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/kaiser.h>
62 #include <linux/delayacct.h>
63 #include <linux/taskstats_kern.h>
64 #include <linux/random.h>
65 #include <linux/tty.h>
66 #include <linux/blkdev.h>
67 #include <linux/fs_struct.h>
68 #include <linux/magic.h>
69 #include <linux/perf_event.h>
70 #include <linux/posix-timers.h>
71 #include <linux/user-return-notifier.h>
72 #include <linux/oom.h>
73 #include <linux/khugepaged.h>
74 #include <linux/signalfd.h>
75 #include <linux/uprobes.h>
76 #include <linux/aio.h>
77 #include <linux/compiler.h>
78 #include <linux/sysctl.h>
79 #include <linux/kcov.h>
81 #include <asm/pgtable.h>
82 #include <asm/pgalloc.h>
83 #include <asm/uaccess.h>
84 #include <asm/mmu_context.h>
85 #include <asm/cacheflush.h>
86 #include <asm/tlbflush.h>
88 #include <trace/events/sched.h>
90 #define CREATE_TRACE_POINTS
91 #include <trace/events/task.h>
94 * Minimum number of threads to boot the kernel
96 #define MIN_THREADS 20
99 * Maximum number of threads
101 #define MAX_THREADS FUTEX_TID_MASK
104 * Protected counters by write_lock_irq(&tasklist_lock)
106 unsigned long total_forks; /* Handle normal Linux uptimes. */
107 int nr_threads; /* The idle threads do not count.. */
109 int max_threads; /* tunable limit on nr_threads */
111 DEFINE_PER_CPU(unsigned long, process_counts) = 0;
113 __cacheline_aligned DEFINE_RWLOCK(tasklist_lock); /* outer */
115 #ifdef CONFIG_PROVE_RCU
116 int lockdep_tasklist_lock_is_held(void)
118 return lockdep_is_held(&tasklist_lock);
120 EXPORT_SYMBOL_GPL(lockdep_tasklist_lock_is_held);
121 #endif /* #ifdef CONFIG_PROVE_RCU */
123 int nr_processes(void)
128 for_each_possible_cpu(cpu)
129 total += per_cpu(process_counts, cpu);
134 void __weak arch_release_task_struct(struct task_struct *tsk)
138 #ifndef CONFIG_ARCH_TASK_STRUCT_ALLOCATOR
139 static struct kmem_cache *task_struct_cachep;
141 static inline struct task_struct *alloc_task_struct_node(int node)
143 return kmem_cache_alloc_node(task_struct_cachep, GFP_KERNEL, node);
146 static inline void free_task_struct(struct task_struct *tsk)
148 kmem_cache_free(task_struct_cachep, tsk);
152 void __weak arch_release_thread_stack(unsigned long *stack)
156 #ifndef CONFIG_ARCH_THREAD_STACK_ALLOCATOR
159 * Allocate pages if THREAD_SIZE is >= PAGE_SIZE, otherwise use a
160 * kmemcache based allocator.
162 # if THREAD_SIZE >= PAGE_SIZE || defined(CONFIG_VMAP_STACK)
164 #ifdef CONFIG_VMAP_STACK
166 * vmalloc() is a bit slow, and calling vfree() enough times will force a TLB
167 * flush. Try to minimize the number of calls by caching stacks.
169 #define NR_CACHED_STACKS 2
170 static DEFINE_PER_CPU(struct vm_struct *, cached_stacks[NR_CACHED_STACKS]);
173 static unsigned long *alloc_thread_stack_node(struct task_struct *tsk, int node)
175 #ifdef CONFIG_VMAP_STACK
180 for (i = 0; i < NR_CACHED_STACKS; i++) {
181 struct vm_struct *s = this_cpu_read(cached_stacks[i]);
185 this_cpu_write(cached_stacks[i], NULL);
187 /* Clear stale pointers from reused stack. */
188 memset(s->addr, 0, THREAD_SIZE);
190 tsk->stack_vm_area = s;
196 stack = __vmalloc_node_range(THREAD_SIZE, THREAD_SIZE,
197 VMALLOC_START, VMALLOC_END,
198 THREADINFO_GFP | __GFP_HIGHMEM,
200 0, node, __builtin_return_address(0));
203 * We can't call find_vm_area() in interrupt context, and
204 * free_thread_stack() can be called in interrupt context,
205 * so cache the vm_struct.
208 tsk->stack_vm_area = find_vm_area(stack);
211 struct page *page = alloc_pages_node(node, THREADINFO_GFP,
214 return page ? page_address(page) : NULL;
218 static inline void free_thread_stack(struct task_struct *tsk)
220 kaiser_unmap_thread_stack(tsk->stack);
221 #ifdef CONFIG_VMAP_STACK
222 if (task_stack_vm_area(tsk)) {
226 local_irq_save(flags);
227 for (i = 0; i < NR_CACHED_STACKS; i++) {
228 if (this_cpu_read(cached_stacks[i]))
231 this_cpu_write(cached_stacks[i], tsk->stack_vm_area);
232 local_irq_restore(flags);
235 local_irq_restore(flags);
242 __free_pages(virt_to_page(tsk->stack), THREAD_SIZE_ORDER);
245 static struct kmem_cache *thread_stack_cache;
247 static unsigned long *alloc_thread_stack_node(struct task_struct *tsk,
250 return kmem_cache_alloc_node(thread_stack_cache, THREADINFO_GFP, node);
253 static void free_thread_stack(struct task_struct *tsk)
255 kmem_cache_free(thread_stack_cache, tsk->stack);
258 void thread_stack_cache_init(void)
260 thread_stack_cache = kmem_cache_create("thread_stack", THREAD_SIZE,
261 THREAD_SIZE, 0, NULL);
262 BUG_ON(thread_stack_cache == NULL);
267 /* SLAB cache for signal_struct structures (tsk->signal) */
268 static struct kmem_cache *signal_cachep;
270 /* SLAB cache for sighand_struct structures (tsk->sighand) */
271 struct kmem_cache *sighand_cachep;
273 /* SLAB cache for files_struct structures (tsk->files) */
274 struct kmem_cache *files_cachep;
276 /* SLAB cache for fs_struct structures (tsk->fs) */
277 struct kmem_cache *fs_cachep;
279 /* SLAB cache for vm_area_struct structures */
280 struct kmem_cache *vm_area_cachep;
282 /* SLAB cache for mm_struct structures (tsk->mm) */
283 static struct kmem_cache *mm_cachep;
285 static void account_kernel_stack(struct task_struct *tsk, int account)
287 void *stack = task_stack_page(tsk);
288 struct vm_struct *vm = task_stack_vm_area(tsk);
290 BUILD_BUG_ON(IS_ENABLED(CONFIG_VMAP_STACK) && PAGE_SIZE % 1024 != 0);
295 BUG_ON(vm->nr_pages != THREAD_SIZE / PAGE_SIZE);
297 for (i = 0; i < THREAD_SIZE / PAGE_SIZE; i++) {
298 mod_zone_page_state(page_zone(vm->pages[i]),
300 PAGE_SIZE / 1024 * account);
303 /* All stack pages belong to the same memcg. */
304 memcg_kmem_update_page_stat(vm->pages[0], MEMCG_KERNEL_STACK_KB,
305 account * (THREAD_SIZE / 1024));
308 * All stack pages are in the same zone and belong to the
311 struct page *first_page = virt_to_page(stack);
313 mod_zone_page_state(page_zone(first_page), NR_KERNEL_STACK_KB,
314 THREAD_SIZE / 1024 * account);
316 memcg_kmem_update_page_stat(first_page, MEMCG_KERNEL_STACK_KB,
317 account * (THREAD_SIZE / 1024));
321 static void release_task_stack(struct task_struct *tsk)
323 if (WARN_ON(tsk->state != TASK_DEAD))
324 return; /* Better to leak the stack than to free prematurely */
326 account_kernel_stack(tsk, -1);
327 arch_release_thread_stack(tsk->stack);
328 free_thread_stack(tsk);
330 #ifdef CONFIG_VMAP_STACK
331 tsk->stack_vm_area = NULL;
335 #ifdef CONFIG_THREAD_INFO_IN_TASK
336 void put_task_stack(struct task_struct *tsk)
338 if (atomic_dec_and_test(&tsk->stack_refcount))
339 release_task_stack(tsk);
343 void free_task(struct task_struct *tsk)
345 #ifndef CONFIG_THREAD_INFO_IN_TASK
347 * The task is finally done with both the stack and thread_info,
350 release_task_stack(tsk);
353 * If the task had a separate stack allocation, it should be gone
356 WARN_ON_ONCE(atomic_read(&tsk->stack_refcount) != 0);
358 rt_mutex_debug_task_free(tsk);
359 ftrace_graph_exit_task(tsk);
360 put_seccomp_filter(tsk);
361 arch_release_task_struct(tsk);
362 free_task_struct(tsk);
364 EXPORT_SYMBOL(free_task);
366 static inline void free_signal_struct(struct signal_struct *sig)
368 taskstats_tgid_free(sig);
369 sched_autogroup_exit(sig);
371 * __mmdrop is not safe to call from softirq context on x86 due to
372 * pgd_dtor so postpone it to the async context
375 mmdrop_async(sig->oom_mm);
376 kmem_cache_free(signal_cachep, sig);
379 static inline void put_signal_struct(struct signal_struct *sig)
381 if (atomic_dec_and_test(&sig->sigcnt))
382 free_signal_struct(sig);
385 void __put_task_struct(struct task_struct *tsk)
387 WARN_ON(!tsk->exit_state);
388 WARN_ON(atomic_read(&tsk->usage));
389 WARN_ON(tsk == current);
392 task_numa_free(tsk, true);
393 security_task_free(tsk);
395 delayacct_tsk_free(tsk);
396 put_signal_struct(tsk->signal);
398 if (!profile_handoff_task(tsk))
401 EXPORT_SYMBOL_GPL(__put_task_struct);
403 void __init __weak arch_task_cache_init(void) { }
408 static void set_max_threads(unsigned int max_threads_suggested)
413 * The number of threads shall be limited such that the thread
414 * structures may only consume a small part of the available memory.
