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>
76 #include <linux/compiler.h>
77 #include <linux/sysctl.h>
79 #include <asm/pgtable.h>
80 #include <asm/pgalloc.h>
81 #include <asm/uaccess.h>
82 #include <asm/mmu_context.h>
83 #include <asm/cacheflush.h>
84 #include <asm/tlbflush.h>
86 #include <trace/events/sched.h>
88 #define CREATE_TRACE_POINTS
89 #include <trace/events/task.h>
92 * Minimum number of threads to boot the kernel
94 #define MIN_THREADS 20
97 * Maximum number of threads
99 #define MAX_THREADS FUTEX_TID_MASK
102 * Protected counters by write_lock_irq(&tasklist_lock)
104 unsigned long total_forks; /* Handle normal Linux uptimes. */
105 int nr_threads; /* The idle threads do not count.. */
107 int max_threads; /* tunable limit on nr_threads */
109 DEFINE_PER_CPU(unsigned long, process_counts) = 0;
111 DEFINE_RWLOCK(tasklist_lock); /* outer */
113 #ifdef CONFIG_PROVE_RCU
114 int lockdep_tasklist_lock_is_held(void)
116 return lockdep_is_held(&tasklist_lock);
118 EXPORT_SYMBOL_GPL(lockdep_tasklist_lock_is_held);
119 #endif /* #ifdef CONFIG_PROVE_RCU */
121 int nr_processes(void)
126 for_each_possible_cpu(cpu)
127 total += per_cpu(process_counts, cpu);
132 void __weak arch_release_task_struct(struct task_struct *tsk)
136 #ifndef CONFIG_ARCH_TASK_STRUCT_ALLOCATOR
137 static struct kmem_cache *task_struct_cachep;
139 static inline struct task_struct *alloc_task_struct_node(int node)
141 return kmem_cache_alloc_node(task_struct_cachep, GFP_KERNEL, node);
144 static inline void free_task_struct(struct task_struct *tsk)
146 kmem_cache_free(task_struct_cachep, tsk);
150 void __weak arch_release_thread_info(struct thread_info *ti)
154 #ifndef CONFIG_ARCH_THREAD_INFO_ALLOCATOR
157 * Allocate pages if THREAD_SIZE is >= PAGE_SIZE, otherwise use a
158 * kmemcache based allocator.
160 # if THREAD_SIZE >= PAGE_SIZE
161 static struct thread_info *alloc_thread_info_node(struct task_struct *tsk,
164 struct page *page = alloc_kmem_pages_node(node, THREADINFO_GFP,
167 return page ? page_address(page) : NULL;
170 static inline void free_thread_info(struct thread_info *ti)
172 free_kmem_pages((unsigned long)ti, THREAD_SIZE_ORDER);
175 static struct kmem_cache *thread_info_cache;
177 static struct thread_info *alloc_thread_info_node(struct task_struct *tsk,
180 return kmem_cache_alloc_node(thread_info_cache, THREADINFO_GFP, node);
183 static void free_thread_info(struct thread_info *ti)
185 kmem_cache_free(thread_info_cache, ti);
188 void thread_info_cache_init(void)
190 thread_info_cache = kmem_cache_create("thread_info", THREAD_SIZE,
191 THREAD_SIZE, 0, NULL);
192 BUG_ON(thread_info_cache == NULL);
197 /* SLAB cache for signal_struct structures (tsk->signal) */
198 static struct kmem_cache *signal_cachep;
200 /* SLAB cache for sighand_struct structures (tsk->sighand) */
201 struct kmem_cache *sighand_cachep;
203 /* SLAB cache for files_struct structures (tsk->files) */
204 struct kmem_cache *files_cachep;
206 /* SLAB cache for fs_struct structures (tsk->fs) */
207 struct kmem_cache *fs_cachep;
209 /* SLAB cache for vm_area_struct structures */
210 struct kmem_cache *vm_area_cachep;
212 /* SLAB cache for mm_struct structures (tsk->mm) */
213 static struct kmem_cache *mm_cachep;
215 static void account_kernel_stack(struct thread_info *ti, int account)
217 struct zone *zone = page_zone(virt_to_page(ti));
219 mod_zone_page_state(zone, NR_KERNEL_STACK, account);
222 void free_task(struct task_struct *tsk)
224 account_kernel_stack(tsk->stack, -1);
225 arch_release_thread_info(tsk->stack);
226 free_thread_info(tsk->stack);
227 rt_mutex_debug_task_free(tsk);
228 ftrace_graph_exit_task(tsk);
229 put_seccomp_filter(tsk);
230 arch_release_task_struct(tsk);
231 free_task_struct(tsk);
233 EXPORT_SYMBOL(free_task);
235 static inline void free_signal_struct(struct signal_struct *sig)
237 taskstats_tgid_free(sig);
238 sched_autogroup_exit(sig);
239 kmem_cache_free(signal_cachep, sig);
242 static inline void put_signal_struct(struct signal_struct *sig)
244 if (atomic_dec_and_test(&sig->sigcnt))
245 free_signal_struct(sig);
247 #ifdef CONFIG_PREEMPT_RT_BASE
250 void __put_task_struct(struct task_struct *tsk)
252 WARN_ON(!tsk->exit_state);
253 WARN_ON(atomic_read(&tsk->usage));
254 WARN_ON(tsk == current);
258 security_task_free(tsk);
260 delayacct_tsk_free(tsk);
261 put_signal_struct(tsk->signal);
263 if (!profile_handoff_task(tsk))
266 #ifndef CONFIG_PREEMPT_RT_BASE
267 EXPORT_SYMBOL_GPL(__put_task_struct);
269 void __put_task_struct_cb(struct rcu_head *rhp)
271 struct task_struct *tsk = container_of(rhp, struct task_struct, put_rcu);
273 __put_task_struct(tsk);
276 EXPORT_SYMBOL_GPL(__put_task_struct_cb);
279 void __init __weak arch_task_cache_init(void) { }
284 static void set_max_threads(unsigned int max_threads_suggested)
289 * The number of threads shall be limited such that the thread
290 * structures may only consume a small part of the available memory.
292 if (fls64(totalram_pages) + fls64(PAGE_SIZE) > 64)
293 threads = MAX_THREADS;
295 threads = div64_u64((u64) totalram_pages * (u64) PAGE_SIZE,
296 (u64) THREAD_SIZE * 8UL);
298 if (threads > max_threads_suggested)
299 threads = max_threads_suggested;
301 max_threads = clamp_t(u64, threads, MIN_THREADS, MAX_THREADS);
304 #ifdef CONFIG_ARCH_WANTS_DYNAMIC_TASK_STRUCT
305 /* Initialized by the architecture: */
306 int arch_task_struct_size __read_mostly;
309 void __init fork_init(void)
311 #ifndef CONFIG_ARCH_TASK_STRUCT_ALLOCATOR
312 #ifndef ARCH_MIN_TASKALIGN
313 #define ARCH_MIN_TASKALIGN L1_CACHE_BYTES
315 /* create a slab on which task_structs can be allocated */
317 kmem_cache_create("task_struct", arch_task_struct_size,
318 ARCH_MIN_TASKALIGN, SLAB_PANIC | SLAB_NOTRACK, NULL);
321 /* do the arch specific task caches init */
322 arch_task_cache_init();
324 set_max_threads(MAX_THREADS);
326 init_task.signal->rlim[RLIMIT_NPROC].rlim_cur = max_threads/2;
327 init_task.signal->rlim[RLIMIT_NPROC].rlim_max = max_threads/2;
328 init_task.signal->rlim[RLIMIT_SIGPENDING] =
329 init_task.signal->rlim[RLIMIT_NPROC];
332 int __weak arch_dup_task_struct(struct task_struct *dst,
333 struct task_struct *src)
339 void set_task_stack_end_magic(struct task_struct *tsk)
341 unsigned long *stackend;
343 stackend = end_of_stack(tsk);
344 *stackend = STACK_END_MAGIC; /* for overflow detection */
347 static struct task_struct *dup_task_struct(struct task_struct *orig)
349 struct task_struct *tsk;
350 struct thread_info *ti;
351 int node = tsk_fork_get_node(orig);
354 tsk = alloc_task_struct_node(node);
358 ti = alloc_thread_info_node(tsk, node);
362 err = arch_dup_task_struct(tsk, orig);
367 #ifdef CONFIG_SECCOMP
369 * We must handle setting up seccomp filters once we're under
370 * the sighand lock in case orig has changed between now and
371 * then. Until then, filter must be NULL to avoid messing up
372 * the usage counts on the error path calling free_task.
