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/seccomp.h>
  38#include <linux/swap.h>
  39#include <linux/syscalls.h>
  40#include <linux/jiffies.h>
  41#include <linux/futex.h>
  42#include <linux/compat.h>
  43#include <linux/kthread.h>
  44#include <linux/task_io_accounting_ops.h>
  45#include <linux/rcupdate.h>
  46#include <linux/ptrace.h>
  47#include <linux/mount.h>
  48#include <linux/audit.h>
  49#include <linux/memcontrol.h>
  50#include <linux/ftrace.h>
  51#include <linux/proc_fs.h>
  52#include <linux/profile.h>
  53#include <linux/rmap.h>
  54#include <linux/ksm.h>
  55#include <linux/acct.h>
  56#include <linux/tsacct_kern.h>
  57#include <linux/cn_proc.h>
  58#include <linux/freezer.h>
  59#include <linux/delayacct.h>
  60#include <linux/taskstats_kern.h>
  61#include <linux/random.h>
  62#include <linux/tty.h>
  63#include <linux/blkdev.h>
  64#include <linux/fs_struct.h>
  65#include <linux/magic.h>
  66#include <linux/perf_event.h>
  67#include <linux/posix-timers.h>
  68#include <linux/user-return-notifier.h>
  69#include <linux/oom.h>
  70#include <linux/khugepaged.h>
  71#include <linux/signalfd.h>
  72#include <linux/uprobes.h>
  73
  74#include <asm/pgtable.h>
  75#include <asm/pgalloc.h>
  76#include <asm/uaccess.h>
  77#include <asm/mmu_context.h>
  78#include <asm/cacheflush.h>
  79#include <asm/tlbflush.h>
  80
  81#include <trace/events/sched.h>
  82
  83#define CREATE_TRACE_POINTS
  84#include <trace/events/task.h>
  85
  86/*
  87 * Protected counters by write_lock_irq(&tasklist_lock)
  88 */
  89unsigned long total_forks;	/* Handle normal Linux uptimes. */
  90int nr_threads;			/* The idle threads do not count.. */
  91
  92int max_threads;		/* tunable limit on nr_threads */
  93
  94DEFINE_PER_CPU(unsigned long, process_counts) = 0;
  95
  96__cacheline_aligned DEFINE_RWLOCK(tasklist_lock);  /* outer */
  97
  98#ifdef CONFIG_PROVE_RCU
  99int lockdep_tasklist_lock_is_held(void)
 100{
 101	return lockdep_is_held(&tasklist_lock);
 102}
 103EXPORT_SYMBOL_GPL(lockdep_tasklist_lock_is_held);
 104#endif /* #ifdef CONFIG_PROVE_RCU */
 105
 106int nr_processes(void)
 107{
 108	int cpu;
 109	int total = 0;
 110
 111	for_each_possible_cpu(cpu)
 112		total += per_cpu(process_counts, cpu);
 113
 114	return total;
 115}
 116
 117#ifndef CONFIG_ARCH_TASK_STRUCT_ALLOCATOR
 
 
 
 
 118static struct kmem_cache *task_struct_cachep;
 119
 120static inline struct task_struct *alloc_task_struct_node(int node)
 121{
 122	return kmem_cache_alloc_node(task_struct_cachep, GFP_KERNEL, node);
 123}
 124
 125void __weak arch_release_task_struct(struct task_struct *tsk) { }
 126
 127static inline void free_task_struct(struct task_struct *tsk)
 128{
 129	arch_release_task_struct(tsk);
 130	kmem_cache_free(task_struct_cachep, tsk);
 131}
 132#endif
 133
 134#ifndef CONFIG_ARCH_THREAD_INFO_ALLOCATOR
 135void __weak arch_release_thread_info(struct thread_info *ti) { }
 136
 137/*
 138 * Allocate pages if THREAD_SIZE is >= PAGE_SIZE, otherwise use a
 139 * kmemcache based allocator.
 140 */
 141# if THREAD_SIZE >= PAGE_SIZE
 142static struct thread_info *alloc_thread_info_node(struct task_struct *tsk,
 143						  int node)
 144{
 145	struct page *page = alloc_pages_node(node, THREADINFO_GFP,
 146					     THREAD_SIZE_ORDER);
 
 
 
 
 147
 148	return page ? page_address(page) : NULL;
 149}
 150
 151static inline void free_thread_info(struct thread_info *ti)
 152{
 153	arch_release_thread_info(ti);
 154	free_pages((unsigned long)ti, THREAD_SIZE_ORDER);
 155}
 156# else
 157static struct kmem_cache *thread_info_cache;
 158
 159static struct thread_info *alloc_thread_info_node(struct task_struct *tsk,
 160						  int node)
 161{
 162	return kmem_cache_alloc_node(thread_info_cache, THREADINFO_GFP, node);
 163}
 164
 165static void free_thread_info(struct thread_info *ti)
 166{
 167	arch_release_thread_info(ti);
 168	kmem_cache_free(thread_info_cache, ti);
 169}
 170
 171void thread_info_cache_init(void)
 172{
 173	thread_info_cache = kmem_cache_create("thread_info", THREAD_SIZE,
 174					      THREAD_SIZE, 0, NULL);
 175	BUG_ON(thread_info_cache == NULL);
 176}
 177# endif
 178#endif
 179
 180/* SLAB cache for signal_struct structures (tsk->signal) */
 181static struct kmem_cache *signal_cachep;
 182
 183/* SLAB cache for sighand_struct structures (tsk->sighand) */
 184struct kmem_cache *sighand_cachep;
 185
 186/* SLAB cache for files_struct structures (tsk->files) */
 187struct kmem_cache *files_cachep;
 188
 189/* SLAB cache for fs_struct structures (tsk->fs) */
 190struct kmem_cache *fs_cachep;
 191
 192/* SLAB cache for vm_area_struct structures */
 193struct kmem_cache *vm_area_cachep;
 194
 195/* SLAB cache for mm_struct structures (tsk->mm) */
 196static struct kmem_cache *mm_cachep;
 197
 198static void account_kernel_stack(struct thread_info *ti, int account)
 199{
 200	struct zone *zone = page_zone(virt_to_page(ti));
 201
 202	mod_zone_page_state(zone, NR_KERNEL_STACK, account);
 203}
 204
 205void free_task(struct task_struct *tsk)
 206{
 
 207	account_kernel_stack(tsk->stack, -1);
 208	free_thread_info(tsk->stack);
 209	rt_mutex_debug_task_free(tsk);
 210	ftrace_graph_exit_task(tsk);
 211	put_seccomp_filter(tsk);
 212	free_task_struct(tsk);
 213}
 214EXPORT_SYMBOL(free_task);
 215
 216static inline void free_signal_struct(struct signal_struct *sig)
 217{
 218	taskstats_tgid_free(sig);
 219	sched_autogroup_exit(sig);
 220	kmem_cache_free(signal_cachep, sig);
 221}
 222
 223static inline void put_signal_struct(struct signal_struct *sig)
 224{
 225	if (atomic_dec_and_test(&sig->sigcnt))
 226		free_signal_struct(sig);
 227}
 228
 229void __put_task_struct(struct task_struct *tsk)
 230{
 231	WARN_ON(!tsk->exit_state);
 232	WARN_ON(atomic_read(&tsk->usage));
 233	WARN_ON(tsk == current);
 234
 235	security_task_free(tsk);
 236	exit_creds(tsk);
 237	delayacct_tsk_free(tsk);
 238	put_signal_struct(tsk->signal);
 239
 240	if (!profile_handoff_task(tsk))
 241		free_task(tsk);
 242}
 243EXPORT_SYMBOL_GPL(__put_task_struct);
 244
 245void __init __weak arch_task_cache_init(void) { }
 
 
 
 
 