416 if (fls64(totalram_pages) + fls64(PAGE_SIZE) > 64)
417 threads = MAX_THREADS;
419 threads = div64_u64((u64) totalram_pages * (u64) PAGE_SIZE,
420 (u64) THREAD_SIZE * 8UL);
422 if (threads > max_threads_suggested)
423 threads = max_threads_suggested;
425 max_threads = clamp_t(u64, threads, MIN_THREADS, MAX_THREADS);
428 #ifdef CONFIG_ARCH_WANTS_DYNAMIC_TASK_STRUCT
429 /* Initialized by the architecture: */
430 int arch_task_struct_size __read_mostly;
433 void __init fork_init(void)
436 #ifndef CONFIG_ARCH_TASK_STRUCT_ALLOCATOR
437 #ifndef ARCH_MIN_TASKALIGN
438 #define ARCH_MIN_TASKALIGN L1_CACHE_BYTES
440 /* create a slab on which task_structs can be allocated */
441 task_struct_cachep = kmem_cache_create("task_struct",
442 arch_task_struct_size, ARCH_MIN_TASKALIGN,
443 SLAB_PANIC|SLAB_NOTRACK|SLAB_ACCOUNT, NULL);
446 /* do the arch specific task caches init */
447 arch_task_cache_init();
449 set_max_threads(MAX_THREADS);
451 init_task.signal->rlim[RLIMIT_NPROC].rlim_cur = max_threads/2;
452 init_task.signal->rlim[RLIMIT_NPROC].rlim_max = max_threads/2;
453 init_task.signal->rlim[RLIMIT_SIGPENDING] =
454 init_task.signal->rlim[RLIMIT_NPROC];
456 for (i = 0; i < UCOUNT_COUNTS; i++) {
457 init_user_ns.ucount_max[i] = max_threads/2;
461 int __weak arch_dup_task_struct(struct task_struct *dst,
462 struct task_struct *src)
468 void set_task_stack_end_magic(struct task_struct *tsk)
470 unsigned long *stackend;
472 stackend = end_of_stack(tsk);
473 *stackend = STACK_END_MAGIC; /* for overflow detection */
476 static struct task_struct *dup_task_struct(struct task_struct *orig, int node)
478 struct task_struct *tsk;
479 unsigned long *stack;
480 struct vm_struct *stack_vm_area;
483 if (node == NUMA_NO_NODE)
484 node = tsk_fork_get_node(orig);
485 tsk = alloc_task_struct_node(node);
489 stack = alloc_thread_stack_node(tsk, node);
493 stack_vm_area = task_stack_vm_area(tsk);
495 err = arch_dup_task_struct(tsk, orig);
498 * arch_dup_task_struct() clobbers the stack-related fields. Make
499 * sure they're properly initialized before using any stack-related
504 err= kaiser_map_thread_stack(tsk->stack);
507 #ifdef CONFIG_VMAP_STACK
508 tsk->stack_vm_area = stack_vm_area;
510 #ifdef CONFIG_THREAD_INFO_IN_TASK
511 atomic_set(&tsk->stack_refcount, 1);
517 #ifdef CONFIG_SECCOMP
519 * We must handle setting up seccomp filters once we're under
520 * the sighand lock in case orig has changed between now and
521 * then. Until then, filter must be NULL to avoid messing up
522 * the usage counts on the error path calling free_task.
524 tsk->seccomp.filter = NULL;
527 setup_thread_stack(tsk, orig);
528 clear_user_return_notifier(tsk);
529 clear_tsk_need_resched(tsk);
530 set_task_stack_end_magic(tsk);
532 #ifdef CONFIG_CC_STACKPROTECTOR
533 tsk->stack_canary = get_random_long();
537 * One for us, one for whoever does the "release_task()" (usually
540 atomic_set(&tsk->usage, 2);
541 #ifdef CONFIG_BLK_DEV_IO_TRACE
544 tsk->splice_pipe = NULL;
545 tsk->task_frag.page = NULL;
546 tsk->wake_q.next = NULL;
548 account_kernel_stack(tsk, 1);
555 free_thread_stack(tsk);
557 free_task_struct(tsk);
562 static __latent_entropy int dup_mmap(struct mm_struct *mm,
563 struct mm_struct *oldmm)
565 struct vm_area_struct *mpnt, *tmp, *prev, **pprev;
566 struct rb_node **rb_link, *rb_parent;
568 unsigned long charge;
570 uprobe_start_dup_mmap();
571 if (down_write_killable(&oldmm->mmap_sem)) {
573 goto fail_uprobe_end;
575 flush_cache_dup_mm(oldmm);
576 uprobe_dup_mmap(oldmm, mm);
578 * Not linked in yet - no deadlock potential:
580 down_write_nested(&mm->mmap_sem, SINGLE_DEPTH_NESTING);
582 /* No ordering required: file already has been exposed. */
583 RCU_INIT_POINTER(mm->exe_file, get_mm_exe_file(oldmm));
585 mm->total_vm = oldmm->total_vm;
586 mm->data_vm = oldmm->data_vm;
587 mm->exec_vm = oldmm->exec_vm;
588 mm->stack_vm = oldmm->stack_vm;
590 rb_link = &mm->mm_rb.rb_node;
593 retval = ksm_fork(mm, oldmm);
596 retval = khugepaged_fork(mm, oldmm);
601 for (mpnt = oldmm->mmap; mpnt; mpnt = mpnt->vm_next) {
604 if (mpnt->vm_flags & VM_DONTCOPY) {
605 vm_stat_account(mm, mpnt->vm_flags, -vma_pages(mpnt));
609 if (mpnt->vm_flags & VM_ACCOUNT) {
610 unsigned long len = vma_pages(mpnt);
612 if (security_vm_enough_memory_mm(oldmm, len)) /* sic */
616 tmp = kmem_cache_alloc(vm_area_cachep, GFP_KERNEL);
620 INIT_LIST_HEAD(&tmp->anon_vma_chain);
621 retval = vma_dup_policy(mpnt, tmp);
623 goto fail_nomem_policy;
625 if (anon_vma_fork(tmp, mpnt))
626 goto fail_nomem_anon_vma_fork;
628 ~(VM_LOCKED|VM_LOCKONFAULT|VM_UFFD_MISSING|VM_UFFD_WP);
629 tmp->vm_next = tmp->vm_prev = NULL;
630 tmp->vm_userfaultfd_ctx = NULL_VM_UFFD_CTX;
633 struct inode *inode = file_inode(file);
634 struct address_space *mapping = file->f_mapping;
637 if (tmp->vm_flags & VM_DENYWRITE)
638 atomic_dec(&inode->i_writecount);
639 i_mmap_lock_write(mapping);
640 if (tmp->vm_flags & VM_SHARED)
641 atomic_inc(&mapping->i_mmap_writable);
642 flush_dcache_mmap_lock(mapping);
643 /* insert tmp into the share list, just after mpnt */
644 vma_interval_tree_insert_after(tmp, mpnt,
646 flush_dcache_mmap_unlock(mapping);
647 i_mmap_unlock_write(mapping);
651 * Clear hugetlb-related page reserves for children. This only
652 * affects MAP_PRIVATE mappings. Faults generated by the child
653 * are not guaranteed to succeed, even if read-only
655 if (is_vm_hugetlb_page(tmp))
656 reset_vma_resv_huge_pages(tmp);
659 * Link in the new vma and copy the page table entries.
