bindings.c

   1 /* lxcfs
   2  *
   3  * Copyright © 2014-2016 Canonical, Inc
   4  * Author: Serge Hallyn <serge.hallyn@ubuntu.com>
   5  *
   6  * See COPYING file for details.
   7  */
   8
   9 #ifndef _GNU_SOURCE
  10 #define _GNU_SOURCE
  11 #endif
  12
  13 #ifndef FUSE_USE_VERSION
  14 #define FUSE_USE_VERSION 26
  15 #endif
  16
  17 #define _FILE_OFFSET_BITS 64
  18
  19 #include <dirent.h>
  20 #include <errno.h>
  21 #include <fcntl.h>
  22 #include <fuse.h>
  23 #include <inttypes.h>
  24 #include <libgen.h>
  25 #include <pthread.h>
  26 #include <sched.h>
  27 #include <stdarg.h>
  28 #include <stdbool.h>
  29 #include <stdint.h>
  30 #include <stdio.h>
  31 #include <stdlib.h>
  32 #include <string.h>
  33 #include <time.h>
  34 #include <unistd.h>
  35 #include <wait.h>
  36 #include <linux/magic.h>
  37 #include <linux/sched.h>
  38 #include <sys/epoll.h>
  39 #include <sys/mman.h>
  40 #include <sys/mount.h>
  41 #include <sys/param.h>
  42 #include <signal.h>
  43 #include <sys/socket.h>
  44 #include <sys/syscall.h>
  45 #include <sys/sysinfo.h>
  46 #include <sys/vfs.h>
  47
  48 #include "api_extensions.h"
  49 #include "bindings.h"
  50 #include "config.h"
  51 #include "cgroup_fuse.h"
  52 #include "cgroups/cgroup.h"
  53 #include "cgroups/cgroup_utils.h"
  54 #include "memory_utils.h"
  55 #include "proc_cpuview.h"
  56 #include "utils.h"
  57
  58 static bool can_use_pidfd;
  59
  60 /* Define pivot_root() if missing from the C library */
  61 #ifndef HAVE_PIVOT_ROOT
  62 static int pivot_root(const char *new_root, const char *put_old)
  63 {
  64 #ifdef __NR_pivot_root
  65         return syscall(__NR_pivot_root, new_root, put_old);
  66 #else
  67         errno = ENOSYS;
  68         return -1;
  69 #endif
  70 }
  71 #else
  72 extern int pivot_root(const char *new_root, const char *put_old);
  73 #endif
  74
  75 /*
  76  * A table caching which pid is init for a pid namespace.
  77  * When looking up which pid is init for $qpid, we first
  78  * 1. Stat /proc/$qpid/ns/pid.
  79  * 2. Check whether the ino_t is in our store.
  80  *   a. if not, fork a child in qpid's ns to send us
  81  *       ucred.pid = 1, and read the initpid.  Cache
  82  *       initpid and creation time for /proc/initpid
  83  *       in a new store entry.
  84  *   b. if so, verify that /proc/initpid still matches
  85  *       what we have saved.  If not, clear the store
  86  *       entry and go back to a.  If so, return the
  87  *       cached initpid.
