xref: /openbmc/linux/kernel/fork.c (revision 4800cd83)
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 #include <linux/oom.h>
69 #include <linux/khugepaged.h>
70 
71 #include <asm/pgtable.h>
72 #include <asm/pgalloc.h>
73 #include <asm/uaccess.h>
74 #include <asm/mmu_context.h>
75 #include <asm/cacheflush.h>
76 #include <asm/tlbflush.h>
77 
78 #include <trace/events/sched.h>
79 
80 /*
81  * Protected counters by write_lock_irq(&tasklist_lock)
82  */
83 unsigned long total_forks;	/* Handle normal Linux uptimes. */
84 int nr_threads; 		/* The idle threads do not count.. */
85 
86 int max_threads;		/* tunable limit on nr_threads */
87 
88 DEFINE_PER_CPU(unsigned long, process_counts) = 0;
89 
90 __cacheline_aligned DEFINE_RWLOCK(tasklist_lock);  /* outer */
91 
92 #ifdef CONFIG_PROVE_RCU
93 int lockdep_tasklist_lock_is_held(void)
94 {
95 	return lockdep_is_held(&tasklist_lock);
96 }
97 EXPORT_SYMBOL_GPL(lockdep_tasklist_lock_is_held);
98 #endif /* #ifdef CONFIG_PROVE_RCU */
99 
100 int nr_processes(void)
101 {
102 	int cpu;
103 	int total = 0;
104 
105 	for_each_possible_cpu(cpu)
106 		total += per_cpu(process_counts, cpu);
107 
108 	return total;
109 }
110 
111 #ifndef __HAVE_ARCH_TASK_STRUCT_ALLOCATOR
112 # define alloc_task_struct()	kmem_cache_alloc(task_struct_cachep, GFP_KERNEL)
113 # define free_task_struct(tsk)	kmem_cache_free(task_struct_cachep, (tsk))
114 static struct kmem_cache *task_struct_cachep;
115 #endif
116 
117 #ifndef __HAVE_ARCH_THREAD_INFO_ALLOCATOR
118 static inline struct thread_info *alloc_thread_info(struct task_struct *tsk)
119 {
120 #ifdef CONFIG_DEBUG_STACK_USAGE
121 	gfp_t mask = GFP_KERNEL | __GFP_ZERO;
122 #else
123 	gfp_t mask = GFP_KERNEL;
124 #endif
125 	return (struct thread_info *)__get_free_pages(mask, THREAD_SIZE_ORDER);
126 }
127 
128 static inline void free_thread_info(struct thread_info *ti)
129 {
130 	free_pages((unsigned long)ti, THREAD_SIZE_ORDER);
131 }
132 #endif
133 
134 /* SLAB cache for signal_struct structures (tsk->signal) */
135 static struct kmem_cache *signal_cachep;
136 
137 /* SLAB cache for sighand_struct structures (tsk->sighand) */
138 struct kmem_cache *sighand_cachep;
139 
140 /* SLAB cache for files_struct structures (tsk->files) */
141 struct kmem_cache *files_cachep;
142 
143 /* SLAB cache for fs_struct structures (tsk->fs) */
144 struct kmem_cache *fs_cachep;
145 
146 /* SLAB cache for vm_area_struct structures */
147 struct kmem_cache *vm_area_cachep;
148 
149 /* SLAB cache for mm_struct structures (tsk->mm) */
150 static struct kmem_cache *mm_cachep;
151 
152 static void account_kernel_stack(struct thread_info *ti, int account)
153 {
154 	struct zone *zone = page_zone(virt_to_page(ti));
155 
156 	mod_zone_page_state(zone, NR_KERNEL_STACK, account);
157 }
158 
159 void free_task(struct task_struct *tsk)
160 {
161 	prop_local_destroy_single(&tsk->dirties);
162 	account_kernel_stack(tsk->stack, -1);
163 	free_thread_info(tsk->stack);
164 	rt_mutex_debug_task_free(tsk);
165 	ftrace_graph_exit_task(tsk);
166 	free_task_struct(tsk);
167 }
168 EXPORT_SYMBOL(free_task);
169 
170 static inline void free_signal_struct(struct signal_struct *sig)
171 {
172 	taskstats_tgid_free(sig);
173 	sched_autogroup_exit(sig);
174 	kmem_cache_free(signal_cachep, sig);
175 }
176 
177 static inline void put_signal_struct(struct signal_struct *sig)
178 {
179 	if (atomic_dec_and_test(&sig->sigcnt))
180 		free_signal_struct(sig);
181 }
182 
183 void __put_task_struct(struct task_struct *tsk)
184 {
185 	WARN_ON(!tsk->exit_state);
186 	WARN_ON(atomic_read(&tsk->usage));
187 	WARN_ON(tsk == current);
188 
189 	exit_creds(tsk);
190 	delayacct_tsk_free(tsk);
191 	put_signal_struct(tsk->signal);
192 
193 	if (!profile_handoff_task(tsk))
194 		free_task(tsk);
195 }
196 
197 /*
198  * macro override instead of weak attribute alias, to workaround
199  * gcc 4.1.0 and 4.1.1 bugs with weak attribute and empty functions.
200  */
201 #ifndef arch_task_cache_init
202 #define arch_task_cache_init()
203 #endif
204 
205 void __init fork_init(unsigned long mempages)
206 {
207 #ifndef __HAVE_ARCH_TASK_STRUCT_ALLOCATOR
208 #ifndef ARCH_MIN_TASKALIGN
209 #define ARCH_MIN_TASKALIGN	L1_CACHE_BYTES
210 #endif
211 	/* create a slab on which task_structs can be allocated */
212 	task_struct_cachep =
213 		kmem_cache_create("task_struct", sizeof(struct task_struct),
214 			ARCH_MIN_TASKALIGN, SLAB_PANIC | SLAB_NOTRACK, NULL);
215 #endif
216 
217 	/* do the arch specific task caches init */
218 	arch_task_cache_init();
219 
220 	/*
221 	 * The default maximum number of threads is set to a safe
222 	 * value: the thread structures can take up at most half
223 	 * of memory.
