fork.c 39.0 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/config.h>
#include <linux/slab.h>
#include <linux/init.h>
#include <linux/unistd.h>
#include <linux/smp_lock.h>
#include <linux/module.h>
#include <linux/vmalloc.h>
#include <linux/completion.h>
#include <linux/namespace.h>
#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/capability.h>
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#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>
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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/cn_proc.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;

 __cacheline_aligned DEFINE_RWLOCK(tasklist_lock);  /* outer */

EXPORT_SYMBOL(tasklist_lock);

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))
static kmem_cache_t *task_struct_cachep;
#endif

/* SLAB cache for signal_struct structures (tsk->signal) */
kmem_cache_t *signal_cachep;

/* SLAB cache for sighand_struct structures (tsk->sighand) */
kmem_cache_t *sighand_cachep;

/* SLAB cache for files_struct structures (tsk->files) */
kmem_cache_t *files_cachep;

/* SLAB cache for fs_struct structures (tsk->fs) */
kmem_cache_t *fs_cachep;

/* SLAB cache for vm_area_struct structures */
kmem_cache_t *vm_area_cachep;

/* SLAB cache for mm_struct structures (tsk->mm) */
static kmem_cache_t *mm_cachep;

void free_task(struct task_struct *tsk)
{
	free_thread_info(tsk->thread_info);
	free_task_struct(tsk);
}
EXPORT_SYMBOL(free_task);

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void __put_task_struct_cb(struct rcu_head *rhp)
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{
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	struct task_struct *tsk = container_of(rhp, struct task_struct, rcu);

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	WARN_ON(!(tsk->exit_state & (EXIT_DEAD | EXIT_ZOMBIE)));
	WARN_ON(atomic_read(&tsk->usage));
	WARN_ON(tsk == current);

	if (unlikely(tsk->audit_context))
		audit_free(tsk);
	security_task_free(tsk);
	free_uid(tsk->user);
	put_group_info(tsk->group_info);

	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;
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	setup_thread_stack(tsk, orig);
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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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	return tsk;
}

#ifdef CONFIG_MMU
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static inline 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_mm(oldmm);
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	down_write(&mm->mmap_sem);

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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;
		}
		tmp = kmem_cache_alloc(vm_area_cachep, SLAB_KERNEL);
		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) {
			struct inode *inode = file->f_dentry->d_inode;
			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);
		}

		/*
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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;
	}
	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)
{
	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);

#define allocate_mm()	(kmem_cache_alloc(mm_cachep, SLAB_KERNEL))
#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;
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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);
}

/*
 * Decrement the use count and release all resources for an mm.
 */
void mmput(struct mm_struct *mm)
{
	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);
	}
	if (tsk->clear_child_tid && atomic_read(&mm->mm_users) > 1) {
		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));

	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:
	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;
}

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static int count_open_files(struct fdtable *fdt)
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{
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	int size = fdt->max_fdset;
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	int i;

	/* Find the last open fd */
	for (i = size/(8*sizeof(long)); i > 0; ) {
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		if (fdt->open_fds->fds_bits[--i])
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			break;
	}
	i = (i+1) * 8 * sizeof(long);
	return i;
}

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static struct files_struct *alloc_files(void)
{
	struct files_struct *newf;
	struct fdtable *fdt;

	newf = kmem_cache_alloc(files_cachep, SLAB_KERNEL);
	if (!newf)
		goto out;

	atomic_set(&newf->count, 1);

	spin_lock_init(&newf->file_lock);
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	newf->next_fd = 0;
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	fdt = &newf->fdtab;
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	fdt->max_fds = NR_OPEN_DEFAULT;
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	fdt->max_fdset = EMBEDDED_FD_SET_SIZE;
	fdt->close_on_exec = (fd_set *)&newf->close_on_exec_init;
	fdt->open_fds = (fd_set *)&newf->open_fds_init;
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	fdt->fd = &newf->fd_array[0];
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	INIT_RCU_HEAD(&fdt->rcu);
	fdt->free_files = NULL;
	fdt->next = NULL;
	rcu_assign_pointer(newf->fdt, fdt);
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out:
	return newf;
}

