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/string_helpers.h>
 85#include <linux/user_namespace.h>
 86
 87#include <asm/pgtable.h>
 88#include <asm/processor.h>
 89#include "internal.h"
 90
 91static inline void task_name(struct seq_file *m, struct task_struct *p)
 92{
 93	char *buf;
 94	size_t size;
 
 95	char tcomm[sizeof(p->comm)];
 96	int ret;
 97
 98	get_task_comm(tcomm, p);
 99
100	seq_puts(m, "Name:\t");
101
102	size = seq_get_buf(m, &buf);
103	ret = string_escape_str(tcomm, buf, size, ESCAPE_SPACE | ESCAPE_SPECIAL, "\n\\");
104	seq_commit(m, ret < size ? ret : -1);
105
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
106	seq_putc(m, '\n');
107}
108
109/*
110 * The task state array is a strange "bitmap" of
111 * reasons to sleep. Thus "running" is zero, and
112 * you can test for combinations of others with
113 * simple bit tests.
114 */
115static const char * const task_state_array[] = {
116	"R (running)",		/*   0 */
117	"S (sleeping)",		/*   1 */
118	"D (disk sleep)",	/*   2 */
119	"T (stopped)",		/*   4 */
120	"t (tracing stop)",	/*   8 */
121	"X (dead)",		/*  16 */
122	"Z (zombie)",		/*  32 */
 
 
 
123};
124
125static inline const char *get_task_state(struct task_struct *tsk)
126{
127	unsigned int state = (tsk->state | tsk->exit_state) & TASK_REPORT;
128
129	/*
130	 * Parked tasks do not run; they sit in __kthread_parkme().
131	 * Without this check, we would report them as running, which is
132	 * clearly wrong, so we report them as sleeping instead.
133	 */
134	if (tsk->state == TASK_PARKED)
135		state = TASK_INTERRUPTIBLE;
136
137	BUILD_BUG_ON(1 + ilog2(TASK_REPORT) != ARRAY_SIZE(task_state_array)-1);
138
139	return task_state_array[fls(state)];
 
 
 
 
140}
141
142static inline void task_state(struct seq_file *m, struct pid_namespace *ns,
143				struct pid *pid, struct task_struct *p)
144{
145	struct user_namespace *user_ns = seq_user_ns(m);
146	struct group_info *group_info;
147	int g;
148	struct task_struct *tracer;
149	const struct cred *cred;
150	pid_t ppid, tpid = 0, tgid, ngid;
151	unsigned int max_fds = 0;
152
153	rcu_read_lock();
154	ppid = pid_alive(p) ?
155		task_tgid_nr_ns(rcu_dereference(p->real_parent), ns) : 0;
156
157	tracer = ptrace_parent(p);
158	if (tracer)
159		tpid = task_pid_nr_ns(tracer, ns);
160
161	tgid = task_tgid_nr_ns(p, ns);
162	ngid = task_numa_group_id(p);
163	cred = get_task_cred(p);
164
165	task_lock(p);
166	if (p->files)
167		max_fds = files_fdtable(p->files)->max_fds;
168	task_unlock(p);
169	rcu_read_unlock();
170
171	seq_printf(m,
172		"State:\t%s\n"
173		"Tgid:\t%d\n"
174		"Ngid:\t%d\n"
175		"Pid:\t%d\n"
176		"PPid:\t%d\n"
177		"TracerPid:\t%d\n"
178		"Uid:\t%d\t%d\t%d\t%d\n"
179		"Gid:\t%d\t%d\t%d\t%d\n"
180		"FDSize:\t%d\nGroups:\t",
181		get_task_state(p),
182		tgid, ngid, pid_nr_ns(pid, ns), ppid, tpid,
 
 
183		from_kuid_munged(user_ns, cred->uid),
184		from_kuid_munged(user_ns, cred->euid),
185		from_kuid_munged(user_ns, cred->suid),
186		from_kuid_munged(user_ns, cred->fsuid),
187		from_kgid_munged(user_ns, cred->gid),
188		from_kgid_munged(user_ns, cred->egid),
189		from_kgid_munged(user_ns, cred->sgid),
190		from_kgid_munged(user_ns, cred->fsgid),
191		max_fds);
 
