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Root/kernel/fork.c

1	/*
2	* linux/kernel/fork.c
3	*
4	* Copyright (C) 1991, 1992 Linus Torvalds
5	*/
6
7	/*
8	* 'fork.c' contains the help-routines for the 'fork' system call
9	* (see also entry.S and others).
10	* Fork is rather simple, once you get the hang of it, but the memory
11	* management can be a bitch. See 'mm/memory.c': 'copy_page_range()'
12	*/
13
14	#include <linux/slab.h>
15	#include <linux/init.h>
16	#include <linux/unistd.h>
17	#include <linux/module.h>
18	#include <linux/vmalloc.h>
19	#include <linux/completion.h>
20	#include <linux/personality.h>
21	#include <linux/mempolicy.h>
22	#include <linux/sem.h>
23	#include <linux/file.h>
24	#include <linux/fdtable.h>
25	#include <linux/iocontext.h>
26	#include <linux/key.h>
27	#include <linux/binfmts.h>
28	#include <linux/mman.h>
29	#include <linux/mmu_notifier.h>
30	#include <linux/fs.h>
31	#include <linux/nsproxy.h>
32	#include <linux/capability.h>
33	#include <linux/cpu.h>
34	#include <linux/cgroup.h>
35	#include <linux/security.h>
36	#include <linux/hugetlb.h>
37	#include <linux/swap.h>
38	#include <linux/syscalls.h>
39	#include <linux/jiffies.h>
40	#include <linux/tracehook.h>
41	#include <linux/futex.h>
42	#include <linux/compat.h>
43	#include <linux/task_io_accounting_ops.h>
44	#include <linux/rcupdate.h>
45	#include <linux/ptrace.h>
46	#include <linux/mount.h>
47	#include <linux/audit.h>
48	#include <linux/memcontrol.h>
49	#include <linux/ftrace.h>
50	#include <linux/profile.h>
51	#include <linux/rmap.h>
52	#include <linux/ksm.h>
53	#include <linux/acct.h>
54	#include <linux/tsacct_kern.h>
55	#include <linux/cn_proc.h>
56	#include <linux/freezer.h>
57	#include <linux/delayacct.h>
58	#include <linux/taskstats_kern.h>
59	#include <linux/random.h>
60	#include <linux/tty.h>
61	#include <linux/proc_fs.h>
62	#include <linux/blkdev.h>
63	#include <linux/fs_struct.h>
64	#include <linux/magic.h>
65	#include <linux/perf_event.h>
66	#include <linux/posix-timers.h>
67	#include <linux/user-return-notifier.h>
68
69	#include <asm/pgtable.h>
70	#include <asm/pgalloc.h>
71	#include <asm/uaccess.h>
72	#include <asm/mmu_context.h>
73	#include <asm/cacheflush.h>
74	#include <asm/tlbflush.h>
75
76	#include <trace/events/sched.h>
77
78	/*
79	* Protected counters by write_lock_irq(&tasklist_lock)
80	*/
81	unsigned long total_forks; /* Handle normal Linux uptimes. */
82	int nr_threads; /* The idle threads do not count.. */
83
84	int max_threads; /* tunable limit on nr_threads */
85
86	DEFINE_PER_CPU(unsigned long, process_counts) = 0;
87
88	__cacheline_aligned DEFINE_RWLOCK(tasklist_lock); /* outer */
89
90	#ifdef CONFIG_PROVE_RCU
91	int lockdep_tasklist_lock_is_held(void)
92	{
93	return lockdep_is_held(&tasklist_lock);
94	}
95	EXPORT_SYMBOL_GPL(lockdep_tasklist_lock_is_held);
96	#endif /* #ifdef CONFIG_PROVE_RCU */
97
98	int nr_processes(void)
99	{
100	int cpu;
101	int total = 0;
102
103	for_each_possible_cpu(cpu)
104	total += per_cpu(process_counts, cpu);
105
106	return total;
107	}
108
109	#ifndef __HAVE_ARCH_TASK_STRUCT_ALLOCATOR
110	# define alloc_task_struct() kmem_cache_alloc(task_struct_cachep, GFP_KERNEL)
111	# define free_task_struct(tsk) kmem_cache_free(task_struct_cachep, (tsk))
112	static struct kmem_cache *task_struct_cachep;
113	#endif
114
115	#ifndef __HAVE_ARCH_THREAD_INFO_ALLOCATOR
116	static inline struct thread_info alloc_thread_info(struct task_struct tsk)
117	{
118	#ifdef CONFIG_DEBUG_STACK_USAGE
119	gfp_t mask = GFP_KERNEL \| __GFP_ZERO;
120	#else
121	gfp_t mask = GFP_KERNEL;
122	#endif
123	return (struct thread_info *)__get_free_pages(mask, THREAD_SIZE_ORDER);
124	}
125
126	static inline void free_thread_info(struct thread_info *ti)
127	{
128	free_pages((unsigned long)ti, THREAD_SIZE_ORDER);
129	}
130	#endif
131
132	/* SLAB cache for signal_struct structures (tsk->signal) */
133	static struct kmem_cache *signal_cachep;
134
135	/* SLAB cache for sighand_struct structures (tsk->sighand) */
136	struct kmem_cache *sighand_cachep;
137
138	/* SLAB cache for files_struct structures (tsk->files) */
139	struct kmem_cache *files_cachep;
140
141	/* SLAB cache for fs_struct structures (tsk->fs) */
142	struct kmem_cache *fs_cachep;
143
144	/* SLAB cache for vm_area_struct structures */
145	struct kmem_cache *vm_area_cachep;
146
147	/* SLAB cache for mm_struct structures (tsk->mm) */
148	static struct kmem_cache *mm_cachep;
149
150	static void account_kernel_stack(struct thread_info *ti, int account)
151	{
152	struct zone *zone = page_zone(virt_to_page(ti));
153
154	mod_zone_page_state(zone, NR_KERNEL_STACK, account);
155	}
156
157	void free_task(struct task_struct *tsk)
158	{
159	prop_local_destroy_single(&tsk->dirties);
160	account_kernel_stack(tsk->stack, -1);
161	free_thread_info(tsk->stack);
162	rt_mutex_debug_task_free(tsk);
163	ftrace_graph_exit_task(tsk);
164	free_task_struct(tsk);
165	}
166	EXPORT_SYMBOL(free_task);
167
168	void __put_task_struct(struct task_struct *tsk)
169	{
170	WARN_ON(!tsk->exit_state);
171	WARN_ON(atomic_read(&tsk->usage));
172	WARN_ON(tsk == current);
173
174	exit_creds(tsk);
175	delayacct_tsk_free(tsk);
176
177	if (!profile_handoff_task(tsk))
178	free_task(tsk);
179	}
180
181	/*
182	* macro override instead of weak attribute alias, to workaround
183	* gcc 4.1.0 and 4.1.1 bugs with weak attribute and empty functions.
184	*/
185	#ifndef arch_task_cache_init
186	#define arch_task_cache_init()
187	#endif
188
189	void __init fork_init(unsigned long mempages)
190	{
191	#ifndef __HAVE_ARCH_TASK_STRUCT_ALLOCATOR
192	#ifndef ARCH_MIN_TASKALIGN
193	#define ARCH_MIN_TASKALIGN L1_CACHE_BYTES
194	#endif
195	/* create a slab on which task_structs can be allocated */
196	task_struct_cachep =
197	kmem_cache_create("task_struct", sizeof(struct task_struct),
198	ARCH_MIN_TASKALIGN, SLAB_PANIC \| SLAB_NOTRACK, NULL);
199	#endif
200
201	/* do the arch specific task caches init */
202	arch_task_cache_init();
203
204	/*
205	* The default maximum number of threads is set to a safe
206	* value: the thread structures can take up at most half
207	* of memory.