  88  */
  89 struct pidns_init_store {
  90         ino_t ino;     /* inode number for /proc/$pid/ns/pid */
  91         pid_t initpid; /* the pid of nit in that ns */
  92         int init_pidfd;
  93         long int ctime; /* the time at which /proc/$initpid was created */
  94         struct pidns_init_store *next;
  95         long int lastcheck;
  96 };
  97
  98 /* lol - look at how they are allocated in the kernel */
  99 #define PIDNS_HASH_SIZE 4096
 100 #define HASH(x) ((x) % PIDNS_HASH_SIZE)
 101
 102 static struct pidns_init_store *pidns_hash_table[PIDNS_HASH_SIZE];
 103 static pthread_mutex_t pidns_store_mutex = PTHREAD_MUTEX_INITIALIZER;
 104
 105 static void lock_mutex(pthread_mutex_t *l)
 106 {
 107         int ret;
 108
 109         ret = pthread_mutex_lock(l);
 110         if (ret)
 111                 log_exit("%s - returned %d\n", strerror(ret), ret);
 112 }
 113
 114 struct cgroup_ops *cgroup_ops;
 115
 116 static void unlock_mutex(pthread_mutex_t *l)
 117 {
 118         int ret;
 119
 120         ret = pthread_mutex_unlock(l);
 121         if (ret)
 122                 log_exit("%s - returned %d\n", strerror(ret), ret);
 123 }
 124
 125 static void store_lock(void)
 126 {
 127         lock_mutex(&pidns_store_mutex);
 128 }
 129
 130 static void store_unlock(void)
 131 {
 132         unlock_mutex(&pidns_store_mutex);
 133 }
 134
 135 /* /proc/       =    6
 136  *                +
 137  * <pid-as-str> =   INTTYPE_TO_STRLEN(pid_t)
 138  *                +
 139  * \0           =    1
 140  */
 141 #define LXCFS_PROC_PID_LEN \
 142         (STRLITERALLEN("/proc/") + INTTYPE_TO_STRLEN(uint64_t) + +1)
 143
 144 /* Must be called under store_lock */
 145 static bool initpid_still_valid(struct pidns_init_store *entry)
 146 {
 147         bool valid = true;
 148
 149         if (entry->init_pidfd >= 0) {
 150                 if (pidfd_send_signal(entry->init_pidfd, 0, NULL, 0))
 151                         valid = false;
 152         } else {
 153                 struct stat st;
 154                 char path[LXCFS_PROC_PID_LEN];
 155
 156                 snprintf(path, sizeof(path), "/proc/%d", entry->initpid);
 157
 158                 if (stat(path, &st) || entry->ctime != st.st_ctime)
 159                         valid = false;
 160         }
 161
 162         return valid;
 163 }
 164
 165 /* Must be called under store_lock */
 166 static void remove_initpid(struct pidns_init_store *entry)
 167 {
 168         struct pidns_init_store *it;
 169         int ino_hash;
 170
 171         lxcfs_debug("Removing cached entry for pid %d from init pid cache",
 172                     entry->initpid);
 173
 174         ino_hash = HASH(entry->ino);
 175         if (pidns_hash_table[ino_hash] == entry) {
 176                 pidns_hash_table[ino_hash] = entry->next;
 177                 close_prot_errno_disarm(entry->init_pidfd);
 178                 free_disarm(entry);
 179                 return;
 180         }
 181
 182         it = pidns_hash_table[ino_hash];
 183         while (it) {
 184                 if (it->next == entry) {
 185                         it->next = entry->next;
 186                         close_prot_errno_disarm(entry->init_pidfd);
 187                         free_disarm(entry);
 188                         return;
 189                 }
 190                 it = it->next;
 191         }
 192 }
 193
 194 #define PURGE_SECS 5
 195 /* Must be called under store_lock */
 196 static void prune_initpid_store(void)
 197 {
 198         static long int last_prune = 0;
 199         long int now, threshold;
 200
 201         if (!last_prune) {
 202                 last_prune = time(NULL);
 203                 return;
 204         }
 205
 206         now = time(NULL);
 207         if (now < last_prune + PURGE_SECS)
 208                 return;
 209
 210         lxcfs_debug("Pruning init pid cache");
 211
 212         last_prune = now;
 213         threshold = now - 2 * PURGE_SECS;
 214
 215         for (int i = 0; i < PIDNS_HASH_SIZE; i++) {
 216                 for (struct pidns_init_store *entry = pidns_hash_table[i], *prev = NULL; entry;) {
 217                         if (entry->lastcheck < threshold) {
 218                                 struct pidns_init_store *cur = entry;
 219
 220                                 lxcfs_debug("Removed cache entry for pid %d to init pid cache", cur->initpid);
 221
