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