src/login/logind-user.c

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