224 	 */
225 	max_threads = mempages / (8 * THREAD_SIZE / PAGE_SIZE);
226 
227 	/*
228 	 * we need to allow at least 20 threads to boot a system
229 	 */
230 	if(max_threads < 20)
231 		max_threads = 20;
232 
233 	init_task.signal->rlim[RLIMIT_NPROC].rlim_cur = max_threads/2;
234 	init_task.signal->rlim[RLIMIT_NPROC].rlim_max = max_threads/2;
235 	init_task.signal->rlim[RLIMIT_SIGPENDING] =
236 		init_task.signal->rlim[RLIMIT_NPROC];
237 }
238 
239 int __attribute__((weak)) arch_dup_task_struct(struct task_struct *dst,
240 					       struct task_struct *src)
241 {
242 	*dst = *src;
243 	return 0;
244 }
245 
246 static struct task_struct *dup_task_struct(struct task_struct *orig)
247 {
248 	struct task_struct *tsk;
249 	struct thread_info *ti;
250 	unsigned long *stackend;
251 
252 	int err;
253 
254 	prepare_to_copy(orig);
255 
256 	tsk = alloc_task_struct();
257 	if (!tsk)
258 		return NULL;
259 
260 	ti = alloc_thread_info(tsk);
261 	if (!ti) {
262 		free_task_struct(tsk);
263 		return NULL;
264 	}
265 
266  	err = arch_dup_task_struct(tsk, orig);
267 	if (err)
268 		goto out;
269 
270 	tsk->stack = ti;
271 
272 	err = prop_local_init_single(&tsk->dirties);
273 	if (err)
274 		goto out;
275 
276 	setup_thread_stack(tsk, orig);
277 	clear_user_return_notifier(tsk);
278 	clear_tsk_need_resched(tsk);
279 	stackend = end_of_stack(tsk);
280 	*stackend = STACK_END_MAGIC;	/* for overflow detection */
281 
282 #ifdef CONFIG_CC_STACKPROTECTOR
283 	tsk->stack_canary = get_random_int();
284 #endif
285 
286 	/* One for us, one for whoever does the "release_task()" (usually parent) */
287 	atomic_set(&tsk->usage,2);
288 	atomic_set(&tsk->fs_excl, 0);
289 #ifdef CONFIG_BLK_DEV_IO_TRACE
290 	tsk->btrace_seq = 0;
291 #endif
292 	tsk->splice_pipe = NULL;
293 
294 	account_kernel_stack(ti, 1);
295 
296 	return tsk;
297 
298 out:
299 	free_thread_info(ti);
300 	free_task_struct(tsk);
301 	return NULL;
302 }
303 
304 #ifdef CONFIG_MMU
305 static int dup_mmap(struct mm_struct *mm, struct mm_struct *oldmm)
306 {
307 	struct vm_area_struct *mpnt, *tmp, *prev, **pprev;
308 	struct rb_node **rb_link, *rb_parent;
309 	int retval;
310 	unsigned long charge;
311 	struct mempolicy *pol;
312 
313 	down_write(&oldmm->mmap_sem);
314 	flush_cache_dup_mm(oldmm);
315 	/*
316 	 * Not linked in yet - no deadlock potential:
317 	 */
318 	down_write_nested(&mm->mmap_sem, SINGLE_DEPTH_NESTING);
319 
320 	mm->locked_vm = 0;
321 	mm->mmap = NULL;
322 	mm->mmap_cache = NULL;
323 	mm->free_area_cache = oldmm->mmap_base;
324 	mm->cached_hole_size = ~0UL;
325 	mm->map_count = 0;
326 	cpumask_clear(mm_cpumask(mm));
327 	mm->mm_rb = RB_ROOT;
328 	rb_link = &mm->mm_rb.rb_node;
329 	rb_parent = NULL;
330 	pprev = &mm->mmap;
331 	retval = ksm_fork(mm, oldmm);
332 	if (retval)
333 		goto out;
334 	retval = khugepaged_fork(mm, oldmm);
335 	if (retval)
336 		goto out;
337 
338 	prev = NULL;
339 	for (mpnt = oldmm->mmap; mpnt; mpnt = mpnt->vm_next) {
340 		struct file *file;
341 
342 		if (mpnt->vm_flags & VM_DONTCOPY) {
343 			long pages = vma_pages(mpnt);
344 			mm->total_vm -= pages;
345 			vm_stat_account(mm, mpnt->vm_flags, mpnt->vm_file,
346 								-pages);
347 			continue;
348 		}
349 		charge = 0;
350 		if (mpnt->vm_flags & VM_ACCOUNT) {
351 			unsigned int len = (mpnt->vm_end - mpnt->vm_start) >> PAGE_SHIFT;
352 			if (security_vm_enough_memory(len))
353 				goto fail_nomem;
354 			charge = len;
355 		}
356 		tmp = kmem_cache_alloc(vm_area_cachep, GFP_KERNEL);
357 		if (!tmp)
358 			goto fail_nomem;
359 		*tmp = *mpnt;
360 		INIT_LIST_HEAD(&tmp->anon_vma_chain);
361 		pol = mpol_dup(vma_policy(mpnt));
362 		retval = PTR_ERR(pol);
363 		if (IS_ERR(pol))
364 			goto fail_nomem_policy;
365 		vma_set_policy(tmp, pol);
366 		tmp->vm_mm = mm;
367 		if (anon_vma_fork(tmp, mpnt))
368 			goto fail_nomem_anon_vma_fork;
369 		tmp->vm_flags &= ~VM_LOCKED;
370 		tmp->vm_next = tmp->vm_prev = NULL;
371 		file = tmp->vm_file;
372 		if (file) {
373 			struct inode *inode = file->f_path.dentry->d_inode;
374 			struct address_space *mapping = file->f_mapping;
375 
376 			get_file(file);
377 			if (tmp->vm_flags & VM_DENYWRITE)
378 				atomic_dec(&inode->i_writecount);
379 			spin_lock(&mapping->i_mmap_lock);
380 			if (tmp->vm_flags & VM_SHARED)
381 				mapping->i_mmap_writable++;
382 			tmp->vm_truncate_count = mpnt->vm_truncate_count;
383 			flush_dcache_mmap_lock(mapping);
384 			/* insert tmp into the share list, just after mpnt */
385 			vma_prio_tree_add(tmp, mpnt);
386 			flush_dcache_mmap_unlock(mapping);
387 			spin_unlock(&mapping->i_mmap_lock);
388 		}
389 
390 		/*
391 		 * Clear hugetlb-related page reserves for children. This only
392 		 * affects MAP_PRIVATE mappings. Faults generated by the child
393 		 * are not guaranteed to succeed, even if read-only
394 		 */
395 		if (is_vm_hugetlb_page(tmp))
396 			reset_vma_resv_huge_pages(tmp);
397 
398 		/*
399 		 * Link in the new vma and copy the page table entries.
400 		 */
401 		*pprev = tmp;
402 		pprev = &tmp->vm_next;
403 		tmp->vm_prev = prev;
404 		prev = tmp;
405 
406 		__vma_link_rb(mm, tmp, rb_link, rb_parent);
407 		rb_link = &tmp->vm_rb.rb_right;
408 		rb_parent = &tmp->vm_rb;
409 
410 		mm->map_count++;
411 		retval = copy_page_range(mm, oldmm, mpnt);
412 
413 		if (tmp->vm_ops && tmp->vm_ops->open)
414 			tmp->vm_ops->open(tmp);
415 
416 		if (retval)
417 			goto out;
418 	}
419 	/* a new mm has just been created */
420 	arch_dup_mmap(oldmm, mm);
421 	retval = 0;
422 out:
423 	up_write(&mm->mmap_sem);
424 	flush_tlb_mm(oldmm);
425 	up_write(&oldmm->mmap_sem);
426 	return retval;
427 fail_nomem_anon_vma_fork:
428 	mpol_put(pol);
429 fail_nomem_policy:
430 	kmem_cache_free(vm_area_cachep, tmp);
431 fail_nomem:
432 	retval = -ENOMEM;
433 	vm_unacct_memory(charge);
434 	goto out;
435 }
436 
437 static inline int mm_alloc_pgd(struct mm_struct * mm)
438 {
439 	mm->pgd = pgd_alloc(mm);
440 	if (unlikely(!mm->pgd))
441 		return -ENOMEM;
442 	return 0;
443 }
444 
445 static inline void mm_free_pgd(struct mm_struct * mm)
446 {
447 	pgd_free(mm, mm->pgd);
448 }
449 #else
450 #define dup_mmap(mm, oldmm)	(0)
451 #define mm_alloc_pgd(mm)	(0)
452 #define mm_free_pgd(mm)
453 #endif /* CONFIG_MMU */
454 
455 __cacheline_aligned_in_smp DEFINE_SPINLOCK(mmlist_lock);
456 
457 #define allocate_mm()	(kmem_cache_alloc(mm_cachep, GFP_KERNEL))
458 #define free_mm(mm)	(kmem_cache_free(mm_cachep, (mm)))
459 
460 static unsigned long default_dump_filter = MMF_DUMP_FILTER_DEFAULT;
461 
462 static int __init coredump_filter_setup(char *s)
463 {
464 	default_dump_filter =
465 		(simple_strtoul(s, NULL, 0) << MMF_DUMP_FILTER_SHIFT) &
466 		MMF_DUMP_FILTER_MASK;
467 	return 1;
468 }
469 
470 __setup("coredump_filter=", coredump_filter_setup);
471 
472 #include <linux/init_task.h>
473 
474 static void mm_init_aio(struct mm_struct *mm)
475 {
476 #ifdef CONFIG_AIO
477 	spin_lock_init(&mm->ioctx_lock);
478 	INIT_HLIST_HEAD(&mm->ioctx_list);
479 #endif
480 }
481 
482 static struct mm_struct * mm_init(struct mm_struct * mm, struct task_struct *p)
483 {
484 	atomic_set(&mm->mm_users, 1);
485 	atomic_set(&mm->mm_count, 1);
486 	init_rwsem(&mm->mmap_sem);
487 	INIT_LIST_HEAD(&mm->mmlist);
488 	mm->flags = (current->mm) ?