 
 246
 247void __init fork_init(unsigned long mempages)
 248{
 249#ifndef CONFIG_ARCH_TASK_STRUCT_ALLOCATOR
 250#ifndef ARCH_MIN_TASKALIGN
 251#define ARCH_MIN_TASKALIGN	L1_CACHE_BYTES
 252#endif
 253	/* create a slab on which task_structs can be allocated */
 254	task_struct_cachep =
 255		kmem_cache_create("task_struct", sizeof(struct task_struct),
 256			ARCH_MIN_TASKALIGN, SLAB_PANIC | SLAB_NOTRACK, NULL);
 257#endif
 258
 259	/* do the arch specific task caches init */
 260	arch_task_cache_init();
 261
 262	/*
 263	 * The default maximum number of threads is set to a safe
 264	 * value: the thread structures can take up at most half
 265	 * of memory.
 266	 */
 267	max_threads = mempages / (8 * THREAD_SIZE / PAGE_SIZE);
 268
 269	/*
 270	 * we need to allow at least 20 threads to boot a system
 271	 */
 272	if (max_threads < 20)
 273		max_threads = 20;
 274
 275	init_task.signal->rlim[RLIMIT_NPROC].rlim_cur = max_threads/2;
 276	init_task.signal->rlim[RLIMIT_NPROC].rlim_max = max_threads/2;
 277	init_task.signal->rlim[RLIMIT_SIGPENDING] =
 278		init_task.signal->rlim[RLIMIT_NPROC];
 279}
 280
 281int __attribute__((weak)) arch_dup_task_struct(struct task_struct *dst,
 282					       struct task_struct *src)
 283{
 284	*dst = *src;
 285	return 0;
 286}
 287
 288static struct task_struct *dup_task_struct(struct task_struct *orig)
 289{
 290	struct task_struct *tsk;
 291	struct thread_info *ti;
 292	unsigned long *stackend;
 293	int node = tsk_fork_get_node(orig);
 294	int err;
 295
 
 
 296	tsk = alloc_task_struct_node(node);
 297	if (!tsk)
 298		return NULL;
 299
 300	ti = alloc_thread_info_node(tsk, node);
 301	if (!ti) {
 302		free_task_struct(tsk);
 303		return NULL;
 304	}
 305
 306	err = arch_dup_task_struct(tsk, orig);
 
 
 307
 308	/*
 309	 * We defer looking at err, because we will need this setup
 310	 * for the clean up path to work correctly.
 311	 */
 312	tsk->stack = ti;
 313	setup_thread_stack(tsk, orig);
 314
 
 315	if (err)
 316		goto out;
 317
 
 318	clear_user_return_notifier(tsk);
 319	clear_tsk_need_resched(tsk);
 320	stackend = end_of_stack(tsk);
 321	*stackend = STACK_END_MAGIC;	/* for overflow detection */
 322
 323#ifdef CONFIG_CC_STACKPROTECTOR
 324	tsk->stack_canary = get_random_int();
 325#endif
 326
 327	/*
 328	 * One for us, one for whoever does the "release_task()" (usually
 329	 * parent)
 330	 */
 331	atomic_set(&tsk->usage, 2);
 332#ifdef CONFIG_BLK_DEV_IO_TRACE
 333	tsk->btrace_seq = 0;
 334#endif
 335	tsk->splice_pipe = NULL;
 336
 337	account_kernel_stack(ti, 1);
 338
 339	return tsk;
 340
 341out:
 342	free_thread_info(ti);
 343	free_task_struct(tsk);
 344	return NULL;
 345}
 346
 347#ifdef CONFIG_MMU
 348static int dup_mmap(struct mm_struct *mm, struct mm_struct *oldmm)
 349{
 350	struct vm_area_struct *mpnt, *tmp, *prev, **pprev;
 351	struct rb_node **rb_link, *rb_parent;
 352	int retval;
 353	unsigned long charge;
 354	struct mempolicy *pol;
 355
 356	down_write(&oldmm->mmap_sem);
 357	flush_cache_dup_mm(oldmm);
 358	/*
 359	 * Not linked in yet - no deadlock potential:
 360	 */
 361	down_write_nested(&mm->mmap_sem, SINGLE_DEPTH_NESTING);
 362
 363	mm->locked_vm = 0;
 364	mm->mmap = NULL;
 365	mm->mmap_cache = NULL;
 366	mm->free_area_cache = oldmm->mmap_base;
 367	mm->cached_hole_size = ~0UL;
 368	mm->map_count = 0;
 369	cpumask_clear(mm_cpumask(mm));
 370	mm->mm_rb = RB_ROOT;
 371	rb_link = &mm->mm_rb.rb_node;
 372	rb_parent = NULL;
 373	pprev = &mm->mmap;
 374	retval = ksm_fork(mm, oldmm);
 375	if (retval)
 376		goto out;
 377	retval = khugepaged_fork(mm, oldmm);
 378	if (retval)
 379		goto out;
 380
 381	prev = NULL;
 382	for (mpnt = oldmm->mmap; mpnt; mpnt = mpnt->vm_next) {
 383		struct file *file;
 384
 385		if (mpnt->vm_flags & VM_DONTCOPY) {
 386			long pages = vma_pages(mpnt);
 387			mm->total_vm -= pages;
 388			vm_stat_account(mm, mpnt->vm_flags, mpnt->vm_file,
 389								-pages);
 390			continue;
 391		}
 392		charge = 0;
 393		if (mpnt->vm_flags & VM_ACCOUNT) {
 394			unsigned long len;
 395			len = (mpnt->vm_end - mpnt->vm_start) >> PAGE_SHIFT;
 396			if (security_vm_enough_memory_mm(oldmm, len)) /* sic */
 397				goto fail_nomem;
 398			charge = len;
 399		}
 400		tmp = kmem_cache_alloc(vm_area_cachep, GFP_KERNEL);
 401		if (!tmp)
 402			goto fail_nomem;
 403		*tmp = *mpnt;
 404		INIT_LIST_HEAD(&tmp->anon_vma_chain);
 405		pol = mpol_dup(vma_policy(mpnt));
 406		retval = PTR_ERR(pol);
 407		if (IS_ERR(pol))
 408			goto fail_nomem_policy;
 409		vma_set_policy(tmp, pol);
 410		tmp->vm_mm = mm;
 411		if (anon_vma_fork(tmp, mpnt))
 412			goto fail_nomem_anon_vma_fork;
 413		tmp->vm_flags &= ~VM_LOCKED;
 414		tmp->vm_next = tmp->vm_prev = NULL;
 415		file = tmp->vm_file;
 416		if (file) {
 417			struct inode *inode = file->f_path.dentry->d_inode;
 418			struct address_space *mapping = file->f_mapping;
 419
 420			get_file(file);
 421			if (tmp->vm_flags & VM_DENYWRITE)
 422				atomic_dec(&inode->i_writecount);
 423			mutex_lock(&mapping->i_mmap_mutex);
 424			if (tmp->vm_flags & VM_SHARED)
 425				mapping->i_mmap_writable++;
 426			flush_dcache_mmap_lock(mapping);
 427			/* insert tmp into the share list, just after mpnt */
 428			vma_prio_tree_add(tmp, mpnt);
 429			flush_dcache_mmap_unlock(mapping);
 430			mutex_unlock(&mapping->i_mmap_mutex);
 431		}
 432
 433		/*
 434		 * Clear hugetlb-related page reserves for children. This only
 435		 * affects MAP_PRIVATE mappings. Faults generated by the child
 436		 * are not guaranteed to succeed, even if read-only
 437		 */
 438		if (is_vm_hugetlb_page(tmp))
 439			reset_vma_resv_huge_pages(tmp);
 440
 441		/*
 442		 * Link in the new vma and copy the page table entries.
 443		 */
 444		*pprev = tmp;
 445		pprev = &tmp->vm_next;
 446		tmp->vm_prev = prev;
 447		prev = tmp;
 448
 449		__vma_link_rb(mm, tmp, rb_link, rb_parent);
 450		rb_link = &tmp->vm_rb.rb_right;
 451		rb_parent = &tmp->vm_rb;
 452
 453		mm->map_count++;
 454		retval = copy_page_range(mm, oldmm, mpnt);
 455
 456		if (tmp->vm_ops && tmp->vm_ops->open)
 457			tmp->vm_ops->open(tmp);
 458
 459		if (retval)
 460			goto out;
 461
 462		if (file)
 463			uprobe_mmap(tmp);
 464	}
 465	/* a new mm has just been created */
 466	arch_dup_mmap(oldmm, mm);
 467	retval = 0;
 468out:
 469	up_write(&mm->mmap_sem);
 470	flush_tlb_mm(oldmm);
 471	up_write(&oldmm->mmap_sem);
 472	return retval;
 473fail_nomem_anon_vma_fork:
 474	mpol_put(pol);
 475fail_nomem_policy:
 476	kmem_cache_free(vm_area_cachep, tmp);
 477fail_nomem:
 478	retval = -ENOMEM;
 479	vm_unacct_memory(charge);
 480	goto out;
 481}
 482
 483static inline int mm_alloc_pgd(struct mm_struct *mm)
 484{
 485	mm->pgd = pgd_alloc(mm);
 486	if (unlikely(!mm->pgd))
 487		return -ENOMEM;
 488	return 0;
 489}
 490
 491static inline void mm_free_pgd(struct mm_struct *mm)
 492{
 493	pgd_free(mm, mm->pgd);
 494}
 495#else
 496#define dup_mmap(mm, oldmm)	(0)
 497#define mm_alloc_pgd(mm)	(0)
 498#define mm_free_pgd(mm)
 499#endif /* CONFIG_MMU */
 500
 501__cacheline_aligned_in_smp DEFINE_SPINLOCK(mmlist_lock);
 502
 503#define allocate_mm()	(kmem_cache_alloc(mm_cachep, GFP_KERNEL))
 504#define free_mm(mm)	(kmem_cache_free(mm_cachep, (mm)))
 505
 506static unsigned long default_dump_filter = MMF_DUMP_FILTER_DEFAULT;
 507
 508static int __init coredump_filter_setup(char *s)
 509{
 510	default_dump_filter =
 511		(simple_strtoul(s, NULL, 0) << MMF_DUMP_FILTER_SHIFT) &
 512		MMF_DUMP_FILTER_MASK;
 513	return 1;
 514}
 515
 516__setup("coredump_filter=", coredump_filter_setup);
 517
 518#include <linux/init_task.h>
 519
 520static void mm_init_aio(struct mm_struct *mm)
 521{
 522#ifdef CONFIG_AIO
 523	spin_lock_init(&mm->ioctx_lock);
 524	INIT_HLIST_HEAD(&mm->ioctx_list);
 525#endif
 526}
 527
 528static struct mm_struct *mm_init(struct mm_struct *mm, struct task_struct *p)
 529{
 530	atomic_set(&mm->mm_users, 1);
 531	atomic_set(&mm->mm_count, 1);
 532	init_rwsem(&mm->mmap_sem);
 533	INIT_LIST_HEAD(&mm->mmlist);
 534	mm->flags = (current->mm) ?
 535		(current->mm->flags & MMF_INIT_MASK) : default_dump_filter;
 536	mm->core_state = NULL;
 537	mm->nr_ptes = 0;
 538	memset(&mm->rss_stat, 0, sizeof(mm->rss_stat));
 539	spin_lock_init(&mm->page_table_lock);
 540	mm->free_area_cache = TASK_UNMAPPED_BASE;
 541	mm->cached_hole_size = ~0UL;
 542	mm_init_aio(mm);
 543	mm_init_owner(mm, p);
 