374 tsk->seccomp.filter = NULL;
377 setup_thread_stack(tsk, orig);
378 clear_user_return_notifier(tsk);
379 clear_tsk_need_resched(tsk);
380 set_task_stack_end_magic(tsk);
382 #ifdef CONFIG_CC_STACKPROTECTOR
383 tsk->stack_canary = get_random_int();
387 * One for us, one for whoever does the "release_task()" (usually
390 atomic_set(&tsk->usage, 2);
391 #ifdef CONFIG_BLK_DEV_IO_TRACE
394 tsk->splice_pipe = NULL;
395 tsk->task_frag.page = NULL;
396 tsk->wake_q.next = NULL;
398 account_kernel_stack(ti, 1);
403 free_thread_info(ti);
405 free_task_struct(tsk);
410 static int dup_mmap(struct mm_struct *mm, struct mm_struct *oldmm)
412 struct vm_area_struct *mpnt, *tmp, *prev, **pprev;
413 struct rb_node **rb_link, *rb_parent;
415 unsigned long charge;
417 uprobe_start_dup_mmap();
418 down_write(&oldmm->mmap_sem);
419 flush_cache_dup_mm(oldmm);
420 uprobe_dup_mmap(oldmm, mm);
422 * Not linked in yet - no deadlock potential:
424 down_write_nested(&mm->mmap_sem, SINGLE_DEPTH_NESTING);
426 /* No ordering required: file already has been exposed. */
427 RCU_INIT_POINTER(mm->exe_file, get_mm_exe_file(oldmm));
429 mm->total_vm = oldmm->total_vm;
430 mm->shared_vm = oldmm->shared_vm;
431 mm->exec_vm = oldmm->exec_vm;
432 mm->stack_vm = oldmm->stack_vm;
434 rb_link = &mm->mm_rb.rb_node;
437 retval = ksm_fork(mm, oldmm);
440 retval = khugepaged_fork(mm, oldmm);
445 for (mpnt = oldmm->mmap; mpnt; mpnt = mpnt->vm_next) {
448 if (mpnt->vm_flags & VM_DONTCOPY) {
449 vm_stat_account(mm, mpnt->vm_flags, mpnt->vm_file,
454 if (mpnt->vm_flags & VM_ACCOUNT) {
455 unsigned long len = vma_pages(mpnt);
457 if (security_vm_enough_memory_mm(oldmm, len)) /* sic */
461 tmp = kmem_cache_alloc(vm_area_cachep, GFP_KERNEL);
465 INIT_LIST_HEAD(&tmp->anon_vma_chain);
466 retval = vma_dup_policy(mpnt, tmp);
468 goto fail_nomem_policy;
470 if (anon_vma_fork(tmp, mpnt))
471 goto fail_nomem_anon_vma_fork;
473 ~(VM_LOCKED|VM_LOCKONFAULT|VM_UFFD_MISSING|VM_UFFD_WP);
474 tmp->vm_next = tmp->vm_prev = NULL;
475 tmp->vm_userfaultfd_ctx = NULL_VM_UFFD_CTX;
478 struct inode *inode = file_inode(file);
479 struct address_space *mapping = file->f_mapping;
482 if (tmp->vm_flags & VM_DENYWRITE)
483 atomic_dec(&inode->i_writecount);
484 i_mmap_lock_write(mapping);
485 if (tmp->vm_flags & VM_SHARED)
486 atomic_inc(&mapping->i_mmap_writable);
487 flush_dcache_mmap_lock(mapping);
488 /* insert tmp into the share list, just after mpnt */
489 vma_interval_tree_insert_after(tmp, mpnt,
491 flush_dcache_mmap_unlock(mapping);
492 i_mmap_unlock_write(mapping);
496 * Clear hugetlb-related page reserves for children. This only
497 * affects MAP_PRIVATE mappings. Faults generated by the child
498 * are not guaranteed to succeed, even if read-only
500 if (is_vm_hugetlb_page(tmp))
501 reset_vma_resv_huge_pages(tmp);
504 * Link in the new vma and copy the page table entries.
507 pprev = &tmp->vm_next;
511 __vma_link_rb(mm, tmp, rb_link, rb_parent);
512 rb_link = &tmp->vm_rb.rb_right;
513 rb_parent = &tmp->vm_rb;
516 retval = copy_page_range(mm, oldmm, mpnt);
518 if (tmp->vm_ops && tmp->vm_ops->open)
519 tmp->vm_ops->open(tmp);
524 /* a new mm has just been created */
525 arch_dup_mmap(oldmm, mm);
528 up_write(&mm->mmap_sem);
530 up_write(&oldmm->mmap_sem);
531 uprobe_end_dup_mmap();
533 fail_nomem_anon_vma_fork:
534 mpol_put(vma_policy(tmp));
536 kmem_cache_free(vm_area_cachep, tmp);
539 vm_unacct_memory(charge);
543 static inline int mm_alloc_pgd(struct mm_struct *mm)
545 mm->pgd = pgd_alloc(mm);
546 if (unlikely(!mm->pgd))
551 static inline void mm_free_pgd(struct mm_struct *mm)
553 pgd_free(mm, mm->pgd);
556 static int dup_mmap(struct mm_struct *mm, struct mm_struct *oldmm)
558 down_write(&oldmm->mmap_sem);
559 RCU_INIT_POINTER(mm->exe_file, get_mm_exe_file(oldmm));
560 up_write(&oldmm->mmap_sem);
563 #define mm_alloc_pgd(mm) (0)
564 #define mm_free_pgd(mm)
565 #endif /* CONFIG_MMU */
567 __cacheline_aligned_in_smp DEFINE_SPINLOCK(mmlist_lock);
569 #define allocate_mm() (kmem_cache_alloc(mm_cachep, GFP_KERNEL))
570 #define free_mm(mm) (kmem_cache_free(mm_cachep, (mm)))
572 static unsigned long default_dump_filter = MMF_DUMP_FILTER_DEFAULT;
574 static int __init coredump_filter_setup(char *s)
576 default_dump_filter =
577 (simple_strtoul(s, NULL, 0) << MMF_DUMP_FILTER_SHIFT) &
578 MMF_DUMP_FILTER_MASK;
582 __setup("coredump_filter=", coredump_filter_setup);
584 #include <linux/init_task.h>
586 static void mm_init_aio(struct mm_struct *mm)
589 spin_lock_init(&mm->ioctx_lock);
590 mm->ioctx_table = NULL;
594 static void mm_init_owner(struct mm_struct *mm, struct task_struct *p)
601 static struct mm_struct *mm_init(struct mm_struct *mm, struct task_struct *p)
605 mm->vmacache_seqnum = 0;
606 atomic_set(&mm->mm_users, 1);
607 atomic_set(&mm->mm_count, 1);
608 init_rwsem(&mm->mmap_sem);
609 INIT_LIST_HEAD(&mm->mmlist);
610 mm->core_state = NULL;
611 atomic_long_set(&mm->nr_ptes, 0);
616 memset(&mm->rss_stat, 0, sizeof(mm->rss_stat));
617 spin_lock_init(&mm->page_table_lock);
620 mm_init_owner(mm, p);
621 mmu_notifier_mm_init(mm);
622 clear_tlb_flush_pending(mm);
623 #if defined(CONFIG_TRANSPARENT_HUGEPAGE) && !USE_SPLIT_PMD_PTLOCKS
624 mm->pmd_huge_pte = NULL;
628 mm->flags = current->mm->flags & MMF_INIT_MASK;
629 mm->def_flags = current->mm->def_flags & VM_INIT_DEF_MASK;
631 mm->flags = default_dump_filter;
635 if (mm_alloc_pgd(mm))
638 if (init_new_context(p, mm))
650 static void check_mm(struct mm_struct *mm)
654 for (i = 0; i < NR_MM_COUNTERS; i++) {
655 long x = atomic_long_read(&mm->rss_stat.count[i]);
658 printk(KERN_ALERT "BUG: Bad rss-counter state "
659 "mm:%p idx:%d val:%ld\n", mm, i, x);
662 if (atomic_long_read(&mm->nr_ptes))
663 pr_alert("BUG: non-zero nr_ptes on freeing mm: %ld\n",
664 atomic_long_read(&mm->nr_ptes));
666 pr_alert("BUG: non-zero nr_pmds on freeing mm: %ld\n",
669 #if defined(CONFIG_TRANSPARENT_HUGEPAGE) && !USE_SPLIT_PMD_PTLOCKS
670 VM_BUG_ON_MM(mm->pmd_huge_pte, mm);
675 * Allocate and initialize an mm_struct.
