Obtain the unique ID or serial number of the processor using C in Linux

There is a answer made by @AndreHolzner on site SO, where you specify:

This is what the Linux kernel seems to use:

static inline void native_cpuid(unsigned int *eax, unsigned int *ebx,
                                unsigned int *ecx, unsigned int *edx)
{
        /* ecx is often an input as well as an output. */
        asm volatile("cpuid"
            : "=a" (*eax),
              "=b" (*ebx),
              "=c" (*ecx),
              "=d" (*edx)
            : "0" (*eax), "2" (*ecx));
}

What one can use, for example:

#include <stdio.h>

int main(int argc, char **argv)
{
  unsigned eax, ebx, ecx, edx;

  eax = 1; /* processor info and feature bits */
  native_cpuid(&eax, &ebx, &ecx, &edx);

  printf("stepping %d\n", eax & 0xF);
  printf("model %d\n", (eax >> 4) & 0xF);
  printf("family %d\n", (eax >> 8) & 0xF);
  printf("processor type %d\n", (eax >> 12) & 0x3);
  printf("extended model %d\n", (eax >> 16) & 0xF);
  printf("extended family %d\n", (eax >> 20) & 0xFF);

  /* EDIT */
  eax = 3; /* processor serial number */
  native_cpuid(&eax, &ebx, &ecx, &edx);

  /** see the CPUID Wikipedia article on which models return the serial 
      number in which registers. The example here is for 
      Pentium III */
  printf("serial number 0x%08x%08x\n", edx, ecx);

}