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/*
 * Allocate a new files structure and copy contents from the
 * passed in files structure.
 */
static struct files_struct *dup_fd(struct files_struct *oldf, int *errorp)
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{
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	struct files_struct *newf;
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	struct file **old_fds, **new_fds;
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	int open_files, size, i, expand;
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	struct fdtable *old_fdt, *new_fdt;
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	newf = alloc_files();
	if (!newf)
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		goto out;

	spin_lock(&oldf->file_lock);
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	old_fdt = files_fdtable(oldf);
	new_fdt = files_fdtable(newf);
	size = old_fdt->max_fdset;
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	open_files = count_open_files(old_fdt);
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	expand = 0;

	/*
	 * Check whether we need to allocate a larger fd array or fd set.
	 * Note: we're not a clone task, so the open count won't  change.
	 */
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	if (open_files > new_fdt->max_fdset) {
		new_fdt->max_fdset = 0;
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		expand = 1;
	}
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	if (open_files > new_fdt->max_fds) {
		new_fdt->max_fds = 0;
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		expand = 1;
	}

	/* if the old fdset gets grown now, we'll only copy up to "size" fds */
	if (expand) {
		spin_unlock(&oldf->file_lock);
		spin_lock(&newf->file_lock);
664
		*errorp = expand_files(newf, open_files-1);
L
Linus Torvalds 已提交
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		spin_unlock(&newf->file_lock);
666
		if (*errorp < 0)
L
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			goto out_release;
668 669 670 671 672 673
		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
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		spin_lock(&oldf->file_lock);
675
		old_fdt = files_fdtable(oldf);
L
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	}

678 679
	old_fds = old_fdt->fd;
	new_fds = new_fdt->fd;
L
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681 682
	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);
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	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.
			 */
695
			FD_CLR(open_files - i, new_fdt->open_fds);
L
Linus Torvalds 已提交
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		}
697
		rcu_assign_pointer(*new_fds++, f);
L
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	}
	spin_unlock(&oldf->file_lock);

	/* compute the remainder to be cleared */
702
	size = (new_fdt->max_fds - open_files) * sizeof(struct file *);
L
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	/* This is long word aligned thus could use a optimized version */ 
	memset(new_fds, 0, size); 

707 708
	if (new_fdt->max_fdset > open_files) {
		int left = (new_fdt->max_fdset-open_files)/8;
L
Linus Torvalds 已提交
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		int start = open_files / (8 * sizeof(unsigned long));

711 712
		memset(&new_fdt->open_fds->fds_bits[start], 0, left);
		memset(&new_fdt->close_on_exec->fds_bits[start], 0, left);
L
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	}

out:
716
	return newf;
L
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out_release:
719 720 721
	free_fdset (new_fdt->close_on_exec, new_fdt->max_fdset);
	free_fdset (new_fdt->open_fds, new_fdt->max_fdset);
	free_fd_array(new_fdt->fd, new_fdt->max_fds);
L
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	kmem_cache_free(files_cachep, newf);
	goto out;
}

726 727 728 729 730 731 732 733 734 735 736 737 738 739 740 741 742 743 744 745 746 747 748 749 750 751 752 753 754 755 756 757 758 759
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;
	error = -ENOMEM;
	newf = dup_fd(oldf, &error);
	if (!newf)
		goto out;

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

L
Linus Torvalds 已提交
760 761 762 763 764 765 766 767 768 769 770 771 772 773 774 775 776 777 778 779 780 781 782 783 784 785 786 787 788
/*
 *	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;

	if(!files)
		BUG();

	/* 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);

I
Ingo Molnar 已提交
789 790 791 792 793 794 795 796
void sighand_free_cb(struct rcu_head *rhp)
{
	struct sighand_struct *sp;

	sp = container_of(rhp, struct sighand_struct, rcu);
	kmem_cache_free(sighand_cachep, sp);
}

L
Linus Torvalds 已提交
797 798 799 800 801 802 803 804 805
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);
I
Ingo Molnar 已提交
806
	rcu_assign_pointer(tsk->sighand, sig);
L
Linus Torvalds 已提交
807 808 809 810 811 812 813 814 815 816 817 818 819 820 821 822 823 824 825 826 827 828 829 830 831 832 833 834 835 836 837 838 839 840 841 842 843 844 845 846
	if (!sig)
		return -ENOMEM;
	spin_lock_init(&sig->siglock);
	atomic_set(&sig->count, 1);
	memcpy(sig->action, current->sighand->action, sizeof(sig->action));
	return 0;
}