662 pprev = &tmp->vm_next;
666 __vma_link_rb(mm, tmp, rb_link, rb_parent);
667 rb_link = &tmp->vm_rb.rb_right;
668 rb_parent = &tmp->vm_rb;
671 retval = copy_page_range(mm, oldmm, mpnt);
673 if (tmp->vm_ops && tmp->vm_ops->open)
674 tmp->vm_ops->open(tmp);
679 /* a new mm has just been created */
680 arch_dup_mmap(oldmm, mm);
683 up_write(&mm->mmap_sem);
685 up_write(&oldmm->mmap_sem);
687 uprobe_end_dup_mmap();
689 fail_nomem_anon_vma_fork:
690 mpol_put(vma_policy(tmp));
692 kmem_cache_free(vm_area_cachep, tmp);
695 vm_unacct_memory(charge);
699 static inline int mm_alloc_pgd(struct mm_struct *mm)
701 mm->pgd = pgd_alloc(mm);
702 if (unlikely(!mm->pgd))
707 static inline void mm_free_pgd(struct mm_struct *mm)
709 pgd_free(mm, mm->pgd);
712 static int dup_mmap(struct mm_struct *mm, struct mm_struct *oldmm)
714 down_write(&oldmm->mmap_sem);
715 RCU_INIT_POINTER(mm->exe_file, get_mm_exe_file(oldmm));
716 up_write(&oldmm->mmap_sem);
719 #define mm_alloc_pgd(mm) (0)
720 #define mm_free_pgd(mm)
721 #endif /* CONFIG_MMU */
723 __cacheline_aligned_in_smp DEFINE_SPINLOCK(mmlist_lock);
725 #define allocate_mm() (kmem_cache_alloc(mm_cachep, GFP_KERNEL))
726 #define free_mm(mm) (kmem_cache_free(mm_cachep, (mm)))
728 static unsigned long default_dump_filter = MMF_DUMP_FILTER_DEFAULT;
730 static int __init coredump_filter_setup(char *s)
732 default_dump_filter =
733 (simple_strtoul(s, NULL, 0) << MMF_DUMP_FILTER_SHIFT) &
734 MMF_DUMP_FILTER_MASK;
738 __setup("coredump_filter=", coredump_filter_setup);
740 #include <linux/init_task.h>
742 static void mm_init_aio(struct mm_struct *mm)
745 spin_lock_init(&mm->ioctx_lock);
746 mm->ioctx_table = NULL;
750 static void mm_init_owner(struct mm_struct *mm, struct task_struct *p)
757 static void mm_init_uprobes_state(struct mm_struct *mm)
759 #ifdef CONFIG_UPROBES
760 mm->uprobes_state.xol_area = NULL;
764 static struct mm_struct *mm_init(struct mm_struct *mm, struct task_struct *p,
765 struct user_namespace *user_ns)
769 mm->vmacache_seqnum = 0;
770 atomic_set(&mm->mm_users, 1);
771 atomic_set(&mm->mm_count, 1);
772 init_rwsem(&mm->mmap_sem);
773 INIT_LIST_HEAD(&mm->mmlist);
774 mm->core_state = NULL;
775 atomic_long_set(&mm->nr_ptes, 0);
780 memset(&mm->rss_stat, 0, sizeof(mm->rss_stat));
781 spin_lock_init(&mm->page_table_lock);
784 mm_init_owner(mm, p);
785 RCU_INIT_POINTER(mm->exe_file, NULL);
786 mmu_notifier_mm_init(mm);
787 clear_tlb_flush_pending(mm);
788 #if defined(CONFIG_TRANSPARENT_HUGEPAGE) && !USE_SPLIT_PMD_PTLOCKS
789 mm->pmd_huge_pte = NULL;
791 mm_init_uprobes_state(mm);
792 hugetlb_count_init(mm);
795 mm->flags = current->mm->flags & MMF_INIT_MASK;
796 mm->def_flags = current->mm->def_flags & VM_INIT_DEF_MASK;
798 mm->flags = default_dump_filter;
802 if (mm_alloc_pgd(mm))
805 if (init_new_context(p, mm))
808 mm->user_ns = get_user_ns(user_ns);
818 static void check_mm(struct mm_struct *mm)
822 for (i = 0; i < NR_MM_COUNTERS; i++) {
823 long x = atomic_long_read(&mm->rss_stat.count[i]);
826 printk(KERN_ALERT "BUG: Bad rss-counter state "
827 "mm:%p idx:%d val:%ld\n", mm, i, x);
830 if (atomic_long_read(&mm->nr_ptes))
831 pr_alert("BUG: non-zero nr_ptes on freeing mm: %ld\n",
832 atomic_long_read(&mm->nr_ptes));
834 pr_alert("BUG: non-zero nr_pmds on freeing mm: %ld\n",
837 #if defined(CONFIG_TRANSPARENT_HUGEPAGE) && !USE_SPLIT_PMD_PTLOCKS
838 VM_BUG_ON_MM(mm->pmd_huge_pte, mm);
843 * Allocate and initialize an mm_struct.
845 struct mm_struct *mm_alloc(void)
847 struct mm_struct *mm;
853 memset(mm, 0, sizeof(*mm));
854 return mm_init(mm, current, current_user_ns());
858 * Called when the last reference to the mm
859 * is dropped: either by a lazy thread or by
860 * mmput. Free the page directory and the mm.
862 void __mmdrop(struct mm_struct *mm)
864 BUG_ON(mm == &init_mm);
867 mmu_notifier_mm_destroy(mm);
869 put_user_ns(mm->user_ns);
872 EXPORT_SYMBOL_GPL(__mmdrop);
874 static inline void __mmput(struct mm_struct *mm)
876 VM_BUG_ON(atomic_read(&mm->mm_users));
878 uprobe_clear_state(mm);
881 khugepaged_exit(mm); /* must run before exit_mmap */
883 mm_put_huge_zero_page(mm);
884 set_mm_exe_file(mm, NULL);
885 if (!list_empty(&mm->mmlist)) {
886 spin_lock(&mmlist_lock);
887 list_del(&mm->mmlist);
888 spin_unlock(&mmlist_lock);
891 module_put(mm->binfmt->module);
892 set_bit(MMF_OOM_SKIP, &mm->flags);
897 * Decrement the use count and release all resources for an mm.
899 void mmput(struct mm_struct *mm)
903 if (atomic_dec_and_test(&mm->mm_users))
906 EXPORT_SYMBOL_GPL(mmput);
909 static void mmput_async_fn(struct work_struct *work)
911 struct mm_struct *mm = container_of(work, struct mm_struct, async_put_work);
915 void mmput_async(struct mm_struct *mm)
917 if (atomic_dec_and_test(&mm->mm_users)) {
918 INIT_WORK(&mm->async_put_work, mmput_async_fn);
919 schedule_work(&mm->async_put_work);
925 * set_mm_exe_file - change a reference to the mm's executable file
927 * This changes mm's executable file (shown as symlink /proc/[pid]/exe).
929 * Main users are mmput() and sys_execve(). Callers prevent concurrent
930 * invocations: in mmput() nobody alive left, in execve task is single
931 * threaded. sys_prctl(PR_SET_MM_MAP/EXE_FILE) also needs to set the
932 * mm->exe_file, but does so without using set_mm_exe_file() in order
933 * to do avoid the need for any locks.
935 void set_mm_exe_file(struct mm_struct *mm, struct file *new_exe_file)
937 struct file *old_exe_file;
940 * It is safe to dereference the exe_file without RCU as
941 * this function is only called if nobody else can access
942 * this mm -- see comment above for justification.