 222                                 if (prev)
 223                                         prev->next = entry->next;
 224                                 else
 225                                         pidns_hash_table[i] = entry->next;
 226                                 entry = entry->next;
 227                                 close_prot_errno_disarm(cur->init_pidfd);
 228                                 free_disarm(cur);
 229                         } else {
 230                                 prev = entry;
 231                                 entry = entry->next;
 232                         }
 233                 }
 234         }
 235 }
 236
 237 /* Must be called under store_lock */
 238 static void save_initpid(struct stat *sb, pid_t pid)
 239 {
 240         __do_free struct pidns_init_store *entry = NULL;
 241         __do_close_prot_errno int pidfd = -EBADF;
 242         char path[LXCFS_PROC_PID_LEN];
 243         struct lxcfs_opts *opts = fuse_get_context()->private_data;
 244         struct stat st;
 245         int ino_hash;
 246
 247         if (opts->use_pidfd && can_use_pidfd) {
 248                 pidfd = pidfd_open(pid, 0);
 249                 if (pidfd < 0)
 250                         return;
 251         }
 252
 253         snprintf(path, sizeof(path), "/proc/%d", pid);
 254         if (stat(path, &st))
 255                 return;
 256
 257         entry = malloc(sizeof(*entry));
 258         if (entry)
 259                 return;
 260
 261         ino_hash = HASH(entry->ino);
 262         *entry = (struct pidns_init_store){
 263                 .ino            = sb->st_ino,
 264                 .initpid        = pid,
 265                 .ctime          = st.st_ctime,
 266                 .next           = pidns_hash_table[ino_hash],
 267                 .lastcheck      = time(NULL),
 268                 .init_pidfd     = move_fd(pidfd),
 269         };
 270         pidns_hash_table[ino_hash] = move_ptr(entry);
 271
 272         lxcfs_debug("Added cache entry %d for pid %d to init pid cache", ino_hash, pid);
 273 }
 274
 275 /*
 276  * Given the stat(2) info for a nsfd pid inode, lookup the init_pid_store
 277  * entry for the inode number and creation time.  Verify that the init pid
 278  * is still valid.  If not, remove it.  Return the entry if valid, NULL
 279  * otherwise.
 280  * Must be called under store_lock
 281  */
 282 static struct pidns_init_store *lookup_verify_initpid(struct stat *sb)
 283 {
 284         struct pidns_init_store *entry = pidns_hash_table[HASH(sb->st_ino)];
 285
 286         while (entry) {
 287                 if (entry->ino == sb->st_ino) {
 288                         if (initpid_still_valid(entry)) {
 289                                 entry->lastcheck = time(NULL);
 290                                 return entry;
 291                         }
 292
 293                         remove_initpid(entry);
 294                         return NULL;
 295                 }
 296                 entry = entry->next;
 297         }
 298
 299         return NULL;
 300 }
 301
 302 static int send_creds_clone_wrapper(void *arg)
 303 {
 304         int sock = PTR_TO_INT(arg);
 305         char v = '1'; /* we are the child */
 306         struct ucred cred = {
 307             .uid = 0,
 308             .gid = 0,
 309             .pid = 1,
 310         };
 311
 312         return send_creds(sock, &cred, v, true) != SEND_CREDS_OK;
 313 }
 314
 315 /*
 316  * Let's use the "standard stack limit" (i.e. glibc thread size default) for
 317  * stack sizes: 8MB.
 318  */
 319 #define __LXCFS_STACK_SIZE (8 * 1024 * 1024)
 320 static pid_t lxcfs_clone(int (*fn)(void *), void *arg, int flags)
 321 {
 322         pid_t ret;
 323         void *stack;
 324
 325         stack = malloc(__LXCFS_STACK_SIZE);
 326         if (!stack)
 327                 return ret_errno(ENOMEM);
 328
 329 #ifdef __ia64__
 330         ret = __clone2(fn, stack, __LXCFS_STACK_SIZE, flags | SIGCHLD, arg, NULL);
 331 #else
 332         ret = clone(fn, stack + __LXCFS_STACK_SIZE, flags | SIGCHLD, arg, NULL);
 333 #endif
 334         return ret;
 335 }
 336
 337 #define LXCFS_PROC_PID_NS_LEN                                    \
 338         (STRLITERALLEN("/proc/") + INTTYPE_TO_STRLEN(uint64_t) + \
 339          STRLITERALLEN("/ns/pid") + 1)
 340
 341 /*
 342  * clone a task which switches to @task's namespace and writes '1'.
