src/login/logind-user.c

   1 /* SPDX-License-Identifier: LGPL-2.1+ */
   2 /***
   3   This file is part of systemd.
   4
   5   Copyright 2011 Lennart Poettering
   6 ***/
   7
   8 #include <errno.h>
   9 #include <string.h>
  10 #include <sys/mount.h>
  11 #include <unistd.h>
  12 #include <stdio_ext.h>
  13
  14 #include "alloc-util.h"
  15 #include "bus-common-errors.h"
  16 #include "bus-error.h"
  17 #include "bus-util.h"
  18 #include "cgroup-util.h"
  19 #include "clean-ipc.h"
  20 #include "conf-parser.h"
  21 #include "escape.h"
  22 #include "fd-util.h"
  23 #include "fileio.h"
  24 #include "format-util.h"
  25 #include "fs-util.h"
  26 #include "hashmap.h"
  27 #include "label.h"
  28 #include "logind-user.h"
  29 #include "mkdir.h"
  30 #include "mount-util.h"
  31 #include "parse-util.h"
  32 #include "path-util.h"
  33 #include "rm-rf.h"
  34 #include "smack-util.h"
  35 #include "special.h"
  36 #include "stdio-util.h"
  37 #include "string-table.h"
  38 #include "unit-name.h"
  39 #include "user-util.h"
  40 #include "util.h"
  41
  42 int user_new(User **out, Manager *m, uid_t uid, gid_t gid, const char *name) {
  43         _cleanup_(user_freep) User *u = NULL;
  44         char lu[DECIMAL_STR_MAX(uid_t) + 1];
  45         int r;
  46
  47         assert(out);
  48         assert(m);
  49         assert(name);
  50
  51         u = new0(User, 1);
  52         if (!u)
  53                 return -ENOMEM;
  54
  55         u->manager = m;
  56         u->uid = uid;
  57         u->gid = gid;
  58         xsprintf(lu, UID_FMT, uid);
  59
  60         u->name = strdup(name);
  61         if (!u->name)
  62                 return -ENOMEM;
  63
  64         if (asprintf(&u->state_file, "/run/systemd/users/"UID_FMT, uid) < 0)
  65                 return -ENOMEM;
  66
  67         if (asprintf(&u->runtime_path, "/run/user/"UID_FMT, uid) < 0)
  68                 return -ENOMEM;
  69
  70         r = slice_build_subslice(SPECIAL_USER_SLICE, lu, &u->slice);
  71         if (r < 0)
  72                 return r;
  73
  74         r = unit_name_build("user", lu, ".service", &u->service);
  75         if (r < 0)
  76                 return r;
  77
  78         r = hashmap_put(m->users, UID_TO_PTR(uid), u);
  79         if (r < 0)
  80                 return r;
  81
  82         r = hashmap_put(m->user_units, u->slice, u);
  83         if (r < 0)
  84                 return r;
  85
  86         r = hashmap_put(m->user_units, u->service, u);
  87         if (r < 0)
  88                 return r;
  89
  90         *out = TAKE_PTR(u);
  91
  92         return 0;
  93 }
  94
  95 User *user_free(User *u) {
  96         if (!u)
  97                 return NULL;
  98
  99         if (u->in_gc_queue)
 100                 LIST_REMOVE(gc_queue, u->manager->user_gc_queue, u);
 101
 102         while (u->sessions)
 103                 session_free(u->sessions);
 104
 105         if (u->service)
 106                 hashmap_remove_value(u->manager->user_units, u->service, u);
 107
 108         if (u->slice)
 109                 hashmap_remove_value(u->manager->user_units, u->slice, u);
 110
 111         hashmap_remove_value(u->manager->users, UID_TO_PTR(u->uid), u);
 112
 113 #if 0 /// elogind neither supports slice nor service jobs.