 
 
 
 
 
 
 
192
193	group_info = cred->group_info;
194	for (g = 0; g < group_info->ngroups; g++)
 
 
195		seq_printf(m, "%d ",
196			   from_kgid_munged(user_ns, GROUP_AT(group_info, g)));
197	put_cred(cred);
198
199#ifdef CONFIG_PID_NS
200	seq_puts(m, "\nNStgid:");
201	for (g = ns->level; g <= pid->level; g++)
202		seq_printf(m, "\t%d",
203			task_tgid_nr_ns(p, pid->numbers[g].ns));
204	seq_puts(m, "\nNSpid:");
205	for (g = ns->level; g <= pid->level; g++)
206		seq_printf(m, "\t%d",
207			task_pid_nr_ns(p, pid->numbers[g].ns));
208	seq_puts(m, "\nNSpgid:");
209	for (g = ns->level; g <= pid->level; g++)
210		seq_printf(m, "\t%d",
211			task_pgrp_nr_ns(p, pid->numbers[g].ns));
212	seq_puts(m, "\nNSsid:");
213	for (g = ns->level; g <= pid->level; g++)
214		seq_printf(m, "\t%d",
215			task_session_nr_ns(p, pid->numbers[g].ns));
216#endif
217	seq_putc(m, '\n');
218}
219
220void render_sigset_t(struct seq_file *m, const char *header,
221				sigset_t *set)
222{
223	int i;
224
225	seq_puts(m, header);
226
227	i = _NSIG;
228	do {
229		int x = 0;
230
231		i -= 4;
232		if (sigismember(set, i+1)) x |= 1;
233		if (sigismember(set, i+2)) x |= 2;
234		if (sigismember(set, i+3)) x |= 4;
235		if (sigismember(set, i+4)) x |= 8;
236		seq_printf(m, "%x", x);
237	} while (i >= 4);
238
239	seq_putc(m, '\n');
240}
241
242static void collect_sigign_sigcatch(struct task_struct *p, sigset_t *ign,
243				    sigset_t *catch)
244{
245	struct k_sigaction *k;
246	int i;
247
248	k = p->sighand->action;
249	for (i = 1; i <= _NSIG; ++i, ++k) {
250		if (k->sa.sa_handler == SIG_IGN)
251			sigaddset(ign, i);
252		else if (k->sa.sa_handler != SIG_DFL)
253			sigaddset(catch, i);
254	}
255}
256
257static inline void task_sig(struct seq_file *m, struct task_struct *p)
258{
259	unsigned long flags;
260	sigset_t pending, shpending, blocked, ignored, caught;
261	int num_threads = 0;
262	unsigned long qsize = 0;
263	unsigned long qlim = 0;
264
265	sigemptyset(&pending);
266	sigemptyset(&shpending);
267	sigemptyset(&blocked);
268	sigemptyset(&ignored);
269	sigemptyset(&caught);
270
271	if (lock_task_sighand(p, &flags)) {
272		pending = p->pending.signal;
273		shpending = p->signal->shared_pending.signal;
274		blocked = p->blocked;
275		collect_sigign_sigcatch(p, &ignored, &caught);
276		num_threads = get_nr_threads(p);
277		rcu_read_lock();  /* FIXME: is this correct? */
278		qsize = atomic_read(&__task_cred(p)->user->sigpending);
279		rcu_read_unlock();
280		qlim = task_rlimit(p, RLIMIT_SIGPENDING);
281		unlock_task_sighand(p, &flags);
282	}
283
284	seq_printf(m, "Threads:\t%d\n", num_threads);
285	seq_printf(m, "SigQ:\t%lu/%lu\n", qsize, qlim);
286
287	/* render them all */
288	render_sigset_t(m, "SigPnd:\t", &pending);
289	render_sigset_t(m, "ShdPnd:\t", &shpending);
290	render_sigset_t(m, "SigBlk:\t", &blocked);
291	render_sigset_t(m, "SigIgn:\t", &ignored);
292	render_sigset_t(m, "SigCgt:\t", &caught);
293}
294
295static void render_cap_t(struct seq_file *m, const char *header,
296			kernel_cap_t *a)
297{
298	unsigned __capi;
299
300	seq_puts(m, header);
301	CAP_FOR_EACH_U32(__capi) {
302		seq_printf(m, "%08x",
303			   a->cap[CAP_LAST_U32 - __capi]);
304	}
305	seq_putc(m, '\n');
306}
307
308static inline void task_cap(struct seq_file *m, struct task_struct *p)
309{
310	const struct cred *cred;
311	kernel_cap_t cap_inheritable, cap_permitted, cap_effective,
312			cap_bset, cap_ambient;
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	cap_ambient	= cred->cap_ambient;
321	rcu_read_unlock();
322
323	render_cap_t(m, "CapInh:\t", &cap_inheritable);
324	render_cap_t(m, "CapPrm:\t", &cap_permitted);
325	render_cap_t(m, "CapEff:\t", &cap_effective);
326	render_cap_t(m, "CapBnd:\t", &cap_bset);
327	render_cap_t(m, "CapAmb:\t", &cap_ambient);
328}
329
330static inline void task_seccomp(struct seq_file *m, struct task_struct *p)
331{
332#ifdef CONFIG_SECCOMP
333	seq_printf(m, "Seccomp:\t%d\n", p->seccomp.mode);
334#endif
335}
336
337static inline void task_context_switch_counts(struct seq_file *m,
338						struct task_struct *p)
339{
340	seq_printf(m,	"voluntary_ctxt_switches:\t%lu\n"
341			"nonvoluntary_ctxt_switches:\t%lu\n",
342			p->nvcsw,
343			p->nivcsw);
344}
345
346static void task_cpus_allowed(struct seq_file *m, struct task_struct *task)
347{
348	seq_printf(m, "Cpus_allowed:\t%*pb\n",
349		   cpumask_pr_args(&task->cpus_allowed));
350	seq_printf(m, "Cpus_allowed_list:\t%*pbl\n",
351		   cpumask_pr_args(&task->cpus_allowed));
 
