4 * Copyright (C) 1991, 1992 Linus Torvalds
8 * 'fork.c' contains the help-routines for the 'fork' system call
9 * (see also entry.S and others).
10 * Fork is rather simple, once you get the hang of it, but the memory
11 * management can be a bitch. See 'mm/memory.c': 'copy_page_range()'
14 #include <linux/slab.h>
15 #include <linux/init.h>
16 #include <linux/unistd.h>
17 #include <linux/module.h>
18 #include <linux/vmalloc.h>
19 #include <linux/completion.h>
20 #include <linux/personality.h>
21 #include <linux/mempolicy.h>
22 #include <linux/sem.h>
23 #include <linux/file.h>
24 #include <linux/fdtable.h>
25 #include <linux/iocontext.h>
26 #include <linux/key.h>
27 #include <linux/binfmts.h>
28 #include <linux/mman.h>
29 #include <linux/mmu_notifier.h>
31 #include <linux/nsproxy.h>
32 #include <linux/capability.h>
33 #include <linux/cpu.h>
34 #include <linux/cgroup.h>
35 #include <linux/security.h>
36 #include <linux/hugetlb.h>
37 #include <linux/swap.h>
38 #include <linux/syscalls.h>
39 #include <linux/jiffies.h>
40 #include <linux/futex.h>
41 #include <linux/compat.h>
42 #include <linux/kthread.h>
43 #include <linux/task_io_accounting_ops.h>
44 #include <linux/rcupdate.h>
45 #include <linux/ptrace.h>
46 #include <linux/mount.h>
47 #include <linux/audit.h>
48 #include <linux/memcontrol.h>
49 #include <linux/ftrace.h>
50 #include <linux/proc_fs.h>
51 #include <linux/profile.h>
52 #include <linux/rmap.h>
53 #include <linux/ksm.h>
54 #include <linux/acct.h>
55 #include <linux/tsacct_kern.h>
56 #include <linux/cn_proc.h>
57 #include <linux/freezer.h>
58 #include <linux/delayacct.h>
59 #include <linux/taskstats_kern.h>
60 #include <linux/random.h>
61 #include <linux/tty.h>
62 #include <linux/blkdev.h>
63 #include <linux/fs_struct.h>
64 #include <linux/magic.h>
65 #include <linux/perf_event.h>
66 #include <linux/posix-timers.h>
67 #include <linux/user-return-notifier.h>
68 #include <linux/oom.h>
69 #include <linux/khugepaged.h>
70 #include <linux/signalfd.h>
72 #include <asm/pgtable.h>
73 #include <asm/pgalloc.h>
74 #include <asm/uaccess.h>
75 #include <asm/mmu_context.h>
76 #include <asm/cacheflush.h>
77 #include <asm/tlbflush.h>
79 #include <trace/events/sched.h>
81 #define CREATE_TRACE_POINTS
82 #include <trace/events/task.h>
85 * Protected counters by write_lock_irq(&tasklist_lock)
87 unsigned long total_forks; /* Handle normal Linux uptimes. */
88 int nr_threads; /* The idle threads do not count.. */
90 int max_threads; /* tunable limit on nr_threads */
92 DEFINE_PER_CPU(unsigned long, process_counts) = 0;
94 __cacheline_aligned DEFINE_RWLOCK(tasklist_lock); /* outer */
96 #ifdef CONFIG_PROVE_RCU
97 int lockdep_tasklist_lock_is_held(void)
99 return lockdep_is_held(&tasklist_lock);
101 EXPORT_SYMBOL_GPL(lockdep_tasklist_lock_is_held);
102 #endif /* #ifdef CONFIG_PROVE_RCU */
104 int nr_processes(void)
109 for_each_possible_cpu(cpu)
110 total += per_cpu(process_counts, cpu);
115 #ifndef __HAVE_ARCH_TASK_STRUCT_ALLOCATOR
116 # define alloc_task_struct_node(node) \
117 kmem_cache_alloc_node(task_struct_cachep, GFP_KERNEL, node)
118 # define free_task_struct(tsk) \
119 kmem_cache_free(task_struct_cachep, (tsk))
120 static struct kmem_cache *task_struct_cachep;
123 #ifndef __HAVE_ARCH_THREAD_INFO_ALLOCATOR
124 static struct thread_info *alloc_thread_info_node(struct task_struct *tsk,
127 #ifdef CONFIG_DEBUG_STACK_USAGE
128 gfp_t mask = GFP_KERNEL | __GFP_ZERO;
130 gfp_t mask = GFP_KERNEL;
132 struct page *page = alloc_pages_node(node, mask, THREAD_SIZE_ORDER);
134 return page ? page_address(page) : NULL;
137 static inline void free_thread_info(struct thread_info *ti)
139 free_pages((unsigned long)ti, THREAD_SIZE_ORDER);
143 /* SLAB cache for signal_struct structures (tsk->signal) */
144 static struct kmem_cache *signal_cachep;
146 /* SLAB cache for sighand_struct structures (tsk->sighand) */
147 struct kmem_cache *sighand_cachep;
149 /* SLAB cache for files_struct structures (tsk->files) */
150 struct kmem_cache *files_cachep;
152 /* SLAB cache for fs_struct structures (tsk->fs) */
153 struct kmem_cache *fs_cachep;
155 /* SLAB cache for vm_area_struct structures */
156 struct kmem_cache *vm_area_cachep;
158 /* SLAB cache for mm_struct structures (tsk->mm) */
159 static struct kmem_cache *mm_cachep;
161 static void account_kernel_stack(struct thread_info *ti, int account)
163 struct zone *zone = page_zone(virt_to_page(ti));
165 mod_zone_page_state(zone, NR_KERNEL_STACK, account);
168 void free_task(struct task_struct *tsk)
170 account_kernel_stack(tsk->stack, -1);
171 free_thread_info(tsk->stack);
172 rt_mutex_debug_task_free(tsk);
173 ftrace_graph_exit_task(tsk);
174 free_task_struct(tsk);
176 EXPORT_SYMBOL(free_task);
178 static inline void free_signal_struct(struct signal_struct *sig)
180 taskstats_tgid_free(sig);
181 sched_autogroup_exit(sig);
182 kmem_cache_free(signal_cachep, sig);
185 static inline void put_signal_struct(struct signal_struct *sig)
187 if (atomic_dec_and_test(&sig->sigcnt))
188 free_signal_struct(sig);
191 void __put_task_struct(struct task_struct *tsk)
193 WARN_ON(!tsk->exit_state);
194 WARN_ON(atomic_read(&tsk->usage));
195 WARN_ON(tsk == current);
197 security_task_free(tsk);
199 delayacct_tsk_free(tsk);
200 put_signal_struct(tsk->signal);
202 if (!profile_handoff_task(tsk))
205 EXPORT_SYMBOL_GPL(__put_task_struct);
208 * macro override instead of weak attribute alias, to workaround
209 * gcc 4.1.0 and 4.1.1 bugs with weak attribute and empty functions.