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);

847
	hrtimer_init(&sig->real_timer, CLOCK_MONOTONIC, HRTIMER_REL);
848
	sig->it_real_incr.tv64 = 0;
L
Linus Torvalds 已提交
849
	sig->real_timer.function = it_real_fn;
850
	sig->real_timer.data = tsk;
L
Linus Torvalds 已提交
851 852 853 854 855 856 857 858 859 860 861 862 863 864 865 866 867 868 869 870 871 872 873 874 875 876 877 878 879 880 881 882 883 884 885 886 887

	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 */
	sig->tty_old_pgrp = 0;

	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]);

	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);
	}

	return 0;
}

static inline void copy_flags(unsigned long clone_flags, struct task_struct *p)
{
	unsigned long new_flags = p->flags;

888
	new_flags &= ~(PF_SUPERPRIV | PF_NOFREEZE);
L
Linus Torvalds 已提交
889 890 891 892 893 894 895 896 897 898 899 900 901 902 903 904 905 906 907 908 909 910 911 912 913 914 915 916 917 918 919 920 921 922 923 924 925 926 927 928 929 930 931 932 933 934 935 936 937 938 939 940 941 942 943 944 945 946 947 948 949 950 951 952 953 954 955 956 957 958 959 960 961 962 963 964 965 966 967
	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;
}

/*
 * 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.
 */
static task_t *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)
{
	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;

	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;

A
Al Viro 已提交
968
	if (!try_module_get(task_thread_info(p)->exec_domain->module))
L
Linus Torvalds 已提交
969 970 971 972 973 974 975 976 977 978 979 980 981 982 983 984 985 986 987 988 989 990 991 992 993 994 995 996 997 998 999 1000 1001 1002 1003 1004 1005 1006 1007 1008 1009 1010 1011 1012 1013 1014
		goto bad_fork_cleanup_count;

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

	p->did_exec = 0;
	copy_flags(clone_flags, p);
	p->pid = pid;
	retval = -EFAULT;
	if (clone_flags & CLONE_PARENT_SETTID)
		if (put_user(p->pid, parent_tidptr))
			goto bad_fork_cleanup;

	p->proc_dentry = NULL;

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

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

	p->utime = cputime_zero;
	p->stime = cputime_zero;
 	p->sched_time = 0;
	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 */
	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;
P
Paul Jackson 已提交
1015
	cpuset_fork(p);
L
Linus Torvalds 已提交
1016 1017 1018 1019 1020
#ifdef CONFIG_NUMA
 	p->mempolicy = mpol_copy(p->mempolicy);
 	if (IS_ERR(p->mempolicy)) {
 		retval = PTR_ERR(p->mempolicy);
 		p->mempolicy = NULL;
P
Paul Jackson 已提交
1021
 		goto bad_fork_cleanup_cpuset;
L
Linus Torvalds 已提交
1022 1023 1024
 	}
#endif

1025 1026 1027 1028
#ifdef CONFIG_DEBUG_MUTEXES
	p->blocked_on = NULL; /* not blocked yet */
#endif

L
Linus Torvalds 已提交
1029 1030 1031 1032 1033 1034 1035 1036 1037 1038 1039 1040 1041 1042 1043 1044 1045 1046 1047 1048 1049 1050 1051 1052 1053 1054 1055 1056 1057 1058 1059 1060 1061 1062 1063
	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;
	if ((retval = copy_namespace(clone_flags, p)))
		goto bad_fork_cleanup_keys;
	retval = copy_thread(0, clone_flags, stack_start, stack_size, p, regs);
	if (retval)
		goto bad_fork_cleanup_namespace;

	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;

1064 1065 1066 1067 1068 1069
	/*
	 * 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
1070 1071 1072 1073 1074
	/*
	 * Syscall tracing should be turned off in the child regardless
	 * of CLONE_PTRACE.
	 */
	clear_tsk_thread_flag(p, TIF_SYSCALL_TRACE);
1075 1076 1077
#ifdef TIF_SYSCALL_EMU
	clear_tsk_thread_flag(p, TIF_SYSCALL_EMU);
#endif
L
Linus Torvalds 已提交
1078 1079 1080 1081 1082 1083 1084 1085 1086 1087 1088 1089 1090 1091 1092 1093 1094 1095 1096

