tools/lib/api/fs/cgroup.c

   1 // SPDX-License-Identifier: GPL-2.0
   2 #include <linux/stringify.h>
   3 #include <sys/types.h>
   4 #include <sys/stat.h>
   5 #include <fcntl.h>
   6 #include <stdio.h>
   7 #include <stdlib.h>
   8 #include <string.h>
   9 #include "fs.h"
  10
  11 int cgroupfs_find_mountpoint(char *buf, size_t maxlen, const char *subsys)
  12 {
  13         FILE *fp;
  14         char mountpoint[PATH_MAX + 1], tokens[PATH_MAX + 1], type[PATH_MAX + 1];
  15         char path_v1[PATH_MAX + 1], path_v2[PATH_MAX + 2], *path;
  16         char *token, *saved_ptr = NULL;
  17
  18         fp = fopen("/proc/mounts", "r");
  19         if (!fp)
  20                 return -1;
  21
  22         /*
  23          * in order to handle split hierarchy, we need to scan /proc/mounts
  24          * and inspect every cgroupfs mount point to find one that has
  25          * perf_event subsystem
  26          */
  27         path_v1[0] = '\0';
  28         path_v2[0] = '\0';
  29
  30         while (fscanf(fp, "%*s %"__stringify(PATH_MAX)"s %"__stringify(PATH_MAX)"s %"
  31                                 __stringify(PATH_MAX)"s %*d %*d\n",
  32                                 mountpoint, type, tokens) == 3) {
  33
  34                 if (!path_v1[0] && !strcmp(type, "cgroup")) {
  35
  36                         token = strtok_r(tokens, ",", &saved_ptr);
  37
  38                         while (token != NULL) {
  39                                 if (subsys && !strcmp(token, subsys)) {
  40                                         strcpy(path_v1, mountpoint);
  41                                         break;
  42                                 }
  43                                 token = strtok_r(NULL, ",", &saved_ptr);
  44                         }
  45                 }
  46
  47                 if (!path_v2[0] && !strcmp(type, "cgroup2"))
  48                         strcpy(path_v2, mountpoint);
  49
  50                 if (path_v1[0] && path_v2[0])
  51                         break;
  52         }
  53         fclose(fp);
  54
  55         if (path_v1[0])
  56                 path = path_v1;
  57         else if (path_v2[0])
  58                 path = path_v2;
  59         else
  60                 return -1;
  61
  62         if (strlen(path) < maxlen) {
  63                 strcpy(buf, path);
  64                 return 0;
  65         }
  66         return -1;
  67 }