211 #ifndef arch_task_cache_init
212 #define arch_task_cache_init()
215 void __init fork_init(unsigned long mempages)
217 #ifndef __HAVE_ARCH_TASK_STRUCT_ALLOCATOR
218 #ifndef ARCH_MIN_TASKALIGN
219 #define ARCH_MIN_TASKALIGN L1_CACHE_BYTES
221 /* create a slab on which task_structs can be allocated */
223 kmem_cache_create("task_struct", sizeof(struct task_struct),
224 ARCH_MIN_TASKALIGN, SLAB_PANIC | SLAB_NOTRACK, NULL);
227 /* do the arch specific task caches init */
228 arch_task_cache_init();
231 * The default maximum number of threads is set to a safe
232 * value: the thread structures can take up at most half
235 max_threads = mempages / (8 * THREAD_SIZE / PAGE_SIZE);
238 * we need to allow at least 20 threads to boot a system
240 if (max_threads < 20)
243 init_task.signal->rlim[RLIMIT_NPROC].rlim_cur = max_threads/2;
244 init_task.signal->rlim[RLIMIT_NPROC].rlim_max = max_threads/2;
245 init_task.signal->rlim[RLIMIT_SIGPENDING] =
246 init_task.signal->rlim[RLIMIT_NPROC];
249 int __attribute__((weak)) arch_dup_task_struct(struct task_struct *dst,
250 struct task_struct *src)
256 static struct task_struct *dup_task_struct(struct task_struct *orig)
258 struct task_struct *tsk;
259 struct thread_info *ti;
260 unsigned long *stackend;
261 int node = tsk_fork_get_node(orig);
264 tsk = alloc_task_struct_node(node);
268 ti = alloc_thread_info_node(tsk, node);
270 free_task_struct(tsk);
274 err = arch_dup_task_struct(tsk, orig);
280 setup_thread_stack(tsk, orig);
281 clear_user_return_notifier(tsk);
282 clear_tsk_need_resched(tsk);
283 stackend = end_of_stack(tsk);
284 *stackend = STACK_END_MAGIC; /* for overflow detection */
286 #ifdef CONFIG_CC_STACKPROTECTOR
287 tsk->stack_canary = get_random_int();
291 * One for us, one for whoever does the "release_task()" (usually
294 atomic_set(&tsk->usage, 2);
295 #ifdef CONFIG_BLK_DEV_IO_TRACE
298 tsk->splice_pipe = NULL;
300 account_kernel_stack(ti, 1);
305 free_thread_info(ti);
306 free_task_struct(tsk);
311 static int dup_mmap(struct mm_struct *mm, struct mm_struct *oldmm)
313 struct vm_area_struct *mpnt, *tmp, *prev, **pprev;
314 struct rb_node **rb_link, *rb_parent;
316 unsigned long charge;
317 struct mempolicy *pol;
319 down_write(&oldmm->mmap_sem);
320 flush_cache_dup_mm(oldmm);
322 * Not linked in yet - no deadlock potential:
324 down_write_nested(&mm->mmap_sem, SINGLE_DEPTH_NESTING);
328 mm->mmap_cache = NULL;
329 mm->free_area_cache = oldmm->mmap_base;
330 mm->cached_hole_size = ~0UL;
332 cpumask_clear(mm_cpumask(mm));
334 rb_link = &mm->mm_rb.rb_node;
337 retval = ksm_fork(mm, oldmm);
340 retval = khugepaged_fork(mm, oldmm);
345 for (mpnt = oldmm->mmap; mpnt; mpnt = mpnt->vm_next) {
348 if (mpnt->vm_flags & VM_DONTCOPY) {
349 long pages = vma_pages(mpnt);
350 mm->total_vm -= pages;
351 vm_stat_account(mm, mpnt->vm_flags, mpnt->vm_file,
356 if (mpnt->vm_flags & VM_ACCOUNT) {
357 unsigned int len = (mpnt->vm_end - mpnt->vm_start) >> PAGE_SHIFT;
358 if (security_vm_enough_memory_mm(oldmm, len)) /* sic */
362 tmp = kmem_cache_alloc(vm_area_cachep, GFP_KERNEL);
366 INIT_LIST_HEAD(&tmp->anon_vma_chain);
367 pol = mpol_dup(vma_policy(mpnt));
368 retval = PTR_ERR(pol);
370 goto fail_nomem_policy;
371 vma_set_policy(tmp, pol);
373 if (anon_vma_fork(tmp, mpnt))
374 goto fail_nomem_anon_vma_fork;
375 tmp->vm_flags &= ~VM_LOCKED;
376 tmp->vm_next = tmp->vm_prev = NULL;
379 struct inode *inode = file->f_path.dentry->d_inode;
380 struct address_space *mapping = file->f_mapping;
383 if (tmp->vm_flags & VM_DENYWRITE)
384 atomic_dec(&inode->i_writecount);
385 mutex_lock(&mapping->i_mmap_mutex);
386 if (tmp->vm_flags & VM_SHARED)
387 mapping->i_mmap_writable++;
388 flush_dcache_mmap_lock(mapping);
389 /* insert tmp into the share list, just after mpnt */
390 vma_prio_tree_add(tmp, mpnt);
391 flush_dcache_mmap_unlock(mapping);
392 mutex_unlock(&mapping->i_mmap_mutex);
396 * Clear hugetlb-related page reserves for children. This only
397 * affects MAP_PRIVATE mappings. Faults generated by the child
398 * are not guaranteed to succeed, even if read-only
400 if (is_vm_hugetlb_page(tmp))
401 reset_vma_resv_huge_pages(tmp);
404 * Link in the new vma and copy the page table entries.