677 struct mm_struct *mm_alloc(void)
679 struct mm_struct *mm;
685 memset(mm, 0, sizeof(*mm));
686 return mm_init(mm, current);
690 * Called when the last reference to the mm
691 * is dropped: either by a lazy thread or by
692 * mmput. Free the page directory and the mm.
694 void __mmdrop(struct mm_struct *mm)
696 BUG_ON(mm == &init_mm);
699 mmu_notifier_mm_destroy(mm);
703 EXPORT_SYMBOL_GPL(__mmdrop);
705 #ifdef CONFIG_PREEMPT_RT_BASE
707 * RCU callback for delayed mm drop. Not strictly rcu, but we don't
708 * want another facility to make this work.
710 void __mmdrop_delayed(struct rcu_head *rhp)
712 struct mm_struct *mm = container_of(rhp, struct mm_struct, delayed_drop);
719 * Decrement the use count and release all resources for an mm.
721 void mmput(struct mm_struct *mm)
725 if (atomic_dec_and_test(&mm->mm_users)) {
726 uprobe_clear_state(mm);
729 khugepaged_exit(mm); /* must run before exit_mmap */
731 set_mm_exe_file(mm, NULL);
732 if (!list_empty(&mm->mmlist)) {
733 spin_lock(&mmlist_lock);
734 list_del(&mm->mmlist);
735 spin_unlock(&mmlist_lock);
738 module_put(mm->binfmt->module);
742 EXPORT_SYMBOL_GPL(mmput);
745 * set_mm_exe_file - change a reference to the mm's executable file
747 * This changes mm's executable file (shown as symlink /proc/[pid]/exe).
749 * Main users are mmput() and sys_execve(). Callers prevent concurrent
750 * invocations: in mmput() nobody alive left, in execve task is single
751 * threaded. sys_prctl(PR_SET_MM_MAP/EXE_FILE) also needs to set the
752 * mm->exe_file, but does so without using set_mm_exe_file() in order
753 * to do avoid the need for any locks.
755 void set_mm_exe_file(struct mm_struct *mm, struct file *new_exe_file)
757 struct file *old_exe_file;
760 * It is safe to dereference the exe_file without RCU as
761 * this function is only called if nobody else can access
762 * this mm -- see comment above for justification.
764 old_exe_file = rcu_dereference_raw(mm->exe_file);
767 get_file(new_exe_file);
768 rcu_assign_pointer(mm->exe_file, new_exe_file);
774 * get_mm_exe_file - acquire a reference to the mm's executable file
776 * Returns %NULL if mm has no associated executable file.
777 * User must release file via fput().
779 struct file *get_mm_exe_file(struct mm_struct *mm)
781 struct file *exe_file;
784 exe_file = rcu_dereference(mm->exe_file);
785 if (exe_file && !get_file_rcu(exe_file))
790 EXPORT_SYMBOL(get_mm_exe_file);
793 * get_task_mm - acquire a reference to the task's mm
795 * Returns %NULL if the task has no mm. Checks PF_KTHREAD (meaning
796 * this kernel workthread has transiently adopted a user mm with use_mm,
797 * to do its AIO) is not set and if so returns a reference to it, after
798 * bumping up the use count. User must release the mm via mmput()
799 * after use. Typically used by /proc and ptrace.
801 struct mm_struct *get_task_mm(struct task_struct *task)
803 struct mm_struct *mm;
808 if (task->flags & PF_KTHREAD)
811 atomic_inc(&mm->mm_users);
816 EXPORT_SYMBOL_GPL(get_task_mm);
818 struct mm_struct *mm_access(struct task_struct *task, unsigned int mode)
820 struct mm_struct *mm;
823 err = mutex_lock_killable(&task->signal->cred_guard_mutex);
827 mm = get_task_mm(task);
828 if (mm && mm != current->mm &&
829 !ptrace_may_access(task, mode)) {
831 mm = ERR_PTR(-EACCES);
833 mutex_unlock(&task->signal->cred_guard_mutex);
838 static void complete_vfork_done(struct task_struct *tsk)
840 struct completion *vfork;
843 vfork = tsk->vfork_done;
845 tsk->vfork_done = NULL;
851 static int wait_for_vfork_done(struct task_struct *child,
852 struct completion *vfork)
856 freezer_do_not_count();
857 killed = wait_for_completion_killable(vfork);
862 child->vfork_done = NULL;
866 put_task_struct(child);
870 /* Please note the differences between mmput and mm_release.
871 * mmput is called whenever we stop holding onto a mm_struct,
872 * error success whatever.
874 * mm_release is called after a mm_struct has been removed
875 * from the current process.
877 * This difference is important for error handling, when we
878 * only half set up a mm_struct for a new process and need to restore
879 * the old one. Because we mmput the new mm_struct before
880 * restoring the old one. . .
881 * Eric Biederman 10 January 1998
883 void mm_release(struct task_struct *tsk, struct mm_struct *mm)
885 /* Get rid of any futexes when releasing the mm */
887 if (unlikely(tsk->robust_list)) {
888 exit_robust_list(tsk);
889 tsk->robust_list = NULL;
892 if (unlikely(tsk->compat_robust_list)) {
893 compat_exit_robust_list(tsk);
894 tsk->compat_robust_list = NULL;
897 if (unlikely(!list_empty(&tsk->pi_state_list)))
898 exit_pi_state_list(tsk);
901 uprobe_free_utask(tsk);
903 /* Get rid of any cached register state */
904 deactivate_mm(tsk, mm);
907 * If we're exiting normally, clear a user-space tid field if
908 * requested. We leave this alone when dying by signal, to leave
909 * the value intact in a core dump, and to save the unnecessary
910 * trouble, say, a killed vfork parent shouldn't touch this mm.
