fs/proc/array.c

   1 /*
   2  *  linux/fs/proc/array.c
   3  *
   4  *  Copyright (C) 1992  by Linus Torvalds
   5  *  based on ideas by Darren Senn
   6  *
   7  * Fixes:
   8  * Michael. K. Johnson: stat,statm extensions.
   9  *                      <johnsonm@stolaf.edu>
  10  *
  11  * Pauline Middelink :  Made cmdline,envline only break at '\0's, to
  12  *                      make sure SET_PROCTITLE works. Also removed
  13  *                      bad '!' which forced address recalculation for
  14  *                      EVERY character on the current page.
  15  *                      <middelin@polyware.iaf.nl>
  16  *
  17  * Danny ter Haar    :  added cpuinfo
  18  *                      <dth@cistron.nl>
  19  *
  20  * Alessandro Rubini :  profile extension.
  21  *                      <rubini@ipvvis.unipv.it>
  22  *
  23  * Jeff Tranter      :  added BogoMips field to cpuinfo
  24  *                      <Jeff_Tranter@Mitel.COM>
  25  *
  26  * Bruno Haible      :  remove 4K limit for the maps file
  27  *                      <haible@ma2s2.mathematik.uni-karlsruhe.de>
  28  *
  29  * Yves Arrouye      :  remove removal of trailing spaces in get_array.
  30  *                      <Yves.Arrouye@marin.fdn.fr>
  31  *
  32  * Jerome Forissier  :  added per-CPU time information to /proc/stat
  33  *                      and /proc/<pid>/cpu extension
  34  *                      <forissier@isia.cma.fr>
  35  *                      - Incorporation and non-SMP safe operation
  36  *                      of forissier patch in 2.1.78 by
  37  *                      Hans Marcus <crowbar@concepts.nl>
  38  *
  39  * aeb@cwi.nl        :  /proc/partitions
  40  *
  41  *
  42  * Alan Cox          :  security fixes.
  43  *                      <alan@lxorguk.ukuu.org.uk>
  44  *
  45  * Al Viro           :  safe handling of mm_struct
  46  *
  47  * Gerhard Wichert   :  added BIGMEM support
  48  * Siemens AG           <Gerhard.Wichert@pdb.siemens.de>
  49  *
  50  * Al Viro & Jeff Garzik :  moved most of the thing into base.c and
  51  *                       :  proc_misc.c. The rest may eventually go into
  52  *                       :  base.c too.
  53  */
  54
  55 #include <linux/types.h>
  56 #include <linux/errno.h>
  57 #include <linux/time.h>
  58 #include <linux/kernel.h>
  59 #include <linux/kernel_stat.h>
  60 #include <linux/tty.h>
  61 #include <linux/string.h>
  62 #include <linux/mman.h>
  63 #include <linux/proc_fs.h>
  64 #include <linux/ioport.h>
  65 #include <linux/uaccess.h>
  66 #include <linux/io.h>
  67 #include <linux/mm.h>
  68 #include <linux/hugetlb.h>
  69 #include <linux/pagemap.h>
  70 #include <linux/swap.h>
  71 #include <linux/smp.h>
  72 #include <linux/signal.h>
  73 #include <linux/highmem.h>
  74 #include <linux/file.h>
  75 #include <linux/fdtable.h>
  76 #include <linux/times.h>
  77 #include <linux/cpuset.h>
  78 #include <linux/rcupdate.h>
  79 #include <linux/delayacct.h>
  80 #include <linux/seq_file.h>
  81 #include <linux/pid_namespace.h>
  82 #include <linux/ptrace.h>
  83 #include <linux/tracehook.h>
  84 #include <linux/user_namespace.h>
  85
  86 #include <asm/pgtable.h>
  87 #include <asm/processor.h>
  88 #include "internal.h"
  89
  90 static inline void task_name(struct seq_file *m, struct task_struct *p)
  91 {
  92         int i;
  93         char *buf, *end;
  94         char *name;
  95         char tcomm[sizeof(p->comm)];
  96
  97         get_task_comm(tcomm, p);
  98
  99         seq_puts(m, "Name:\t");
 100         end = m->buf + m->size;
 101         buf = m->buf + m->count;
 102         name = tcomm;
 103         i = sizeof(tcomm);
 104         while (i && (buf < end)) {
 105                 unsigned char c = *name;
 106                 name++;
 107                 i--;
 108                 *buf = c;
 109                 if (!c)
 110                         break;
 111                 if (c == '\\') {
 112                         buf++;
 113                         if (buf < end)
 114                                 *buf++ = c;
 115                         continue;
 116                 }
 117                 if (c == '\n') {
 118                         *buf++ = '\\';
 119                         if (buf < end)
 120                                 *buf++ = 'n';
 121                         continue;
 122                 }
 123                 buf++;
 124         }
 125         m->count = buf - m->buf;
 126         seq_putc(m, '\n');
 127 }
 128
 129 /*
 130  * The task state array is a strange "bitmap" of
 131  * reasons to sleep. Thus "running" is zero, and
 132  * you can test for combinations of others with
 133  * simple bit tests.