 544
 545	if (likely(!mm_alloc_pgd(mm))) {
 546		mm->def_flags = 0;
 547		mmu_notifier_mm_init(mm);
 548		return mm;
 549	}
 550
 551	free_mm(mm);
 552	return NULL;
 553}
 554
 555static void check_mm(struct mm_struct *mm)
 556{
 557	int i;
 558
 559	for (i = 0; i < NR_MM_COUNTERS; i++) {
 560		long x = atomic_long_read(&mm->rss_stat.count[i]);
 561
 562		if (unlikely(x))
 563			printk(KERN_ALERT "BUG: Bad rss-counter state "
 564					  "mm:%p idx:%d val:%ld\n", mm, i, x);
 565	}
 566
 567#ifdef CONFIG_TRANSPARENT_HUGEPAGE
 568	VM_BUG_ON(mm->pmd_huge_pte);
 569#endif
 570}
 571
 572/*
 573 * Allocate and initialize an mm_struct.
 574 */
 575struct mm_struct *mm_alloc(void)
 576{
 577	struct mm_struct *mm;
 578
 579	mm = allocate_mm();
 580	if (!mm)
 581		return NULL;
 582
 583	memset(mm, 0, sizeof(*mm));
 584	mm_init_cpumask(mm);
 585	return mm_init(mm, current);
 586}
 587
 588/*
 589 * Called when the last reference to the mm
 590 * is dropped: either by a lazy thread or by
 591 * mmput. Free the page directory and the mm.
 592 */
 593void __mmdrop(struct mm_struct *mm)
 594{
 595	BUG_ON(mm == &init_mm);
 596	mm_free_pgd(mm);
 597	destroy_context(mm);
 598	mmu_notifier_mm_destroy(mm);
 599	check_mm(mm);
 
 
 600	free_mm(mm);
 601}
 602EXPORT_SYMBOL_GPL(__mmdrop);
 603
 604/*
 605 * Decrement the use count and release all resources for an mm.
 606 */
 607void mmput(struct mm_struct *mm)
 608{
 609	might_sleep();
 610
 611	if (atomic_dec_and_test(&mm->mm_users)) {
 612		uprobe_clear_state(mm);
 613		exit_aio(mm);
 614		ksm_exit(mm);
 615		khugepaged_exit(mm); /* must run before exit_mmap */
 616		exit_mmap(mm);
 617		set_mm_exe_file(mm, NULL);
 618		if (!list_empty(&mm->mmlist)) {
 619			spin_lock(&mmlist_lock);
 620			list_del(&mm->mmlist);
 621			spin_unlock(&mmlist_lock);
 622		}
 
 623		if (mm->binfmt)
 624			module_put(mm->binfmt->module);
 625		mmdrop(mm);
 626	}
 627}
 628EXPORT_SYMBOL_GPL(mmput);
 629
 630/*
 631 * We added or removed a vma mapping the executable. The vmas are only mapped
 632 * during exec and are not mapped with the mmap system call.
 633 * Callers must hold down_write() on the mm's mmap_sem for these
 634 */
 635void added_exe_file_vma(struct mm_struct *mm)
 636{
 637	mm->num_exe_file_vmas++;
 638}
 639
 640void removed_exe_file_vma(struct mm_struct *mm)
 641{
 642	mm->num_exe_file_vmas--;
 643	if ((mm->num_exe_file_vmas == 0) && mm->exe_file) {
 644		fput(mm->exe_file);
 645		mm->exe_file = NULL;
 646	}
 647
 648}
 649
 650void set_mm_exe_file(struct mm_struct *mm, struct file *new_exe_file)
 651{
 652	if (new_exe_file)
 653		get_file(new_exe_file);
 654	if (mm->exe_file)
 655		fput(mm->exe_file);
 656	mm->exe_file = new_exe_file;
 657	mm->num_exe_file_vmas = 0;
 658}
 659
 660struct file *get_mm_exe_file(struct mm_struct *mm)
 661{
 662	struct file *exe_file;
 663
 664	/* We need mmap_sem to protect against races with removal of
 665	 * VM_EXECUTABLE vmas */
 666	down_read(&mm->mmap_sem);
 667	exe_file = mm->exe_file;
 668	if (exe_file)
 669		get_file(exe_file);
 670	up_read(&mm->mmap_sem);
 671	return exe_file;
 672}
 673
 674static void dup_mm_exe_file(struct mm_struct *oldmm, struct mm_struct *newmm)
 675{
 676	/* It's safe to write the exe_file pointer without exe_file_lock because
 677	 * this is called during fork when the task is not yet in /proc */
 678	newmm->exe_file = get_mm_exe_file(oldmm);
 679}
 680
 681/**
 682 * get_task_mm - acquire a reference to the task's mm
 683 *
 684 * Returns %NULL if the task has no mm.  Checks PF_KTHREAD (meaning
 685 * this kernel workthread has transiently adopted a user mm with use_mm,
 686 * to do its AIO) is not set and if so returns a reference to it, after
 687 * bumping up the use count.  User must release the mm via mmput()
 688 * after use.  Typically used by /proc and ptrace.
 689 */
 690struct mm_struct *get_task_mm(struct task_struct *task)
 691{
 692	struct mm_struct *mm;
 693
 694	task_lock(task);
 695	mm = task->mm;
 696	if (mm) {
 697		if (task->flags & PF_KTHREAD)
 698			mm = NULL;
 699		else
 700			atomic_inc(&mm->mm_users);
 701	}
 702	task_unlock(task);
 703	return mm;
 704}
 705EXPORT_SYMBOL_GPL(get_task_mm);
 706
 707struct mm_struct *mm_access(struct task_struct *task, unsigned int mode)
 708{
 709	struct mm_struct *mm;
 710	int err;
 711
 712	err =  mutex_lock_killable(&task->signal->cred_guard_mutex);
 713	if (err)
 714		return ERR_PTR(err);
 715
 716	mm = get_task_mm(task);
 717	if (mm && mm != current->mm &&
 718			!ptrace_may_access(task, mode)) {
 719		mmput(mm);
 720		mm = ERR_PTR(-EACCES);
 721	}
 722	mutex_unlock(&task->signal->cred_guard_mutex);
 723
 724	return mm;
 725}
 726
 727static void complete_vfork_done(struct task_struct *tsk)
 728{
 729	struct completion *vfork;
 730
 731	task_lock(tsk);
 732	vfork = tsk->vfork_done;
 733	if (likely(vfork)) {
 734		tsk->vfork_done = NULL;
 735		complete(vfork);
 736	}
 737	task_unlock(tsk);
 738}
 739
 740static int wait_for_vfork_done(struct task_struct *child,
 741				struct completion *vfork)
 742{
 743	int killed;
 744
 745	freezer_do_not_count();
 746	killed = wait_for_completion_killable(vfork);
 747	freezer_count();
 748
 749	if (killed) {
 750		task_lock(child);
 751		child->vfork_done = NULL;
 752		task_unlock(child);
 753	}
 754
 755	put_task_struct(child);
 756	return killed;
 757}
 758
 759/* Please note the differences between mmput and mm_release.
 760 * mmput is called whenever we stop holding onto a mm_struct,
 761 * error success whatever.
 762 *
 763 * mm_release is called after a mm_struct has been removed
 764 * from the current process.
 765 *
 766 * This difference is important for error handling, when we
 767 * only half set up a mm_struct for a new process and need to restore
 768 * the old one.  Because we mmput the new mm_struct before
 769 * restoring the old one. . .
 770 * Eric Biederman 10 January 1998
 771 */
 772void mm_release(struct task_struct *tsk, struct mm_struct *mm)
 773{
 