	/* 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;
	INIT_LIST_HEAD(&p->ptrace_children);
	INIT_LIST_HEAD(&p->ptrace_list);

N
Nick Piggin 已提交
1097 1098 1099
	/* Perform scheduler related setup. Assign this task to a CPU. */
	sched_fork(p, clone_flags);

L
Linus Torvalds 已提交
1100 1101 1102 1103
	/* Need tasklist lock for parent etc handling! */
	write_lock_irq(&tasklist_lock);

	/*
N
Nick Piggin 已提交
1104 1105 1106 1107 1108 1109 1110
	 * 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
1111 1112
	 */
	p->cpus_allowed = current->cpus_allowed;
1113 1114
	if (unlikely(!cpu_isset(task_cpu(p), p->cpus_allowed) ||
			!cpu_online(task_cpu(p))))
N
Nick Piggin 已提交
1115
		set_task_cpu(p, smp_processor_id());
L
Linus Torvalds 已提交
1116 1117 1118 1119 1120 1121 1122 1123 1124 1125 1126 1127 1128 1129 1130 1131 1132 1133

	/*
	 * Check for pending SIGKILL! The new thread should not be allowed
	 * to slip out of an OOM kill. (or normal SIGKILL.)
	 */
	if (sigismember(&current->pending.signal, SIGKILL)) {
		write_unlock_irq(&tasklist_lock);
		retval = -EINTR;
		goto bad_fork_cleanup_namespace;
	}

	/* 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;

1134
	spin_lock(&current->sighand->siglock);
L
Linus Torvalds 已提交
1135 1136 1137 1138 1139 1140 1141 1142 1143 1144 1145 1146 1147 1148 1149 1150 1151 1152 1153 1154 1155 1156 1157 1158 1159 1160 1161 1162 1163 1164 1165 1166 1167 1168 1169 1170 1171 1172 1173 1174
	if (clone_flags & CLONE_THREAD) {
		/*
		 * Important: if an exit-all has been started then
		 * do not create this new thread - the whole thread
		 * group is supposed to exit anyway.
		 */
		if (current->signal->flags & SIGNAL_GROUP_EXIT) {
			spin_unlock(&current->sighand->siglock);
			write_unlock_irq(&tasklist_lock);
			retval = -EAGAIN;
			goto bad_fork_cleanup_namespace;
		}
		p->group_leader = current->group_leader;

		if (current->signal->group_stop_count > 0) {
			/*
			 * There is an all-stop in progress for the group.
			 * We ourselves will stop as soon as we check signals.
			 * Make the new thread part of that group stop too.
			 */
			current->signal->group_stop_count++;
			set_tsk_thread_flag(p, TIF_SIGPENDING);
		}

		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);
		}
	}

1175 1176 1177 1178 1179
	/*
	 * inherit ioprio
	 */
	p->ioprio = current->ioprio;

L
Linus Torvalds 已提交
1180 1181 1182 1183 1184
	SET_LINKS(p);
	if (unlikely(p->ptrace & PT_PTRACED))
		__ptrace_link(p, current->parent);

	if (thread_group_leader(p)) {
1185 1186 1187
		p->signal->tty = current->signal->tty;
		p->signal->pgrp = process_group(current);
		p->signal->session = current->signal->session;
L
Linus Torvalds 已提交
1188 1189 1190 1191 1192
		attach_pid(p, PIDTYPE_PGID, process_group(p));
		attach_pid(p, PIDTYPE_SID, p->signal->session);
		if (p->pid)
			__get_cpu_var(process_counts)++;
	}
1193 1194
	attach_pid(p, PIDTYPE_TGID, p->tgid);
	attach_pid(p, PIDTYPE_PID, p->pid);
L
Linus Torvalds 已提交
1195 1196 1197

	nr_threads++;
	total_forks++;
1198
	spin_unlock(&current->sighand->siglock);
L
Linus Torvalds 已提交
1199
	write_unlock_irq(&tasklist_lock);
1200
	proc_fork_connector(p);
L
Linus Torvalds 已提交
1201 1202 1203 1204 1205 1206 1207 1208 1209 1210 1211 1212 1213 1214 1215 1216 1217 1218 1219 1220 1221 1222 1223 1224 1225 1226
	return p;

