fork.c 43.3 KB
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/*
 *  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>
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#include <linux/mnt_namespace.h>
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#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>
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#include <linux/nsproxy.h>
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#include <linux/capability.h>
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#include <linux/cpu.h>
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#include <linux/cgroup.h>
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#include <linux/security.h>
#include <linux/swap.h>
#include <linux/syscalls.h>
#include <linux/jiffies.h>
#include <linux/futex.h>
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#include <linux/task_io_accounting_ops.h>
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#include <linux/rcupdate.h>
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#include <linux/ptrace.h>
#include <linux/mount.h>
#include <linux/audit.h>
#include <linux/profile.h>
#include <linux/rmap.h>
#include <linux/acct.h>
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#include <linux/tsacct_kern.h>
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#include <linux/cn_proc.h>
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#include <linux/freezer.h>
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#include <linux/delayacct.h>
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#include <linux/taskstats_kern.h>
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#include <linux/random.h>
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#include <linux/tty.h>
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#include <linux/proc_fs.h>
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#include <linux/blkdev.h>
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#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;

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__cacheline_aligned DEFINE_RWLOCK(tasklist_lock);  /* outer */
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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))
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static struct kmem_cache *task_struct_cachep;
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#endif

/* SLAB cache for signal_struct structures (tsk->signal) */
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static struct kmem_cache *signal_cachep;
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/* SLAB cache for sighand_struct structures (tsk->sighand) */
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struct kmem_cache *sighand_cachep;
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/* SLAB cache for files_struct structures (tsk->files) */
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struct kmem_cache *files_cachep;
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/* SLAB cache for fs_struct structures (tsk->fs) */
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struct kmem_cache *fs_cachep;
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/* SLAB cache for vm_area_struct structures */
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struct kmem_cache *vm_area_cachep;
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/* SLAB cache for mm_struct structures (tsk->mm) */
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static struct kmem_cache *mm_cachep;
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void free_task(struct task_struct *tsk)
{
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	prop_local_destroy_single(&tsk->dirties);
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	free_thread_info(tsk->stack);
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	rt_mutex_debug_task_free(tsk);
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	free_task_struct(tsk);
}
EXPORT_SYMBOL(free_task);

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void __put_task_struct(struct task_struct *tsk)
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{
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	WARN_ON(!tsk->exit_state);
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	WARN_ON(atomic_read(&tsk->usage));
	WARN_ON(tsk == current);

	security_task_free(tsk);
	free_uid(tsk->user);
	put_group_info(tsk->group_info);
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	delayacct_tsk_free(tsk);
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	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),
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			ARCH_MIN_TASKALIGN, SLAB_PANIC, NULL);
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#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;
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	int err;
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	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;
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	tsk->stack = ti;
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	err = prop_local_init_single(&tsk->dirties);
	if (err) {
		free_thread_info(ti);
		free_task_struct(tsk);
		return NULL;
	}

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	setup_thread_stack(tsk, orig);
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#ifdef CONFIG_CC_STACKPROTECTOR
	tsk->stack_canary = get_random_int();
#endif

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	/* One for us, one for whoever does the "release_task()" (usually parent) */
	atomic_set(&tsk->usage,2);
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	atomic_set(&tsk->fs_excl, 0);
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#ifdef CONFIG_BLK_DEV_IO_TRACE
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	tsk->btrace_seq = 0;
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#endif
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	tsk->splice_pipe = NULL;
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	return tsk;
}

#ifdef CONFIG_MMU
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static int dup_mmap(struct mm_struct *mm, struct mm_struct *oldmm)
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{
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	struct vm_area_struct *mpnt, *tmp, **pprev;
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	struct rb_node **rb_link, *rb_parent;
	int retval;
	unsigned long charge;
	struct mempolicy *pol;

	down_write(&oldmm->mmap_sem);
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	flush_cache_dup_mm(oldmm);
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	/*
	 * Not linked in yet - no deadlock potential:
	 */
	down_write_nested(&mm->mmap_sem, SINGLE_DEPTH_NESTING);
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	mm->locked_vm = 0;
	mm->mmap = NULL;
	mm->mmap_cache = NULL;
	mm->free_area_cache = oldmm->mmap_base;
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	mm->cached_hole_size = ~0UL;
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	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;

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	for (mpnt = oldmm->mmap; mpnt; mpnt = mpnt->vm_next) {
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		struct file *file;

		if (mpnt->vm_flags & VM_DONTCOPY) {
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			long pages = vma_pages(mpnt);
			mm->total_vm -= pages;
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			vm_stat_account(mm, mpnt->vm_flags, mpnt->vm_file,
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								-pages);
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			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;
		}
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		tmp = kmem_cache_alloc(vm_area_cachep, GFP_KERNEL);
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		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) {
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			struct inode *inode = file->f_path.dentry->d_inode;
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			get_file(file);
			if (tmp->vm_flags & VM_DENYWRITE)
				atomic_dec(&inode->i_writecount);
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			/* 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);
		}

		/*
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		 * Link in the new vma and copy the page table entries.
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		 */
		*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++;
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		retval = copy_page_range(mm, oldmm, mpnt);
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		if (tmp->vm_ops && tmp->vm_ops->open)
			tmp->vm_ops->open(tmp);

		if (retval)
			goto out;
	}
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	/* a new mm has just been created */
	arch_dup_mmap(oldmm, mm);
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	retval = 0;
out:
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	up_write(&mm->mmap_sem);
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	flush_tlb_mm(oldmm);
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	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)
{
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	pgd_free(mm, mm->pgd);
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}
#else
#define dup_mmap(mm, oldmm)	(0)
#define mm_alloc_pgd(mm)	(0)
#define mm_free_pgd(mm)
#endif /* CONFIG_MMU */

