LXR linux/tools/testing/selftests/powerpc/utils.c

   1/*
   2 * Copyright 2013-2015, Michael Ellerman, IBM Corp.
   3 * Licensed under GPLv2.
   4 */
   5
   6#define _GNU_SOURCE     /* For CPU_ZERO etc. */
   7
   8#include <elf.h>
   9#include <errno.h>
  10#include <fcntl.h>
  11#include <link.h>
  12#include <sched.h>
  13#include <stdio.h>
  14#include <sys/stat.h>
  15#include <sys/types.h>
  16#include <unistd.h>
  17
  18#include "utils.h"
  19
  20static char auxv[4096];
  21
  22void *get_auxv_entry(int type)
  23{
  24        ElfW(auxv_t) *p;
  25        void *result;
  26        ssize_t num;
  27        int fd;
  28
  29        fd = open("/proc/self/auxv", O_RDONLY);
  30        if (fd == -1) {
  31                perror("open");
  32                return NULL;
  33        }
  34
  35        result = NULL;
  36
  37        num = read(fd, auxv, sizeof(auxv));
  38        if (num < 0) {
  39                perror("read");
  40                goto out;
  41        }
  42
  43        if (num > sizeof(auxv)) {
  44                printf("Overflowed auxv buffer\n");
  45                goto out;
  46        }
  47
  48        p = (ElfW(auxv_t) *)auxv;
  49
  50        while (p->a_type != AT_NULL) {
  51                if (p->a_type == type) {
  52                        result = (void *)p->a_un.a_val;
  53                        break;
  54                }
  55
  56                p++;
  57        }
  58out:
  59        close(fd);
  60        return result;
  61}
  62
  63int pick_online_cpu(void)
  64{
  65        cpu_set_t mask;
  66        int cpu;
  67
  68        CPU_ZERO(&mask);
  69
  70        if (sched_getaffinity(0, sizeof(mask), &mask)) {
  71                perror("sched_getaffinity");
  72                return -1;
  73        }
  74
  75        /* We prefer a primary thread, but skip 0 */
  76        for (cpu = 8; cpu < CPU_SETSIZE; cpu += 8)
  77                if (CPU_ISSET(cpu, &mask))
  78                        return cpu;
  79
  80        /* Search for anything, but in reverse */
  81        for (cpu = CPU_SETSIZE - 1; cpu >= 0; cpu--)
  82                if (CPU_ISSET(cpu, &mask))
  83                        return cpu;
  84
  85        printf("No cpus in affinity mask?!\n");
  86        return -1;
  87}
  88