944 old_exe_file = rcu_dereference_raw(mm->exe_file);
947 get_file(new_exe_file);
948 rcu_assign_pointer(mm->exe_file, new_exe_file);
954 * get_mm_exe_file - acquire a reference to the mm's executable file
956 * Returns %NULL if mm has no associated executable file.
957 * User must release file via fput().
959 struct file *get_mm_exe_file(struct mm_struct *mm)
961 struct file *exe_file;
964 exe_file = rcu_dereference(mm->exe_file);
965 if (exe_file && !get_file_rcu(exe_file))
970 EXPORT_SYMBOL(get_mm_exe_file);
973 * get_task_exe_file - acquire a reference to the task's executable file
975 * Returns %NULL if task's mm (if any) has no associated executable file or
976 * this is a kernel thread with borrowed mm (see the comment above get_task_mm).
977 * User must release file via fput().
979 struct file *get_task_exe_file(struct task_struct *task)
981 struct file *exe_file = NULL;
982 struct mm_struct *mm;
987 if (!(task->flags & PF_KTHREAD))
988 exe_file = get_mm_exe_file(mm);
993 EXPORT_SYMBOL(get_task_exe_file);
996 * get_task_mm - acquire a reference to the task's mm
998 * Returns %NULL if the task has no mm. Checks PF_KTHREAD (meaning
999 * this kernel workthread has transiently adopted a user mm with use_mm,
1000 * to do its AIO) is not set and if so returns a reference to it, after
1001 * bumping up the use count. User must release the mm via mmput()
1002 * after use. Typically used by /proc and ptrace.
1004 struct mm_struct *get_task_mm(struct task_struct *task)
1006 struct mm_struct *mm;
1011 if (task->flags & PF_KTHREAD)
1014 atomic_inc(&mm->mm_users);
1019 EXPORT_SYMBOL_GPL(get_task_mm);
1021 struct mm_struct *mm_access(struct task_struct *task, unsigned int mode)
1023 struct mm_struct *mm;
1026 err = mutex_lock_killable(&task->signal->cred_guard_mutex);
1028 return ERR_PTR(err);
1030 mm = get_task_mm(task);
1031 if (mm && mm != current->mm &&
1032 !ptrace_may_access(task, mode)) {
1034 mm = ERR_PTR(-EACCES);
1036 mutex_unlock(&task->signal->cred_guard_mutex);
1041 static void complete_vfork_done(struct task_struct *tsk)
1043 struct completion *vfork;
1046 vfork = tsk->vfork_done;
1047 if (likely(vfork)) {
1048 tsk->vfork_done = NULL;
1054 static int wait_for_vfork_done(struct task_struct *child,
1055 struct completion *vfork)
1059 freezer_do_not_count();
1060 killed = wait_for_completion_killable(vfork);
1065 child->vfork_done = NULL;
1069 put_task_struct(child);
1073 /* Please note the differences between mmput and mm_release.
1074 * mmput is called whenever we stop holding onto a mm_struct,
1075 * error success whatever.
1077 * mm_release is called after a mm_struct has been removed
1078 * from the current process.
1080 * This difference is important for error handling, when we
1081 * only half set up a mm_struct for a new process and need to restore
1082 * the old one. Because we mmput the new mm_struct before
1083 * restoring the old one. . .
1084 * Eric Biederman 10 January 1998
1086 static void mm_release(struct task_struct *tsk, struct mm_struct *mm)
1088 uprobe_free_utask(tsk);
1090 /* Get rid of any cached register state */
1091 deactivate_mm(tsk, mm);
1094 * Signal userspace if we're not exiting with a core dump
1095 * because we want to leave the value intact for debugging
1098 if (tsk->clear_child_tid) {
1099 if (!(tsk->signal->flags & SIGNAL_GROUP_COREDUMP) &&
1100 atomic_read(&mm->mm_users) > 1) {
1102 * We don't check the error code - if userspace has
1103 * not set up a proper pointer then tough luck.
1105 put_user(0, tsk->clear_child_tid);
1106 sys_futex(tsk->clear_child_tid, FUTEX_WAKE,
1109 tsk->clear_child_tid = NULL;
1113 * All done, finally we can wake up parent and return this mm to him.
1114 * Also kthread_stop() uses this completion for synchronization.
1116 if (tsk->vfork_done)
1117 complete_vfork_done(tsk);
1120 void exit_mm_release(struct task_struct *tsk, struct mm_struct *mm)
1122 futex_exit_release(tsk);
1123 mm_release(tsk, mm);
1126 void exec_mm_release(struct task_struct *tsk, struct mm_struct *mm)
1128 futex_exec_release(tsk);
1129 mm_release(tsk, mm);
1133 * Allocate a new mm structure and copy contents from the
1134 * mm structure of the passed in task structure.
1136 static struct mm_struct *dup_mm(struct task_struct *tsk)
1138 struct mm_struct *mm, *oldmm = current->mm;
1145 memcpy(mm, oldmm, sizeof(*mm));
1147 if (!mm_init(mm, tsk, mm->user_ns))
1150 err = dup_mmap(mm, oldmm);
1154 mm->hiwater_rss = get_mm_rss(mm);
1155 mm->hiwater_vm = mm->total_vm;
1157 if (mm->binfmt && !try_module_get(mm->binfmt->module))
1163 /* don't put binfmt in mmput, we haven't got module yet */
1171 static int copy_mm(unsigned long clone_flags, struct task_struct *tsk)
1173 struct mm_struct *mm, *oldmm;
1176 tsk->min_flt = tsk->maj_flt = 0;
1177 tsk->nvcsw = tsk->nivcsw = 0;
1178 #ifdef CONFIG_DETECT_HUNG_TASK
1179 tsk->last_switch_count = tsk->nvcsw + tsk->nivcsw;
1183 tsk->active_mm = NULL;
1186 * Are we cloning a kernel thread?
1188 * We need to steal a active VM for that..
1190 oldmm = current->mm;
1194 /* initialize the new vmacache entries */
1195 vmacache_flush(tsk);
1197 if (clone_flags & CLONE_VM) {
1198 atomic_inc(&oldmm->mm_users);
1210 tsk->active_mm = mm;
1217 static int copy_fs(unsigned long clone_flags, struct task_struct *tsk)
1219 struct fs_struct *fs = current->fs;
1220 if (clone_flags & CLONE_FS) {
1221 /* tsk->fs is already what we want */
1222 spin_lock(&fs->lock);
1224 spin_unlock(&fs->lock);
1228 spin_unlock(&fs->lock);
1231 tsk->fs = copy_fs_struct(fs);
1237 static int copy_files(unsigned long clone_flags, struct task_struct *tsk)
1239 struct files_struct *oldf, *newf;
1243 * A background process may not have any files ...
1245 oldf = current->files;
1249 if (clone_flags & CLONE_FILES) {
1250 atomic_inc(&oldf->count);
1254 newf = dup_fd(oldf, &error);
1264 static int copy_io(unsigned long clone_flags, struct task_struct *tsk)
1267 struct io_context *ioc = current->io_context;
1268 struct io_context *new_ioc;
1273 * Share io context with parent, if CLONE_IO is set
1275 if (clone_flags & CLONE_IO) {
1277 tsk->io_context = ioc;
1278 } else if (ioprio_valid(ioc->ioprio)) {
1279 new_ioc = get_task_io_context(tsk, GFP_KERNEL, NUMA_NO_NODE);
1280 if (unlikely(!new_ioc))
1283 new_ioc->ioprio = ioc->ioprio;
1284 put_io_context(new_ioc);
1290 static int copy_sighand(unsigned long clone_flags, struct task_struct *tsk)
1292 struct sighand_struct *sig;
1294 if (clone_flags & CLONE_SIGHAND) {
1295 atomic_inc(¤t->sighand->count);
1298 sig = kmem_cache_alloc(sighand_cachep, GFP_KERNEL);
1299 rcu_assign_pointer(tsk->sighand, sig);
1303 atomic_set(&sig->count, 1);
1304 spin_lock_irq(¤t->sighand->siglock);
1305 memcpy(sig->action, current->sighand->action, sizeof(sig->action));
1306 spin_unlock_irq(¤t->sighand->siglock);
1310 void __cleanup_sighand(struct sighand_struct *sighand)
1312 if (atomic_dec_and_test(&sighand->count)) {
1313 signalfd_cleanup(sighand);
1315 * sighand_cachep is SLAB_DESTROY_BY_RCU so we can free it
1316 * without an RCU grace period, see __lock_task_sighand().