911 * Userland only wants this done for a sys_exit.
913 if (tsk->clear_child_tid) {
914 if (!(tsk->flags & PF_SIGNALED) &&
915 atomic_read(&mm->mm_users) > 1) {
917 * We don't check the error code - if userspace has
918 * not set up a proper pointer then tough luck.
920 put_user(0, tsk->clear_child_tid);
921 sys_futex(tsk->clear_child_tid, FUTEX_WAKE,
924 tsk->clear_child_tid = NULL;
928 * All done, finally we can wake up parent and return this mm to him.
929 * Also kthread_stop() uses this completion for synchronization.
932 complete_vfork_done(tsk);
936 * Allocate a new mm structure and copy contents from the
937 * mm structure of the passed in task structure.
939 static struct mm_struct *dup_mm(struct task_struct *tsk)
941 struct mm_struct *mm, *oldmm = current->mm;
948 memcpy(mm, oldmm, sizeof(*mm));
950 if (!mm_init(mm, tsk))
953 err = dup_mmap(mm, oldmm);
957 mm->hiwater_rss = get_mm_rss(mm);
958 mm->hiwater_vm = mm->total_vm;
960 if (mm->binfmt && !try_module_get(mm->binfmt->module))
966 /* don't put binfmt in mmput, we haven't got module yet */
974 static int copy_mm(unsigned long clone_flags, struct task_struct *tsk)
976 struct mm_struct *mm, *oldmm;
979 tsk->min_flt = tsk->maj_flt = 0;
980 tsk->nvcsw = tsk->nivcsw = 0;
981 #ifdef CONFIG_DETECT_HUNG_TASK
982 tsk->last_switch_count = tsk->nvcsw + tsk->nivcsw;
986 tsk->active_mm = NULL;
989 * Are we cloning a kernel thread?
991 * We need to steal a active VM for that..
997 /* initialize the new vmacache entries */
1000 if (clone_flags & CLONE_VM) {
1001 atomic_inc(&oldmm->mm_users);
1013 tsk->active_mm = mm;
1020 static int copy_fs(unsigned long clone_flags, struct task_struct *tsk)
1022 struct fs_struct *fs = current->fs;
1023 if (clone_flags & CLONE_FS) {
1024 /* tsk->fs is already what we want */
1025 spin_lock(&fs->lock);
1027 spin_unlock(&fs->lock);
1031 spin_unlock(&fs->lock);
1034 tsk->fs = copy_fs_struct(fs);
1040 static int copy_files(unsigned long clone_flags, struct task_struct *tsk)
1042 struct files_struct *oldf, *newf;
1046 * A background process may not have any files ...
1048 oldf = current->files;
1052 if (clone_flags & CLONE_FILES) {
1053 atomic_inc(&oldf->count);
1057 newf = dup_fd(oldf, &error);
1067 static int copy_io(unsigned long clone_flags, struct task_struct *tsk)
1070 struct io_context *ioc = current->io_context;
1071 struct io_context *new_ioc;
1076 * Share io context with parent, if CLONE_IO is set
1078 if (clone_flags & CLONE_IO) {
1080 tsk->io_context = ioc;
1081 } else if (ioprio_valid(ioc->ioprio)) {
1082 new_ioc = get_task_io_context(tsk, GFP_KERNEL, NUMA_NO_NODE);
1083 if (unlikely(!new_ioc))
1086 new_ioc->ioprio = ioc->ioprio;
1087 put_io_context(new_ioc);
1093 static int copy_sighand(unsigned long clone_flags, struct task_struct *tsk)
1095 struct sighand_struct *sig;
1097 if (clone_flags & CLONE_SIGHAND) {
1098 atomic_inc(¤t->sighand->count);
1101 sig = kmem_cache_alloc(sighand_cachep, GFP_KERNEL);
1102 rcu_assign_pointer(tsk->sighand, sig);
1106 atomic_set(&sig->count, 1);
1107 memcpy(sig->action, current->sighand->action, sizeof(sig->action));
1111 void __cleanup_sighand(struct sighand_struct *sighand)
1113 if (atomic_dec_and_test(&sighand->count)) {
1114 signalfd_cleanup(sighand);
1116 * sighand_cachep is SLAB_DESTROY_BY_RCU so we can free it
1117 * without an RCU grace period, see __lock_task_sighand().
1119 kmem_cache_free(sighand_cachep, sighand);
1124 * Initialize POSIX timer handling for a thread group.
1126 static void posix_cpu_timers_init_group(struct signal_struct *sig)
1128 unsigned long cpu_limit;
1130 cpu_limit = READ_ONCE(sig->rlim[RLIMIT_CPU].rlim_cur);
1131 if (cpu_limit != RLIM_INFINITY) {
1132 sig->cputime_expires.prof_exp = secs_to_cputime(cpu_limit);
1133 sig->cputimer.running = true;
1136 /* The timer lists. */
1137 INIT_LIST_HEAD(&sig->cpu_timers[0]);
1138 INIT_LIST_HEAD(&sig->cpu_timers[1]);
1139 INIT_LIST_HEAD(&sig->cpu_timers[2]);
1142 static int copy_signal(unsigned long clone_flags, struct task_struct *tsk)
1144 struct signal_struct *sig;
1146 if (clone_flags & CLONE_THREAD)
1149 sig = kmem_cache_zalloc(signal_cachep, GFP_KERNEL);
1154 sig->nr_threads = 1;
1155 atomic_set(&sig->live, 1);
1156 atomic_set(&sig->sigcnt, 1);
1158 /* list_add(thread_node, thread_head) without INIT_LIST_HEAD() */
1159 sig->thread_head = (struct list_head)LIST_HEAD_INIT(tsk->thread_node);
1160 tsk->thread_node = (struct list_head)LIST_HEAD_INIT(sig->thread_head);
1162 init_waitqueue_head(&sig->wait_chldexit);
1163 sig->curr_target = tsk;
1164 init_sigpending(&sig->shared_pending);
1165 INIT_LIST_HEAD(&sig->posix_timers);
1166 seqlock_init(&sig->stats_lock);
1167 prev_cputime_init(&sig->prev_cputime);
1169 hrtimer_init(&sig->real_timer, CLOCK_MONOTONIC, HRTIMER_MODE_REL);
1170 sig->real_timer.function = it_real_fn;
1172 task_lock(current->group_leader);
1173 memcpy(sig->rlim, current->signal->rlim, sizeof sig->rlim);
1174 task_unlock(current->group_leader);
1176 posix_cpu_timers_init_group(sig);
1178 tty_audit_fork(sig);
1179 sched_autogroup_fork(sig);
1181 sig->oom_score_adj = current->signal->oom_score_adj;
1182 sig->oom_score_adj_min = current->signal->oom_score_adj_min;
1184 sig->has_child_subreaper = current->signal->has_child_subreaper ||
1185 current->signal->is_child_subreaper;
1187 mutex_init(&sig->cred_guard_mutex);
1192 static void copy_seccomp(struct task_struct *p)
1194 #ifdef CONFIG_SECCOMP
1196 * Must be called with sighand->lock held, which is common to
1197 * all threads in the group. Holding cred_guard_mutex is not
1198 * needed because this new task is not yet running and cannot
1201 assert_spin_locked(¤t->sighand->siglock);
1203 /* Ref-count the new filter user, and assign it. */
1204 get_seccomp_filter(current);
1205 p->seccomp = current->seccomp;
1208 * Explicitly enable no_new_privs here in case it got set
1209 * between the task_struct being duplicated and holding the
1210 * sighand lock. The seccomp state and nnp must be in sync.
