LXR linux/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
  11int 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}
  68