 
352}
353
354int proc_pid_status(struct seq_file *m, struct pid_namespace *ns,
355			struct pid *pid, struct task_struct *task)
356{
357	struct mm_struct *mm = get_task_mm(task);
358
359	task_name(m, task);
360	task_state(m, ns, pid, task);
361
362	if (mm) {
363		task_mem(m, mm);
364		mmput(mm);
365	}
366	task_sig(m, task);
367	task_cap(m, task);
368	task_seccomp(m, task);
369	task_cpus_allowed(m, task);
370	cpuset_task_status_allowed(m, task);
371	task_context_switch_counts(m, task);
372	return 0;
373}
374
375static int do_task_stat(struct seq_file *m, struct pid_namespace *ns,
376			struct pid *pid, struct task_struct *task, int whole)
377{
378	unsigned long vsize, eip, esp, wchan = 0;
379	int priority, nice;
380	int tty_pgrp = -1, tty_nr = 0;
381	sigset_t sigign, sigcatch;
382	char state;
383	pid_t ppid = 0, pgid = -1, sid = -1;
384	int num_threads = 0;
385	int permitted;
386	struct mm_struct *mm;
387	unsigned long long start_time;
388	unsigned long cmin_flt = 0, cmaj_flt = 0;
389	unsigned long  min_flt = 0,  maj_flt = 0;
390	cputime_t cutime, cstime, utime, stime;
391	cputime_t cgtime, gtime;
392	unsigned long rsslim = 0;
393	char tcomm[sizeof(task->comm)];
394	unsigned long flags;
395
396	state = *get_task_state(task);
397	vsize = eip = esp = 0;
398	permitted = ptrace_may_access(task, PTRACE_MODE_READ_FSCREDS | PTRACE_MODE_NOAUDIT);
399	mm = get_task_mm(task);
400	if (mm) {
401		vsize = task_vsize(mm);
402		if (permitted) {
403			eip = KSTK_EIP(task);
404			esp = KSTK_ESP(task);
405		}
406	}
407
408	get_task_comm(tcomm, task);
409
410	sigemptyset(&sigign);
411	sigemptyset(&sigcatch);
412	cutime = cstime = utime = stime = 0;
413	cgtime = gtime = 0;
414
415	if (lock_task_sighand(task, &flags)) {
416		struct signal_struct *sig = task->signal;
417
418		if (sig->tty) {
419			struct pid *pgrp = tty_get_pgrp(sig->tty);
420			tty_pgrp = pid_nr_ns(pgrp, ns);
421			put_pid(pgrp);
422			tty_nr = new_encode_dev(tty_devnum(sig->tty));
423		}
424
425		num_threads = get_nr_threads(task);
426		collect_sigign_sigcatch(task, &sigign, &sigcatch);
427
428		cmin_flt = sig->cmin_flt;
429		cmaj_flt = sig->cmaj_flt;
430		cutime = sig->cutime;
431		cstime = sig->cstime;
432		cgtime = sig->cgtime;
433		rsslim = ACCESS_ONCE(sig->rlim[RLIMIT_RSS].rlim_cur);
434
435		/* add up live thread stats at the group level */
436		if (whole) {
437			struct task_struct *t = task;
438			do {
439				min_flt += t->min_flt;
440				maj_flt += t->maj_flt;
441				gtime += task_gtime(t);
442			} while_each_thread(task, t);
 
