nibbles blog

#define _GNU_SOURCE
#define __USE_GNU
 
#include <errno.h>
#include <stdio.h>
#include <sched.h>
 
struct dt_struct {
   unsigned short limit;
   unsigned long base;
} __attribute__((packed));
 
unsigned int get_sidt (void) {
   struct dt_struct idt;
   asm volatile ("sidt %0\t\n" : "=m"(idt));
   return idt.base;
}
 
unsigned int get_sgdt (void) {
   struct dt_struct gdt;
   asm volatile ("sgdt %0\t\n" : "=m"(gdt));
   return gdt.base;
}
 
int main (void) {
   int result = 0, cpu = 0, cpu2;
   cpu_set_t cs, cs2;
 
   if (sched_getaffinity (getpid (), sizeof (cs), &cs) != 0) {
      printf ("sched_getaffinity() failed : %m\n");
      return -1;
   }
 
   while (CPU_COUNT (&cs) != 0) {
      if (CPU_ISSET (cpu, &cs)) {
         CPU_ZERO (&cs2);
         CPU_SET (cpu, &cs2);
         if (sched_setaffinity (getpid (), sizeof (cs2), &cs2) != 0) {
            printf ("setaffinity(%d) failed: %m\n", cpu);
            result = 1;
         }
         else {
            cpu2 = sched_getcpu ();
            if (cpu2 == -1 && errno == ENOSYS) {
               puts ("getcpu syscall not implemented");
               return -1;
            }
            if (cpu2 != cpu) {
               printf ("getcpu results %d not possible\n", cpu2);
               result = 1;
            }
         }
         printf ("CPU %d\nIDT : 0x%08x\nGDT : 0x%08x\n\n", cpu, get_sidt(), get_sgdt());
         CPU_CLR (cpu, &cs);
      }
      ++cpu;
   }
   return 0;
}