all_cpus.c

extern "C" {
/* from sys/osfmk/i386/mp.c */

extern void mp_rendezvous(void (*setup_func)(void *),
                          void (*action_func)(void *),
                          void (*teardown_func)(void *),
                          void *arg);

extern int cpu_number(void);
}

typedef struct {
    int os_id;
    int socket;
    int core;
    int apic;
} cpu_info_t;

static void topologyHelperFunction(void* data) {

    int values[4];
    cpu_info_t* cpus = (cpu_info_t*) data;
    int cpu = cpu_number();

    cpus[cpu].os_id = cpu;

    cpuid(0xB, 0, values);
    cpus[cpu].core = values[3] >> values[0] & 0xF

    cpuid(0xB, 1, values);
    cpus[cpu].socket = values[3] >> values[0] & 0xF

    cpus[cpu].apic = values[3];
}

static void getCpuidData() {
    int ncpu;
    size_t len = sizeof(int);
    sysctlbyname("hw.ncpu", &ncpu, &len, NULL, 0);

    cpu_info_t* values = (cpu_info_t*) malloc(sizeof(cpu_info_t) * ncpus);

    mp_rendevous(NULL, (void (*)(void *))topologyHelperFunction,
                 NULL, (void*) values);
}