 134  */
 135 static const char * const task_state_array[] = {
 136         "R (running)",          /*   0 */
 137         "S (sleeping)",         /*   1 */
 138         "D (disk sleep)",       /*   2 */
 139         "T (stopped)",          /*   4 */
 140         "t (tracing stop)",     /*   8 */
 141         "Z (zombie)",           /*  16 */
 142         "X (dead)",             /*  32 */
 143 };
 144
 145 static inline const char *get_task_state(struct task_struct *tsk)
 146 {
 147         unsigned int state = (tsk->state | tsk->exit_state) & TASK_REPORT;
 148
 149         BUILD_BUG_ON(1 + ilog2(TASK_REPORT) != ARRAY_SIZE(task_state_array)-1);
 150
 151         return task_state_array[fls(state)];
 152 }
 153
 154 static inline void task_state(struct seq_file *m, struct pid_namespace *ns,
 155                                 struct pid *pid, struct task_struct *p)
 156 {
 157         struct user_namespace *user_ns = seq_user_ns(m);
 158         struct group_info *group_info;
 159         int g;
 160         struct fdtable *fdt = NULL;
 161         const struct cred *cred;
 162         pid_t ppid, tpid;
 163
 164         rcu_read_lock();
 165         ppid = pid_alive(p) ?
 166                 task_tgid_nr_ns(rcu_dereference(p->real_parent), ns) : 0;
 167         tpid = 0;
 168         if (pid_alive(p)) {
 169                 struct task_struct *tracer = ptrace_parent(p);
 170                 if (tracer)
 171                         tpid = task_pid_nr_ns(tracer, ns);
 172         }
 173         cred = get_task_cred(p);
 174         seq_printf(m,
 175                 "State:\t%s\n"
 176                 "Tgid:\t%d\n"
 177                 "Ngid:\t%d\n"
 178                 "Pid:\t%d\n"
 179                 "PPid:\t%d\n"
 180                 "TracerPid:\t%d\n"
 181                 "Uid:\t%d\t%d\t%d\t%d\n"
 182                 "Gid:\t%d\t%d\t%d\t%d\n",
 183                 get_task_state(p),
 184                 task_tgid_nr_ns(p, ns),
 185                 task_numa_group_id(p),
 186                 pid_nr_ns(pid, ns),
 187                 ppid, tpid,
 188                 from_kuid_munged(user_ns, cred->uid),
 189                 from_kuid_munged(user_ns, cred->euid),
 190                 from_kuid_munged(user_ns, cred->suid),
 191                 from_kuid_munged(user_ns, cred->fsuid),
 192                 from_kgid_munged(user_ns, cred->gid),
 193                 from_kgid_munged(user_ns, cred->egid),
 194                 from_kgid_munged(user_ns, cred->sgid),
 195                 from_kgid_munged(user_ns, cred->fsgid));
 196
 197         task_lock(p);
 198         if (p->files)
 199                 fdt = files_fdtable(p->files);
 200         seq_printf(m,
 201                 "FDSize:\t%d\n"
 202                 "Groups:\t",
 203                 fdt ? fdt->max_fds : 0);
 204         rcu_read_unlock();
 205
 206         group_info = cred->group_info;
 207         task_unlock(p);
 208
 209         for (g = 0; g < group_info->ngroups; g++)
 210                 seq_printf(m, "%d ",
 211                            from_kgid_munged(user_ns, GROUP_AT(group_info, g)));
 212         put_cred(cred);
 213
 214         seq_putc(m, '\n');
 215 }
 216
 217 void render_sigset_t(struct seq_file *m, const char *header,
 218                                 sigset_t *set)
 219 {
 220         int i;
 221
 222         seq_puts(m, header);
 223
 224         i = _NSIG;
 225         do {
 226                 int x = 0;
 227
 228                 i -= 4;
 229                 if (sigismember(set, i+1)) x |= 1;
 230                 if (sigismember(set, i+2)) x |= 2;
 231                 if (sigismember(set, i+3)) x |= 4;
 232                 if (sigismember(set, i+4)) x |= 8;
 233                 seq_printf(m, "%x", x);
 234         } while (i >= 4);