489 		(current->mm->flags & MMF_INIT_MASK) : default_dump_filter;
490 	mm->core_state = NULL;
491 	mm->nr_ptes = 0;
492 	memset(&mm->rss_stat, 0, sizeof(mm->rss_stat));
493 	spin_lock_init(&mm->page_table_lock);
494 	mm->free_area_cache = TASK_UNMAPPED_BASE;
495 	mm->cached_hole_size = ~0UL;
496 	mm_init_aio(mm);
497 	mm_init_owner(mm, p);
498 	atomic_set(&mm->oom_disable_count, 0);
499 
500 	if (likely(!mm_alloc_pgd(mm))) {
501 		mm->def_flags = 0;
502 		mmu_notifier_mm_init(mm);
503 		return mm;
504 	}
505 
506 	free_mm(mm);
507 	return NULL;
508 }
509 
510 /*
511  * Allocate and initialize an mm_struct.
512  */
513 struct mm_struct * mm_alloc(void)
514 {
515 	struct mm_struct * mm;
516 
517 	mm = allocate_mm();
518 	if (mm) {
519 		memset(mm, 0, sizeof(*mm));
520 		mm = mm_init(mm, current);
521 	}
522 	return mm;
523 }
524 
525 /*
526  * Called when the last reference to the mm
527  * is dropped: either by a lazy thread or by
528  * mmput. Free the page directory and the mm.
529  */
530 void __mmdrop(struct mm_struct *mm)
531 {
532 	BUG_ON(mm == &init_mm);
533 	mm_free_pgd(mm);
534 	destroy_context(mm);
535 	mmu_notifier_mm_destroy(mm);
536 #ifdef CONFIG_TRANSPARENT_HUGEPAGE
537 	VM_BUG_ON(mm->pmd_huge_pte);
538 #endif
539 	free_mm(mm);
540 }
541 EXPORT_SYMBOL_GPL(__mmdrop);
542 
543 /*
544  * Decrement the use count and release all resources for an mm.
545  */
546 void mmput(struct mm_struct *mm)
547 {
548 	might_sleep();
549 
550 	if (atomic_dec_and_test(&mm->mm_users)) {
551 		exit_aio(mm);
552 		ksm_exit(mm);
553 		khugepaged_exit(mm); /* must run before exit_mmap */
554 		exit_mmap(mm);
555 		set_mm_exe_file(mm, NULL);
556 		if (!list_empty(&mm->mmlist)) {
557 			spin_lock(&mmlist_lock);
558 			list_del(&mm->mmlist);
559 			spin_unlock(&mmlist_lock);
560 		}
561 		put_swap_token(mm);
562 		if (mm->binfmt)
563 			module_put(mm->binfmt->module);
564 		mmdrop(mm);
565 	}
566 }
567 EXPORT_SYMBOL_GPL(mmput);
568 
569 /**
570  * get_task_mm - acquire a reference to the task's mm
571  *
572  * Returns %NULL if the task has no mm.  Checks PF_KTHREAD (meaning
573  * this kernel workthread has transiently adopted a user mm with use_mm,
574  * to do its AIO) is not set and if so returns a reference to it, after
575  * bumping up the use count.  User must release the mm via mmput()
576  * after use.  Typically used by /proc and ptrace.
577  */
578 struct mm_struct *get_task_mm(struct task_struct *task)
579 {
580 	struct mm_struct *mm;
581 
582 	task_lock(task);
583 	mm = task->mm;
584 	if (mm) {
585 		if (task->flags & PF_KTHREAD)
586 			mm = NULL;
587 		else
588 			atomic_inc(&mm->mm_users);
589 	}
590 	task_unlock(task);
591 	return mm;
592 }
593 EXPORT_SYMBOL_GPL(get_task_mm);
594 
595 /* Please note the differences between mmput and mm_release.
596  * mmput is called whenever we stop holding onto a mm_struct,
597  * error success whatever.
598  *
599  * mm_release is called after a mm_struct has been removed
600  * from the current process.
601  *
602  * This difference is important for error handling, when we
603  * only half set up a mm_struct for a new process and need to restore
604  * the old one.  Because we mmput the new mm_struct before
605  * restoring the old one. . .
606  * Eric Biederman 10 January 1998
607  */
608 void mm_release(struct task_struct *tsk, struct mm_struct *mm)
609 {
610 	struct completion *vfork_done = tsk->vfork_done;
611 
612 	/* Get rid of any futexes when releasing the mm */
613 #ifdef CONFIG_FUTEX
614 	if (unlikely(tsk->robust_list)) {
615 		exit_robust_list(tsk);
616 		tsk->robust_list = NULL;
617 	}
618 #ifdef CONFIG_COMPAT
619 	if (unlikely(tsk->compat_robust_list)) {
620 		compat_exit_robust_list(tsk);
621 		tsk->compat_robust_list = NULL;
622 	}
623 #endif
624 	if (unlikely(!list_empty(&tsk->pi_state_list)))
625 		exit_pi_state_list(tsk);
626 #endif
627 
628 	/* Get rid of any cached register state */
629 	deactivate_mm(tsk, mm);
630 
631 	/* notify parent sleeping on vfork() */
632 	if (vfork_done) {
633 		tsk->vfork_done = NULL;
634 		complete(vfork_done);
635 	}
636 
637 	/*
638 	 * If we're exiting normally, clear a user-space tid field if
639 	 * requested.  We leave this alone when dying by signal, to leave
640 	 * the value intact in a core dump, and to save the unnecessary
641 	 * trouble otherwise.  Userland only wants this done for a sys_exit.
642 	 */
643 	if (tsk->clear_child_tid) {
644 		if (!(tsk->flags & PF_SIGNALED) &&
645 		    atomic_read(&mm->mm_users) > 1) {
646 			/*
647 			 * We don't check the error code - if userspace has
648 			 * not set up a proper pointer then tough luck.
649 			 */
650 			put_user(0, tsk->clear_child_tid);
651 			sys_futex(tsk->clear_child_tid, FUTEX_WAKE,
652 					1, NULL, NULL, 0);
653 		}
654 		tsk->clear_child_tid = NULL;
655 	}
656 }
657 
658 /*
659  * Allocate a new mm structure and copy contents from the
660  * mm structure of the passed in task structure.
661  */
662 struct mm_struct *dup_mm(struct task_struct *tsk)
663 {
664 	struct mm_struct *mm, *oldmm = current->mm;
665 	int err;
666 
667 	if (!oldmm)
668 		return NULL;
669 
670 	mm = allocate_mm();
671 	if (!mm)
672 		goto fail_nomem;
673 
674 	memcpy(mm, oldmm, sizeof(*mm));
675 
676 	/* Initializing for Swap token stuff */
677 	mm->token_priority = 0;
678 	mm->last_interval = 0;
679 
680 #ifdef CONFIG_TRANSPARENT_HUGEPAGE
681 	mm->pmd_huge_pte = NULL;
682 #endif
683 
684 	if (!mm_init(mm, tsk))
685 		goto fail_nomem;
686 
687 	if (init_new_context(tsk, mm))
688 		goto fail_nocontext;
689 
690 	dup_mm_exe_file(oldmm, mm);
691 
692 	err = dup_mmap(mm, oldmm);
693 	if (err)
694 		goto free_pt;
695 
696 	mm->hiwater_rss = get_mm_rss(mm);
697 	mm->hiwater_vm = mm->total_vm;
698 
699 	if (mm->binfmt && !try_module_get(mm->binfmt->module))
700 		goto free_pt;
701 
702 	return mm;
703 
704 free_pt:
705 	/* don't put binfmt in mmput, we haven't got module yet */
706 	mm->binfmt = NULL;
707 	mmput(mm);
708 
709 fail_nomem:
710 	return NULL;
711 
712 fail_nocontext:
713 	/*
714 	 * If init_new_context() failed, we cannot use mmput() to free the mm
715 	 * because it calls destroy_context()
716 	 */
717 	mm_free_pgd(mm);
718 	free_mm(mm);
719 	return NULL;
720 }
721 
722 static int copy_mm(unsigned long clone_flags, struct task_struct * tsk)
723 {
724 	struct mm_struct * mm, *oldmm;
725 	int retval;
726 
727 	tsk->min_flt = tsk->maj_flt = 0;
728 	tsk->nvcsw = tsk->nivcsw = 0;
729 #ifdef CONFIG_DETECT_HUNG_TASK
730 	tsk->last_switch_count = tsk->nvcsw + tsk->nivcsw;
731 #endif
732 
733 	tsk->mm = NULL;
734 	tsk->active_mm = NULL;
735 
736 	/*
737 	 * Are we cloning a kernel thread?