 
 774	/* Get rid of any futexes when releasing the mm */
 775#ifdef CONFIG_FUTEX
 776	if (unlikely(tsk->robust_list)) {
 777		exit_robust_list(tsk);
 778		tsk->robust_list = NULL;
 779	}
 780#ifdef CONFIG_COMPAT
 781	if (unlikely(tsk->compat_robust_list)) {
 782		compat_exit_robust_list(tsk);
 783		tsk->compat_robust_list = NULL;
 784	}
 785#endif
 786	if (unlikely(!list_empty(&tsk->pi_state_list)))
 787		exit_pi_state_list(tsk);
 788#endif
 789
 790	uprobe_free_utask(tsk);
 791
 792	/* Get rid of any cached register state */
 793	deactivate_mm(tsk, mm);
 794
 
 
 
 
 
 
 795	/*
 796	 * If we're exiting normally, clear a user-space tid field if
 797	 * requested.  We leave this alone when dying by signal, to leave
 798	 * the value intact in a core dump, and to save the unnecessary
 799	 * trouble, say, a killed vfork parent shouldn't touch this mm.
 800	 * Userland only wants this done for a sys_exit.
 801	 */
 802	if (tsk->clear_child_tid) {
 803		if (!(tsk->flags & PF_SIGNALED) &&
 804		    atomic_read(&mm->mm_users) > 1) {
 805			/*
 806			 * We don't check the error code - if userspace has
 807			 * not set up a proper pointer then tough luck.
 808			 */
 809			put_user(0, tsk->clear_child_tid);
 810			sys_futex(tsk->clear_child_tid, FUTEX_WAKE,
 811					1, NULL, NULL, 0);
 812		}
 813		tsk->clear_child_tid = NULL;
 814	}
 815
 816	/*
 817	 * All done, finally we can wake up parent and return this mm to him.
 818	 * Also kthread_stop() uses this completion for synchronization.
 819	 */
 820	if (tsk->vfork_done)
 821		complete_vfork_done(tsk);
 822}
 823
 824/*
 825 * Allocate a new mm structure and copy contents from the
 826 * mm structure of the passed in task structure.
 827 */
 828struct mm_struct *dup_mm(struct task_struct *tsk)
 829{
 830	struct mm_struct *mm, *oldmm = current->mm;
 831	int err;
 832
 833	if (!oldmm)
 834		return NULL;
 835
 836	mm = allocate_mm();
 837	if (!mm)
 838		goto fail_nomem;
 839
 840	memcpy(mm, oldmm, sizeof(*mm));
 841	mm_init_cpumask(mm);
 842
 
 
 
 
 843#ifdef CONFIG_TRANSPARENT_HUGEPAGE
 844	mm->pmd_huge_pte = NULL;
 845#endif
 846	uprobe_reset_state(mm);
 847
 848	if (!mm_init(mm, tsk))
 849		goto fail_nomem;
 850
 851	if (init_new_context(tsk, mm))
 852		goto fail_nocontext;
 853
 854	dup_mm_exe_file(oldmm, mm);
 855
 856	err = dup_mmap(mm, oldmm);
 857	if (err)
 858		goto free_pt;
 859
 860	mm->hiwater_rss = get_mm_rss(mm);
 861	mm->hiwater_vm = mm->total_vm;
 862
 863	if (mm->binfmt && !try_module_get(mm->binfmt->module))
 864		goto free_pt;
 865
 866	return mm;
 867
 868free_pt:
 869	/* don't put binfmt in mmput, we haven't got module yet */
 870	mm->binfmt = NULL;
 871	mmput(mm);
 872
 873fail_nomem:
 874	return NULL;
 875
 876fail_nocontext:
 877	/*
 878	 * If init_new_context() failed, we cannot use mmput() to free the mm
 879	 * because it calls destroy_context()
 880	 */
 881	mm_free_pgd(mm);
 882	free_mm(mm);
 883	return NULL;
 884}
 885
 886static int copy_mm(unsigned long clone_flags, struct task_struct *tsk)
 887{
 888	struct mm_struct *mm, *oldmm;
 889	int retval;
 890
 891	tsk->min_flt = tsk->maj_flt = 0;
 892	tsk->nvcsw = tsk->nivcsw = 0;
 893#ifdef CONFIG_DETECT_HUNG_TASK
 894	tsk->last_switch_count = tsk->nvcsw + tsk->nivcsw;
 895#endif
 896
 897	tsk->mm = NULL;
 898	tsk->active_mm = NULL;
 899
 900	/*
 901	 * Are we cloning a kernel thread?
 902	 *
 903	 * We need to steal a active VM for that..
 904	 */
 905	oldmm = current->mm;
 906	if (!oldmm)
 907		return 0;
 908
 909	if (clone_flags & CLONE_VM) {
 910		atomic_inc(&oldmm->mm_users);
 911		mm = oldmm;
 912		goto good_mm;
 913	}
 914
 915	retval = -ENOMEM;
 916	mm = dup_mm(tsk);
 917	if (!mm)
 918		goto fail_nomem;
 919
 920good_mm:
 
 
 
 
 
 
 921	tsk->mm = mm;
 922	tsk->active_mm = mm;
 923	return 0;
 924
 925fail_nomem:
 926	return retval;
 927}
 928
 929static int copy_fs(unsigned long clone_flags, struct task_struct *tsk)
 930{
 931	struct fs_struct *fs = current->fs;
 932	if (clone_flags & CLONE_FS) {
 933		/* tsk->fs is already what we want */
 934		spin_lock(&fs->lock);
 935		if (fs->in_exec) {
 936			spin_unlock(&fs->lock);
 937			return -EAGAIN;
 938		}
 939		fs->users++;
 940		spin_unlock(&fs->lock);
 941		return 0;
 942	}
 943	tsk->fs = copy_fs_struct(fs);
 944	if (!tsk->fs)
 945		return -ENOMEM;
 946	return 0;
 947}
 948
 949static int copy_files(unsigned long clone_flags, struct task_struct *tsk)
 950{
 951	struct files_struct *oldf, *newf;
 952	int error = 0;
 953
 954	/*
 955	 * A background process may not have any files ...
 956	 */
 957	oldf = current->files;
 958	if (!oldf)
 959		goto out;
 960
 961	if (clone_flags & CLONE_FILES) {
 962		atomic_inc(&oldf->count);
 963		goto out;
 964	}
 965
 966	newf = dup_fd(oldf, &error);
 967	if (!newf)
 968		goto out;
 969
 970	tsk->files = newf;
 971	error = 0;
 972out:
 973	return error;
 974}
 975
 976static int copy_io(unsigned long clone_flags, struct task_struct *tsk)
 977{
 978#ifdef CONFIG_BLOCK
 979	struct io_context *ioc = current->io_context;
 980	struct io_context *new_ioc;
 981
 982	if (!ioc)
 983		return 0;
 984	/*
 985	 * Share io context with parent, if CLONE_IO is set
 986	 */
 987	if (clone_flags & CLONE_IO) {
 988		ioc_task_link(ioc);
 989		tsk->io_context = ioc;
 