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__cacheline_aligned_in_smp DEFINE_SPINLOCK(mmlist_lock);
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#define allocate_mm()	(kmem_cache_alloc(mm_cachep, GFP_KERNEL))
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#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);
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	mm->flags = (current->mm) ? current->mm->flags
				  : MMF_DUMP_FILTER_DEFAULT;
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	mm->core_waiters = 0;
	mm->nr_ptes = 0;
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	set_mm_counter(mm, file_rss, 0);
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	set_mm_counter(mm, anon_rss, 0);
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	spin_lock_init(&mm->page_table_lock);
	rwlock_init(&mm->ioctx_list_lock);
	mm->ioctx_list = NULL;
	mm->free_area_cache = TASK_UNMAPPED_BASE;
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	mm->cached_hole_size = ~0UL;
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	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);
}
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EXPORT_SYMBOL_GPL(__mmdrop);
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/*
 * Decrement the use count and release all resources for an mm.
 */
void mmput(struct mm_struct *mm)
{
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	might_sleep();

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	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);
	}
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	/*
	 * 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) {
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		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);
	}
}

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/*
 * 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));

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	/* Initializing for Swap token stuff */
	mm->token_priority = 0;
	mm->last_interval = 0;

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	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;
}

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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;
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	mm = dup_mm(tsk);
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	if (!mm)
		goto fail_nomem;

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

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	tsk->mm = mm;
	tsk->active_mm = mm;
	return 0;

fail_nomem:
	return retval;
}

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static struct fs_struct *__copy_fs_struct(struct fs_struct *old)
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{
	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);

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Alexey Dobriyan 已提交
621
static int copy_fs(unsigned long clone_flags, struct task_struct *tsk)
L
Linus Torvalds 已提交
622 623 624 625 626 627 628 629 630 631 632
{
	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;
}

633
static int count_open_files(struct fdtable *fdt)
L
Linus Torvalds 已提交
634
{
635
	int size = fdt->max_fds;
L
Linus Torvalds 已提交
636 637 638 639
	int i;

	/* Find the last open fd */
	for (i = size/(8*sizeof(long)); i > 0; ) {
640
		if (fdt->open_fds->fds_bits[--i])
L
Linus Torvalds 已提交
641 642 643 644 645 646
			break;
	}
	i = (i+1) * 8 * sizeof(long);
	return i;
}

647 648 649 650 651
static struct files_struct *alloc_files(void)
{
	struct files_struct *newf;
	struct fdtable *fdt;

652
	newf = kmem_cache_alloc(files_cachep, GFP_KERNEL);
653 654 655 656 657 658
	if (!newf)
		goto out;

	atomic_set(&newf->count, 1);

	spin_lock_init(&newf->file_lock);
659
	newf->next_fd = 0;
660
	fdt = &newf->fdtab;
661
	fdt->max_fds = NR_OPEN_DEFAULT;
662 663
	fdt->close_on_exec = (fd_set *)&newf->close_on_exec_init;
	fdt->open_fds = (fd_set *)&newf->open_fds_init;
664
	fdt->fd = &newf->fd_array[0];
665 666 667
	INIT_RCU_HEAD(&fdt->rcu);
	fdt->next = NULL;
	rcu_assign_pointer(newf->fdt, fdt);
668 669 670 671
out:
	return newf;
}

672 673 674
/*
 * Allocate a new files structure and copy contents from the
 * passed in files structure.
P
Prasanna Meda 已提交
675
 * errorp will be valid only when the returned files_struct is NULL.
676 677
 */
static struct files_struct *dup_fd(struct files_struct *oldf, int *errorp)
L
Linus Torvalds 已提交
678
{
679
	struct files_struct *newf;
L
Linus Torvalds 已提交
680
	struct file **old_fds, **new_fds;
681
	int open_files, size, i;
682
	struct fdtable *old_fdt, *new_fdt;
L
Linus Torvalds 已提交
683

P
Prasanna Meda 已提交
684
	*errorp = -ENOMEM;
685 686
	newf = alloc_files();
	if (!newf)
L
Linus Torvalds 已提交
687 688 689
		goto out;

	spin_lock(&oldf->file_lock);
690 691
	old_fdt = files_fdtable(oldf);
	new_fdt = files_fdtable(newf);
692
	open_files = count_open_files(old_fdt);
L
Linus Torvalds 已提交
693 694

	/*
695 696
	 * 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.
L
Linus Torvalds 已提交
697
	 */
698 699
	if (open_files > new_fdt->max_fds) {
		new_fdt->max_fds = 0;
L
Linus Torvalds 已提交
700 701
		spin_unlock(&oldf->file_lock);
		spin_lock(&newf->file_lock);
702
		*errorp = expand_files(newf, open_files-1);
L
Linus Torvalds 已提交
703
		spin_unlock(&newf->file_lock);
704
		if (*errorp < 0)
L
Linus Torvalds 已提交
705
			goto out_release;
706 707 708 709 710 711
		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.
		 */
L
Linus Torvalds 已提交
712
		spin_lock(&oldf->file_lock);
713
		old_fdt = files_fdtable(oldf);
L
Linus Torvalds 已提交
714 715
	}

