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>
32 #include <linux/vmacache.h>
33 #include <linux/nsproxy.h>
34 #include <linux/capability.h>
35 #include <linux/cpu.h>
36 #include <linux/cgroup.h>
37 #include <linux/security.h>
38 #include <linux/hugetlb.h>
39 #include <linux/seccomp.h>
40 #include <linux/swap.h>
41 #include <linux/syscalls.h>
42 #include <linux/jiffies.h>
43 #include <linux/futex.h>
44 #include <linux/compat.h>
45 #include <linux/kthread.h>
46 #include <linux/task_io_accounting_ops.h>
47 #include <linux/rcupdate.h>
48 #include <linux/ptrace.h>
49 #include <linux/mount.h>
50 #include <linux/audit.h>
51 #include <linux/memcontrol.h>
52 #include <linux/ftrace.h>
53 #include <linux/proc_fs.h>
54 #include <linux/profile.h>
55 #include <linux/rmap.h>
56 #include <linux/ksm.h>
57 #include <linux/acct.h>
58 #include <linux/tsacct_kern.h>
59 #include <linux/cn_proc.h>
60 #include <linux/freezer.h>
61 #include <linux/delayacct.h>
62 #include <linux/taskstats_kern.h>
63 #include <linux/random.h>
64 #include <linux/tty.h>
65 #include <linux/blkdev.h>
66 #include <linux/fs_struct.h>
67 #include <linux/magic.h>
68 #include <linux/perf_event.h>
69 #include <linux/posix-timers.h>
70 #include <linux/user-return-notifier.h>
71 #include <linux/oom.h>
72 #include <linux/khugepaged.h>
73 #include <linux/signalfd.h>
74 #include <linux/uprobes.h>
75 #include <linux/aio.h>
77 #include <asm/pgtable.h>
78 #include <asm/pgalloc.h>
79 #include <asm/uaccess.h>
80 #include <asm/mmu_context.h>
81 #include <asm/cacheflush.h>
82 #include <asm/tlbflush.h>
84 #include <trace/events/sched.h>
86 #define CREATE_TRACE_POINTS
87 #include <trace/events/task.h>
90 * Protected counters by write_lock_irq(&tasklist_lock)
92 unsigned long total_forks; /* Handle normal Linux uptimes. */
93 int nr_threads; /* The idle threads do not count.. */
95 int max_threads; /* tunable limit on nr_threads */
97 DEFINE_PER_CPU(unsigned long, process_counts) = 0;
99 __cacheline_aligned DEFINE_RWLOCK(tasklist_lock); /* outer */
101 #ifdef CONFIG_PROVE_RCU
102 int lockdep_tasklist_lock_is_held(void)
104 return lockdep_is_held(&tasklist_lock);
106 EXPORT_SYMBOL_GPL(lockdep_tasklist_lock_is_held);
107 #endif /* #ifdef CONFIG_PROVE_RCU */
109 int nr_processes(void)
114 for_each_possible_cpu(cpu)
115 total += per_cpu(process_counts, cpu);
120 void __weak arch_release_task_struct(struct task_struct *tsk)
124 #ifndef CONFIG_ARCH_TASK_STRUCT_ALLOCATOR
125 static struct kmem_cache *task_struct_cachep;
127 static inline struct task_struct *alloc_task_struct_node(int node)
129 return kmem_cache_alloc_node(task_struct_cachep, GFP_KERNEL, node);
132 static inline void free_task_struct(struct task_struct *tsk)
134 kmem_cache_free(task_struct_cachep, tsk);
138 void __weak arch_release_thread_info(struct thread_info *ti)
142 #ifndef CONFIG_ARCH_THREAD_INFO_ALLOCATOR
145 * Allocate pages if THREAD_SIZE is >= PAGE_SIZE, otherwise use a
146 * kmemcache based allocator.
148 # if THREAD_SIZE >= PAGE_SIZE
149 static struct thread_info *alloc_thread_info_node(struct task_struct *tsk,
152 struct page *page = alloc_pages_node(node, THREADINFO_GFP_ACCOUNTED,
155 return page ? page_address(page) : NULL;
158 static inline void free_thread_info(struct thread_info *ti)
160 free_memcg_kmem_pages((unsigned long)ti, THREAD_SIZE_ORDER);
163 static struct kmem_cache *thread_info_cache;
165 static struct thread_info *alloc_thread_info_node(struct task_struct *tsk,
168 return kmem_cache_alloc_node(thread_info_cache, THREADINFO_GFP, node);
171 static void free_thread_info(struct thread_info *ti)
173 kmem_cache_free(thread_info_cache, ti);
176 void thread_info_cache_init(void)
178 thread_info_cache = kmem_cache_create("thread_info", THREAD_SIZE,
179 THREAD_SIZE, 0, NULL);
180 BUG_ON(thread_info_cache == NULL);
185 /* SLAB cache for signal_struct structures (tsk->signal) */
186 static struct kmem_cache *signal_cachep;
188 /* SLAB cache for sighand_struct structures (tsk->sighand) */
189 struct kmem_cache *sighand_cachep;
191 /* SLAB cache for files_struct structures (tsk->files) */
192 struct kmem_cache *files_cachep;
194 /* SLAB cache for fs_struct structures (tsk->fs) */
195 struct kmem_cache *fs_cachep;
197 /* SLAB cache for vm_area_struct structures */
198 struct kmem_cache *vm_area_cachep;
200 /* SLAB cache for mm_struct structures (tsk->mm) */
201 static struct kmem_cache *mm_cachep;
203 static void account_kernel_stack(struct thread_info *ti, int account)
205 struct zone *zone = page_zone(virt_to_page(ti));
207 mod_zone_page_state(zone, NR_KERNEL_STACK, account);
210 void free_task(struct task_struct *tsk)
212 account_kernel_stack(tsk->stack, -1);
213 arch_release_thread_info(tsk->stack);
214 free_thread_info(tsk->stack);
215 rt_mutex_debug_task_free(tsk);
216 ftrace_graph_exit_task(tsk);
217 put_seccomp_filter(tsk);
218 arch_release_task_struct(tsk);
219 free_task_struct(tsk);
221 EXPORT_SYMBOL(free_task);
223 static inline void free_signal_struct(struct signal_struct *sig)
225 taskstats_tgid_free(sig);
226 sched_autogroup_exit(sig);
227 kmem_cache_free(signal_cachep, sig);
230 static inline void put_signal_struct(struct signal_struct *sig)
232 if (atomic_dec_and_test(&sig->sigcnt))
233 free_signal_struct(sig);
236 void __put_task_struct(struct task_struct *tsk)
238 WARN_ON(!tsk->exit_state);
239 WARN_ON(atomic_read(&tsk->usage));
240 WARN_ON(tsk == current);
242 security_task_free(tsk);
244 delayacct_tsk_free(tsk);
245 put_signal_struct(tsk->signal);
247 if (!profile_handoff_task(tsk))
250 EXPORT_SYMBOL_GPL(__put_task_struct);
252 void __init __weak arch_task_cache_init(void) { }
254 void __init fork_init(unsigned long mempages)
256 #ifndef CONFIG_ARCH_TASK_STRUCT_ALLOCATOR