 990	} else if (ioprio_valid(ioc->ioprio)) {
 991		new_ioc = get_task_io_context(tsk, GFP_KERNEL, NUMA_NO_NODE);
 992		if (unlikely(!new_ioc))
 993			return -ENOMEM;
 994
 995		new_ioc->ioprio = ioc->ioprio;
 996		put_io_context(new_ioc);
 997	}
 998#endif
 999	return 0;
1000}
1001
1002static int copy_sighand(unsigned long clone_flags, struct task_struct *tsk)
1003{
1004	struct sighand_struct *sig;
1005
1006	if (clone_flags & CLONE_SIGHAND) {
1007		atomic_inc(&current->sighand->count);
1008		return 0;
1009	}
1010	sig = kmem_cache_alloc(sighand_cachep, GFP_KERNEL);
1011	rcu_assign_pointer(tsk->sighand, sig);
1012	if (!sig)
1013		return -ENOMEM;
1014	atomic_set(&sig->count, 1);
1015	memcpy(sig->action, current->sighand->action, sizeof(sig->action));
1016	return 0;
1017}
1018
1019void __cleanup_sighand(struct sighand_struct *sighand)
1020{
1021	if (atomic_dec_and_test(&sighand->count)) {
1022		signalfd_cleanup(sighand);
1023		kmem_cache_free(sighand_cachep, sighand);
1024	}
1025}
1026
1027
1028/*
1029 * Initialize POSIX timer handling for a thread group.
1030 */
1031static void posix_cpu_timers_init_group(struct signal_struct *sig)
1032{
1033	unsigned long cpu_limit;
1034
1035	/* Thread group counters. */
1036	thread_group_cputime_init(sig);
1037
1038	cpu_limit = ACCESS_ONCE(sig->rlim[RLIMIT_CPU].rlim_cur);
1039	if (cpu_limit != RLIM_INFINITY) {
1040		sig->cputime_expires.prof_exp = secs_to_cputime(cpu_limit);
1041		sig->cputimer.running = 1;
1042	}
1043
1044	/* The timer lists. */
1045	INIT_LIST_HEAD(&sig->cpu_timers[0]);
1046	INIT_LIST_HEAD(&sig->cpu_timers[1]);
1047	INIT_LIST_HEAD(&sig->cpu_timers[2]);
1048}
1049
1050static int copy_signal(unsigned long clone_flags, struct task_struct *tsk)
1051{
1052	struct signal_struct *sig;
1053
1054	if (clone_flags & CLONE_THREAD)
1055		return 0;
1056
1057	sig = kmem_cache_zalloc(signal_cachep, GFP_KERNEL);
1058	tsk->signal = sig;
1059	if (!sig)
1060		return -ENOMEM;
1061
1062	sig->nr_threads = 1;
1063	atomic_set(&sig->live, 1);
1064	atomic_set(&sig->sigcnt, 1);
1065	init_waitqueue_head(&sig->wait_chldexit);
1066	if (clone_flags & CLONE_NEWPID)
1067		sig->flags |= SIGNAL_UNKILLABLE;
1068	sig->curr_target = tsk;
1069	init_sigpending(&sig->shared_pending);
1070	INIT_LIST_HEAD(&sig->posix_timers);
1071
1072	hrtimer_init(&sig->real_timer, CLOCK_MONOTONIC, HRTIMER_MODE_REL);
1073	sig->real_timer.function = it_real_fn;
1074
1075	task_lock(current->group_leader);
1076	memcpy(sig->rlim, current->signal->rlim, sizeof sig->rlim);
1077	task_unlock(current->group_leader);
1078
1079	posix_cpu_timers_init_group(sig);
1080
1081	tty_audit_fork(sig);
1082	sched_autogroup_fork(sig);
1083
1084#ifdef CONFIG_CGROUPS
1085	init_rwsem(&sig->group_rwsem);
1086#endif
1087
1088	sig->oom_adj = current->signal->oom_adj;
1089	sig->oom_score_adj = current->signal->oom_score_adj;
1090	sig->oom_score_adj_min = current->signal->oom_score_adj_min;
1091
1092	sig->has_child_subreaper = current->signal->has_child_subreaper ||
1093				   current->signal->is_child_subreaper;
1094
1095	mutex_init(&sig->cred_guard_mutex);
1096
1097	return 0;
1098}
1099
1100static void copy_flags(unsigned long clone_flags, struct task_struct *p)
1101{
1102	unsigned long new_flags = p->flags;
1103
1104	new_flags &= ~(PF_SUPERPRIV | PF_WQ_WORKER);
1105	new_flags |= PF_FORKNOEXEC;
 
1106	p->flags = new_flags;
 
1107}
1108
1109SYSCALL_DEFINE1(set_tid_address, int __user *, tidptr)
1110{
1111	current->clear_child_tid = tidptr;
1112
1113	return task_pid_vnr(current);
1114}
1115
1116static void rt_mutex_init_task(struct task_struct *p)
1117{
1118	raw_spin_lock_init(&p->pi_lock);
1119#ifdef CONFIG_RT_MUTEXES
1120	plist_head_init(&p->pi_waiters);
1121	p->pi_blocked_on = NULL;
1122#endif
1123}
1124
1125#ifdef CONFIG_MM_OWNER
1126void mm_init_owner(struct mm_struct *mm, struct task_struct *p)
1127{
1128	mm->owner = p;
1129}
1130#endif /* CONFIG_MM_OWNER */
1131
1132/*
1133 * Initialize POSIX timer handling for a single task.
1134 */
1135static void posix_cpu_timers_init(struct task_struct *tsk)
1136{
1137	tsk->cputime_expires.prof_exp = 0;
1138	tsk->cputime_expires.virt_exp = 0;
1139	tsk->cputime_expires.sched_exp = 0;
1140	INIT_LIST_HEAD(&tsk->cpu_timers[0]);
1141	INIT_LIST_HEAD(&tsk->cpu_timers[1]);
1142	INIT_LIST_HEAD(&tsk->cpu_timers[2]);
1143}
1144
1145/*
1146 * This creates a new process as a copy of the old one,
1147 * but does not actually start it yet.
1148 *
1149 * It copies the registers, and all the appropriate
1150 * parts of the process environment (as per the clone
1151 * flags). The actual kick-off is left to the caller.
1152 */
1153static struct task_struct *copy_process(unsigned long clone_flags,
1154					unsigned long stack_start,
1155					struct pt_regs *regs,
1156					unsigned long stack_size,
1157					int __user *child_tidptr,
1158					struct pid *pid,
1159					int trace)
1160{
1161	int retval;
1162	struct task_struct *p;
1163	int cgroup_callbacks_done = 0;
1164
1165	if ((clone_flags & (CLONE_NEWNS|CLONE_FS)) == (CLONE_NEWNS|CLONE_FS))
1166		return ERR_PTR(-EINVAL);
1167
1168	/*
1169	 * Thread groups must share signals as well, and detached threads
1170	 * can only be started up within the thread group.
1171	 */
1172	if ((clone_flags & CLONE_THREAD) && !(clone_flags & CLONE_SIGHAND))
1173		return ERR_PTR(-EINVAL);
1174
1175	/*
1176	 * Shared signal handlers imply shared VM. By way of the above,
1177	 * thread groups also imply shared VM. Blocking this case allows
1178	 * for various simplifications in other code.
1179	 */
1180	if ((clone_flags & CLONE_SIGHAND) && !(clone_flags & CLONE_VM))
1181		return ERR_PTR(-EINVAL);
1182
1183	/*
1184	 * Siblings of global init remain as zombies on exit since they are
1185	 * not reaped by their parent (swapper). To solve this and to avoid
1186	 * multi-rooted process trees, prevent global and container-inits
1187	 * from creating siblings.
1188	 */
1189	if ((clone_flags & CLONE_PARENT) &&
1190				current->signal->flags & SIGNAL_UNKILLABLE)
1191		return ERR_PTR(-EINVAL);
1192
1193	retval = security_task_create(clone_flags);
1194	if (retval)
1195		goto fork_out;
1196
1197	retval = -ENOMEM;
1198	p = dup_task_struct(current);
1199	if (!p)
1200		goto fork_out;
1201
1202	ftrace_graph_init_task(p);
1203	get_seccomp_filter(p);
1204
1205	rt_mutex_init_task(p);
1206
1207#ifdef CONFIG_PROVE_LOCKING
1208	DEBUG_LOCKS_WARN_ON(!p->hardirqs_enabled);
1209	DEBUG_LOCKS_WARN_ON(!p->softirqs_enabled);
1210#endif
1211	retval = -EAGAIN;
1212	if (atomic_read(&p->real_cred->user->processes) >=
1213			task_rlimit(p, RLIMIT_NPROC)) {
1214		if (!capable(CAP_SYS_ADMIN) && !capable(CAP_SYS_RESOURCE) &&
1215		    p->real_cred->user != INIT_USER)
1216			goto bad_fork_free;
1217	}
1218	current->flags &= ~PF_NPROC_EXCEEDED;
1219
1220	retval = copy_creds(p, clone_flags);
1221	if (retval < 0)
1222		goto bad_fork_free;
1223
1224	/*
1225	 * If multiple threads are within copy_process(), then this check
1226	 * triggers too late. This doesn't hurt, the check is only there
1227	 * to stop root fork bombs.
1228	 */
1229	retval = -EAGAIN;
1230	if (nr_threads >= max_threads)
1231		goto bad_fork_cleanup_count;
1232
1233	if (!try_module_get(task_thread_info(p)->exec_domain->module))
1234		goto bad_fork_cleanup_count;
1235
1236	p->did_exec = 0;
1237	delayacct_tsk_init(p);	/* Must remain after dup_task_struct() */
1238	copy_flags(clone_flags, p);
1239	INIT_LIST_HEAD(&p->children);
1240	INIT_LIST_HEAD(&p->sibling);
1241	rcu_copy_process(p);
1242	p->vfork_done = NULL;
1243	spin_lock_init(&p->alloc_lock);
1244
1245	init_sigpending(&p->pending);
1246
1247	p->utime = p->stime = p->gtime = 0;
1248	p->utimescaled = p->stimescaled = 0;
 