443
444			min_flt += sig->min_flt;
445			maj_flt += sig->maj_flt;
446			thread_group_cputime_adjusted(task, &utime, &stime);
447			gtime += sig->gtime;
448		}
449
450		sid = task_session_nr_ns(task, ns);
451		ppid = task_tgid_nr_ns(task->real_parent, ns);
452		pgid = task_pgrp_nr_ns(task, ns);
453
454		unlock_task_sighand(task, &flags);
455	}
456
457	if (permitted && (!whole || num_threads < 2))
458		wchan = get_wchan(task);
459	if (!whole) {
460		min_flt = task->min_flt;
461		maj_flt = task->maj_flt;
462		task_cputime_adjusted(task, &utime, &stime);
463		gtime = task_gtime(task);
464	}
465
466	/* scale priority and nice values from timeslices to -20..20 */
467	/* to make it look like a "normal" Unix priority/nice value  */
468	priority = task_prio(task);
469	nice = task_nice(task);
470
 
 
 
 
 
471	/* convert nsec -> ticks */
472	start_time = nsec_to_clock_t(task->real_start_time);
473
474	seq_printf(m, "%d (%s) %c", pid_nr_ns(pid, ns), tcomm, state);
475	seq_put_decimal_ll(m, ' ', ppid);
476	seq_put_decimal_ll(m, ' ', pgid);
477	seq_put_decimal_ll(m, ' ', sid);
478	seq_put_decimal_ll(m, ' ', tty_nr);
479	seq_put_decimal_ll(m, ' ', tty_pgrp);
480	seq_put_decimal_ull(m, ' ', task->flags);
481	seq_put_decimal_ull(m, ' ', min_flt);
482	seq_put_decimal_ull(m, ' ', cmin_flt);
483	seq_put_decimal_ull(m, ' ', maj_flt);
484	seq_put_decimal_ull(m, ' ', cmaj_flt);
485	seq_put_decimal_ull(m, ' ', cputime_to_clock_t(utime));
486	seq_put_decimal_ull(m, ' ', cputime_to_clock_t(stime));
487	seq_put_decimal_ll(m, ' ', cputime_to_clock_t(cutime));
488	seq_put_decimal_ll(m, ' ', cputime_to_clock_t(cstime));
489	seq_put_decimal_ll(m, ' ', priority);
490	seq_put_decimal_ll(m, ' ', nice);
491	seq_put_decimal_ll(m, ' ', num_threads);
492	seq_put_decimal_ull(m, ' ', 0);
493	seq_put_decimal_ull(m, ' ', start_time);
494	seq_put_decimal_ull(m, ' ', vsize);
495	seq_put_decimal_ull(m, ' ', mm ? get_mm_rss(mm) : 0);
496	seq_put_decimal_ull(m, ' ', rsslim);
497	seq_put_decimal_ull(m, ' ', mm ? (permitted ? mm->start_code : 1) : 0);
498	seq_put_decimal_ull(m, ' ', mm ? (permitted ? mm->end_code : 1) : 0);
499	seq_put_decimal_ull(m, ' ', (permitted && mm) ? mm->start_stack : 0);
500	seq_put_decimal_ull(m, ' ', esp);
501	seq_put_decimal_ull(m, ' ', eip);
502	/* The signal information here is obsolete.
503	 * It must be decimal for Linux 2.0 compatibility.
504	 * Use /proc/#/status for real-time signals.
505	 */
506	seq_put_decimal_ull(m, ' ', task->pending.signal.sig[0] & 0x7fffffffUL);
507	seq_put_decimal_ull(m, ' ', task->blocked.sig[0] & 0x7fffffffUL);
508	seq_put_decimal_ull(m, ' ', sigign.sig[0] & 0x7fffffffUL);
509	seq_put_decimal_ull(m, ' ', sigcatch.sig[0] & 0x7fffffffUL);
510
511	/*
512	 * We used to output the absolute kernel address, but that's an
513	 * information leak - so instead we show a 0/1 flag here, to signal
