x89, 0x40, 0x00,     // mov    dword ptr [r8+0],  eax
        0x41, 0x89, 0x58, 0x04,     // mov    dword ptr [r8+4],  ebx
        0x41, 0x89, 0x48, 0x08,     // mov    dword ptr [r8+8],  ecx
        0x41, 0x89, 0x50, 0x0c,     // mov    dword ptr [r8+12], edx

        0x5b,                       // pop rbx
        0xc3                        // ret
    };
}

Tenga en cuenta que CPUID0 debe leerse en el orden correcto:

//a twelve character ASCII string stored in EBX, EDX, ECX - in that order
var cpuid0s = new string(ASCIIEncoding.ASCII.GetChars(
    cpuid0.Skip(4).Take(4).Concat(
    cpuid0.Skip(12).Take(4)).Concat(
    cpuid0.Skip(8).Take(4)).ToArray()));

Answer 1

¿Puedo sugerir la siguiente página: http://devpinoy.org/blogs/cvega/archive/2006/04/07/2658.aspx

Esta página le mostrará el código fuente del ensamblado para CPUID, cómo compilarlo en una DLL y cómo llamarlo desde C #.

Además, si necesita otros procedimientos de identificación de hardware, le sugiero esta página: http://www.codeproject.com/KB/system/GetHardwareInformation.aspx

Esta página muestra cómo obtener información como información de la placa base, información del disco duro, información de la CPU, información de la tarjeta de video, etc., etc.

Answer 2

Además, para obtener CPUID4, se necesita un argumento más. Aquí es cómo obtienes CPUID0, CPUID1, CPUID2, CPUID4.

byte[] cpuid0 = Invoke(0, 0);
byte[] cpuid1 = Invoke(1, 0);
byte[] cpuid2 = Invoke(2, 0);

List<byte[]> cpuid4L = new List<byte[]>();
for (int i = 0; true; i++)
{
    byte[] cpuid4 = Invoke(4, (uint)i);
    if ( (cpuid4[0] & 0x0F) == 0)
        break;
    cpuid4L.Add(cpuid4);
}

private static byte[] Invoke(uint functionNum, uint ecx)
{
    IntPtr codePointer = IntPtr.Zero;

    try
    {
        // Select a code
        byte[] codeBytes;
        if (IntPtr.Size == 4)
            codeBytes = x86CodeBytes;
        else
            codeBytes = x64CodeBytes;

        codePointer = NativeMethods.VirtualAlloc(IntPtr.Zero, new UIntPtr((uint)codeBytes.Length), MEM_COMMIT | MEM_RESERVE, PAGE_EXECUTE_READWRITE);
        Marshal.Copy(codeBytes, 0, codePointer, codeBytes.Length);
        CpuIdDelegate cpuIdDelg = (CpuIdDelegate)Marshal.GetDelegateForFunctionPointer(codePointer, typeof(CpuIdDelegate));

        // Invoke the code
        GCHandle handle = default(GCHandle);
        var buffer = new byte[16];

        try
        {
            handle = GCHandle.Alloc(buffer, GCHandleType.Pinned);
            cpuIdDelg(ecx, functionNum, buffer);  // Run the assembly code.
        }
        finally
        {
            if (handle != default(GCHandle))
            {
                handle.Free();
            }
        }

        return buffer;
    }
    finally
    {
        if (codePointer != IntPtr.Zero)
        {
            NativeMethods.VirtualFree(codePointer, (UIntPtr) 0, MEM_RELEASE);
            codePointer = IntPtr.Zero;
        }
    }
}

private readonly static byte[] x86CodeBytes = {
    0x55,                   
    0x8B, 0xEC,             
    0x53,                   
    0x57,                   
    0x8B, 0x4D, 0x08,
    0x8B, 0x45, 0x0C,
    0x0F, 0xA2,      
    0x8B, 0x7D, 0x10,
    0x89, 0x07,      
    0x89, 0x5F, 0x04,
    0x89, 0x4F, 0x08,
    0x89, 0x57, 0x0C,
    0x5F,                   
    0x5B,                   
    0x8B, 0xE5,             
    0x5D,                   
    0xc3                    
};

private readonly static byte[] x64CodeBytes = {
    0x53,
    0x89, 0xD0,
    0x0F, 0xA2,
    0x41, 0x89, 0x40, 0x00,
    0x41, 0x89, 0x58, 0x04,
    0x41, 0x89, 0x48, 0x08,
    0x41, 0x89, 0x50, 0x0c,
    0x5b,
    0xc3
};

Answer 3

Decidí mejorar tu respuesta. Ya no es necesario compilar inseguro, y solo necesita dos bloques de ensamblaje para poder leer cualquiera y todos los bloques de cpuid, porque solo escribe eax / ebx / ecx / edx en una matriz de bytes de 16 bytes.

