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
  22 static char auxv[4096];
  23
  24 int 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;
  49 out:
  50         close(fd);
  51         return rc;
  52 }
  53
  54 void *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
  70 void *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
  84 int 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
 110 bool 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 }