257 #ifndef ARCH_MIN_TASKALIGN
258 #define ARCH_MIN_TASKALIGN L1_CACHE_BYTES
260 /* create a slab on which task_structs can be allocated */
262 kmem_cache_create("task_struct", sizeof(struct task_struct),
263 ARCH_MIN_TASKALIGN, SLAB_PANIC | SLAB_NOTRACK, NULL);
266 /* do the arch specific task caches init */
267 arch_task_cache_init();
270 * The default maximum number of threads is set to a safe
271 * value: the thread structures can take up at most half
274 max_threads = mempages / (8 * THREAD_SIZE / PAGE_SIZE);
277 * we need to allow at least 20 threads to boot a system
279 if (max_threads < 20)
282 init_task.signal->rlim[RLIMIT_NPROC].rlim_cur = max_threads/2;
283 init_task.signal->rlim[RLIMIT_NPROC].rlim_max = max_threads/2;
284 init_task.signal->rlim[RLIMIT_SIGPENDING] =
285 init_task.signal->rlim[RLIMIT_NPROC];
288 int __attribute__((weak)) arch_dup_task_struct(struct task_struct *dst,
289 struct task_struct *src)
295 static struct task_struct *dup_task_struct(struct task_struct *orig)
297 struct task_struct *tsk;
298 struct thread_info *ti;
299 unsigned long *stackend;
300 int node = tsk_fork_get_node(orig);
303 tsk = alloc_task_struct_node(node);
307 ti = alloc_thread_info_node(tsk, node);
311 err = arch_dup_task_struct(tsk, orig);
317 setup_thread_stack(tsk, orig);
318 clear_user_return_notifier(tsk);
319 clear_tsk_need_resched(tsk);
320 stackend = end_of_stack(tsk);
321 *stackend = STACK_END_MAGIC; /* for overflow detection */
323 #ifdef CONFIG_CC_STACKPROTECTOR
324 tsk->stack_canary = get_random_int();
328 * One for us, one for whoever does the "release_task()" (usually
331 atomic_set(&tsk->usage, 2);
332 #ifdef CONFIG_BLK_DEV_IO_TRACE
335 tsk->splice_pipe = NULL;
336 tsk->task_frag.page = NULL;
338 account_kernel_stack(ti, 1);
343 free_thread_info(ti);
345 free_task_struct(tsk);
350 static int dup_mmap(struct mm_struct *mm, struct mm_struct *oldmm)
352 struct vm_area_struct *mpnt, *tmp, *prev, **pprev;
353 struct rb_node **rb_link, *rb_parent;
355 unsigned long charge;
357 uprobe_start_dup_mmap();
358 down_write(&oldmm->mmap_sem);
359 flush_cache_dup_mm(oldmm);
360 uprobe_dup_mmap(oldmm, mm);
362 * Not linked in yet - no deadlock potential:
364 down_write_nested(&mm->mmap_sem, SINGLE_DEPTH_NESTING);
368 mm->vmacache_seqnum = 0;
370 cpumask_clear(mm_cpumask(mm));
372 rb_link = &mm->mm_rb.rb_node;
375 retval = ksm_fork(mm, oldmm);
378 retval = khugepaged_fork(mm, oldmm);
383 for (mpnt = oldmm->mmap; mpnt; mpnt = mpnt->vm_next) {
386 if (mpnt->vm_flags & VM_DONTCOPY) {
387 vm_stat_account(mm, mpnt->vm_flags, mpnt->vm_file,
392 if (mpnt->vm_flags & VM_ACCOUNT) {
393 unsigned long len = vma_pages(mpnt);
395 if (security_vm_enough_memory_mm(oldmm, len)) /* sic */
399 tmp = kmem_cache_alloc(vm_area_cachep, GFP_KERNEL);
403 INIT_LIST_HEAD(&tmp->anon_vma_chain);
404 retval = vma_dup_policy(mpnt, tmp);
406 goto fail_nomem_policy;
408 if (anon_vma_fork(tmp, mpnt))
409 goto fail_nomem_anon_vma_fork;
410 tmp->vm_flags &= ~VM_LOCKED;
411 tmp->vm_next = tmp->vm_prev = NULL;
414 struct inode *inode = file_inode(file);
415 struct address_space *mapping = file->f_mapping;
418 if (tmp->vm_flags & VM_DENYWRITE)
419 atomic_dec(&inode->i_writecount);
420 mutex_lock(&mapping->i_mmap_mutex);
421 if (tmp->vm_flags & VM_SHARED)
422 mapping->i_mmap_writable++;
423 flush_dcache_mmap_lock(mapping);
424 /* insert tmp into the share list, just after mpnt */
425 if (unlikely(tmp->vm_flags & VM_NONLINEAR))
426 vma_nonlinear_insert(tmp,
427 &mapping->i_mmap_nonlinear);
429 vma_interval_tree_insert_after(tmp, mpnt,
431 flush_dcache_mmap_unlock(mapping);
432 mutex_unlock(&mapping->i_mmap_mutex);
436 * Clear hugetlb-related page reserves for children. This only
437 * affects MAP_PRIVATE mappings. Faults generated by the child
438 * are not guaranteed to succeed, even if read-only
440 if (is_vm_hugetlb_page(tmp))
441 reset_vma_resv_huge_pages(tmp);
444 * Link in the new vma and copy the page table entries.
447 pprev = &tmp->vm_next;
451 __vma_link_rb(mm, tmp, rb_link, rb_parent);
452 rb_link = &tmp->vm_rb.rb_right;
453 rb_parent = &tmp->vm_rb;
456 retval = copy_page_range(mm, oldmm, mpnt);
458 if (tmp->vm_ops && tmp->vm_ops->open)
459 tmp->vm_ops->open(tmp);
464 /* a new mm has just been created */
465 arch_dup_mmap(oldmm, mm);
468 up_write(&mm->mmap_sem);
470 up_write(&oldmm->mmap_sem);
471 uprobe_end_dup_mmap();
473 fail_nomem_anon_vma_fork:
474 mpol_put(vma_policy(tmp));
476 kmem_cache_free(vm_area_cachep, tmp);
479 vm_unacct_memory(charge);
483 static inline int mm_alloc_pgd(struct mm_struct *mm)
485 mm->pgd = pgd_alloc(mm);
486 if (unlikely(!mm->pgd))
491 static inline void mm_free_pgd(struct mm_struct *mm)
493 pgd_free(mm, mm->pgd);
496 #define dup_mmap(mm, oldmm) (0)
497 #define mm_alloc_pgd(mm) (0)
498 #define mm_free_pgd(mm)
499 #endif /* CONFIG_MMU */
501 __cacheline_aligned_in_smp DEFINE_SPINLOCK(mmlist_lock);
503 #define allocate_mm() (kmem_cache_alloc(mm_cachep, GFP_KERNEL))
504 #define free_mm(mm) (kmem_cache_free(mm_cachep, (mm)))
506 static unsigned long default_dump_filter = MMF_DUMP_FILTER_DEFAULT;
508 static int __init coredump_filter_setup(char *s)
510 default_dump_filter =
511 (simple_strtoul(s, NULL, 0) << MMF_DUMP_FILTER_SHIFT) &
512 MMF_DUMP_FILTER_MASK;
516 __setup("coredump_filter=", coredump_filter_setup);
518 #include <linux/init_task.h>
520 static void mm_init_aio(struct mm_struct *mm)
523 spin_lock_init(&mm->ioctx_lock);
524 mm->ioctx_table = NULL;
528 static struct mm_struct *mm_init(struct mm_struct *mm, struct task_struct *p)
530 atomic_set(&mm->mm_users, 1);
531 atomic_set(&mm->mm_count, 1);
532 init_rwsem(&mm->mmap_sem);
533 INIT_LIST_HEAD(&mm->mmlist);
534 mm->flags = (current->mm) ?