208	*/
209	max_threads = mempages / (8 * THREAD_SIZE / PAGE_SIZE);
210
211	/*
212	* we need to allow at least 20 threads to boot a system
213	*/
214	if(max_threads < 20)
215	max_threads = 20;
216
217	init_task.signal->rlim[RLIMIT_NPROC].rlim_cur = max_threads/2;
218	init_task.signal->rlim[RLIMIT_NPROC].rlim_max = max_threads/2;
219	init_task.signal->rlim[RLIMIT_SIGPENDING] =
220	init_task.signal->rlim[RLIMIT_NPROC];
221	}
222
223	int __attribute__((weak)) arch_dup_task_struct(struct task_struct *dst,
224	struct task_struct *src)
225	{
226	dst = src;
227	return 0;
228	}
229
230	static struct task_struct dup_task_struct(struct task_struct orig)
231	{
232	struct task_struct *tsk;
233	struct thread_info *ti;
234	unsigned long *stackend;
235
236	int err;
237
238	prepare_to_copy(orig);
239
240	tsk = alloc_task_struct();
241	if (!tsk)
242	return NULL;
243
244	ti = alloc_thread_info(tsk);
245	if (!ti) {
246	free_task_struct(tsk);
247	return NULL;
248	}
249
250	err = arch_dup_task_struct(tsk, orig);
251	if (err)
252	goto out;
253
254	tsk->stack = ti;
255
256	err = prop_local_init_single(&tsk->dirties);
257	if (err)
258	goto out;
259
260	setup_thread_stack(tsk, orig);
261	clear_user_return_notifier(tsk);
262	stackend = end_of_stack(tsk);
263	stackend = STACK_END_MAGIC; / for overflow detection */
264
265	#ifdef CONFIG_CC_STACKPROTECTOR
266	tsk->stack_canary = get_random_int();
267	#endif
268
269	/* One for us, one for whoever does the "release_task()" (usually parent) */
270	atomic_set(&tsk->usage,2);
271	atomic_set(&tsk->fs_excl, 0);
272	#ifdef CONFIG_BLK_DEV_IO_TRACE
273	tsk->btrace_seq = 0;
274	#endif
275	tsk->splice_pipe = NULL;
276
277	account_kernel_stack(ti, 1);
278
279	return tsk;
280
281	out:
282	free_thread_info(ti);
283	free_task_struct(tsk);
284	return NULL;
285	}
286
287	#ifdef CONFIG_MMU
288	static int dup_mmap(struct mm_struct mm, struct mm_struct oldmm)
289	{
290	struct vm_area_struct mpnt, tmp, **pprev;
291	struct rb_node *rb_link, rb_parent;
292	int retval;
293	unsigned long charge;
294	struct mempolicy *pol;
295
296	down_write(&oldmm->mmap_sem);
297	flush_cache_dup_mm(oldmm);
298	/*
299	* Not linked in yet - no deadlock potential:
300	*/
301	down_write_nested(&mm->mmap_sem, SINGLE_DEPTH_NESTING);
302
303	mm->locked_vm = 0;
304	mm->mmap = NULL;
305	mm->mmap_cache = NULL;
306	mm->free_area_cache = oldmm->mmap_base;
307	mm->cached_hole_size = ~0UL;
308	mm->map_count = 0;
309	cpumask_clear(mm_cpumask(mm));
310	mm->mm_rb = RB_ROOT;
311	rb_link = &mm->mm_rb.rb_node;
312	rb_parent = NULL;
313	pprev = &mm->mmap;
314	retval = ksm_fork(mm, oldmm);
315	if (retval)
316	goto out;
317
318	for (mpnt = oldmm->mmap; mpnt; mpnt = mpnt->vm_next) {
319	struct file *file;
320
321	if (mpnt->vm_flags & VM_DONTCOPY) {
322	long pages = vma_pages(mpnt);
323	mm->total_vm -= pages;
324	vm_stat_account(mm, mpnt->vm_flags, mpnt->vm_file,
325	-pages);
326	continue;
327	}
328	charge = 0;
329	if (mpnt->vm_flags & VM_ACCOUNT) {
330	unsigned int len = (mpnt->vm_end - mpnt->vm_start) >> PAGE_SHIFT;
331	if (security_vm_enough_memory(len))
332	goto fail_nomem;
333	charge = len;
334	}
335	tmp = kmem_cache_alloc(vm_area_cachep, GFP_KERNEL);
336	if (!tmp)
337	goto fail_nomem;
338	tmp = mpnt;
339	INIT_LIST_HEAD(&tmp->anon_vma_chain);
340	pol = mpol_dup(vma_policy(mpnt));
341	retval = PTR_ERR(pol);
342	if (IS_ERR(pol))
343	goto fail_nomem_policy;
344	vma_set_policy(tmp, pol);
345	if (anon_vma_fork(tmp, mpnt))
346	goto fail_nomem_anon_vma_fork;
347	tmp->vm_flags &= ~VM_LOCKED;
348	tmp->vm_mm = mm;
349	tmp->vm_next = NULL;
350	file = tmp->vm_file;
351	if (file) {
352	struct inode *inode = file->f_path.dentry->d_inode;
353	struct address_space *mapping = file->f_mapping;
354
355	get_file(file);
356	if (tmp->vm_flags & VM_DENYWRITE)
357	atomic_dec(&inode->i_writecount);
358	spin_lock(&mapping->i_mmap_lock);
359	if (tmp->vm_flags & VM_SHARED)
360	mapping->i_mmap_writable++;
361	tmp->vm_truncate_count = mpnt->vm_truncate_count;
362	flush_dcache_mmap_lock(mapping);
363	/* insert tmp into the share list, just after mpnt */
364	vma_prio_tree_add(tmp, mpnt);
365	flush_dcache_mmap_unlock(mapping);
366	spin_unlock(&mapping->i_mmap_lock);
367	}
368
369	/*
370	* Clear hugetlb-related page reserves for children. This only
371	* affects MAP_PRIVATE mappings. Faults generated by the child
372	* are not guaranteed to succeed, even if read-only
373	*/
374	if (is_vm_hugetlb_page(tmp))
375	reset_vma_resv_huge_pages(tmp);
376
377	/*
378	* Link in the new vma and copy the page table entries.
379	*/
380	*pprev = tmp;
381	pprev = &tmp->vm_next;
382
383	__vma_link_rb(mm, tmp, rb_link, rb_parent);
384	rb_link = &tmp->vm_rb.rb_right;
385	rb_parent = &tmp->vm_rb;
386
387	mm->map_count++;
388	retval = copy_page_range(mm, oldmm, mpnt);
389
390	if (tmp->vm_ops && tmp->vm_ops->open)
391	tmp->vm_ops->open(tmp);
392
393	if (retval)
394	goto out;
395	}
396	/* a new mm has just been created */
397	arch_dup_mmap(oldmm, mm);
398	retval = 0;
399	out:
400	up_write(&mm->mmap_sem);
401	flush_tlb_mm(oldmm);
402	up_write(&oldmm->mmap_sem);
403	return retval;
404	fail_nomem_anon_vma_fork:
405	mpol_put(pol);
406	fail_nomem_policy:
407	kmem_cache_free(vm_area_cachep, tmp);
408	fail_nomem:
409	retval = -ENOMEM;
410	vm_unacct_memory(charge);
411	goto out;
412	}
413
414	static inline int mm_alloc_pgd(struct mm_struct * mm)
415	{
416	mm->pgd = pgd_alloc(mm);
417	if (unlikely(!mm->pgd))
418	return -ENOMEM;
419	return 0;
420	}
421
422	static inline void mm_free_pgd(struct mm_struct * mm)
423	{
424	pgd_free(mm, mm->pgd);
425	}
426	#else
427	#define dup_mmap(mm, oldmm) (0)
428	#define mm_alloc_pgd(mm) (0)
429	#define mm_free_pgd(mm)
430	#endif /* CONFIG_MMU */
431
432	__cacheline_aligned_in_smp DEFINE_SPINLOCK(mmlist_lock);
433
434	#define allocate_mm() (kmem_cache_alloc(mm_cachep, GFP_KERNEL))
435	#define free_mm(mm) (kmem_cache_free(mm_cachep, (mm)))
436
437	static unsigned long default_dump_filter = MMF_DUMP_FILTER_DEFAULT;
438
439	static int __init coredump_filter_setup(char *s)
440	{
441	default_dump_filter =
442	(simple_strtoul(s, NULL, 0) << MMF_DUMP_FILTER_SHIFT) &
443	MMF_DUMP_FILTER_MASK;
444	return 1;
445	}
446
447	__setup("coredump_filter=", coredump_filter_setup);
448
449	#include <linux/init_task.h>
450
451	static void mm_init_aio(struct mm_struct *mm)
452	{
453	#ifdef CONFIG_AIO
454	spin_lock_init(&mm->ioctx_lock);
455	INIT_HLIST_HEAD(&mm->ioctx_list);
456	#endif
457	}
458
459	static struct mm_struct * mm_init(struct mm_struct * mm, struct task_struct *p)
460	{
461	atomic_set(&mm->mm_users, 1);
462	atomic_set(&mm->mm_count, 1);
463	init_rwsem(&mm->mmap_sem);
464	INIT_LIST_HEAD(&mm->mmlist);
465	mm->flags = (current->mm) ?