1318 kmem_cache_free(sighand_cachep, sighand);
1323 * Initialize POSIX timer handling for a thread group.
1325 static void posix_cpu_timers_init_group(struct signal_struct *sig)
1327 unsigned long cpu_limit;
1329 cpu_limit = READ_ONCE(sig->rlim[RLIMIT_CPU].rlim_cur);
1330 if (cpu_limit != RLIM_INFINITY) {
1331 sig->cputime_expires.prof_exp = secs_to_cputime(cpu_limit);
1332 sig->cputimer.running = true;
1335 /* The timer lists. */
1336 INIT_LIST_HEAD(&sig->cpu_timers[0]);
1337 INIT_LIST_HEAD(&sig->cpu_timers[1]);
1338 INIT_LIST_HEAD(&sig->cpu_timers[2]);
1341 static int copy_signal(unsigned long clone_flags, struct task_struct *tsk)
1343 struct signal_struct *sig;
1345 if (clone_flags & CLONE_THREAD)
1348 sig = kmem_cache_zalloc(signal_cachep, GFP_KERNEL);
1353 sig->nr_threads = 1;
1354 atomic_set(&sig->live, 1);
1355 atomic_set(&sig->sigcnt, 1);
1357 /* list_add(thread_node, thread_head) without INIT_LIST_HEAD() */
1358 sig->thread_head = (struct list_head)LIST_HEAD_INIT(tsk->thread_node);
1359 tsk->thread_node = (struct list_head)LIST_HEAD_INIT(sig->thread_head);
1361 init_waitqueue_head(&sig->wait_chldexit);
1362 sig->curr_target = tsk;
1363 init_sigpending(&sig->shared_pending);
1364 INIT_LIST_HEAD(&sig->posix_timers);
1365 seqlock_init(&sig->stats_lock);
1366 prev_cputime_init(&sig->prev_cputime);
1368 hrtimer_init(&sig->real_timer, CLOCK_MONOTONIC, HRTIMER_MODE_REL);
1369 sig->real_timer.function = it_real_fn;
1371 task_lock(current->group_leader);
1372 memcpy(sig->rlim, current->signal->rlim, sizeof sig->rlim);
1373 task_unlock(current->group_leader);
1375 posix_cpu_timers_init_group(sig);
1377 tty_audit_fork(sig);
1378 sched_autogroup_fork(sig);
1380 sig->oom_score_adj = current->signal->oom_score_adj;
1381 sig->oom_score_adj_min = current->signal->oom_score_adj_min;
1383 sig->has_child_subreaper = current->signal->has_child_subreaper ||
1384 current->signal->is_child_subreaper;
1386 mutex_init(&sig->cred_guard_mutex);
1391 static void copy_seccomp(struct task_struct *p)
1393 #ifdef CONFIG_SECCOMP
1395 * Must be called with sighand->lock held, which is common to
1396 * all threads in the group. Holding cred_guard_mutex is not
1397 * needed because this new task is not yet running and cannot
1400 assert_spin_locked(¤t->sighand->siglock);
1402 /* Ref-count the new filter user, and assign it. */
1403 get_seccomp_filter(current);
1404 p->seccomp = current->seccomp;
1407 * Explicitly enable no_new_privs here in case it got set
1408 * between the task_struct being duplicated and holding the
1409 * sighand lock. The seccomp state and nnp must be in sync.
1411 if (task_no_new_privs(current))
1412 task_set_no_new_privs(p);
1415 * If the parent gained a seccomp mode after copying thread
1416 * flags and between before we held the sighand lock, we have
1417 * to manually enable the seccomp thread flag here.
1419 if (p->seccomp.mode != SECCOMP_MODE_DISABLED)
1420 set_tsk_thread_flag(p, TIF_SECCOMP);
1424 SYSCALL_DEFINE1(set_tid_address, int __user *, tidptr)
1426 current->clear_child_tid = tidptr;
1428 return task_pid_vnr(current);
1431 static void rt_mutex_init_task(struct task_struct *p)
1433 raw_spin_lock_init(&p->pi_lock);
1434 #ifdef CONFIG_RT_MUTEXES
1435 p->pi_waiters = RB_ROOT;
1436 p->pi_waiters_leftmost = NULL;
1437 p->pi_blocked_on = NULL;
1442 * Initialize POSIX timer handling for a single task.
1444 static void posix_cpu_timers_init(struct task_struct *tsk)
1446 tsk->cputime_expires.prof_exp = 0;
1447 tsk->cputime_expires.virt_exp = 0;
1448 tsk->cputime_expires.sched_exp = 0;
1449 INIT_LIST_HEAD(&tsk->cpu_timers[0]);
1450 INIT_LIST_HEAD(&tsk->cpu_timers[1]);
1451 INIT_LIST_HEAD(&tsk->cpu_timers[2]);
1455 init_task_pid(struct task_struct *task, enum pid_type type, struct pid *pid)
1457 task->pids[type].pid = pid;
1461 * This creates a new process as a copy of the old one,
1462 * but does not actually start it yet.
1464 * It copies the registers, and all the appropriate
1465 * parts of the process environment (as per the clone
1466 * flags). The actual kick-off is left to the caller.
1468 static __latent_entropy struct task_struct *copy_process(
1469 unsigned long clone_flags,
1470 unsigned long stack_start,
1471 unsigned long stack_size,
1472 int __user *child_tidptr,
1479 struct task_struct *p;
1481 if ((clone_flags & (CLONE_NEWNS|CLONE_FS)) == (CLONE_NEWNS|CLONE_FS))
1482 return ERR_PTR(-EINVAL);
1484 if ((clone_flags & (CLONE_NEWUSER|CLONE_FS)) == (CLONE_NEWUSER|CLONE_FS))
1485 return ERR_PTR(-EINVAL);
1488 * Thread groups must share signals as well, and detached threads
1489 * can only be started up within the thread group.
1491 if ((clone_flags & CLONE_THREAD) && !(clone_flags & CLONE_SIGHAND))
1492 return ERR_PTR(-EINVAL);
1495 * Shared signal handlers imply shared VM. By way of the above,
1496 * thread groups also imply shared VM. Blocking this case allows
1497 * for various simplifications in other code.
1499 if ((clone_flags & CLONE_SIGHAND) && !(clone_flags & CLONE_VM))
1500 return ERR_PTR(-EINVAL);
1503 * Siblings of global init remain as zombies on exit since they are
1504 * not reaped by their parent (swapper). To solve this and to avoid
1505 * multi-rooted process trees, prevent global and container-inits
1506 * from creating siblings.
1508 if ((clone_flags & CLONE_PARENT) &&
1509 current->signal->flags & SIGNAL_UNKILLABLE)
1510 return ERR_PTR(-EINVAL);
1513 * If the new process will be in a different pid or user namespace
1514 * do not allow it to share a thread group with the forking task.
1516 if (clone_flags & CLONE_THREAD) {
1517 if ((clone_flags & (CLONE_NEWUSER | CLONE_NEWPID)) ||
1518 (task_active_pid_ns(current) !=
1519 current->nsproxy->pid_ns_for_children))
1520 return ERR_PTR(-EINVAL);
1523 retval = security_task_create(clone_flags);
1528 p = dup_task_struct(current, node);
1533 * This _must_ happen before we call free_task(), i.e. before we jump
1534 * to any of the bad_fork_* labels. This is to avoid freeing
1535 * p->set_child_tid which is (ab)used as a kthread's data pointer for
1536 * kernel threads (PF_KTHREAD).
1538 p->set_child_tid = (clone_flags & CLONE_CHILD_SETTID) ? child_tidptr : NULL;
1540 * Clear TID on mm_release()?