 114         u->slice_job = mfree(u->slice_job);
 115         u->service_job = mfree(u->service_job);
 116 #endif // 0
 117
 118         u->service = mfree(u->service);
 119         u->slice = mfree(u->slice);
 120         u->runtime_path = mfree(u->runtime_path);
 121         u->state_file = mfree(u->state_file);
 122         u->name = mfree(u->name);
 123
 124         return mfree(u);
 125 }
 126
 127 static int user_save_internal(User *u) {
 128         _cleanup_free_ char *temp_path = NULL;
 129         _cleanup_fclose_ FILE *f = NULL;
 130         int r;
 131
 132         assert(u);
 133         assert(u->state_file);
 134
 135         r = mkdir_safe_label("/run/systemd/users", 0755, 0, 0, MKDIR_WARN_MODE);
 136         if (r < 0)
 137                 goto fail;
 138
 139         r = fopen_temporary(u->state_file, &f, &temp_path);
 140         if (r < 0)
 141                 goto fail;
 142
 143         (void) __fsetlocking(f, FSETLOCKING_BYCALLER);
 144         (void) fchmod(fileno(f), 0644);
 145
 146         fprintf(f,
 147                 "# This is private data. Do not parse.\n"
 148                 "NAME=%s\n"
 149                 "STATE=%s\n",
 150                 u->name,
 151                 user_state_to_string(user_get_state(u)));
 152
 153         /* LEGACY: no-one reads RUNTIME= anymore, drop it at some point */
 154         if (u->runtime_path)
 155                 fprintf(f, "RUNTIME=%s\n", u->runtime_path);
 156
 157 #if 0 /// elogind neither supports service nor slice jobs
 158         if (u->service_job)
 159                 fprintf(f, "SERVICE_JOB=%s\n", u->service_job);
 160
 161         if (u->slice_job)
 162                 fprintf(f, "SLICE_JOB=%s\n", u->slice_job);
 163 #endif // 0
 164
 165         if (u->display)
 166                 fprintf(f, "DISPLAY=%s\n", u->display->id);
 167
 168         if (dual_timestamp_is_set(&u->timestamp))
 169                 fprintf(f,
 170                         "REALTIME="USEC_FMT"\n"
 171                         "MONOTONIC="USEC_FMT"\n",
 172                         u->timestamp.realtime,
 173                         u->timestamp.monotonic);
 174
 175         if (u->sessions) {
 176                 Session *i;
 177                 bool first;
 178
 179                 fputs("SESSIONS=", f);
 180                 first = true;
 181                 LIST_FOREACH(sessions_by_user, i, u->sessions) {
 182                         if (first)
 183                                 first = false;
 184                         else
 185                                 fputc(' ', f);
 186
 187                         fputs(i->id, f);
 188                 }
 189
 190                 fputs("\nSEATS=", f);
 191                 first = true;
 192                 LIST_FOREACH(sessions_by_user, i, u->sessions) {
 193                         if (!i->seat)
 194                                 continue;
 195
 196                         if (first)
 197                                 first = false;
 198                         else
 199                                 fputc(' ', f);
 200
 201                         fputs(i->seat->id, f);
 202                 }
 203
 204                 fputs("\nACTIVE_SESSIONS=", f);
 205                 first = true;
 206                 LIST_FOREACH(sessions_by_user, i, u->sessions) {
 207                         if (!session_is_active(i))
 208                                 continue;
 209
 210                         if (first)
 211                                 first = false;
 212                         else
 213                                 fputc(' ', f);
 214
 215                         fputs(i->id, f);
 216                 }
 217
 218                 fputs("\nONLINE_SESSIONS=", f);
 219                 first = true;
 220                 LIST_FOREACH(sessions_by_user, i, u->sessions) {
 221                         if (session_get_state(i) == SESSION_CLOSING)
 222                                 continue;
 223
 224                         if (first)
 225                                 first = false;
 226                         else
 227                                 fputc(' ', f);
 228
 229                         fputs(i->id, f);
 230                 }
 231
 232                 fputs("\nACTIVE_SEATS=", f);
 233                 first = true;
 234                 LIST_FOREACH(sessions_by_user, i, u->sessions) {
 235                         if (!session_is_active(i) || !i->seat)
 236                                 continue;
 237
 238                         if (first)
 239                                 first = false;