 
 
1249#ifndef CONFIG_VIRT_CPU_ACCOUNTING
1250	p->prev_utime = p->prev_stime = 0;
 
1251#endif
1252#if defined(SPLIT_RSS_COUNTING)
1253	memset(&p->rss_stat, 0, sizeof(p->rss_stat));
1254#endif
1255
1256	p->default_timer_slack_ns = current->timer_slack_ns;
1257
1258	task_io_accounting_init(&p->ioac);
1259	acct_clear_integrals(p);
1260
1261	posix_cpu_timers_init(p);
1262
1263	do_posix_clock_monotonic_gettime(&p->start_time);
1264	p->real_start_time = p->start_time;
1265	monotonic_to_bootbased(&p->real_start_time);
1266	p->io_context = NULL;
1267	p->audit_context = NULL;
1268	if (clone_flags & CLONE_THREAD)
1269		threadgroup_change_begin(current);
1270	cgroup_fork(p);
1271#ifdef CONFIG_NUMA
1272	p->mempolicy = mpol_dup(p->mempolicy);
1273	if (IS_ERR(p->mempolicy)) {
1274		retval = PTR_ERR(p->mempolicy);
1275		p->mempolicy = NULL;
1276		goto bad_fork_cleanup_cgroup;
1277	}
1278	mpol_fix_fork_child_flag(p);
1279#endif
1280#ifdef CONFIG_CPUSETS
1281	p->cpuset_mem_spread_rotor = NUMA_NO_NODE;
1282	p->cpuset_slab_spread_rotor = NUMA_NO_NODE;
1283	seqcount_init(&p->mems_allowed_seq);
1284#endif
1285#ifdef CONFIG_TRACE_IRQFLAGS
1286	p->irq_events = 0;
1287#ifdef __ARCH_WANT_INTERRUPTS_ON_CTXSW
1288	p->hardirqs_enabled = 1;
1289#else
1290	p->hardirqs_enabled = 0;
1291#endif
1292	p->hardirq_enable_ip = 0;
1293	p->hardirq_enable_event = 0;
1294	p->hardirq_disable_ip = _THIS_IP_;
1295	p->hardirq_disable_event = 0;
1296	p->softirqs_enabled = 1;
1297	p->softirq_enable_ip = _THIS_IP_;
1298	p->softirq_enable_event = 0;
1299	p->softirq_disable_ip = 0;
1300	p->softirq_disable_event = 0;
1301	p->hardirq_context = 0;
1302	p->softirq_context = 0;
1303#endif
1304#ifdef CONFIG_LOCKDEP
1305	p->lockdep_depth = 0; /* no locks held yet */
1306	p->curr_chain_key = 0;
1307	p->lockdep_recursion = 0;
1308#endif
1309
1310#ifdef CONFIG_DEBUG_MUTEXES
1311	p->blocked_on = NULL; /* not blocked yet */
1312#endif
1313#ifdef CONFIG_CGROUP_MEM_RES_CTLR
1314	p->memcg_batch.do_batch = 0;
1315	p->memcg_batch.memcg = NULL;
1316#endif
1317
1318	/* Perform scheduler related setup. Assign this task to a CPU. */
1319	sched_fork(p);
1320
1321	retval = perf_event_init_task(p);
1322	if (retval)
1323		goto bad_fork_cleanup_policy;
1324	retval = audit_alloc(p);
1325	if (retval)
1326		goto bad_fork_cleanup_policy;
1327	/* copy all the process information */
1328	retval = copy_semundo(clone_flags, p);
1329	if (retval)
1330		goto bad_fork_cleanup_audit;
1331	retval = copy_files(clone_flags, p);
1332	if (retval)
1333		goto bad_fork_cleanup_semundo;
1334	retval = copy_fs(clone_flags, p);
1335	if (retval)
1336		goto bad_fork_cleanup_files;
1337	retval = copy_sighand(clone_flags, p);
1338	if (retval)
1339		goto bad_fork_cleanup_fs;
1340	retval = copy_signal(clone_flags, p);
1341	if (retval)
1342		goto bad_fork_cleanup_sighand;
1343	retval = copy_mm(clone_flags, p);
1344	if (retval)
1345		goto bad_fork_cleanup_signal;
1346	retval = copy_namespaces(clone_flags, p);
1347	if (retval)
1348		goto bad_fork_cleanup_mm;
1349	retval = copy_io(clone_flags, p);
1350	if (retval)
1351		goto bad_fork_cleanup_namespaces;
1352	retval = copy_thread(clone_flags, stack_start, stack_size, p, regs);
1353	if (retval)
1354		goto bad_fork_cleanup_io;
1355
1356	if (pid != &init_struct_pid) {
1357		retval = -ENOMEM;
1358		pid = alloc_pid(p->nsproxy->pid_ns);
1359		if (!pid)
1360			goto bad_fork_cleanup_io;
1361	}
1362
1363	p->pid = pid_nr(pid);
1364	p->tgid = p->pid;
1365	if (clone_flags & CLONE_THREAD)
1366		p->tgid = current->tgid;
1367
1368	p->set_child_tid = (clone_flags & CLONE_CHILD_SETTID) ? child_tidptr : NULL;
1369	/*
1370	 * Clear TID on mm_release()?
1371	 */
1372	p->clear_child_tid = (clone_flags & CLONE_CHILD_CLEARTID) ? child_tidptr : NULL;
1373#ifdef CONFIG_BLOCK
1374	p->plug = NULL;
1375#endif
1376#ifdef CONFIG_FUTEX
1377	p->robust_list = NULL;
1378#ifdef CONFIG_COMPAT
1379	p->compat_robust_list = NULL;
1380#endif
1381	INIT_LIST_HEAD(&p->pi_state_list);
1382	p->pi_state_cache = NULL;
1383#endif
1384	uprobe_copy_process(p);
1385	/*
1386	 * sigaltstack should be cleared when sharing the same VM
1387	 */
1388	if ((clone_flags & (CLONE_VM|CLONE_VFORK)) == CLONE_VM)
1389		p->sas_ss_sp = p->sas_ss_size = 0;
1390
1391	/*
1392	 * Syscall tracing and stepping should be turned off in the
1393	 * child regardless of CLONE_PTRACE.
1394	 */
1395	user_disable_single_step(p);
1396	clear_tsk_thread_flag(p, TIF_SYSCALL_TRACE);
1397#ifdef TIF_SYSCALL_EMU
1398	clear_tsk_thread_flag(p, TIF_SYSCALL_EMU);
1399#endif
1400	clear_all_latency_tracing(p);
1401
1402	/* ok, now we should be set up.. */
1403	if (clone_flags & CLONE_THREAD)
1404		p->exit_signal = -1;
1405	else if (clone_flags & CLONE_PARENT)
1406		p->exit_signal = current->group_leader->exit_signal;
1407	else
1408		p->exit_signal = (clone_flags & CSIGNAL);
1409
1410	p->pdeath_signal = 0;
1411	p->exit_state = 0;
1412
1413	p->nr_dirtied = 0;
1414	p->nr_dirtied_pause = 128 >> (PAGE_SHIFT - 10);
1415	p->dirty_paused_when = 0;
1416
1417	/*
1418	 * Ok, make it visible to the rest of the system.
1419	 * We dont wake it up yet.
1420	 */
1421	p->group_leader = p;
1422	INIT_LIST_HEAD(&p->thread_group);
1423	INIT_HLIST_HEAD(&p->task_works);
1424
1425	/* Now that the task is set up, run cgroup callbacks if
1426	 * necessary. We need to run them before the task is visible
1427	 * on the tasklist. */
1428	cgroup_fork_callbacks(p);
1429	cgroup_callbacks_done = 1;
1430
1431	/* Need tasklist lock for parent etc handling! */
1432	write_lock_irq(&tasklist_lock);
1433
1434	/* CLONE_PARENT re-uses the old parent */
1435	if (clone_flags & (CLONE_PARENT|CLONE_THREAD)) {
1436		p->real_parent = current->real_parent;
1437		p->parent_exec_id = current->parent_exec_id;
1438	} else {
1439		p->real_parent = current;
1440		p->parent_exec_id = current->self_exec_id;
1441	}
1442
1443	spin_lock(&current->sighand->siglock);
1444
1445	/*
1446	 * Process group and session signals need to be delivered to just the
1447	 * parent before the fork or both the parent and the child after the
1448	 * fork. Restart if a signal comes in before we add the new process to
1449	 * it's process group.
1450	 * A fatal signal pending means that current will exit, so the new
1451	 * thread can't slip out of an OOM kill (or normal SIGKILL).
1452	*/
1453	recalc_sigpending();
1454	if (signal_pending(current)) {
1455		spin_unlock(&current->sighand->siglock);
1456		write_unlock_irq(&tasklist_lock);
1457		retval = -ERESTARTNOINTR;
1458		goto bad_fork_free_pid;
1459	}
1460
1461	if (clone_flags & CLONE_THREAD) {
1462		current->signal->nr_threads++;
1463		atomic_inc(&current->signal->live);
1464		atomic_inc(&current->signal->sigcnt);
1465		p->group_leader = current->group_leader;
1466		list_add_tail_rcu(&p->thread_group, &p->group_leader->thread_group);
1467	}
1468
1469	if (likely(p->pid)) {
1470		ptrace_init_task(p, (clone_flags & CLONE_PTRACE) || trace);
1471
1472		if (thread_group_leader(p)) {
1473			if (is_child_reaper(pid))
1474				p->nsproxy->pid_ns->child_reaper = p;
1475
1476			p->signal->leader_pid = pid;
1477			p->signal->tty = tty_kref_get(current->signal->tty);
1478			attach_pid(p, PIDTYPE_PGID, task_pgrp(current));
1479			attach_pid(p, PIDTYPE_SID, task_session(current));
1480			list_add_tail(&p->sibling, &p->real_parent->children);
1481			list_add_tail_rcu(&p->tasks, &init_task.tasks);
1482			__this_cpu_inc(process_counts);
1483		}
1484		attach_pid(p, PIDTYPE_PID, pid);
1485		nr_threads++;
1486	}
1487
1488	total_forks++;
1489	spin_unlock(&current->sighand->siglock);
1490	write_unlock_irq(&tasklist_lock);
1491	proc_fork_connector(p);
1492	cgroup_post_fork(p);
1493	if (clone_flags & CLONE_THREAD)
1494		threadgroup_change_end(current);
1495	perf_event_fork(p);
1496
1497	trace_task_newtask(p, clone_flags);
1498
1499	return p;
1500
1501bad_fork_free_pid:
1502	if (pid != &init_struct_pid)
1503		free_pid(pid);
1504bad_fork_cleanup_io:
1505	if (p->io_context)
1506		exit_io_context(p);
1507bad_fork_cleanup_namespaces:
1508	if (unlikely(clone_flags & CLONE_NEWPID))
1509		pid_ns_release_proc(p->nsproxy->pid_ns);
1510	exit_task_namespaces(p);
1511bad_fork_cleanup_mm:
1512	if (p->mm)
 