466	(current->mm->flags & MMF_INIT_MASK) : default_dump_filter;
467	mm->core_state = NULL;
468	mm->nr_ptes = 0;
469	memset(&mm->rss_stat, 0, sizeof(mm->rss_stat));
470	spin_lock_init(&mm->page_table_lock);
471	mm->free_area_cache = TASK_UNMAPPED_BASE;
472	mm->cached_hole_size = ~0UL;
473	mm_init_aio(mm);
474	mm_init_owner(mm, p);
475
476	if (likely(!mm_alloc_pgd(mm))) {
477	mm->def_flags = 0;
478	mmu_notifier_mm_init(mm);
479	return mm;
480	}
481
482	free_mm(mm);
483	return NULL;
484	}
485
486	/*
487	* Allocate and initialize an mm_struct.
488	*/
489	struct mm_struct * mm_alloc(void)
490	{
491	struct mm_struct * mm;
492
493	mm = allocate_mm();
494	if (mm) {
495	memset(mm, 0, sizeof(*mm));
496	mm = mm_init(mm, current);
497	}
498	return mm;
499	}
500
501	/*
502	* Called when the last reference to the mm
503	* is dropped: either by a lazy thread or by
504	* mmput. Free the page directory and the mm.
505	*/
506	void __mmdrop(struct mm_struct *mm)
507	{
508	BUG_ON(mm == &init_mm);
509	mm_free_pgd(mm);
510	destroy_context(mm);
511	mmu_notifier_mm_destroy(mm);
512	free_mm(mm);
513	}
514	EXPORT_SYMBOL_GPL(__mmdrop);
515
516	/*
517	* Decrement the use count and release all resources for an mm.
518	*/
519	void mmput(struct mm_struct *mm)
520	{
521	might_sleep();
522
523	if (atomic_dec_and_test(&mm->mm_users)) {
524	exit_aio(mm);
525	ksm_exit(mm);
526	exit_mmap(mm);
527	set_mm_exe_file(mm, NULL);
528	if (!list_empty(&mm->mmlist)) {
529	spin_lock(&mmlist_lock);
530	list_del(&mm->mmlist);
531	spin_unlock(&mmlist_lock);
532	}
533	put_swap_token(mm);
534	if (mm->binfmt)
535	module_put(mm->binfmt->module);
536	mmdrop(mm);
537	}
538	}
539	EXPORT_SYMBOL_GPL(mmput);
540
541	/**
542	* get_task_mm - acquire a reference to the task's mm
543	*
544	* Returns %NULL if the task has no mm. Checks PF_KTHREAD (meaning
545	* this kernel workthread has transiently adopted a user mm with use_mm,
546	* to do its AIO) is not set and if so returns a reference to it, after
547	* bumping up the use count. User must release the mm via mmput()
548	* after use. Typically used by /proc and ptrace.
549	*/
550	struct mm_struct get_task_mm(struct task_struct task)
551	{
552	struct mm_struct *mm;
553
554	task_lock(task);
555	mm = task->mm;
556	if (mm) {
557	if (task->flags & PF_KTHREAD)
558	mm = NULL;
559	else
560	atomic_inc(&mm->mm_users);
561	}
562	task_unlock(task);
563	return mm;
564	}
565	EXPORT_SYMBOL_GPL(get_task_mm);
566
567	/* Please note the differences between mmput and mm_release.
568	* mmput is called whenever we stop holding onto a mm_struct,
569	* error success whatever.
570	*
571	* mm_release is called after a mm_struct has been removed
572	* from the current process.
573	*
574	* This difference is important for error handling, when we
575	* only half set up a mm_struct for a new process and need to restore
576	* the old one. Because we mmput the new mm_struct before
577	* restoring the old one. . .
578	* Eric Biederman 10 January 1998
579	*/
580	void mm_release(struct task_struct tsk, struct mm_struct mm)
581	{
582	struct completion *vfork_done = tsk->vfork_done;
583
584	/* Get rid of any futexes when releasing the mm */
585	#ifdef CONFIG_FUTEX
586	if (unlikely(tsk->robust_list)) {
587	exit_robust_list(tsk);
588	tsk->robust_list = NULL;
589	}
590	#ifdef CONFIG_COMPAT
591	if (unlikely(tsk->compat_robust_list)) {
592	compat_exit_robust_list(tsk);
593	tsk->compat_robust_list = NULL;
594	}
595	#endif
596	if (unlikely(!list_empty(&tsk->pi_state_list)))
597	exit_pi_state_list(tsk);
598	#endif
599
600	/* Get rid of any cached register state */
601	deactivate_mm(tsk, mm);
602
603	/* notify parent sleeping on vfork() */
604	if (vfork_done) {
605	tsk->vfork_done = NULL;
606	complete(vfork_done);
607	}
608
609	/*
610	* If we're exiting normally, clear a user-space tid field if
611	* requested. We leave this alone when dying by signal, to leave
612	* the value intact in a core dump, and to save the unnecessary
613	* trouble otherwise. Userland only wants this done for a sys_exit.
614	*/
615	if (tsk->clear_child_tid) {
616	if (!(tsk->flags & PF_SIGNALED) &&
617	atomic_read(&mm->mm_users) > 1) {
618	/*
619	* We don't check the error code - if userspace has
620	* not set up a proper pointer then tough luck.
621	*/
622	put_user(0, tsk->clear_child_tid);
623	sys_futex(tsk->clear_child_tid, FUTEX_WAKE,
624	1, NULL, NULL, 0);
625	}
626	tsk->clear_child_tid = NULL;
627	}
628	}
629
630	/*
631	* Allocate a new mm structure and copy contents from the
632	* mm structure of the passed in task structure.
633	*/
634	struct mm_struct dup_mm(struct task_struct tsk)
635	{
636	struct mm_struct mm, oldmm = current->mm;
637	int err;
638
639	if (!oldmm)
640	return NULL;
641
642	mm = allocate_mm();
643	if (!mm)
644	goto fail_nomem;
645
646	memcpy(mm, oldmm, sizeof(*mm));
647
648	/* Initializing for Swap token stuff */
649	mm->token_priority = 0;
650	mm->last_interval = 0;
651
652	if (!mm_init(mm, tsk))
653	goto fail_nomem;
654
655	if (init_new_context(tsk, mm))
656	goto fail_nocontext;
657
658	dup_mm_exe_file(oldmm, mm);
659
660	err = dup_mmap(mm, oldmm);
661	if (err)
662	goto free_pt;
663
664	mm->hiwater_rss = get_mm_rss(mm);
665	mm->hiwater_vm = mm->total_vm;
666
667	if (mm->binfmt && !try_module_get(mm->binfmt->module))
668	goto free_pt;
669
670	return mm;
671
672	free_pt:
673	/* don't put binfmt in mmput, we haven't got module yet */
674	mm->binfmt = NULL;
675	mmput(mm);
676
677	fail_nomem:
678	return NULL;
679
680	fail_nocontext:
681	/*
682	* If init_new_context() failed, we cannot use mmput() to free the mm
683	* because it calls destroy_context()
684	*/
685	mm_free_pgd(mm);
686	free_mm(mm);
687	return NULL;
688	}
689
690	static int copy_mm(unsigned long clone_flags, struct task_struct * tsk)
691	{
692	struct mm_struct * mm, *oldmm;
693	int retval;
694
695	tsk->min_flt = tsk->maj_flt = 0;
696	tsk->nvcsw = tsk->nivcsw = 0;
697	#ifdef CONFIG_DETECT_HUNG_TASK
698	tsk->last_switch_count = tsk->nvcsw + tsk->nivcsw;
699	#endif
700
701	tsk->mm = NULL;
702	tsk->active_mm = NULL;
703
704	/*
705	* Are we cloning a kernel thread?