 240                         else
 241                                 fputc(' ', f);
 242
 243                         fputs(i->seat->id, f);
 244                 }
 245
 246                 fputs("\nONLINE_SEATS=", f);
 247                 first = true;
 248                 LIST_FOREACH(sessions_by_user, i, u->sessions) {
 249                         if (session_get_state(i) == SESSION_CLOSING || !i->seat)
 250                                 continue;
 251
 252                         if (first)
 253                                 first = false;
 254                         else
 255                                 fputc(' ', f);
 256
 257                         fputs(i->seat->id, f);
 258                 }
 259                 fputc('\n', f);
 260         }
 261
 262         r = fflush_and_check(f);
 263         if (r < 0)
 264                 goto fail;
 265
 266         if (rename(temp_path, u->state_file) < 0) {
 267                 r = -errno;
 268                 goto fail;
 269         }
 270
 271         return 0;
 272
 273 fail:
 274         (void) unlink(u->state_file);
 275
 276         if (temp_path)
 277                 (void) unlink(temp_path);
 278
 279         return log_error_errno(r, "Failed to save user data %s: %m", u->state_file);
 280 }
 281
 282 int user_save(User *u) {
 283         assert(u);
 284
 285         if (!u->started)
 286                 return 0;
 287
 288         return user_save_internal (u);
 289 }
 290
 291 int user_load(User *u) {
 292         _cleanup_free_ char *display = NULL, *realtime = NULL, *monotonic = NULL;
 293         Session *s = NULL;
 294         int r;
 295
 296         assert(u);
 297
 298         r = parse_env_file(u->state_file, NEWLINE,
 299 #if 0 /// elogind neither supports service nor slice jobs
 300                            "SERVICE_JOB", &u->service_job,
 301                            "SLICE_JOB",   &u->slice_job,
 302 #endif // 0
 303                            "DISPLAY",     &display,
 304                            "REALTIME",    &realtime,
 305                            "MONOTONIC",   &monotonic,
 306                            NULL);
 307         if (r < 0) {
 308                 if (r == -ENOENT)
 309                         return 0;
 310
 311                 return log_error_errno(r, "Failed to read %s: %m", u->state_file);
 312         }
 313
 314         if (display)
 315                 s = hashmap_get(u->manager->sessions, display);
 316
 317         if (s && s->display && display_is_local(s->display))
 318                 u->display = s;
 319
 320         if (realtime)
 321                 timestamp_deserialize(realtime, &u->timestamp.realtime);
 322         if (monotonic)
 323                 timestamp_deserialize(monotonic, &u->timestamp.monotonic);
 324
 325         return r;
 326 }
 327
 328 static int user_mkdir_runtime_path(User *u) {
 329         int r;
 330
 331         assert(u);
 332
 333         r = mkdir_safe_label("/run/user", 0755, 0, 0, MKDIR_WARN_MODE);
 334         if (r < 0)
 335                 return log_error_errno(r, "Failed to create /run/user: %m");
 336
 337         if (path_is_mount_point(u->runtime_path, NULL, 0) <= 0) {
 338                 _cleanup_free_ char *t = NULL;
 339
 340                 r = asprintf(&t, "mode=0700,uid=" UID_FMT ",gid=" GID_FMT ",size=%zu%s",
 341                              u->uid, u->gid, u->manager->runtime_dir_size,
 342                              mac_smack_use() ? ",smackfsroot=*" : "");
 343                 if (r < 0)
 344                         return log_oom();
 345
 346                 (void) mkdir_label(u->runtime_path, 0700);
 347
 348                 r = mount("tmpfs", u->runtime_path, "tmpfs", MS_NODEV|MS_NOSUID, t);
 349                 if (r < 0) {
 350                         if (!IN_SET(errno, EPERM, EACCES)) {
 351                                 r = log_error_errno(errno, "Failed to mount per-user tmpfs directory %s: %m", u->runtime_path);
 352                                 goto fail;
 353                         }
 354
 355                         log_debug_errno(errno, "Failed to mount per-user tmpfs directory %s, assuming containerized execution, ignoring: %m", u->runtime_path);
 356
 357                         r = chmod_and_chown(u->runtime_path, 0700, u->uid, u->gid);
 358                         if (r < 0) {
 359                                 log_error_errno(r, "Failed to change runtime directory ownership and mode: %m");
 360                                 goto fail;
 361                         }
 362                 }
 363