716 717
	old_fds = old_fdt->fd;
	new_fds = new_fdt->fd;
L
Linus Torvalds 已提交
718

719 720 721 722
	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);
L
Linus Torvalds 已提交
723 724 725 726 727 728 729 730 731 732 733 734

	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.
			 */
735
			FD_CLR(open_files - i, new_fdt->open_fds);
L
Linus Torvalds 已提交
736
		}
737
		rcu_assign_pointer(*new_fds++, f);
L
Linus Torvalds 已提交
738 739 740 741
	}
	spin_unlock(&oldf->file_lock);

	/* compute the remainder to be cleared */
742
	size = (new_fdt->max_fds - open_files) * sizeof(struct file *);
L
Linus Torvalds 已提交
743

D
Daniel Walker 已提交
744 745
	/* This is long word aligned thus could use a optimized version */
	memset(new_fds, 0, size);
L
Linus Torvalds 已提交
746

747 748
	if (new_fdt->max_fds > open_files) {
		int left = (new_fdt->max_fds-open_files)/8;
L
Linus Torvalds 已提交
749 750
		int start = open_files / (8 * sizeof(unsigned long));

751 752
		memset(&new_fdt->open_fds->fds_bits[start], 0, left);
		memset(&new_fdt->close_on_exec->fds_bits[start], 0, left);
L
Linus Torvalds 已提交
753 754
	}

755
	return newf;
L
Linus Torvalds 已提交
756 757 758

out_release:
	kmem_cache_free(files_cachep, newf);
759
out:
760
	return NULL;
L
Linus Torvalds 已提交
761 762
}

763 764 765 766 767 768 769 770 771 772 773 774 775 776 777 778 779 780 781 782 783 784 785 786 787 788 789 790 791 792 793 794 795
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;
}

796
static int copy_io(unsigned long clone_flags, struct task_struct *tsk)
797 798 799 800 801 802
{
#ifdef CONFIG_BLOCK
	struct io_context *ioc = current->io_context;

	if (!ioc)
		return 0;
803 804 805 806 807 808 809 810
	/*
	 * Share io context with parent, if CLONE_IO is set
	 */
	if (clone_flags & CLONE_IO) {
		tsk->io_context = ioc_task_link(ioc);
		if (unlikely(!tsk->io_context))
			return -ENOMEM;
	} else if (ioprio_valid(ioc->ioprio)) {
811 812 813 814 815 816 817 818 819 820
		tsk->io_context = alloc_io_context(GFP_KERNEL, -1);
		if (unlikely(!tsk->io_context))
			return -ENOMEM;

		tsk->io_context->ioprio = ioc->ioprio;
	}
#endif
	return 0;
}

L
Linus Torvalds 已提交
821 822 823 824 825 826 827 828 829 830 831
/*
 *	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;

832
	BUG_ON(!files);
L
Linus Torvalds 已提交
833 834 835 836 837 838 839 840 841 842 843 844 845 846 847 848

	/* 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);

A
Alexey Dobriyan 已提交
849
static int copy_sighand(unsigned long clone_flags, struct task_struct *tsk)
L
Linus Torvalds 已提交
850 851 852 853 854 855 856 857
{
	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);
I
Ingo Molnar 已提交
858
	rcu_assign_pointer(tsk->sighand, sig);
L
Linus Torvalds 已提交
859 860 861 862 863 864 865
	if (!sig)
		return -ENOMEM;
	atomic_set(&sig->count, 1);
	memcpy(sig->action, current->sighand->action, sizeof(sig->action));
	return 0;
}

866
void __cleanup_sighand(struct sighand_struct *sighand)
867 868 869 870 871
{
	if (atomic_dec_and_test(&sighand->count))
		kmem_cache_free(sighand_cachep, sighand);
}

A
Alexey Dobriyan 已提交
872
static int copy_signal(unsigned long clone_flags, struct task_struct *tsk)
L
Linus Torvalds 已提交
873 874 875 876 877 878 879 880 881 882 883 884 885 886 887 888 889 890 891 892 893 894 895 896 897 898 899 900 901 902 903
{
	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);

904
	hrtimer_init(&sig->real_timer, CLOCK_MONOTONIC, HRTIMER_MODE_REL);
905
	sig->it_real_incr.tv64 = 0;
L
Linus Torvalds 已提交
906
	sig->real_timer.function = it_real_fn;
907
	sig->tsk = tsk;
L
Linus Torvalds 已提交
908 909 910 911 912 913 914

	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 */
915
	sig->tty_old_pgrp = NULL;
L
Linus Torvalds 已提交
916 917

	sig->utime = sig->stime = sig->cutime = sig->cstime = cputime_zero;
918 919
	sig->gtime = cputime_zero;
	sig->cgtime = cputime_zero;
L
Linus Torvalds 已提交
920 921
	sig->nvcsw = sig->nivcsw = sig->cnvcsw = sig->cnivcsw = 0;
	sig->min_flt = sig->maj_flt = sig->cmin_flt = sig->cmaj_flt = 0;
922
	sig->inblock = sig->oublock = sig->cinblock = sig->coublock = 0;
923
	sig->sum_sched_runtime = 0;
L
Linus Torvalds 已提交
924 925 926
	INIT_LIST_HEAD(&sig->cpu_timers[0]);
	INIT_LIST_HEAD(&sig->cpu_timers[1]);
	INIT_LIST_HEAD(&sig->cpu_timers[2]);
927
	taskstats_tgid_init(sig);
L
Linus Torvalds 已提交
928 929 930 931 932 933 934 935 936 937 938 939 940