 235
 236         seq_putc(m, '\n');
 237 }
 238
 239 static void collect_sigign_sigcatch(struct task_struct *p, sigset_t *ign,
 240                                     sigset_t *catch)
 241 {
 242         struct k_sigaction *k;
 243         int i;
 244
 245         k = p->sighand->action;
 246         for (i = 1; i <= _NSIG; ++i, ++k) {
 247                 if (k->sa.sa_handler == SIG_IGN)
 248                         sigaddset(ign, i);
 249                 else if (k->sa.sa_handler != SIG_DFL)
 250                         sigaddset(catch, i);
 251         }
 252 }
 253
 254 static inline void task_sig(struct seq_file *m, struct task_struct *p)
 255 {
 256         unsigned long flags;
 257         sigset_t pending, shpending, blocked, ignored, caught;
 258         int num_threads = 0;
 259         unsigned long qsize = 0;
 260         unsigned long qlim = 0;
 261
 262         sigemptyset(&pending);
 263         sigemptyset(&shpending);
 264         sigemptyset(&blocked);
 265         sigemptyset(&ignored);
 266         sigemptyset(&caught);
 267
 268         if (lock_task_sighand(p, &flags)) {
 269                 pending = p->pending.signal;
 270                 shpending = p->signal->shared_pending.signal;
 271                 blocked = p->blocked;
 272                 collect_sigign_sigcatch(p, &ignored, &caught);
 273                 num_threads = get_nr_threads(p);
 274                 rcu_read_lock();  /* FIXME: is this correct? */
 275                 qsize = atomic_read(&__task_cred(p)->user->sigpending);
 276                 rcu_read_unlock();
 277                 qlim = task_rlimit(p, RLIMIT_SIGPENDING);
 278                 unlock_task_sighand(p, &flags);
 279         }
 280
 281         seq_printf(m, "Threads:\t%d\n", num_threads);
 282         seq_printf(m, "SigQ:\t%lu/%lu\n", qsize, qlim);
 283
 284         /* render them all */
 285         render_sigset_t(m, "SigPnd:\t", &pending);
 286         render_sigset_t(m, "ShdPnd:\t", &shpending);
 287         render_sigset_t(m, "SigBlk:\t", &blocked);
 288         render_sigset_t(m, "SigIgn:\t", &ignored);
 289         render_sigset_t(m, "SigCgt:\t", &caught);
 290 }
 291
 292 static void render_cap_t(struct seq_file *m, const char *header,
 293                         kernel_cap_t *a)
 294 {
 295         unsigned __capi;
 296
 297         seq_puts(m, header);
 298         CAP_FOR_EACH_U32(__capi) {
 299                 seq_printf(m, "%08x",
 300                            a->cap[(_KERNEL_CAPABILITY_U32S-1) - __capi]);
 301         }
 302         seq_putc(m, '\n');
 303 }
 304
 305 /* Remove non-existent capabilities */
 306 #define NORM_CAPS(v) (v.cap[CAP_TO_INDEX(CAP_LAST_CAP)] &= \
 307                                 CAP_TO_MASK(CAP_LAST_CAP + 1) - 1)
 308
 309 static inline void task_cap(struct seq_file *m, struct task_struct *p)
 310 {
 311         const struct cred *cred;
 312         kernel_cap_t cap_inheritable, cap_permitted, cap_effective, cap_bset;
 313
 314         rcu_read_lock();
 315         cred = __task_cred(p);
 316         cap_inheritable = cred->cap_inheritable;
 317         cap_permitted   = cred->cap_permitted;
 318         cap_effective   = cred->cap_effective;
 319         cap_bset        = cred->cap_bset;
 320         rcu_read_unlock();
 321
 322         NORM_CAPS(cap_inheritable);
 323         NORM_CAPS(cap_permitted);
 324         NORM_CAPS(cap_effective);
 325         NORM_CAPS(cap_bset);
 326
 327         render_cap_t(m, "CapInh:\t", &cap_inheritable);
 328         render_cap_t(m, "CapPrm:\t", &cap_permitted);
 329         render_cap_t(m, "CapEff:\t", &cap_effective);
 330         render_cap_t(m, "CapBnd:\t", &cap_bset);
 331 }
 332
 333 static inline void task_seccomp(struct seq_file *m, struct task_struct *p)
 334 {