 364                 r = label_fix(u->runtime_path, 0);
 365                 if (r < 0)
 366                         log_warning_errno(r, "Failed to fix label of '%s', ignoring: %m", u->runtime_path);
 367         }
 368
 369         return 0;
 370
 371 fail:
 372         /* Try to clean up, but ignore errors */
 373         (void) rmdir(u->runtime_path);
 374         return r;
 375 }
 376
 377 #if 0 /// elogind can not ask systemd via dbus to start user services
 378 #else
 379         assert(u);
 380
 381         hashmap_put(u->manager->user_units, u->slice, u);
 382 #endif // 0
 383 static int user_start_service(User *u) {
 384 #if 0 /// elogind can not ask systemd via dbus to start user services
 385         _cleanup_(sd_bus_error_free) sd_bus_error error = SD_BUS_ERROR_NULL;
 386         char *job;
 387         int r;
 388
 389         assert(u);
 390
 391         u->service_job = mfree(u->service_job);
 392
 393         r = manager_start_unit(
 394                         u->manager,
 395                         u->service,
 396                         &error,
 397                         &job);
 398         if (r < 0)
 399                 /* we don't fail due to this, let's try to continue */
 400                 log_error_errno(r, "Failed to start user service, ignoring: %s", bus_error_message(&error, r));
 401         else
 402                 u->service_job = job;
 403 #else
 404         assert(u);
 405
 406         hashmap_put(u->manager->user_units, u->service, u);
 407 #endif // 0
 408
 409         return 0;
 410 }
 411
 412 int user_start(User *u) {
 413         int r;
 414
 415         assert(u);
 416
 417         if (u->started && !u->stopping)
 418                 return 0;
 419
 420         /*
 421          * If u->stopping is set, the user is marked for removal and the slice
 422          * and service stop-jobs are queued. We have to clear that flag before
 423          * queing the start-jobs again. If they succeed, the user object can be
 424          * re-used just fine (pid1 takes care of job-ordering and proper
 425          * restart), but if they fail, we want to force another user_stop() so
 426          * possibly pending units are stopped.
 427          * Note that we don't clear u->started, as we have no clue what state
 428          * the user is in on failure here. Hence, we pretend the user is
 429          * running so it will be properly taken down by GC. However, we clearly
 430          * return an error from user_start() in that case, so no further
 431          * reference to the user is taken.
 432          */
 433         u->stopping = false;
 434
 435         if (!u->started) {
 436                 log_debug("Starting services for new user %s.", u->name);
 437
 438                 /* Make XDG_RUNTIME_DIR */
 439                 r = user_mkdir_runtime_path(u);
 440                 if (r < 0)
 441                         return r;
 442         }
 443
 444         /* Save the user data so far, because pam_systemd will read the
 445          * XDG_RUNTIME_DIR out of it while starting up systemd --user.
 446          * We need to do user_save_internal() because we have not
 447          * "officially" started yet. */
 448         user_save_internal(u);
 449
 450         /* Spawn user systemd */
 451         r = user_start_service(u);
 452         if (r < 0)
 453                 return r;
 454
 455         if (!u->started) {
 456                 if (!dual_timestamp_is_set(&u->timestamp))
 457                         dual_timestamp_get(&u->timestamp);
 458                 user_send_signal(u, true);
 459                 u->started = true;
 460         }
 461
 462         /* Save new user data */
 463         user_save(u);
 464
 465         return 0;
 466 }
 467
 468 #if 0 /// UNNEEDED by elogind
 469 static int user_stop_slice(User *u) {
 470         _cleanup_(sd_bus_error_free) sd_bus_error error = SD_BUS_ERROR_NULL;
 471         char *job;
 472         int r;
 473
 474         assert(u);
 475
 476         r = manager_stop_unit(u->manager, u->slice, &error, &job);
 477         if (r < 0) {
 478                 log_error("Failed to stop user slice: %s", bus_error_message(&error, r));
 479                 return r;
 480         }
 481
 482         free(u->slice_job);
 483         u->slice_job = job;
 484
 485         return r;
 486 }
 487
 488 static int user_stop_service(User *u) {
 489         _cleanup_(sd_bus_error_free) sd_bus_error error = SD_BUS_ERROR_NULL;
 490         char *job;
 491         int r;
 492
 493         assert(u);
 494
 495         r = manager_stop_unit(u->manager, u->service, &error, &job);