 
 
 
1513		mmput(p->mm);
 
1514bad_fork_cleanup_signal:
1515	if (!(clone_flags & CLONE_THREAD))
1516		free_signal_struct(p->signal);
1517bad_fork_cleanup_sighand:
1518	__cleanup_sighand(p->sighand);
1519bad_fork_cleanup_fs:
1520	exit_fs(p); /* blocking */
1521bad_fork_cleanup_files:
1522	exit_files(p); /* blocking */
1523bad_fork_cleanup_semundo:
1524	exit_sem(p);
1525bad_fork_cleanup_audit:
1526	audit_free(p);
1527bad_fork_cleanup_policy:
1528	perf_event_free_task(p);
1529#ifdef CONFIG_NUMA
1530	mpol_put(p->mempolicy);
1531bad_fork_cleanup_cgroup:
1532#endif
1533	if (clone_flags & CLONE_THREAD)
1534		threadgroup_change_end(current);
1535	cgroup_exit(p, cgroup_callbacks_done);
1536	delayacct_tsk_free(p);
1537	module_put(task_thread_info(p)->exec_domain->module);
1538bad_fork_cleanup_count:
1539	atomic_dec(&p->cred->user->processes);
1540	exit_creds(p);
1541bad_fork_free:
1542	free_task(p);
1543fork_out:
1544	return ERR_PTR(retval);
1545}
1546
1547noinline struct pt_regs * __cpuinit __attribute__((weak)) idle_regs(struct pt_regs *regs)
1548{
1549	memset(regs, 0, sizeof(struct pt_regs));
1550	return regs;
1551}
1552
1553static inline void init_idle_pids(struct pid_link *links)
1554{
1555	enum pid_type type;
1556
1557	for (type = PIDTYPE_PID; type < PIDTYPE_MAX; ++type) {
1558		INIT_HLIST_NODE(&links[type].node); /* not really needed */
1559		links[type].pid = &init_struct_pid;
1560	}
1561}
1562
1563struct task_struct * __cpuinit fork_idle(int cpu)
1564{
1565	struct task_struct *task;
1566	struct pt_regs regs;
1567
1568	task = copy_process(CLONE_VM, 0, idle_regs(&regs), 0, NULL,
1569			    &init_struct_pid, 0);
1570	if (!IS_ERR(task)) {
1571		init_idle_pids(task->pids);
1572		init_idle(task, cpu);
1573	}
1574
1575	return task;
1576}
1577
1578/*
1579 *  Ok, this is the main fork-routine.
1580 *
1581 * It copies the process, and if successful kick-starts
1582 * it and waits for it to finish using the VM if required.
1583 */
1584long do_fork(unsigned long clone_flags,
1585	      unsigned long stack_start,
1586	      struct pt_regs *regs,
1587	      unsigned long stack_size,
1588	      int __user *parent_tidptr,
1589	      int __user *child_tidptr)
1590{
1591	struct task_struct *p;
1592	int trace = 0;
1593	long nr;
1594
1595	/*
1596	 * Do some preliminary argument and permissions checking before we
1597	 * actually start allocating stuff
1598	 */
1599	if (clone_flags & CLONE_NEWUSER) {
1600		if (clone_flags & CLONE_THREAD)
1601			return -EINVAL;
1602		/* hopefully this check will go away when userns support is
1603		 * complete
1604		 */
1605		if (!capable(CAP_SYS_ADMIN) || !capable(CAP_SETUID) ||
1606				!capable(CAP_SETGID))
1607			return -EPERM;
1608	}
1609
1610	/*
1611	 * Determine whether and which event to report to ptracer.  When
1612	 * called from kernel_thread or CLONE_UNTRACED is explicitly
1613	 * requested, no event is reported; otherwise, report if the event
1614	 * for the type of forking is enabled.
1615	 */
1616	if (likely(user_mode(regs)) && !(clone_flags & CLONE_UNTRACED)) {
1617		if (clone_flags & CLONE_VFORK)
1618			trace = PTRACE_EVENT_VFORK;
1619		else if ((clone_flags & CSIGNAL) != SIGCHLD)
1620			trace = PTRACE_EVENT_CLONE;
1621		else
1622			trace = PTRACE_EVENT_FORK;
1623
1624		if (likely(!ptrace_event_enabled(current, trace)))
1625			trace = 0;
1626	}
1627
1628	p = copy_process(clone_flags, stack_start, regs, stack_size,
1629			 child_tidptr, NULL, trace);
1630	/*
1631	 * Do this prior waking up the new thread - the thread pointer
1632	 * might get invalid after that point, if the thread exits quickly.
1633	 */
1634	if (!IS_ERR(p)) {
1635		struct completion vfork;
1636
1637		trace_sched_process_fork(current, p);
1638
1639		nr = task_pid_vnr(p);
1640
1641		if (clone_flags & CLONE_PARENT_SETTID)
1642			put_user(nr, parent_tidptr);
1643
1644		if (clone_flags & CLONE_VFORK) {
1645			p->vfork_done = &vfork;
1646			init_completion(&vfork);
1647			get_task_struct(p);
1648		}
1649
 
 
 
 
 
 
 
 
 
