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 #define _GNU_SOURCE
  18 #include <errno.h>
  19 #include <sched.h>
  20 #include <sys/types.h>
  21 #include <sys/stat.h>
  22 #include <fcntl.h>
  23 #include <unistd.h>
  24 #include <sys/wait.h>
  25
  26 int main(void)
  27 {
  28         pid_t pid;
  29         int wstatus;
  30
  31         if (unshare(CLONE_NEWPID) == -1) {
  32                 if (errno == ENOSYS || errno == EPERM)
  33                         return 4;
  34                 return 1;
  35         }
  36
  37         pid = fork();
  38         if (pid == -1)
  39                 return 1;
  40         if (pid == 0) {
  41                 char buf[128], *p;
  42                 int fd;
  43                 ssize_t rv;
  44
  45                 fd = open("/proc/loadavg" , O_RDONLY);
  46                 if (fd == -1)
  47                         return 1;
  48                 rv = read(fd, buf, sizeof(buf));
  49                 if (rv < 3)
  50                         return 1;
  51                 p = buf + rv;
  52
  53                 /* pid 1 */
  54                 if (!(p[-3] == ' ' && p[-2] == '1' && p[-1] == '\n'))
  55                         return 1;
  56
  57                 pid = fork();
  58                 if (pid == -1)
  59                         return 1;
  60                 if (pid == 0)
  61                         return 0;
  62                 if (waitpid(pid, NULL, 0) == -1)
  63                         return 1;
  64
  65                 lseek(fd, 0, SEEK_SET);
  66                 rv = read(fd, buf, sizeof(buf));
  67                 if (rv < 3)
  68                         return 1;
  69                 p = buf + rv;
  70
  71                 /* pid 2 */
  72                 if (!(p[-3] == ' ' && p[-2] == '2' && p[-1] == '\n'))
  73                         return 1;
  74
  75                 return 0;
  76         }
  77
  78         if (waitpid(pid, &wstatus, 0) == -1)
  79                 return 1;
  80         if (WIFEXITED(wstatus) && WEXITSTATUS(wstatus) == 0)
  81                 return 0;
  82         return 1;
  83 }