 496         if (r < 0) {
 497                 log_error("Failed to stop user service: %s", bus_error_message(&error, r));
 498                 return r;
 499         }
 500
 501         free_and_replace(u->service_job, job);
 502         return r;
 503 }
 504 #endif // 0
 505
 506 static int user_remove_runtime_path(User *u) {
 507         int r;
 508
 509         assert(u);
 510
 511         r = rm_rf(u->runtime_path, 0);
 512         if (r < 0)
 513                 log_error_errno(r, "Failed to remove runtime directory %s (before unmounting): %m", u->runtime_path);
 514
 515         /* Ignore cases where the directory isn't mounted, as that's
 516          * quite possible, if we lacked the permissions to mount
 517          * something */
 518         r = umount2(u->runtime_path, MNT_DETACH);
 519         if (r < 0 && !IN_SET(errno, EINVAL, ENOENT))
 520                 log_error_errno(errno, "Failed to unmount user runtime directory %s: %m", u->runtime_path);
 521
 522         r = rm_rf(u->runtime_path, REMOVE_ROOT);
 523         if (r < 0)
 524                 log_error_errno(r, "Failed to remove runtime directory %s (after unmounting): %m", u->runtime_path);
 525
 526         return r;
 527 }
 528
 529 int user_stop(User *u, bool force) {
 530         Session *s;
 531         int r = 0, k;
 532         assert(u);
 533
 534         /* Stop jobs have already been queued */
 535         if (u->stopping) {
 536                 user_save(u);
 537                 return r;
 538         }
 539
 540         LIST_FOREACH(sessions_by_user, s, u->sessions) {
 541                 k = session_stop(s, force);
 542                 if (k < 0)
 543                         r = k;
 544         }
 545
 546         /* Kill systemd */
 547 #if 0 /// elogind does not support service or slice jobs
 548         k = user_stop_service(u);
 549         if (k < 0)
 550                 r = k;
 551
 552         /* Kill cgroup */
 553         k = user_stop_slice(u);
 554         if (k < 0)
 555                 r = k;
 556 #endif // 0
 557
 558         u->stopping = true;
 559
 560         user_save(u);
 561
 562 #if 1 /// elogind must queue this user again
 563         user_add_to_gc_queue(u);
 564 #endif // 1
 565         return r;
 566 }
 567
 568 int user_finalize(User *u) {
 569         Session *s;
 570         int r = 0, k;
 571
 572         assert(u);
 573
 574         if (u->started)
 575                 log_debug("User %s logged out.", u->name);
 576
 577         LIST_FOREACH(sessions_by_user, s, u->sessions) {
 578                 k = session_finalize(s);
 579                 if (k < 0)
 580                         r = k;
 581         }
 582
 583         /* Kill XDG_RUNTIME_DIR */
 584         k = user_remove_runtime_path(u);
 585         if (k < 0)
 586                 r = k;
 587
 588         /* Clean SysV + POSIX IPC objects, but only if this is not a system user. Background: in many setups cronjobs
 589          * are run in full PAM and thus logind sessions, even if the code run doesn't belong to actual users but to
 590          * system components. Since enable RemoveIPC= globally for all users, we need to be a bit careful with such
 591          * cases, as we shouldn't accidentally remove a system service's IPC objects while it is running, just because
 592          * a cronjob running as the same user just finished. Hence: exclude system users generally from IPC clean-up,
 593          * and do it only for normal users. */
 594         if (u->manager->remove_ipc && !uid_is_system(u->uid)) {
 595                 k = clean_ipc_by_uid(u->uid);
 596                 if (k < 0)
 597                         r = k;
 598         }
 599
 600         unlink(u->state_file);
 601         user_add_to_gc_queue(u);
 602
 603         if (u->started) {
 604                 user_send_signal(u, false);
 605                 u->started = false;
 606         }
 607
 608         return r;
 609 }
 610
 611 int user_get_idle_hint(User *u, dual_timestamp *t) {
 612         Session *s;
 613         bool idle_hint = true;
 614         dual_timestamp ts = DUAL_TIMESTAMP_NULL;
 615
 616         assert(u);
 617
 618         LIST_FOREACH(sessions_by_user, s, u->sessions) {
 619                 dual_timestamp k;
 620                 int ih;
 621
 622                 ih = session_get_idle_hint(s, &k);
 623                 if (ih < 0)
 624                         return ih;
 625
 626                 if (!ih) {
 627                         if (!idle_hint) {
 628                                 if (k.monotonic < ts.monotonic)
 629                                         ts = k;
