CPUID Java 21 :p

info.md

You need --enable-preview to compile/run this file.

Main.java

/*
    Demonstrates usage of CPUID on Windows in a single Java file, and prints the processor vendor string.
    Uses Java 21 language features.
 */

import java.lang.foreign.*;
import java.lang.invoke.MethodHandle;
import java.nio.ByteBuffer;
import java.nio.ByteOrder;

void main() throws Throwable {
    System.loadLibrary("kernel32");
    MethodHandle virtualAlloc = Linker.nativeLinker().downcallHandle(
        SymbolLookup.loaderLookup().find("VirtualAlloc").get(),
        FunctionDescriptor.of(
            ValueLayout.ADDRESS,
            ValueLayout.ADDRESS,
            ValueLayout.JAVA_INT,
            ValueLayout.JAVA_INT,
            ValueLayout.JAVA_INT
        )
    ); // VirtualAlloc of Kernel32.dll
    MethodHandle virtualFree = Linker.nativeLinker().downcallHandle(
        SymbolLookup.loaderLookup().find("VirtualFree").get(),
        FunctionDescriptor.of(
            ValueLayout.JAVA_BOOLEAN,
            ValueLayout.ADDRESS,
            ValueLayout.JAVA_INT,
            ValueLayout.JAVA_INT
        )
    ); // VirtualFree of Kernel32.dll


    ByteBuffer text = ByteBuffer.allocate(12);
    // 00,00,00,00
    byte[] base = new byte[]{
        (byte) 0xB8, (byte) 0x00, (byte) 0x00, (byte) 0x00, (byte) 0x00, // mov eax, 0
        (byte) 0x0F, (byte) 0xA2, // cpuid
        (byte) 0x89, (byte) 0x00, // mov ?, ?
        (byte) 0xC3 // ret
    };

    byte[] its = new byte[]{(byte) 0xD8, (byte) 0xD0, (byte) 0xC8}; // ebx, edx, ecx
    var alloc = ((MemorySegment) virtualAlloc.invoke(
        MemorySegment.NULL,
        base.length,
        0x00001000 /* commit */ | 0x00002000 /* reserve */,
        0x40 /* exec + read + write */
    )).reinterpret(base.length); // allocate an rwx page that contains our code

    for (int i = 0; i < base.length; i++)
        alloc.set(ValueLayout.JAVA_BYTE, i, base[i]); // copy the initial code
    var cpuid = Linker.nativeLinker().downcallHandle(alloc, FunctionDescriptor.of(ValueLayout.JAVA_INT)); // prepare the downcall

    text.order(ByteOrder.LITTLE_ENDIAN); // :p

    for (int i = 0; i < its.length; i++) {
        alloc.set(ValueLayout.JAVA_BYTE, 8, its[i]); // modify the codes returned registers in order
        int ret = (int) cpuid.invoke();
        text.putInt(ret);
    }

    String output = new String(text.array()); // ta daa
    System.out.println(output); // yep

    if ((boolean) virtualFree.invoke(alloc, base.length, 0x4000 /* decommit */))
        System.err.println("VirtualFree failed.");
}

i read this again and i puked