fork.c 40.6 KB
Newer Older
Linus Torvalds's avatar
Linus Torvalds committed
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19
/*
 *  linux/kernel/fork.c
 *
 *  Copyright (C) 1991, 1992  Linus Torvalds
 */

/*
 *  'fork.c' contains the help-routines for the 'fork' system call
 * (see also entry.S and others).
 * Fork is rather simple, once you get the hang of it, but the memory
 * management can be a bitch. See 'mm/memory.c': 'copy_page_range()'
 */

#include <linux/slab.h>
#include <linux/init.h>
#include <linux/unistd.h>
#include <linux/module.h>
#include <linux/vmalloc.h>
#include <linux/completion.h>
20
#include <linux/mnt_namespace.h>
Linus Torvalds's avatar
Linus Torvalds committed
21 22 23 24 25 26 27 28
#include <linux/personality.h>
#include <linux/mempolicy.h>
#include <linux/sem.h>
#include <linux/file.h>
#include <linux/key.h>
#include <linux/binfmts.h>
#include <linux/mman.h>
#include <linux/fs.h>
29
#include <linux/nsproxy.h>
30
#include <linux/capability.h>
Linus Torvalds's avatar
Linus Torvalds committed
31 32 33 34 35 36 37
#include <linux/cpu.h>
#include <linux/cpuset.h>
#include <linux/security.h>
#include <linux/swap.h>
#include <linux/syscalls.h>
#include <linux/jiffies.h>
#include <linux/futex.h>
38
#include <linux/task_io_accounting_ops.h>
39
#include <linux/rcupdate.h>
Linus Torvalds's avatar
Linus Torvalds committed
40 41 42 43 44 45
#include <linux/ptrace.h>
#include <linux/mount.h>
#include <linux/audit.h>
#include <linux/profile.h>
#include <linux/rmap.h>
#include <linux/acct.h>
46
#include <linux/tsacct_kern.h>
47
#include <linux/cn_proc.h>
48
#include <linux/delayacct.h>
49
#include <linux/taskstats_kern.h>
50
#include <linux/random.h>
Linus Torvalds's avatar
Linus Torvalds committed
51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68

#include <asm/pgtable.h>
#include <asm/pgalloc.h>
#include <asm/uaccess.h>
#include <asm/mmu_context.h>
#include <asm/cacheflush.h>
#include <asm/tlbflush.h>

/*
 * Protected counters by write_lock_irq(&tasklist_lock)
 */
unsigned long total_forks;	/* Handle normal Linux uptimes. */
int nr_threads; 		/* The idle threads do not count.. */

int max_threads;		/* tunable limit on nr_threads */

DEFINE_PER_CPU(unsigned long, process_counts) = 0;

69
__cacheline_aligned DEFINE_RWLOCK(tasklist_lock);  /* outer */
Linus Torvalds's avatar
Linus Torvalds committed
70 71 72 73 74 75 76 77 78 79 80 81 82 83 84

int nr_processes(void)
{
	int cpu;
	int total = 0;

	for_each_online_cpu(cpu)
		total += per_cpu(process_counts, cpu);

	return total;
}

#ifndef __HAVE_ARCH_TASK_STRUCT_ALLOCATOR
# define alloc_task_struct()	kmem_cache_alloc(task_struct_cachep, GFP_KERNEL)
# define free_task_struct(tsk)	kmem_cache_free(task_struct_cachep, (tsk))
85
static struct kmem_cache *task_struct_cachep;
Linus Torvalds's avatar
Linus Torvalds committed
86 87 88
#endif

/* SLAB cache for signal_struct structures (tsk->signal) */
89
static struct kmem_cache *signal_cachep;
Linus Torvalds's avatar
Linus Torvalds committed
90 91

/* SLAB cache for sighand_struct structures (tsk->sighand) */
92
struct kmem_cache *sighand_cachep;
Linus Torvalds's avatar
Linus Torvalds committed
93 94

/* SLAB cache for files_struct structures (tsk->files) */
95
struct kmem_cache *files_cachep;
Linus Torvalds's avatar
Linus Torvalds committed
96 97

/* SLAB cache for fs_struct structures (tsk->fs) */
98
struct kmem_cache *fs_cachep;
Linus Torvalds's avatar
Linus Torvalds committed
99 100

/* SLAB cache for vm_area_struct structures */
101
struct kmem_cache *vm_area_cachep;
Linus Torvalds's avatar
Linus Torvalds committed
102 103

/* SLAB cache for mm_struct structures (tsk->mm) */
104
static struct kmem_cache *mm_cachep;
Linus Torvalds's avatar
Linus Torvalds committed
105 106 107 108

void free_task(struct task_struct *tsk)
{
	free_thread_info(tsk->thread_info);
109
	rt_mutex_debug_task_free(tsk);
Linus Torvalds's avatar
Linus Torvalds committed
110 111 112 113
	free_task_struct(tsk);
}
EXPORT_SYMBOL(free_task);

114
void __put_task_struct(struct task_struct *tsk)
Linus Torvalds's avatar
Linus Torvalds committed
115 116 117 118 119 120 121 122
{
	WARN_ON(!(tsk->exit_state & (EXIT_DEAD | EXIT_ZOMBIE)));
	WARN_ON(atomic_read(&tsk->usage));
	WARN_ON(tsk == current);

	security_task_free(tsk);
	free_uid(tsk->user);
	put_group_info(tsk->group_info);
123
	delayacct_tsk_free(tsk);
Linus Torvalds's avatar
Linus Torvalds committed
124 125 126 127 128 129 130 131 132 133 134 135 136 137 138 139 140 141 142 143 144 145 146 147 148 149 150 151 152 153 154 155 156 157 158 159 160 161 162 163 164 165 166 167 168 169 170 171 172 173 174 175 176 177 178

	if (!profile_handoff_task(tsk))
		free_task(tsk);
}

void __init fork_init(unsigned long mempages)
{
#ifndef __HAVE_ARCH_TASK_STRUCT_ALLOCATOR
#ifndef ARCH_MIN_TASKALIGN
#define ARCH_MIN_TASKALIGN	L1_CACHE_BYTES
#endif
	/* create a slab on which task_structs can be allocated */
	task_struct_cachep =
		kmem_cache_create("task_struct", sizeof(struct task_struct),
			ARCH_MIN_TASKALIGN, SLAB_PANIC, NULL, NULL);
#endif

	/*
	 * The default maximum number of threads is set to a safe
	 * value: the thread structures can take up at most half
	 * of memory.
	 */
	max_threads = mempages / (8 * THREAD_SIZE / PAGE_SIZE);

	/*
	 * we need to allow at least 20 threads to boot a system
	 */
	if(max_threads < 20)
		max_threads = 20;

	init_task.signal->rlim[RLIMIT_NPROC].rlim_cur = max_threads/2;
	init_task.signal->rlim[RLIMIT_NPROC].rlim_max = max_threads/2;
	init_task.signal->rlim[RLIMIT_SIGPENDING] =
		init_task.signal->rlim[RLIMIT_NPROC];
}

static struct task_struct *dup_task_struct(struct task_struct *orig)
{
	struct task_struct *tsk;
	struct thread_info *ti;

	prepare_to_copy(orig);

	tsk = alloc_task_struct();
	if (!tsk)
		return NULL;

	ti = alloc_thread_info(tsk);
	if (!ti) {
		free_task_struct(tsk);
		return NULL;
	}

	*tsk = *orig;
	tsk->thread_info = ti;
179
	setup_thread_stack(tsk, orig);
Linus Torvalds's avatar
Linus Torvalds committed
180

181 182 183 184
#ifdef CONFIG_CC_STACKPROTECTOR
	tsk->stack_canary = get_random_int();
#endif

Linus Torvalds's avatar
Linus Torvalds committed
185 186
	/* One for us, one for whoever does the "release_task()" (usually parent) */
	atomic_set(&tsk->usage,2);
187
	atomic_set(&tsk->fs_excl, 0);
188
#ifdef CONFIG_BLK_DEV_IO_TRACE
189
	tsk->btrace_seq = 0;
190
#endif
191
	tsk->splice_pipe = NULL;
Linus Torvalds's avatar
Linus Torvalds committed
192 193 194 195
	return tsk;
}

#ifdef CONFIG_MMU
196
static inline int dup_mmap(struct mm_struct *mm, struct mm_struct *oldmm)
Linus Torvalds's avatar
Linus Torvalds committed
197
{
198
	struct vm_area_struct *mpnt, *tmp, **pprev;
Linus Torvalds's avatar
Linus Torvalds committed
199 200 201 202 203 204
	struct rb_node **rb_link, *rb_parent;
	int retval;
	unsigned long charge;
	struct mempolicy *pol;

	down_write(&oldmm->mmap_sem);
205
	flush_cache_dup_mm(oldmm);
206 207 208 209
	/*
	 * Not linked in yet - no deadlock potential:
	 */
	down_write_nested(&mm->mmap_sem, SINGLE_DEPTH_NESTING);
210