706	*
707	* We need to steal a active VM for that..
708	*/
709	oldmm = current->mm;
710	if (!oldmm)
711	return 0;
712
713	if (clone_flags & CLONE_VM) {
714	atomic_inc(&oldmm->mm_users);
715	mm = oldmm;
716	goto good_mm;
717	}
718
719	retval = -ENOMEM;
720	mm = dup_mm(tsk);
721	if (!mm)
722	goto fail_nomem;
723
724	good_mm:
725	/* Initializing for Swap token stuff */
726	mm->token_priority = 0;
727	mm->last_interval = 0;
728
729	tsk->mm = mm;
730	tsk->active_mm = mm;
731	return 0;
732
733	fail_nomem:
734	return retval;
735	}
736
737	static int copy_fs(unsigned long clone_flags, struct task_struct *tsk)
738	{
739	struct fs_struct *fs = current->fs;
740	if (clone_flags & CLONE_FS) {
741	/* tsk->fs is already what we want */
742	write_lock(&fs->lock);
743	if (fs->in_exec) {
744	write_unlock(&fs->lock);
745	return -EAGAIN;
746	}
747	fs->users++;
748	write_unlock(&fs->lock);
749	return 0;
750	}
751	tsk->fs = copy_fs_struct(fs);
752	if (!tsk->fs)
753	return -ENOMEM;
754	return 0;
755	}
756
757	static int copy_files(unsigned long clone_flags, struct task_struct * tsk)
758	{
759	struct files_struct oldf, newf;
760	int error = 0;
761
762	/*
763	* A background process may not have any files ...
764	*/
765	oldf = current->files;
766	if (!oldf)
767	goto out;
768
769	if (clone_flags & CLONE_FILES) {
770	atomic_inc(&oldf->count);
771	goto out;
772	}
773
774	newf = dup_fd(oldf, &error);
775	if (!newf)
776	goto out;
777
778	tsk->files = newf;
779	error = 0;
780	out:
781	return error;
782	}
783
784	static int copy_io(unsigned long clone_flags, struct task_struct *tsk)
785	{
786	#ifdef CONFIG_BLOCK
787	struct io_context *ioc = current->io_context;
788
789	if (!ioc)
790	return 0;
791	/*
792	* Share io context with parent, if CLONE_IO is set
793	*/
794	if (clone_flags & CLONE_IO) {
795	tsk->io_context = ioc_task_link(ioc);
796	if (unlikely(!tsk->io_context))
797	return -ENOMEM;
798	} else if (ioprio_valid(ioc->ioprio)) {
799	tsk->io_context = alloc_io_context(GFP_KERNEL, -1);
800	if (unlikely(!tsk->io_context))
801	return -ENOMEM;
802
803	tsk->io_context->ioprio = ioc->ioprio;
804	}
805	#endif
806	return 0;
807	}
808
809	static int copy_sighand(unsigned long clone_flags, struct task_struct *tsk)
810	{
811	struct sighand_struct *sig;
812
813	if (clone_flags & CLONE_SIGHAND) {
814	atomic_inc(&current->sighand->count);
815	return 0;
816	}
817	sig = kmem_cache_alloc(sighand_cachep, GFP_KERNEL);
818	rcu_assign_pointer(tsk->sighand, sig);
819	if (!sig)
820	return -ENOMEM;
821	atomic_set(&sig->count, 1);
822	memcpy(sig->action, current->sighand->action, sizeof(sig->action));
823	return 0;
824	}
825
826	void __cleanup_sighand(struct sighand_struct *sighand)
827	{
828	if (atomic_dec_and_test(&sighand->count))
829	kmem_cache_free(sighand_cachep, sighand);
830	}
831
832
833	/*
834	* Initialize POSIX timer handling for a thread group.
835	*/
836	static void posix_cpu_timers_init_group(struct signal_struct *sig)
837	{
838	unsigned long cpu_limit;
839
840	/* Thread group counters. */
841	thread_group_cputime_init(sig);
842
843	cpu_limit = ACCESS_ONCE(sig->rlim[RLIMIT_CPU].rlim_cur);
844	if (cpu_limit != RLIM_INFINITY) {
845	sig->cputime_expires.prof_exp = secs_to_cputime(cpu_limit);
846	sig->cputimer.running = 1;
847	}
848
849	/* The timer lists. */
850	INIT_LIST_HEAD(&sig->cpu_timers[0]);
851	INIT_LIST_HEAD(&sig->cpu_timers[1]);
852	INIT_LIST_HEAD(&sig->cpu_timers[2]);
853	}
854
855	static int copy_signal(unsigned long clone_flags, struct task_struct *tsk)
856	{
857	struct signal_struct *sig;
858
859	if (clone_flags & CLONE_THREAD)
860	return 0;
861
862	sig = kmem_cache_zalloc(signal_cachep, GFP_KERNEL);
863	tsk->signal = sig;
864	if (!sig)
865	return -ENOMEM;
866
867	atomic_set(&sig->count, 1);
868	atomic_set(&sig->live, 1);
869	init_waitqueue_head(&sig->wait_chldexit);
870	if (clone_flags & CLONE_NEWPID)
871	sig->flags \|= SIGNAL_UNKILLABLE;
872	sig->curr_target = tsk;
873	init_sigpending(&sig->shared_pending);
874	INIT_LIST_HEAD(&sig->posix_timers);
875
876	hrtimer_init(&sig->real_timer, CLOCK_MONOTONIC, HRTIMER_MODE_REL);
877	sig->real_timer.function = it_real_fn;
878
879	task_lock(current->group_leader);
880	memcpy(sig->rlim, current->signal->rlim, sizeof sig->rlim);
881	task_unlock(current->group_leader);
882
883	posix_cpu_timers_init_group(sig);
884
885	tty_audit_fork(sig);
886
887	sig->oom_adj = current->signal->oom_adj;
888
889	return 0;
890	}
891
892	void __cleanup_signal(struct signal_struct *sig)
893	{
894	thread_group_cputime_free(sig);
895	tty_kref_put(sig->tty);
896	kmem_cache_free(signal_cachep, sig);
897	}
898
899	static void copy_flags(unsigned long clone_flags, struct task_struct *p)
900	{
901	unsigned long new_flags = p->flags;
902
903	new_flags &= ~PF_SUPERPRIV;
904	new_flags \|= PF_FORKNOEXEC;
905	new_flags \|= PF_STARTING;
906	p->flags = new_flags;
907	clear_freeze_flag(p);
908	}
909
910	SYSCALL_DEFINE1(set_tid_address, int __user *, tidptr)
911	{
912	current->clear_child_tid = tidptr;
913
914	return task_pid_vnr(current);
915	}
916
917	static void rt_mutex_init_task(struct task_struct *p)
918	{
919	raw_spin_lock_init(&p->pi_lock);
920	#ifdef CONFIG_RT_MUTEXES
921	plist_head_init_raw(&p->pi_waiters, &p->pi_lock);
922	p->pi_blocked_on = NULL;
923	#endif
924	}
925
926	#ifdef CONFIG_MM_OWNER
927	void mm_init_owner(struct mm_struct mm, struct task_struct p)
928	{
929	mm->owner = p;
930	}
931	#endif /* CONFIG_MM_OWNER */
932
933	/*
934	* Initialize POSIX timer handling for a single task.
