How to convert Intel Assembly C to AT&T C++

Question

I trying to convert function "__cpuid" from С language to C++. I have a problem that the g++ compiler does not work with Intel assembler.

I'm trying to translate this code:

__asm
    {
        mov    esi, CPUInfo
        mov    eax, InfoType
        xor ecx, ecx
        cpuid
        mov    dword ptr[esi + 0], eax
        mov    dword ptr[esi + 4], ebx
        mov    dword ptr[esi + 8], ecx
        mov    dword ptr[esi + 12], edx
    }

I tried to do it using examples from the Internet, I got this code, but it doesn't work:

__asm
    (


            "movl   %CPUInfo,%esi\n"
            "movl   %InfoType,%eax\n"
            "xorl   %ecx,%ecx\n"
            "cpuid\n"
            "movl   %eax,0(%esi)\n"
            "movl   %ebx,4(%esi))\n"
            "movl   %ecx,8(%esi)\n"
            "movl   %edx,12(%esi)\n"
             :"=r"(CPUInfo)
 

    );

Answer 1

void cpuid(int InfoType, int *CPUInfo) {
  int a = InfoType;
  int c = 0;
  int b, d;
  __asm__ (
    "cpuid"
    : "+a"(a), "=b"(b), "+c"(c), "=d"(d)
  );
  CPUInfo[0] = a;
  CPUInfo[1] = b;
  CPUInfo[2] = c;
  CPUInfo[3] = d;
}

a , b , c , and d each binds to eax , ebx , ecx , and edx register. The GCC docs explains how this works in detail.

Answer 2

On linux (and in many other platforms, non-linux, non-gcc), you can assemble the intel assembly code into an object file with assembler such as nasm . Then you can link your assembly object into the application without need of mixing messages or assembly language syntax.