Linus Torvalds's avatar
Linus Torvalds committed
211 212 213 214
	mm->locked_vm = 0;
	mm->mmap = NULL;
	mm->mmap_cache = NULL;
	mm->free_area_cache = oldmm->mmap_base;
215
	mm->cached_hole_size = ~0UL;
Linus Torvalds's avatar
Linus Torvalds committed
216 217 218 219 220 221 222
	mm->map_count = 0;
	cpus_clear(mm->cpu_vm_mask);
	mm->mm_rb = RB_ROOT;
	rb_link = &mm->mm_rb.rb_node;
	rb_parent = NULL;
	pprev = &mm->mmap;

223
	for (mpnt = oldmm->mmap; mpnt; mpnt = mpnt->vm_next) {
Linus Torvalds's avatar
Linus Torvalds committed
224 225 226
		struct file *file;

		if (mpnt->vm_flags & VM_DONTCOPY) {
227 228
			long pages = vma_pages(mpnt);
			mm->total_vm -= pages;
229
			vm_stat_account(mm, mpnt->vm_flags, mpnt->vm_file,
230
								-pages);
Linus Torvalds's avatar
Linus Torvalds committed
231 232 233 234 235 236 237 238 239
			continue;
		}
		charge = 0;
		if (mpnt->vm_flags & VM_ACCOUNT) {
			unsigned int len = (mpnt->vm_end - mpnt->vm_start) >> PAGE_SHIFT;
			if (security_vm_enough_memory(len))
				goto fail_nomem;
			charge = len;
		}
240
		tmp = kmem_cache_alloc(vm_area_cachep, GFP_KERNEL);
Linus Torvalds's avatar
Linus Torvalds committed
241 242 243 244 245 246 247 248 249 250 251 252 253 254
		if (!tmp)
			goto fail_nomem;
		*tmp = *mpnt;
		pol = mpol_copy(vma_policy(mpnt));
		retval = PTR_ERR(pol);
		if (IS_ERR(pol))
			goto fail_nomem_policy;
		vma_set_policy(tmp, pol);
		tmp->vm_flags &= ~VM_LOCKED;
		tmp->vm_mm = mm;
		tmp->vm_next = NULL;
		anon_vma_link(tmp);
		file = tmp->vm_file;
		if (file) {
255
			struct inode *inode = file->f_path.dentry->d_inode;
Linus Torvalds's avatar
Linus Torvalds committed
256 257 258 259 260 261 262 263 264 265 266 267 268 269
			get_file(file);
			if (tmp->vm_flags & VM_DENYWRITE)
				atomic_dec(&inode->i_writecount);
      
			/* insert tmp into the share list, just after mpnt */
			spin_lock(&file->f_mapping->i_mmap_lock);
			tmp->vm_truncate_count = mpnt->vm_truncate_count;
			flush_dcache_mmap_lock(file->f_mapping);
			vma_prio_tree_add(tmp, mpnt);
			flush_dcache_mmap_unlock(file->f_mapping);
			spin_unlock(&file->f_mapping->i_mmap_lock);
		}

		/*
270
		 * Link in the new vma and copy the page table entries.
Linus Torvalds's avatar
Linus Torvalds committed
271 272 273 274 275 276 277 278 279
		 */
		*pprev = tmp;
		pprev = &tmp->vm_next;

		__vma_link_rb(mm, tmp, rb_link, rb_parent);
		rb_link = &tmp->vm_rb.rb_right;
		rb_parent = &tmp->vm_rb;

		mm->map_count++;
280
		retval = copy_page_range(mm, oldmm, mpnt);
Linus Torvalds's avatar
Linus Torvalds committed
281 282 283 284 285 286 287

		if (tmp->vm_ops && tmp->vm_ops->open)
			tmp->vm_ops->open(tmp);

		if (retval)
			goto out;
	}
288 289
	/* a new mm has just been created */
	arch_dup_mmap(oldmm, mm);
Linus Torvalds's avatar
Linus Torvalds committed
290 291
	retval = 0;
out:
292
	up_write(&mm->mmap_sem);
293
	flush_tlb_mm(oldmm);
Linus Torvalds's avatar
Linus Torvalds committed
294 295 296 297 298 299 300 301 302 303 304 305 306 307 308 309 310 311 312 313 314 315 316 317 318 319 320 321 322 323
	up_write(&oldmm->mmap_sem);
	return retval;
fail_nomem_policy:
	kmem_cache_free(vm_area_cachep, tmp);
fail_nomem:
	retval = -ENOMEM;
	vm_unacct_memory(charge);
	goto out;
}

static inline int mm_alloc_pgd(struct mm_struct * mm)
{
	mm->pgd = pgd_alloc(mm);
	if (unlikely(!mm->pgd))
		return -ENOMEM;
	return 0;
}

static inline void mm_free_pgd(struct mm_struct * mm)
{
	pgd_free(mm->pgd);
}
#else
#define dup_mmap(mm, oldmm)	(0)
#define mm_alloc_pgd(mm)	(0)
#define mm_free_pgd(mm)
#endif /* CONFIG_MMU */

 __cacheline_aligned_in_smp DEFINE_SPINLOCK(mmlist_lock);

324
#define allocate_mm()	(kmem_cache_alloc(mm_cachep, GFP_KERNEL))
Linus Torvalds's avatar
Linus Torvalds committed
325 326 327 328 329 330 331 332 333 334 335 336
#define free_mm(mm)	(kmem_cache_free(mm_cachep, (mm)))

#include <linux/init_task.h>

static struct mm_struct * mm_init(struct mm_struct * mm)
{
	atomic_set(&mm->mm_users, 1);
	atomic_set(&mm->mm_count, 1);
	init_rwsem(&mm->mmap_sem);
	INIT_LIST_HEAD(&mm->mmlist);
	mm->core_waiters = 0;
	mm->nr_ptes = 0;
337
	set_mm_counter(mm, file_rss, 0);
338
	set_mm_counter(mm, anon_rss, 0);
Linus Torvalds's avatar
Linus Torvalds committed
339 340 341 342
	spin_lock_init(&mm->page_table_lock);
	rwlock_init(&mm->ioctx_list_lock);
	mm->ioctx_list = NULL;
	mm->free_area_cache = TASK_UNMAPPED_BASE;
343
	mm->cached_hole_size = ~0UL;
Linus Torvalds's avatar
Linus Torvalds committed
344 345 346 347 348 349 350 351 352 353 354 355 356 357 358 359 360 361 362 363 364 365 366 367 368 369 370 371 372 373 374 375 376 377 378 379 380 381 382 383 384 385

	if (likely(!mm_alloc_pgd(mm))) {
		mm->def_flags = 0;
		return mm;
	}
	free_mm(mm);
	return NULL;
}

/*
 * Allocate and initialize an mm_struct.
 */
struct mm_struct * mm_alloc(void)
{
	struct mm_struct * mm;

	mm = allocate_mm();
	if (mm) {
		memset(mm, 0, sizeof(*mm));
		mm = mm_init(mm);
	}
	return mm;
}

/*
 * Called when the last reference to the mm
 * is dropped: either by a lazy thread or by
 * mmput. Free the page directory and the mm.
 */
void fastcall __mmdrop(struct mm_struct *mm)
{
	BUG_ON(mm == &init_mm);
	mm_free_pgd(mm);
	destroy_context(mm);
	free_mm(mm);
}

/*
 * Decrement the use count and release all resources for an mm.
 */
void mmput(struct mm_struct *mm)
{
Andrew Morton's avatar
Andrew Morton committed
386 387
	might_sleep();

Linus Torvalds's avatar
Linus Torvalds committed
388 389 390 391 392 393 394 395 396 397 398 399 400 401 402 403 404 405 406 407 408 409 410 411 412 413 414 415 416 417 418 419 420 421 422 423 424 425 426 427 428 429 430 431 432 433 434 435 436 437 438 439 440 441 442 443 444 445 446 447 448 449 450 451 452
	if (atomic_dec_and_test(&mm->mm_users)) {
		exit_aio(mm);
		exit_mmap(mm);
		if (!list_empty(&mm->mmlist)) {
			spin_lock(&mmlist_lock);
			list_del(&mm->mmlist);
			spin_unlock(&mmlist_lock);
		}
		put_swap_token(mm);
		mmdrop(mm);
	}
}
EXPORT_SYMBOL_GPL(mmput);

/**
 * get_task_mm - acquire a reference to the task's mm
 *
 * Returns %NULL if the task has no mm.  Checks PF_BORROWED_MM (meaning
 * this kernel workthread has transiently adopted a user mm with use_mm,
 * to do its AIO) is not set and if so returns a reference to it, after
 * bumping up the use count.  User must release the mm via mmput()
 * after use.  Typically used by /proc and ptrace.
 */
struct mm_struct *get_task_mm(struct task_struct *task)
{
	struct mm_struct *mm;

	task_lock(task);
	mm = task->mm;
	if (mm) {
		if (task->flags & PF_BORROWED_MM)
			mm = NULL;
		else
			atomic_inc(&mm->mm_users);
	}
	task_unlock(task);
	return mm;
}
EXPORT_SYMBOL_GPL(get_task_mm);