935	*/
936	static void posix_cpu_timers_init(struct task_struct *tsk)
937	{
938	tsk->cputime_expires.prof_exp = cputime_zero;
939	tsk->cputime_expires.virt_exp = cputime_zero;
940	tsk->cputime_expires.sched_exp = 0;
941	INIT_LIST_HEAD(&tsk->cpu_timers[0]);
942	INIT_LIST_HEAD(&tsk->cpu_timers[1]);
943	INIT_LIST_HEAD(&tsk->cpu_timers[2]);
944	}
945
946	/*
947	* This creates a new process as a copy of the old one,
948	* but does not actually start it yet.
949	*
950	* It copies the registers, and all the appropriate
951	* parts of the process environment (as per the clone
952	* flags). The actual kick-off is left to the caller.
953	*/
954	static struct task_struct *copy_process(unsigned long clone_flags,
955	unsigned long stack_start,
956	struct pt_regs *regs,
957	unsigned long stack_size,
958	int __user *child_tidptr,
959	struct pid *pid,
960	int trace)
961	{
962	int retval;
963	struct task_struct *p;
964	int cgroup_callbacks_done = 0;
965
966	if ((clone_flags & (CLONE_NEWNS\|CLONE_FS)) == (CLONE_NEWNS\|CLONE_FS))
967	return ERR_PTR(-EINVAL);
968
969	/*
970	* Thread groups must share signals as well, and detached threads
971	* can only be started up within the thread group.
972	*/
973	if ((clone_flags & CLONE_THREAD) && !(clone_flags & CLONE_SIGHAND))
974	return ERR_PTR(-EINVAL);
975
976	/*
977	* Shared signal handlers imply shared VM. By way of the above,
978	* thread groups also imply shared VM. Blocking this case allows
979	* for various simplifications in other code.
980	*/
981	if ((clone_flags & CLONE_SIGHAND) && !(clone_flags & CLONE_VM))
982	return ERR_PTR(-EINVAL);
983
984	/*
985	* Siblings of global init remain as zombies on exit since they are
986	* not reaped by their parent (swapper). To solve this and to avoid
987	* multi-rooted process trees, prevent global and container-inits
988	* from creating siblings.
989	*/
990	if ((clone_flags & CLONE_PARENT) &&
991	current->signal->flags & SIGNAL_UNKILLABLE)
992	return ERR_PTR(-EINVAL);
993
994	retval = security_task_create(clone_flags);
995	if (retval)
996	goto fork_out;
997
998	retval = -ENOMEM;
999	p = dup_task_struct(current);
1000	if (!p)
1001	goto fork_out;
1002
1003	ftrace_graph_init_task(p);
1004
1005	rt_mutex_init_task(p);
1006
1007	#ifdef CONFIG_PROVE_LOCKING
1008	DEBUG_LOCKS_WARN_ON(!p->hardirqs_enabled);
1009	DEBUG_LOCKS_WARN_ON(!p->softirqs_enabled);
1010	#endif
1011	retval = -EAGAIN;
1012	if (atomic_read(&p->real_cred->user->processes) >=
1013	task_rlimit(p, RLIMIT_NPROC)) {
1014	if (!capable(CAP_SYS_ADMIN) && !capable(CAP_SYS_RESOURCE) &&
1015	p->real_cred->user != INIT_USER)
1016	goto bad_fork_free;
1017	}
1018
1019	retval = copy_creds(p, clone_flags);
1020	if (retval < 0)
1021	goto bad_fork_free;
1022
1023	/*
1024	* If multiple threads are within copy_process(), then this check
1025	* triggers too late. This doesn't hurt, the check is only there
1026	* to stop root fork bombs.
1027	*/
1028	retval = -EAGAIN;
1029	if (nr_threads >= max_threads)
1030	goto bad_fork_cleanup_count;
1031
1032	if (!try_module_get(task_thread_info(p)->exec_domain->module))
1033	goto bad_fork_cleanup_count;
1034
1035	p->did_exec = 0;
1036	delayacct_tsk_init(p); /* Must remain after dup_task_struct() */
1037	copy_flags(clone_flags, p);
1038	INIT_LIST_HEAD(&p->children);
1039	INIT_LIST_HEAD(&p->sibling);
1040	rcu_copy_process(p);
1041	p->vfork_done = NULL;
1042	spin_lock_init(&p->alloc_lock);
1043
1044	init_sigpending(&p->pending);
1045
1046	p->utime = cputime_zero;
1047	p->stime = cputime_zero;
1048	p->gtime = cputime_zero;
1049	p->utimescaled = cputime_zero;
1050	p->stimescaled = cputime_zero;
1051	#ifndef CONFIG_VIRT_CPU_ACCOUNTING
1052	p->prev_utime = cputime_zero;
1053	p->prev_stime = cputime_zero;
1054	#endif
1055	#if defined(SPLIT_RSS_COUNTING)
1056	memset(&p->rss_stat, 0, sizeof(p->rss_stat));
1057	#endif
1058
1059	p->default_timer_slack_ns = current->timer_slack_ns;
1060
1061	task_io_accounting_init(&p->ioac);
1062	acct_clear_integrals(p);
1063
1064	posix_cpu_timers_init(p);
1065
1066	p->lock_depth = -1; /* -1 = no lock */
1067	do_posix_clock_monotonic_gettime(&p->start_time);
1068	p->real_start_time = p->start_time;
1069	monotonic_to_bootbased(&p->real_start_time);
1070	p->io_context = NULL;
1071	p->audit_context = NULL;
1072	cgroup_fork(p);
1073	#ifdef CONFIG_NUMA
1074	p->mempolicy = mpol_dup(p->mempolicy);
1075	if (IS_ERR(p->mempolicy)) {
1076	retval = PTR_ERR(p->mempolicy);
1077	p->mempolicy = NULL;
1078	goto bad_fork_cleanup_cgroup;
1079	}
1080	mpol_fix_fork_child_flag(p);
1081	#endif
1082	#ifdef CONFIG_TRACE_IRQFLAGS
1083	p->irq_events = 0;
1084	#ifdef __ARCH_WANT_INTERRUPTS_ON_CTXSW
1085	p->hardirqs_enabled = 1;
1086	#else
1087	p->hardirqs_enabled = 0;
1088	#endif
1089	p->hardirq_enable_ip = 0;
1090	p->hardirq_enable_event = 0;
1091	p->hardirq_disable_ip = _THIS_IP_;
1092	p->hardirq_disable_event = 0;
1093	p->softirqs_enabled = 1;
1094	p->softirq_enable_ip = _THIS_IP_;
1095	p->softirq_enable_event = 0;
1096	p->softirq_disable_ip = 0;
1097	p->softirq_disable_event = 0;
1098	p->hardirq_context = 0;
1099	p->softirq_context = 0;
1100	#endif
1101	#ifdef CONFIG_LOCKDEP
1102	p->lockdep_depth = 0; /* no locks held yet */
1103	p->curr_chain_key = 0;
1104	p->lockdep_recursion = 0;
1105	#endif
1106
1107	#ifdef CONFIG_DEBUG_MUTEXES
1108	p->blocked_on = NULL; /* not blocked yet */
1109	#endif
1110	#ifdef CONFIG_CGROUP_MEM_RES_CTLR
1111	p->memcg_batch.do_batch = 0;
1112	p->memcg_batch.memcg = NULL;
1113	#endif
1114
1115	p->bts = NULL;
1116
1117	p->stack_start = stack_start;
1118
1119	/* Perform scheduler related setup. Assign this task to a CPU. */
1120	sched_fork(p, clone_flags);
1121
1122	retval = perf_event_init_task(p);
1123	if (retval)
1124	goto bad_fork_cleanup_policy;
1125
1126	if ((retval = audit_alloc(p)))
1127	goto bad_fork_cleanup_policy;
1128	/* copy all the process information */
1129	if ((retval = copy_semundo(clone_flags, p)))
1130	goto bad_fork_cleanup_audit;
1131	if ((retval = copy_files(clone_flags, p)))
1132	goto bad_fork_cleanup_semundo;
1133	if ((retval = copy_fs(clone_flags, p)))
1134	goto bad_fork_cleanup_files;
1135	if ((retval = copy_sighand(clone_flags, p)))
1136	goto bad_fork_cleanup_fs;
1137	if ((retval = copy_signal(clone_flags, p)))
1138	goto bad_fork_cleanup_sighand;
1139	if ((retval = copy_mm(clone_flags, p)))
1140	goto bad_fork_cleanup_signal;
1141	if ((retval = copy_namespaces(clone_flags, p)))
1142	goto bad_fork_cleanup_mm;
1143	if ((retval = copy_io(clone_flags, p)))
1144	goto bad_fork_cleanup_namespaces;
1145	retval = copy_thread(clone_flags, stack_start, stack_size, p, regs);
1146	if (retval)
1147	goto bad_fork_cleanup_io;
1148
1149	if (pid != &init_struct_pid) {
1150	retval = -ENOMEM;
1151	pid = alloc_pid(p->nsproxy->pid_ns);
1152	if (!pid)
1153	goto bad_fork_cleanup_io;
1154
1155	if (clone_flags & CLONE_NEWPID) {
1156	retval = pid_ns_prepare_proc(p->nsproxy->pid_ns);
1157	if (retval < 0)
1158	goto bad_fork_free_pid;
1159	}
1160	}
1161
1162	p->pid = pid_nr(pid);
1163	p->tgid = p->pid;
1164	if (clone_flags & CLONE_THREAD)
1165	p->tgid = current->tgid;
1166
1167	if (current->nsproxy != p->nsproxy) {
1168	retval = ns_cgroup_clone(p, pid);
1169	if (retval)
1170	goto bad_fork_free_pid;
1171	}
1172
1173	p->set_child_tid = (clone_flags & CLONE_CHILD_SETTID) ? child_tidptr : NULL;
1174	/*
1175	* Clear TID on mm_release()?