 
1650		wake_up_new_task(p);
1651
1652		/* forking complete and child started to run, tell ptracer */
1653		if (unlikely(trace))
1654			ptrace_event(trace, nr);
1655
1656		if (clone_flags & CLONE_VFORK) {
1657			if (!wait_for_vfork_done(p, &vfork))
1658				ptrace_event(PTRACE_EVENT_VFORK_DONE, nr);
 
 
1659		}
1660	} else {
1661		nr = PTR_ERR(p);
1662	}
1663	return nr;
1664}
1665
1666#ifndef ARCH_MIN_MMSTRUCT_ALIGN
1667#define ARCH_MIN_MMSTRUCT_ALIGN 0
1668#endif
1669
1670static void sighand_ctor(void *data)
1671{
1672	struct sighand_struct *sighand = data;
1673
1674	spin_lock_init(&sighand->siglock);
1675	init_waitqueue_head(&sighand->signalfd_wqh);
1676}
1677
1678void __init proc_caches_init(void)
1679{
1680	sighand_cachep = kmem_cache_create("sighand_cache",
1681			sizeof(struct sighand_struct), 0,
1682			SLAB_HWCACHE_ALIGN|SLAB_PANIC|SLAB_DESTROY_BY_RCU|
1683			SLAB_NOTRACK, sighand_ctor);
1684	signal_cachep = kmem_cache_create("signal_cache",
1685			sizeof(struct signal_struct), 0,
1686			SLAB_HWCACHE_ALIGN|SLAB_PANIC|SLAB_NOTRACK, NULL);
1687	files_cachep = kmem_cache_create("files_cache",
1688			sizeof(struct files_struct), 0,
1689			SLAB_HWCACHE_ALIGN|SLAB_PANIC|SLAB_NOTRACK, NULL);
1690	fs_cachep = kmem_cache_create("fs_cache",
1691			sizeof(struct fs_struct), 0,
1692			SLAB_HWCACHE_ALIGN|SLAB_PANIC|SLAB_NOTRACK, NULL);
1693	/*
1694	 * FIXME! The "sizeof(struct mm_struct)" currently includes the
1695	 * whole struct cpumask for the OFFSTACK case. We could change
1696	 * this to *only* allocate as much of it as required by the
1697	 * maximum number of CPU's we can ever have.  The cpumask_allocation
1698	 * is at the end of the structure, exactly for that reason.
1699	 */
1700	mm_cachep = kmem_cache_create("mm_struct",
1701			sizeof(struct mm_struct), ARCH_MIN_MMSTRUCT_ALIGN,
1702			SLAB_HWCACHE_ALIGN|SLAB_PANIC|SLAB_NOTRACK, NULL);
1703	vm_area_cachep = KMEM_CACHE(vm_area_struct, SLAB_PANIC);
1704	mmap_init();
1705	nsproxy_cache_init();
1706}
1707
1708/*
1709 * Check constraints on flags passed to the unshare system call.
1710 */
1711static int check_unshare_flags(unsigned long unshare_flags)
1712{
1713	if (unshare_flags & ~(CLONE_THREAD|CLONE_FS|CLONE_NEWNS|CLONE_SIGHAND|
1714				CLONE_VM|CLONE_FILES|CLONE_SYSVSEM|
1715				CLONE_NEWUTS|CLONE_NEWIPC|CLONE_NEWNET))
1716		return -EINVAL;
1717	/*
1718	 * Not implemented, but pretend it works if there is nothing to
1719	 * unshare. Note that unsharing CLONE_THREAD or CLONE_SIGHAND
1720	 * needs to unshare vm.
1721	 */
1722	if (unshare_flags & (CLONE_THREAD | CLONE_SIGHAND | CLONE_VM)) {
1723		/* FIXME: get_task_mm() increments ->mm_users */
1724		if (atomic_read(&current->mm->mm_users) > 1)
1725			return -EINVAL;
1726	}
1727
1728	return 0;
1729}
1730
1731/*
1732 * Unshare the filesystem structure if it is being shared
1733 */
1734static int unshare_fs(unsigned long unshare_flags, struct fs_struct **new_fsp)
1735{
1736	struct fs_struct *fs = current->fs;
1737
1738	if (!(unshare_flags & CLONE_FS) || !fs)
1739		return 0;
1740
1741	/* don't need lock here; in the worst case we'll do useless copy */
1742	if (fs->users == 1)
1743		return 0;
1744
1745	*new_fsp = copy_fs_struct(fs);
1746	if (!*new_fsp)
1747		return -ENOMEM;
1748
1749	return 0;
1750}
1751
1752/*
1753 * Unshare file descriptor table if it is being shared
1754 */
1755static int unshare_fd(unsigned long unshare_flags, struct files_struct **new_fdp)
1756{
1757	struct files_struct *fd = current->files;
1758	int error = 0;
1759
1760	if ((unshare_flags & CLONE_FILES) &&
1761	    (fd && atomic_read(&fd->count) > 1)) {
1762		*new_fdp = dup_fd(fd, &error);
1763		if (!*new_fdp)
1764			return error;
1765	}
1766
1767	return 0;
1768}
1769
1770/*
1771 * unshare allows a process to 'unshare' part of the process
1772 * context which was originally shared using clone.  copy_*
1773 * functions used by do_fork() cannot be used here directly
1774 * because they modify an inactive task_struct that is being
1775 * constructed. Here we are modifying the current, active,
1776 * task_struct.
1777 */
1778SYSCALL_DEFINE1(unshare, unsigned long, unshare_flags)
1779{
1780	struct fs_struct *fs, *new_fs = NULL;
1781	struct files_struct *fd, *new_fd = NULL;
1782	struct nsproxy *new_nsproxy = NULL;
1783	int do_sysvsem = 0;
1784	int err;
1785
1786	err = check_unshare_flags(unshare_flags);
1787	if (err)
1788		goto bad_unshare_out;
1789
1790	/*
1791	 * If unsharing namespace, must also unshare filesystem information.
1792	 */
1793	if (unshare_flags & CLONE_NEWNS)
1794		unshare_flags |= CLONE_FS;
1795	/*
1796	 * CLONE_NEWIPC must also detach from the undolist: after switching
1797	 * to a new ipc namespace, the semaphore arrays from the old
1798	 * namespace are unreachable.
1799	 */
1800	if (unshare_flags & (CLONE_NEWIPC|CLONE_SYSVSEM))
1801		do_sysvsem = 1;
1802	err = unshare_fs(unshare_flags, &new_fs);
1803	if (err)
1804		goto bad_unshare_out;
1805	err = unshare_fd(unshare_flags, &new_fd);
1806	if (err)
1807		goto bad_unshare_cleanup_fs;
1808	err = unshare_nsproxy_namespaces(unshare_flags, &new_nsproxy, new_fs);
1809	if (err)
1810		goto bad_unshare_cleanup_fd;
1811
1812	if (new_fs || new_fd || do_sysvsem || new_nsproxy) {
1813		if (do_sysvsem) {
1814			/*
1815			 * CLONE_SYSVSEM is equivalent to sys_exit().
1816			 */
1817			exit_sem(current);
1818		}
1819
1820		if (new_nsproxy) {
1821			switch_task_namespaces(current, new_nsproxy);
1822			new_nsproxy = NULL;
1823		}
1824
1825		task_lock(current);
1826
1827		if (new_fs) {
1828			fs = current->fs;
1829			spin_lock(&fs->lock);
1830			current->fs = new_fs;
1831			if (--fs->users)
1832				new_fs = NULL;
1833			else
1834				new_fs = fs;
1835			spin_unlock(&fs->lock);
1836		}
1837
1838		if (new_fd) {
1839			fd = current->files;
1840			current->files = new_fd;
1841			new_fd = fd;
1842		}
1843
1844		task_unlock(current);
1845	}
1846
1847	if (new_nsproxy)
1848		put_nsproxy(new_nsproxy);
1849
1850bad_unshare_cleanup_fd:
1851	if (new_fd)
1852		put_files_struct(new_fd);
1853
1854bad_unshare_cleanup_fs:
1855	if (new_fs)
1856		free_fs_struct(new_fs);
1857
1858bad_unshare_out:
1859	return err;
1860}
1861
1862/*
1863 *	Helper to unshare the files of the current task.
1864 *	We don't want to expose copy_files internals to
1865 *	the exec layer of the kernel.
1866 */
1867
1868int unshare_files(struct files_struct **displaced)
1869{
1870	struct task_struct *task = current;
1871	struct files_struct *copy = NULL;
1872	int error;
1873
1874	error = unshare_fd(CLONE_FILES, &copy);
1875	if (error || !copy) {
1876		*displaced = NULL;
1877		return error;
1878	}
1879	*displaced = task->files;
1880	task_lock(task);
1881	task->files = copy;
1882	task_unlock(task);
1883	return 0;
1884}