1542 p->clear_child_tid = (clone_flags & CLONE_CHILD_CLEARTID) ? child_tidptr : NULL;
1544 ftrace_graph_init_task(p);
1546 rt_mutex_init_task(p);
1548 #ifdef CONFIG_PROVE_LOCKING
1549 DEBUG_LOCKS_WARN_ON(!p->hardirqs_enabled);
1550 DEBUG_LOCKS_WARN_ON(!p->softirqs_enabled);
1553 if (atomic_read(&p->real_cred->user->processes) >=
1554 task_rlimit(p, RLIMIT_NPROC)) {
1555 if (p->real_cred->user != INIT_USER &&
1556 !capable(CAP_SYS_RESOURCE) && !capable(CAP_SYS_ADMIN))
1559 current->flags &= ~PF_NPROC_EXCEEDED;
1561 retval = copy_creds(p, clone_flags);
1566 * If multiple threads are within copy_process(), then this check
1567 * triggers too late. This doesn't hurt, the check is only there
1568 * to stop root fork bombs.
1571 if (nr_threads >= max_threads)
1572 goto bad_fork_cleanup_count;
1574 delayacct_tsk_init(p); /* Must remain after dup_task_struct() */
1575 p->flags &= ~(PF_SUPERPRIV | PF_WQ_WORKER);
1576 p->flags |= PF_FORKNOEXEC;
1577 INIT_LIST_HEAD(&p->children);
1578 INIT_LIST_HEAD(&p->sibling);
1579 rcu_copy_process(p);
1580 p->vfork_done = NULL;
1581 spin_lock_init(&p->alloc_lock);
1583 init_sigpending(&p->pending);
1585 p->utime = p->stime = p->gtime = 0;
1586 p->utimescaled = p->stimescaled = 0;
1587 prev_cputime_init(&p->prev_cputime);
1589 #ifdef CONFIG_VIRT_CPU_ACCOUNTING_GEN
1590 seqcount_init(&p->vtime_seqcount);
1592 p->vtime_snap_whence = VTIME_INACTIVE;
1595 #if defined(SPLIT_RSS_COUNTING)
1596 memset(&p->rss_stat, 0, sizeof(p->rss_stat));
1599 p->default_timer_slack_ns = current->timer_slack_ns;
1601 task_io_accounting_init(&p->ioac);
1602 acct_clear_integrals(p);
1604 posix_cpu_timers_init(p);
1606 p->io_context = NULL;
1607 p->audit_context = NULL;
1610 p->mempolicy = mpol_dup(p->mempolicy);
1611 if (IS_ERR(p->mempolicy)) {
1612 retval = PTR_ERR(p->mempolicy);
1613 p->mempolicy = NULL;
1614 goto bad_fork_cleanup_threadgroup_lock;
1617 #ifdef CONFIG_CPUSETS
1618 p->cpuset_mem_spread_rotor = NUMA_NO_NODE;
1619 p->cpuset_slab_spread_rotor = NUMA_NO_NODE;
1620 seqcount_init(&p->mems_allowed_seq);
1622 #ifdef CONFIG_TRACE_IRQFLAGS
1624 p->hardirqs_enabled = 0;
1625 p->hardirq_enable_ip = 0;
1626 p->hardirq_enable_event = 0;
1627 p->hardirq_disable_ip = _THIS_IP_;
1628 p->hardirq_disable_event = 0;
1629 p->softirqs_enabled = 1;
1630 p->softirq_enable_ip = _THIS_IP_;
1631 p->softirq_enable_event = 0;
1632 p->softirq_disable_ip = 0;
1633 p->softirq_disable_event = 0;
1634 p->hardirq_context = 0;
1635 p->softirq_context = 0;
1638 p->pagefault_disabled = 0;
1640 #ifdef CONFIG_LOCKDEP
1641 p->lockdep_depth = 0; /* no locks held yet */
1642 p->curr_chain_key = 0;
1643 p->lockdep_recursion = 0;
1646 #ifdef CONFIG_DEBUG_MUTEXES
1647 p->blocked_on = NULL; /* not blocked yet */
1649 #ifdef CONFIG_BCACHE
1650 p->sequential_io = 0;
1651 p->sequential_io_avg = 0;
1654 /* Perform scheduler related setup. Assign this task to a CPU. */
1655 retval = sched_fork(clone_flags, p);
1657 goto bad_fork_cleanup_policy;
1659 retval = perf_event_init_task(p);
1661 goto bad_fork_cleanup_policy;
1662 retval = audit_alloc(p);
1664 goto bad_fork_cleanup_perf;
1665 /* copy all the process information */
1667 retval = copy_semundo(clone_flags, p);
1669 goto bad_fork_cleanup_audit;
1670 retval = copy_files(clone_flags, p);
1672 goto bad_fork_cleanup_semundo;
1673 retval = copy_fs(clone_flags, p);
1675 goto bad_fork_cleanup_files;
1676 retval = copy_sighand(clone_flags, p);
1678 goto bad_fork_cleanup_fs;
1679 retval = copy_signal(clone_flags, p);
1681 goto bad_fork_cleanup_sighand;
1682 retval = copy_mm(clone_flags, p);
1684 goto bad_fork_cleanup_signal;
1685 retval = copy_namespaces(clone_flags, p);
1687 goto bad_fork_cleanup_mm;
1688 retval = copy_io(clone_flags, p);
1690 goto bad_fork_cleanup_namespaces;
1691 retval = copy_thread_tls(clone_flags, stack_start, stack_size, p, tls);
1693 goto bad_fork_cleanup_io;
1695 if (pid != &init_struct_pid) {
1696 pid = alloc_pid(p->nsproxy->pid_ns_for_children);
1698 retval = PTR_ERR(pid);
1699 goto bad_fork_cleanup_thread;
1709 * sigaltstack should be cleared when sharing the same VM
1711 if ((clone_flags & (CLONE_VM|CLONE_VFORK)) == CLONE_VM)
1715 * Syscall tracing and stepping should be turned off in the
1716 * child regardless of CLONE_PTRACE.
1718 user_disable_single_step(p);
1719 clear_tsk_thread_flag(p, TIF_SYSCALL_TRACE);
1720 #ifdef TIF_SYSCALL_EMU
1721 clear_tsk_thread_flag(p, TIF_SYSCALL_EMU);
1723 clear_all_latency_tracing(p);
1725 /* ok, now we should be set up.. */
1726 p->pid = pid_nr(pid);
1727 if (clone_flags & CLONE_THREAD) {
1728 p->group_leader = current->group_leader;
1729 p->tgid = current->tgid;
1731 p->group_leader = p;
1736 p->nr_dirtied_pause = 128 >> (PAGE_SHIFT - 10);
1737 p->dirty_paused_when = 0;
1739 p->pdeath_signal = 0;
1740 INIT_LIST_HEAD(&p->thread_group);
1741 p->task_works = NULL;
1743 threadgroup_change_begin(current);
1745 * Ensure that the cgroup subsystem policies allow the new process to be
1746 * forked. It should be noted the the new process's css_set can be changed
1747 * between here and cgroup_post_fork() if an organisation operation is in
1750 retval = cgroup_can_fork(p);
1752 goto bad_fork_free_pid;
1755 * From this point on we must avoid any synchronous user-space
1756 * communication until we take the tasklist-lock. In particular, we do
1757 * not want user-space to be able to predict the process start-time by
1758 * stalling fork(2) after we recorded the start_time but before it is
1759 * visible to the system.
1762 p->start_time = ktime_get_ns();
1763 p->real_start_time = ktime_get_boot_ns();
1766 * Make it visible to the rest of the system, but dont wake it up yet.
1767 * Need tasklist lock for parent etc handling!
1769 write_lock_irq(&tasklist_lock);
1771 /* CLONE_PARENT re-uses the old parent */
1772 if (clone_flags & (CLONE_PARENT|CLONE_THREAD)) {
1773 p->real_parent = current->real_parent;
1774 p->parent_exec_id = current->parent_exec_id;
1775 if (clone_flags & CLONE_THREAD)
1776 p->exit_signal = -1;
1778 p->exit_signal = current->group_leader->exit_signal;
1780 p->real_parent = current;
1781 p->parent_exec_id = current->self_exec_id;
1782 p->exit_signal = (clone_flags & CSIGNAL);
1785 spin_lock(¤t->sighand->siglock);
1788 * Copy seccomp details explicitly here, in case they were changed
1789 * before holding sighand lock.
1794 * Process group and session signals need to be delivered to just the
1795 * parent before the fork or both the parent and the child after the
1796 * fork. Restart if a signal comes in before we add the new process to
1797 * it's process group.
1798 * A fatal signal pending means that current will exit, so the new
1799 * thread can't slip out of an OOM kill (or normal SIGKILL).