/* Please note the differences between mmput and mm_release.
 * mmput is called whenever we stop holding onto a mm_struct,
 * error success whatever.
 *
 * mm_release is called after a mm_struct has been removed
 * from the current process.
 *
 * This difference is important for error handling, when we
 * only half set up a mm_struct for a new process and need to restore
 * the old one.  Because we mmput the new mm_struct before
 * restoring the old one. . .
 * Eric Biederman 10 January 1998
 */
void mm_release(struct task_struct *tsk, struct mm_struct *mm)
{
	struct completion *vfork_done = tsk->vfork_done;

	/* Get rid of any cached register state */
	deactivate_mm(tsk, mm);

	/* notify parent sleeping on vfork() */
	if (vfork_done) {
		tsk->vfork_done = NULL;
		complete(vfork_done);
	}
453 454 455 456 457 458 459 460 461 462

	/*
	 * If we're exiting normally, clear a user-space tid field if
	 * requested.  We leave this alone when dying by signal, to leave
	 * the value intact in a core dump, and to save the unnecessary
	 * trouble otherwise.  Userland only wants this done for a sys_exit.
	 */
	if (tsk->clear_child_tid
	    && !(tsk->flags & PF_SIGNALED)
	    && atomic_read(&mm->mm_users) > 1) {
Linus Torvalds's avatar
Linus Torvalds committed
463 464 465 466 467 468 469 470 471 472 473 474
		u32 __user * tidptr = tsk->clear_child_tid;
		tsk->clear_child_tid = NULL;

		/*
		 * We don't check the error code - if userspace has
		 * not set up a proper pointer then tough luck.
		 */
		put_user(0, tidptr);
		sys_futex(tidptr, FUTEX_WAKE, 1, NULL, NULL, 0);
	}
}

475 476 477 478 479 480 481 482 483 484 485 486 487 488 489 490 491 492
/*
 * Allocate a new mm structure and copy contents from the
 * mm structure of the passed in task structure.
 */
static struct mm_struct *dup_mm(struct task_struct *tsk)
{
	struct mm_struct *mm, *oldmm = current->mm;
	int err;

	if (!oldmm)
		return NULL;

	mm = allocate_mm();
	if (!mm)
		goto fail_nomem;

	memcpy(mm, oldmm, sizeof(*mm));

493 494 495 496
	/* Initializing for Swap token stuff */
	mm->token_priority = 0;
	mm->last_interval = 0;

497 498 499 500 501 502 503 504 505 506 507 508 509 510 511 512 513 514 515 516 517 518 519 520 521 522 523 524 525 526 527
	if (!mm_init(mm))
		goto fail_nomem;

	if (init_new_context(tsk, mm))
		goto fail_nocontext;

	err = dup_mmap(mm, oldmm);
	if (err)
		goto free_pt;

	mm->hiwater_rss = get_mm_rss(mm);
	mm->hiwater_vm = mm->total_vm;

	return mm;

free_pt:
	mmput(mm);

fail_nomem:
	return NULL;

fail_nocontext:
	/*
	 * If init_new_context() failed, we cannot use mmput() to free the mm
	 * because it calls destroy_context()
	 */
	mm_free_pgd(mm);
	free_mm(mm);
	return NULL;
}

Linus Torvalds's avatar
Linus Torvalds committed
528 529 530 531 532 533 534 535 536 537 538 539 540 541 542 543 544 545 546 547 548 549 550 551 552 553 554
static int copy_mm(unsigned long clone_flags, struct task_struct * tsk)
{
	struct mm_struct * mm, *oldmm;
	int retval;

	tsk->min_flt = tsk->maj_flt = 0;
	tsk->nvcsw = tsk->nivcsw = 0;

	tsk->mm = NULL;
	tsk->active_mm = NULL;

	/*
	 * Are we cloning a kernel thread?
	 *
	 * We need to steal a active VM for that..
	 */
	oldmm = current->mm;
	if (!oldmm)
		return 0;

	if (clone_flags & CLONE_VM) {
		atomic_inc(&oldmm->mm_users);
		mm = oldmm;
		goto good_mm;
	}

	retval = -ENOMEM;
555
	mm = dup_mm(tsk);
Linus Torvalds's avatar
Linus Torvalds committed
556 557 558 559
	if (!mm)
		goto fail_nomem;

good_mm:
560 561 562 563
	/* Initializing for Swap token stuff */
	mm->token_priority = 0;
	mm->last_interval = 0;

Linus Torvalds's avatar
Linus Torvalds committed
564 565 566 567 568 569 570 571 572 573 574 575 576 577 578 579 580 581 582 583 584 585 586 587 588 589 590 591 592 593 594 595 596 597 598 599 600 601 602 603 604 605 606 607 608 609 610 611 612 613 614 615
	tsk->mm = mm;
	tsk->active_mm = mm;
	return 0;

fail_nomem:
	return retval;
}

static inline struct fs_struct *__copy_fs_struct(struct fs_struct *old)
{
	struct fs_struct *fs = kmem_cache_alloc(fs_cachep, GFP_KERNEL);
	/* We don't need to lock fs - think why ;-) */
	if (fs) {
		atomic_set(&fs->count, 1);
		rwlock_init(&fs->lock);
		fs->umask = old->umask;
		read_lock(&old->lock);
		fs->rootmnt = mntget(old->rootmnt);
		fs->root = dget(old->root);
		fs->pwdmnt = mntget(old->pwdmnt);
		fs->pwd = dget(old->pwd);
		if (old->altroot) {
			fs->altrootmnt = mntget(old->altrootmnt);
			fs->altroot = dget(old->altroot);
		} else {
			fs->altrootmnt = NULL;
			fs->altroot = NULL;
		}
		read_unlock(&old->lock);
	}
	return fs;
}

struct fs_struct *copy_fs_struct(struct fs_struct *old)
{
	return __copy_fs_struct(old);
}

EXPORT_SYMBOL_GPL(copy_fs_struct);

static inline int copy_fs(unsigned long clone_flags, struct task_struct * tsk)
{
	if (clone_flags & CLONE_FS) {
		atomic_inc(&current->fs->count);
		return 0;
	}
	tsk->fs = __copy_fs_struct(current->fs);
	if (!tsk->fs)
		return -ENOMEM;
	return 0;
}

616
static int count_open_files(struct fdtable *fdt)
Linus Torvalds's avatar
Linus Torvalds committed
617
{
618
	int size = fdt->max_fds;
Linus Torvalds's avatar
Linus Torvalds committed
619 620 621 622
	int i;

	/* Find the last open fd */
	for (i = size/(8*sizeof(long)); i > 0; ) {
623
		if (fdt->open_fds->fds_bits[--i])
Linus Torvalds's avatar
Linus Torvalds committed
624 625 626 627 628 629
			break;
	}
	i = (i+1) * 8 * sizeof(long);
	return i;
}

630 631 632 633 634
static struct files_struct *alloc_files(void)
{
	struct files_struct *newf;
	struct fdtable *fdt;

635
	newf = kmem_cache_alloc(files_cachep, GFP_KERNEL);
636 637 638 639 640 641
	if (!newf)
		goto out;

	atomic_set(&newf->count, 1);

	spin_lock_init(&newf->file_lock);
642
	newf->next_fd = 0;
643
	fdt = &newf->fdtab;
644
	fdt->max_fds = NR_OPEN_DEFAULT;
645 646
	fdt->close_on_exec = (fd_set *)&newf->close_on_exec_init;
	fdt->open_fds = (fd_set *)&newf->open_fds_init;
647
	fdt->fd = &newf->fd_array[0];
648 649 650
	INIT_RCU_HEAD(&fdt->rcu);
	fdt->next = NULL;
	rcu_assign_pointer(newf->fdt, fdt);
651 652 653 654
out:
	return newf;
}

655 656 657
/*
 * Allocate a new files structure and copy contents from the
 * passed in files structure.
Prasanna Meda's avatar
Prasanna Meda committed
658
 * errorp will be valid only when the returned files_struct is NULL.
659 660
 */
static struct files_struct *dup_fd(struct files_struct *oldf, int *errorp)
Linus Torvalds's avatar
Linus Torvalds committed
661
{
662
	struct files_struct *newf;
Linus Torvalds's avatar
Linus Torvalds committed
663
	struct file **old_fds, **new_fds;
664
	int open_files, size, i;
665
	struct fdtable *old_fdt, *new_fdt;
Linus Torvalds's avatar
Linus Torvalds committed
666

Prasanna Meda's avatar
Prasanna Meda committed
667
	*errorp = -ENOMEM;
668 669
	newf = alloc_files();
	if (!newf)
Linus Torvalds's avatar
Linus Torvalds committed
670 671 672
		goto out;

	spin_lock(&oldf->file_lock);
673 674
	old_fdt = files_fdtable(oldf);
	new_fdt = files_fdtable(newf);
675
	open_files = count_open_files(old_fdt);
Linus Torvalds's avatar
Linus Torvalds committed
676 677