535 (current->mm->flags & MMF_INIT_MASK) : default_dump_filter;
536 mm->core_state = NULL;
537 atomic_long_set(&mm->nr_ptes, 0);
538 memset(&mm->rss_stat, 0, sizeof(mm->rss_stat));
539 spin_lock_init(&mm->page_table_lock);
541 mm_init_owner(mm, p);
542 clear_tlb_flush_pending(mm);
544 if (likely(!mm_alloc_pgd(mm))) {
546 mmu_notifier_mm_init(mm);
554 static void check_mm(struct mm_struct *mm)
558 for (i = 0; i < NR_MM_COUNTERS; i++) {
559 long x = atomic_long_read(&mm->rss_stat.count[i]);
562 printk(KERN_ALERT "BUG: Bad rss-counter state "
563 "mm:%p idx:%d val:%ld\n", mm, i, x);
566 #if defined(CONFIG_TRANSPARENT_HUGEPAGE) && !USE_SPLIT_PMD_PTLOCKS
567 VM_BUG_ON(mm->pmd_huge_pte);
572 * Allocate and initialize an mm_struct.
574 struct mm_struct *mm_alloc(void)
576 struct mm_struct *mm;
582 memset(mm, 0, sizeof(*mm));
584 return mm_init(mm, current);
588 * Called when the last reference to the mm
589 * is dropped: either by a lazy thread or by
590 * mmput. Free the page directory and the mm.
592 void __mmdrop(struct mm_struct *mm)
594 BUG_ON(mm == &init_mm);
597 mmu_notifier_mm_destroy(mm);
601 EXPORT_SYMBOL_GPL(__mmdrop);
604 * Decrement the use count and release all resources for an mm.
606 void mmput(struct mm_struct *mm)
610 if (atomic_dec_and_test(&mm->mm_users)) {
611 uprobe_clear_state(mm);
614 khugepaged_exit(mm); /* must run before exit_mmap */
616 set_mm_exe_file(mm, NULL);
617 if (!list_empty(&mm->mmlist)) {
618 spin_lock(&mmlist_lock);
619 list_del(&mm->mmlist);
620 spin_unlock(&mmlist_lock);
623 module_put(mm->binfmt->module);
627 EXPORT_SYMBOL_GPL(mmput);
629 void set_mm_exe_file(struct mm_struct *mm, struct file *new_exe_file)
632 get_file(new_exe_file);
635 mm->exe_file = new_exe_file;
638 struct file *get_mm_exe_file(struct mm_struct *mm)
640 struct file *exe_file;
642 /* We need mmap_sem to protect against races with removal of exe_file */
643 down_read(&mm->mmap_sem);
644 exe_file = mm->exe_file;
647 up_read(&mm->mmap_sem);
651 static void dup_mm_exe_file(struct mm_struct *oldmm, struct mm_struct *newmm)
653 /* It's safe to write the exe_file pointer without exe_file_lock because
654 * this is called during fork when the task is not yet in /proc */
655 newmm->exe_file = get_mm_exe_file(oldmm);
659 * get_task_mm - acquire a reference to the task's mm
661 * Returns %NULL if the task has no mm. Checks PF_KTHREAD (meaning
662 * this kernel workthread has transiently adopted a user mm with use_mm,
663 * to do its AIO) is not set and if so returns a reference to it, after
664 * bumping up the use count. User must release the mm via mmput()
665 * after use. Typically used by /proc and ptrace.
667 struct mm_struct *get_task_mm(struct task_struct *task)
669 struct mm_struct *mm;
674 if (task->flags & PF_KTHREAD)
677 atomic_inc(&mm->mm_users);
682 EXPORT_SYMBOL_GPL(get_task_mm);
684 struct mm_struct *mm_access(struct task_struct *task, unsigned int mode)
686 struct mm_struct *mm;
689 err = mutex_lock_killable(&task->signal->cred_guard_mutex);
693 mm = get_task_mm(task);
694 if (mm && mm != current->mm &&
695 !ptrace_may_access(task, mode)) {
697 mm = ERR_PTR(-EACCES);
699 mutex_unlock(&task->signal->cred_guard_mutex);
704 static void complete_vfork_done(struct task_struct *tsk)
706 struct completion *vfork;
709 vfork = tsk->vfork_done;
711 tsk->vfork_done = NULL;
717 static int wait_for_vfork_done(struct task_struct *child,
718 struct completion *vfork)
722 freezer_do_not_count();
723 killed = wait_for_completion_killable(vfork);
728 child->vfork_done = NULL;
732 put_task_struct(child);
736 /* Please note the differences between mmput and mm_release.
737 * mmput is called whenever we stop holding onto a mm_struct,
738 * error success whatever.
740 * mm_release is called after a mm_struct has been removed
741 * from the current process.
743 * This difference is important for error handling, when we
744 * only half set up a mm_struct for a new process and need to restore
745 * the old one. Because we mmput the new mm_struct before
746 * restoring the old one. . .
747 * Eric Biederman 10 January 1998
749 void mm_release(struct task_struct *tsk, struct mm_struct *mm)
751 /* Get rid of any futexes when releasing the mm */
753 if (unlikely(tsk->robust_list)) {
754 exit_robust_list(tsk);
755 tsk->robust_list = NULL;
758 if (unlikely(tsk->compat_robust_list)) {
759 compat_exit_robust_list(tsk);
760 tsk->compat_robust_list = NULL;
763 if (unlikely(!list_empty(&tsk->pi_state_list)))
764 exit_pi_state_list(tsk);
767 uprobe_free_utask(tsk);
769 /* Get rid of any cached register state */
770 deactivate_mm(tsk, mm);
773 * If we're exiting normally, clear a user-space tid field if
774 * requested. We leave this alone when dying by signal, to leave
775 * the value intact in a core dump, and to save the unnecessary
776 * trouble, say, a killed vfork parent shouldn't touch this mm.
777 * Userland only wants this done for a sys_exit.