1801 recalc_sigpending();
1802 if (signal_pending(current)) {
1803 retval = -ERESTARTNOINTR;
1804 goto bad_fork_cancel_cgroup;
1806 if (unlikely(!(ns_of_pid(pid)->nr_hashed & PIDNS_HASH_ADDING))) {
1808 goto bad_fork_cancel_cgroup;
1811 if (likely(p->pid)) {
1812 ptrace_init_task(p, (clone_flags & CLONE_PTRACE) || trace);
1814 init_task_pid(p, PIDTYPE_PID, pid);
1815 if (thread_group_leader(p)) {
1816 init_task_pid(p, PIDTYPE_PGID, task_pgrp(current));
1817 init_task_pid(p, PIDTYPE_SID, task_session(current));
1819 if (is_child_reaper(pid)) {
1820 ns_of_pid(pid)->child_reaper = p;
1821 p->signal->flags |= SIGNAL_UNKILLABLE;
1824 p->signal->leader_pid = pid;
1825 p->signal->tty = tty_kref_get(current->signal->tty);
1826 list_add_tail(&p->sibling, &p->real_parent->children);
1827 list_add_tail_rcu(&p->tasks, &init_task.tasks);
1828 attach_pid(p, PIDTYPE_PGID);
1829 attach_pid(p, PIDTYPE_SID);
1830 __this_cpu_inc(process_counts);
1832 current->signal->nr_threads++;
1833 atomic_inc(¤t->signal->live);
1834 atomic_inc(¤t->signal->sigcnt);
1835 list_add_tail_rcu(&p->thread_group,
1836 &p->group_leader->thread_group);
1837 list_add_tail_rcu(&p->thread_node,
1838 &p->signal->thread_head);
1840 attach_pid(p, PIDTYPE_PID);
1845 spin_unlock(¤t->sighand->siglock);
1846 syscall_tracepoint_update(p);
1847 write_unlock_irq(&tasklist_lock);
1849 proc_fork_connector(p);
1850 cgroup_post_fork(p);
1851 threadgroup_change_end(current);
1854 trace_task_newtask(p, clone_flags);
1855 uprobe_copy_process(p, clone_flags);
1859 bad_fork_cancel_cgroup:
1860 spin_unlock(¤t->sighand->siglock);
1861 write_unlock_irq(&tasklist_lock);
1862 cgroup_cancel_fork(p);
1864 threadgroup_change_end(current);
1865 if (pid != &init_struct_pid)
1867 bad_fork_cleanup_thread:
1869 bad_fork_cleanup_io:
1872 bad_fork_cleanup_namespaces:
1873 exit_task_namespaces(p);
1874 bad_fork_cleanup_mm:
1877 bad_fork_cleanup_signal:
1878 if (!(clone_flags & CLONE_THREAD))
1879 free_signal_struct(p->signal);
1880 bad_fork_cleanup_sighand:
1881 __cleanup_sighand(p->sighand);
1882 bad_fork_cleanup_fs:
1883 exit_fs(p); /* blocking */
1884 bad_fork_cleanup_files:
1885 exit_files(p); /* blocking */
1886 bad_fork_cleanup_semundo:
1888 bad_fork_cleanup_audit:
1890 bad_fork_cleanup_perf:
1891 perf_event_free_task(p);
1892 bad_fork_cleanup_policy:
1894 mpol_put(p->mempolicy);
1895 bad_fork_cleanup_threadgroup_lock:
1897 delayacct_tsk_free(p);
1898 bad_fork_cleanup_count:
1899 atomic_dec(&p->cred->user->processes);
1902 p->state = TASK_DEAD;
1906 return ERR_PTR(retval);
1909 static inline void init_idle_pids(struct pid_link *links)
1913 for (type = PIDTYPE_PID; type < PIDTYPE_MAX; ++type) {
1914 INIT_HLIST_NODE(&links[type].node); /* not really needed */
1915 links[type].pid = &init_struct_pid;
1919 struct task_struct *fork_idle(int cpu)
1921 struct task_struct *task;
1922 task = copy_process(CLONE_VM, 0, 0, NULL, &init_struct_pid, 0, 0,
1924 if (!IS_ERR(task)) {
1925 init_idle_pids(task->pids);
1926 init_idle(task, cpu);
1933 * Ok, this is the main fork-routine.
1935 * It copies the process, and if successful kick-starts
1936 * it and waits for it to finish using the VM if required.
1938 long _do_fork(unsigned long clone_flags,
1939 unsigned long stack_start,
1940 unsigned long stack_size,
1941 int __user *parent_tidptr,
1942 int __user *child_tidptr,
1945 struct task_struct *p;
1950 * Determine whether and which event to report to ptracer. When
1951 * called from kernel_thread or CLONE_UNTRACED is explicitly
1952 * requested, no event is reported; otherwise, report if the event
1953 * for the type of forking is enabled.
1955 if (!(clone_flags & CLONE_UNTRACED)) {
1956 if (clone_flags & CLONE_VFORK)
1957 trace = PTRACE_EVENT_VFORK;
1958 else if ((clone_flags & CSIGNAL) != SIGCHLD)
1959 trace = PTRACE_EVENT_CLONE;
1961 trace = PTRACE_EVENT_FORK;
1963 if (likely(!ptrace_event_enabled(current, trace)))
1967 p = copy_process(clone_flags, stack_start, stack_size,
1968 child_tidptr, NULL, trace, tls, NUMA_NO_NODE);
1969 add_latent_entropy();
1971 * Do this prior waking up the new thread - the thread pointer
1972 * might get invalid after that point, if the thread exits quickly.
1975 struct completion vfork;
1978 trace_sched_process_fork(current, p);
1980 pid = get_task_pid(p, PIDTYPE_PID);
1983 if (clone_flags & CLONE_PARENT_SETTID)
1984 put_user(nr, parent_tidptr);
1986 if (clone_flags & CLONE_VFORK) {
1987 p->vfork_done = &vfork;
1988 init_completion(&vfork);
1992 wake_up_new_task(p);
1994 /* forking complete and child started to run, tell ptracer */
1995 if (unlikely(trace))
1996 ptrace_event_pid(trace, pid);
1998 if (clone_flags & CLONE_VFORK) {
1999 if (!wait_for_vfork_done(p, &vfork))
2000 ptrace_event_pid(PTRACE_EVENT_VFORK_DONE, pid);
2010 #ifndef CONFIG_HAVE_COPY_THREAD_TLS
2011 /* For compatibility with architectures that call do_fork directly rather than
2012 * using the syscall entry points below. */
2013 long do_fork(unsigned long clone_flags,
2014 unsigned long stack_start,
2015 unsigned long stack_size,
2016 int __user *parent_tidptr,
2017 int __user *child_tidptr)
2019 return _do_fork(clone_flags, stack_start, stack_size,
2020 parent_tidptr, child_tidptr, 0);
2025 * Create a kernel thread.