1212 if (task_no_new_privs(current))
1213 task_set_no_new_privs(p);
1216 * If the parent gained a seccomp mode after copying thread
1217 * flags and between before we held the sighand lock, we have
1218 * to manually enable the seccomp thread flag here.
1220 if (p->seccomp.mode != SECCOMP_MODE_DISABLED)
1221 set_tsk_thread_flag(p, TIF_SECCOMP);
1225 SYSCALL_DEFINE1(set_tid_address, int __user *, tidptr)
1227 current->clear_child_tid = tidptr;
1229 return task_pid_vnr(current);
1232 static void rt_mutex_init_task(struct task_struct *p)
1234 raw_spin_lock_init(&p->pi_lock);
1235 #ifdef CONFIG_RT_MUTEXES
1236 p->pi_waiters = RB_ROOT;
1237 p->pi_waiters_leftmost = NULL;
1238 p->pi_blocked_on = NULL;
1243 * Initialize POSIX timer handling for a single task.
1245 static void posix_cpu_timers_init(struct task_struct *tsk)
1247 #ifdef CONFIG_PREEMPT_RT_BASE
1248 tsk->posix_timer_list = NULL;
1250 tsk->cputime_expires.prof_exp = 0;
1251 tsk->cputime_expires.virt_exp = 0;
1252 tsk->cputime_expires.sched_exp = 0;
1253 INIT_LIST_HEAD(&tsk->cpu_timers[0]);
1254 INIT_LIST_HEAD(&tsk->cpu_timers[1]);
1255 INIT_LIST_HEAD(&tsk->cpu_timers[2]);
1259 init_task_pid(struct task_struct *task, enum pid_type type, struct pid *pid)
1261 task->pids[type].pid = pid;
1265 * This creates a new process as a copy of the old one,
1266 * but does not actually start it yet.
1268 * It copies the registers, and all the appropriate
1269 * parts of the process environment (as per the clone
1270 * flags). The actual kick-off is left to the caller.
1272 static struct task_struct *copy_process(unsigned long clone_flags,
1273 unsigned long stack_start,
1274 unsigned long stack_size,
1275 int __user *child_tidptr,
1281 struct task_struct *p;
1282 void *cgrp_ss_priv[CGROUP_CANFORK_COUNT] = {};
1284 if ((clone_flags & (CLONE_NEWNS|CLONE_FS)) == (CLONE_NEWNS|CLONE_FS))
1285 return ERR_PTR(-EINVAL);
1287 if ((clone_flags & (CLONE_NEWUSER|CLONE_FS)) == (CLONE_NEWUSER|CLONE_FS))
1288 return ERR_PTR(-EINVAL);
1291 * Thread groups must share signals as well, and detached threads
1292 * can only be started up within the thread group.
1294 if ((clone_flags & CLONE_THREAD) && !(clone_flags & CLONE_SIGHAND))
1295 return ERR_PTR(-EINVAL);
1298 * Shared signal handlers imply shared VM. By way of the above,
1299 * thread groups also imply shared VM. Blocking this case allows
1300 * for various simplifications in other code.
1302 if ((clone_flags & CLONE_SIGHAND) && !(clone_flags & CLONE_VM))
1303 return ERR_PTR(-EINVAL);
1306 * Siblings of global init remain as zombies on exit since they are
1307 * not reaped by their parent (swapper). To solve this and to avoid
1308 * multi-rooted process trees, prevent global and container-inits
1309 * from creating siblings.
1311 if ((clone_flags & CLONE_PARENT) &&
1312 current->signal->flags & SIGNAL_UNKILLABLE)
1313 return ERR_PTR(-EINVAL);
1316 * If the new process will be in a different pid or user namespace
1317 * do not allow it to share a thread group with the forking task.
1319 if (clone_flags & CLONE_THREAD) {
1320 if ((clone_flags & (CLONE_NEWUSER | CLONE_NEWPID)) ||
1321 (task_active_pid_ns(current) !=
1322 current->nsproxy->pid_ns_for_children))
1323 return ERR_PTR(-EINVAL);
1326 retval = security_task_create(clone_flags);
1331 p = dup_task_struct(current);
1335 ftrace_graph_init_task(p);
1337 rt_mutex_init_task(p);
1339 #ifdef CONFIG_PROVE_LOCKING
1340 DEBUG_LOCKS_WARN_ON(!p->hardirqs_enabled);
1341 DEBUG_LOCKS_WARN_ON(!p->softirqs_enabled);
1344 if (atomic_read(&p->real_cred->user->processes) >=
1345 task_rlimit(p, RLIMIT_NPROC)) {
1346 if (p->real_cred->user != INIT_USER &&
1347 !capable(CAP_SYS_RESOURCE) && !capable(CAP_SYS_ADMIN))
1350 current->flags &= ~PF_NPROC_EXCEEDED;
1352 retval = copy_creds(p, clone_flags);
1357 * If multiple threads are within copy_process(), then this check
1358 * triggers too late. This doesn't hurt, the check is only there
1359 * to stop root fork bombs.
