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 } 68