 630                         } else {
 631                                 idle_hint = false;
 632                                 ts = k;
 633                         }
 634                 } else if (idle_hint) {
 635
 636                         if (k.monotonic > ts.monotonic)
 637                                 ts = k;
 638                 }
 639         }
 640
 641         if (t)
 642                 *t = ts;
 643
 644         return idle_hint;
 645 }
 646
 647 int user_check_linger_file(User *u) {
 648         _cleanup_free_ char *cc = NULL;
 649         char *p = NULL;
 650
 651         cc = cescape(u->name);
 652         if (!cc)
 653                 return -ENOMEM;
 654
 655         p = strjoina("/var/lib/elogind/linger/", cc);
 656
 657         return access(p, F_OK) >= 0;
 658 }
 659
 660 bool user_may_gc(User *u, bool drop_not_started) {
 661         assert(u);
 662
 663         if (drop_not_started && !u->started)
 664                 return true;
 665
 666         if (u->sessions)
 667                 return false;
 668
 669         if (user_check_linger_file(u) > 0)
 670                 return false;
 671
 672 #if 0 /// elogind neither supports service nor slice jobs
 673         if (u->slice_job && manager_job_is_active(u->manager, u->slice_job))
 674                 return false;
 675
 676         if (u->service_job && manager_job_is_active(u->manager, u->service_job))
 677                 return false;
 678 #endif // 0
 679
 680         return true;
 681 }
 682
 683 void user_add_to_gc_queue(User *u) {
 684         assert(u);
 685
 686         if (u->in_gc_queue)
 687                 return;
 688
 689         LIST_PREPEND(gc_queue, u->manager->user_gc_queue, u);
 690         u->in_gc_queue = true;
 691 }
 692
 693 UserState user_get_state(User *u) {
 694         Session *i;
 695
 696         assert(u);
 697
 698         if (u->stopping)
 699                 return USER_CLOSING;
 700
 701 #if 0 /// elogind neither supports service nor slice jobs.
 702         if (!u->started || u->slice_job || u->service_job)
 703 #else
 704         if (!u->started)
 705 #endif // 0
 706                 return USER_OPENING;
 707
 708         if (u->sessions) {
 709                 bool all_closing = true;
 710
 711                 LIST_FOREACH(sessions_by_user, i, u->sessions) {
 712                         SessionState state;
 713
 714                         state = session_get_state(i);
 715                         if (state == SESSION_ACTIVE)
 716                                 return USER_ACTIVE;
 717                         if (state != SESSION_CLOSING)
 718                                 all_closing = false;
 719                 }
 720
 721                 return all_closing ? USER_CLOSING : USER_ONLINE;
 722         }
 723
 724         if (user_check_linger_file(u) > 0)
 725                 return USER_LINGERING;
 726
 727         return USER_CLOSING;
 728 }
 729
 730 int user_kill(User *u, int signo) {
 731 #if 0 /// Without systemd unit support, elogind has to rely on its session system
 732         assert(u);
 733
 734         return manager_kill_unit(u->manager, u->slice, KILL_ALL, signo, NULL);
 735 #else
 736         Session *s;
 737         int res = 0;
 738
 739         assert(u);
 740
 741         LIST_FOREACH(sessions_by_user, s, u->sessions) {
 742                 int r = session_kill(s, KILL_ALL, signo);
 743                 if (res == 0 && r < 0)
 744                         res = r;
 745         }
 746
 747         return res;
 748 #endif // 0
 749 }
 750
 751 static bool elect_display_filter(Session *s) {
 752         /* Return true if the session is a candidate for the user’s ‘primary
 753          * session’ or ‘display’. */
 754         assert(s);
 755
 756         return (s->class == SESSION_USER && !s->stopping);
 757 }
 758
 759 static int elect_display_compare(Session *s1, Session *s2) {
 760         /* Indexed by SessionType. Lower numbers mean more preferred. */
 761         const int type_ranks[_SESSION_TYPE_MAX] = {
 762                 [SESSION_UNSPECIFIED] = 0,
 763                 [SESSION_TTY] = -2,
 764                 [SESSION_X11] = -3,
 765                 [SESSION_WAYLAND] = -3,
 766                 [SESSION_MIR] = -3,
 767                 [SESSION_WEB] = -1,
 768         };
 769
 770         /* Calculate the partial order relationship between s1 and s2,
 771          * returning < 0 if s1 is preferred as the user’s ‘primary session’,
 772          * 0 if s1 and s2 are equally preferred or incomparable, or > 0 if s2
 773          * is preferred.