738 	 *
739 	 * We need to steal a active VM for that..
740 	 */
741 	oldmm = current->mm;
742 	if (!oldmm)
743 		return 0;
744 
745 	if (clone_flags & CLONE_VM) {
746 		atomic_inc(&oldmm->mm_users);
747 		mm = oldmm;
748 		goto good_mm;
749 	}
750 
751 	retval = -ENOMEM;
752 	mm = dup_mm(tsk);
753 	if (!mm)
754 		goto fail_nomem;
755 
756 good_mm:
757 	/* Initializing for Swap token stuff */
758 	mm->token_priority = 0;
759 	mm->last_interval = 0;
760 	if (tsk->signal->oom_score_adj == OOM_SCORE_ADJ_MIN)
761 		atomic_inc(&mm->oom_disable_count);
762 
763 	tsk->mm = mm;
764 	tsk->active_mm = mm;
765 	return 0;
766 
767 fail_nomem:
768 	return retval;
769 }
770 
771 static int copy_fs(unsigned long clone_flags, struct task_struct *tsk)
772 {
773 	struct fs_struct *fs = current->fs;
774 	if (clone_flags & CLONE_FS) {
775 		/* tsk->fs is already what we want */
776 		spin_lock(&fs->lock);
777 		if (fs->in_exec) {
778 			spin_unlock(&fs->lock);
779 			return -EAGAIN;
780 		}
781 		fs->users++;
782 		spin_unlock(&fs->lock);
783 		return 0;
784 	}
785 	tsk->fs = copy_fs_struct(fs);
786 	if (!tsk->fs)
787 		return -ENOMEM;
788 	return 0;
789 }
790 
791 static int copy_files(unsigned long clone_flags, struct task_struct * tsk)
792 {
793 	struct files_struct *oldf, *newf;
794 	int error = 0;
795 
796 	/*
797 	 * A background process may not have any files ...
798 	 */
799 	oldf = current->files;
800 	if (!oldf)
801 		goto out;
802 
803 	if (clone_flags & CLONE_FILES) {
804 		atomic_inc(&oldf->count);
805 		goto out;
806 	}
807 
808 	newf = dup_fd(oldf, &error);
809 	if (!newf)
810 		goto out;
811 
812 	tsk->files = newf;
813 	error = 0;
814 out:
815 	return error;
816 }
817 
818 static int copy_io(unsigned long clone_flags, struct task_struct *tsk)
819 {
820 #ifdef CONFIG_BLOCK
821 	struct io_context *ioc = current->io_context;
822 
823 	if (!ioc)
824 		return 0;
825 	/*
826 	 * Share io context with parent, if CLONE_IO is set
827 	 */
828 	if (clone_flags & CLONE_IO) {
829 		tsk->io_context = ioc_task_link(ioc);
830 		if (unlikely(!tsk->io_context))
831 			return -ENOMEM;
832 	} else if (ioprio_valid(ioc->ioprio)) {
833 		tsk->io_context = alloc_io_context(GFP_KERNEL, -1);
834 		if (unlikely(!tsk->io_context))
835 			return -ENOMEM;
836 
837 		tsk->io_context->ioprio = ioc->ioprio;
838 	}
839 #endif
840 	return 0;
841 }
842 
843 static int copy_sighand(unsigned long clone_flags, struct task_struct *tsk)
844 {
845 	struct sighand_struct *sig;
846 
847 	if (clone_flags & CLONE_SIGHAND) {
848 		atomic_inc(&current->sighand->count);
849 		return 0;
850 	}
851 	sig = kmem_cache_alloc(sighand_cachep, GFP_KERNEL);
852 	rcu_assign_pointer(tsk->sighand, sig);
853 	if (!sig)
854 		return -ENOMEM;
855 	atomic_set(&sig->count, 1);
856 	memcpy(sig->action, current->sighand->action, sizeof(sig->action));
857 	return 0;
858 }
859 
860 void __cleanup_sighand(struct sighand_struct *sighand)
861 {
862 	if (atomic_dec_and_test(&sighand->count))
863 		kmem_cache_free(sighand_cachep, sighand);
864 }
865 
866 
867 /*
868  * Initialize POSIX timer handling for a thread group.
869  */
870 static void posix_cpu_timers_init_group(struct signal_struct *sig)
871 {
872 	unsigned long cpu_limit;
873 
874 	/* Thread group counters. */
875 	thread_group_cputime_init(sig);
876 
877 	cpu_limit = ACCESS_ONCE(sig->rlim[RLIMIT_CPU].rlim_cur);
878 	if (cpu_limit != RLIM_INFINITY) {
879 		sig->cputime_expires.prof_exp = secs_to_cputime(cpu_limit);
880 		sig->cputimer.running = 1;
881 	}
882 
883 	/* The timer lists. */
884 	INIT_LIST_HEAD(&sig->cpu_timers[0]);
885 	INIT_LIST_HEAD(&sig->cpu_timers[1]);
886 	INIT_LIST_HEAD(&sig->cpu_timers[2]);
887 }
888 
889 static int copy_signal(unsigned long clone_flags, struct task_struct *tsk)
890 {
891 	struct signal_struct *sig;
892 
893 	if (clone_flags & CLONE_THREAD)
894 		return 0;
895 
896 	sig = kmem_cache_zalloc(signal_cachep, GFP_KERNEL);
897 	tsk->signal = sig;
898 	if (!sig)
899 		return -ENOMEM;
900 
901 	sig->nr_threads = 1;
902 	atomic_set(&sig->live, 1);
903 	atomic_set(&sig->sigcnt, 1);
904 	init_waitqueue_head(&sig->wait_chldexit);
905 	if (clone_flags & CLONE_NEWPID)
906 		sig->flags |= SIGNAL_UNKILLABLE;
907 	sig->curr_target = tsk;
908 	init_sigpending(&sig->shared_pending);
909 	INIT_LIST_HEAD(&sig->posix_timers);
910 
911 	hrtimer_init(&sig->real_timer, CLOCK_MONOTONIC, HRTIMER_MODE_REL);
912 	sig->real_timer.function = it_real_fn;
913 
914 	task_lock(current->group_leader);
915 	memcpy(sig->rlim, current->signal->rlim, sizeof sig->rlim);
916 	task_unlock(current->group_leader);
917 
918 	posix_cpu_timers_init_group(sig);
919 
920 	tty_audit_fork(sig);
921 	sched_autogroup_fork(sig);
922 
923 	sig->oom_adj = current->signal->oom_adj;
924 	sig->oom_score_adj = current->signal->oom_score_adj;
925 	sig->oom_score_adj_min = current->signal->oom_score_adj_min;
926 
927 	mutex_init(&sig->cred_guard_mutex);
928 
929 	return 0;
930 }
931 
932 static void copy_flags(unsigned long clone_flags, struct task_struct *p)
933 {
934 	unsigned long new_flags = p->flags;
935 
936 	new_flags &= ~(PF_SUPERPRIV | PF_WQ_WORKER);
937 	new_flags |= PF_FORKNOEXEC;
938 	new_flags |= PF_STARTING;
939 	p->flags = new_flags;
940 	clear_freeze_flag(p);
941 }
942 
943 SYSCALL_DEFINE1(set_tid_address, int __user *, tidptr)
944 {
945 	current->clear_child_tid = tidptr;
946 
947 	return task_pid_vnr(current);
948 }
949 
950 static void rt_mutex_init_task(struct task_struct *p)
951 {
952 	raw_spin_lock_init(&p->pi_lock);
953 #ifdef CONFIG_RT_MUTEXES
954 	plist_head_init_raw(&p->pi_waiters, &p->pi_lock);
955 	p->pi_blocked_on = NULL;
956 #endif
957 }
958 
959 #ifdef CONFIG_MM_OWNER
960 void mm_init_owner(struct mm_struct *mm, struct task_struct *p)
961 {
962 	mm->owner = p;
963 }
964 #endif /* CONFIG_MM_OWNER */
965 
966 /*
967  * Initialize POSIX timer handling for a single task.