 343  * over a unix sock so we can read the task's reaper's pid in our
 344  * namespace
 345  *
 346  * Note: glibc's fork() does not respect pidns, which can lead to failed
 347  * assertions inside glibc (and thus failed forks) if the child's pid in
 348  * the pidns and the parent pid outside are identical. Using clone prevents
 349  * this issue.
 350  */
 351 static void write_task_init_pid_exit(int sock, pid_t target)
 352 {
 353         __do_close_prot_errno int fd = -EBADF;
 354         char path[LXCFS_PROC_PID_NS_LEN];
 355         pid_t pid;
 356
 357         snprintf(path, sizeof(path), "/proc/%d/ns/pid", (int)target);
 358         fd = open(path, O_RDONLY | O_CLOEXEC);
 359         if (fd < 0)
 360                 log_exit("write_task_init_pid_exit open of ns/pid");
 361
 362         if (setns(fd, 0))
 363                 log_exit("Failed to setns to pid namespace of process %d", target);
 364
 365         pid = lxcfs_clone(send_creds_clone_wrapper, INT_TO_PTR(sock), 0);
 366         if (pid < 0)
 367                 _exit(EXIT_FAILURE);
 368
 369         if (pid != 0) {
 370                 if (!wait_for_pid(pid))
 371                         _exit(EXIT_FAILURE);
 372
 373                 _exit(EXIT_SUCCESS);
 374         }
 375 }
 376
 377 static pid_t get_init_pid_for_task(pid_t task)
 378 {
 379         char v = '0';
 380         pid_t pid_ret = -1;
 381         pid_t pid;
 382         int sock[2];
 383         struct ucred cred;
 384
 385         if (socketpair(AF_UNIX, SOCK_DGRAM, 0, sock) < 0)
 386                 return -1;
 387
 388         pid = fork();
 389         if (pid < 0)
 390                 goto out;
 391
 392         if (pid == 0) {
 393                 close(sock[1]);
 394                 write_task_init_pid_exit(sock[0], task);
 395                 _exit(EXIT_SUCCESS);
 396         }
 397
 398         if (!recv_creds(sock[1], &cred, &v))
 399                 goto out;
 400
 401         pid_ret = cred.pid;
 402
 403 out:
 404         close(sock[0]);
 405         close(sock[1]);
 406         if (pid > 0)
 407                 wait_for_pid(pid);
 408
 409         return pid_ret;
 410 }
 411
 412 pid_t lookup_initpid_in_store(pid_t pid)
 413 {
 414         pid_t answer = 0;
 415         char path[LXCFS_PROC_PID_NS_LEN];
 416         struct stat st;
 417         struct pidns_init_store *entry;
 418
 419         snprintf(path, sizeof(path), "/proc/%d/ns/pid", pid);
 420
 421         store_lock();
 422         if (stat(path, &st))
 423                 goto out;
 424
 425         entry = lookup_verify_initpid(&st);
 426         if (entry) {
 427                 answer = entry->initpid;
 428                 goto out;
 429         }
 430
 431         answer = get_init_pid_for_task(pid);
 432         if (answer > 0)
 433                 save_initpid(&st, answer);
 434
 435 out:
 436         /*
 437          * Prune at the end in case we're returning the value we were about to
 438          * return.
 439          */
 440         prune_initpid_store();
 441
 442         store_unlock();
 443
 444         return answer;
 445 }
 446
 447 /*
 448  * Functions needed to setup cgroups in the __constructor__.