407 pprev = &tmp->vm_next;
411 __vma_link_rb(mm, tmp, rb_link, rb_parent);
412 rb_link = &tmp->vm_rb.rb_right;
413 rb_parent = &tmp->vm_rb;
416 retval = copy_page_range(mm, oldmm, mpnt);
418 if (tmp->vm_ops && tmp->vm_ops->open)
419 tmp->vm_ops->open(tmp);
424 /* a new mm has just been created */
425 arch_dup_mmap(oldmm, mm);
428 up_write(&mm->mmap_sem);
430 up_write(&oldmm->mmap_sem);
432 fail_nomem_anon_vma_fork:
435 kmem_cache_free(vm_area_cachep, tmp);
438 vm_unacct_memory(charge);
442 static inline int mm_alloc_pgd(struct mm_struct *mm)
444 mm->pgd = pgd_alloc(mm);
445 if (unlikely(!mm->pgd))
450 static inline void mm_free_pgd(struct mm_struct *mm)
452 pgd_free(mm, mm->pgd);
455 #define dup_mmap(mm, oldmm) (0)
456 #define mm_alloc_pgd(mm) (0)
457 #define mm_free_pgd(mm)
458 #endif /* CONFIG_MMU */
460 __cacheline_aligned_in_smp DEFINE_SPINLOCK(mmlist_lock);
462 #define allocate_mm() (kmem_cache_alloc(mm_cachep, GFP_KERNEL))
463 #define free_mm(mm) (kmem_cache_free(mm_cachep, (mm)))
465 static unsigned long default_dump_filter = MMF_DUMP_FILTER_DEFAULT;
467 static int __init coredump_filter_setup(char *s)
469 default_dump_filter =
470 (simple_strtoul(s, NULL, 0) << MMF_DUMP_FILTER_SHIFT) &
471 MMF_DUMP_FILTER_MASK;
475 __setup("coredump_filter=", coredump_filter_setup);
477 #include <linux/init_task.h>
479 static void mm_init_aio(struct mm_struct *mm)
482 spin_lock_init(&mm->ioctx_lock);
483 INIT_HLIST_HEAD(&mm->ioctx_list);
487 static struct mm_struct *mm_init(struct mm_struct *mm, struct task_struct *p)
489 atomic_set(&mm->mm_users, 1);
490 atomic_set(&mm->mm_count, 1);
491 init_rwsem(&mm->mmap_sem);
492 INIT_LIST_HEAD(&mm->mmlist);
493 mm->flags = (current->mm) ?
494 (current->mm->flags & MMF_INIT_MASK) : default_dump_filter;
495 mm->core_state = NULL;
497 memset(&mm->rss_stat, 0, sizeof(mm->rss_stat));
498 spin_lock_init(&mm->page_table_lock);
499 mm->free_area_cache = TASK_UNMAPPED_BASE;
500 mm->cached_hole_size = ~0UL;
502 mm_init_owner(mm, p);
504 if (likely(!mm_alloc_pgd(mm))) {
506 mmu_notifier_mm_init(mm);
514 static void check_mm(struct mm_struct *mm)
518 for (i = 0; i < NR_MM_COUNTERS; i++) {
519 long x = atomic_long_read(&mm->rss_stat.count[i]);
522 printk(KERN_ALERT "BUG: Bad rss-counter state "
523 "mm:%p idx:%d val:%ld\n", mm, i, x);
526 #ifdef CONFIG_TRANSPARENT_HUGEPAGE
527 VM_BUG_ON(mm->pmd_huge_pte);
532 * Allocate and initialize an mm_struct.
534 struct mm_struct *mm_alloc(void)
536 struct mm_struct *mm;
542 memset(mm, 0, sizeof(*mm));
544 return mm_init(mm, current);
548 * Called when the last reference to the mm
549 * is dropped: either by a lazy thread or by
550 * mmput. Free the page directory and the mm.
552 void __mmdrop(struct mm_struct *mm)
554 BUG_ON(mm == &init_mm);
557 mmu_notifier_mm_destroy(mm);
561 EXPORT_SYMBOL_GPL(__mmdrop);
564 * Decrement the use count and release all resources for an mm.
566 void mmput(struct mm_struct *mm)
570 if (atomic_dec_and_test(&mm->mm_users)) {
573 khugepaged_exit(mm); /* must run before exit_mmap */
575 set_mm_exe_file(mm, NULL);
576 if (!list_empty(&mm->mmlist)) {
577 spin_lock(&mmlist_lock);
578 list_del(&mm->mmlist);
579 spin_unlock(&mmlist_lock);
583 module_put(mm->binfmt->module);
587 EXPORT_SYMBOL_GPL(mmput);
590 * We added or removed a vma mapping the executable. The vmas are only mapped
591 * during exec and are not mapped with the mmap system call.
592 * Callers must hold down_write() on the mm's mmap_sem for these
594 void added_exe_file_vma(struct mm_struct *mm)
596 mm->num_exe_file_vmas++;
599 void removed_exe_file_vma(struct mm_struct *mm)
601 mm->num_exe_file_vmas--;
602 if ((mm->num_exe_file_vmas == 0) && mm->exe_file) {
609 void set_mm_exe_file(struct mm_struct *mm, struct file *new_exe_file)
612 get_file(new_exe_file);
615 mm->exe_file = new_exe_file;
616 mm->num_exe_file_vmas = 0;
619 struct file *get_mm_exe_file(struct mm_struct *mm)
621 struct file *exe_file;
623 /* We need mmap_sem to protect against races with removal of
624 * VM_EXECUTABLE vmas */
625 down_read(&mm->mmap_sem);
626 exe_file = mm->exe_file;
629 up_read(&mm->mmap_sem);
633 static void dup_mm_exe_file(struct mm_struct *oldmm, struct mm_struct *newmm)
635 /* It's safe to write the exe_file pointer without exe_file_lock because
636 * this is called during fork when the task is not yet in /proc */
637 newmm->exe_file = get_mm_exe_file(oldmm);
641 * get_task_mm - acquire a reference to the task's mm
643 * Returns %NULL if the task has no mm. Checks PF_KTHREAD (meaning
644 * this kernel workthread has transiently adopted a user mm with use_mm,
645 * to do its AIO) is not set and if so returns a reference to it, after
646 * bumping up the use count. User must release the mm via mmput()
647 * after use. Typically used by /proc and ptrace.
649 struct mm_struct *get_task_mm(struct task_struct *task)
651 struct mm_struct *mm;
656 if (task->flags & PF_KTHREAD)
659 atomic_inc(&mm->mm_users);
664 EXPORT_SYMBOL_GPL(get_task_mm);
666 struct mm_struct *mm_access(struct task_struct *task, unsigned int mode)
668 struct mm_struct *mm;
671 err = mutex_lock_killable(&task->signal->cred_guard_mutex);
675 mm = get_task_mm(task);
676 if (mm && mm != current->mm &&
677 !ptrace_may_access(task, mode)) {
679 mm = ERR_PTR(-EACCES);
681 mutex_unlock(&task->signal->cred_guard_mutex);
686 static void complete_vfork_done(struct task_struct *tsk)
688 struct completion *vfork;
691 vfork = tsk->vfork_done;
693 tsk->vfork_done = NULL;
699 static int wait_for_vfork_done(struct task_struct *child,
700 struct completion *vfork)
704 freezer_do_not_count();
705 killed = wait_for_completion_killable(vfork);
710 child->vfork_done = NULL;
714 put_task_struct(child);
718 /* Please note the differences between mmput and mm_release.