1362 if (nr_threads >= max_threads)
1363 goto bad_fork_cleanup_count;
1365 delayacct_tsk_init(p); /* Must remain after dup_task_struct() */
1366 p->flags &= ~(PF_SUPERPRIV | PF_WQ_WORKER);
1367 p->flags |= PF_FORKNOEXEC;
1368 INIT_LIST_HEAD(&p->children);
1369 INIT_LIST_HEAD(&p->sibling);
1370 rcu_copy_process(p);
1371 p->vfork_done = NULL;
1372 spin_lock_init(&p->alloc_lock);
1374 init_sigpending(&p->pending);
1375 p->sigqueue_cache = NULL;
1377 p->utime = p->stime = p->gtime = 0;
1378 p->utimescaled = p->stimescaled = 0;
1379 prev_cputime_init(&p->prev_cputime);
1381 #ifdef CONFIG_VIRT_CPU_ACCOUNTING_GEN
1382 raw_spin_lock_init(&p->vtime_lock);
1383 seqcount_init(&p->vtime_seq);
1385 p->vtime_snap_whence = VTIME_SLEEPING;
1388 #if defined(SPLIT_RSS_COUNTING)
1389 memset(&p->rss_stat, 0, sizeof(p->rss_stat));
1392 p->default_timer_slack_ns = current->timer_slack_ns;
1394 task_io_accounting_init(&p->ioac);
1395 acct_clear_integrals(p);
1397 posix_cpu_timers_init(p);
1399 p->start_time = ktime_get_ns();
1400 p->real_start_time = ktime_get_boot_ns();
1401 p->io_context = NULL;
1402 p->audit_context = NULL;
1403 threadgroup_change_begin(current);
1406 p->mempolicy = mpol_dup(p->mempolicy);
1407 if (IS_ERR(p->mempolicy)) {
1408 retval = PTR_ERR(p->mempolicy);
1409 p->mempolicy = NULL;
1410 goto bad_fork_cleanup_threadgroup_lock;
1413 #ifdef CONFIG_CPUSETS
1414 p->cpuset_mem_spread_rotor = NUMA_NO_NODE;
1415 p->cpuset_slab_spread_rotor = NUMA_NO_NODE;
1416 seqcount_init(&p->mems_allowed_seq);
1418 #ifdef CONFIG_TRACE_IRQFLAGS
1420 p->hardirqs_enabled = 0;
1421 p->hardirq_enable_ip = 0;
1422 p->hardirq_enable_event = 0;
1423 p->hardirq_disable_ip = _THIS_IP_;
1424 p->hardirq_disable_event = 0;
1425 p->softirqs_enabled = 1;
1426 p->softirq_enable_ip = _THIS_IP_;
1427 p->softirq_enable_event = 0;
1428 p->softirq_disable_ip = 0;
1429 p->softirq_disable_event = 0;
1430 p->hardirq_context = 0;
1431 p->softirq_context = 0;
1434 p->pagefault_disabled = 0;
1436 #ifdef CONFIG_LOCKDEP
1437 p->lockdep_depth = 0; /* no locks held yet */
1438 p->curr_chain_key = 0;
1439 p->lockdep_recursion = 0;
1442 #ifdef CONFIG_DEBUG_MUTEXES
1443 p->blocked_on = NULL; /* not blocked yet */
1445 #ifdef CONFIG_BCACHE
1446 p->sequential_io = 0;
1447 p->sequential_io_avg = 0;
1450 /* Perform scheduler related setup. Assign this task to a CPU. */
1451 retval = sched_fork(clone_flags, p);
1453 goto bad_fork_cleanup_policy;
1455 retval = perf_event_init_task(p);
1457 goto bad_fork_cleanup_policy;
1458 retval = audit_alloc(p);
1460 goto bad_fork_cleanup_perf;
1461 /* copy all the process information */
1463 retval = copy_semundo(clone_flags, p);
1465 goto bad_fork_cleanup_audit;
1466 retval = copy_files(clone_flags, p);
1468 goto bad_fork_cleanup_semundo;
1469 retval = copy_fs(clone_flags, p);
1471 goto bad_fork_cleanup_files;
1472 retval = copy_sighand(clone_flags, p);
1474 goto bad_fork_cleanup_fs;
1475 retval = copy_signal(clone_flags, p);
1477 goto bad_fork_cleanup_sighand;
1478 retval = copy_mm(clone_flags, p);
1480 goto bad_fork_cleanup_signal;
1481 retval = copy_namespaces(clone_flags, p);
1483 goto bad_fork_cleanup_mm;
1484 retval = copy_io(clone_flags, p);
1486 goto bad_fork_cleanup_namespaces;
1487 retval = copy_thread_tls(clone_flags, stack_start, stack_size, p, tls);
1489 goto bad_fork_cleanup_io;
1491 if (pid != &init_struct_pid) {
1492 pid = alloc_pid(p->nsproxy->pid_ns_for_children);
1494 retval = PTR_ERR(pid);
1495 goto bad_fork_cleanup_io;
1499 p->set_child_tid = (clone_flags & CLONE_CHILD_SETTID) ? child_tidptr : NULL;
1501 * Clear TID on mm_release()?
1503 p->clear_child_tid = (clone_flags & CLONE_CHILD_CLEARTID) ? child_tidptr : NULL;
1508 p->robust_list = NULL;
1509 #ifdef CONFIG_COMPAT
1510 p->compat_robust_list = NULL;
1512 INIT_LIST_HEAD(&p->pi_state_list);
1513 p->pi_state_cache = NULL;
1516 * sigaltstack should be cleared when sharing the same VM
1518 if ((clone_flags & (CLONE_VM|CLONE_VFORK)) == CLONE_VM)
1519 p->sas_ss_sp = p->sas_ss_size = 0;
1522 * Syscall tracing and stepping should be turned off in the
1523 * child regardless of CLONE_PTRACE.
1525 user_disable_single_step(p);
1526 clear_tsk_thread_flag(p, TIF_SYSCALL_TRACE);
1527 #ifdef TIF_SYSCALL_EMU
1528 clear_tsk_thread_flag(p, TIF_SYSCALL_EMU);
1530 clear_all_latency_tracing(p);
1532 /* ok, now we should be set up.. */
1533 p->pid = pid_nr(pid);
1534 if (clone_flags & CLONE_THREAD) {
1535 p->exit_signal = -1;
1536 p->group_leader = current->group_leader;
1537 p->tgid = current->tgid;
1539 if (clone_flags & CLONE_PARENT)
1540 p->exit_signal = current->group_leader->exit_signal;
1542 p->exit_signal = (clone_flags & CSIGNAL);
1543 p->group_leader = p;
1548 p->nr_dirtied_pause = 128 >> (PAGE_SHIFT - 10);
1549 p->dirty_paused_when = 0;
1551 p->pdeath_signal = 0;
1552 INIT_LIST_HEAD(&p->thread_group);
1553 p->task_works = NULL;
1556 * Ensure that the cgroup subsystem policies allow the new process to be
1557 * forked. It should be noted the the new process's css_set can be changed
1558 * between here and cgroup_post_fork() if an organisation operation is in
1561 retval = cgroup_can_fork(p, cgrp_ss_priv);
1563 goto bad_fork_free_pid;
1566 * Make it visible to the rest of the system, but dont wake it up yet.
1567 * Need tasklist lock for parent etc handling!
1569 write_lock_irq(&tasklist_lock);
1571 /* CLONE_PARENT re-uses the old parent */
1572 if (clone_flags & (CLONE_PARENT|CLONE_THREAD)) {
1573 p->real_parent = current->real_parent;
1574 p->parent_exec_id = current->parent_exec_id;
1576 p->real_parent = current;
1577 p->parent_exec_id = current->self_exec_id;
1580 spin_lock(¤t->sighand->siglock);
1583 * Copy seccomp details explicitly here, in case they were changed
1584 * before holding sighand lock.
1589 * Process group and session signals need to be delivered to just the
1590 * parent before the fork or both the parent and the child after the
1591 * fork. Restart if a signal comes in before we add the new process to
1592 * it's process group.
1593 * A fatal signal pending means that current will exit, so the new
1594 * thread can't slip out of an OOM kill (or normal SIGKILL).