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Reflection;
using System.Runtime.InteropServices;

namespace CpuID
{
    public class CpuID : IDisposable
    {
        [UnmanagedFunctionPointerAttribute(CallingConvention.Cdecl)]
        public delegate void CpuIDDelegate(int level, byte[] buffer);

        [DllImport("kernel32.dll", SetLastError = true)]
        private static extern IntPtr VirtualAlloc(
            IntPtr lpAddress,
            UIntPtr dwSize,
            AllocationType flAllocationType, 
            MemoryProtection flProtect
        );

        [DllImport("kernel32")]
        private static extern bool VirtualFree(
                IntPtr lpAddress,
                UInt32 dwSize,
                UInt32 dwFreeType
        );

        [Flags()]
        public enum AllocationType : uint
        {
            COMMIT = 0x1000,
            RESERVE = 0x2000,
            RESET = 0x80000,
            LARGE_PAGES = 0x20000000,
            PHYSICAL = 0x400000,
            TOP_DOWN = 0x100000,
            WRITE_WATCH = 0x200000
        }

        [Flags()]
        public enum MemoryProtection : uint
        {
            EXECUTE = 0x10,
            EXECUTE_READ = 0x20,
            EXECUTE_READWRITE = 0x40,
            EXECUTE_WRITECOPY = 0x80,
            NOACCESS = 0x01,
            READONLY = 0x02,
            READWRITE = 0x04,
            WRITECOPY = 0x08,
            GUARD_Modifierflag = 0x100,
            NOCACHE_Modifierflag = 0x200,
            WRITECOMBINE_Modifierflag = 0x400
        }

        private CpuIDDelegate cpuIdDelg;

        private IntPtr codePointer;

        // void x86CpuId(int level, byte* buffer) 
        // {
        //    eax = level
        //    cpuid
        //    buffer[0] = eax
        //    buffer[4] = ebx
        //    buffer[8] = ecx
        //    buffer[12] = edx
        // }
        private byte[] x86CodeBytes = 
        {
            0x55,                   // push        ebp  
            0x8B, 0xEC,             // mov         ebp,esp
            0x53,                   // push        ebx  
            0x57,                   // push        edi

            0x8B, 0x45, 0x08,       // mov         eax, dword ptr [ebp+8] (move level into eax)
            0x0F, 0xA2,              // cpuid

            0x8B, 0x7D, 0x0C,       // mov         edi, dword ptr [ebp+12] (move address of buffer into edi)
            0x89, 0x07,             // mov         dword ptr [edi+0], eax  (write eax, ... to buffer)
            0x89, 0x5F, 0x04,       // mov         dword ptr [edi+4], ebx 
            0x89, 0x4F, 0x08,       // mov         dword ptr [edi+8], ecx 
            0x89, 0x57, 0x0C,       // mov         dword ptr [edi+12],edx 

            0x5F,                   // pop         edi  
            0x5B,                   // pop         ebx  
            0x8B, 0xE5,             // mov         esp,ebp  
            0x5D,                   // pop         ebp 
            0xc3                    // ret
        };

        private byte[] x64CodeBytes = 
        {
            0x53,                       // push rbx    this gets clobbered by cpuid

            // rcx is level
            // rdx is buffer.
            // Need to save buffer elsewhere, cpuid overwrites rdx
            // Put buffer in r8, use r8 to reference buffer later.