	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);
	}
941
	acct_init_pacct(&sig->pacct);
L
Linus Torvalds 已提交
942

M
Miloslav Trmac 已提交
943 944
	tty_audit_fork(sig);

L
Linus Torvalds 已提交
945 946 947
	return 0;
}

948 949 950 951 952 953
void __cleanup_signal(struct signal_struct *sig)
{
	exit_thread_group_keys(sig);
	kmem_cache_free(signal_cachep, sig);
}

A
Alexey Dobriyan 已提交
954
static void cleanup_signal(struct task_struct *tsk)
955 956 957 958 959 960 961 962 963
{
	struct signal_struct *sig = tsk->signal;

	atomic_dec(&sig->live);

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

A
Alexey Dobriyan 已提交
964
static void copy_flags(unsigned long clone_flags, struct task_struct *p)
L
Linus Torvalds 已提交
965 966 967
{
	unsigned long new_flags = p->flags;

968
	new_flags &= ~PF_SUPERPRIV;
L
Linus Torvalds 已提交
969 970 971 972
	new_flags |= PF_FORKNOEXEC;
	if (!(clone_flags & CLONE_PTRACE))
		p->ptrace = 0;
	p->flags = new_flags;
973
	clear_freeze_flag(p);
L
Linus Torvalds 已提交
974 975 976 977 978 979
}

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

980
	return task_pid_vnr(current);
L
Linus Torvalds 已提交
981 982
}

A
Alexey Dobriyan 已提交
983
static void rt_mutex_init_task(struct task_struct *p)
I
Ingo Molnar 已提交
984 985
{
	spin_lock_init(&p->pi_lock);
986
#ifdef CONFIG_RT_MUTEXES
I
Ingo Molnar 已提交
987 988 989 990 991
	plist_head_init(&p->pi_waiters, &p->pi_lock);
	p->pi_blocked_on = NULL;
#endif
}

L
Linus Torvalds 已提交
992 993 994 995 996 997 998 999
/*
 * 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.
 */
1000 1001 1002 1003 1004
static struct task_struct *copy_process(unsigned long clone_flags,
					unsigned long stack_start,
					struct pt_regs *regs,
					unsigned long stack_size,
					int __user *child_tidptr,
1005
					struct pid *pid)
L
Linus Torvalds 已提交
1006 1007
{
	int retval;
1008
	struct task_struct *p;
1009
	int cgroup_callbacks_done = 0;
L
Linus Torvalds 已提交
1010 1011 1012 1013 1014 1015 1016 1017 1018 1019 1020 1021 1022 1023 1024 1025 1026 1027 1028 1029 1030 1031 1032 1033 1034 1035 1036 1037

	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;

1038 1039
	rt_mutex_init_task(p);

1040 1041 1042 1043
#ifdef CONFIG_TRACE_IRQFLAGS
	DEBUG_LOCKS_WARN_ON(!p->hardirqs_enabled);
	DEBUG_LOCKS_WARN_ON(!p->softirqs_enabled);
#endif
L
Linus Torvalds 已提交
1044 1045 1046 1047
	retval = -EAGAIN;
	if (atomic_read(&p->user->processes) >=
			p->signal->rlim[RLIMIT_NPROC].rlim_cur) {
		if (!capable(CAP_SYS_ADMIN) && !capable(CAP_SYS_RESOURCE) &&
1048
		    p->user != current->nsproxy->user_ns->root_user)
L
Linus Torvalds 已提交
1049 1050 1051 1052 1053 1054 1055 1056 1057 1058 1059 1060 1061 1062 1063
			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;

A
Al Viro 已提交
1064
	if (!try_module_get(task_thread_info(p)->exec_domain->module))
L
Linus Torvalds 已提交
1065 1066 1067 1068 1069 1070
		goto bad_fork_cleanup_count;

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

	p->did_exec = 0;
1071
	delayacct_tsk_init(p);	/* Must remain after dup_task_struct() */
L
Linus Torvalds 已提交
1072 1073 1074
	copy_flags(clone_flags, p);
	INIT_LIST_HEAD(&p->children);
	INIT_LIST_HEAD(&p->sibling);
P
Paul E. McKenney 已提交
1075 1076 1077 1078
#ifdef CONFIG_PREEMPT_RCU
	p->rcu_read_lock_nesting = 0;
	p->rcu_flipctr_idx = 0;
#endif /* #ifdef CONFIG_PREEMPT_RCU */
L
Linus Torvalds 已提交
1079 1080 1081 1082 1083 1084 1085 1086
	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;
1087
	p->gtime = cputime_zero;
1088 1089
	p->utimescaled = cputime_zero;
	p->stimescaled = cputime_zero;
P
Peter Zijlstra 已提交
1090
	p->prev_utime = cputime_zero;
1091
	p->prev_stime = cputime_zero;
1092

1093 1094 1095 1096 1097
#ifdef CONFIG_DETECT_SOFTLOCKUP
	p->last_switch_count = 0;
	p->last_switch_timestamp = 0;
#endif

1098
#ifdef CONFIG_TASK_XACCT
L
Linus Torvalds 已提交
1099 1100 1101 1102
	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 */
1103
#endif
1104
	task_io_accounting_init(p);
L
Linus Torvalds 已提交
1105 1106
	acct_clear_integrals(p);