514	 * to user-space whether there's a wchan field in /proc/PID/wchan.
515	 *
516	 * This works with older implementations of procps as well.
517	 */
518	if (wchan)
519		seq_puts(m, " 1");
520	else
521		seq_puts(m, " 0");
522
523	seq_put_decimal_ull(m, ' ', 0);
524	seq_put_decimal_ull(m, ' ', 0);
525	seq_put_decimal_ll(m, ' ', task->exit_signal);
526	seq_put_decimal_ll(m, ' ', task_cpu(task));
527	seq_put_decimal_ull(m, ' ', task->rt_priority);
528	seq_put_decimal_ull(m, ' ', task->policy);
529	seq_put_decimal_ull(m, ' ', delayacct_blkio_ticks(task));
530	seq_put_decimal_ull(m, ' ', cputime_to_clock_t(gtime));
531	seq_put_decimal_ll(m, ' ', cputime_to_clock_t(cgtime));
532
533	if (mm && permitted) {
534		seq_put_decimal_ull(m, ' ', mm->start_data);
535		seq_put_decimal_ull(m, ' ', mm->end_data);
536		seq_put_decimal_ull(m, ' ', mm->start_brk);
537		seq_put_decimal_ull(m, ' ', mm->arg_start);
538		seq_put_decimal_ull(m, ' ', mm->arg_end);
539		seq_put_decimal_ull(m, ' ', mm->env_start);
540		seq_put_decimal_ull(m, ' ', mm->env_end);
541	} else
542		seq_printf(m, " 0 0 0 0 0 0 0");
543
544	if (permitted)
545		seq_put_decimal_ll(m, ' ', task->exit_code);
546	else
547		seq_put_decimal_ll(m, ' ', 0);
548
549	seq_putc(m, '\n');
550	if (mm)
551		mmput(mm);
552	return 0;
553}
554
555int proc_tid_stat(struct seq_file *m, struct pid_namespace *ns,
556			struct pid *pid, struct task_struct *task)
557{
558	return do_task_stat(m, ns, pid, task, 0);
559}
560
561int proc_tgid_stat(struct seq_file *m, struct pid_namespace *ns,
562			struct pid *pid, struct task_struct *task)
563{
564	return do_task_stat(m, ns, pid, task, 1);
565}
566
567int proc_pid_statm(struct seq_file *m, struct pid_namespace *ns,
568			struct pid *pid, struct task_struct *task)
569{
570	unsigned long size = 0, resident = 0, shared = 0, text = 0, data = 0;
571	struct mm_struct *mm = get_task_mm(task);
572
573	if (mm) {
574		size = task_statm(mm, &shared, &text, &data, &resident);
575		mmput(mm);
576	}
577	/*
578	 * For quick read, open code by putting numbers directly
579	 * expected format is
580	 * seq_printf(m, "%lu %lu %lu %lu 0 %lu 0\n",
581	 *               size, resident, shared, text, data);
582	 */
583	seq_put_decimal_ull(m, 0, size);
584	seq_put_decimal_ull(m, ' ', resident);
585	seq_put_decimal_ull(m, ' ', shared);
586	seq_put_decimal_ull(m, ' ', text);
587	seq_put_decimal_ull(m, ' ', 0);
588	seq_put_decimal_ull(m, ' ', data);
589	seq_put_decimal_ull(m, ' ', 0);
590	seq_putc(m, '\n');
591
592	return 0;
593}
594
595#ifdef CONFIG_PROC_CHILDREN
596static struct pid *
597get_children_pid(struct inode *inode, struct pid *pid_prev, loff_t pos)
598{
599	struct task_struct *start, *task;
600	struct pid *pid = NULL;
601
602	read_lock(&tasklist_lock);
603