            // Save rdx (buffer addy) to r8
            0x49, 0x89, 0xd0,           // mov r8,  rdx

            // Move ecx (level) to eax to call cpuid, call cpuid
            0x89, 0xc8,                 // mov eax, ecx
            0x0F, 0xA2,                 // cpuid

            // Write eax et al to buffer
            0x41, 0x89, 0x40, 0x00,     // mov    dword ptr [r8+0],  eax
            0x41, 0x89, 0x58, 0x04,     // mov    dword ptr [r8+4],  ebx
            0x41, 0x89, 0x48, 0x08,     // mov    dword ptr [r8+8],  ecx
            0x41, 0x89, 0x50, 0x0c,     // mov    dword ptr [r8+12], edx

            0x5b,                       // pop rbx
            0xc3                        // ret
        };

        public CpuID()
        {
            Compile();
        }

        ~CpuID()
        {
            Dispose(false);
        }

        private void Compile()
        {
            byte[] codeBytes;

            if (IntPtr.Size == 4)
            {
                codeBytes = x86CodeBytes;
            }
            else
            {
                codeBytes = x64CodeBytes;
            }

            this.codePointer = VirtualAlloc(
                IntPtr.Zero,
                new UIntPtr((uint)codeBytes.Length),
                AllocationType.COMMIT | AllocationType.RESERVE,
                MemoryProtection.EXECUTE_READWRITE
            );

            Marshal.Copy(codeBytes, 0, this.codePointer, codeBytes.Length);

            this.cpuIdDelg = (CpuIDDelegate)Marshal.GetDelegateForFunctionPointer(this.codePointer, typeof(CpuIDDelegate));
        }

        public void Invoke(int level, byte[] buffer)
        {
            GCHandle handle = default(GCHandle);
            if (buffer.Length < 16)
            {
                throw new ArgumentException("buffer must be at least 16 bytes long");
            }

            try
            {
                handle = GCHandle.Alloc(buffer, GCHandleType.Pinned);

                this.cpuIdDelg(level, buffer);
            }
            finally
            {
                if (handle != default(GCHandle))
                {
                    handle.Free();
                }
            }
        }

        public void Dispose()
        {
            Dispose(true);
        }

        public void Dispose(bool disposing)
        {
            if (this.codePointer != IntPtr.Zero)
            {
                VirtualFree(this.codePointer, 0, 0x8000);
                this.codePointer = IntPtr.Zero;
            }
        }

    }
}

Answer 4

Estoy bastante seguro de que estás siendo bloqueado por DEP . Las x_CPUIDy_INSNS bytes x_CPUIDy_INSNS están en un segmento de memoria marcado como datos y no ejecutable.

EDITAR:

Dicho esto, obtuve una versión que compila y ejecuta, pero no creo que tenga los valores correctos. Tal vez esto te ayude a seguir tu camino.

EDICION 2:

Creo que tengo los valores correctos regresando ahora. Siéntase libre de validar.

namespace CPUID
{
    using System;
    using System.Globalization;
    using System.Linq;
    using System.Reflection;
    using System.Runtime.InteropServices;
    using System.Text;

    internal static class Program
    {
        [Flags]
        private enum AllocationTypes : uint
        {
            Commit = 0x1000,
            Reserve = 0x2000,
            Reset = 0x80000,
            LargePages = 0x20000000,
            Physical = 0x400000,
            TopDown = 0x100000,
            WriteWatch = 0x200000
        }

        [Flags]
        private enum MemoryProtections : uint
        {
            Execute = 0x10,
            ExecuteRead = 0x20,
            ExecuteReadWrite = 0x40,
            ExecuteWriteCopy = 0x80,
            NoAccess = 0x01,
            ReadOnly = 0x02,
            ReadWrite = 0x04,
            WriteCopy = 0x08,
            GuartModifierflag = 0x100,
            NoCacheModifierflag = 0x200,
            WriteCombineModifierflag = 0x400
        }

        [Flags]
        private enum FreeTypes : uint
        {
            Decommit = 0x4000,
            Release = 0x8000
        }

        [UnmanagedFunctionPointerAttribute(CallingConvention.Cdecl)]
        private unsafe delegate void CPUID0Delegate(byte* buffer);

        [UnmanagedFunctionPointerAttribute(CallingConvention.Cdecl)]
        private unsafe delegate void CPUID1Delegate(byte* buffer);

        private static void Main()
        {
            Console.WriteLine("CPUID0: {0}", string.Join(", ", CPUID0().Select(x => x.ToString("X2", CultureInfo.InvariantCulture))));
            Console.WriteLine("CPUID0: {0}", new string(ASCIIEncoding.ASCII.GetChars(CPUID0())));
            Console.WriteLine("CPUID1: {0}", string.Join(", ", CPUID1().Select(x => x.ToString("X2", CultureInfo.InvariantCulture))));
            Console.ReadLine();
        }

        private static unsafe byte[] CPUID0()
        {
            byte[] buffer = new byte[12];

            if (IntPtr.Size == 4)
            {
                IntPtr p = NativeMethods.VirtualAlloc(
                    IntPtr.Zero,
                    new UIntPtr((uint)x86_CPUID0_INSNS.Length),
                    AllocationTypes.Commit | AllocationTypes.Reserve,
                    MemoryProtections.ExecuteReadWrite);
                try
                {
                    Marshal.Copy(x86_CPUID0_INSNS, 0, p, x86_CPUID0_INSNS.Length);