779 if (tsk->clear_child_tid) {
780 if (!(tsk->flags & PF_SIGNALED) &&
781 atomic_read(&mm->mm_users) > 1) {
783 * We don't check the error code - if userspace has
784 * not set up a proper pointer then tough luck.
786 put_user(0, tsk->clear_child_tid);
787 sys_futex(tsk->clear_child_tid, FUTEX_WAKE,
790 tsk->clear_child_tid = NULL;
794 * All done, finally we can wake up parent and return this mm to him.
795 * Also kthread_stop() uses this completion for synchronization.
798 complete_vfork_done(tsk);
802 * Allocate a new mm structure and copy contents from the
803 * mm structure of the passed in task structure.
805 static struct mm_struct *dup_mm(struct task_struct *tsk)
807 struct mm_struct *mm, *oldmm = current->mm;
814 memcpy(mm, oldmm, sizeof(*mm));
817 #if defined(CONFIG_TRANSPARENT_HUGEPAGE) && !USE_SPLIT_PMD_PTLOCKS
818 mm->pmd_huge_pte = NULL;
820 if (!mm_init(mm, tsk))
823 if (init_new_context(tsk, mm))
826 dup_mm_exe_file(oldmm, mm);
828 err = dup_mmap(mm, oldmm);
832 mm->hiwater_rss = get_mm_rss(mm);
833 mm->hiwater_vm = mm->total_vm;
835 if (mm->binfmt && !try_module_get(mm->binfmt->module))
841 /* don't put binfmt in mmput, we haven't got module yet */
850 * If init_new_context() failed, we cannot use mmput() to free the mm
851 * because it calls destroy_context()
858 static int copy_mm(unsigned long clone_flags, struct task_struct *tsk)
860 struct mm_struct *mm, *oldmm;
863 tsk->min_flt = tsk->maj_flt = 0;
864 tsk->nvcsw = tsk->nivcsw = 0;
865 #ifdef CONFIG_DETECT_HUNG_TASK
866 tsk->last_switch_count = tsk->nvcsw + tsk->nivcsw;
870 tsk->active_mm = NULL;
873 * Are we cloning a kernel thread?
875 * We need to steal a active VM for that..
881 /* initialize the new vmacache entries */
884 if (clone_flags & CLONE_VM) {
885 atomic_inc(&oldmm->mm_users);
904 static int copy_fs(unsigned long clone_flags, struct task_struct *tsk)
906 struct fs_struct *fs = current->fs;
907 if (clone_flags & CLONE_FS) {
908 /* tsk->fs is already what we want */
909 spin_lock(&fs->lock);
911 spin_unlock(&fs->lock);
915 spin_unlock(&fs->lock);
918 tsk->fs = copy_fs_struct(fs);
924 static int copy_files(unsigned long clone_flags, struct task_struct *tsk)
926 struct files_struct *oldf, *newf;
930 * A background process may not have any files ...
932 oldf = current->files;
936 if (clone_flags & CLONE_FILES) {
937 atomic_inc(&oldf->count);
941 newf = dup_fd(oldf, &error);
951 static int copy_io(unsigned long clone_flags, struct task_struct *tsk)
954 struct io_context *ioc = current->io_context;
955 struct io_context *new_ioc;
960 * Share io context with parent, if CLONE_IO is set
962 if (clone_flags & CLONE_IO) {
964 tsk->io_context = ioc;
965 } else if (ioprio_valid(ioc->ioprio)) {
966 new_ioc = get_task_io_context(tsk, GFP_KERNEL, NUMA_NO_NODE);
967 if (unlikely(!new_ioc))
970 new_ioc->ioprio = ioc->ioprio;
971 put_io_context(new_ioc);
977 static int copy_sighand(unsigned long clone_flags, struct task_struct *tsk)
979 struct sighand_struct *sig;
981 if (clone_flags & CLONE_SIGHAND) {
982 atomic_inc(¤t->sighand->count);
985 sig = kmem_cache_alloc(sighand_cachep, GFP_KERNEL);
986 rcu_assign_pointer(tsk->sighand, sig);
989 atomic_set(&sig->count, 1);
990 memcpy(sig->action, current->sighand->action, sizeof(sig->action));
994 void __cleanup_sighand(struct sighand_struct *sighand)
996 if (atomic_dec_and_test(&sighand->count)) {
997 signalfd_cleanup(sighand);
998 kmem_cache_free(sighand_cachep, sighand);
1004 * Initialize POSIX timer handling for a thread group.
1006 static void posix_cpu_timers_init_group(struct signal_struct *sig)
1008 unsigned long cpu_limit;
1010 /* Thread group counters. */
1011 thread_group_cputime_init(sig);
1013 cpu_limit = ACCESS_ONCE(sig->rlim[RLIMIT_CPU].rlim_cur);
1014 if (cpu_limit != RLIM_INFINITY) {
1015 sig->cputime_expires.prof_exp = secs_to_cputime(cpu_limit);
1016 sig->cputimer.running = 1;
1019 /* The timer lists. */
1020 INIT_LIST_HEAD(&sig->cpu_timers[0]);
1021 INIT_LIST_HEAD(&sig->cpu_timers[1]);
1022 INIT_LIST_HEAD(&sig->cpu_timers[2]);
1025 static int copy_signal(unsigned long clone_flags, struct task_struct *tsk)
1027 struct signal_struct *sig;
1029 if (clone_flags & CLONE_THREAD)
1032 sig = kmem_cache_zalloc(signal_cachep, GFP_KERNEL);
1037 sig->nr_threads = 1;
1038 atomic_set(&sig->live, 1);
1039 atomic_set(&sig->sigcnt, 1);
1041 /* list_add(thread_node, thread_head) without INIT_LIST_HEAD() */
1042 sig->thread_head = (struct list_head)LIST_HEAD_INIT(tsk->thread_node);
1043 tsk->thread_node = (struct list_head)LIST_HEAD_INIT(sig->thread_head);
1045 init_waitqueue_head(&sig->wait_chldexit);
1046 sig->curr_target = tsk;
1047 init_sigpending(&sig->shared_pending);
1048 INIT_LIST_HEAD(&sig->posix_timers);
1050 hrtimer_init(&sig->real_timer, CLOCK_MONOTONIC, HRTIMER_MODE_REL);
1051 sig->real_timer.function = it_real_fn;
1053 task_lock(current->group_leader);
1054 memcpy(sig->rlim, current->signal->rlim, sizeof sig->rlim);
1055 task_unlock(current->group_leader);
1057 posix_cpu_timers_init_group(sig);
1059 tty_audit_fork(sig);
1060 sched_autogroup_fork(sig);
1062 #ifdef CONFIG_CGROUPS
1063 init_rwsem(&sig->group_rwsem);
1066 sig->oom_score_adj = current->signal->oom_score_adj;
1067 sig->oom_score_adj_min = current->signal->oom_score_adj_min;
1069 sig->has_child_subreaper = current->signal->has_child_subreaper ||
1070 current->signal->is_child_subreaper;
1072 mutex_init(&sig->cred_guard_mutex);
1077 static void copy_flags(unsigned long clone_flags, struct task_struct *p)
1079 unsigned long new_flags = p->flags;
1081 new_flags &= ~(PF_SUPERPRIV | PF_WQ_WORKER);
1082 new_flags |= PF_FORKNOEXEC;
1083 p->flags = new_flags;
1086 SYSCALL_DEFINE1(set_tid_address, int __user *, tidptr)
1088 current->clear_child_tid = tidptr;
1090 return task_pid_vnr(current);
1093 static void rt_mutex_init_task(struct task_struct *p)
1095 raw_spin_lock_init(&p->pi_lock);
1096 #ifdef CONFIG_RT_MUTEXES
1097 p->pi_waiters = RB_ROOT;
1098 p->pi_waiters_leftmost = NULL;
1099 p->pi_blocked_on = NULL;
1100 p->pi_top_task = NULL;
1104 #ifdef CONFIG_MM_OWNER
1105 void mm_init_owner(struct mm_struct *mm, struct task_struct *p)
1109 #endif /* CONFIG_MM_OWNER */
1112 * Initialize POSIX timer handling for a single task.