719 * mmput is called whenever we stop holding onto a mm_struct,
720 * error success whatever.
722 * mm_release is called after a mm_struct has been removed
723 * from the current process.
725 * This difference is important for error handling, when we
726 * only half set up a mm_struct for a new process and need to restore
727 * the old one. Because we mmput the new mm_struct before
728 * restoring the old one. . .
729 * Eric Biederman 10 January 1998
731 void mm_release(struct task_struct *tsk, struct mm_struct *mm)
733 /* Get rid of any futexes when releasing the mm */
735 if (unlikely(tsk->robust_list)) {
736 exit_robust_list(tsk);
737 tsk->robust_list = NULL;
740 if (unlikely(tsk->compat_robust_list)) {
741 compat_exit_robust_list(tsk);
742 tsk->compat_robust_list = NULL;
745 if (unlikely(!list_empty(&tsk->pi_state_list)))
746 exit_pi_state_list(tsk);
749 /* Get rid of any cached register state */
750 deactivate_mm(tsk, mm);
753 complete_vfork_done(tsk);
756 * If we're exiting normally, clear a user-space tid field if
757 * requested. We leave this alone when dying by signal, to leave
758 * the value intact in a core dump, and to save the unnecessary
759 * trouble, say, a killed vfork parent shouldn't touch this mm.
760 * Userland only wants this done for a sys_exit.
762 if (tsk->clear_child_tid) {
763 if (!(tsk->flags & PF_SIGNALED) &&
764 atomic_read(&mm->mm_users) > 1) {
766 * We don't check the error code - if userspace has
767 * not set up a proper pointer then tough luck.
769 put_user(0, tsk->clear_child_tid);
770 sys_futex(tsk->clear_child_tid, FUTEX_WAKE,
773 tsk->clear_child_tid = NULL;
778 * Allocate a new mm structure and copy contents from the
779 * mm structure of the passed in task structure.
781 struct mm_struct *dup_mm(struct task_struct *tsk)
783 struct mm_struct *mm, *oldmm = current->mm;
793 memcpy(mm, oldmm, sizeof(*mm));
796 /* Initializing for Swap token stuff */
797 mm->token_priority = 0;
798 mm->last_interval = 0;
800 #ifdef CONFIG_TRANSPARENT_HUGEPAGE
801 mm->pmd_huge_pte = NULL;
804 if (!mm_init(mm, tsk))
807 if (init_new_context(tsk, mm))
810 dup_mm_exe_file(oldmm, mm);
812 err = dup_mmap(mm, oldmm);
816 mm->hiwater_rss = get_mm_rss(mm);
817 mm->hiwater_vm = mm->total_vm;
819 if (mm->binfmt && !try_module_get(mm->binfmt->module))
825 /* don't put binfmt in mmput, we haven't got module yet */
834 * If init_new_context() failed, we cannot use mmput() to free the mm
835 * because it calls destroy_context()
842 static int copy_mm(unsigned long clone_flags, struct task_struct *tsk)
844 struct mm_struct *mm, *oldmm;
847 tsk->min_flt = tsk->maj_flt = 0;
848 tsk->nvcsw = tsk->nivcsw = 0;
849 #ifdef CONFIG_DETECT_HUNG_TASK
850 tsk->last_switch_count = tsk->nvcsw + tsk->nivcsw;
854 tsk->active_mm = NULL;
857 * Are we cloning a kernel thread?
859 * We need to steal a active VM for that..
865 if (clone_flags & CLONE_VM) {
866 atomic_inc(&oldmm->mm_users);
877 /* Initializing for Swap token stuff */
878 mm->token_priority = 0;
879 mm->last_interval = 0;
889 static int copy_fs(unsigned long clone_flags, struct task_struct *tsk)
891 struct fs_struct *fs = current->fs;
892 if (clone_flags & CLONE_FS) {
893 /* tsk->fs is already what we want */
894 spin_lock(&fs->lock);
896 spin_unlock(&fs->lock);
900 spin_unlock(&fs->lock);
903 tsk->fs = copy_fs_struct(fs);
909 static int copy_files(unsigned long clone_flags, struct task_struct *tsk)
911 struct files_struct *oldf, *newf;
915 * A background process may not have any files ...
917 oldf = current->files;
921 if (clone_flags & CLONE_FILES) {
922 atomic_inc(&oldf->count);
926 newf = dup_fd(oldf, &error);
936 static int copy_io(unsigned long clone_flags, struct task_struct *tsk)
939 struct io_context *ioc = current->io_context;
940 struct io_context *new_ioc;
945 * Share io context with parent, if CLONE_IO is set
947 if (clone_flags & CLONE_IO) {
948 tsk->io_context = ioc_task_link(ioc);
949 if (unlikely(!tsk->io_context))
951 } else if (ioprio_valid(ioc->ioprio)) {
952 new_ioc = get_task_io_context(tsk, GFP_KERNEL, NUMA_NO_NODE);
953 if (unlikely(!new_ioc))
956 new_ioc->ioprio = ioc->ioprio;
957 put_io_context(new_ioc);
963 static int copy_sighand(unsigned long clone_flags, struct task_struct *tsk)
965 struct sighand_struct *sig;
967 if (clone_flags & CLONE_SIGHAND) {
968 atomic_inc(¤t->sighand->count);
971 sig = kmem_cache_alloc(sighand_cachep, GFP_KERNEL);
972 rcu_assign_pointer(tsk->sighand, sig);
975 atomic_set(&sig->count, 1);
976 memcpy(sig->action, current->sighand->action, sizeof(sig->action));
980 void __cleanup_sighand(struct sighand_struct *sighand)
982 if (atomic_dec_and_test(&sighand->count)) {
983 signalfd_cleanup(sighand);
984 kmem_cache_free(sighand_cachep, sighand);
990 * Initialize POSIX timer handling for a thread group.
