root/tools/testing/selftests/bpf/cgroup_helpers.c

DEFINITIONS

1. enable_all_controllers
2. setup_cgroup_environment
3. nftwfunc
4. join_cgroup_from_top
5. join_cgroup
6. cleanup_cgroup_environment
7. create_and_get_cgroup
8. get_cgroup_id

   1 // SPDX-License-Identifier: GPL-2.0
   2 #define _GNU_SOURCE
   3 #include <sched.h>
   4 #include <sys/mount.h>
   5 #include <sys/stat.h>
   6 #include <sys/types.h>
   7 #include <linux/limits.h>
   8 #include <stdio.h>
   9 #include <stdlib.h>
  10 #include <linux/sched.h>
  11 #include <fcntl.h>
  12 #include <unistd.h>
  13 #include <ftw.h>
  14 
  15 
  16 #include "cgroup_helpers.h"
  17 
  18 /*
  19  * To avoid relying on the system setup, when setup_cgroup_env is called
  20  * we create a new mount namespace, and cgroup namespace. The cgroup2
  21  * root is mounted at CGROUP_MOUNT_PATH
  22  *
  23  * Unfortunately, most people don't have cgroupv2 enabled at this point in time.
  24  * It's easier to create our own mount namespace and manage it ourselves.
  25  *
  26  * We assume /mnt exists.
  27  */
  28 
  29 #define WALK_FD_LIMIT                   16
  30 #define CGROUP_MOUNT_PATH               "/mnt"
  31 #define CGROUP_WORK_DIR                 "/cgroup-test-work-dir"
  32 #define format_cgroup_path(buf, path) \
  33         snprintf(buf, sizeof(buf), "%s%s%s", CGROUP_MOUNT_PATH, \
  34                  CGROUP_WORK_DIR, path)
  35 
  36 /**
  37  * enable_all_controllers() - Enable all available cgroup v2 controllers
  38  *
  39  * Enable all available cgroup v2 controllers in order to increase
  40  * the code coverage.
  41  *
  42  * If successful, 0 is returned.
  43  */
  44 int enable_all_controllers(char *cgroup_path)
  45 {
  46         char path[PATH_MAX + 1];
  47         char buf[PATH_MAX];
  48         char *c, *c2;
  49         int fd, cfd;
  50         ssize_t len;
  51 
  52         snprintf(path, sizeof(path), "%s/cgroup.controllers", cgroup_path);
  53         fd = open(path, O_RDONLY);
  54         if (fd < 0) {
  55                 log_err("Opening cgroup.controllers: %s", path);
  56                 return 1;
  57         }
  58 
  59         len = read(fd, buf, sizeof(buf) - 1);
  60         if (len < 0) {
  61                 close(fd);
  62                 log_err("Reading cgroup.controllers: %s", path);
  63                 return 1;
  64         }
  65         buf[len] = 0;
  66         close(fd);
  67 
  68         /* No controllers available? We're probably on cgroup v1. */
  69         if (len == 0)
  70                 return 0;
  71 
  72         snprintf(path, sizeof(path), "%s/cgroup.subtree_control", cgroup_path);
  73         cfd = open(path, O_RDWR);
  74         if (cfd < 0) {
  75                 log_err("Opening cgroup.subtree_control: %s", path);
  76                 return 1;
  77         }
  78 
  79         for (c = strtok_r(buf, " ", &c2); c; c = strtok_r(NULL, " ", &c2)) {
  80                 if (dprintf(cfd, "+%s\n", c) <= 0) {
  81                         log_err("Enabling controller %s: %s", c, path);
  82                         close(cfd);
  83                         return 1;
  84                 }
  85         }
  86         close(cfd);
  87         return 0;
  88 }
  89 
  90 /**
  91  * setup_cgroup_environment() - Setup the cgroup environment
  92  *
  93  * After calling this function, cleanup_cgroup_environment should be called
  94  * once testing is complete.
  95  *
  96  * This function will print an error to stderr and return 1 if it is unable
  97  * to setup the cgroup environment. If setup is successful, 0 is returned.
  98  */
  99 int setup_cgroup_environment(void)
 100 {
 101         char cgroup_workdir[PATH_MAX - 24];
 102 
 103         format_cgroup_path(cgroup_workdir, "");
 104 
 105         if (unshare(CLONE_NEWNS)) {
 106                 log_err("unshare");
 107                 return 1;
 108         }
 109 
 110         if (mount("none", "/", NULL, MS_REC | MS_PRIVATE, NULL)) {
 111                 log_err("mount fakeroot");
 112                 return 1;
 113         }
 114 
 115         if (mount("none", CGROUP_MOUNT_PATH, "cgroup2", 0, NULL) && errno != EBUSY) {
 116                 log_err("mount cgroup2");
 117                 return 1;
 118         }
 119 
 120         /* Cleanup existing failed runs, now that the environment is setup */
 121         cleanup_cgroup_environment();
 122 
 123         if (mkdir(cgroup_workdir, 0777) && errno != EEXIST) {
 124                 log_err("mkdir cgroup work dir");
 125                 return 1;
 126         }
 127 
 128         if (enable_all_controllers(cgroup_workdir))
 129                 return 1;
 130 
 131         return 0;
 132 }
 133 
 134 static int nftwfunc(const char *filename, const struct stat *statptr,
 135                     int fileflags, struct FTW *pfwt)
 136 {
 137         if ((fileflags & FTW_D) && rmdir(filename))
 138                 log_err("Removing cgroup: %s", filename);
 139         return 0;
 140 }
 141 
 142 
 143 static int join_cgroup_from_top(char *cgroup_path)
 144 {
 145         char cgroup_procs_path[PATH_MAX + 1];