1596 recalc_sigpending();
1597 if (signal_pending(current)) {
1598 spin_unlock(¤t->sighand->siglock);
1599 write_unlock_irq(&tasklist_lock);
1600 retval = -ERESTARTNOINTR;
1601 goto bad_fork_cancel_cgroup;
1604 if (likely(p->pid)) {
1605 ptrace_init_task(p, (clone_flags & CLONE_PTRACE) || trace);
1607 init_task_pid(p, PIDTYPE_PID, pid);
1608 if (thread_group_leader(p)) {
1609 init_task_pid(p, PIDTYPE_PGID, task_pgrp(current));
1610 init_task_pid(p, PIDTYPE_SID, task_session(current));
1612 if (is_child_reaper(pid)) {
1613 ns_of_pid(pid)->child_reaper = p;
1614 p->signal->flags |= SIGNAL_UNKILLABLE;
1617 p->signal->leader_pid = pid;
1618 p->signal->tty = tty_kref_get(current->signal->tty);
1619 list_add_tail(&p->sibling, &p->real_parent->children);
1620 list_add_tail_rcu(&p->tasks, &init_task.tasks);
1621 attach_pid(p, PIDTYPE_PGID);
1622 attach_pid(p, PIDTYPE_SID);
1623 __this_cpu_inc(process_counts);
1625 current->signal->nr_threads++;
1626 atomic_inc(¤t->signal->live);
1627 atomic_inc(¤t->signal->sigcnt);
1628 list_add_tail_rcu(&p->thread_group,
1629 &p->group_leader->thread_group);
1630 list_add_tail_rcu(&p->thread_node,
1631 &p->signal->thread_head);
1633 attach_pid(p, PIDTYPE_PID);
1638 spin_unlock(¤t->sighand->siglock);
1639 syscall_tracepoint_update(p);
1640 write_unlock_irq(&tasklist_lock);
1642 proc_fork_connector(p);
1643 cgroup_post_fork(p, cgrp_ss_priv);
1644 threadgroup_change_end(current);
1647 trace_task_newtask(p, clone_flags);
1648 uprobe_copy_process(p, clone_flags);
1652 bad_fork_cancel_cgroup:
1653 cgroup_cancel_fork(p, cgrp_ss_priv);
1655 if (pid != &init_struct_pid)
1657 bad_fork_cleanup_io:
1660 bad_fork_cleanup_namespaces:
1661 exit_task_namespaces(p);
1662 bad_fork_cleanup_mm:
1665 bad_fork_cleanup_signal:
1666 if (!(clone_flags & CLONE_THREAD))
1667 free_signal_struct(p->signal);
1668 bad_fork_cleanup_sighand:
1669 __cleanup_sighand(p->sighand);
1670 bad_fork_cleanup_fs:
1671 exit_fs(p); /* blocking */
1672 bad_fork_cleanup_files:
1673 exit_files(p); /* blocking */
1674 bad_fork_cleanup_semundo:
1676 bad_fork_cleanup_audit:
1678 bad_fork_cleanup_perf:
1679 perf_event_free_task(p);
1680 bad_fork_cleanup_policy:
1682 mpol_put(p->mempolicy);
1683 bad_fork_cleanup_threadgroup_lock:
1685 threadgroup_change_end(current);
1686 delayacct_tsk_free(p);
1687 bad_fork_cleanup_count:
1688 atomic_dec(&p->cred->user->processes);
1693 return ERR_PTR(retval);
1696 static inline void init_idle_pids(struct pid_link *links)
1700 for (type = PIDTYPE_PID; type < PIDTYPE_MAX; ++type) {
1701 INIT_HLIST_NODE(&links[type].node); /* not really needed */
1702 links[type].pid = &init_struct_pid;
1706 struct task_struct *fork_idle(int cpu)
1708 struct task_struct *task;
1709 task = copy_process(CLONE_VM, 0, 0, NULL, &init_struct_pid, 0, 0);
1710 if (!IS_ERR(task)) {
1711 init_idle_pids(task->pids);
1712 init_idle(task, cpu);
1719 * Ok, this is the main fork-routine.
1721 * It copies the process, and if successful kick-starts
1722 * it and waits for it to finish using the VM if required.
1724 long _do_fork(unsigned long clone_flags,
1725 unsigned long stack_start,
1726 unsigned long stack_size,
1727 int __user *parent_tidptr,
1728 int __user *child_tidptr,
1731 struct task_struct *p;
1736 * Determine whether and which event to report to ptracer. When
1737 * called from kernel_thread or CLONE_UNTRACED is explicitly
1738 * requested, no event is reported; otherwise, report if the event
1739 * for the type of forking is enabled.
1741 if (!(clone_flags & CLONE_UNTRACED)) {
1742 if (clone_flags & CLONE_VFORK)
1743 trace = PTRACE_EVENT_VFORK;
1744 else if ((clone_flags & CSIGNAL) != SIGCHLD)
1745 trace = PTRACE_EVENT_CLONE;
1747 trace = PTRACE_EVENT_FORK;
1749 if (likely(!ptrace_event_enabled(current, trace)))
1753 p = copy_process(clone_flags, stack_start, stack_size,
1754 child_tidptr, NULL, trace, tls);
1756 * Do this prior waking up the new thread - the thread pointer
1757 * might get invalid after that point, if the thread exits quickly.
1760 struct completion vfork;
1763 trace_sched_process_fork(current, p);
1765 pid = get_task_pid(p, PIDTYPE_PID);
1768 if (clone_flags & CLONE_PARENT_SETTID)
1769 put_user(nr, parent_tidptr);
1771 if (clone_flags & CLONE_VFORK) {
1772 p->vfork_done = &vfork;
1773 init_completion(&vfork);
1777 wake_up_new_task(p);
1779 /* forking complete and child started to run, tell ptracer */
1780 if (unlikely(trace))
1781 ptrace_event_pid(trace, pid);
1783 if (clone_flags & CLONE_VFORK) {
1784 if (!wait_for_vfork_done(p, &vfork))
1785 ptrace_event_pid(PTRACE_EVENT_VFORK_DONE, pid);
1795 #ifndef CONFIG_HAVE_COPY_THREAD_TLS
1796 /* For compatibility with architectures that call do_fork directly rather than
1797 * using the syscall entry points below. */
1798 long do_fork(unsigned long clone_flags,
1799 unsigned long stack_start,
1800 unsigned long stack_size,
1801 int __user *parent_tidptr,
1802 int __user *child_tidptr)
1804 return _do_fork(clone_flags, stack_start, stack_size,
1805 parent_tidptr, child_tidptr, 0);
1810 * Create a kernel thread.
1812 pid_t kernel_thread(int (*fn)(void *), void *arg, unsigned long flags)
1814 return _do_fork(flags|CLONE_VM|CLONE_UNTRACED, (unsigned long)fn,
1815 (unsigned long)arg, NULL, NULL, 0);
1818 #ifdef __ARCH_WANT_SYS_FORK
1819 SYSCALL_DEFINE0(fork)
1822 return _do_fork(SIGCHLD, 0, 0, NULL, NULL, 0);
1824 /* can not support in nommu mode */
1830 #ifdef __ARCH_WANT_SYS_VFORK
1831 SYSCALL_DEFINE0(vfork)
1833 return _do_fork(CLONE_VFORK | CLONE_VM | SIGCHLD, 0,
1838 #ifdef __ARCH_WANT_SYS_CLONE
1839 #ifdef CONFIG_CLONE_BACKWARDS
1840 SYSCALL_DEFINE5(clone, unsigned long, clone_flags, unsigned long, newsp,
1841 int __user *, parent_tidptr,
1843 int __user *, child_tidptr)
1844 #elif defined(CONFIG_CLONE_BACKWARDS2)
1845 SYSCALL_DEFINE5(clone, unsigned long, newsp, unsigned long, clone_flags,
1846 int __user *, parent_tidptr,
1847 int __user *, child_tidptr,
1849 #elif defined(CONFIG_CLONE_BACKWARDS3)
1850 SYSCALL_DEFINE6(clone, unsigned long, clone_flags, unsigned long, newsp,
1852 int __user *, parent_tidptr,
1853 int __user *, child_tidptr,
1856 SYSCALL_DEFINE5(clone, unsigned long, clone_flags, unsigned long, newsp,
1857 int __user *, parent_tidptr,
1858 int __user *, child_tidptr,
1862 return _do_fork(clone_flags, newsp, 0, parent_tidptr, child_tidptr, tls);
1866 #ifndef ARCH_MIN_MMSTRUCT_ALIGN
1867 #define ARCH_MIN_MMSTRUCT_ALIGN 0
1870 static void sighand_ctor(void *data)
1872 struct sighand_struct *sighand = data;
1874 spin_lock_init(&sighand->siglock);
1875 init_waitqueue_head(&sighand->signalfd_wqh);
1878 void __init proc_caches_init(void)
1880 sighand_cachep = kmem_cache_create("sighand_cache",
1881 sizeof(struct sighand_struct), 0,
1882 SLAB_HWCACHE_ALIGN|SLAB_PANIC|SLAB_DESTROY_BY_RCU|
1883 SLAB_NOTRACK, sighand_ctor);
1884 signal_cachep = kmem_cache_create("signal_cache",
1885 sizeof(struct signal_struct), 0,
1886 SLAB_HWCACHE_ALIGN|SLAB_PANIC|SLAB_NOTRACK, NULL);
1887 files_cachep = kmem_cache_create("files_cache",
1888 sizeof(struct files_struct), 0,
1889 SLAB_HWCACHE_ALIGN|SLAB_PANIC|SLAB_NOTRACK, NULL);
1890 fs_cachep = kmem_cache_create("fs_cache",
1891 sizeof(struct fs_struct), 0,
1892 SLAB_HWCACHE_ALIGN|SLAB_PANIC|SLAB_NOTRACK, NULL);
1894 * FIXME! The "sizeof(struct mm_struct)" currently includes the
1895 * whole struct cpumask for the OFFSTACK case. We could change
1896 * this to *only* allocate as much of it as required by the
1897 * maximum number of CPU's we can ever have. The cpumask_allocation
1898 * is at the end of the structure, exactly for that reason.
