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 <string.h>
  15#include <sys/stat.h>
  16#include <sys/types.h>
  17#include <sys/utsname.h>
  18#include <unistd.h>
  19
  20#include "utils.h"
  21
  22static char auxv[4096];
  23
  24int read_auxv(char *buf, ssize_t buf_size)
  25{
  26        ssize_t num;
  27        int rc, fd;
  28
  29        fd = open("/proc/self/auxv", O_RDONLY);
  30        if (fd == -1) {
  31                perror("open");
  32                return -errno;
  33        }
  34
  35        num = read(fd, buf, buf_size);
  36        if (num < 0) {
  37                perror("read");
  38                rc = -EIO;
  39                goto out;
  40        }
  41
  42        if (num > buf_size) {
  43                printf("overflowed auxv buffer\n");
  44                rc = -EOVERFLOW;
  45                goto out;
  46        }
  47
  48        rc = 0;
  49out:
  50        close(fd);
  51        return rc;
  52}
  53
  54void *find_auxv_entry(int type, char *auxv)
  55{
  56        ElfW(auxv_t) *p;
  57
  58        p = (ElfW(auxv_t) *)auxv;
  59
  60        while (p->a_type != AT_NULL) {
  61                if (p->a_type == type)
  62                        return p;
  63
  64                p++;
  65        }
  66
  67        return NULL;
  68}
  69
  70void *get_auxv_entry(int type)
  71{
  72        ElfW(auxv_t) *p;
  73
  74        if (read_auxv(auxv, sizeof(auxv)))
  75                return NULL;
  76
  77        p = find_auxv_entry(type, auxv);
  78        if (p)
  79                return (void *)p->a_un.a_val;
  80
  81        return NULL;
  82}
  83
  84int pick_online_cpu(void)
  85{
  86        cpu_set_t mask;
  87        int cpu;
  88
  89        CPU_ZERO(&mask);
  90
  91        if (sched_getaffinity(0, sizeof(mask), &mask)) {
  92                perror("sched_getaffinity");
  93                return -1;
  94        }
  95
  96        /* We prefer a primary thread, but skip 0 */
  97        for (cpu = 8; cpu < CPU_SETSIZE; cpu += 8)
  98                if (CPU_ISSET(cpu, &mask))
  99                        return cpu;
 100
 101        /* Search for anything, but in reverse */
 102        for (cpu = CPU_SETSIZE - 1; cpu >= 0; cpu--)
 103                if (CPU_ISSET(cpu, &mask))
 104                        return cpu;
 105
 106        printf("No cpus in affinity mask?!\n");
 107        return -1;
 108}
 109
 110bool is_ppc64le(void)
 111{
 112        struct utsname uts;
 113        int rc;
 114
 115        errno = 0;
 116        rc = uname(&uts);
 117        if (rc) {
 118                perror("uname");
 119                return false;
 120        }
 121
 122        return strcmp(uts.machine, "ppc64le") == 0;
 123}
 124