bad_fork_cleanup_namespace:
	exit_namespace(p);
bad_fork_cleanup_keys:
	exit_keys(p);
bad_fork_cleanup_mm:
	if (p->mm)
		mmput(p->mm);
bad_fork_cleanup_signal:
	exit_signal(p);
bad_fork_cleanup_sighand:
	exit_sighand(p);
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);
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bad_fork_cleanup_cpuset:
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#endif
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	cpuset_exit(p);
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bad_fork_cleanup:
	if (p->binfmt)
		module_put(p->binfmt->module);
bad_fork_cleanup_put_domain:
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	module_put(task_thread_info(p)->exec_domain->module);
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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);
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fork_out:
	return ERR_PTR(retval);
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}

struct pt_regs * __devinit __attribute__((weak)) idle_regs(struct pt_regs *regs)
{
	memset(regs, 0, sizeof(struct pt_regs));
	return regs;
}

task_t * __devinit fork_idle(int cpu)
{
	task_t *task;
	struct pt_regs regs;

	task = copy_process(CLONE_VM, 0, idle_regs(&regs), 0, NULL, NULL, 0);
	if (!task)
		return ERR_PTR(-ENOMEM);
	init_idle(task, cpu);
	unhash_process(task);
	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;
	long pid = alloc_pidmap();

	if (pid < 0)
		return -EAGAIN;
	if (unlikely(current->ptrace)) {
		trace = fork_traceflag (clone_flags);
		if (trace)
			clone_flags |= CLONE_PTRACE;
	}

	p = copy_process(clone_flags, stack_start, regs, stack_size, parent_tidptr, child_tidptr, pid);
	/*
	 * 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)) {
			current->ptrace_message = pid;
			ptrace_notify ((trace << 8) | SIGTRAP);
		}

		if (clone_flags & CLONE_VFORK) {
			wait_for_completion(&vfork);
			if (unlikely (current->ptrace & PT_TRACE_VFORK_DONE))
				ptrace_notify ((PTRACE_EVENT_VFORK_DONE << 8) | SIGTRAP);
		}
	} else {
		free_pidmap(pid);
		pid = PTR_ERR(p);
	}
	return pid;
}

1348 1349 1350 1351
#ifndef ARCH_MIN_MMSTRUCT_ALIGN
#define ARCH_MIN_MMSTRUCT_ALIGN 0
#endif

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void __init proc_caches_init(void)
{
	sighand_cachep = kmem_cache_create("sighand_cache",
			sizeof(struct sighand_struct), 0,
			SLAB_HWCACHE_ALIGN|SLAB_PANIC, NULL, NULL);
	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",
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			sizeof(struct mm_struct), ARCH_MIN_MMSTRUCT_ALIGN,
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			SLAB_HWCACHE_ALIGN|SLAB_PANIC, NULL, NULL);
}
1373 1374 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 1401 1402 1403 1404 1405 1406 1407 1408 1409 1410 1411 1412 1413 1414 1415 1416 1417 1418 1419 1420


/*
 * 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;
}

/*
1421
 * Unshare the filesystem structure if it is being shared
1422 1423 1424 1425 1426 1427
 */
static int unshare_fs(unsigned long unshare_flags, struct fs_struct **new_fsp)
{
	struct fs_struct *fs = current->fs;

	if ((unshare_flags & CLONE_FS) &&
1428 1429 1430 1431 1432
	    (fs && atomic_read(&fs->count) > 1)) {
		*new_fsp = __copy_fs_struct(current->fs);
		if (!*new_fsp)
			return -ENOMEM;
	}
1433 1434 1435 1436 1437

	return 0;
}

/*
1438
 * Unshare the namespace structure if it is being shared
1439
 */
1440
static int unshare_namespace(unsigned long unshare_flags, struct namespace **new_nsp, struct fs_struct *new_fs)
1441 1442 1443 1444
{
	struct namespace *ns = current->namespace;

	if ((unshare_flags & CLONE_NEWNS) &&
1445 1446 1447 1448 1449 1450 1451 1452
	    (ns && atomic_read(&ns->count) > 1)) {
		if (!capable(CAP_SYS_ADMIN))
			return -EPERM;