968  */
969 static void posix_cpu_timers_init(struct task_struct *tsk)
970 {
971 	tsk->cputime_expires.prof_exp = cputime_zero;
972 	tsk->cputime_expires.virt_exp = cputime_zero;
973 	tsk->cputime_expires.sched_exp = 0;
974 	INIT_LIST_HEAD(&tsk->cpu_timers[0]);
975 	INIT_LIST_HEAD(&tsk->cpu_timers[1]);
976 	INIT_LIST_HEAD(&tsk->cpu_timers[2]);
977 }
978 
979 /*
980  * This creates a new process as a copy of the old one,
981  * but does not actually start it yet.
982  *
983  * It copies the registers, and all the appropriate
984  * parts of the process environment (as per the clone
985  * flags). The actual kick-off is left to the caller.
986  */
987 static struct task_struct *copy_process(unsigned long clone_flags,
988 					unsigned long stack_start,
989 					struct pt_regs *regs,
990 					unsigned long stack_size,
991 					int __user *child_tidptr,
992 					struct pid *pid,
993 					int trace)
994 {
995 	int retval;
996 	struct task_struct *p;
997 	int cgroup_callbacks_done = 0;
998 
999 	if ((clone_flags & (CLONE_NEWNS|CLONE_FS)) == (CLONE_NEWNS|CLONE_FS))
1000 		return ERR_PTR(-EINVAL);
1001 
1002 	/*
1003 	 * Thread groups must share signals as well, and detached threads
1004 	 * can only be started up within the thread group.
1005 	 */
1006 	if ((clone_flags & CLONE_THREAD) && !(clone_flags & CLONE_SIGHAND))
1007 		return ERR_PTR(-EINVAL);
1008 
1009 	/*
1010 	 * Shared signal handlers imply shared VM. By way of the above,
1011 	 * thread groups also imply shared VM. Blocking this case allows
1012 	 * for various simplifications in other code.
1013 	 */
1014 	if ((clone_flags & CLONE_SIGHAND) && !(clone_flags & CLONE_VM))
1015 		return ERR_PTR(-EINVAL);
1016 
1017 	/*
1018 	 * Siblings of global init remain as zombies on exit since they are
1019 	 * not reaped by their parent (swapper). To solve this and to avoid
1020 	 * multi-rooted process trees, prevent global and container-inits
1021 	 * from creating siblings.
1022 	 */
1023 	if ((clone_flags & CLONE_PARENT) &&
1024 				current->signal->flags & SIGNAL_UNKILLABLE)
1025 		return ERR_PTR(-EINVAL);
1026 
1027 	retval = security_task_create(clone_flags);
1028 	if (retval)
1029 		goto fork_out;
1030 
1031 	retval = -ENOMEM;
1032 	p = dup_task_struct(current);
1033 	if (!p)
1034 		goto fork_out;
1035 
1036 	ftrace_graph_init_task(p);
1037 
1038 	rt_mutex_init_task(p);
1039 
1040 #ifdef CONFIG_PROVE_LOCKING
1041 	DEBUG_LOCKS_WARN_ON(!p->hardirqs_enabled);
1042 	DEBUG_LOCKS_WARN_ON(!p->softirqs_enabled);
1043 #endif
1044 	retval = -EAGAIN;
1045 	if (atomic_read(&p->real_cred->user->processes) >=
1046 			task_rlimit(p, RLIMIT_NPROC)) {
1047 		if (!capable(CAP_SYS_ADMIN) && !capable(CAP_SYS_RESOURCE) &&
1048 		    p->real_cred->user != INIT_USER)
1049 			goto bad_fork_free;
1050 	}
1051 
1052 	retval = copy_creds(p, clone_flags);
1053 	if (retval < 0)
1054 		goto bad_fork_free;
1055 
1056 	/*
1057 	 * If multiple threads are within copy_process(), then this check
1058 	 * triggers too late. This doesn't hurt, the check is only there
1059 	 * to stop root fork bombs.
1060 	 */
1061 	retval = -EAGAIN;
1062 	if (nr_threads >= max_threads)
1063 		goto bad_fork_cleanup_count;
1064 
1065 	if (!try_module_get(task_thread_info(p)->exec_domain->module))
1066 		goto bad_fork_cleanup_count;
1067 
1068 	p->did_exec = 0;
1069 	delayacct_tsk_init(p);	/* Must remain after dup_task_struct() */
1070 	copy_flags(clone_flags, p);
1071 	INIT_LIST_HEAD(&p->children);
1072 	INIT_LIST_HEAD(&p->sibling);
1073 	rcu_copy_process(p);
1074 	p->vfork_done = NULL;
1075 	spin_lock_init(&p->alloc_lock);
1076 
1077 	init_sigpending(&p->pending);
1078 
1079 	p->utime = cputime_zero;
1080 	p->stime = cputime_zero;
1081 	p->gtime = cputime_zero;
1082 	p->utimescaled = cputime_zero;
1083 	p->stimescaled = cputime_zero;
1084 #ifndef CONFIG_VIRT_CPU_ACCOUNTING
1085 	p->prev_utime = cputime_zero;
1086 	p->prev_stime = cputime_zero;
1087 #endif
1088 #if defined(SPLIT_RSS_COUNTING)
1089 	memset(&p->rss_stat, 0, sizeof(p->rss_stat));
1090 #endif
1091 
1092 	p->default_timer_slack_ns = current->timer_slack_ns;
1093 
1094 	task_io_accounting_init(&p->ioac);
1095 	acct_clear_integrals(p);
1096 
1097 	posix_cpu_timers_init(p);
1098 
1099 	p->lock_depth = -1;		/* -1 = no lock */
1100 	do_posix_clock_monotonic_gettime(&p->start_time);
1101 	p->real_start_time = p->start_time;
1102 	monotonic_to_bootbased(&p->real_start_time);
1103 	p->io_context = NULL;
1104 	p->audit_context = NULL;
1105 	cgroup_fork(p);
1106 #ifdef CONFIG_NUMA
1107 	p->mempolicy = mpol_dup(p->mempolicy);
1108  	if (IS_ERR(p->mempolicy)) {
1109  		retval = PTR_ERR(p->mempolicy);
1110  		p->mempolicy = NULL;
1111  		goto bad_fork_cleanup_cgroup;
1112  	}
1113 	mpol_fix_fork_child_flag(p);
1114 #endif
1115 #ifdef CONFIG_TRACE_IRQFLAGS
1116 	p->irq_events = 0;
1117 #ifdef __ARCH_WANT_INTERRUPTS_ON_CTXSW
1118 	p->hardirqs_enabled = 1;
1119 #else
1120 	p->hardirqs_enabled = 0;
1121 #endif
1122 	p->hardirq_enable_ip = 0;
1123 	p->hardirq_enable_event = 0;
1124 	p->hardirq_disable_ip = _THIS_IP_;
1125 	p->hardirq_disable_event = 0;
1126 	p->softirqs_enabled = 1;
1127 	p->softirq_enable_ip = _THIS_IP_;
1128 	p->softirq_enable_event = 0;
1129 	p->softirq_disable_ip = 0;
1130 	p->softirq_disable_event = 0;
1131 	p->hardirq_context = 0;
1132 	p->softirq_context = 0;
1133 #endif
1134 #ifdef CONFIG_LOCKDEP
1135 	p->lockdep_depth = 0; /* no locks held yet */
1136 	p->curr_chain_key = 0;
1137 	p->lockdep_recursion = 0;
1138 #endif
1139 
1140 #ifdef CONFIG_DEBUG_MUTEXES
1141 	p->blocked_on = NULL; /* not blocked yet */
1142 #endif
1143 #ifdef CONFIG_CGROUP_MEM_RES_CTLR
1144 	p->memcg_batch.do_batch = 0;
1145 	p->memcg_batch.memcg = NULL;
1146 #endif
1147 
1148 	/* Perform scheduler related setup. Assign this task to a CPU. */
1149 	sched_fork(p, clone_flags);
1150 
1151 	retval = perf_event_init_task(p);
1152 	if (retval)
1153 		goto bad_fork_cleanup_policy;
1154 
1155 	if ((retval = audit_alloc(p)))
1156 		goto bad_fork_cleanup_policy;
1157 	/* copy all the process information */
1158 	if ((retval = copy_semundo(clone_flags, p)))
1159 		goto bad_fork_cleanup_audit;
1160 	if ((retval = copy_files(clone_flags, p)))
1161 		goto bad_fork_cleanup_semundo;
1162 	if ((retval = copy_fs(clone_flags, p)))
1163 		goto bad_fork_cleanup_files;
1164 	if ((retval = copy_sighand(clone_flags, p)))
1165 		goto bad_fork_cleanup_fs;
1166 	if ((retval = copy_signal(clone_flags, p)))
1167 		goto bad_fork_cleanup_sighand;
1168 	if ((retval = copy_mm(clone_flags, p)))
1169 		goto bad_fork_cleanup_signal;
1170 	if ((retval = copy_namespaces(clone_flags, p)))
1171 		goto bad_fork_cleanup_mm;
1172 	if ((retval = copy_io(clone_flags, p)))
1173 		goto bad_fork_cleanup_namespaces;
1174 	retval = copy_thread(clone_flags, stack_start, stack_size, p, regs);
1175 	if (retval)
1176 		goto bad_fork_cleanup_io;
1177 
1178 	if (pid != &init_struct_pid) {
1179 		retval = -ENOMEM;
1180 		pid = alloc_pid(p->nsproxy->pid_ns);
1181 		if (!pid)
1182 			goto bad_fork_cleanup_io;
1183 
1184 		if (clone_flags & CLONE_NEWPID) {
1185 			retval = pid_ns_prepare_proc(p->nsproxy->pid_ns);
1186 			if (retval < 0)
1187 				goto bad_fork_free_pid;
1188 		}
1189 	}
1190 
1191 	p->pid = pid_nr(pid);
1192 	p->tgid = p->pid;
1193 	if (clone_flags & CLONE_THREAD)
1194 		p->tgid = current->tgid;
1195 
1196 	if (current->nsproxy != p->nsproxy) {
1197 		retval = ns_cgroup_clone(p, pid);
1198 		if (retval)
1199 			goto bad_fork_free_pid;
1200 	}
1201 
1202 	p->set_child_tid = (clone_flags & CLONE_CHILD_SETTID) ? child_tidptr : NULL;
1203 	/*
1204 	 * Clear TID on mm_release()?