 146         pid_t pid = getpid();
 147         int fd, rc = 0;
 148 
 149         snprintf(cgroup_procs_path, sizeof(cgroup_procs_path),
 150                  "%s/cgroup.procs", cgroup_path);
 151 
 152         fd = open(cgroup_procs_path, O_WRONLY);
 153         if (fd < 0) {
 154                 log_err("Opening Cgroup Procs: %s", cgroup_procs_path);
 155                 return 1;
 156         }
 157 
 158         if (dprintf(fd, "%d\n", pid) < 0) {
 159                 log_err("Joining Cgroup");
 160                 rc = 1;
 161         }
 162 
 163         close(fd);
 164         return rc;
 165 }
 166 
 167 /**
 168  * join_cgroup() - Join a cgroup
 169  * @path: The cgroup path, relative to the workdir, to join
 170  *
 171  * This function expects a cgroup to already be created, relative to the cgroup
 172  * work dir, and it joins it. For example, passing "/my-cgroup" as the path
 173  * would actually put the calling process into the cgroup
 174  * "/cgroup-test-work-dir/my-cgroup"
 175  *
 176  * On success, it returns 0, otherwise on failure it returns 1.
 177  */
 178 int join_cgroup(const char *path)
 179 {
 180         char cgroup_path[PATH_MAX + 1];
 181 
 182         format_cgroup_path(cgroup_path, path);
 183         return join_cgroup_from_top(cgroup_path);
 184 }
 185 
 186 /**
 187  * cleanup_cgroup_environment() - Cleanup Cgroup Testing Environment
 188  *
 189  * This is an idempotent function to delete all temporary cgroups that
 190  * have been created during the test, including the cgroup testing work
 191  * directory.
 192  *
 193  * At call time, it moves the calling process to the root cgroup, and then
 194  * runs the deletion process. It is idempotent, and should not fail, unless
 195  * a process is lingering.
 196  *
 197  * On failure, it will print an error to stderr, and try to continue.
 198  */
 199 void cleanup_cgroup_environment(void)
 200 {
 201         char cgroup_workdir[PATH_MAX + 1];
 202 
 203         format_cgroup_path(cgroup_workdir, "");
 204         join_cgroup_from_top(CGROUP_MOUNT_PATH);
 205         nftw(cgroup_workdir, nftwfunc, WALK_FD_LIMIT, FTW_DEPTH | FTW_MOUNT);
 206 }
 207 
 208 /**
 209  * create_and_get_cgroup() - Create a cgroup, relative to workdir, and get the FD
 210  * @path: The cgroup path, relative to the workdir, to join
 211  *
 212  * This function creates a cgroup under the top level workdir and returns the
 213  * file descriptor. It is idempotent.
 214  *
 215  * On success, it returns the file descriptor. On failure it returns -1.
 216  * If there is a failure, it prints the error to stderr.
 217  */
 218 int create_and_get_cgroup(const char *path)
 219 {
 220         char cgroup_path[PATH_MAX + 1];
 221         int fd;
 222 
 223         format_cgroup_path(cgroup_path, path);
 224         if (mkdir(cgroup_path, 0777) && errno != EEXIST) {
 225                 log_err("mkdiring cgroup %s .. %s", path, cgroup_path);
 226                 return -1;
 227         }
 228 
 229         fd = open(cgroup_path, O_RDONLY);
 230         if (fd < 0) {
 231                 log_err("Opening Cgroup");
 232                 return -1;
 233         }
 234 
 235         return fd;
 236 }
 237 
 238 /**
 239  * get_cgroup_id() - Get cgroup id for a particular cgroup path
 240  * @path: The cgroup path, relative to the workdir, to join
 241  *
 242  * On success, it returns the cgroup id. On failure it returns 0,
 243  * which is an invalid cgroup id.
 244  * If there is a failure, it prints the error to stderr.
 245  */
 246 unsigned long long get_cgroup_id(const char *path)
 247 {
 248         int dirfd, err, flags, mount_id, fhsize;
 249         union {
 250                 unsigned long long cgid;
 251                 unsigned char raw_bytes[8];
 252         } id;
 253         char cgroup_workdir[PATH_MAX + 1];
 254         struct file_handle *fhp, *fhp2;
 255         unsigned long long ret = 0;
 256 
 257         format_cgroup_path(cgroup_workdir, path);
 258 
 259         dirfd = AT_FDCWD;
 260         flags = 0;
 261         fhsize = sizeof(*fhp);
 262         fhp = calloc(1, fhsize);
 263         if (!fhp) {
 264                 log_err("calloc");
 265                 return 0;
 266         }
 267         err = name_to_handle_at(dirfd, cgroup_workdir, fhp, &mount_id, flags);
 268         if (err >= 0 || fhp->handle_bytes != 8) {
 269                 log_err("name_to_handle_at");
 270                 goto free_mem;
 271         }
 272 
 273         fhsize = sizeof(struct file_handle) + fhp->handle_bytes;
 274         fhp2 = realloc(fhp, fhsize);
 275         if (!fhp2) {
 276                 log_err("realloc");
 277                 goto free_mem;
 278         }
 279         err = name_to_handle_at(dirfd, cgroup_workdir, fhp2, &mount_id, flags);
 280         fhp = fhp2;
 281         if (err < 0) {
 282                 log_err("name_to_handle_at");
 283                 goto free_mem;
 284         }
 285 
 286         memcpy(id.raw_bytes, fhp->f_handle, 8);
 287         ret = id.cgid;
 288 
 289 free_mem:
 290         free(fhp);
 291         return ret;
 292 }