1176	*/
1177	p->clear_child_tid = (clone_flags & CLONE_CHILD_CLEARTID) ? child_tidptr: NULL;
1178	#ifdef CONFIG_FUTEX
1179	p->robust_list = NULL;
1180	#ifdef CONFIG_COMPAT
1181	p->compat_robust_list = NULL;
1182	#endif
1183	INIT_LIST_HEAD(&p->pi_state_list);
1184	p->pi_state_cache = NULL;
1185	#endif
1186	/*
1187	* sigaltstack should be cleared when sharing the same VM
1188	*/
1189	if ((clone_flags & (CLONE_VM\|CLONE_VFORK)) == CLONE_VM)
1190	p->sas_ss_sp = p->sas_ss_size = 0;
1191
1192	/*
1193	* Syscall tracing and stepping should be turned off in the
1194	* child regardless of CLONE_PTRACE.
1195	*/
1196	user_disable_single_step(p);
1197	clear_tsk_thread_flag(p, TIF_SYSCALL_TRACE);
1198	#ifdef TIF_SYSCALL_EMU
1199	clear_tsk_thread_flag(p, TIF_SYSCALL_EMU);
1200	#endif
1201	clear_all_latency_tracing(p);
1202
1203	/* ok, now we should be set up.. */
1204	p->exit_signal = (clone_flags & CLONE_THREAD) ? -1 : (clone_flags & CSIGNAL);
1205	p->pdeath_signal = 0;
1206	p->exit_state = 0;
1207
1208	/*
1209	* Ok, make it visible to the rest of the system.
1210	* We dont wake it up yet.
1211	*/
1212	p->group_leader = p;
1213	INIT_LIST_HEAD(&p->thread_group);
1214
1215	/* Now that the task is set up, run cgroup callbacks if
1216	* necessary. We need to run them before the task is visible
1217	* on the tasklist. */
1218	cgroup_fork_callbacks(p);
1219	cgroup_callbacks_done = 1;
1220
1221	/* Need tasklist lock for parent etc handling! */
1222	write_lock_irq(&tasklist_lock);
1223
1224	/* CLONE_PARENT re-uses the old parent */
1225	if (clone_flags & (CLONE_PARENT\|CLONE_THREAD)) {
1226	p->real_parent = current->real_parent;
1227	p->parent_exec_id = current->parent_exec_id;
1228	} else {
1229	p->real_parent = current;
1230	p->parent_exec_id = current->self_exec_id;
1231	}
1232
1233	spin_lock(&current->sighand->siglock);
1234
1235	/*
1236	* Process group and session signals need to be delivered to just the
1237	* parent before the fork or both the parent and the child after the
1238	* fork. Restart if a signal comes in before we add the new process to
1239	* it's process group.
1240	* A fatal signal pending means that current will exit, so the new
1241	* thread can't slip out of an OOM kill (or normal SIGKILL).
1242	*/
1243	recalc_sigpending();
1244	if (signal_pending(current)) {
1245	spin_unlock(&current->sighand->siglock);
1246	write_unlock_irq(&tasklist_lock);
1247	retval = -ERESTARTNOINTR;
1248	goto bad_fork_free_pid;
1249	}
1250
1251	if (clone_flags & CLONE_THREAD) {
1252	atomic_inc(&current->signal->count);
1253	atomic_inc(&current->signal->live);
1254	p->group_leader = current->group_leader;
1255	list_add_tail_rcu(&p->thread_group, &p->group_leader->thread_group);
1256	}
1257
1258	if (likely(p->pid)) {
1259	tracehook_finish_clone(p, clone_flags, trace);
1260
1261	if (thread_group_leader(p)) {
1262	if (clone_flags & CLONE_NEWPID)
1263	p->nsproxy->pid_ns->child_reaper = p;
1264
1265	p->signal->leader_pid = pid;
1266	tty_kref_put(p->signal->tty);
1267	p->signal->tty = tty_kref_get(current->signal->tty);
1268	attach_pid(p, PIDTYPE_PGID, task_pgrp(current));
1269	attach_pid(p, PIDTYPE_SID, task_session(current));
1270	list_add_tail(&p->sibling, &p->real_parent->children);
1271	list_add_tail_rcu(&p->tasks, &init_task.tasks);
1272	__get_cpu_var(process_counts)++;
1273	}
1274	attach_pid(p, PIDTYPE_PID, pid);
1275	nr_threads++;
1276	}
1277
1278	total_forks++;
1279	spin_unlock(&current->sighand->siglock);
1280	write_unlock_irq(&tasklist_lock);
1281	proc_fork_connector(p);
1282	cgroup_post_fork(p);
1283	perf_event_fork(p);
1284	return p;
1285
1286	bad_fork_free_pid:
1287	if (pid != &init_struct_pid)
1288	free_pid(pid);
1289	bad_fork_cleanup_io:
1290	if (p->io_context)
1291	exit_io_context(p);
1292	bad_fork_cleanup_namespaces:
1293	exit_task_namespaces(p);
1294	bad_fork_cleanup_mm:
1295	if (p->mm)
1296	mmput(p->mm);
1297	bad_fork_cleanup_signal:
1298	if (!(clone_flags & CLONE_THREAD))
1299	__cleanup_signal(p->signal);
1300	bad_fork_cleanup_sighand:
1301	__cleanup_sighand(p->sighand);
1302	bad_fork_cleanup_fs:
1303	exit_fs(p); /* blocking */
1304	bad_fork_cleanup_files:
1305	exit_files(p); /* blocking */
1306	bad_fork_cleanup_semundo:
1307	exit_sem(p);
1308	bad_fork_cleanup_audit:
1309	audit_free(p);
1310	bad_fork_cleanup_policy:
1311	perf_event_free_task(p);
1312	#ifdef CONFIG_NUMA
1313	mpol_put(p->mempolicy);
1314	bad_fork_cleanup_cgroup:
1315	#endif
1316	cgroup_exit(p, cgroup_callbacks_done);
1317	delayacct_tsk_free(p);
1318	module_put(task_thread_info(p)->exec_domain->module);
1319	bad_fork_cleanup_count:
1320	atomic_dec(&p->cred->user->processes);
1321	exit_creds(p);
1322	bad_fork_free:
1323	free_task(p);
1324	fork_out:
1325	return ERR_PTR(retval);
1326	}
1327
1328	noinline struct pt_regs * __cpuinit __attribute__((weak)) idle_regs(struct pt_regs *regs)
1329	{
1330	memset(regs, 0, sizeof(struct pt_regs));
1331	return regs;
1332	}
1333
1334	struct task_struct * __cpuinit fork_idle(int cpu)
1335	{
1336	struct task_struct *task;
1337	struct pt_regs regs;
1338
1339	task = copy_process(CLONE_VM, 0, idle_regs(&regs), 0, NULL,
1340	&init_struct_pid, 0);
1341	if (!IS_ERR(task))
1342	init_idle(task, cpu);
1343
1344	return task;
1345	}
1346
1347	/*
1348	* Ok, this is the main fork-routine.