1114 static void posix_cpu_timers_init(struct task_struct *tsk)
1116 tsk->cputime_expires.prof_exp = 0;
1117 tsk->cputime_expires.virt_exp = 0;
1118 tsk->cputime_expires.sched_exp = 0;
1119 INIT_LIST_HEAD(&tsk->cpu_timers[0]);
1120 INIT_LIST_HEAD(&tsk->cpu_timers[1]);
1121 INIT_LIST_HEAD(&tsk->cpu_timers[2]);
1125 init_task_pid(struct task_struct *task, enum pid_type type, struct pid *pid)
1127 task->pids[type].pid = pid;
1131 * This creates a new process as a copy of the old one,
1132 * but does not actually start it yet.
1134 * It copies the registers, and all the appropriate
1135 * parts of the process environment (as per the clone
1136 * flags). The actual kick-off is left to the caller.
1138 static struct task_struct *copy_process(unsigned long clone_flags,
1139 unsigned long stack_start,
1140 unsigned long stack_size,
1141 int __user *child_tidptr,
1146 struct task_struct *p;
1148 if ((clone_flags & (CLONE_NEWNS|CLONE_FS)) == (CLONE_NEWNS|CLONE_FS))
1149 return ERR_PTR(-EINVAL);
1151 if ((clone_flags & (CLONE_NEWUSER|CLONE_FS)) == (CLONE_NEWUSER|CLONE_FS))
1152 return ERR_PTR(-EINVAL);
1155 * Thread groups must share signals as well, and detached threads
1156 * can only be started up within the thread group.
1158 if ((clone_flags & CLONE_THREAD) && !(clone_flags & CLONE_SIGHAND))
1159 return ERR_PTR(-EINVAL);
1162 * Shared signal handlers imply shared VM. By way of the above,
1163 * thread groups also imply shared VM. Blocking this case allows
1164 * for various simplifications in other code.
1166 if ((clone_flags & CLONE_SIGHAND) && !(clone_flags & CLONE_VM))
1167 return ERR_PTR(-EINVAL);
1170 * Siblings of global init remain as zombies on exit since they are
1171 * not reaped by their parent (swapper). To solve this and to avoid
1172 * multi-rooted process trees, prevent global and container-inits
1173 * from creating siblings.
1175 if ((clone_flags & CLONE_PARENT) &&
1176 current->signal->flags & SIGNAL_UNKILLABLE)
1177 return ERR_PTR(-EINVAL);
1180 * If the new process will be in a different pid or user namespace
1181 * do not allow it to share a thread group or signal handlers or
1182 * parent with the forking task.
1184 if (clone_flags & CLONE_SIGHAND) {
1185 if ((clone_flags & (CLONE_NEWUSER | CLONE_NEWPID)) ||
1186 (task_active_pid_ns(current) !=
1187 current->nsproxy->pid_ns_for_children))
1188 return ERR_PTR(-EINVAL);
1191 retval = security_task_create(clone_flags);
1196 p = dup_task_struct(current);
1200 ftrace_graph_init_task(p);
1201 get_seccomp_filter(p);
1203 rt_mutex_init_task(p);
1205 #ifdef CONFIG_PROVE_LOCKING
1206 DEBUG_LOCKS_WARN_ON(!p->hardirqs_enabled);
1207 DEBUG_LOCKS_WARN_ON(!p->softirqs_enabled);
1210 if (atomic_read(&p->real_cred->user->processes) >=
1211 task_rlimit(p, RLIMIT_NPROC)) {
1212 if (p->real_cred->user != INIT_USER &&
1213 !capable(CAP_SYS_RESOURCE) && !capable(CAP_SYS_ADMIN))
1216 current->flags &= ~PF_NPROC_EXCEEDED;
1218 retval = copy_creds(p, clone_flags);
1223 * If multiple threads are within copy_process(), then this check
1224 * triggers too late. This doesn't hurt, the check is only there
1225 * to stop root fork bombs.