                    CPUID0Delegate del = (CPUID0Delegate)Marshal.GetDelegateForFunctionPointer(p, typeof(CPUID0Delegate));

                    fixed (byte* newBuffer = &buffer[0])
                    {
                        del(newBuffer);
                    }
                }
                finally
                {
                    NativeMethods.VirtualFree(p, 0, FreeTypes.Release);
                }
            }
            else if (IntPtr.Size == 8)
            {
                IntPtr p = NativeMethods.VirtualAlloc(
                    IntPtr.Zero,
                    new UIntPtr((uint)x64_CPUID0_INSNS.Length),
                    AllocationTypes.Commit | AllocationTypes.Reserve,
                    MemoryProtections.ExecuteReadWrite);
                try
                {
                    Marshal.Copy(x64_CPUID0_INSNS, 0, p, x64_CPUID0_INSNS.Length);

                    CPUID0Delegate del = (CPUID0Delegate)Marshal.GetDelegateForFunctionPointer(p, typeof(CPUID0Delegate));

                    fixed (byte* newBuffer = &buffer[0])
                    {
                        del(newBuffer);
                    }
                }
                finally
                {
                    NativeMethods.VirtualFree(p, 0, FreeTypes.Release);
                }
            }

            return buffer;
        }

        private static unsafe byte[] CPUID1()
        {
            byte[] buffer = new byte[12];

            if (IntPtr.Size == 4)
            {
                IntPtr p = NativeMethods.VirtualAlloc(
                    IntPtr.Zero,
                    new UIntPtr((uint)x86_CPUID1_INSNS.Length),
                    AllocationTypes.Commit | AllocationTypes.Reserve,
                    MemoryProtections.ExecuteReadWrite);
                try
                {
                    Marshal.Copy(x86_CPUID1_INSNS, 0, p, x86_CPUID1_INSNS.Length);

                    CPUID1Delegate del = (CPUID1Delegate)Marshal.GetDelegateForFunctionPointer(p, typeof(CPUID1Delegate));

                    fixed (byte* newBuffer = &buffer[0])
                    {
                        del(newBuffer);
                    }
                }
                finally
                {
                    NativeMethods.VirtualFree(p, 0, FreeTypes.Release);
                }
            }
            else if (IntPtr.Size == 8)
            {
                IntPtr p = NativeMethods.VirtualAlloc(
                    IntPtr.Zero,
                    new UIntPtr((uint)x64_CPUID1_INSNS.Length),
                    AllocationTypes.Commit | AllocationTypes.Reserve,
                    MemoryProtections.ExecuteReadWrite);
                try
                {
                    Marshal.Copy(x64_CPUID1_INSNS, 0, p, x64_CPUID1_INSNS.Length);

                    CPUID1Delegate del = (CPUID1Delegate)Marshal.GetDelegateForFunctionPointer(p, typeof(CPUID1Delegate));

                    fixed (byte* newBuffer = &buffer[0])
                    {
                        del(newBuffer);
                    }
                }
                finally
                {
                    NativeMethods.VirtualFree(p, 0, FreeTypes.Release);
                }
            }

            return buffer;
        }

        private static class NativeMethods
        {
            [DllImport("kernel32.dll", SetLastError = true)]
            internal static extern IntPtr VirtualAlloc(
                IntPtr lpAddress,
                UIntPtr dwSize,
                AllocationTypes flAllocationType,
                MemoryProtections flProtect);

            [DllImport("kernel32")]
            [return: MarshalAs(UnmanagedType.Bool)]
            internal static extern bool VirtualFree(
                IntPtr lpAddress,
                uint dwSize,
                FreeTypes flFreeType);
        }