992 static void posix_cpu_timers_init_group(struct signal_struct *sig)
994 unsigned long cpu_limit;
996 /* Thread group counters. */
997 thread_group_cputime_init(sig);
999 cpu_limit = ACCESS_ONCE(sig->rlim[RLIMIT_CPU].rlim_cur);
1000 if (cpu_limit != RLIM_INFINITY) {
1001 sig->cputime_expires.prof_exp = secs_to_cputime(cpu_limit);
1002 sig->cputimer.running = 1;
1005 /* The timer lists. */
1006 INIT_LIST_HEAD(&sig->cpu_timers[0]);
1007 INIT_LIST_HEAD(&sig->cpu_timers[1]);
1008 INIT_LIST_HEAD(&sig->cpu_timers[2]);
1011 static int copy_signal(unsigned long clone_flags, struct task_struct *tsk)
1013 struct signal_struct *sig;
1015 if (clone_flags & CLONE_THREAD)
1018 sig = kmem_cache_zalloc(signal_cachep, GFP_KERNEL);
1023 sig->nr_threads = 1;
1024 atomic_set(&sig->live, 1);
1025 atomic_set(&sig->sigcnt, 1);
1026 init_waitqueue_head(&sig->wait_chldexit);
1027 if (clone_flags & CLONE_NEWPID)
1028 sig->flags |= SIGNAL_UNKILLABLE;
1029 sig->curr_target = tsk;
1030 init_sigpending(&sig->shared_pending);
1031 INIT_LIST_HEAD(&sig->posix_timers);
1033 hrtimer_init(&sig->real_timer, CLOCK_MONOTONIC, HRTIMER_MODE_REL);
1034 sig->real_timer.function = it_real_fn;
1036 task_lock(current->group_leader);
1037 memcpy(sig->rlim, current->signal->rlim, sizeof sig->rlim);
1038 task_unlock(current->group_leader);
1040 posix_cpu_timers_init_group(sig);
1042 tty_audit_fork(sig);
1043 sched_autogroup_fork(sig);
1045 #ifdef CONFIG_CGROUPS
1046 init_rwsem(&sig->group_rwsem);
1049 sig->oom_adj = current->signal->oom_adj;
1050 sig->oom_score_adj = current->signal->oom_score_adj;
1051 sig->oom_score_adj_min = current->signal->oom_score_adj_min;
1053 sig->has_child_subreaper = current->signal->has_child_subreaper ||
1054 current->signal->is_child_subreaper;
1056 mutex_init(&sig->cred_guard_mutex);
1061 static void copy_flags(unsigned long clone_flags, struct task_struct *p)
1063 unsigned long new_flags = p->flags;
1065 new_flags &= ~(PF_SUPERPRIV | PF_WQ_WORKER);
1066 new_flags |= PF_FORKNOEXEC;
1067 p->flags = new_flags;
1070 SYSCALL_DEFINE1(set_tid_address, int __user *, tidptr)
1072 current->clear_child_tid = tidptr;
1074 return task_pid_vnr(current);
1077 static void rt_mutex_init_task(struct task_struct *p)
1079 raw_spin_lock_init(&p->pi_lock);
1080 #ifdef CONFIG_RT_MUTEXES
1081 plist_head_init(&p->pi_waiters);
1082 p->pi_blocked_on = NULL;
1086 #ifdef CONFIG_MM_OWNER
1087 void mm_init_owner(struct mm_struct *mm, struct task_struct *p)
1091 #endif /* CONFIG_MM_OWNER */
1094 * Initialize POSIX timer handling for a single task.
1096 static void posix_cpu_timers_init(struct task_struct *tsk)
1098 tsk->cputime_expires.prof_exp = 0;
1099 tsk->cputime_expires.virt_exp = 0;
1100 tsk->cputime_expires.sched_exp = 0;
1101 INIT_LIST_HEAD(&tsk->cpu_timers[0]);
1102 INIT_LIST_HEAD(&tsk->cpu_timers[1]);
1103 INIT_LIST_HEAD(&tsk->cpu_timers[2]);
1107 * This creates a new process as a copy of the old one,
1108 * but does not actually start it yet.
1110 * It copies the registers, and all the appropriate
1111 * parts of the process environment (as per the clone
1112 * flags). The actual kick-off is left to the caller.
1114 static struct task_struct *copy_process(unsigned long clone_flags,
1115 unsigned long stack_start,
1116 struct pt_regs *regs,
1117 unsigned long stack_size,
1118 int __user *child_tidptr,
1123 struct task_struct *p;
1124 int cgroup_callbacks_done = 0;
1126 if ((clone_flags & (CLONE_NEWNS|CLONE_FS)) == (CLONE_NEWNS|CLONE_FS))
1127 return ERR_PTR(-EINVAL);
1130 * Thread groups must share signals as well, and detached threads
1131 * can only be started up within the thread group.
1133 if ((clone_flags & CLONE_THREAD) && !(clone_flags & CLONE_SIGHAND))
1134 return ERR_PTR(-EINVAL);
1137 * Shared signal handlers imply shared VM. By way of the above,
1138 * thread groups also imply shared VM. Blocking this case allows
1139 * for various simplifications in other code.
1141 if ((clone_flags & CLONE_SIGHAND) && !(clone_flags & CLONE_VM))
1142 return ERR_PTR(-EINVAL);
1145 * Siblings of global init remain as zombies on exit since they are
1146 * not reaped by their parent (swapper). To solve this and to avoid
1147 * multi-rooted process trees, prevent global and container-inits
1148 * from creating siblings.
1150 if ((clone_flags & CLONE_PARENT) &&
1151 current->signal->flags & SIGNAL_UNKILLABLE)
1152 return ERR_PTR(-EINVAL);
1154 retval = security_task_create(clone_flags);
1159 p = dup_task_struct(current);
1163 ftrace_graph_init_task(p);
1165 rt_mutex_init_task(p);
1167 #ifdef CONFIG_PROVE_LOCKING
1168 DEBUG_LOCKS_WARN_ON(!p->hardirqs_enabled);
1169 DEBUG_LOCKS_WARN_ON(!p->softirqs_enabled);
1172 if (atomic_read(&p->real_cred->user->processes) >=
1173 task_rlimit(p, RLIMIT_NPROC)) {
1174 if (!capable(CAP_SYS_ADMIN) && !capable(CAP_SYS_RESOURCE) &&
1175 p->real_cred->user != INIT_USER)
1178 current->flags &= ~PF_NPROC_EXCEEDED;
1180 retval = copy_creds(p, clone_flags);
1185 * If multiple threads are within copy_process(), then this check
1186 * triggers too late. This doesn't hurt, the check is only there
1187 * to stop root fork bombs.