D
Daniel Walker 已提交
1107
	p->it_virt_expires = cputime_zero;
L
Linus Torvalds 已提交
1108
	p->it_prof_expires = cputime_zero;
D
Daniel Walker 已提交
1109 1110 1111 1112
	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]);
L
Linus Torvalds 已提交
1113 1114 1115

	p->lock_depth = -1;		/* -1 = no lock */
	do_posix_clock_monotonic_gettime(&p->start_time);
1116 1117
	p->real_start_time = p->start_time;
	monotonic_to_bootbased(&p->real_start_time);
1118
#ifdef CONFIG_SECURITY
L
Linus Torvalds 已提交
1119
	p->security = NULL;
1120
#endif
1121
	p->cap_bset = current->cap_bset;
L
Linus Torvalds 已提交
1122 1123
	p->io_context = NULL;
	p->audit_context = NULL;
1124
	cgroup_fork(p);
L
Linus Torvalds 已提交
1125 1126 1127 1128 1129
#ifdef CONFIG_NUMA
 	p->mempolicy = mpol_copy(p->mempolicy);
 	if (IS_ERR(p->mempolicy)) {
 		retval = PTR_ERR(p->mempolicy);
 		p->mempolicy = NULL;
1130
 		goto bad_fork_cleanup_cgroup;
L
Linus Torvalds 已提交
1131
 	}
1132
	mpol_fix_fork_child_flag(p);
L
Linus Torvalds 已提交
1133
#endif
1134 1135
#ifdef CONFIG_TRACE_IRQFLAGS
	p->irq_events = 0;
1136 1137 1138
#ifdef __ARCH_WANT_INTERRUPTS_ON_CTXSW
	p->hardirqs_enabled = 1;
#else
1139
	p->hardirqs_enabled = 0;
1140
#endif
1141 1142 1143 1144 1145 1146 1147 1148 1149 1150 1151 1152
	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
I
Ingo Molnar 已提交
1153 1154 1155 1156 1157
#ifdef CONFIG_LOCKDEP
	p->lockdep_depth = 0; /* no locks held yet */
	p->curr_chain_key = 0;
	p->lockdep_recursion = 0;
#endif
L
Linus Torvalds 已提交
1158

1159 1160 1161 1162
#ifdef CONFIG_DEBUG_MUTEXES
	p->blocked_on = NULL; /* not blocked yet */
#endif

1163 1164 1165
	/* Perform scheduler related setup. Assign this task to a CPU. */
	sched_fork(p, clone_flags);

L
Linus Torvalds 已提交
1166 1167 1168 1169 1170 1171 1172 1173 1174 1175 1176 1177 1178 1179 1180 1181 1182 1183 1184
	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;
S
Serge E. Hallyn 已提交
1185
	if ((retval = copy_namespaces(clone_flags, p)))
L
Linus Torvalds 已提交
1186
		goto bad_fork_cleanup_keys;
1187
	if ((retval = copy_io(clone_flags, p)))
1188
		goto bad_fork_cleanup_namespaces;
L
Linus Torvalds 已提交
1189 1190
	retval = copy_thread(0, clone_flags, stack_start, stack_size, p, regs);
	if (retval)
1191
		goto bad_fork_cleanup_io;
L
Linus Torvalds 已提交
1192

1193 1194 1195 1196
	if (pid != &init_struct_pid) {
		retval = -ENOMEM;
		pid = alloc_pid(task_active_pid_ns(p));
		if (!pid)
1197
			goto bad_fork_cleanup_io;
1198 1199 1200 1201 1202 1203

		if (clone_flags & CLONE_NEWPID) {
			retval = pid_ns_prepare_proc(task_active_pid_ns(p));
			if (retval < 0)
				goto bad_fork_free_pid;
		}
1204 1205 1206 1207 1208 1209 1210
	}

	p->pid = pid_nr(pid);
	p->tgid = p->pid;
	if (clone_flags & CLONE_THREAD)
		p->tgid = current->tgid;

L
Linus Torvalds 已提交
1211 1212 1213 1214 1215
	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;
1216
#ifdef CONFIG_FUTEX
1217 1218 1219 1220
	p->robust_list = NULL;
#ifdef CONFIG_COMPAT
	p->compat_robust_list = NULL;
#endif
1221 1222
	INIT_LIST_HEAD(&p->pi_state_list);
	p->pi_state_cache = NULL;
1223
#endif
1224 1225 1226 1227 1228 1229
	/*
	 * 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;

L
Linus Torvalds 已提交
1230 1231 1232 1233 1234
	/*
	 * Syscall tracing should be turned off in the child regardless
	 * of CLONE_PTRACE.
	 */
	clear_tsk_thread_flag(p, TIF_SYSCALL_TRACE);
1235 1236 1237
#ifdef TIF_SYSCALL_EMU
	clear_tsk_thread_flag(p, TIF_SYSCALL_EMU);
#endif
A
Arjan van de Ven 已提交
1238
	clear_all_latency_tracing(p);
L
Linus Torvalds 已提交
1239 1240 1241 1242 1243 1244 1245 1246 1247 1248 1249 1250 1251 1252 1253

	/* 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;
O
Oleg Nesterov 已提交
1254
	INIT_LIST_HEAD(&p->thread_group);
L
Linus Torvalds 已提交
1255 1256 1257
	INIT_LIST_HEAD(&p->ptrace_children);
	INIT_LIST_HEAD(&p->ptrace_list);

1258 1259 1260 1261 1262 1263
	/* Now that the task is set up, run cgroup callbacks if
	 * necessary. We need to run them before the task is visible
	 * on the tasklist. */
	cgroup_fork_callbacks(p);
	cgroup_callbacks_done = 1;