1205 	 */
1206 	p->clear_child_tid = (clone_flags & CLONE_CHILD_CLEARTID) ? child_tidptr: NULL;
1207 #ifdef CONFIG_FUTEX
1208 	p->robust_list = NULL;
1209 #ifdef CONFIG_COMPAT
1210 	p->compat_robust_list = NULL;
1211 #endif
1212 	INIT_LIST_HEAD(&p->pi_state_list);
1213 	p->pi_state_cache = NULL;
1214 #endif
1215 	/*
1216 	 * sigaltstack should be cleared when sharing the same VM
1217 	 */
1218 	if ((clone_flags & (CLONE_VM|CLONE_VFORK)) == CLONE_VM)
1219 		p->sas_ss_sp = p->sas_ss_size = 0;
1220 
1221 	/*
1222 	 * Syscall tracing and stepping should be turned off in the
1223 	 * child regardless of CLONE_PTRACE.
1224 	 */
1225 	user_disable_single_step(p);
1226 	clear_tsk_thread_flag(p, TIF_SYSCALL_TRACE);
1227 #ifdef TIF_SYSCALL_EMU
1228 	clear_tsk_thread_flag(p, TIF_SYSCALL_EMU);
1229 #endif
1230 	clear_all_latency_tracing(p);
1231 
1232 	/* ok, now we should be set up.. */
1233 	p->exit_signal = (clone_flags & CLONE_THREAD) ? -1 : (clone_flags & CSIGNAL);
1234 	p->pdeath_signal = 0;
1235 	p->exit_state = 0;
1236 
1237 	/*
1238 	 * Ok, make it visible to the rest of the system.
1239 	 * We dont wake it up yet.
1240 	 */
1241 	p->group_leader = p;
1242 	INIT_LIST_HEAD(&p->thread_group);
1243 
1244 	/* Now that the task is set up, run cgroup callbacks if
1245 	 * necessary. We need to run them before the task is visible
1246 	 * on the tasklist. */
1247 	cgroup_fork_callbacks(p);
1248 	cgroup_callbacks_done = 1;
1249 
1250 	/* Need tasklist lock for parent etc handling! */
1251 	write_lock_irq(&tasklist_lock);
1252 
1253 	/* CLONE_PARENT re-uses the old parent */
1254 	if (clone_flags & (CLONE_PARENT|CLONE_THREAD)) {
1255 		p->real_parent = current->real_parent;
1256 		p->parent_exec_id = current->parent_exec_id;
1257 	} else {
1258 		p->real_parent = current;
1259 		p->parent_exec_id = current->self_exec_id;
1260 	}
1261 
1262 	spin_lock(&current->sighand->siglock);
1263 
1264 	/*
1265 	 * Process group and session signals need to be delivered to just the
1266 	 * parent before the fork or both the parent and the child after the
1267 	 * fork. Restart if a signal comes in before we add the new process to
1268 	 * it's process group.
1269 	 * A fatal signal pending means that current will exit, so the new
1270 	 * thread can't slip out of an OOM kill (or normal SIGKILL).
1271  	 */
1272 	recalc_sigpending();
1273 	if (signal_pending(current)) {
1274 		spin_unlock(&current->sighand->siglock);
1275 		write_unlock_irq(&tasklist_lock);
1276 		retval = -ERESTARTNOINTR;
1277 		goto bad_fork_free_pid;
1278 	}
1279 
1280 	if (clone_flags & CLONE_THREAD) {
1281 		current->signal->nr_threads++;
1282 		atomic_inc(&current->signal->live);
1283 		atomic_inc(&current->signal->sigcnt);
1284 		p->group_leader = current->group_leader;
1285 		list_add_tail_rcu(&p->thread_group, &p->group_leader->thread_group);
1286 	}
1287 
1288 	if (likely(p->pid)) {
1289 		tracehook_finish_clone(p, clone_flags, trace);
1290 
1291 		if (thread_group_leader(p)) {
1292 			if (clone_flags & CLONE_NEWPID)
1293 				p->nsproxy->pid_ns->child_reaper = p;
1294 
1295 			p->signal->leader_pid = pid;
1296 			p->signal->tty = tty_kref_get(current->signal->tty);
1297 			attach_pid(p, PIDTYPE_PGID, task_pgrp(current));
1298 			attach_pid(p, PIDTYPE_SID, task_session(current));
1299 			list_add_tail(&p->sibling, &p->real_parent->children);
1300 			list_add_tail_rcu(&p->tasks, &init_task.tasks);
1301 			__this_cpu_inc(process_counts);
1302 		}
1303 		attach_pid(p, PIDTYPE_PID, pid);
1304 		nr_threads++;
1305 	}
1306 
1307 	total_forks++;
1308 	spin_unlock(&current->sighand->siglock);
1309 	write_unlock_irq(&tasklist_lock);
1310 	proc_fork_connector(p);
1311 	cgroup_post_fork(p);
1312 	perf_event_fork(p);
1313 	return p;
1314 
1315 bad_fork_free_pid:
1316 	if (pid != &init_struct_pid)
1317 		free_pid(pid);
1318 bad_fork_cleanup_io:
1319 	if (p->io_context)
1320 		exit_io_context(p);
1321 bad_fork_cleanup_namespaces:
1322 	exit_task_namespaces(p);
1323 bad_fork_cleanup_mm:
1324 	if (p->mm) {
1325 		task_lock(p);
1326 		if (p->signal->oom_score_adj == OOM_SCORE_ADJ_MIN)
1327 			atomic_dec(&p->mm->oom_disable_count);
1328 		task_unlock(p);
1329 		mmput(p->mm);
1330 	}
1331 bad_fork_cleanup_signal:
1332 	if (!(clone_flags & CLONE_THREAD))
1333 		free_signal_struct(p->signal);
1334 bad_fork_cleanup_sighand:
1335 	__cleanup_sighand(p->sighand);
1336 bad_fork_cleanup_fs:
1337 	exit_fs(p); /* blocking */
1338 bad_fork_cleanup_files:
1339 	exit_files(p); /* blocking */
1340 bad_fork_cleanup_semundo:
1341 	exit_sem(p);
1342 bad_fork_cleanup_audit:
1343 	audit_free(p);
1344 bad_fork_cleanup_policy:
1345 	perf_event_free_task(p);
1346 #ifdef CONFIG_NUMA
1347 	mpol_put(p->mempolicy);
1348 bad_fork_cleanup_cgroup:
1349 #endif
1350 	cgroup_exit(p, cgroup_callbacks_done);
1351 	delayacct_tsk_free(p);
1352 	module_put(task_thread_info(p)->exec_domain->module);
1353 bad_fork_cleanup_count:
1354 	atomic_dec(&p->cred->user->processes);
1355 	exit_creds(p);
1356 bad_fork_free:
1357 	free_task(p);
1358 fork_out:
1359 	return ERR_PTR(retval);
1360 }
1361 
1362 noinline struct pt_regs * __cpuinit __attribute__((weak)) idle_regs(struct pt_regs *regs)
1363 {
1364 	memset(regs, 0, sizeof(struct pt_regs));
1365 	return regs;
1366 }
1367 
1368 static inline void init_idle_pids(struct pid_link *links)
1369 {
1370 	enum pid_type type;
1371 
1372 	for (type = PIDTYPE_PID; type < PIDTYPE_MAX; ++type) {
1373 		INIT_HLIST_NODE(&links[type].node); /* not really needed */
1374 		links[type].pid = &init_struct_pid;
1375 	}
1376 }
1377 
1378 struct task_struct * __cpuinit fork_idle(int cpu)
1379 {
1380 	struct task_struct *task;
1381 	struct pt_regs regs;
1382 
1383 	task = copy_process(CLONE_VM, 0, idle_regs(&regs), 0, NULL,
1384 			    &init_struct_pid, 0);
1385 	if (!IS_ERR(task)) {
1386 		init_idle_pids(task->pids);
1387 		init_idle(task, cpu);
1388 	}
1389 
1390 	return task;
1391 }
1392 
1393 /*
1394  *  Ok, this is the main fork-routine.