1190 if (nr_threads >= max_threads)
1191 goto bad_fork_cleanup_count;
1193 if (!try_module_get(task_thread_info(p)->exec_domain->module))
1194 goto bad_fork_cleanup_count;
1197 delayacct_tsk_init(p); /* Must remain after dup_task_struct() */
1198 copy_flags(clone_flags, p);
1199 INIT_LIST_HEAD(&p->children);
1200 INIT_LIST_HEAD(&p->sibling);
1201 rcu_copy_process(p);
1202 p->vfork_done = NULL;
1203 spin_lock_init(&p->alloc_lock);
1205 init_sigpending(&p->pending);
1207 p->utime = p->stime = p->gtime = 0;
1208 p->utimescaled = p->stimescaled = 0;
1209 #ifndef CONFIG_VIRT_CPU_ACCOUNTING
1210 p->prev_utime = p->prev_stime = 0;
1212 #if defined(SPLIT_RSS_COUNTING)
1213 memset(&p->rss_stat, 0, sizeof(p->rss_stat));
1216 p->default_timer_slack_ns = current->timer_slack_ns;
1218 task_io_accounting_init(&p->ioac);
1219 acct_clear_integrals(p);
1221 posix_cpu_timers_init(p);
1223 do_posix_clock_monotonic_gettime(&p->start_time);
1224 p->real_start_time = p->start_time;
1225 monotonic_to_bootbased(&p->real_start_time);
1226 p->io_context = NULL;
1227 p->audit_context = NULL;
1228 if (clone_flags & CLONE_THREAD)
1229 threadgroup_change_begin(current);
1232 p->mempolicy = mpol_dup(p->mempolicy);
1233 if (IS_ERR(p->mempolicy)) {
1234 retval = PTR_ERR(p->mempolicy);
1235 p->mempolicy = NULL;
1236 goto bad_fork_cleanup_cgroup;
1238 mpol_fix_fork_child_flag(p);
1240 #ifdef CONFIG_CPUSETS
1241 p->cpuset_mem_spread_rotor = NUMA_NO_NODE;
1242 p->cpuset_slab_spread_rotor = NUMA_NO_NODE;
1243 seqcount_init(&p->mems_allowed_seq);
1245 #ifdef CONFIG_TRACE_IRQFLAGS
1247 #ifdef __ARCH_WANT_INTERRUPTS_ON_CTXSW
1248 p->hardirqs_enabled = 1;
1250 p->hardirqs_enabled = 0;
1252 p->hardirq_enable_ip = 0;
1253 p->hardirq_enable_event = 0;
1254 p->hardirq_disable_ip = _THIS_IP_;
1255 p->hardirq_disable_event = 0;
1256 p->softirqs_enabled = 1;
1257 p->softirq_enable_ip = _THIS_IP_;
1258 p->softirq_enable_event = 0;
1259 p->softirq_disable_ip = 0;
1260 p->softirq_disable_event = 0;
1261 p->hardirq_context = 0;
1262 p->softirq_context = 0;
1264 #ifdef CONFIG_LOCKDEP
1265 p->lockdep_depth = 0; /* no locks held yet */
1266 p->curr_chain_key = 0;
1267 p->lockdep_recursion = 0;
1270 #ifdef CONFIG_DEBUG_MUTEXES
1271 p->blocked_on = NULL; /* not blocked yet */
1273 #ifdef CONFIG_CGROUP_MEM_RES_CTLR
1274 p->memcg_batch.do_batch = 0;
1275 p->memcg_batch.memcg = NULL;
1278 /* Perform scheduler related setup. Assign this task to a CPU. */
1281 retval = perf_event_init_task(p);
1283 goto bad_fork_cleanup_policy;
1284 retval = audit_alloc(p);
1286 goto bad_fork_cleanup_policy;
1287 /* copy all the process information */
1288 retval = copy_semundo(clone_flags, p);
1290 goto bad_fork_cleanup_audit;
1291 retval = copy_files(clone_flags, p);
1293 goto bad_fork_cleanup_semundo;
1294 retval = copy_fs(clone_flags, p);
1296 goto bad_fork_cleanup_files;
1297 retval = copy_sighand(clone_flags, p);
1299 goto bad_fork_cleanup_fs;
1300 retval = copy_signal(clone_flags, p);
1302 goto bad_fork_cleanup_sighand;
1303 retval = copy_mm(clone_flags, p);
1305 goto bad_fork_cleanup_signal;
1306 retval = copy_namespaces(clone_flags, p);
1308 goto bad_fork_cleanup_mm;
1309 retval = copy_io(clone_flags, p);
1311 goto bad_fork_cleanup_namespaces;
1312 retval = copy_thread(clone_flags, stack_start, stack_size, p, regs);
1314 goto bad_fork_cleanup_io;
1316 if (pid != &init_struct_pid) {
1318 pid = alloc_pid(p->nsproxy->pid_ns);
1320 goto bad_fork_cleanup_io;
1323 p->pid = pid_nr(pid);
1325 if (clone_flags & CLONE_THREAD)
1326 p->tgid = current->tgid;
1328 p->set_child_tid = (clone_flags & CLONE_CHILD_SETTID) ? child_tidptr : NULL;
1330 * Clear TID on mm_release()?
1332 p->clear_child_tid = (clone_flags & CLONE_CHILD_CLEARTID) ? child_tidptr : NULL;
1337 p->robust_list = NULL;
1338 #ifdef CONFIG_COMPAT
1339 p->compat_robust_list = NULL;
1341 INIT_LIST_HEAD(&p->pi_state_list);
1342 p->pi_state_cache = NULL;
1345 * sigaltstack should be cleared when sharing the same VM
1347 if ((clone_flags & (CLONE_VM|CLONE_VFORK)) == CLONE_VM)
1348 p->sas_ss_sp = p->sas_ss_size = 0;
1351 * Syscall tracing and stepping should be turned off in the
1352 * child regardless of CLONE_PTRACE.
1354 user_disable_single_step(p);
1355 clear_tsk_thread_flag(p, TIF_SYSCALL_TRACE);
1356 #ifdef TIF_SYSCALL_EMU
1357 clear_tsk_thread_flag(p, TIF_SYSCALL_EMU);
1359 clear_all_latency_tracing(p);
1361 /* ok, now we should be set up.. */
1362 if (clone_flags & CLONE_THREAD)
1363 p->exit_signal = -1;
1364 else if (clone_flags & CLONE_PARENT)
1365 p->exit_signal = current->group_leader->exit_signal;
1367 p->exit_signal = (clone_flags & CSIGNAL);
1369 p->pdeath_signal = 0;
1373 p->nr_dirtied_pause = 128 >> (PAGE_SHIFT - 10);
1374 p->dirty_paused_when = 0;
1377 * Ok, make it visible to the rest of the system.
1378 * We dont wake it up yet.
1380 p->group_leader = p;
1381 INIT_LIST_HEAD(&p->thread_group);
1383 /* Now that the task is set up, run cgroup callbacks if
1384 * necessary. We need to run them before the task is visible
1385 * on the tasklist. */
1386 cgroup_fork_callbacks(p);
1387 cgroup_callbacks_done = 1;
1389 /* Need tasklist lock for parent etc handling! */
1390 write_lock_irq(&tasklist_lock);
1392 /* CLONE_PARENT re-uses the old parent */
1393 if (clone_flags & (CLONE_PARENT|CLONE_THREAD)) {
1394 p->real_parent = current->real_parent;
1395 p->parent_exec_id = current->parent_exec_id;
1397 p->real_parent = current;
1398 p->parent_exec_id = current->self_exec_id;
1401 spin_lock(¤t->sighand->siglock);
1404 * Process group and session signals need to be delivered to just the
1405 * parent before the fork or both the parent and the child after the
1406 * fork. Restart if a signal comes in before we add the new process to
1407 * it's process group.