 335 #ifdef CONFIG_SECCOMP
 336         seq_printf(m, "Seccomp:\t%d\n", p->seccomp.mode);
 337 #endif
 338 }
 339
 340 static inline void task_context_switch_counts(struct seq_file *m,
 341                                                 struct task_struct *p)
 342 {
 343         seq_printf(m,   "voluntary_ctxt_switches:\t%lu\n"
 344                         "nonvoluntary_ctxt_switches:\t%lu\n",
 345                         p->nvcsw,
 346                         p->nivcsw);
 347 }
 348
 349 static void task_cpus_allowed(struct seq_file *m, struct task_struct *task)
 350 {
 351         seq_puts(m, "Cpus_allowed:\t");
 352         seq_cpumask(m, &task->cpus_allowed);
 353         seq_putc(m, '\n');
 354         seq_puts(m, "Cpus_allowed_list:\t");
 355         seq_cpumask_list(m, &task->cpus_allowed);
 356         seq_putc(m, '\n');
 357 }
 358
 359 int proc_pid_status(struct seq_file *m, struct pid_namespace *ns,
 360                         struct pid *pid, struct task_struct *task)
 361 {
 362         struct mm_struct *mm = get_task_mm(task);
 363
 364         task_name(m, task);
 365         task_state(m, ns, pid, task);
 366
 367         if (mm) {
 368                 task_mem(m, mm);
 369                 mmput(mm);
 370         }
 371         task_sig(m, task);
 372         task_cap(m, task);
 373         task_seccomp(m, task);
 374         task_cpus_allowed(m, task);
 375         cpuset_task_status_allowed(m, task);
 376         task_context_switch_counts(m, task);
 377         return 0;
 378 }
 379
 380 static int do_task_stat(struct seq_file *m, struct pid_namespace *ns,
 381                         struct pid *pid, struct task_struct *task, int whole)
 382 {
 383         unsigned long vsize, eip, esp, wchan = ~0UL;
 384         int priority, nice;
 385         int tty_pgrp = -1, tty_nr = 0;
 386         sigset_t sigign, sigcatch;
 387         char state;
 388         pid_t ppid = 0, pgid = -1, sid = -1;
 389         int num_threads = 0;
 390         int permitted;
 391         struct mm_struct *mm;
 392         unsigned long long start_time;
 393         unsigned long cmin_flt = 0, cmaj_flt = 0;
 394         unsigned long  min_flt = 0,  maj_flt = 0;
 395         cputime_t cutime, cstime, utime, stime;
 396         cputime_t cgtime, gtime;
 397         unsigned long rsslim = 0;
 398         char tcomm[sizeof(task->comm)];
 399         unsigned long flags;
 400
 401         state = *get_task_state(task);
 402         vsize = eip = esp = 0;
 403         permitted = ptrace_may_access(task, PTRACE_MODE_READ | PTRACE_MODE_NOAUDIT);
 404         mm = get_task_mm(task);
 405         if (mm) {
 406                 vsize = task_vsize(mm);
 407                 if (permitted) {
 408                         eip = KSTK_EIP(task);
 409                         esp = KSTK_ESP(task);
 410                 }
 411         }
 412
 413         get_task_comm(tcomm, task);
 414
 415         sigemptyset(&sigign);
 416         sigemptyset(&sigcatch);
 417         cutime = cstime = utime = stime = 0;
 418         cgtime = gtime = 0;
 419
 420         if (lock_task_sighand(task, &flags)) {
 421                 struct signal_struct *sig = task->signal;
 422
 423                 if (sig->tty) {
 424                         struct pid *pgrp = tty_get_pgrp(sig->tty);
 425                         tty_pgrp = pid_nr_ns(pgrp, ns);
 426                         put_pid(pgrp);
 427                         tty_nr = new_encode_dev(tty_devnum(sig->tty));
 428                 }
 429
 430                 num_threads = get_nr_threads(task);
 431                 collect_sigign_sigcatch(task, &sigign, &sigcatch);
 432
 433                 cmin_flt = sig->cmin_flt;
 434                 cmaj_flt = sig->cmaj_flt;
 435                 cutime = sig->cutime;