	/*
678 679
	 * Check whether we need to allocate a larger fd array and fd set.
	 * Note: we're not a clone task, so the open count won't change.
Linus Torvalds's avatar
Linus Torvalds committed
680
	 */
681 682
	if (open_files > new_fdt->max_fds) {
		new_fdt->max_fds = 0;
Linus Torvalds's avatar
Linus Torvalds committed
683 684
		spin_unlock(&oldf->file_lock);
		spin_lock(&newf->file_lock);
685
		*errorp = expand_files(newf, open_files-1);
Linus Torvalds's avatar
Linus Torvalds committed
686
		spin_unlock(&newf->file_lock);
687
		if (*errorp < 0)
Linus Torvalds's avatar
Linus Torvalds committed
688
			goto out_release;
689 690 691 692 693 694
		new_fdt = files_fdtable(newf);
		/*
		 * Reacquire the oldf lock and a pointer to its fd table
		 * who knows it may have a new bigger fd table. We need
		 * the latest pointer.
		 */
Linus Torvalds's avatar
Linus Torvalds committed
695
		spin_lock(&oldf->file_lock);
696
		old_fdt = files_fdtable(oldf);
Linus Torvalds's avatar
Linus Torvalds committed
697 698
	}

699 700
	old_fds = old_fdt->fd;
	new_fds = new_fdt->fd;
Linus Torvalds's avatar
Linus Torvalds committed
701

702 703 704 705
	memcpy(new_fdt->open_fds->fds_bits,
		old_fdt->open_fds->fds_bits, open_files/8);
	memcpy(new_fdt->close_on_exec->fds_bits,
		old_fdt->close_on_exec->fds_bits, open_files/8);
Linus Torvalds's avatar
Linus Torvalds committed
706 707 708 709 710 711 712 713 714 715 716 717

	for (i = open_files; i != 0; i--) {
		struct file *f = *old_fds++;
		if (f) {
			get_file(f);
		} else {
			/*
			 * The fd may be claimed in the fd bitmap but not yet
			 * instantiated in the files array if a sibling thread
			 * is partway through open().  So make sure that this
			 * fd is available to the new process.
			 */
718
			FD_CLR(open_files - i, new_fdt->open_fds);
Linus Torvalds's avatar
Linus Torvalds committed
719
		}
720
		rcu_assign_pointer(*new_fds++, f);
Linus Torvalds's avatar
Linus Torvalds committed
721 722 723 724
	}
	spin_unlock(&oldf->file_lock);

	/* compute the remainder to be cleared */
725
	size = (new_fdt->max_fds - open_files) * sizeof(struct file *);
Linus Torvalds's avatar
Linus Torvalds committed
726 727 728 729

	/* This is long word aligned thus could use a optimized version */ 
	memset(new_fds, 0, size); 

730 731
	if (new_fdt->max_fds > open_files) {
		int left = (new_fdt->max_fds-open_files)/8;
Linus Torvalds's avatar
Linus Torvalds committed
732 733
		int start = open_files / (8 * sizeof(unsigned long));

734 735
		memset(&new_fdt->open_fds->fds_bits[start], 0, left);
		memset(&new_fdt->close_on_exec->fds_bits[start], 0, left);
Linus Torvalds's avatar
Linus Torvalds committed
736 737
	}

738
	return newf;
Linus Torvalds's avatar
Linus Torvalds committed
739 740 741

out_release:
	kmem_cache_free(files_cachep, newf);
742
out:
743
	return NULL;
Linus Torvalds's avatar
Linus Torvalds committed
744 745
}

746 747 748 749 750 751 752 753 754 755 756 757 758 759 760 761 762 763 764 765 766 767 768 769 770 771 772 773 774 775 776 777 778
static int copy_files(unsigned long clone_flags, struct task_struct * tsk)
{
	struct files_struct *oldf, *newf;
	int error = 0;

	/*
	 * A background process may not have any files ...
	 */
	oldf = current->files;
	if (!oldf)
		goto out;

	if (clone_flags & CLONE_FILES) {
		atomic_inc(&oldf->count);
		goto out;
	}

	/*
	 * Note: we may be using current for both targets (See exec.c)
	 * This works because we cache current->files (old) as oldf. Don't
	 * break this.
	 */
	tsk->files = NULL;
	newf = dup_fd(oldf, &error);
	if (!newf)
		goto out;

	tsk->files = newf;
	error = 0;
out:
	return error;
}

Linus Torvalds's avatar
Linus Torvalds committed
779 780 781 782 783 784 785 786 787 788 789
/*
 *	Helper to unshare the files of the current task.
 *	We don't want to expose copy_files internals to
 *	the exec layer of the kernel.
 */

int unshare_files(void)
{
	struct files_struct *files  = current->files;
	int rc;

790
	BUG_ON(!files);
Linus Torvalds's avatar
Linus Torvalds committed
791 792 793 794 795 796 797 798 799 800 801 802 803 804 805 806 807 808 809 810 811 812 813 814 815

	/* This can race but the race causes us to copy when we don't
	   need to and drop the copy */
	if(atomic_read(&files->count) == 1)
	{
		atomic_inc(&files->count);
		return 0;
	}
	rc = copy_files(0, current);
	if(rc)
		current->files = files;
	return rc;
}

EXPORT_SYMBOL(unshare_files);

static inline int copy_sighand(unsigned long clone_flags, struct task_struct * tsk)
{
	struct sighand_struct *sig;

	if (clone_flags & (CLONE_SIGHAND | CLONE_THREAD)) {
		atomic_inc(&current->sighand->count);
		return 0;
	}
	sig = kmem_cache_alloc(sighand_cachep, GFP_KERNEL);
Ingo Molnar's avatar
Ingo Molnar committed
816
	rcu_assign_pointer(tsk->sighand, sig);
Linus Torvalds's avatar
Linus Torvalds committed
817 818 819 820 821 822 823
	if (!sig)
		return -ENOMEM;
	atomic_set(&sig->count, 1);
	memcpy(sig->action, current->sighand->action, sizeof(sig->action));
	return 0;
}

824
void __cleanup_sighand(struct sighand_struct *sighand)
825 826 827 828 829
{
	if (atomic_dec_and_test(&sighand->count))
		kmem_cache_free(sighand_cachep, sighand);
}

Linus Torvalds's avatar
Linus Torvalds committed
830 831 832 833 834 835 836 837 838 839 840 841 842 843 844 845 846 847 848 849 850 851 852 853 854 855 856 857 858 859 860 861
static inline int copy_signal(unsigned long clone_flags, struct task_struct * tsk)
{
	struct signal_struct *sig;
	int ret;

	if (clone_flags & CLONE_THREAD) {
		atomic_inc(&current->signal->count);
		atomic_inc(&current->signal->live);
		return 0;
	}
	sig = kmem_cache_alloc(signal_cachep, GFP_KERNEL);
	tsk->signal = sig;
	if (!sig)
		return -ENOMEM;

	ret = copy_thread_group_keys(tsk);
	if (ret < 0) {
		kmem_cache_free(signal_cachep, sig);
		return ret;
	}

	atomic_set(&sig->count, 1);
	atomic_set(&sig->live, 1);
	init_waitqueue_head(&sig->wait_chldexit);
	sig->flags = 0;
	sig->group_exit_code = 0;
	sig->group_exit_task = NULL;
	sig->group_stop_count = 0;
	sig->curr_target = NULL;
	init_sigpending(&sig->shared_pending);
	INIT_LIST_HEAD(&sig->posix_timers);

862
	hrtimer_init(&sig->real_timer, CLOCK_MONOTONIC, HRTIMER_MODE_REL);
863
	sig->it_real_incr.tv64 = 0;
Linus Torvalds's avatar
Linus Torvalds committed
864
	sig->real_timer.function = it_real_fn;
865
	sig->tsk = tsk;
Linus Torvalds's avatar
Linus Torvalds committed
866 867 868 869 870 871 872

	sig->it_virt_expires = cputime_zero;
	sig->it_virt_incr = cputime_zero;
	sig->it_prof_expires = cputime_zero;
	sig->it_prof_incr = cputime_zero;

	sig->leader = 0;	/* session leadership doesn't inherit */
873
	sig->tty_old_pgrp = NULL;
Linus Torvalds's avatar
Linus Torvalds committed
874 875 876 877 878 879 880 881

	sig->utime = sig->stime = sig->cutime = sig->cstime = cputime_zero;
	sig->nvcsw = sig->nivcsw = sig->cnvcsw = sig->cnivcsw = 0;
	sig->min_flt = sig->maj_flt = sig->cmin_flt = sig->cmaj_flt = 0;
	sig->sched_time = 0;
	INIT_LIST_HEAD(&sig->cpu_timers[0]);
	INIT_LIST_HEAD(&sig->cpu_timers[1]);
	INIT_LIST_HEAD(&sig->cpu_timers[2]);
882
	taskstats_tgid_init(sig);
Linus Torvalds's avatar
Linus Torvalds committed
883 884 885 886 887 888 889 890 891 892 893 894 895

	task_lock(current->group_leader);
	memcpy(sig->rlim, current->signal->rlim, sizeof sig->rlim);
	task_unlock(current->group_leader);

	if (sig->rlim[RLIMIT_CPU].rlim_cur != RLIM_INFINITY) {
		/*
		 * New sole thread in the process gets an expiry time
		 * of the whole CPU time limit.
		 */
		tsk->it_prof_expires =
			secs_to_cputime(sig->rlim[RLIMIT_CPU].rlim_cur);
	}
896
	acct_init_pacct(&sig->pacct);
Linus Torvalds's avatar
Linus Torvalds committed
897 898 899 900

	return 0;
}

901 902 903 904 905 906 907 908 909 910 911 912 913 914 915 916
void __cleanup_signal(struct signal_struct *sig)
{
	exit_thread_group_keys(sig);
	kmem_cache_free(signal_cachep, sig);
}

static inline void cleanup_signal(struct task_struct *tsk)
{
	struct signal_struct *sig = tsk->signal;

	atomic_dec(&sig->live);

	if (atomic_dec_and_test(&sig->count))
		__cleanup_signal(sig);
}

Linus Torvalds's avatar
Linus Torvalds committed
917 918 919 920
static inline void copy_flags(unsigned long clone_flags, struct task_struct *p)
{
	unsigned long new_flags = p->flags;