1408 * A fatal signal pending means that current will exit, so the new
1409 * thread can't slip out of an OOM kill (or normal SIGKILL).
1411 recalc_sigpending();
1412 if (signal_pending(current)) {
1413 spin_unlock(¤t->sighand->siglock);
1414 write_unlock_irq(&tasklist_lock);
1415 retval = -ERESTARTNOINTR;
1416 goto bad_fork_free_pid;
1419 if (clone_flags & CLONE_THREAD) {
1420 current->signal->nr_threads++;
1421 atomic_inc(¤t->signal->live);
1422 atomic_inc(¤t->signal->sigcnt);
1423 p->group_leader = current->group_leader;
1424 list_add_tail_rcu(&p->thread_group, &p->group_leader->thread_group);
1427 if (likely(p->pid)) {
1428 ptrace_init_task(p, (clone_flags & CLONE_PTRACE) || trace);
1430 if (thread_group_leader(p)) {
1431 if (is_child_reaper(pid))
1432 p->nsproxy->pid_ns->child_reaper = p;
1434 p->signal->leader_pid = pid;
1435 p->signal->tty = tty_kref_get(current->signal->tty);
1436 attach_pid(p, PIDTYPE_PGID, task_pgrp(current));
1437 attach_pid(p, PIDTYPE_SID, task_session(current));
1438 list_add_tail(&p->sibling, &p->real_parent->children);
1439 list_add_tail_rcu(&p->tasks, &init_task.tasks);
1440 __this_cpu_inc(process_counts);
1442 attach_pid(p, PIDTYPE_PID, pid);
1447 spin_unlock(¤t->sighand->siglock);
1448 write_unlock_irq(&tasklist_lock);
1449 proc_fork_connector(p);
1450 cgroup_post_fork(p);
1451 if (clone_flags & CLONE_THREAD)
1452 threadgroup_change_end(current);
1455 trace_task_newtask(p, clone_flags);
1460 if (pid != &init_struct_pid)
1462 bad_fork_cleanup_io:
1465 bad_fork_cleanup_namespaces:
1466 if (unlikely(clone_flags & CLONE_NEWPID))
1467 pid_ns_release_proc(p->nsproxy->pid_ns);
1468 exit_task_namespaces(p);
1469 bad_fork_cleanup_mm:
1472 bad_fork_cleanup_signal:
1473 if (!(clone_flags & CLONE_THREAD))
1474 free_signal_struct(p->signal);
1475 bad_fork_cleanup_sighand:
1476 __cleanup_sighand(p->sighand);
1477 bad_fork_cleanup_fs:
1478 exit_fs(p); /* blocking */
1479 bad_fork_cleanup_files:
1480 exit_files(p); /* blocking */
1481 bad_fork_cleanup_semundo:
1483 bad_fork_cleanup_audit:
1485 bad_fork_cleanup_policy:
1486 perf_event_free_task(p);
1488 mpol_put(p->mempolicy);
1489 bad_fork_cleanup_cgroup:
1491 if (clone_flags & CLONE_THREAD)
1492 threadgroup_change_end(current);
1493 cgroup_exit(p, cgroup_callbacks_done);
1494 delayacct_tsk_free(p);
1495 module_put(task_thread_info(p)->exec_domain->module);
1496 bad_fork_cleanup_count:
1497 atomic_dec(&p->cred->user->processes);
1502 return ERR_PTR(retval);
1505 noinline struct pt_regs * __cpuinit __attribute__((weak)) idle_regs(struct pt_regs *regs)
1507 memset(regs, 0, sizeof(struct pt_regs));
1511 static inline void init_idle_pids(struct pid_link *links)
1515 for (type = PIDTYPE_PID; type < PIDTYPE_MAX; ++type) {
1516 INIT_HLIST_NODE(&links[type].node); /* not really needed */
1517 links[type].pid = &init_struct_pid;
1521 struct task_struct * __cpuinit fork_idle(int cpu)
1523 struct task_struct *task;
1524 struct pt_regs regs;
1526 task = copy_process(CLONE_VM, 0, idle_regs(®s), 0, NULL,
1527 &init_struct_pid, 0);
1528 if (!IS_ERR(task)) {
1529 init_idle_pids(task->pids);
1530 init_idle(task, cpu);
1537 * Ok, this is the main fork-routine.
1539 * It copies the process, and if successful kick-starts
1540 * it and waits for it to finish using the VM if required.
1542 long do_fork(unsigned long clone_flags,
1543 unsigned long stack_start,
1544 struct pt_regs *regs,
1545 unsigned long stack_size,
1546 int __user *parent_tidptr,
1547 int __user *child_tidptr)
1549 struct task_struct *p;
1554 * Do some preliminary argument and permissions checking before we
1555 * actually start allocating stuff
1557 if (clone_flags & CLONE_NEWUSER) {
1558 if (clone_flags & CLONE_THREAD)
1560 /* hopefully this check will go away when userns support is
1563 if (!capable(CAP_SYS_ADMIN) || !capable(CAP_SETUID) ||
1564 !capable(CAP_SETGID))
1569 * Determine whether and which event to report to ptracer. When
1570 * called from kernel_thread or CLONE_UNTRACED is explicitly
1571 * requested, no event is reported; otherwise, report if the event
1572 * for the type of forking is enabled.
1574 if (likely(user_mode(regs)) && !(clone_flags & CLONE_UNTRACED)) {
1575 if (clone_flags & CLONE_VFORK)
1576 trace = PTRACE_EVENT_VFORK;
1577 else if ((clone_flags & CSIGNAL) != SIGCHLD)
1578 trace = PTRACE_EVENT_CLONE;
1580 trace = PTRACE_EVENT_FORK;
1582 if (likely(!ptrace_event_enabled(current, trace)))
1586 p = copy_process(clone_flags, stack_start, regs, stack_size,
1587 child_tidptr, NULL, trace);
1589 * Do this prior waking up the new thread - the thread pointer
1590 * might get invalid after that point, if the thread exits quickly.