 449  */
 450
 451 static bool umount_if_mounted(void)
 452 {
 453         if (umount2(BASEDIR, MNT_DETACH) < 0 && errno != EINVAL) {
 454                 lxcfs_error("Failed to unmount %s: %s.\n", BASEDIR, strerror(errno));
 455                 return false;
 456         }
 457         return true;
 458 }
 459
 460 /* __typeof__ should be safe to use with all compilers. */
 461 typedef __typeof__(((struct statfs *)NULL)->f_type) fs_type_magic;
 462 static bool has_fs_type(const struct statfs *fs, fs_type_magic magic_val)
 463 {
 464         return (fs->f_type == (fs_type_magic)magic_val);
 465 }
 466
 467 /*
 468  * looking at fs/proc_namespace.c, it appears we can
 469  * actually expect the rootfs entry to very specifically contain
 470  * " - rootfs rootfs "
 471  * IIUC, so long as we've chrooted so that rootfs is not our root,
 472  * the rootfs entry should always be skipped in mountinfo contents.
 473  */
 474 static bool is_on_ramfs(void)
 475 {
 476         __do_free char *line = NULL;
 477         __do_fclose FILE *f = NULL;
 478         size_t len = 0;
 479
 480         f = fopen("/proc/self/mountinfo", "re");
 481         if (!f)
 482                 return false;
 483
 484         while (getline(&line, &len, f) != -1) {
 485                 int i;
 486                 char *p, *p2;
 487
 488                 for (p = line, i = 0; p && i < 4; i++)
 489                         p = strchr(p + 1, ' ');
 490                 if (!p)
 491                         continue;
 492
 493                 p2 = strchr(p + 1, ' ');
 494                 if (!p2)
 495                         continue;
 496                 *p2 = '\0';
 497                 if (strcmp(p + 1, "/") == 0) {
 498                         /* This is '/'. Is it the ramfs? */
 499                         p = strchr(p2 + 1, '-');
 500                         if (p && strncmp(p, "- rootfs rootfs ", 16) == 0)
 501                                 return true;
 502                 }
 503         }
 504
 505         return false;
 506 }
 507
 508 static int pivot_enter()
 509 {
 510         __do_close_prot_errno int oldroot = -EBADF, newroot = -EBADF;
 511
 512         oldroot = open("/", O_DIRECTORY | O_RDONLY);
 513         if (oldroot < 0)
 514                 return log_error_errno(-1, errno,
 515                                        "Failed to open old root for fchdir");
 516
 517         newroot = open(ROOTDIR, O_DIRECTORY | O_RDONLY);
 518         if (newroot < 0)
 519                 return log_error_errno(-1, errno,
 520                                        "Failed to open new root for fchdir");
 521
 522         /* change into new root fs */
 523         if (fchdir(newroot) < 0)
 524                 return log_error_errno(-1,
 525                                        errno, "Failed to change directory to new rootfs: %s",
 526                                        ROOTDIR);
 527
 528         /* pivot_root into our new root fs */
 529         if (pivot_root(".", ".") < 0)
 530                 return log_error_errno(-1, errno,
 531                                        "pivot_root() syscall failed: %s",
 532                                        strerror(errno));
 533
 534         /*
 535          * At this point the old-root is mounted on top of our new-root.
 536          * To unmounted it we must not be chdir'd into it, so escape back
 537          * to the old-root.