2027 pid_t kernel_thread(int (*fn)(void *), void *arg, unsigned long flags)
2029 return _do_fork(flags|CLONE_VM|CLONE_UNTRACED, (unsigned long)fn,
2030 (unsigned long)arg, NULL, NULL, 0);
2033 #ifdef __ARCH_WANT_SYS_FORK
2034 SYSCALL_DEFINE0(fork)
2037 return _do_fork(SIGCHLD, 0, 0, NULL, NULL, 0);
2039 /* can not support in nommu mode */
2045 #ifdef __ARCH_WANT_SYS_VFORK
2046 SYSCALL_DEFINE0(vfork)
2048 return _do_fork(CLONE_VFORK | CLONE_VM | SIGCHLD, 0,
2053 #ifdef __ARCH_WANT_SYS_CLONE
2054 #ifdef CONFIG_CLONE_BACKWARDS
2055 SYSCALL_DEFINE5(clone, unsigned long, clone_flags, unsigned long, newsp,
2056 int __user *, parent_tidptr,
2058 int __user *, child_tidptr)
2059 #elif defined(CONFIG_CLONE_BACKWARDS2)
2060 SYSCALL_DEFINE5(clone, unsigned long, newsp, unsigned long, clone_flags,
2061 int __user *, parent_tidptr,
2062 int __user *, child_tidptr,
2064 #elif defined(CONFIG_CLONE_BACKWARDS3)
2065 SYSCALL_DEFINE6(clone, unsigned long, clone_flags, unsigned long, newsp,
2067 int __user *, parent_tidptr,
2068 int __user *, child_tidptr,
2071 SYSCALL_DEFINE5(clone, unsigned long, clone_flags, unsigned long, newsp,
2072 int __user *, parent_tidptr,
2073 int __user *, child_tidptr,
2077 return _do_fork(clone_flags, newsp, 0, parent_tidptr, child_tidptr, tls);
2081 #ifndef ARCH_MIN_MMSTRUCT_ALIGN
2082 #define ARCH_MIN_MMSTRUCT_ALIGN 0
2085 static void sighand_ctor(void *data)
2087 struct sighand_struct *sighand = data;
2089 spin_lock_init(&sighand->siglock);
2090 init_waitqueue_head(&sighand->signalfd_wqh);
2093 void __init proc_caches_init(void)
2095 sighand_cachep = kmem_cache_create("sighand_cache",
2096 sizeof(struct sighand_struct), 0,
2097 SLAB_HWCACHE_ALIGN|SLAB_PANIC|SLAB_DESTROY_BY_RCU|
2098 SLAB_NOTRACK|SLAB_ACCOUNT, sighand_ctor);
2099 signal_cachep = kmem_cache_create("signal_cache",
2100 sizeof(struct signal_struct), 0,
2101 SLAB_HWCACHE_ALIGN|SLAB_PANIC|SLAB_NOTRACK|SLAB_ACCOUNT,
2103 files_cachep = kmem_cache_create("files_cache",
2104 sizeof(struct files_struct), 0,
2105 SLAB_HWCACHE_ALIGN|SLAB_PANIC|SLAB_NOTRACK|SLAB_ACCOUNT,
2107 fs_cachep = kmem_cache_create("fs_cache",
2108 sizeof(struct fs_struct), 0,
2109 SLAB_HWCACHE_ALIGN|SLAB_PANIC|SLAB_NOTRACK|SLAB_ACCOUNT,
2112 * FIXME! The "sizeof(struct mm_struct)" currently includes the
2113 * whole struct cpumask for the OFFSTACK case. We could change
2114 * this to *only* allocate as much of it as required by the
2115 * maximum number of CPU's we can ever have. The cpumask_allocation
2116 * is at the end of the structure, exactly for that reason.
2118 mm_cachep = kmem_cache_create("mm_struct",
2119 sizeof(struct mm_struct), ARCH_MIN_MMSTRUCT_ALIGN,
2120 SLAB_HWCACHE_ALIGN|SLAB_PANIC|SLAB_NOTRACK|SLAB_ACCOUNT,
2122 vm_area_cachep = KMEM_CACHE(vm_area_struct, SLAB_PANIC|SLAB_ACCOUNT);
2124 nsproxy_cache_init();
2128 * Check constraints on flags passed to the unshare system call.
2130 static int check_unshare_flags(unsigned long unshare_flags)
2132 if (unshare_flags & ~(CLONE_THREAD|CLONE_FS|CLONE_NEWNS|CLONE_SIGHAND|
2133 CLONE_VM|CLONE_FILES|CLONE_SYSVSEM|
2134 CLONE_NEWUTS|CLONE_NEWIPC|CLONE_NEWNET|
2135 CLONE_NEWUSER|CLONE_NEWPID|CLONE_NEWCGROUP))
2138 * Not implemented, but pretend it works if there is nothing
2139 * to unshare. Note that unsharing the address space or the
2140 * signal handlers also need to unshare the signal queues (aka
2143 if (unshare_flags & (CLONE_THREAD | CLONE_SIGHAND | CLONE_VM)) {
2144 if (!thread_group_empty(current))
2147 if (unshare_flags & (CLONE_SIGHAND | CLONE_VM)) {
2148 if (atomic_read(¤t->sighand->count) > 1)
2151 if (unshare_flags & CLONE_VM) {
2152 if (!current_is_single_threaded())
2160 * Unshare the filesystem structure if it is being shared
2162 static int unshare_fs(unsigned long unshare_flags, struct fs_struct **new_fsp)
2164 struct fs_struct *fs = current->fs;
2166 if (!(unshare_flags & CLONE_FS) || !fs)
2169 /* don't need lock here; in the worst case we'll do useless copy */
2173 *new_fsp = copy_fs_struct(fs);
2181 * Unshare file descriptor table if it is being shared
2183 static int unshare_fd(unsigned long unshare_flags, struct files_struct **new_fdp)
2185 struct files_struct *fd = current->files;
2188 if ((unshare_flags & CLONE_FILES) &&
2189 (fd && atomic_read(&fd->count) > 1)) {
2190 *new_fdp = dup_fd(fd, &error);
2199 * unshare allows a process to 'unshare' part of the process
2200 * context which was originally shared using clone. copy_*
2201 * functions used by do_fork() cannot be used here directly
2202 * because they modify an inactive task_struct that is being
2203 * constructed. Here we are modifying the current, active,
2206 SYSCALL_DEFINE1(unshare, unsigned long, unshare_flags)
2208 struct fs_struct *fs, *new_fs = NULL;
2209 struct files_struct *fd, *new_fd = NULL;
2210 struct cred *new_cred = NULL;
2211 struct nsproxy *new_nsproxy = NULL;
2216 * If unsharing a user namespace must also unshare the thread group
2217 * and unshare the filesystem root and working directories.
2219 if (unshare_flags & CLONE_NEWUSER)
2220 unshare_flags |= CLONE_THREAD | CLONE_FS;
2222 * If unsharing vm, must also unshare signal handlers.
2224 if (unshare_flags & CLONE_VM)
2225 unshare_flags |= CLONE_SIGHAND;
2227 * If unsharing a signal handlers, must also unshare the signal queues.
2229 if (unshare_flags & CLONE_SIGHAND)
2230 unshare_flags |= CLONE_THREAD;
2232 * If unsharing namespace, must also unshare filesystem information.
2234 if (unshare_flags & CLONE_NEWNS)
2235 unshare_flags |= CLONE_FS;
2237 err = check_unshare_flags(unshare_flags);
2239 goto bad_unshare_out;
2241 * CLONE_NEWIPC must also detach from the undolist: after switching
2242 * to a new ipc namespace, the semaphore arrays from the old
2243 * namespace are unreachable.
2245 if (unshare_flags & (CLONE_NEWIPC|CLONE_SYSVSEM))
2247 err = unshare_fs(unshare_flags, &new_fs);
2249 goto bad_unshare_out;
2250 err = unshare_fd(unshare_flags, &new_fd);
2252 goto bad_unshare_cleanup_fs;
2253 err = unshare_userns(unshare_flags, &new_cred);
2255 goto bad_unshare_cleanup_fd;
2256 err = unshare_nsproxy_namespaces(unshare_flags, &new_nsproxy,
2259 goto bad_unshare_cleanup_cred;
2261 if (new_fs || new_fd || do_sysvsem || new_cred || new_nsproxy) {
2264 * CLONE_SYSVSEM is equivalent to sys_exit().
2268 if (unshare_flags & CLONE_NEWIPC) {
2269 /* Orphan segments in old ns (see sem above). */
2271 shm_init_task(current);
2275 switch_task_namespaces(current, new_nsproxy);
2281 spin_lock(&fs->lock);
2282 current->fs = new_fs;
2287 spin_unlock(&fs->lock);
2291 fd = current->files;
2292 current->files = new_fd;
2296 task_unlock(current);
2299 /* Install the new user namespace */
2300 commit_creds(new_cred);
2305 bad_unshare_cleanup_cred:
2308 bad_unshare_cleanup_fd:
2310 put_files_struct(new_fd);
2312 bad_unshare_cleanup_fs:
2314 free_fs_struct(new_fs);
2321 * Helper to unshare the files of the current task.
2322 * We don't want to expose copy_files internals to
2323 * the exec layer of the kernel.
2326 int unshare_files(struct files_struct **displaced)
2328 struct task_struct *task = current;
2329 struct files_struct *copy = NULL;
2332 error = unshare_fd(CLONE_FILES, ©);
2333 if (error || !copy) {
2337 *displaced = task->files;
2344 int sysctl_max_threads(struct ctl_table *table, int write,
2345 void __user *buffer, size_t *lenp, loff_t *ppos)
2349 int threads = max_threads;
2351 int max = MAX_THREADS;
2358 ret = proc_dointvec_minmax(&t, write, buffer, lenp, ppos);
2362 max_threads = threads;