921
	new_flags &= ~(PF_SUPERPRIV | PF_NOFREEZE);
Linus Torvalds's avatar
Linus Torvalds committed
922 923 924 925 926 927 928 929 930 931 932 933 934
	new_flags |= PF_FORKNOEXEC;
	if (!(clone_flags & CLONE_PTRACE))
		p->ptrace = 0;
	p->flags = new_flags;
}

asmlinkage long sys_set_tid_address(int __user *tidptr)
{
	current->clear_child_tid = tidptr;

	return current->pid;
}

935 936 937
static inline void rt_mutex_init_task(struct task_struct *p)
{
	spin_lock_init(&p->pi_lock);
938
#ifdef CONFIG_RT_MUTEXES
939 940 941 942 943
	plist_head_init(&p->pi_waiters, &p->pi_lock);
	p->pi_blocked_on = NULL;
#endif
}

Linus Torvalds's avatar
Linus Torvalds committed
944 945 946 947 948 949 950 951
/*
 * This creates a new process as a copy of the old one,
 * but does not actually start it yet.
 *
 * It copies the registers, and all the appropriate
 * parts of the process environment (as per the clone
 * flags). The actual kick-off is left to the caller.
 */
952 953 954 955 956 957 958
static struct task_struct *copy_process(unsigned long clone_flags,
					unsigned long stack_start,
					struct pt_regs *regs,
					unsigned long stack_size,
					int __user *parent_tidptr,
					int __user *child_tidptr,
					int pid)
Linus Torvalds's avatar
Linus Torvalds committed
959 960 961 962 963 964 965 966 967 968 969 970 971 972 973 974 975 976 977 978 979 980 981 982 983 984 985 986 987 988 989
{
	int retval;
	struct task_struct *p = NULL;

	if ((clone_flags & (CLONE_NEWNS|CLONE_FS)) == (CLONE_NEWNS|CLONE_FS))
		return ERR_PTR(-EINVAL);

	/*
	 * Thread groups must share signals as well, and detached threads
	 * can only be started up within the thread group.
	 */
	if ((clone_flags & CLONE_THREAD) && !(clone_flags & CLONE_SIGHAND))
		return ERR_PTR(-EINVAL);

	/*
	 * Shared signal handlers imply shared VM. By way of the above,
	 * thread groups also imply shared VM. Blocking this case allows
	 * for various simplifications in other code.
	 */
	if ((clone_flags & CLONE_SIGHAND) && !(clone_flags & CLONE_VM))
		return ERR_PTR(-EINVAL);

	retval = security_task_create(clone_flags);
	if (retval)
		goto fork_out;

	retval = -ENOMEM;
	p = dup_task_struct(current);
	if (!p)
		goto fork_out;

990 991
	rt_mutex_init_task(p);

992 993 994 995
#ifdef CONFIG_TRACE_IRQFLAGS
	DEBUG_LOCKS_WARN_ON(!p->hardirqs_enabled);
	DEBUG_LOCKS_WARN_ON(!p->softirqs_enabled);
#endif
Linus Torvalds's avatar
Linus Torvalds committed
996 997 998 999 1000 1001 1002 1003 1004 1005 1006 1007 1008 1009 1010 1011 1012 1013 1014 1015
	retval = -EAGAIN;
	if (atomic_read(&p->user->processes) >=
			p->signal->rlim[RLIMIT_NPROC].rlim_cur) {
		if (!capable(CAP_SYS_ADMIN) && !capable(CAP_SYS_RESOURCE) &&
				p->user != &root_user)
			goto bad_fork_free;
	}

	atomic_inc(&p->user->__count);
	atomic_inc(&p->user->processes);
	get_group_info(p->group_info);

	/*
	 * If multiple threads are within copy_process(), then this check
	 * triggers too late. This doesn't hurt, the check is only there
	 * to stop root fork bombs.
	 */
	if (nr_threads >= max_threads)
		goto bad_fork_cleanup_count;

1016
	if (!try_module_get(task_thread_info(p)->exec_domain->module))
Linus Torvalds's avatar
Linus Torvalds committed
1017 1018 1019 1020 1021 1022
		goto bad_fork_cleanup_count;

	if (p->binfmt && !try_module_get(p->binfmt->module))
		goto bad_fork_cleanup_put_domain;

	p->did_exec = 0;
1023
	delayacct_tsk_init(p);	/* Must remain after dup_task_struct() */
Linus Torvalds's avatar
Linus Torvalds committed
1024 1025 1026 1027 1028
	copy_flags(clone_flags, p);
	p->pid = pid;
	retval = -EFAULT;
	if (clone_flags & CLONE_PARENT_SETTID)
		if (put_user(p->pid, parent_tidptr))
1029
			goto bad_fork_cleanup_delays_binfmt;
Linus Torvalds's avatar
Linus Torvalds committed
1030 1031 1032 1033 1034 1035 1036 1037 1038 1039 1040 1041

	INIT_LIST_HEAD(&p->children);
	INIT_LIST_HEAD(&p->sibling);
	p->vfork_done = NULL;
	spin_lock_init(&p->alloc_lock);

	clear_tsk_thread_flag(p, TIF_SIGPENDING);
	init_sigpending(&p->pending);

	p->utime = cputime_zero;
	p->stime = cputime_zero;
 	p->sched_time = 0;
1042
#ifdef CONFIG_TASK_XACCT
Linus Torvalds's avatar
Linus Torvalds committed
1043 1044 1045 1046
	p->rchar = 0;		/* I/O counter: bytes read */
	p->wchar = 0;		/* I/O counter: bytes written */
	p->syscr = 0;		/* I/O counter: read syscalls */
	p->syscw = 0;		/* I/O counter: write syscalls */
1047
#endif
1048
	task_io_accounting_init(p);
Linus Torvalds's avatar
Linus Torvalds committed
1049 1050 1051 1052 1053 1054 1055 1056 1057 1058 1059 1060 1061 1062 1063
	acct_clear_integrals(p);

 	p->it_virt_expires = cputime_zero;
	p->it_prof_expires = cputime_zero;
 	p->it_sched_expires = 0;
 	INIT_LIST_HEAD(&p->cpu_timers[0]);
 	INIT_LIST_HEAD(&p->cpu_timers[1]);
 	INIT_LIST_HEAD(&p->cpu_timers[2]);

	p->lock_depth = -1;		/* -1 = no lock */
	do_posix_clock_monotonic_gettime(&p->start_time);
	p->security = NULL;
	p->io_context = NULL;
	p->io_wait = NULL;
	p->audit_context = NULL;
Paul Jackson's avatar
Paul Jackson committed
1064
	cpuset_fork(p);
Linus Torvalds's avatar
Linus Torvalds committed
1065 1066 1067 1068 1069
#ifdef CONFIG_NUMA
 	p->mempolicy = mpol_copy(p->mempolicy);
 	if (IS_ERR(p->mempolicy)) {
 		retval = PTR_ERR(p->mempolicy);
 		p->mempolicy = NULL;
Paul Jackson's avatar
Paul Jackson committed
1070
 		goto bad_fork_cleanup_cpuset;
Linus Torvalds's avatar
Linus Torvalds committed
1071
 	}
1072
	mpol_fix_fork_child_flag(p);
Linus Torvalds's avatar
Linus Torvalds committed
1073
#endif
1074 1075
#ifdef CONFIG_TRACE_IRQFLAGS
	p->irq_events = 0;
1076 1077 1078
#ifdef __ARCH_WANT_INTERRUPTS_ON_CTXSW
	p->hardirqs_enabled = 1;
#else
1079
	p->hardirqs_enabled = 0;
1080
#endif
1081 1082 1083 1084 1085 1086 1087 1088 1089 1090 1091 1092
	p->hardirq_enable_ip = 0;
	p->hardirq_enable_event = 0;
	p->hardirq_disable_ip = _THIS_IP_;
	p->hardirq_disable_event = 0;
	p->softirqs_enabled = 1;
	p->softirq_enable_ip = _THIS_IP_;
	p->softirq_enable_event = 0;
	p->softirq_disable_ip = 0;
	p->softirq_disable_event = 0;
	p->hardirq_context = 0;
	p->softirq_context = 0;
#endif
Ingo Molnar's avatar
Ingo Molnar committed
1093 1094 1095 1096 1097
#ifdef CONFIG_LOCKDEP
	p->lockdep_depth = 0; /* no locks held yet */
	p->curr_chain_key = 0;
	p->lockdep_recursion = 0;
#endif
Linus Torvalds's avatar
Linus Torvalds committed
1098