604	start = pid_task(proc_pid(inode), PIDTYPE_PID);
605	if (!start)
606		goto out;
607
608	/*
609	 * Lets try to continue searching first, this gives
610	 * us significant speedup on children-rich processes.
611	 */
612	if (pid_prev) {
613		task = pid_task(pid_prev, PIDTYPE_PID);
614		if (task && task->real_parent == start &&
615		    !(list_empty(&task->sibling))) {
616			if (list_is_last(&task->sibling, &start->children))
617				goto out;
618			task = list_first_entry(&task->sibling,
619						struct task_struct, sibling);
620			pid = get_pid(task_pid(task));
621			goto out;
622		}
623	}
624
625	/*
626	 * Slow search case.
627	 *
628	 * We might miss some children here if children
629	 * are exited while we were not holding the lock,
630	 * but it was never promised to be accurate that
631	 * much.
632	 *
633	 * "Just suppose that the parent sleeps, but N children
634	 *  exit after we printed their tids. Now the slow paths
635	 *  skips N extra children, we miss N tasks." (c)
636	 *
637	 * So one need to stop or freeze the leader and all
638	 * its children to get a precise result.
639	 */
640	list_for_each_entry(task, &start->children, sibling) {
641		if (pos-- == 0) {
642			pid = get_pid(task_pid(task));
643			break;
644		}
645	}
646
647out:
648	read_unlock(&tasklist_lock);
649	return pid;
650}
651
652static int children_seq_show(struct seq_file *seq, void *v)
653{
654	struct inode *inode = seq->private;
655	pid_t pid;
656
657	pid = pid_nr_ns(v, inode->i_sb->s_fs_info);
658	seq_printf(seq, "%d ", pid);
659
660	return 0;
661}
662
663static void *children_seq_start(struct seq_file *seq, loff_t *pos)
664{
665	return get_children_pid(seq->private, NULL, *pos);
666}
667
668static void *children_seq_next(struct seq_file *seq, void *v, loff_t *pos)
669{
670	struct pid *pid;
671
672	pid = get_children_pid(seq->private, v, *pos + 1);
673	put_pid(v);
674
675	++*pos;
676	return pid;
677}
678
679static void children_seq_stop(struct seq_file *seq, void *v)
680{
681	put_pid(v);
682}
683
684static const struct seq_operations children_seq_ops = {
685	.start	= children_seq_start,
686	.next	= children_seq_next,
687	.stop	= children_seq_stop,
688	.show	= children_seq_show,
689};
690
691static int children_seq_open(struct inode *inode, struct file *file)
692{
693	struct seq_file *m;
694	int ret;
695
696	ret = seq_open(file, &children_seq_ops);
697	if (ret)
698		return ret;
699
700	m = file->private_data;
701	m->private = inode;
702
703	return ret;
704}
705
706int children_seq_release(struct inode *inode, struct file *file)
707{
708	seq_release(inode, file);
709	return 0;
710}
711
712const struct file_operations proc_tid_children_operations = {
713	.open    = children_seq_open,
714	.read    = seq_read,
715	.llseek  = seq_lseek,
716	.release = children_seq_release,
717};
718#endif /* CONFIG_PROC_CHILDREN */