 538          */
 539         if (fchdir(oldroot) < 0)
 540                 return log_error_errno(-1, errno, "Failed to enter old root");
 541
 542         if (umount2(".", MNT_DETACH) < 0)
 543                 return log_error_errno(-1, errno, "Failed to detach old root");
 544
 545         if (fchdir(newroot) < 0)
 546                 return log_error_errno(-1, errno, "Failed to re-enter new root");
 547
 548         return 0;
 549 }
 550
 551 static int chroot_enter()
 552 {
 553         if (mount(ROOTDIR, "/", NULL, MS_REC | MS_BIND, NULL)) {
 554                 lxcfs_error("Failed to recursively bind-mount %s into /.", ROOTDIR);
 555                 return -1;
 556         }
 557
 558         if (chroot(".") < 0) {
 559                 lxcfs_error("Call to chroot() failed: %s.\n", strerror(errno));
 560                 return -1;
 561         }
 562
 563         if (chdir("/") < 0) {
 564                 lxcfs_error("Failed to change directory: %s.\n", strerror(errno));
 565                 return -1;
 566         }
 567
 568         return 0;
 569 }
 570
 571 static int permute_and_enter(void)
 572 {
 573         struct statfs sb;
 574
 575         if (statfs("/", &sb) < 0) {
 576                 lxcfs_error("%s\n", "Could not stat / mountpoint.");
 577                 return -1;
 578         }
 579
 580         /* has_fs_type() is not reliable. When the ramfs is a tmpfs it will
 581          * likely report TMPFS_MAGIC. Hence, when it reports no we still check
 582          * /proc/1/mountinfo. */
 583         if (has_fs_type(&sb, RAMFS_MAGIC) || is_on_ramfs())
 584                 return chroot_enter();
 585
 586         if (pivot_enter() < 0) {
 587                 lxcfs_error("%s\n", "Could not perform pivot root.");
 588                 return -1;
 589         }
 590
 591         return 0;
 592 }
 593
 594 /* Prepare our new clean root. */
 595 static int permute_prepare(void)
 596 {
 597         if (mkdir(ROOTDIR, 0700) < 0 && errno != EEXIST) {
 598                 lxcfs_error("%s\n", "Failed to create directory for new root.");
 599                 return -1;
 600         }
 601
 602         if (mount("/", ROOTDIR, NULL, MS_BIND, 0) < 0) {
 603                 lxcfs_error("Failed to bind-mount / for new root: %s.\n", strerror(errno));
 604                 return -1;
 605         }
 606
 607         if (mount(RUNTIME_PATH, ROOTDIR RUNTIME_PATH, NULL, MS_BIND, 0) < 0) {
 608                 lxcfs_error("Failed to bind-mount /run into new root: %s.\n", strerror(errno));
 609                 return -1;
 610         }
 611
 612         if (mount(BASEDIR, ROOTDIR BASEDIR, NULL, MS_REC | MS_MOVE, 0) < 0) {
 613                 printf("Failed to move " BASEDIR " into new root: %s.\n", strerror(errno));
 614                 return -1;
 615         }
 616
 617         return 0;
 618 }
 619
 620 /* Calls chroot() on ramfs, pivot_root() in all other cases. */
 621 static bool permute_root(void)
 622 {
 623         /* Prepare new root. */
 624         if (permute_prepare() < 0)
 625                 return false;
 626
 627         /* Pivot into new root. */
 628         if (permute_and_enter() < 0)
 629                 return false;
 630
 631         return true;
 632 }
 633
 634 static bool cgfs_prepare_mounts(void)
 635 {
 636         if (!mkdir_p(BASEDIR, 0700)) {
 637                 lxcfs_error("%s\n", "Failed to create lxcfs cgroup mountpoint.");
 638                 return false;
 639         }
 640
 641         if (!umount_if_mounted()) {
 642                 lxcfs_error("%s\n", "Failed to clean up old lxcfs cgroup mountpoint.");
 643                 return false;
 644         }
 645
 646         if (unshare(CLONE_NEWNS) < 0) {
 647                 lxcfs_error("Failed to unshare mount namespace: %s.\n", strerror(errno));
 648                 return false;
 649         }
 650
 651         cgroup_ops->mntns_fd = preserve_ns(getpid(), "mnt");
 652         if (cgroup_ops->mntns_fd < 0) {
 653                 lxcfs_error("Failed to preserve mount namespace: %s.\n", strerror(errno));
 654                 return false;
 655         }
 656