L
Linus Torvalds 已提交
1264 1265 1266 1267
	/* Need tasklist lock for parent etc handling! */
	write_lock_irq(&tasklist_lock);

	/*
N
Nick Piggin 已提交
1268 1269 1270 1271 1272 1273 1274
	 * 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.
L
Linus Torvalds 已提交
1275 1276
	 */
	p->cpus_allowed = current->cpus_allowed;
P
Peter Zijlstra 已提交
1277
	p->rt.nr_cpus_allowed = current->rt.nr_cpus_allowed;
1278 1279
	if (unlikely(!cpu_isset(task_cpu(p), p->cpus_allowed) ||
			!cpu_online(task_cpu(p))))
N
Nick Piggin 已提交
1280
		set_task_cpu(p, smp_processor_id());
L
Linus Torvalds 已提交
1281 1282 1283 1284 1285 1286 1287 1288

	/* 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;

1289
	spin_lock(&current->sighand->siglock);
1290 1291 1292 1293 1294 1295 1296 1297 1298

	/*
	 * 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).
 	 */
D
Daniel Walker 已提交
1299
	recalc_sigpending();
1300 1301 1302 1303
	if (signal_pending(current)) {
		spin_unlock(&current->sighand->siglock);
		write_unlock_irq(&tasklist_lock);
		retval = -ERESTARTNOINTR;
1304
		goto bad_fork_free_pid;
1305 1306
	}

L
Linus Torvalds 已提交
1307 1308
	if (clone_flags & CLONE_THREAD) {
		p->group_leader = current->group_leader;
O
Oleg Nesterov 已提交
1309
		list_add_tail_rcu(&p->thread_group, &p->group_leader->thread_group);
L
Linus Torvalds 已提交
1310 1311 1312 1313 1314 1315 1316 1317 1318 1319 1320 1321 1322 1323 1324 1325 1326

		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);
		}
	}

1327 1328 1329 1330 1331 1332
	if (likely(p->pid)) {
		add_parent(p);
		if (unlikely(p->ptrace & PT_PTRACED))
			__ptrace_link(p, current->parent);

		if (thread_group_leader(p)) {
E
Eric W. Biederman 已提交
1333
			if (clone_flags & CLONE_NEWPID)
1334
				p->nsproxy->pid_ns->child_reaper = p;
1335

E
Eric W. Biederman 已提交
1336 1337 1338 1339 1340
			p->signal->tty = current->signal->tty;
			set_task_pgrp(p, task_pgrp_nr(current));
			set_task_session(p, task_session_nr(current));
			attach_pid(p, PIDTYPE_PGID, task_pgrp(current));
			attach_pid(p, PIDTYPE_SID, task_session(current));
1341
			list_add_tail_rcu(&p->tasks, &init_task.tasks);
L
Linus Torvalds 已提交
1342
			__get_cpu_var(process_counts)++;
1343
		}
1344
		attach_pid(p, PIDTYPE_PID, pid);
1345
		nr_threads++;
L
Linus Torvalds 已提交
1346 1347 1348
	}

	total_forks++;
1349
	spin_unlock(&current->sighand->siglock);
L
Linus Torvalds 已提交
1350
	write_unlock_irq(&tasklist_lock);
1351
	proc_fork_connector(p);
1352
	cgroup_post_fork(p);
L
Linus Torvalds 已提交
1353 1354
	return p;

1355 1356 1357
bad_fork_free_pid:
	if (pid != &init_struct_pid)
		free_pid(pid);
1358 1359
bad_fork_cleanup_io:
	put_io_context(p->io_context);
S
Serge E. Hallyn 已提交
1360
bad_fork_cleanup_namespaces:
1361
	exit_task_namespaces(p);
L
Linus Torvalds 已提交
1362 1363 1364 1365 1366 1367
bad_fork_cleanup_keys:
	exit_keys(p);
bad_fork_cleanup_mm:
	if (p->mm)
		mmput(p->mm);
bad_fork_cleanup_signal:
1368
	cleanup_signal(p);
L
Linus Torvalds 已提交
1369
bad_fork_cleanup_sighand:
1370
	__cleanup_sighand(p->sighand);
L
Linus Torvalds 已提交
1371 1372 1373 1374 1375 1376 1377 1378 1379 1380 1381 1382 1383
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);
1384
bad_fork_cleanup_cgroup:
L
Linus Torvalds 已提交
1385
#endif
1386
	cgroup_exit(p, cgroup_callbacks_done);
1387
	delayacct_tsk_free(p);
L
Linus Torvalds 已提交
1388 1389 1390
	if (p->binfmt)
		module_put(p->binfmt->module);
bad_fork_cleanup_put_domain:
A
Al Viro 已提交
1391
	module_put(task_thread_info(p)->exec_domain->module);
L
Linus Torvalds 已提交
1392 1393 1394 1395 1396 1397
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);
1398 1399
fork_out:
	return ERR_PTR(retval);
L
Linus Torvalds 已提交
1400 1401
}

1402
noinline struct pt_regs * __devinit __attribute__((weak)) idle_regs(struct pt_regs *regs)
L
Linus Torvalds 已提交
1403 1404 1405 1406 1407
{
	memset(regs, 0, sizeof(struct pt_regs));
	return regs;
}

1408
struct task_struct * __cpuinit fork_idle(int cpu)
L
Linus Torvalds 已提交
1409
{
1410
	struct task_struct *task;
L
Linus Torvalds 已提交
1411 1412
	struct pt_regs regs;

