// in my PC, file location is /usr/lib/gcc/x86_64-linux-gnu/5/include/cpuid.h #define __cpuid(level, a, b, c, d) \ __asm__ ("cpuid\n\t" \ : "=a" (a), "=b" (b), "=c" (c), "=d" (d) \ : "0" (level))