 657         if (mount(NULL, "/", NULL, MS_REC | MS_PRIVATE, 0) < 0) {
 658                 lxcfs_error("Failed to remount / private: %s.\n", strerror(errno));
 659                 return false;
 660         }
 661
 662         if (mount("tmpfs", BASEDIR, "tmpfs", 0, "size=100000,mode=700") < 0) {
 663                 lxcfs_error("%s\n", "Failed to mount tmpfs over lxcfs cgroup mountpoint.");
 664                 return false;
 665         }
 666
 667         return true;
 668 }
 669
 670 static bool cgfs_mount_hierarchies(void)
 671 {
 672         if (!mkdir_p(BASEDIR DEFAULT_CGROUP_MOUNTPOINT, 0755))
 673                 return false;
 674
 675         if (!cgroup_ops->mount(cgroup_ops, BASEDIR))
 676                 return false;
 677
 678         for (struct hierarchy **h = cgroup_ops->hierarchies; h && *h; h++) {
 679                 __do_free char *path = must_make_path(BASEDIR, (*h)->mountpoint, NULL);
 680                 (*h)->fd = open(path, O_DIRECTORY | O_CLOEXEC | O_NOFOLLOW);
 681                 if ((*h)->fd < 0)
 682                         return false;
 683         }
 684
 685         return true;
 686 }
 687
 688 static bool cgfs_setup_controllers(void)
 689 {
 690         if (!cgfs_prepare_mounts())
 691                 return false;
 692
 693         if (!cgfs_mount_hierarchies())
 694                 return log_error_errno(false, errno, "Failed to set up private lxcfs cgroup mounts");
 695
 696         if (!permute_root())
 697                 return false;
 698
 699         return true;
 700 }
 701
 702 static void __attribute__((constructor)) lxcfs_init(void)
 703 {
 704         __do_close_prot_errno int init_ns = -EBADF, pidfd = -EBADF;
 705         int i = 0;
 706         pid_t pid;
 707         char *cret;
 708         char cwd[MAXPATHLEN];
 709
 710         cgroup_ops = cgroup_init();
 711         if (!cgroup_ops)
 712                 log_exit("Failed to initialize cgroup support");
 713
 714         /* Preserve initial namespace. */
 715         pid = getpid();
 716         init_ns = preserve_ns(pid, "mnt");
 717         if (init_ns < 0)
 718                 log_exit("Failed to preserve initial mount namespace");
 719
 720         cret = getcwd(cwd, MAXPATHLEN);
 721         if (!cret)
 722                 log_exit("%s - Could not retrieve current working directory", strerror(errno));
 723
 724         /* This function calls unshare(CLONE_NEWNS) our initial mount namespace
 725          * to privately mount lxcfs cgroups. */
 726         if (!cgfs_setup_controllers())
 727                 log_exit("Failed to setup private cgroup mounts for lxcfs");
 728
 729         if (setns(init_ns, 0) < 0)
 730                 log_exit("%s - Failed to switch back to initial mount namespace", strerror(errno));
 731
 732         if (!cret || chdir(cwd) < 0)
 733                 log_exit("%s - Could not change back to original working directory", strerror(errno));
 734
 735         if (!init_cpuview())
 736                 log_exit("Failed to init CPU view");
 737
 738         fprintf(stderr, "mount namespace: %d\n", cgroup_ops->mntns_fd);
 739         fprintf(stderr, "hierarchies:\n");
 740
 741         for (struct hierarchy **h = cgroup_ops->hierarchies; h && *h; h++, i++) {
 742                 __do_free char *controllers = lxc_string_join(",", (const char **)(*h)->controllers, false);
 743                 fprintf(stderr, " %2d: fd: %3d: %s\n", i, (*h)->fd, controllers ?: "");
 744         }
 745
 746         pidfd = pidfd_open(pid, 0);
 747         if (pidfd >= 0 && pidfd_send_signal(pidfd, 0, NULL, 0) == 0) {
 748                 can_use_pidfd = true;
 749                 fprintf(stderr, "Kernel supports pidfds\n");
 750         }
 751
 752         fprintf(stderr, "api_extensions:\n");
 753         for (i = 0; i < nr_api_extensions; i++)
 754                 fprintf(stderr, "- %s\n", api_extensions[i]);
 755 }
 756
 757 static void __attribute__((destructor)) lxcfs_exit(void)
 758 {
 759         lxcfs_debug("%s\n", "Running destructor for liblxcfs");
 760         free_cpuview();
 761         cgroup_exit(cgroup_ops);
 762 }