1099 1100 1101 1102
#ifdef CONFIG_DEBUG_MUTEXES
	p->blocked_on = NULL; /* not blocked yet */
#endif

Linus Torvalds's avatar
Linus Torvalds committed
1103 1104 1105 1106 1107 1108 1109 1110 1111 1112 1113 1114 1115 1116 1117 1118 1119 1120 1121 1122 1123 1124 1125
	p->tgid = p->pid;
	if (clone_flags & CLONE_THREAD)
		p->tgid = current->tgid;

	if ((retval = security_task_alloc(p)))
		goto bad_fork_cleanup_policy;
	if ((retval = audit_alloc(p)))
		goto bad_fork_cleanup_security;
	/* copy all the process information */
	if ((retval = copy_semundo(clone_flags, p)))
		goto bad_fork_cleanup_audit;
	if ((retval = copy_files(clone_flags, p)))
		goto bad_fork_cleanup_semundo;
	if ((retval = copy_fs(clone_flags, p)))
		goto bad_fork_cleanup_files;
	if ((retval = copy_sighand(clone_flags, p)))
		goto bad_fork_cleanup_fs;
	if ((retval = copy_signal(clone_flags, p)))
		goto bad_fork_cleanup_sighand;
	if ((retval = copy_mm(clone_flags, p)))
		goto bad_fork_cleanup_signal;
	if ((retval = copy_keys(clone_flags, p)))
		goto bad_fork_cleanup_mm;
1126
	if ((retval = copy_namespaces(clone_flags, p)))
Linus Torvalds's avatar
Linus Torvalds committed
1127 1128 1129
		goto bad_fork_cleanup_keys;
	retval = copy_thread(0, clone_flags, stack_start, stack_size, p, regs);
	if (retval)
1130
		goto bad_fork_cleanup_namespaces;
Linus Torvalds's avatar
Linus Torvalds committed
1131 1132 1133 1134 1135 1136

	p->set_child_tid = (clone_flags & CLONE_CHILD_SETTID) ? child_tidptr : NULL;
	/*
	 * Clear TID on mm_release()?
	 */
	p->clear_child_tid = (clone_flags & CLONE_CHILD_CLEARTID) ? child_tidptr: NULL;
1137 1138 1139 1140
	p->robust_list = NULL;
#ifdef CONFIG_COMPAT
	p->compat_robust_list = NULL;
#endif
1141 1142 1143
	INIT_LIST_HEAD(&p->pi_state_list);
	p->pi_state_cache = NULL;

1144 1145 1146 1147 1148 1149
	/*
	 * sigaltstack should be cleared when sharing the same VM
	 */
	if ((clone_flags & (CLONE_VM|CLONE_VFORK)) == CLONE_VM)
		p->sas_ss_sp = p->sas_ss_size = 0;

Linus Torvalds's avatar
Linus Torvalds committed
1150 1151 1152 1153 1154
	/*
	 * Syscall tracing should be turned off in the child regardless
	 * of CLONE_PTRACE.
	 */
	clear_tsk_thread_flag(p, TIF_SYSCALL_TRACE);
1155 1156 1157
#ifdef TIF_SYSCALL_EMU
	clear_tsk_thread_flag(p, TIF_SYSCALL_EMU);
#endif
Linus Torvalds's avatar
Linus Torvalds committed
1158 1159 1160 1161 1162 1163 1164 1165 1166 1167 1168 1169 1170 1171 1172

	/* Our parent execution domain becomes current domain
	   These must match for thread signalling to apply */
	p->parent_exec_id = p->self_exec_id;

	/* ok, now we should be set up.. */
	p->exit_signal = (clone_flags & CLONE_THREAD) ? -1 : (clone_flags & CSIGNAL);
	p->pdeath_signal = 0;
	p->exit_state = 0;

	/*
	 * Ok, make it visible to the rest of the system.
	 * We dont wake it up yet.
	 */
	p->group_leader = p;
1173
	INIT_LIST_HEAD(&p->thread_group);
Linus Torvalds's avatar
Linus Torvalds committed
1174 1175 1176
	INIT_LIST_HEAD(&p->ptrace_children);
	INIT_LIST_HEAD(&p->ptrace_list);

1177 1178 1179
	/* Perform scheduler related setup. Assign this task to a CPU. */
	sched_fork(p, clone_flags);

Linus Torvalds's avatar
Linus Torvalds committed
1180 1181 1182
	/* Need tasklist lock for parent etc handling! */
	write_lock_irq(&tasklist_lock);

1183 1184 1185
	/* for sys_ioprio_set(IOPRIO_WHO_PGRP) */
	p->ioprio = current->ioprio;

Linus Torvalds's avatar
Linus Torvalds committed
1186
	/*
1187 1188 1189 1190 1191 1192 1193
	 * The task hasn't been attached yet, so its cpus_allowed mask will
	 * not be changed, nor will its assigned CPU.
	 *
	 * The cpus_allowed mask of the parent may have changed after it was
	 * copied first time - so re-copy it here, then check the child's CPU
	 * to ensure it is on a valid CPU (and if not, just force it back to
	 * parent's CPU). This avoids alot of nasty races.
Linus Torvalds's avatar
Linus Torvalds committed
1194 1195
	 */
	p->cpus_allowed = current->cpus_allowed;
1196 1197
	if (unlikely(!cpu_isset(task_cpu(p), p->cpus_allowed) ||
			!cpu_online(task_cpu(p))))
1198
		set_task_cpu(p, smp_processor_id());
Linus Torvalds's avatar
Linus Torvalds committed
1199 1200 1201 1202 1203 1204 1205 1206

	/* CLONE_PARENT re-uses the old parent */
	if (clone_flags & (CLONE_PARENT|CLONE_THREAD))
		p->real_parent = current->real_parent;
	else
		p->real_parent = current;
	p->parent = p->real_parent;

1207
	spin_lock(&current->sighand->siglock);
1208 1209 1210 1211 1212 1213 1214 1215 1216 1217 1218 1219 1220 1221

	/*
	 * Process group and session signals need to be delivered to just the
	 * parent before the fork or both the parent and the child after the
	 * fork. Restart if a signal comes in before we add the new process to
	 * it's process group.
	 * A fatal signal pending means that current will exit, so the new
	 * thread can't slip out of an OOM kill (or normal SIGKILL).
 	 */
 	recalc_sigpending();
	if (signal_pending(current)) {
		spin_unlock(&current->sighand->siglock);
		write_unlock_irq(&tasklist_lock);
		retval = -ERESTARTNOINTR;
1222
		goto bad_fork_cleanup_namespaces;
1223 1224
	}

Linus Torvalds's avatar
Linus Torvalds committed
1225 1226
	if (clone_flags & CLONE_THREAD) {
		p->group_leader = current->group_leader;
1227
		list_add_tail_rcu(&p->thread_group, &p->group_leader->thread_group);
Linus Torvalds's avatar
Linus Torvalds committed
1228 1229 1230 1231 1232 1233 1234 1235 1236 1237 1238 1239 1240 1241 1242 1243 1244

		if (!cputime_eq(current->signal->it_virt_expires,
				cputime_zero) ||
		    !cputime_eq(current->signal->it_prof_expires,
				cputime_zero) ||
		    current->signal->rlim[RLIMIT_CPU].rlim_cur != RLIM_INFINITY ||
		    !list_empty(&current->signal->cpu_timers[0]) ||
		    !list_empty(&current->signal->cpu_timers[1]) ||
		    !list_empty(&current->signal->cpu_timers[2])) {
			/*
			 * Have child wake up on its first tick to check
			 * for process CPU timers.
			 */
			p->it_prof_expires = jiffies_to_cputime(1);
		}
	}

1245 1246 1247 1248 1249 1250 1251 1252
	if (likely(p->pid)) {
		add_parent(p);
		if (unlikely(p->ptrace & PT_PTRACED))
			__ptrace_link(p, current->parent);

		if (thread_group_leader(p)) {
			p->signal->tty = current->signal->tty;
			p->signal->pgrp = process_group(current);
1253
			set_signal_session(p->signal, process_session(current));
1254
			attach_pid(p, PIDTYPE_PGID, process_group(p));
1255
			attach_pid(p, PIDTYPE_SID, process_session(p));
1256