1395  *
1396  * It copies the process, and if successful kick-starts
1397  * it and waits for it to finish using the VM if required.
1398  */
1399 long do_fork(unsigned long clone_flags,
1400 	      unsigned long stack_start,
1401 	      struct pt_regs *regs,
1402 	      unsigned long stack_size,
1403 	      int __user *parent_tidptr,
1404 	      int __user *child_tidptr)
1405 {
1406 	struct task_struct *p;
1407 	int trace = 0;
1408 	long nr;
1409 
1410 	/*
1411 	 * Do some preliminary argument and permissions checking before we
1412 	 * actually start allocating stuff
1413 	 */
1414 	if (clone_flags & CLONE_NEWUSER) {
1415 		if (clone_flags & CLONE_THREAD)
1416 			return -EINVAL;
1417 		/* hopefully this check will go away when userns support is
1418 		 * complete
1419 		 */
1420 		if (!capable(CAP_SYS_ADMIN) || !capable(CAP_SETUID) ||
1421 				!capable(CAP_SETGID))
1422 			return -EPERM;
1423 	}
1424 
1425 	/*
1426 	 * When called from kernel_thread, don't do user tracing stuff.
1427 	 */
1428 	if (likely(user_mode(regs)))
1429 		trace = tracehook_prepare_clone(clone_flags);
1430 
1431 	p = copy_process(clone_flags, stack_start, regs, stack_size,
1432 			 child_tidptr, NULL, trace);
1433 	/*
1434 	 * Do this prior waking up the new thread - the thread pointer
1435 	 * might get invalid after that point, if the thread exits quickly.
1436 	 */
1437 	if (!IS_ERR(p)) {
1438 		struct completion vfork;
1439 
1440 		trace_sched_process_fork(current, p);
1441 
1442 		nr = task_pid_vnr(p);
1443 
1444 		if (clone_flags & CLONE_PARENT_SETTID)
1445 			put_user(nr, parent_tidptr);
1446 
1447 		if (clone_flags & CLONE_VFORK) {
1448 			p->vfork_done = &vfork;
1449 			init_completion(&vfork);
1450 		}
1451 
1452 		audit_finish_fork(p);
1453 		tracehook_report_clone(regs, clone_flags, nr, p);
1454 
1455 		/*
1456 		 * We set PF_STARTING at creation in case tracing wants to
1457 		 * use this to distinguish a fully live task from one that
1458 		 * hasn't gotten to tracehook_report_clone() yet.  Now we
1459 		 * clear it and set the child going.
1460 		 */
1461 		p->flags &= ~PF_STARTING;
1462 
1463 		wake_up_new_task(p, clone_flags);
1464 
1465 		tracehook_report_clone_complete(trace, regs,
1466 						clone_flags, nr, p);
1467 
1468 		if (clone_flags & CLONE_VFORK) {
1469 			freezer_do_not_count();
1470 			wait_for_completion(&vfork);
1471 			freezer_count();
1472 			tracehook_report_vfork_done(p, nr);
1473 		}
1474 	} else {
1475 		nr = PTR_ERR(p);
1476 	}
1477 	return nr;
1478 }
1479 
1480 #ifndef ARCH_MIN_MMSTRUCT_ALIGN
1481 #define ARCH_MIN_MMSTRUCT_ALIGN 0
1482 #endif
1483 
1484 static void sighand_ctor(void *data)
1485 {
1486 	struct sighand_struct *sighand = data;
1487 
1488 	spin_lock_init(&sighand->siglock);
1489 	init_waitqueue_head(&sighand->signalfd_wqh);
1490 }
1491 
1492 void __init proc_caches_init(void)
1493 {
1494 	sighand_cachep = kmem_cache_create("sighand_cache",
1495 			sizeof(struct sighand_struct), 0,
1496 			SLAB_HWCACHE_ALIGN|SLAB_PANIC|SLAB_DESTROY_BY_RCU|
1497 			SLAB_NOTRACK, sighand_ctor);
1498 	signal_cachep = kmem_cache_create("signal_cache",
1499 			sizeof(struct signal_struct), 0,
1500 			SLAB_HWCACHE_ALIGN|SLAB_PANIC|SLAB_NOTRACK, NULL);
1501 	files_cachep = kmem_cache_create("files_cache",
1502 			sizeof(struct files_struct), 0,
1503 			SLAB_HWCACHE_ALIGN|SLAB_PANIC|SLAB_NOTRACK, NULL);
1504 	fs_cachep = kmem_cache_create("fs_cache",
1505 			sizeof(struct fs_struct), 0,
1506 			SLAB_HWCACHE_ALIGN|SLAB_PANIC|SLAB_NOTRACK, NULL);
1507 	mm_cachep = kmem_cache_create("mm_struct",
1508 			sizeof(struct mm_struct), ARCH_MIN_MMSTRUCT_ALIGN,
1509 			SLAB_HWCACHE_ALIGN|SLAB_PANIC|SLAB_NOTRACK, NULL);
1510 	vm_area_cachep = KMEM_CACHE(vm_area_struct, SLAB_PANIC);
1511 	mmap_init();
1512 }
1513 
1514 /*
1515  * Check constraints on flags passed to the unshare system call and
1516  * force unsharing of additional process context as appropriate.
1517  */
1518 static void check_unshare_flags(unsigned long *flags_ptr)
1519 {
1520 	/*
1521 	 * If unsharing a thread from a thread group, must also
1522 	 * unshare vm.
1523 	 */
1524 	if (*flags_ptr & CLONE_THREAD)
1525 		*flags_ptr |= CLONE_VM;
1526 
1527 	/*
1528 	 * If unsharing vm, must also unshare signal handlers.
1529 	 */
1530 	if (*flags_ptr & CLONE_VM)
1531 		*flags_ptr |= CLONE_SIGHAND;
1532 
1533 	/*
1534 	 * If unsharing namespace, must also unshare filesystem information.