        #region ASM
        private static readonly byte[] x86_CPUID0_INSNS = new byte[]
            {
                0x53,                      // push   %ebx
                0x31, 0xc0,                // xor    %eax,%eax
                0x0f, 0xa2,                // cpuid
                0x8b, 0x44, 0x24, 0x08,    // mov    0x8(%esp),%eax
                0x89, 0x18,                // mov    %ebx,0x0(%eax)
                0x89, 0x50, 0x04,          // mov    %edx,0x4(%eax)
                0x89, 0x48, 0x08,          // mov    %ecx,0x8(%eax)
                0x5b,                      // pop    %ebx
                0xc3                       // ret
            };

        private static readonly byte[] x86_CPUID1_INSNS = new byte[]
            {
                0x53,                   // push   %ebx
                0x31, 0xc0,             // xor    %eax,%eax
                0x40,                   // inc    %eax
                0x0f, 0xa2,             // cpuid
                0x5b,                   // pop    %ebx
                0xc3                    // ret
            };

        private static readonly byte[] x64_CPUID0_INSNS = new byte[]
            {
                0x49, 0x89, 0xd8,       // mov    %rbx,%r8
                0x49, 0x89, 0xc9,       // mov    %rcx,%r9
                0x48, 0x31, 0xc0,       // xor    %rax,%rax
                0x0f, 0xa2,             // cpuid
                0x4c, 0x89, 0xc8,       // mov    %r9,%rax
                0x89, 0x18,             // mov    %ebx,0x0(%rax)
                0x89, 0x50, 0x04,       // mov    %edx,0x4(%rax)
                0x89, 0x48, 0x08,       // mov    %ecx,0x8(%rax)
                0x4c, 0x89, 0xc3,       // mov    %r8,%rbx
                0xc3                    // retq
            };

        private static readonly byte[] x64_CPUID1_INSNS = new byte[]
            {
                0x53,                     // push   %rbx
                0x48, 0x31, 0xc0,         // xor    %rax,%rax
                0x48, 0xff, 0xc0,         // inc    %rax
                0x0f, 0xa2,               // cpuid
                0x5b,                     // pop    %rbx
                0xc3                      // retq
            };
        #endregion
    }
}

Answer 5

Gracias a @antiduh por su solución. Cambiaría la firma Invoke un poco para una mejor usabilidad de la siguiente manera, por lo que no es necesario asignar un obtener el resultado como un conjunto de registros

    // This is a modification to https://.com/a/7964376/725903
    [UnmanagedFunctionPointerAttribute(CallingConvention.Cdecl)]
    private delegate void CpuIDDelegate(int level, IntPtr ptr);

    [StructLayout(LayoutKind.Sequential, Size = 16)]
    public struct CpuIdResult
    {
        public int Eax;
        public int Ebx;
        public int Ecx;
        public int Edx;
    }

    public CpuIdResult Invoke(int level)
    {
        CpuIdResult result;
        IntPtr buffer = Marshal.AllocHGlobal(16);
        try
        {
            this.cpuIdDelg(level, buffer);
            result = (CpuIdResult)Marshal.PtrToStructure(buffer, typeof(CpuIdResult));
        }
        finally
        {
            Marshal.FreeHGlobal(buffer);
        }
        return result;
    }

Answer 6

Tomé el código de @antiduh y lo refactoricé en un método estático, por lo que no hay que administrar el ciclo de vida del objeto. Esto es más lento porque el código ASM no se reutiliza entre las llamadas a Invoke (), pero el intercambio de velocidad por simplicidad tiene sentido para mi caso de uso. Esta nueva versión puede llamar a CPUID 1000 veces en 15 milisegundos en mi máquina.

Gracias por el maravilloso código chicos!

public static class CpuID {

    public static byte[] Invoke(int level) {
        IntPtr codePointer = IntPtr.Zero;
        try {
            // compile
            byte[] codeBytes;
            if (IntPtr.Size == 4) {
                codeBytes = x86CodeBytes;
            } else {
                codeBytes = x64CodeBytes;
            }

            codePointer = VirtualAlloc(
                IntPtr.Zero,
                new UIntPtr((uint)codeBytes.Length),
                AllocationType.COMMIT | AllocationType.RESERVE,
                MemoryProtection.EXECUTE_READWRITE
            );

            Marshal.Copy(codeBytes, 0, codePointer, codeBytes.Length);

            CpuIDDelegate cpuIdDelg = (CpuIDDelegate)Marshal.GetDelegateForFunctionPointer(codePointer, typeof(CpuIDDelegate));