1257
			list_add_tail_rcu(&p->tasks, &init_task.tasks);
Linus Torvalds's avatar
Linus Torvalds committed
1258
			__get_cpu_var(process_counts)++;
1259 1260 1261
		}
		attach_pid(p, PIDTYPE_PID, p->pid);
		nr_threads++;
Linus Torvalds's avatar
Linus Torvalds committed
1262 1263 1264
	}

	total_forks++;
1265
	spin_unlock(&current->sighand->siglock);
Linus Torvalds's avatar
Linus Torvalds committed
1266
	write_unlock_irq(&tasklist_lock);
1267
	proc_fork_connector(p);
Linus Torvalds's avatar
Linus Torvalds committed
1268 1269
	return p;

1270
bad_fork_cleanup_namespaces:
1271
	exit_task_namespaces(p);
Linus Torvalds's avatar
Linus Torvalds committed
1272 1273 1274 1275 1276 1277
bad_fork_cleanup_keys:
	exit_keys(p);
bad_fork_cleanup_mm:
	if (p->mm)
		mmput(p->mm);
bad_fork_cleanup_signal:
1278
	cleanup_signal(p);
Linus Torvalds's avatar
Linus Torvalds committed
1279
bad_fork_cleanup_sighand:
1280
	__cleanup_sighand(p->sighand);
Linus Torvalds's avatar
Linus Torvalds committed
1281 1282 1283 1284 1285 1286 1287 1288 1289 1290 1291 1292 1293
bad_fork_cleanup_fs:
	exit_fs(p); /* blocking */
bad_fork_cleanup_files:
	exit_files(p); /* blocking */
bad_fork_cleanup_semundo:
	exit_sem(p);
bad_fork_cleanup_audit:
	audit_free(p);
bad_fork_cleanup_security:
	security_task_free(p);
bad_fork_cleanup_policy:
#ifdef CONFIG_NUMA
	mpol_free(p->mempolicy);
Paul Jackson's avatar
Paul Jackson committed
1294
bad_fork_cleanup_cpuset:
Linus Torvalds's avatar
Linus Torvalds committed
1295
#endif
Paul Jackson's avatar
Paul Jackson committed
1296
	cpuset_exit(p);
1297 1298
bad_fork_cleanup_delays_binfmt:
	delayacct_tsk_free(p);
Linus Torvalds's avatar
Linus Torvalds committed
1299 1300 1301
	if (p->binfmt)
		module_put(p->binfmt->module);
bad_fork_cleanup_put_domain:
1302
	module_put(task_thread_info(p)->exec_domain->module);
Linus Torvalds's avatar
Linus Torvalds committed
1303 1304 1305 1306 1307 1308
bad_fork_cleanup_count:
	put_group_info(p->group_info);
	atomic_dec(&p->user->processes);
	free_uid(p->user);
bad_fork_free:
	free_task(p);
1309 1310
fork_out:
	return ERR_PTR(retval);
Linus Torvalds's avatar
Linus Torvalds committed
1311 1312
}

1313
noinline struct pt_regs * __devinit __attribute__((weak)) idle_regs(struct pt_regs *regs)
Linus Torvalds's avatar
Linus Torvalds committed
1314 1315 1316 1317 1318
{
	memset(regs, 0, sizeof(struct pt_regs));
	return regs;
}

1319
struct task_struct * __cpuinit fork_idle(int cpu)
Linus Torvalds's avatar
Linus Torvalds committed
1320
{
1321
	struct task_struct *task;
Linus Torvalds's avatar
Linus Torvalds committed
1322 1323 1324
	struct pt_regs regs;

	task = copy_process(CLONE_VM, 0, idle_regs(&regs), 0, NULL, NULL, 0);
1325 1326
	if (!IS_ERR(task))
		init_idle(task, cpu);
1327

Linus Torvalds's avatar
Linus Torvalds committed
1328 1329 1330 1331 1332 1333 1334 1335 1336 1337 1338 1339 1340 1341 1342 1343 1344 1345 1346 1347 1348 1349 1350 1351 1352 1353 1354 1355 1356 1357 1358 1359 1360 1361
	return task;
}

static inline int fork_traceflag (unsigned clone_flags)
{
	if (clone_flags & CLONE_UNTRACED)
		return 0;
	else if (clone_flags & CLONE_VFORK) {
		if (current->ptrace & PT_TRACE_VFORK)
			return PTRACE_EVENT_VFORK;
	} else if ((clone_flags & CSIGNAL) != SIGCHLD) {
		if (current->ptrace & PT_TRACE_CLONE)
			return PTRACE_EVENT_CLONE;
	} else if (current->ptrace & PT_TRACE_FORK)
		return PTRACE_EVENT_FORK;

	return 0;
}

/*
 *  Ok, this is the main fork-routine.
 *
 * It copies the process, and if successful kick-starts
 * it and waits for it to finish using the VM if required.
 */
long do_fork(unsigned long clone_flags,
	      unsigned long stack_start,
	      struct pt_regs *regs,
	      unsigned long stack_size,
	      int __user *parent_tidptr,
	      int __user *child_tidptr)
{
	struct task_struct *p;
	int trace = 0;
1362 1363
	struct pid *pid = alloc_pid();
	long nr;
Linus Torvalds's avatar
Linus Torvalds committed
1364

1365
	if (!pid)
Linus Torvalds's avatar
Linus Torvalds committed
1366
		return -EAGAIN;
1367
	nr = pid->nr;
Linus Torvalds's avatar
Linus Torvalds committed
1368 1369 1370 1371 1372 1373
	if (unlikely(current->ptrace)) {
		trace = fork_traceflag (clone_flags);
		if (trace)
			clone_flags |= CLONE_PTRACE;
	}

1374
	p = copy_process(clone_flags, stack_start, regs, stack_size, parent_tidptr, child_tidptr, nr);
Linus Torvalds's avatar
Linus Torvalds committed
1375 1376 1377 1378 1379 1380 1381 1382 1383 1384 1385 1386 1387 1388 1389 1390 1391 1392 1393 1394 1395 1396 1397 1398 1399 1400
	/*
	 * Do this prior waking up the new thread - the thread pointer
	 * might get invalid after that point, if the thread exits quickly.
	 */
	if (!IS_ERR(p)) {
		struct completion vfork;

		if (clone_flags & CLONE_VFORK) {
			p->vfork_done = &vfork;
			init_completion(&vfork);
		}

		if ((p->ptrace & PT_PTRACED) || (clone_flags & CLONE_STOPPED)) {
			/*
			 * We'll start up with an immediate SIGSTOP.
			 */
			sigaddset(&p->pending.signal, SIGSTOP);
			set_tsk_thread_flag(p, TIF_SIGPENDING);
		}

		if (!(clone_flags & CLONE_STOPPED))
			wake_up_new_task(p, clone_flags);
		else
			p->state = TASK_STOPPED;

		if (unlikely (trace)) {
1401
			current->ptrace_message = nr;
Linus Torvalds's avatar
Linus Torvalds committed
1402 1403 1404 1405 1406
			ptrace_notify ((trace << 8) | SIGTRAP);
		}

		if (clone_flags & CLONE_VFORK) {
			wait_for_completion(&vfork);
1407 1408
			if (unlikely (current->ptrace & PT_TRACE_VFORK_DONE)) {
				current->ptrace_message = nr;
Linus Torvalds's avatar
Linus Torvalds committed
1409
				ptrace_notify ((PTRACE_EVENT_VFORK_DONE << 8) | SIGTRAP);
1410
			}
Linus Torvalds's avatar
Linus Torvalds committed
1411 1412
		}
	} else {
1413 1414
		free_pid(pid);
		nr = PTR_ERR(p);
Linus Torvalds's avatar
Linus Torvalds committed
1415
	}
1416
	return nr;
Linus Torvalds's avatar
Linus Torvalds committed
1417 1418
}

1419 1420 1421 1422
#ifndef ARCH_MIN_MMSTRUCT_ALIGN
#define ARCH_MIN_MMSTRUCT_ALIGN 0
#endif

1423
static void sighand_ctor(void *data, struct kmem_cache *cachep, unsigned long flags)
1424 1425 1426
{
	struct sighand_struct *sighand = data;

1427
	if (flags & SLAB_CTOR_CONSTRUCTOR)
1428 1429 1430
		spin_lock_init(&sighand->siglock);
}

Linus Torvalds's avatar
Linus Torvalds committed
1431 1432 1433 1434
void __init proc_caches_init(void)
{
	sighand_cachep = kmem_cache_create("sighand_cache",
			sizeof(struct sighand_struct), 0,
1435 1436
			SLAB_HWCACHE_ALIGN|SLAB_PANIC|SLAB_DESTROY_BY_RCU,
			sighand_ctor, NULL);
Linus Torvalds's avatar
Linus Torvalds committed
1437 1438 1439 1440 1441 1442 1443 1444 1445 1446 1447 1448 1449
	signal_cachep = kmem_cache_create("signal_cache",
			sizeof(struct signal_struct), 0,
			SLAB_HWCACHE_ALIGN|SLAB_PANIC, NULL, NULL);
	files_cachep = kmem_cache_create("files_cache", 
			sizeof(struct files_struct), 0,
			SLAB_HWCACHE_ALIGN|SLAB_PANIC, NULL, NULL);
	fs_cachep = kmem_cache_create("fs_cache", 
			sizeof(struct fs_struct), 0,
			SLAB_HWCACHE_ALIGN|SLAB_PANIC, NULL, NULL);
	vm_area_cachep = kmem_cache_create("vm_area_struct",
			sizeof(struct vm_area_struct), 0,
			SLAB_PANIC, NULL, NULL);
	mm_cachep = kmem_cache_create("mm_struct",
1450
			sizeof(struct mm_struct), ARCH_MIN_MMSTRUCT_ALIGN,
Linus Torvalds's avatar
Linus Torvalds committed
1451 1452
			SLAB_HWCACHE_ALIGN|SLAB_PANIC, NULL, NULL);
}
1453 1454 1455 1456 1457 1458 1459 1460 1461 1462 1463 1464 1465 1466 1467 1468 1469 1470 1471 1472 1473 1474 1475 1476 1477 1478 1479 1480 1481 1482 1483 1484 1485 1486 1487 1488 1489 1490 1491 1492 1493 1494 1495 1496 1497 1498 1499 1500