		*new_nsp = dup_namespace(current, new_fs ? new_fs : current->fs);
		if (!*new_nsp)
			return -ENOMEM;
	}
1453 1454 1455 1456 1457 1458 1459 1460 1461 1462 1463 1464 1465 1466 1467 1468 1469 1470 1471 1472

	return 0;
}

/*
 * Unsharing of sighand for tasks created with CLONE_SIGHAND is not
 * supported yet
 */
static int unshare_sighand(unsigned long unshare_flags, struct sighand_struct **new_sighp)
{
	struct sighand_struct *sigh = current->sighand;

	if ((unshare_flags & CLONE_SIGHAND) &&
	    (sigh && atomic_read(&sigh->count) > 1))
		return -EINVAL;
	else
		return 0;
}

/*
1473
 * Unshare vm if it is being shared
1474 1475 1476 1477 1478 1479
 */
static int unshare_vm(unsigned long unshare_flags, struct mm_struct **new_mmp)
{
	struct mm_struct *mm = current->mm;

	if ((unshare_flags & CLONE_VM) &&
1480
	    (mm && atomic_read(&mm->mm_users) > 1)) {
1481
		return -EINVAL;
1482
	}
1483 1484 1485 1486 1487

	return 0;
}

/*
1488
 * Unshare file descriptor table if it is being shared
1489 1490 1491 1492
 */
static int unshare_fd(unsigned long unshare_flags, struct files_struct **new_fdp)
{
	struct files_struct *fd = current->files;
1493
	int error = 0;
1494 1495

	if ((unshare_flags & CLONE_FILES) &&
1496 1497 1498 1499 1500
	    (fd && atomic_read(&fd->count) > 1)) {
		*new_fdp = dup_fd(fd, &error);
		if (!*new_fdp)
			return error;
	}
1501 1502 1503 1504 1505 1506 1507 1508 1509 1510 1511 1512 1513 1514 1515 1516 1517 1518 1519 1520 1521 1522 1523 1524 1525 1526 1527 1528 1529 1530 1531 1532 1533 1534 1535 1536

	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;
	struct namespace *ns, *new_ns = NULL;
	struct sighand_struct *sigh, *new_sigh = NULL;
	struct mm_struct *mm, *new_mm = NULL, *active_mm = NULL;
	struct files_struct *fd, *new_fd = NULL;
	struct sem_undo_list *new_ulist = NULL;

	check_unshare_flags(&unshare_flags);

1537 1538 1539 1540 1541 1542
	/* Return -EINVAL for all unsupported flags */
	err = -EINVAL;
	if (unshare_flags & ~(CLONE_THREAD|CLONE_FS|CLONE_NEWNS|CLONE_SIGHAND|
				CLONE_VM|CLONE_FILES|CLONE_SYSVSEM))
		goto bad_unshare_out;

1543 1544 1545 1546
	if ((err = unshare_thread(unshare_flags)))
		goto bad_unshare_out;
	if ((err = unshare_fs(unshare_flags, &new_fs)))
		goto bad_unshare_cleanup_thread;
1547
	if ((err = unshare_namespace(unshare_flags, &new_ns, new_fs)))
1548 1549 1550 1551 1552 1553 1554 1555 1556 1557 1558 1559 1560 1561 1562 1563 1564 1565 1566 1567 1568 1569 1570 1571 1572 1573 1574 1575
		goto bad_unshare_cleanup_fs;
	if ((err = unshare_sighand(unshare_flags, &new_sigh)))
		goto bad_unshare_cleanup_ns;
	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;

	if (new_fs || new_ns || new_sigh || new_mm || new_fd || new_ulist) {

		task_lock(current);

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

		if (new_ns) {
			ns = current->namespace;
			current->namespace = new_ns;
			new_ns = ns;
		}

		if (new_sigh) {
			sigh = current->sighand;
1576
			rcu_assign_pointer(current->sighand, new_sigh);
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 1616 1617 1618 1619 1620 1621 1622
			new_sigh = sigh;
		}

		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);
	}

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_ns:
	if (new_ns)
		put_namespace(new_ns);

bad_unshare_cleanup_fs:
	if (new_fs)
		put_fs_struct(new_fs);

bad_unshare_cleanup_thread:
bad_unshare_out:
	return err;
}