 436                 cstime = sig->cstime;
 437                 cgtime = sig->cgtime;
 438                 rsslim = ACCESS_ONCE(sig->rlim[RLIMIT_RSS].rlim_cur);
 439
 440                 /* add up live thread stats at the group level */
 441                 if (whole) {
 442                         struct task_struct *t = task;
 443                         do {
 444                                 min_flt += t->min_flt;
 445                                 maj_flt += t->maj_flt;
 446                                 gtime += task_gtime(t);
 447                         } while_each_thread(task, t);
 448
 449                         min_flt += sig->min_flt;
 450                         maj_flt += sig->maj_flt;
 451                         thread_group_cputime_adjusted(task, &utime, &stime);
 452                         gtime += sig->gtime;
 453                 }
 454
 455                 sid = task_session_nr_ns(task, ns);
 456                 ppid = task_tgid_nr_ns(task->real_parent, ns);
 457                 pgid = task_pgrp_nr_ns(task, ns);
 458
 459                 unlock_task_sighand(task, &flags);
 460         }
 461
 462         if (permitted && (!whole || num_threads < 2))
 463                 wchan = get_wchan(task);
 464         if (!whole) {
 465                 min_flt = task->min_flt;
 466                 maj_flt = task->maj_flt;
 467                 task_cputime_adjusted(task, &utime, &stime);
 468                 gtime = task_gtime(task);
 469         }
 470
 471         /* scale priority and nice values from timeslices to -20..20 */
 472         /* to make it look like a "normal" Unix priority/nice value  */
 473         priority = task_prio(task);
 474         nice = task_nice(task);
 475
 476         /* Temporary variable needed for gcc-2.96 */
 477         /* convert timespec -> nsec*/
 478         start_time =
 479                 (unsigned long long)task->real_start_time.tv_sec * NSEC_PER_SEC
 480                                 + task->real_start_time.tv_nsec;
 481         /* convert nsec -> ticks */
 482         start_time = nsec_to_clock_t(start_time);
 483
 484         seq_printf(m, "%d (%s) %c", pid_nr_ns(pid, ns), tcomm, state);
 485         seq_put_decimal_ll(m, ' ', ppid);
 486         seq_put_decimal_ll(m, ' ', pgid);
 487         seq_put_decimal_ll(m, ' ', sid);
 488         seq_put_decimal_ll(m, ' ', tty_nr);
 489         seq_put_decimal_ll(m, ' ', tty_pgrp);
 490         seq_put_decimal_ull(m, ' ', task->flags);
 491         seq_put_decimal_ull(m, ' ', min_flt);
 492         seq_put_decimal_ull(m, ' ', cmin_flt);
 493         seq_put_decimal_ull(m, ' ', maj_flt);
 494         seq_put_decimal_ull(m, ' ', cmaj_flt);
 495         seq_put_decimal_ull(m, ' ', cputime_to_clock_t(utime));
 496         seq_put_decimal_ull(m, ' ', cputime_to_clock_t(stime));
 497         seq_put_decimal_ll(m, ' ', cputime_to_clock_t(cutime));
 498         seq_put_decimal_ll(m, ' ', cputime_to_clock_t(cstime));
 499         seq_put_decimal_ll(m, ' ', priority);
 500         seq_put_decimal_ll(m, ' ', nice);
 501         seq_put_decimal_ll(m, ' ', num_threads);
 502         seq_put_decimal_ull(m, ' ', 0);
 503         seq_put_decimal_ull(m, ' ', start_time);
 504         seq_put_decimal_ull(m, ' ', vsize);
 505         seq_put_decimal_ull(m, ' ', mm ? get_mm_rss(mm) : 0);
 506         seq_put_decimal_ull(m, ' ', rsslim);
 507         seq_put_decimal_ull(m, ' ', mm ? (permitted ? mm->start_code : 1) : 0);
 508         seq_put_decimal_ull(m, ' ', mm ? (permitted ? mm->end_code : 1) : 0);
 509         seq_put_decimal_ull(m, ' ', (permitted && mm) ? mm->start_stack : 0);
 510         seq_put_decimal_ull(m, ' ', esp);
 511         seq_put_decimal_ull(m, ' ', eip);
 512         /* The signal information here is obsolete.