/*
 * Check constraints on flags passed to the unshare system call and
 * force unsharing of additional process context as appropriate.
 */
static inline void check_unshare_flags(unsigned long *flags_ptr)
{
	/*
	 * If unsharing a thread from a thread group, must also
	 * unshare vm.
	 */
	if (*flags_ptr & CLONE_THREAD)
		*flags_ptr |= CLONE_VM;

	/*
	 * If unsharing vm, must also unshare signal handlers.
	 */
	if (*flags_ptr & CLONE_VM)
		*flags_ptr |= CLONE_SIGHAND;

	/*
	 * If unsharing signal handlers and the task was created
	 * using CLONE_THREAD, then must unshare the thread
	 */
	if ((*flags_ptr & CLONE_SIGHAND) &&
	    (atomic_read(&current->signal->count) > 1))
		*flags_ptr |= CLONE_THREAD;

	/*
	 * If unsharing namespace, must also unshare filesystem information.
	 */
	if (*flags_ptr & CLONE_NEWNS)
		*flags_ptr |= CLONE_FS;
}

/*
 * Unsharing of tasks created with CLONE_THREAD is not supported yet
 */
static int unshare_thread(unsigned long unshare_flags)
{
	if (unshare_flags & CLONE_THREAD)
		return -EINVAL;

	return 0;
}

/*
1501
 * Unshare the filesystem structure if it is being shared
1502 1503 1504 1505 1506 1507
 */
static int unshare_fs(unsigned long unshare_flags, struct fs_struct **new_fsp)
{
	struct fs_struct *fs = current->fs;

	if ((unshare_flags & CLONE_FS) &&
1508 1509 1510 1511 1512
	    (fs && atomic_read(&fs->count) > 1)) {
		*new_fsp = __copy_fs_struct(current->fs);
		if (!*new_fsp)
			return -ENOMEM;
	}
1513 1514 1515 1516 1517

	return 0;
}

/*
1518
 * Unsharing of sighand is not supported yet
1519 1520 1521 1522 1523
 */
static int unshare_sighand(unsigned long unshare_flags, struct sighand_struct **new_sighp)
{
	struct sighand_struct *sigh = current->sighand;

1524
	if ((unshare_flags & CLONE_SIGHAND) && atomic_read(&sigh->count) > 1)
1525 1526 1527 1528 1529 1530
		return -EINVAL;
	else
		return 0;
}

/*
1531
 * Unshare vm if it is being shared
1532 1533 1534 1535 1536 1537
 */
static int unshare_vm(unsigned long unshare_flags, struct mm_struct **new_mmp)
{
	struct mm_struct *mm = current->mm;

	if ((unshare_flags & CLONE_VM) &&
1538
	    (mm && atomic_read(&mm->mm_users) > 1)) {
1539
		return -EINVAL;
1540
	}
1541 1542 1543 1544 1545

	return 0;
}

/*
1546
 * Unshare file descriptor table if it is being shared
1547 1548 1549 1550
 */
static int unshare_fd(unsigned long unshare_flags, struct files_struct **new_fdp)
{
	struct files_struct *fd = current->files;
1551
	int error = 0;
1552 1553

	if ((unshare_flags & CLONE_FILES) &&
1554 1555 1556 1557 1558
	    (fd && atomic_read(&fd->count) > 1)) {
		*new_fdp = dup_fd(fd, &error);
		if (!*new_fdp)
			return error;
	}
1559 1560 1561 1562 1563 1564 1565 1566 1567 1568 1569 1570 1571 1572 1573 1574 1575 1576 1577 1578 1579 1580 1581 1582 1583 1584 1585 1586

	return 0;
}

/*
 * Unsharing of semundo for tasks created with CLONE_SYSVSEM is not
 * supported yet
 */
static int unshare_semundo(unsigned long unshare_flags, struct sem_undo_list **new_ulistp)
{
	if (unshare_flags & CLONE_SYSVSEM)
		return -EINVAL;

	return 0;
}

/*
 * unshare allows a process to 'unshare' part of the process
 * context which was originally shared using clone.  copy_*
 * functions used by do_fork() cannot be used here directly
 * because they modify an inactive task_struct that is being
 * constructed. Here we are modifying the current, active,
 * task_struct.
 */
asmlinkage long sys_unshare(unsigned long unshare_flags)
{
	int err = 0;
	struct fs_struct *fs, *new_fs = NULL;
1587
	struct sighand_struct *new_sigh = NULL;
1588 1589 1590
	struct mm_struct *mm, *new_mm = NULL, *active_mm = NULL;
	struct files_struct *fd, *new_fd = NULL;
	struct sem_undo_list *new_ulist = NULL;
1591
	struct nsproxy *new_nsproxy = NULL, *old_nsproxy = NULL;
1592 1593 1594

	check_unshare_flags(&unshare_flags);

1595 1596 1597
	/* Return -EINVAL for all unsupported flags */
	err = -EINVAL;
	if (unshare_flags & ~(CLONE_THREAD|CLONE_FS|CLONE_NEWNS|CLONE_SIGHAND|
Kirill Korotaev's avatar
Kirill Korotaev committed
1598 1599
				CLONE_VM|CLONE_FILES|CLONE_SYSVSEM|
				CLONE_NEWUTS|CLONE_NEWIPC))
1600 1601
		goto bad_unshare_out;

1602 1603 1604 1605 1606
	if ((err = unshare_thread(unshare_flags)))
		goto bad_unshare_out;
	if ((err = unshare_fs(unshare_flags, &new_fs)))
		goto bad_unshare_cleanup_thread;
	if ((err = unshare_sighand(unshare_flags, &new_sigh)))
1607
		goto bad_unshare_cleanup_fs;
1608 1609 1610 1611 1612 1613
	if ((err = unshare_vm(unshare_flags, &new_mm)))
		goto bad_unshare_cleanup_sigh;
	if ((err = unshare_fd(unshare_flags, &new_fd)))
		goto bad_unshare_cleanup_vm;
	if ((err = unshare_semundo(unshare_flags, &new_ulist)))
		goto bad_unshare_cleanup_fd;
1614 1615
	if ((err = unshare_nsproxy_namespaces(unshare_flags, &new_nsproxy,
			new_fs)))
1616
		goto bad_unshare_cleanup_semundo;
1617

1618
	if (new_fs ||  new_mm || new_fd || new_ulist || new_nsproxy) {
1619

1620
		task_lock(current);
1621 1622

		if (new_nsproxy) {
1623
			old_nsproxy = current->nsproxy;
1624 1625 1626
			current->nsproxy = new_nsproxy;
			new_nsproxy = old_nsproxy;
		}
1627 1628 1629 1630 1631 1632 1633 1634 1635 1636 1637 1638 1639 1640 1641 1642 1643 1644 1645 1646 1647 1648 1649 1650 1651

		if (new_fs) {
			fs = current->fs;
			current->fs = new_fs;
			new_fs = fs;
		}

		if (new_mm) {
			mm = current->mm;
			active_mm = current->active_mm;
			current->mm = new_mm;
			current->active_mm = new_mm;
			activate_mm(active_mm, new_mm);
			new_mm = mm;
		}

		if (new_fd) {
			fd = current->files;
			current->files = new_fd;
			new_fd = fd;
		}

		task_unlock(current);
	}

1652
	if (new_nsproxy)
1653
		put_nsproxy(new_nsproxy);
1654

1655
bad_unshare_cleanup_semundo:
1656 1657 1658 1659 1660 1661 1662 1663 1664 1665 1666 1667 1668 1669 1670 1671 1672 1673 1674 1675 1676
bad_unshare_cleanup_fd:
	if (new_fd)
		put_files_struct(new_fd);

bad_unshare_cleanup_vm:
	if (new_mm)
		mmput(new_mm);

bad_unshare_cleanup_sigh:
	if (new_sigh)
		if (atomic_dec_and_test(&new_sigh->count))
			kmem_cache_free(sighand_cachep, new_sigh);

bad_unshare_cleanup_fs:
	if (new_fs)
		put_fs_struct(new_fs);

bad_unshare_cleanup_thread:
bad_unshare_out:
	return err;
}