1900 mm_cachep = kmem_cache_create("mm_struct",
1901 sizeof(struct mm_struct), ARCH_MIN_MMSTRUCT_ALIGN,
1902 SLAB_HWCACHE_ALIGN|SLAB_PANIC|SLAB_NOTRACK, NULL);
1903 vm_area_cachep = KMEM_CACHE(vm_area_struct, SLAB_PANIC);
1905 nsproxy_cache_init();
1909 * Check constraints on flags passed to the unshare system call.
1911 static int check_unshare_flags(unsigned long unshare_flags)
1913 if (unshare_flags & ~(CLONE_THREAD|CLONE_FS|CLONE_NEWNS|CLONE_SIGHAND|
1914 CLONE_VM|CLONE_FILES|CLONE_SYSVSEM|
1915 CLONE_NEWUTS|CLONE_NEWIPC|CLONE_NEWNET|
1916 CLONE_NEWUSER|CLONE_NEWPID))
1919 * Not implemented, but pretend it works if there is nothing
1920 * to unshare. Note that unsharing the address space or the
1921 * signal handlers also need to unshare the signal queues (aka
1924 if (unshare_flags & (CLONE_THREAD | CLONE_SIGHAND | CLONE_VM)) {
1925 if (!thread_group_empty(current))
1928 if (unshare_flags & (CLONE_SIGHAND | CLONE_VM)) {
1929 if (atomic_read(¤t->sighand->count) > 1)
1932 if (unshare_flags & CLONE_VM) {
1933 if (!current_is_single_threaded())
1941 * Unshare the filesystem structure if it is being shared
1943 static int unshare_fs(unsigned long unshare_flags, struct fs_struct **new_fsp)
1945 struct fs_struct *fs = current->fs;
1947 if (!(unshare_flags & CLONE_FS) || !fs)
1950 /* don't need lock here; in the worst case we'll do useless copy */
1954 *new_fsp = copy_fs_struct(fs);
1962 * Unshare file descriptor table if it is being shared
1964 static int unshare_fd(unsigned long unshare_flags, struct files_struct **new_fdp)
1966 struct files_struct *fd = current->files;
1969 if ((unshare_flags & CLONE_FILES) &&
1970 (fd && atomic_read(&fd->count) > 1)) {
1971 *new_fdp = dup_fd(fd, &error);
1980 * unshare allows a process to 'unshare' part of the process
1981 * context which was originally shared using clone. copy_*
1982 * functions used by do_fork() cannot be used here directly
1983 * because they modify an inactive task_struct that is being
1984 * constructed. Here we are modifying the current, active,
1987 SYSCALL_DEFINE1(unshare, unsigned long, unshare_flags)
1989 struct fs_struct *fs, *new_fs = NULL;
1990 struct files_struct *fd, *new_fd = NULL;
1991 struct cred *new_cred = NULL;
1992 struct nsproxy *new_nsproxy = NULL;
1997 * If unsharing a user namespace must also unshare the thread group
1998 * and unshare the filesystem root and working directories.
2000 if (unshare_flags & CLONE_NEWUSER)
2001 unshare_flags |= CLONE_THREAD | CLONE_FS;
2003 * If unsharing vm, must also unshare signal handlers.
2005 if (unshare_flags & CLONE_VM)
2006 unshare_flags |= CLONE_SIGHAND;
2008 * If unsharing a signal handlers, must also unshare the signal queues.
2010 if (unshare_flags & CLONE_SIGHAND)
2011 unshare_flags |= CLONE_THREAD;
2013 * If unsharing namespace, must also unshare filesystem information.
2015 if (unshare_flags & CLONE_NEWNS)
2016 unshare_flags |= CLONE_FS;
2018 err = check_unshare_flags(unshare_flags);
2020 goto bad_unshare_out;
2022 * CLONE_NEWIPC must also detach from the undolist: after switching
2023 * to a new ipc namespace, the semaphore arrays from the old
2024 * namespace are unreachable.
2026 if (unshare_flags & (CLONE_NEWIPC|CLONE_SYSVSEM))
2028 err = unshare_fs(unshare_flags, &new_fs);
2030 goto bad_unshare_out;
2031 err = unshare_fd(unshare_flags, &new_fd);
2033 goto bad_unshare_cleanup_fs;
2034 err = unshare_userns(unshare_flags, &new_cred);
2036 goto bad_unshare_cleanup_fd;
2037 err = unshare_nsproxy_namespaces(unshare_flags, &new_nsproxy,
2040 goto bad_unshare_cleanup_cred;
2042 if (new_fs || new_fd || do_sysvsem || new_cred || new_nsproxy) {
2045 * CLONE_SYSVSEM is equivalent to sys_exit().
2049 if (unshare_flags & CLONE_NEWIPC) {
2050 /* Orphan segments in old ns (see sem above). */
2052 shm_init_task(current);
2056 switch_task_namespaces(current, new_nsproxy);
2062 spin_lock(&fs->lock);
2063 current->fs = new_fs;
2068 spin_unlock(&fs->lock);
2072 fd = current->files;
2073 current->files = new_fd;
2077 task_unlock(current);
2080 /* Install the new user namespace */
2081 commit_creds(new_cred);
2086 bad_unshare_cleanup_cred:
2089 bad_unshare_cleanup_fd:
2091 put_files_struct(new_fd);
2093 bad_unshare_cleanup_fs:
2095 free_fs_struct(new_fs);
2102 * Helper to unshare the files of the current task.
2103 * We don't want to expose copy_files internals to
2104 * the exec layer of the kernel.
2107 int unshare_files(struct files_struct **displaced)
2109 struct task_struct *task = current;
2110 struct files_struct *copy = NULL;
2113 error = unshare_fd(CLONE_FILES, ©);
2114 if (error || !copy) {
2118 *displaced = task->files;
2125 int sysctl_max_threads(struct ctl_table *table, int write,
2126 void __user *buffer, size_t *lenp, loff_t *ppos)
2130 int threads = max_threads;
2131 int min = MIN_THREADS;
2132 int max = MAX_THREADS;
2139 ret = proc_dointvec_minmax(&t, write, buffer, lenp, ppos);
2143 set_max_threads(threads);