 774          *
 775          * s1 or s2 may be NULL. */
 776         if (!s1 && !s2)
 777                 return 0;
 778
 779         if ((s1 == NULL) != (s2 == NULL))
 780                 return (s1 == NULL) - (s2 == NULL);
 781
 782         if (s1->stopping != s2->stopping)
 783                 return s1->stopping - s2->stopping;
 784
 785         if ((s1->class != SESSION_USER) != (s2->class != SESSION_USER))
 786                 return (s1->class != SESSION_USER) - (s2->class != SESSION_USER);
 787
 788         if ((s1->type == _SESSION_TYPE_INVALID) != (s2->type == _SESSION_TYPE_INVALID))
 789                 return (s1->type == _SESSION_TYPE_INVALID) - (s2->type == _SESSION_TYPE_INVALID);
 790
 791         if (s1->type != s2->type)
 792                 return type_ranks[s1->type] - type_ranks[s2->type];
 793
 794         return 0;
 795 }
 796
 797 void user_elect_display(User *u) {
 798         Session *s;
 799
 800         assert(u);
 801
 802         /* This elects a primary session for each user, which we call
 803          * the "display". We try to keep the assignment stable, but we
 804          * "upgrade" to better choices. */
 805         log_debug("Electing new display for user %s", u->name);
 806
 807         LIST_FOREACH(sessions_by_user, s, u->sessions) {
 808                 if (!elect_display_filter(s)) {
 809                         log_debug("Ignoring session %s", s->id);
 810                         continue;
 811                 }
 812
 813                 if (elect_display_compare(s, u->display) < 0) {
 814                         log_debug("Choosing session %s in preference to %s", s->id, u->display ? u->display->id : "-");
 815                         u->display = s;
 816                 }
 817         }
 818 }
 819
 820 static const char* const user_state_table[_USER_STATE_MAX] = {
 821         [USER_OFFLINE] = "offline",
 822         [USER_OPENING] = "opening",
 823         [USER_LINGERING] = "lingering",
 824         [USER_ONLINE] = "online",
 825         [USER_ACTIVE] = "active",
 826         [USER_CLOSING] = "closing"
 827 };
 828
 829 DEFINE_STRING_TABLE_LOOKUP(user_state, UserState);
 830
 831 int config_parse_tmpfs_size(
 832                 const char* unit,
 833                 const char *filename,
 834                 unsigned line,
 835                 const char *section,
 836                 unsigned section_line,
 837                 const char *lvalue,
 838                 int ltype,
 839                 const char *rvalue,
 840                 void *data,
 841                 void *userdata) {
 842
 843         size_t *sz = data;
 844         int r;
 845
 846         assert(filename);
 847         assert(lvalue);
 848         assert(rvalue);
 849         assert(data);
 850
 851         /* First, try to parse as percentage */
 852         r = parse_percent(rvalue);
 853         if (r > 0 && r < 100)
 854                 *sz = physical_memory_scale(r, 100U);
 855         else {
 856                 uint64_t k;
 857
 858                 /* If the passed argument was not a percentage, or out of range, parse as byte size */
 859
 860                 r = parse_size(rvalue, 1024, &k);
 861                 if (r < 0 || k <= 0 || (uint64_t) (size_t) k != k) {
 862                         log_syntax(unit, LOG_ERR, filename, line, r, "Failed to parse size value, ignoring: %s", rvalue);
 863                         return 0;
 864                 }
 865
 866                 *sz = PAGE_ALIGN((size_t) k);
 867         }
 868
 869         return 0;
 870 }
 871
 872 int config_parse_compat_user_tasks_max(
 873                 const char *unit,
 874                 const char *filename,
 875                 unsigned line,
 876                 const char *section,
 877                 unsigned section_line,
 878                 const char *lvalue,
 879                 int ltype,
 880                 const char *rvalue,
 881                 void *data,
 882                 void *userdata) {
 883
 884         assert(filename);
 885         assert(lvalue);
 886         assert(rvalue);
 887         assert(data);
 888
 889         log_syntax(unit, LOG_NOTICE, filename, line, 0,
 890                    "Support for option %s= has been removed.",
 891                    lvalue);
 892         log_info("Hint: try creating /etc/elogind/system/user-.slice/50-limits.conf with:\n"
 893                  "        [Slice]\n"
 894                  "        TasksMax=%s",
 895                  rvalue);
 896         return 0;
 897 }