1228 if (nr_threads >= max_threads)
1229 goto bad_fork_cleanup_count;
1231 if (!try_module_get(task_thread_info(p)->exec_domain->module))
1232 goto bad_fork_cleanup_count;
1234 delayacct_tsk_init(p); /* Must remain after dup_task_struct() */
1235 copy_flags(clone_flags, p);
1236 INIT_LIST_HEAD(&p->children);
1237 INIT_LIST_HEAD(&p->sibling);
1238 rcu_copy_process(p);
1239 p->vfork_done = NULL;
1240 spin_lock_init(&p->alloc_lock);
1242 init_sigpending(&p->pending);
1244 p->utime = p->stime = p->gtime = 0;
1245 p->utimescaled = p->stimescaled = 0;
1246 #ifndef CONFIG_VIRT_CPU_ACCOUNTING_NATIVE
1247 p->prev_cputime.utime = p->prev_cputime.stime = 0;
1249 #ifdef CONFIG_VIRT_CPU_ACCOUNTING_GEN
1250 seqlock_init(&p->vtime_seqlock);
1252 p->vtime_snap_whence = VTIME_SLEEPING;
1255 #if defined(SPLIT_RSS_COUNTING)
1256 memset(&p->rss_stat, 0, sizeof(p->rss_stat));
1259 p->default_timer_slack_ns = current->timer_slack_ns;
1261 task_io_accounting_init(&p->ioac);
1262 acct_clear_integrals(p);
1264 posix_cpu_timers_init(p);
1266 do_posix_clock_monotonic_gettime(&p->start_time);
1267 p->real_start_time = p->start_time;
1268 monotonic_to_bootbased(&p->real_start_time);
1269 p->io_context = NULL;
1270 p->audit_context = NULL;
1271 if (clone_flags & CLONE_THREAD)
1272 threadgroup_change_begin(current);
1275 p->mempolicy = mpol_dup(p->mempolicy);
1276 if (IS_ERR(p->mempolicy)) {
1277 retval = PTR_ERR(p->mempolicy);
1278 p->mempolicy = NULL;
1279 goto bad_fork_cleanup_cgroup;
1281 mpol_fix_fork_child_flag(p);
1283 #ifdef CONFIG_CPUSETS
1284 p->cpuset_mem_spread_rotor = NUMA_NO_NODE;
1285 p->cpuset_slab_spread_rotor = NUMA_NO_NODE;
1286 seqcount_init(&p->mems_allowed_seq);
1288 #ifdef CONFIG_TRACE_IRQFLAGS
1290 p->hardirqs_enabled = 0;
1291 p->hardirq_enable_ip = 0;
1292 p->hardirq_enable_event = 0;
1293 p->hardirq_disable_ip = _THIS_IP_;
1294 p->hardirq_disable_event = 0;
1295 p->softirqs_enabled = 1;
1296 p->softirq_enable_ip = _THIS_IP_;
1297 p->softirq_enable_event = 0;
1298 p->softirq_disable_ip = 0;
1299 p->softirq_disable_event = 0;
1300 p->hardirq_context = 0;
1301 p->softirq_context = 0;
1303 #ifdef CONFIG_LOCKDEP
1304 p->lockdep_depth = 0; /* no locks held yet */
1305 p->curr_chain_key = 0;
1306 p->lockdep_recursion = 0;
1309 #ifdef CONFIG_DEBUG_MUTEXES
1310 p->blocked_on = NULL; /* not blocked yet */
1313 p->memcg_batch.do_batch = 0;
1314 p->memcg_batch.memcg = NULL;
1316 #ifdef CONFIG_BCACHE
1317 p->sequential_io = 0;
1318 p->sequential_io_avg = 0;
1321 /* Perform scheduler related setup. Assign this task to a CPU. */
1322 retval = sched_fork(clone_flags, p);
1324 goto bad_fork_cleanup_policy;
1326 retval = perf_event_init_task(p);
1328 goto bad_fork_cleanup_policy;
1329 retval = audit_alloc(p);
1331 goto bad_fork_cleanup_perf;
1332 /* copy all the process information */
1333 retval = copy_semundo(clone_flags, p);
1335 goto bad_fork_cleanup_audit;
1336 retval = copy_files(clone_flags, p);
1338 goto bad_fork_cleanup_semundo;
1339 retval = copy_fs(clone_flags, p);
1341 goto bad_fork_cleanup_files;
1342 retval = copy_sighand(clone_flags, p);
1344 goto bad_fork_cleanup_fs;
1345 retval = copy_signal(clone_flags, p);
1347 goto bad_fork_cleanup_sighand;
1348 retval = copy_mm(clone_flags, p);
1350 goto bad_fork_cleanup_signal;
1351 retval = copy_namespaces(clone_flags, p);
1353 goto bad_fork_cleanup_mm;
1354 retval = copy_io(clone_flags, p);
1356 goto bad_fork_cleanup_namespaces;
1357 retval = copy_thread(clone_flags, stack_start, stack_size, p);
1359 goto bad_fork_cleanup_io;
1361 if (pid != &init_struct_pid) {
1363 pid = alloc_pid(p->nsproxy->pid_ns_for_children);
1365 goto bad_fork_cleanup_io;
1368 p->set_child_tid = (clone_flags & CLONE_CHILD_SETTID) ? child_tidptr : NULL;
1370 * Clear TID on mm_release()?
1372 p->clear_child_tid = (clone_flags & CLONE_CHILD_CLEARTID) ? child_tidptr : NULL;
1377 p->robust_list = NULL;
1378 #ifdef CONFIG_COMPAT
1379 p->compat_robust_list = NULL;
1381 INIT_LIST_HEAD(&p->pi_state_list);
1382 p->pi_state_cache = NULL;
1385 * sigaltstack should be cleared when sharing the same VM
1387 if ((clone_flags & (CLONE_VM|CLONE_VFORK)) == CLONE_VM)
1388 p->sas_ss_sp = p->sas_ss_size = 0;
1391 * Syscall tracing and stepping should be turned off in the
1392 * child regardless of CLONE_PTRACE.
1394 user_disable_single_step(p);
1395 clear_tsk_thread_flag(p, TIF_SYSCALL_TRACE);
1396 #ifdef TIF_SYSCALL_EMU
1397 clear_tsk_thread_flag(p, TIF_SYSCALL_EMU);
1399 clear_all_latency_tracing(p);
1401 /* ok, now we should be set up.. */
1402 p->pid = pid_nr(pid);
1403 if (clone_flags & CLONE_THREAD) {
1404 p->exit_signal = -1;
1405 p->group_leader = current->group_leader;
1406 p->tgid = current->tgid;
1408 if (clone_flags & CLONE_PARENT)
1409 p->exit_signal = current->group_leader->exit_signal;
1411 p->exit_signal = (clone_flags & CSIGNAL);
1412 p->group_leader = p;
1417 p->nr_dirtied_pause = 128 >> (PAGE_SHIFT - 10);
1418 p->dirty_paused_when = 0;
1420 p->pdeath_signal = 0;
1421 INIT_LIST_HEAD(&p->thread_group);
1422 p->task_works = NULL;
1425 * Make it visible to the rest of the system, but dont wake it up yet.
1426 * Need tasklist lock for parent etc handling!
1428 write_lock_irq(&tasklist_lock);
1430 /* CLONE_PARENT re-uses the old parent */
1431 if (clone_flags & (CLONE_PARENT|CLONE_THREAD)) {
1432 p->real_parent = current->real_parent;
1433 p->parent_exec_id = current->parent_exec_id;
1435 p->real_parent = current;
1436 p->parent_exec_id = current->self_exec_id;
1439 spin_lock(¤t->sighand->siglock);
1442 * Process group and session signals need to be delivered to just the
1443 * parent before the fork or both the parent and the child after the
1444 * fork. Restart if a signal comes in before we add the new process to
1445 * it's process group.
1446 * A fatal signal pending means that current will exit, so the new
1447 * thread can't slip out of an OOM kill (or normal SIGKILL).