1535 	 */
1536 	if (*flags_ptr & CLONE_NEWNS)
1537 		*flags_ptr |= CLONE_FS;
1538 }
1539 
1540 /*
1541  * Unsharing of tasks created with CLONE_THREAD is not supported yet
1542  */
1543 static int unshare_thread(unsigned long unshare_flags)
1544 {
1545 	if (unshare_flags & CLONE_THREAD)
1546 		return -EINVAL;
1547 
1548 	return 0;
1549 }
1550 
1551 /*
1552  * Unshare the filesystem structure if it is being shared
1553  */
1554 static int unshare_fs(unsigned long unshare_flags, struct fs_struct **new_fsp)
1555 {
1556 	struct fs_struct *fs = current->fs;
1557 
1558 	if (!(unshare_flags & CLONE_FS) || !fs)
1559 		return 0;
1560 
1561 	/* don't need lock here; in the worst case we'll do useless copy */
1562 	if (fs->users == 1)
1563 		return 0;
1564 
1565 	*new_fsp = copy_fs_struct(fs);
1566 	if (!*new_fsp)
1567 		return -ENOMEM;
1568 
1569 	return 0;
1570 }
1571 
1572 /*
1573  * Unsharing of sighand is not supported yet
1574  */
1575 static int unshare_sighand(unsigned long unshare_flags, struct sighand_struct **new_sighp)
1576 {
1577 	struct sighand_struct *sigh = current->sighand;
1578 
1579 	if ((unshare_flags & CLONE_SIGHAND) && atomic_read(&sigh->count) > 1)
1580 		return -EINVAL;
1581 	else
1582 		return 0;
1583 }
1584 
1585 /*
1586  * Unshare vm if it is being shared
1587  */
1588 static int unshare_vm(unsigned long unshare_flags, struct mm_struct **new_mmp)
1589 {
1590 	struct mm_struct *mm = current->mm;
1591 
1592 	if ((unshare_flags & CLONE_VM) &&
1593 	    (mm && atomic_read(&mm->mm_users) > 1)) {
1594 		return -EINVAL;
1595 	}
1596 
1597 	return 0;
1598 }
1599 
1600 /*
1601  * Unshare file descriptor table if it is being shared
1602  */
1603 static int unshare_fd(unsigned long unshare_flags, struct files_struct **new_fdp)
1604 {
1605 	struct files_struct *fd = current->files;
1606 	int error = 0;
1607 
1608 	if ((unshare_flags & CLONE_FILES) &&
1609 	    (fd && atomic_read(&fd->count) > 1)) {
1610 		*new_fdp = dup_fd(fd, &error);
1611 		if (!*new_fdp)
1612 			return error;
1613 	}
1614 
1615 	return 0;
1616 }
1617 
1618 /*
1619  * unshare allows a process to 'unshare' part of the process
1620  * context which was originally shared using clone.  copy_*
1621  * functions used by do_fork() cannot be used here directly
1622  * because they modify an inactive task_struct that is being
1623  * constructed. Here we are modifying the current, active,
1624  * task_struct.
1625  */
1626 SYSCALL_DEFINE1(unshare, unsigned long, unshare_flags)
1627 {
1628 	int err = 0;
1629 	struct fs_struct *fs, *new_fs = NULL;
1630 	struct sighand_struct *new_sigh = NULL;
1631 	struct mm_struct *mm, *new_mm = NULL, *active_mm = NULL;
1632 	struct files_struct *fd, *new_fd = NULL;
1633 	struct nsproxy *new_nsproxy = NULL;
1634 	int do_sysvsem = 0;
1635 
1636 	check_unshare_flags(&unshare_flags);
1637 
1638 	/* Return -EINVAL for all unsupported flags */
1639 	err = -EINVAL;
1640 	if (unshare_flags & ~(CLONE_THREAD|CLONE_FS|CLONE_NEWNS|CLONE_SIGHAND|
1641 				CLONE_VM|CLONE_FILES|CLONE_SYSVSEM|
1642 				CLONE_NEWUTS|CLONE_NEWIPC|CLONE_NEWNET))
1643 		goto bad_unshare_out;
1644 
1645 	/*
1646 	 * CLONE_NEWIPC must also detach from the undolist: after switching
1647 	 * to a new ipc namespace, the semaphore arrays from the old
1648 	 * namespace are unreachable.
1649 	 */
1650 	if (unshare_flags & (CLONE_NEWIPC|CLONE_SYSVSEM))
1651 		do_sysvsem = 1;
1652 	if ((err = unshare_thread(unshare_flags)))
1653 		goto bad_unshare_out;
1654 	if ((err = unshare_fs(unshare_flags, &new_fs)))
1655 		goto bad_unshare_cleanup_thread;
1656 	if ((err = unshare_sighand(unshare_flags, &new_sigh)))
1657 		goto bad_unshare_cleanup_fs;
1658 	if ((err = unshare_vm(unshare_flags, &new_mm)))
1659 		goto bad_unshare_cleanup_sigh;
1660 	if ((err = unshare_fd(unshare_flags, &new_fd)))
1661 		goto bad_unshare_cleanup_vm;
1662 	if ((err = unshare_nsproxy_namespaces(unshare_flags, &new_nsproxy,
1663 			new_fs)))
1664 		goto bad_unshare_cleanup_fd;
1665 
1666 	if (new_fs ||  new_mm || new_fd || do_sysvsem || new_nsproxy) {
1667 		if (do_sysvsem) {
1668 			/*
1669 			 * CLONE_SYSVSEM is equivalent to sys_exit().
1670 			 */
1671 			exit_sem(current);
1672 		}
1673 
1674 		if (new_nsproxy) {
1675 			switch_task_namespaces(current, new_nsproxy);
1676 			new_nsproxy = NULL;
1677 		}
1678 
1679 		task_lock(current);
1680 
1681 		if (new_fs) {
1682 			fs = current->fs;
1683 			spin_lock(&fs->lock);
1684 			current->fs = new_fs;
1685 			if (--fs->users)
1686 				new_fs = NULL;
1687 			else
1688 				new_fs = fs;
1689 			spin_unlock(&fs->lock);
1690 		}
1691 
1692 		if (new_mm) {
1693 			mm = current->mm;
1694 			active_mm = current->active_mm;
1695 			current->mm = new_mm;
1696 			current->active_mm = new_mm;
1697 			if (current->signal->oom_score_adj == OOM_SCORE_ADJ_MIN) {
1698 				atomic_dec(&mm->oom_disable_count);
1699 				atomic_inc(&new_mm->oom_disable_count);
1700 			}
1701 			activate_mm(active_mm, new_mm);
1702 			new_mm = mm;
1703 		}
1704 
1705 		if (new_fd) {
1706 			fd = current->files;
1707 			current->files = new_fd;
1708 			new_fd = fd;
1709 		}
1710 
1711 		task_unlock(current);
1712 	}
1713 
1714 	if (new_nsproxy)
1715 		put_nsproxy(new_nsproxy);
1716 
1717 bad_unshare_cleanup_fd:
1718 	if (new_fd)
1719 		put_files_struct(new_fd);
1720 
1721 bad_unshare_cleanup_vm:
1722 	if (new_mm)
1723 		mmput(new_mm);
1724 
1725 bad_unshare_cleanup_sigh:
1726 	if (new_sigh)
1727 		if (atomic_dec_and_test(&new_sigh->count))
1728 			kmem_cache_free(sighand_cachep, new_sigh);
1729 
1730 bad_unshare_cleanup_fs:
1731 	if (new_fs)
1732 		free_fs_struct(new_fs);
1733 
1734 bad_unshare_cleanup_thread:
1735 bad_unshare_out:
1736 	return err;
1737 }
1738 
1739 /*
1740  *	Helper to unshare the files of the current task.
1741  *	We don't want to expose copy_files internals to
1742  *	the exec layer of the kernel.
1743  */
1744 
1745 int unshare_files(struct files_struct **displaced)
1746 {
1747 	struct task_struct *task = current;
1748 	struct files_struct *copy = NULL;
1749 	int error;
1750 
1751 	error = unshare_fd(CLONE_FILES, &copy);
1752 	if (error || !copy) {
1753 		*displaced = NULL;
1754 		return error;
1755 	}
1756 	*displaced = task->files;
1757 	task_lock(task);
1758 	task->files = copy;
1759 	task_unlock(task);
1760 	return 0;
1761 }
1762