1413
	task = copy_process(CLONE_VM, 0, idle_regs(&regs), 0, NULL,
1414
				&init_struct_pid);
1415 1416
	if (!IS_ERR(task))
		init_idle(task, cpu);
1417

L
Linus Torvalds 已提交
1418 1419 1420
	return task;
}

A
Alexey Dobriyan 已提交
1421
static int fork_traceflag(unsigned clone_flags)
L
Linus Torvalds 已提交
1422 1423 1424 1425 1426 1427 1428 1429 1430 1431 1432 1433 1434 1435 1436 1437 1438 1439 1440 1441 1442 1443 1444 1445 1446 1447 1448 1449 1450 1451
{
	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;
1452
	long nr;
L
Linus Torvalds 已提交
1453

1454 1455 1456 1457 1458 1459 1460 1461 1462 1463 1464 1465 1466 1467 1468 1469 1470
	/*
	 * We hope to recycle these flags after 2.6.26
	 */
	if (unlikely(clone_flags & CLONE_STOPPED)) {
		static int __read_mostly count = 100;

		if (count > 0 && printk_ratelimit()) {
			char comm[TASK_COMM_LEN];

			count--;
			printk(KERN_INFO "fork(): process `%s' used deprecated "
					"clone flags 0x%lx\n",
				get_task_comm(comm, current),
				clone_flags & CLONE_STOPPED);
		}
	}

L
Linus Torvalds 已提交
1471 1472 1473 1474 1475 1476
	if (unlikely(current->ptrace)) {
		trace = fork_traceflag (clone_flags);
		if (trace)
			clone_flags |= CLONE_PTRACE;
	}

1477
	p = copy_process(clone_flags, stack_start, regs, stack_size,
1478
			child_tidptr, NULL);
L
Linus Torvalds 已提交
1479 1480 1481 1482 1483 1484 1485
	/*
	 * 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;

1486 1487 1488 1489 1490 1491 1492 1493 1494 1495
		/*
		 * this is enough to call pid_nr_ns here, but this if
		 * improves optimisation of regular fork()
		 */
		nr = (clone_flags & CLONE_NEWPID) ?
			task_pid_nr_ns(p, current->nsproxy->pid_ns) :
				task_pid_vnr(p);

		if (clone_flags & CLONE_PARENT_SETTID)
			put_user(nr, parent_tidptr);
1496

L
Linus Torvalds 已提交
1497 1498 1499 1500 1501 1502 1503 1504 1505 1506 1507 1508 1509 1510 1511 1512 1513 1514 1515
		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)) {
1516
			current->ptrace_message = nr;
L
Linus Torvalds 已提交
1517 1518 1519 1520
			ptrace_notify ((trace << 8) | SIGTRAP);
		}

		if (clone_flags & CLONE_VFORK) {
R
Rafael J. Wysocki 已提交
1521
			freezer_do_not_count();
L
Linus Torvalds 已提交
1522
			wait_for_completion(&vfork);
R
Rafael J. Wysocki 已提交
1523
			freezer_count();
1524 1525
			if (unlikely (current->ptrace & PT_TRACE_VFORK_DONE)) {
				current->ptrace_message = nr;
L
Linus Torvalds 已提交
1526
				ptrace_notify ((PTRACE_EVENT_VFORK_DONE << 8) | SIGTRAP);
1527
			}
L
Linus Torvalds 已提交
1528 1529
		}
	} else {
1530
		nr = PTR_ERR(p);
L
Linus Torvalds 已提交
1531
	}
1532
	return nr;
L
Linus Torvalds 已提交
1533 1534
}

1535 1536 1537 1538
#ifndef ARCH_MIN_MMSTRUCT_ALIGN
#define ARCH_MIN_MMSTRUCT_ALIGN 0
#endif

1539
static void sighand_ctor(struct kmem_cache *cachep, void *data)
1540 1541 1542
{
	struct sighand_struct *sighand = data;

C
Christoph Lameter 已提交
1543
	spin_lock_init(&sighand->siglock);
D
Davide Libenzi 已提交
1544
	init_waitqueue_head(&sighand->signalfd_wqh);
1545 1546
}

L
Linus Torvalds 已提交
1547 1548 1549 1550
void __init proc_caches_init(void)
{
	sighand_cachep = kmem_cache_create("sighand_cache",
			sizeof(struct sighand_struct), 0,
1551
			SLAB_HWCACHE_ALIGN|SLAB_PANIC|SLAB_DESTROY_BY_RCU,
1552
			sighand_ctor);
L
Linus Torvalds 已提交
1553 1554
	signal_cachep = kmem_cache_create("signal_cache",
			sizeof(struct signal_struct), 0,
1555 1556
			SLAB_HWCACHE_ALIGN|SLAB_PANIC, NULL);
	files_cachep = kmem_cache_create("files_cache",
L
Linus Torvalds 已提交
1557
			sizeof(struct files_struct), 0,
1558 1559
			SLAB_HWCACHE_ALIGN|SLAB_PANIC, NULL);
	fs_cachep = kmem_cache_create("fs_cache",
L
Linus Torvalds 已提交
1560
			sizeof(struct fs_struct), 0,
1561
			SLAB_HWCACHE_ALIGN|SLAB_PANIC, NULL);
L
Linus Torvalds 已提交
1562 1563
	vm_area_cachep = kmem_cache_create("vm_area_struct",
			sizeof(struct vm_area_struct), 0,
1564
			SLAB_PANIC, NULL);
L
Linus Torvalds 已提交
1565
	mm_cachep = kmem_cache_create("mm_struct",
1566
			sizeof(struct mm_struct), ARCH_MIN_MMSTRUCT_ALIGN,
1567
			SLAB_HWCACHE_ALIGN|SLAB_PANIC, NULL);
L
Linus Torvalds 已提交
1568
}
1569 1570 1571 1572 1573