1349	*
1350	* It copies the process, and if successful kick-starts
1351	* it and waits for it to finish using the VM if required.
1352	*/
1353	long do_fork(unsigned long clone_flags,
1354	unsigned long stack_start,
1355	struct pt_regs *regs,
1356	unsigned long stack_size,
1357	int __user *parent_tidptr,
1358	int __user *child_tidptr)
1359	{
1360	struct task_struct *p;
1361	int trace = 0;
1362	long nr;
1363
1364	/*
1365	* Do some preliminary argument and permissions checking before we
1366	* actually start allocating stuff
1367	*/
1368	if (clone_flags & CLONE_NEWUSER) {
1369	if (clone_flags & CLONE_THREAD)
1370	return -EINVAL;
1371	/* hopefully this check will go away when userns support is
1372	* complete
1373	*/
1374	if (!capable(CAP_SYS_ADMIN) \|\| !capable(CAP_SETUID) \|\|
1375	!capable(CAP_SETGID))
1376	return -EPERM;
1377	}
1378
1379	/*
1380	* We hope to recycle these flags after 2.6.26
1381	*/
1382	if (unlikely(clone_flags & CLONE_STOPPED)) {
1383	static int __read_mostly count = 100;
1384
1385	if (count > 0 && printk_ratelimit()) {
1386	char comm[TASK_COMM_LEN];
1387
1388	count--;
1389	printk(KERN_INFO "fork(): process `%s' used deprecated "
1390	"clone flags 0x%lx\n",
1391	get_task_comm(comm, current),
1392	clone_flags & CLONE_STOPPED);
1393	}
1394	}
1395
1396	/*
1397	* When called from kernel_thread, don't do user tracing stuff.
1398	*/
1399	if (likely(user_mode(regs)))
1400	trace = tracehook_prepare_clone(clone_flags);
1401
1402	p = copy_process(clone_flags, stack_start, regs, stack_size,
1403	child_tidptr, NULL, trace);
1404	/*
1405	* Do this prior waking up the new thread - the thread pointer
1406	* might get invalid after that point, if the thread exits quickly.
1407	*/
1408	if (!IS_ERR(p)) {
1409	struct completion vfork;
1410
1411	trace_sched_process_fork(current, p);
1412
1413	nr = task_pid_vnr(p);
1414
1415	if (clone_flags & CLONE_PARENT_SETTID)
1416	put_user(nr, parent_tidptr);
1417
1418	if (clone_flags & CLONE_VFORK) {
1419	p->vfork_done = &vfork;
1420	init_completion(&vfork);
1421	}
1422
1423	audit_finish_fork(p);
1424	tracehook_report_clone(regs, clone_flags, nr, p);
1425
1426	/*
1427	* We set PF_STARTING at creation in case tracing wants to
1428	* use this to distinguish a fully live task from one that
1429	* hasn't gotten to tracehook_report_clone() yet. Now we
1430	* clear it and set the child going.
1431	*/
1432	p->flags &= ~PF_STARTING;
1433
1434	if (unlikely(clone_flags & CLONE_STOPPED)) {
1435	/*
1436	* We'll start up with an immediate SIGSTOP.
1437	*/
1438	sigaddset(&p->pending.signal, SIGSTOP);
1439	set_tsk_thread_flag(p, TIF_SIGPENDING);
1440	__set_task_state(p, TASK_STOPPED);
1441	} else {
1442	wake_up_new_task(p, clone_flags);
1443	}
1444
1445	tracehook_report_clone_complete(trace, regs,
1446	clone_flags, nr, p);
1447
1448	if (clone_flags & CLONE_VFORK) {
1449	freezer_do_not_count();
1450	wait_for_completion(&vfork);
1451	freezer_count();
1452	tracehook_report_vfork_done(p, nr);
1453	}
1454	} else {
1455	nr = PTR_ERR(p);
1456	}
1457	return nr;
1458	}
1459
1460	#ifndef ARCH_MIN_MMSTRUCT_ALIGN
1461	#define ARCH_MIN_MMSTRUCT_ALIGN 0
1462	#endif
1463
1464	static void sighand_ctor(void *data)
1465	{
1466	struct sighand_struct *sighand = data;
1467
1468	spin_lock_init(&sighand->siglock);
1469	init_waitqueue_head(&sighand->signalfd_wqh);
1470	}
1471
1472	void __init proc_caches_init(void)
1473	{
1474	sighand_cachep = kmem_cache_create("sighand_cache",
1475	sizeof(struct sighand_struct), 0,
1476	SLAB_HWCACHE_ALIGN\|SLAB_PANIC\|SLAB_DESTROY_BY_RCU\|
1477	SLAB_NOTRACK, sighand_ctor);
1478	signal_cachep = kmem_cache_create("signal_cache",
1479	sizeof(struct signal_struct), 0,
1480	SLAB_HWCACHE_ALIGN\|SLAB_PANIC\|SLAB_NOTRACK, NULL);
1481	files_cachep = kmem_cache_create("files_cache",
1482	sizeof(struct files_struct), 0,
1483	SLAB_HWCACHE_ALIGN\|SLAB_PANIC\|SLAB_NOTRACK, NULL);
1484	fs_cachep = kmem_cache_create("fs_cache",
1485	sizeof(struct fs_struct), 0,
1486	SLAB_HWCACHE_ALIGN\|SLAB_PANIC\|SLAB_NOTRACK, NULL);
1487	mm_cachep = kmem_cache_create("mm_struct",
1488	sizeof(struct mm_struct), ARCH_MIN_MMSTRUCT_ALIGN,
1489	SLAB_HWCACHE_ALIGN\|SLAB_PANIC\|SLAB_NOTRACK, NULL);
1490	vm_area_cachep = KMEM_CACHE(vm_area_struct, SLAB_PANIC);
1491	mmap_init();
1492	}
1493
1494	/*
1495	* Check constraints on flags passed to the unshare system call and
1496	* force unsharing of additional process context as appropriate.
1497	*/
1498	static void check_unshare_flags(unsigned long *flags_ptr)
1499	{
1500	/*
1501	* If unsharing a thread from a thread group, must also
1502	* unshare vm.
1503	*/
1504	if (*flags_ptr & CLONE_THREAD)
1505	*flags_ptr \|= CLONE_VM;
1506
1507	/*
1508	* If unsharing vm, must also unshare signal handlers.
1509	*/
1510	if (*flags_ptr & CLONE_VM)
1511	*flags_ptr \|= CLONE_SIGHAND;
1512
1513	/*
1514	* If unsharing signal handlers and the task was created
1515	* using CLONE_THREAD, then must unshare the thread
1516	*/
1517	if ((*flags_ptr & CLONE_SIGHAND) &&
1518	(atomic_read(&current->signal->count) > 1))
1519	*flags_ptr \|= CLONE_THREAD;
1520
1521	/*
1522	* If unsharing namespace, must also unshare filesystem information.
