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