/*
 * Check constraints on flags passed to the unshare system call and
 * force unsharing of additional process context as appropriate.
 */
A
Alexey Dobriyan 已提交
1574
static void check_unshare_flags(unsigned long *flags_ptr)
1575 1576 1577 1578 1579 1580 1581 1582 1583 1584 1585 1586 1587 1588 1589 1590 1591 1592 1593 1594 1595 1596 1597 1598 1599 1600 1601 1602 1603 1604 1605 1606 1607 1608 1609 1610 1611 1612 1613 1614 1615
{
	/*
	 * 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;
}

/*
1616
 * Unshare the filesystem structure if it is being shared
1617 1618 1619 1620 1621 1622
 */
static int unshare_fs(unsigned long unshare_flags, struct fs_struct **new_fsp)
{
	struct fs_struct *fs = current->fs;

	if ((unshare_flags & CLONE_FS) &&
1623 1624 1625 1626 1627
	    (fs && atomic_read(&fs->count) > 1)) {
		*new_fsp = __copy_fs_struct(current->fs);
		if (!*new_fsp)
			return -ENOMEM;
	}
1628 1629 1630 1631 1632

	return 0;
}

/*
1633
 * Unsharing of sighand is not supported yet
1634 1635 1636 1637 1638
 */
static int unshare_sighand(unsigned long unshare_flags, struct sighand_struct **new_sighp)
{
	struct sighand_struct *sigh = current->sighand;

1639
	if ((unshare_flags & CLONE_SIGHAND) && atomic_read(&sigh->count) > 1)
1640 1641 1642 1643 1644 1645
		return -EINVAL;
	else
		return 0;
}

/*
1646
 * Unshare vm if it is being shared
1647 1648 1649 1650 1651 1652
 */
static int unshare_vm(unsigned long unshare_flags, struct mm_struct **new_mmp)
{
	struct mm_struct *mm = current->mm;

	if ((unshare_flags & CLONE_VM) &&
1653
	    (mm && atomic_read(&mm->mm_users) > 1)) {
1654
		return -EINVAL;
1655
	}
1656 1657 1658 1659 1660

	return 0;
}

/*
1661
 * Unshare file descriptor table if it is being shared
1662 1663 1664 1665
 */
static int unshare_fd(unsigned long unshare_flags, struct files_struct **new_fdp)
{
	struct files_struct *fd = current->files;
1666
	int error = 0;
1667 1668

	if ((unshare_flags & CLONE_FILES) &&
1669 1670 1671 1672 1673
	    (fd && atomic_read(&fd->count) > 1)) {
		*new_fdp = dup_fd(fd, &error);
		if (!*new_fdp)
			return error;
	}
1674 1675 1676 1677 1678 1679 1680 1681 1682 1683 1684 1685 1686 1687 1688 1689 1690 1691 1692 1693 1694 1695 1696 1697 1698 1699 1700 1701

	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;
1702
	struct sighand_struct *new_sigh = NULL;
1703 1704 1705
	struct mm_struct *mm, *new_mm = NULL, *active_mm = NULL;
	struct files_struct *fd, *new_fd = NULL;
	struct sem_undo_list *new_ulist = NULL;
1706
	struct nsproxy *new_nsproxy = NULL;
1707 1708 1709

	check_unshare_flags(&unshare_flags);

1710 1711 1712
	/* Return -EINVAL for all unsupported flags */
	err = -EINVAL;
	if (unshare_flags & ~(CLONE_THREAD|CLONE_FS|CLONE_NEWNS|CLONE_SIGHAND|
K
Kirill Korotaev 已提交
1713
				CLONE_VM|CLONE_FILES|CLONE_SYSVSEM|
1714 1715
				CLONE_NEWUTS|CLONE_NEWIPC|CLONE_NEWUSER|
				CLONE_NEWNET))
1716 1717
		goto bad_unshare_out;

1718 1719 1720 1721 1722
	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)))
1723
		goto bad_unshare_cleanup_fs;
1724 1725 1726 1727 1728 1729
	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;
1730 1731
	if ((err = unshare_nsproxy_namespaces(unshare_flags, &new_nsproxy,
			new_fs)))
1732
		goto bad_unshare_cleanup_semundo;
1733

1734
	if (new_fs ||  new_mm || new_fd || new_ulist || new_nsproxy) {
S
Serge E. Hallyn 已提交
1735

1736
		if (new_nsproxy) {
1737 1738
			switch_task_namespaces(current, new_nsproxy);
			new_nsproxy = NULL;
1739
		}
1740

1741 1742
		task_lock(current);

1743 1744 1745 1746 1747 1748 1749 1750 1751 1752 1753 1754 1755 1756 1757 1758 1759 1760 1761 1762 1763 1764 1765 1766
		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);
	}

1767
	if (new_nsproxy)
1768
		put_nsproxy(new_nsproxy);
1769

S
Serge E. Hallyn 已提交
1770
bad_unshare_cleanup_semundo:
1771 1772 1773 1774 1775 1776 1777 1778 1779 1780 1781 1782 1783 1784 1785 1786 1787 1788 1789 1790 1791
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;
}