cpuid

#include
static inline void cpuid(unsigned int op,
                         unsigned int *eax, unsigned int *ebx,
                         unsigned int *ecx, unsigned int *edx)
{
        *eax = op;
        *ecx = 0;
        asm("cpuid"
            : "=a" (*eax),
              "=b" (*ebx),
              "=c" (*ecx),
              "=d" (*edx)
            : "0" (*eax), "2" (*ecx));

}

int main(void)
{
        unsigned int v[4];
        cpuid(0x80000001,&v[0],&v[1],&v[2],&v[3]);
        if(v[3] & (1<<20))
                printf("it has actived PAE!\n");
        else
                printf("not active PAE!\n");
        printf("\n");
        printf("EAX output:%#x\n",v[0]);
        printf("EBX output:%#x\n",v[1]);
        printf("ECX output:%#x\n",v[2]);
        printf("EDX output:%#x\n",v[3]);
        return 0;
}