            // invoke
            GCHandle handle = default(GCHandle);
            var buffer = new byte[16];

            try {
                handle = GCHandle.Alloc(buffer, GCHandleType.Pinned);
                cpuIdDelg(level, buffer);
            } finally {
                if (handle != default(GCHandle)) {
                    handle.Free();
                }
            }

            return buffer;
        } finally {
            if (codePointer != IntPtr.Zero) {
                VirtualFree(codePointer, 0, 0x8000);
                codePointer = IntPtr.Zero;
            }
        }
    }

    [UnmanagedFunctionPointerAttribute(CallingConvention.Cdecl)]
    private delegate void CpuIDDelegate(int level, byte[] buffer);

    [DllImport("kernel32.dll", SetLastError = true)]
    private static extern IntPtr VirtualAlloc(IntPtr lpAddress, UIntPtr dwSize, AllocationType flAllocationType,
        MemoryProtection flProtect);

    [DllImport("kernel32")]
    private static extern bool VirtualFree(IntPtr lpAddress, UInt32 dwSize, UInt32 dwFreeType);

    [Flags()]
    private enum AllocationType : uint {
        COMMIT = 0x1000,
        RESERVE = 0x2000,
        RESET = 0x80000,
        LARGE_PAGES = 0x20000000,
        PHYSICAL = 0x400000,
        TOP_DOWN = 0x100000,
        WRITE_WATCH = 0x200000
    }

    [Flags()]
    private enum MemoryProtection : uint {
        EXECUTE = 0x10,
        EXECUTE_READ = 0x20,
        EXECUTE_READWRITE = 0x40,
        EXECUTE_WRITECOPY = 0x80,
        NOACCESS = 0x01,
        READONLY = 0x02,
        READWRITE = 0x04,
        WRITECOPY = 0x08,
        GUARD_Modifierflag = 0x100,
        NOCACHE_Modifierflag = 0x200,
        WRITECOMBINE_Modifierflag = 0x400
    }

    // Basic ASM strategy --
    // void x86CpuId(int level, byte* buffer) 
    // {
    //    eax = level
    //    cpuid
    //    buffer[0] = eax
    //    buffer[4] = ebx
    //    buffer[8] = ecx
    //    buffer[12] = edx
    // }

    private readonly static byte[] x86CodeBytes = {
        0x55,                   // push        ebp  
        0x8B, 0xEC,             // mov         ebp,esp
        0x53,                   // push        ebx  
        0x57,                   // push        edi

        0x8B, 0x45, 0x08,       // mov         eax, dword ptr [ebp+8] (move level into eax)
        0x0F, 0xA2,              // cpuid

        0x8B, 0x7D, 0x0C,       // mov         edi, dword ptr [ebp+12] (move address of buffer into edi)
        0x89, 0x07,             // mov         dword ptr [edi+0], eax  (write eax, ... to buffer)
        0x89, 0x5F, 0x04,       // mov         dword ptr [edi+4], ebx 
        0x89, 0x4F, 0x08,       // mov         dword ptr [edi+8], ecx 
        0x89, 0x57, 0x0C,       // mov         dword ptr [edi+12],edx 

        0x5F,                   // pop         edi  
        0x5B,                   // pop         ebx  
        0x8B, 0xE5,             // mov         esp,ebp  
        0x5D,                   // pop         ebp 
        0xc3                    // ret
    };

    private readonly static byte[] x64CodeBytes = {
        0x53,                       // push rbx    this gets clobbered by cpuid

        // rcx is level
        // rdx is buffer.
        // Need to save buffer elsewhere, cpuid overwrites rdx
        // Put buffer in r8, use r8 to reference buffer later.

        // Save rdx (buffer addy) to r8
        0x49, 0x89, 0xd0,           // mov r8,  rdx

        // Move ecx (level) to eax to call cpuid, call cpuid
        0x89, 0xc8,                 // mov eax, ecx
        0x0F, 0xA2,                 // cpuid

        // Write eax et al to buffer
        0x41, 0x89, 0x40, 0x00,     // mov    dword ptr [r8+0],  eax
        0x41, 0x89, 0x58, 0x04,     // mov    dword ptr [r8+4],  ebx
        0x41, 0x89, 0x48, 0x08,     // mov    dword ptr [r8+8],  ecx
        0x41, 0x89, 0x50, 0x0c,     // mov    dword ptr [r8+12], edx

        0x5b,                       // pop rbx
        0xc3                        // ret
    };
}