 513          * It must be decimal for Linux 2.0 compatibility.
 514          * Use /proc/#/status for real-time signals.
 515          */
 516         seq_put_decimal_ull(m, ' ', task->pending.signal.sig[0] & 0x7fffffffUL);
 517         seq_put_decimal_ull(m, ' ', task->blocked.sig[0] & 0x7fffffffUL);
 518         seq_put_decimal_ull(m, ' ', sigign.sig[0] & 0x7fffffffUL);
 519         seq_put_decimal_ull(m, ' ', sigcatch.sig[0] & 0x7fffffffUL);
 520         seq_put_decimal_ull(m, ' ', wchan);
 521         seq_put_decimal_ull(m, ' ', 0);
 522         seq_put_decimal_ull(m, ' ', 0);
 523         seq_put_decimal_ll(m, ' ', task->exit_signal);
 524         seq_put_decimal_ll(m, ' ', task_cpu(task));
 525         seq_put_decimal_ull(m, ' ', task->rt_priority);
 526         seq_put_decimal_ull(m, ' ', task->policy);
 527         seq_put_decimal_ull(m, ' ', delayacct_blkio_ticks(task));
 528         seq_put_decimal_ull(m, ' ', cputime_to_clock_t(gtime));
 529         seq_put_decimal_ll(m, ' ', cputime_to_clock_t(cgtime));
 530
 531         if (mm && permitted) {
 532                 seq_put_decimal_ull(m, ' ', mm->start_data);
 533                 seq_put_decimal_ull(m, ' ', mm->end_data);
 534                 seq_put_decimal_ull(m, ' ', mm->start_brk);
 535                 seq_put_decimal_ull(m, ' ', mm->arg_start);
 536                 seq_put_decimal_ull(m, ' ', mm->arg_end);
 537                 seq_put_decimal_ull(m, ' ', mm->env_start);
 538                 seq_put_decimal_ull(m, ' ', mm->env_end);
 539         } else
 540                 seq_printf(m, " 0 0 0 0 0 0 0");
 541
 542         if (permitted)
 543                 seq_put_decimal_ll(m, ' ', task->exit_code);
 544         else
 545                 seq_put_decimal_ll(m, ' ', 0);
 546
 547         seq_putc(m, '\n');
 548         if (mm)
 549                 mmput(mm);
 550         return 0;
 551 }
 552
 553 int proc_tid_stat(struct seq_file *m, struct pid_namespace *ns,
 554                         struct pid *pid, struct task_struct *task)
 555 {
 556         return do_task_stat(m, ns, pid, task, 0);
 557 }
 558
 559 int proc_tgid_stat(struct seq_file *m, struct pid_namespace *ns,
 560                         struct pid *pid, struct task_struct *task)
 561 {
 562         return do_task_stat(m, ns, pid, task, 1);
 563 }
 564
 565 int proc_pid_statm(struct seq_file *m, struct pid_namespace *ns,
 566                         struct pid *pid, struct task_struct *task)
 567 {
 568         unsigned long size = 0, resident = 0, shared = 0, text = 0, data = 0;
 569         struct mm_struct *mm = get_task_mm(task);
 570
 571         if (mm) {
 572                 size = task_statm(mm, &shared, &text, &data, &resident);
 573                 mmput(mm);
 574         }
 575         /*
 576          * For quick read, open code by putting numbers directly
 577          * expected format is
 578          * seq_printf(m, "%lu %lu %lu %lu 0 %lu 0\n",
 579          *               size, resident, shared, text, data);
 580          */
 581         seq_put_decimal_ull(m, 0, size);
 582         seq_put_decimal_ull(m, ' ', resident);
 583         seq_put_decimal_ull(m, ' ', shared);
 584         seq_put_decimal_ull(m, ' ', text);
 585         seq_put_decimal_ull(m, ' ', 0);
 586         seq_put_decimal_ull(m, ' ', data);
 587         seq_put_decimal_ull(m, ' ', 0);
 588         seq_putc(m, '\n');
 589
 590         return 0;
 591 }
 592
 593 #ifdef CONFIG_CHECKPOINT_RESTORE
 594 static struct pid *
 595 get_children_pid(struct inode *inode, struct pid *pid_prev, loff_t pos)
 596 {
 597         struct task_struct *start, *task;
 598         struct pid *pid = NULL;
 599
 600         read_lock(&tasklist_lock);
 601
 602         start = pid_task(proc_pid(inode), PIDTYPE_PID);
 603         if (!start)
 604                 goto out;
 605
 606         /*
 607          * Lets try to continue searching first, this gives
 608          * us significant speedup on children-rich processes.