1449 recalc_sigpending();
1450 if (signal_pending(current)) {
1451 spin_unlock(¤t->sighand->siglock);
1452 write_unlock_irq(&tasklist_lock);
1453 retval = -ERESTARTNOINTR;
1454 goto bad_fork_free_pid;
1457 if (likely(p->pid)) {
1458 ptrace_init_task(p, (clone_flags & CLONE_PTRACE) || trace);
1460 init_task_pid(p, PIDTYPE_PID, pid);
1461 if (thread_group_leader(p)) {
1462 init_task_pid(p, PIDTYPE_PGID, task_pgrp(current));
1463 init_task_pid(p, PIDTYPE_SID, task_session(current));
1465 if (is_child_reaper(pid)) {
1466 ns_of_pid(pid)->child_reaper = p;
1467 p->signal->flags |= SIGNAL_UNKILLABLE;
1470 p->signal->leader_pid = pid;
1471 p->signal->tty = tty_kref_get(current->signal->tty);
1472 list_add_tail(&p->sibling, &p->real_parent->children);
1473 list_add_tail_rcu(&p->tasks, &init_task.tasks);
1474 attach_pid(p, PIDTYPE_PGID);
1475 attach_pid(p, PIDTYPE_SID);
1476 __this_cpu_inc(process_counts);
1478 current->signal->nr_threads++;
1479 atomic_inc(¤t->signal->live);
1480 atomic_inc(¤t->signal->sigcnt);
1481 list_add_tail_rcu(&p->thread_group,
1482 &p->group_leader->thread_group);
1483 list_add_tail_rcu(&p->thread_node,
1484 &p->signal->thread_head);
1486 attach_pid(p, PIDTYPE_PID);
1491 spin_unlock(¤t->sighand->siglock);
1492 syscall_tracepoint_update(p);
1493 write_unlock_irq(&tasklist_lock);
1495 proc_fork_connector(p);
1496 cgroup_post_fork(p);
1497 if (clone_flags & CLONE_THREAD)
1498 threadgroup_change_end(current);
1501 trace_task_newtask(p, clone_flags);
1502 uprobe_copy_process(p, clone_flags);
1507 if (pid != &init_struct_pid)
1509 bad_fork_cleanup_io:
1512 bad_fork_cleanup_namespaces:
1513 exit_task_namespaces(p);
1514 bad_fork_cleanup_mm:
1517 bad_fork_cleanup_signal:
1518 if (!(clone_flags & CLONE_THREAD))
1519 free_signal_struct(p->signal);
1520 bad_fork_cleanup_sighand:
1521 __cleanup_sighand(p->sighand);
1522 bad_fork_cleanup_fs:
1523 exit_fs(p); /* blocking */
1524 bad_fork_cleanup_files:
1525 exit_files(p); /* blocking */
1526 bad_fork_cleanup_semundo:
1528 bad_fork_cleanup_audit:
1530 bad_fork_cleanup_perf:
1531 perf_event_free_task(p);
1532 bad_fork_cleanup_policy:
1534 mpol_put(p->mempolicy);
1535 bad_fork_cleanup_cgroup:
1537 if (clone_flags & CLONE_THREAD)
1538 threadgroup_change_end(current);
1540 delayacct_tsk_free(p);
1541 module_put(task_thread_info(p)->exec_domain->module);
1542 bad_fork_cleanup_count:
1543 atomic_dec(&p->cred->user->processes);
1548 return ERR_PTR(retval);
1551 static inline void init_idle_pids(struct pid_link *links)
1555 for (type = PIDTYPE_PID; type < PIDTYPE_MAX; ++type) {
1556 INIT_HLIST_NODE(&links[type].node); /* not really needed */
1557 links[type].pid = &init_struct_pid;
1561 struct task_struct *fork_idle(int cpu)
1563 struct task_struct *task;
1564 task = copy_process(CLONE_VM, 0, 0, NULL, &init_struct_pid, 0);
1565 if (!IS_ERR(task)) {
1566 init_idle_pids(task->pids);
1567 init_idle(task, cpu);
1574 * Ok, this is the main fork-routine.
1576 * It copies the process, and if successful kick-starts
1577 * it and waits for it to finish using the VM if required.
1579 long do_fork(unsigned long clone_flags,
1580 unsigned long stack_start,
1581 unsigned long stack_size,
1582 int __user *parent_tidptr,
1583 int __user *child_tidptr)
1585 struct task_struct *p;
1590 * Determine whether and which event to report to ptracer. When
1591 * called from kernel_thread or CLONE_UNTRACED is explicitly
1592 * requested, no event is reported; otherwise, report if the event
1593 * for the type of forking is enabled.
1595 if (!(clone_flags & CLONE_UNTRACED)) {
1596 if (clone_flags & CLONE_VFORK)
1597 trace = PTRACE_EVENT_VFORK;
1598 else if ((clone_flags & CSIGNAL) != SIGCHLD)
1599 trace = PTRACE_EVENT_CLONE;
1601 trace = PTRACE_EVENT_FORK;
1603 if (likely(!ptrace_event_enabled(current, trace)))
1607 p = copy_process(clone_flags, stack_start, stack_size,
1608 child_tidptr, NULL, trace);
1610 * Do this prior waking up the new thread - the thread pointer
1611 * might get invalid after that point, if the thread exits quickly.
1614 struct completion vfork;
1617 trace_sched_process_fork(current, p);
1619 pid = get_task_pid(p, PIDTYPE_PID);
1622 if (clone_flags & CLONE_PARENT_SETTID)
1623 put_user(nr, parent_tidptr);
1625 if (clone_flags & CLONE_VFORK) {
1626 p->vfork_done = &vfork;
1627 init_completion(&vfork);
1631 wake_up_new_task(p);
1633 /* forking complete and child started to run, tell ptracer */
1634 if (unlikely(trace))
1635 ptrace_event_pid(trace, pid);
1637 if (clone_flags & CLONE_VFORK) {
1638 if (!wait_for_vfork_done(p, &vfork))
1639 ptrace_event_pid(PTRACE_EVENT_VFORK_DONE, pid);
1650 * Create a kernel thread.
1652 pid_t kernel_thread(int (*fn)(void *), void *arg, unsigned long flags)
1654 return do_fork(flags|CLONE_VM|CLONE_UNTRACED, (unsigned long)fn,
1655 (unsigned long)arg, NULL, NULL);
1658 #ifdef __ARCH_WANT_SYS_FORK
1659 SYSCALL_DEFINE0(fork)
1662 return do_fork(SIGCHLD, 0, 0, NULL, NULL);
1664 /* can not support in nommu mode */
1670 #ifdef __ARCH_WANT_SYS_VFORK
1671 SYSCALL_DEFINE0(vfork)
1673 return do_fork(CLONE_VFORK | CLONE_VM | SIGCHLD, 0,
1678 #ifdef __ARCH_WANT_SYS_CLONE
1679 #ifdef CONFIG_CLONE_BACKWARDS
1680 SYSCALL_DEFINE5(clone, unsigned long, clone_flags, unsigned long, newsp,
1681 int __user *, parent_tidptr,
1683 int __user *, child_tidptr)
1684 #elif defined(CONFIG_CLONE_BACKWARDS2)
1685 SYSCALL_DEFINE5(clone, unsigned long, newsp, unsigned long, clone_flags,
1686 int __user *, parent_tidptr,
1687 int __user *, child_tidptr,
1689 #elif defined(CONFIG_CLONE_BACKWARDS3)
1690 SYSCALL_DEFINE6(clone, unsigned long, clone_flags, unsigned long, newsp,
1692 int __user *, parent_tidptr,
1693 int __user *, child_tidptr,
1696 SYSCALL_DEFINE5(clone, unsigned long, clone_flags, unsigned long, newsp,
1697 int __user *, parent_tidptr,
1698 int __user *, child_tidptr,
1702 return do_fork(clone_flags, newsp, 0, parent_tidptr, child_tidptr);
1706 #ifndef ARCH_MIN_MMSTRUCT_ALIGN
1707 #define ARCH_MIN_MMSTRUCT_ALIGN 0
1710 static void sighand_ctor(void *data)
1712 struct sighand_struct *sighand = data;
1714 spin_lock_init(&sighand->siglock);
1715 init_waitqueue_head(&sighand->signalfd_wqh);
1718 void __init proc_caches_init(void)
1720 sighand_cachep = kmem_cache_create("sighand_cache",
1721 sizeof(struct sighand_struct), 0,
1722 SLAB_HWCACHE_ALIGN|SLAB_PANIC|SLAB_DESTROY_BY_RCU|
1723 SLAB_NOTRACK, sighand_ctor);
1724 signal_cachep = kmem_cache_create("signal_cache",
1725 sizeof(struct signal_struct), 0,
1726 SLAB_HWCACHE_ALIGN|SLAB_PANIC|SLAB_NOTRACK, NULL);
1727 files_cachep = kmem_cache_create("files_cache",
1728 sizeof(struct files_struct), 0,
1729 SLAB_HWCACHE_ALIGN|SLAB_PANIC|SLAB_NOTRACK, NULL);
1730 fs_cachep = kmem_cache_create("fs_cache",
1731 sizeof(struct fs_struct), 0,
1732 SLAB_HWCACHE_ALIGN|SLAB_PANIC|SLAB_NOTRACK, NULL);
1734 * FIXME! The "sizeof(struct mm_struct)" currently includes the
1735 * whole struct cpumask for the OFFSTACK case. We could change
1736 * this to *only* allocate as much of it as required by the
1737 * maximum number of CPU's we can ever have. The cpumask_allocation
1738 * is at the end of the structure, exactly for that reason.
