tools/testing/selftests/proc/proc-loadavg-001.c

   1 /*
   2  * Copyright © 2018 Alexey Dobriyan <adobriyan@gmail.com>
   3  *
   4  * Permission to use, copy, modify, and distribute this software for any
   5  * purpose with or without fee is hereby granted, provided that the above
   6  * copyright notice and this permission notice appear in all copies.
   7  *
   8  * THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
   9  * WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
  10  * MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
  11  * ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
  12  * WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
  13  * ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
  14  * OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
  15  */
  16 /* Test that /proc/loadavg correctly reports last pid in pid namespace. */
  17 #include <errno.h>
  18 #include <sched.h>
  19 #include <sys/types.h>
  20 #include <sys/stat.h>
  21 #include <fcntl.h>
  22 #include <unistd.h>
  23 #include <sys/wait.h>
  24
  25 int main(void)
  26 {
  27         pid_t pid;
  28         int wstatus;
  29
  30         if (unshare(CLONE_NEWPID) == -1) {
  31                 if (errno == ENOSYS || errno == EPERM)
  32                         return 4;
  33                 return 1;
  34         }
  35
  36         pid = fork();
  37         if (pid == -1)
  38                 return 1;
  39         if (pid == 0) {
  40                 char buf[128], *p;
  41                 int fd;
  42                 ssize_t rv;
  43
  44                 fd = open("/proc/loadavg" , O_RDONLY);
  45                 if (fd == -1)
  46                         return 1;
  47                 rv = read(fd, buf, sizeof(buf));
  48                 if (rv < 3)
  49                         return 1;
  50                 p = buf + rv;
  51
  52                 /* pid 1 */
  53                 if (!(p[-3] == ' ' && p[-2] == '1' && p[-1] == '\n'))
  54                         return 1;
  55
  56                 pid = fork();
  57                 if (pid == -1)
  58                         return 1;
  59                 if (pid == 0)
  60                         return 0;
  61                 if (waitpid(pid, NULL, 0) == -1)
  62                         return 1;
  63
  64                 lseek(fd, 0, SEEK_SET);
  65                 rv = read(fd, buf, sizeof(buf));
  66                 if (rv < 3)
  67                         return 1;
  68                 p = buf + rv;
  69
  70                 /* pid 2 */
  71                 if (!(p[-3] == ' ' && p[-2] == '2' && p[-1] == '\n'))
  72                         return 1;
  73
  74                 return 0;
  75         }
  76
  77         if (waitpid(pid, &wstatus, 0) == -1)
  78                 return 1;
  79         if (WIFEXITED(wstatus) && WEXITSTATUS(wstatus) == 0)
  80                 return 0;
  81         return 1;
  82 }