 609          */
 610         if (pid_prev) {
 611                 task = pid_task(pid_prev, PIDTYPE_PID);
 612                 if (task && task->real_parent == start &&
 613                     !(list_empty(&task->sibling))) {
 614                         if (list_is_last(&task->sibling, &start->children))
 615                                 goto out;
 616                         task = list_first_entry(&task->sibling,
 617                                                 struct task_struct, sibling);
 618                         pid = get_pid(task_pid(task));
 619                         goto out;
 620                 }
 621         }
 622
 623         /*
 624          * Slow search case.
 625          *
 626          * We might miss some children here if children
 627          * are exited while we were not holding the lock,
 628          * but it was never promised to be accurate that
 629          * much.
 630          *
 631          * "Just suppose that the parent sleeps, but N children
 632          *  exit after we printed their tids. Now the slow paths
 633          *  skips N extra children, we miss N tasks." (c)
 634          *
 635          * So one need to stop or freeze the leader and all
 636          * its children to get a precise result.
 637          */
 638         list_for_each_entry(task, &start->children, sibling) {
 639                 if (pos-- == 0) {
 640                         pid = get_pid(task_pid(task));
 641                         break;
 642                 }
 643         }
 644
 645 out:
 646         read_unlock(&tasklist_lock);
 647         return pid;
 648 }
 649
 650 static int children_seq_show(struct seq_file *seq, void *v)
 651 {
 652         struct inode *inode = seq->private;
 653         pid_t pid;
 654
 655         pid = pid_nr_ns(v, inode->i_sb->s_fs_info);
 656         return seq_printf(seq, "%d ", pid);
 657 }
 658
 659 static void *children_seq_start(struct seq_file *seq, loff_t *pos)
 660 {
 661         return get_children_pid(seq->private, NULL, *pos);
 662 }
 663
 664 static void *children_seq_next(struct seq_file *seq, void *v, loff_t *pos)
 665 {
 666         struct pid *pid;
 667
 668         pid = get_children_pid(seq->private, v, *pos + 1);
 669         put_pid(v);
 670
 671         ++*pos;
 672         return pid;
 673 }
 674
 675 static void children_seq_stop(struct seq_file *seq, void *v)
 676 {
 677         put_pid(v);
 678 }
 679
 680 static const struct seq_operations children_seq_ops = {
 681         .start  = children_seq_start,
 682         .next   = children_seq_next,
 683         .stop   = children_seq_stop,
 684         .show   = children_seq_show,
 685 };
 686
 687 static int children_seq_open(struct inode *inode, struct file *file)
 688 {
 689         struct seq_file *m;
 690         int ret;
 691
 692         ret = seq_open(file, &children_seq_ops);
 693         if (ret)
 694                 return ret;
 695
 696         m = file->private_data;
 697         m->private = inode;
 698
 699         return ret;
 700 }
 701
 702 int children_seq_release(struct inode *inode, struct file *file)
 703 {
 704         seq_release(inode, file);
 705         return 0;
 706 }
 707
 708 const struct file_operations proc_tid_children_operations = {
 709         .open    = children_seq_open,
 710         .read    = seq_read,
 711         .llseek  = seq_lseek,
 712         .release = children_seq_release,
 713 };
 714 #endif /* CONFIG_CHECKPOINT_RESTORE */