1740 mm_cachep = kmem_cache_create("mm_struct",
1741 sizeof(struct mm_struct), ARCH_MIN_MMSTRUCT_ALIGN,
1742 SLAB_HWCACHE_ALIGN|SLAB_PANIC|SLAB_NOTRACK, NULL);
1743 vm_area_cachep = KMEM_CACHE(vm_area_struct, SLAB_PANIC);
1745 nsproxy_cache_init();
1749 * Check constraints on flags passed to the unshare system call.
1751 static int check_unshare_flags(unsigned long unshare_flags)
1753 if (unshare_flags & ~(CLONE_THREAD|CLONE_FS|CLONE_NEWNS|CLONE_SIGHAND|
1754 CLONE_VM|CLONE_FILES|CLONE_SYSVSEM|
1755 CLONE_NEWUTS|CLONE_NEWIPC|CLONE_NEWNET|
1756 CLONE_NEWUSER|CLONE_NEWPID))
1759 * Not implemented, but pretend it works if there is nothing to
1760 * unshare. Note that unsharing CLONE_THREAD or CLONE_SIGHAND
1761 * needs to unshare vm.
1763 if (unshare_flags & (CLONE_THREAD | CLONE_SIGHAND | CLONE_VM)) {
1764 /* FIXME: get_task_mm() increments ->mm_users */
1765 if (atomic_read(¤t->mm->mm_users) > 1)
1773 * Unshare the filesystem structure if it is being shared
1775 static int unshare_fs(unsigned long unshare_flags, struct fs_struct **new_fsp)
1777 struct fs_struct *fs = current->fs;
1779 if (!(unshare_flags & CLONE_FS) || !fs)
1782 /* don't need lock here; in the worst case we'll do useless copy */
1786 *new_fsp = copy_fs_struct(fs);
1794 * Unshare file descriptor table if it is being shared
1796 static int unshare_fd(unsigned long unshare_flags, struct files_struct **new_fdp)
1798 struct files_struct *fd = current->files;
1801 if ((unshare_flags & CLONE_FILES) &&
1802 (fd && atomic_read(&fd->count) > 1)) {
1803 *new_fdp = dup_fd(fd, &error);
1812 * unshare allows a process to 'unshare' part of the process
1813 * context which was originally shared using clone. copy_*
1814 * functions used by do_fork() cannot be used here directly
1815 * because they modify an inactive task_struct that is being
1816 * constructed. Here we are modifying the current, active,
1819 SYSCALL_DEFINE1(unshare, unsigned long, unshare_flags)
1821 struct fs_struct *fs, *new_fs = NULL;
1822 struct files_struct *fd, *new_fd = NULL;
1823 struct cred *new_cred = NULL;
1824 struct nsproxy *new_nsproxy = NULL;
1829 * If unsharing a user namespace must also unshare the thread.
1831 if (unshare_flags & CLONE_NEWUSER)
1832 unshare_flags |= CLONE_THREAD | CLONE_FS;
1834 * If unsharing a thread from a thread group, must also unshare vm.
1836 if (unshare_flags & CLONE_THREAD)
1837 unshare_flags |= CLONE_VM;
1839 * If unsharing vm, must also unshare signal handlers.
1841 if (unshare_flags & CLONE_VM)
1842 unshare_flags |= CLONE_SIGHAND;
1844 * If unsharing namespace, must also unshare filesystem information.
1846 if (unshare_flags & CLONE_NEWNS)
1847 unshare_flags |= CLONE_FS;
1849 err = check_unshare_flags(unshare_flags);
1851 goto bad_unshare_out;
1853 * CLONE_NEWIPC must also detach from the undolist: after switching
1854 * to a new ipc namespace, the semaphore arrays from the old
1855 * namespace are unreachable.
1857 if (unshare_flags & (CLONE_NEWIPC|CLONE_SYSVSEM))
1859 err = unshare_fs(unshare_flags, &new_fs);
1861 goto bad_unshare_out;
1862 err = unshare_fd(unshare_flags, &new_fd);
1864 goto bad_unshare_cleanup_fs;
1865 err = unshare_userns(unshare_flags, &new_cred);
1867 goto bad_unshare_cleanup_fd;
1868 err = unshare_nsproxy_namespaces(unshare_flags, &new_nsproxy,
1871 goto bad_unshare_cleanup_cred;
1873 if (new_fs || new_fd || do_sysvsem || new_cred || new_nsproxy) {
1876 * CLONE_SYSVSEM is equivalent to sys_exit().
1882 switch_task_namespaces(current, new_nsproxy);
1888 spin_lock(&fs->lock);
1889 current->fs = new_fs;
1894 spin_unlock(&fs->lock);
1898 fd = current->files;
1899 current->files = new_fd;
1903 task_unlock(current);
1906 /* Install the new user namespace */
1907 commit_creds(new_cred);
1912 bad_unshare_cleanup_cred:
1915 bad_unshare_cleanup_fd:
1917 put_files_struct(new_fd);
1919 bad_unshare_cleanup_fs:
1921 free_fs_struct(new_fs);
1928 * Helper to unshare the files of the current task.
1929 * We don't want to expose copy_files internals to
1930 * the exec layer of the kernel.
1933 int unshare_files(struct files_struct **displaced)
1935 struct task_struct *task = current;
1936 struct files_struct *copy = NULL;
1939 error = unshare_fd(CLONE_FILES, ©);
1940 if (error || !copy) {
1944 *displaced = task->files;