1523	*/
1524	if (*flags_ptr & CLONE_NEWNS)
1525	*flags_ptr \|= CLONE_FS;
1526	}
1527
1528	/*
1529	* Unsharing of tasks created with CLONE_THREAD is not supported yet
1530	*/
1531	static int unshare_thread(unsigned long unshare_flags)
1532	{
1533	if (unshare_flags & CLONE_THREAD)
1534	return -EINVAL;
1535
1536	return 0;
1537	}
1538
1539	/*
1540	* Unshare the filesystem structure if it is being shared
1541	*/
1542	static int unshare_fs(unsigned long unshare_flags, struct fs_struct **new_fsp)
1543	{
1544	struct fs_struct *fs = current->fs;
1545
1546	if (!(unshare_flags & CLONE_FS) \|\| !fs)
1547	return 0;
1548
1549	/* don't need lock here; in the worst case we'll do useless copy */
1550	if (fs->users == 1)
1551	return 0;
1552
1553	*new_fsp = copy_fs_struct(fs);
1554	if (!*new_fsp)
1555	return -ENOMEM;
1556
1557	return 0;
1558	}
1559
1560	/*
1561	* Unsharing of sighand is not supported yet
1562	*/
1563	static int unshare_sighand(unsigned long unshare_flags, struct sighand_struct **new_sighp)
1564	{
1565	struct sighand_struct *sigh = current->sighand;
1566
1567	if ((unshare_flags & CLONE_SIGHAND) && atomic_read(&sigh->count) > 1)
1568	return -EINVAL;
1569	else
1570	return 0;
1571	}
1572
1573	/*
1574	* Unshare vm if it is being shared
1575	*/
1576	static int unshare_vm(unsigned long unshare_flags, struct mm_struct **new_mmp)
1577	{
1578	struct mm_struct *mm = current->mm;
1579
1580	if ((unshare_flags & CLONE_VM) &&
1581	(mm && atomic_read(&mm->mm_users) > 1)) {
1582	return -EINVAL;
1583	}
1584
1585	return 0;
1586	}
1587
1588	/*
1589	* Unshare file descriptor table if it is being shared
1590	*/
1591	static int unshare_fd(unsigned long unshare_flags, struct files_struct **new_fdp)
1592	{
1593	struct files_struct *fd = current->files;
1594	int error = 0;
1595
1596	if ((unshare_flags & CLONE_FILES) &&
1597	(fd && atomic_read(&fd->count) > 1)) {
1598	*new_fdp = dup_fd(fd, &error);
1599	if (!*new_fdp)
1600	return error;
1601	}
1602
1603	return 0;
1604	}
1605
1606	/*
1607	* unshare allows a process to 'unshare' part of the process
1608	* context which was originally shared using clone. copy_*
1609	* functions used by do_fork() cannot be used here directly
1610	* because they modify an inactive task_struct that is being
1611	* constructed. Here we are modifying the current, active,
1612	* task_struct.
1613	*/
1614	SYSCALL_DEFINE1(unshare, unsigned long, unshare_flags)
1615	{
1616	int err = 0;
1617	struct fs_struct fs, new_fs = NULL;
1618	struct sighand_struct *new_sigh = NULL;
1619	struct mm_struct mm, new_mm = NULL, *active_mm = NULL;
1620	struct files_struct fd, new_fd = NULL;
1621	struct nsproxy *new_nsproxy = NULL;
1622	int do_sysvsem = 0;
1623
1624	check_unshare_flags(&unshare_flags);
1625
1626	/* Return -EINVAL for all unsupported flags */
1627	err = -EINVAL;
1628	if (unshare_flags & ~(CLONE_THREAD\|CLONE_FS\|CLONE_NEWNS\|CLONE_SIGHAND\|
1629	CLONE_VM\|CLONE_FILES\|CLONE_SYSVSEM\|
1630	CLONE_NEWUTS\|CLONE_NEWIPC\|CLONE_NEWNET))
1631	goto bad_unshare_out;
1632
1633	/*
1634	* CLONE_NEWIPC must also detach from the undolist: after switching
1635	* to a new ipc namespace, the semaphore arrays from the old
1636	* namespace are unreachable.
1637	*/
1638	if (unshare_flags & (CLONE_NEWIPC\|CLONE_SYSVSEM))
1639	do_sysvsem = 1;
1640	if ((err = unshare_thread(unshare_flags)))
1641	goto bad_unshare_out;
1642	if ((err = unshare_fs(unshare_flags, &new_fs)))
1643	goto bad_unshare_cleanup_thread;
1644	if ((err = unshare_sighand(unshare_flags, &new_sigh)))
1645	goto bad_unshare_cleanup_fs;
1646	if ((err = unshare_vm(unshare_flags, &new_mm)))
1647	goto bad_unshare_cleanup_sigh;
1648	if ((err = unshare_fd(unshare_flags, &new_fd)))
1649	goto bad_unshare_cleanup_vm;
1650	if ((err = unshare_nsproxy_namespaces(unshare_flags, &new_nsproxy,
1651	new_fs)))
1652	goto bad_unshare_cleanup_fd;
1653
1654	if (new_fs \|\| new_mm \|\| new_fd \|\| do_sysvsem \|\| new_nsproxy) {
1655	if (do_sysvsem) {
1656	/*
1657	* CLONE_SYSVSEM is equivalent to sys_exit().
1658	*/
1659	exit_sem(current);
1660	}
1661
1662	if (new_nsproxy) {
1663	switch_task_namespaces(current, new_nsproxy);
1664	new_nsproxy = NULL;
1665	}
1666
1667	task_lock(current);
1668
1669	if (new_fs) {
1670	fs = current->fs;
1671	write_lock(&fs->lock);
1672	current->fs = new_fs;
1673	if (--fs->users)
1674	new_fs = NULL;
1675	else
1676	new_fs = fs;
1677	write_unlock(&fs->lock);
1678	}
1679
1680	if (new_mm) {
1681	mm = current->mm;
1682	active_mm = current->active_mm;
1683	current->mm = new_mm;
1684	current->active_mm = new_mm;
1685	activate_mm(active_mm, new_mm);
1686	new_mm = mm;
1687	}
1688
1689	if (new_fd) {
1690	fd = current->files;
1691	current->files = new_fd;
1692	new_fd = fd;
1693	}
1694
1695	task_unlock(current);
1696	}
1697
1698	if (new_nsproxy)
1699	put_nsproxy(new_nsproxy);
1700
1701	bad_unshare_cleanup_fd:
1702	if (new_fd)
1703	put_files_struct(new_fd);
1704
1705	bad_unshare_cleanup_vm:
1706	if (new_mm)
1707	mmput(new_mm);
1708
1709	bad_unshare_cleanup_sigh:
1710	if (new_sigh)
1711	if (atomic_dec_and_test(&new_sigh->count))
1712	kmem_cache_free(sighand_cachep, new_sigh);
1713
1714	bad_unshare_cleanup_fs:
1715	if (new_fs)
1716	free_fs_struct(new_fs);
1717
1718	bad_unshare_cleanup_thread:
1719	bad_unshare_out:
1720	return err;
1721	}
1722
1723	/*
1724	* Helper to unshare the files of the current task.
1725	* We don't want to expose copy_files internals to
1726	* the exec layer of the kernel.
1727	*/
1728
1729	int unshare_files(struct files_struct **displaced)
1730	{
1731	struct task_struct *task = current;
1732	struct files_struct *copy = NULL;
1733	int error;
1734
1735	error = unshare_fd(CLONE_FILES, &copy);
1736	if (error \|\| !copy) {
1737	*displaced = NULL;
1738	return error;
1739	}
1740	*displaced = task->files;
1741	task_lock(task);
1742	task->files = copy;
1743	task_unlock(task);
1744	return 0;
1745	}
1746

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