1593 struct completion vfork;
1595 trace_sched_process_fork(current, p);
1597 nr = task_pid_vnr(p);
1599 if (clone_flags & CLONE_PARENT_SETTID)
1600 put_user(nr, parent_tidptr);
1602 if (clone_flags & CLONE_VFORK) {
1603 p->vfork_done = &vfork;
1604 init_completion(&vfork);
1608 wake_up_new_task(p);
1610 /* forking complete and child started to run, tell ptracer */
1611 if (unlikely(trace))
1612 ptrace_event(trace, nr);
1614 if (clone_flags & CLONE_VFORK) {
1615 if (!wait_for_vfork_done(p, &vfork))
1616 ptrace_event(PTRACE_EVENT_VFORK_DONE, nr);
1624 #ifndef ARCH_MIN_MMSTRUCT_ALIGN
1625 #define ARCH_MIN_MMSTRUCT_ALIGN 0
1628 static void sighand_ctor(void *data)
1630 struct sighand_struct *sighand = data;
1632 spin_lock_init(&sighand->siglock);
1633 init_waitqueue_head(&sighand->signalfd_wqh);
1636 void __init proc_caches_init(void)
1638 sighand_cachep = kmem_cache_create("sighand_cache",
1639 sizeof(struct sighand_struct), 0,
1640 SLAB_HWCACHE_ALIGN|SLAB_PANIC|SLAB_DESTROY_BY_RCU|
1641 SLAB_NOTRACK, sighand_ctor);
1642 signal_cachep = kmem_cache_create("signal_cache",
1643 sizeof(struct signal_struct), 0,
1644 SLAB_HWCACHE_ALIGN|SLAB_PANIC|SLAB_NOTRACK, NULL);
1645 files_cachep = kmem_cache_create("files_cache",
1646 sizeof(struct files_struct), 0,
1647 SLAB_HWCACHE_ALIGN|SLAB_PANIC|SLAB_NOTRACK, NULL);
1648 fs_cachep = kmem_cache_create("fs_cache",
1649 sizeof(struct fs_struct), 0,
1650 SLAB_HWCACHE_ALIGN|SLAB_PANIC|SLAB_NOTRACK, NULL);
1652 * FIXME! The "sizeof(struct mm_struct)" currently includes the
1653 * whole struct cpumask for the OFFSTACK case. We could change
1654 * this to *only* allocate as much of it as required by the
1655 * maximum number of CPU's we can ever have. The cpumask_allocation
1656 * is at the end of the structure, exactly for that reason.
1658 mm_cachep = kmem_cache_create("mm_struct",
1659 sizeof(struct mm_struct), ARCH_MIN_MMSTRUCT_ALIGN,
1660 SLAB_HWCACHE_ALIGN|SLAB_PANIC|SLAB_NOTRACK, NULL);
1661 vm_area_cachep = KMEM_CACHE(vm_area_struct, SLAB_PANIC);
1663 nsproxy_cache_init();
1667 * Check constraints on flags passed to the unshare system call.
1669 static int check_unshare_flags(unsigned long unshare_flags)
1671 if (unshare_flags & ~(CLONE_THREAD|CLONE_FS|CLONE_NEWNS|CLONE_SIGHAND|
1672 CLONE_VM|CLONE_FILES|CLONE_SYSVSEM|
1673 CLONE_NEWUTS|CLONE_NEWIPC|CLONE_NEWNET))
1676 * Not implemented, but pretend it works if there is nothing to
1677 * unshare. Note that unsharing CLONE_THREAD or CLONE_SIGHAND
1678 * needs to unshare vm.
1680 if (unshare_flags & (CLONE_THREAD | CLONE_SIGHAND | CLONE_VM)) {
1681 /* FIXME: get_task_mm() increments ->mm_users */
1682 if (atomic_read(¤t->mm->mm_users) > 1)
1690 * Unshare the filesystem structure if it is being shared
1692 static int unshare_fs(unsigned long unshare_flags, struct fs_struct **new_fsp)
1694 struct fs_struct *fs = current->fs;
1696 if (!(unshare_flags & CLONE_FS) || !fs)
1699 /* don't need lock here; in the worst case we'll do useless copy */
1703 *new_fsp = copy_fs_struct(fs);
1711 * Unshare file descriptor table if it is being shared
1713 static int unshare_fd(unsigned long unshare_flags, struct files_struct **new_fdp)
1715 struct files_struct *fd = current->files;
1718 if ((unshare_flags & CLONE_FILES) &&
1719 (fd && atomic_read(&fd->count) > 1)) {
1720 *new_fdp = dup_fd(fd, &error);
1729 * unshare allows a process to 'unshare' part of the process
1730 * context which was originally shared using clone. copy_*
1731 * functions used by do_fork() cannot be used here directly
1732 * because they modify an inactive task_struct that is being
1733 * constructed. Here we are modifying the current, active,
1736 SYSCALL_DEFINE1(unshare, unsigned long, unshare_flags)
1738 struct fs_struct *fs, *new_fs = NULL;
1739 struct files_struct *fd, *new_fd = NULL;
1740 struct nsproxy *new_nsproxy = NULL;
1744 err = check_unshare_flags(unshare_flags);
1746 goto bad_unshare_out;
1749 * If unsharing namespace, must also unshare filesystem information.
1751 if (unshare_flags & CLONE_NEWNS)
1752 unshare_flags |= CLONE_FS;
1754 * CLONE_NEWIPC must also detach from the undolist: after switching
1755 * to a new ipc namespace, the semaphore arrays from the old
1756 * namespace are unreachable.
1758 if (unshare_flags & (CLONE_NEWIPC|CLONE_SYSVSEM))
1760 err = unshare_fs(unshare_flags, &new_fs);
1762 goto bad_unshare_out;
1763 err = unshare_fd(unshare_flags, &new_fd);
1765 goto bad_unshare_cleanup_fs;
1766 err = unshare_nsproxy_namespaces(unshare_flags, &new_nsproxy, new_fs);
1768 goto bad_unshare_cleanup_fd;
1770 if (new_fs || new_fd || do_sysvsem || new_nsproxy) {
1773 * CLONE_SYSVSEM is equivalent to sys_exit().
1779 switch_task_namespaces(current, new_nsproxy);
1787 spin_lock(&fs->lock);
1788 current->fs = new_fs;
1793 spin_unlock(&fs->lock);
1797 fd = current->files;
1798 current->files = new_fd;
1802 task_unlock(current);
1806 put_nsproxy(new_nsproxy);
1808 bad_unshare_cleanup_fd:
1810 put_files_struct(new_fd);
1812 bad_unshare_cleanup_fs:
1814 free_fs_struct(new_fs);
1821 * Helper to unshare the files of the current task.
1822 * We don't want to expose copy_files internals to
1823 * the exec layer of the kernel.
1826 int unshare_files(struct files_struct **displaced)
1828 struct task_struct *task = current;
1829 struct files_struct *copy = NULL;
1832 error = unshare_fd(CLONE_FILES, ©);
1833 if (error || !copy) {
1837 *displaced = task->files;