Merge branch 'linus' into sched/urgent, to resolve conflicts
[muen/linux.git] / kernel / fork.c
1 /*
2  *  linux/kernel/fork.c
3  *
4  *  Copyright (C) 1991, 1992  Linus Torvalds
5  */
6
7 /*
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()'
12  */
13
14 #include <linux/slab.h>
15 #include <linux/sched/autogroup.h>
16 #include <linux/sched/mm.h>
17 #include <linux/sched/coredump.h>
18 #include <linux/sched/user.h>
19 #include <linux/sched/numa_balancing.h>
20 #include <linux/sched/stat.h>
21 #include <linux/sched/task.h>
22 #include <linux/sched/task_stack.h>
23 #include <linux/sched/cputime.h>
24 #include <linux/rtmutex.h>
25 #include <linux/init.h>
26 #include <linux/unistd.h>
27 #include <linux/module.h>
28 #include <linux/vmalloc.h>
29 #include <linux/completion.h>
30 #include <linux/personality.h>
31 #include <linux/mempolicy.h>
32 #include <linux/sem.h>
33 #include <linux/file.h>
34 #include <linux/fdtable.h>
35 #include <linux/iocontext.h>
36 #include <linux/key.h>
37 #include <linux/binfmts.h>
38 #include <linux/mman.h>
39 #include <linux/mmu_notifier.h>
40 #include <linux/hmm.h>
41 #include <linux/fs.h>
42 #include <linux/mm.h>
43 #include <linux/vmacache.h>
44 #include <linux/nsproxy.h>
45 #include <linux/capability.h>
46 #include <linux/cpu.h>
47 #include <linux/cgroup.h>
48 #include <linux/security.h>
49 #include <linux/hugetlb.h>
50 #include <linux/seccomp.h>
51 #include <linux/swap.h>
52 #include <linux/syscalls.h>
53 #include <linux/jiffies.h>
54 #include <linux/futex.h>
55 #include <linux/compat.h>
56 #include <linux/kthread.h>
57 #include <linux/task_io_accounting_ops.h>
58 #include <linux/rcupdate.h>
59 #include <linux/ptrace.h>
60 #include <linux/mount.h>
61 #include <linux/audit.h>
62 #include <linux/memcontrol.h>
63 #include <linux/ftrace.h>
64 #include <linux/proc_fs.h>
65 #include <linux/profile.h>
66 #include <linux/rmap.h>
67 #include <linux/ksm.h>
68 #include <linux/acct.h>
69 #include <linux/userfaultfd_k.h>
70 #include <linux/tsacct_kern.h>
71 #include <linux/cn_proc.h>
72 #include <linux/freezer.h>
73 #include <linux/delayacct.h>
74 #include <linux/taskstats_kern.h>
75 #include <linux/random.h>
76 #include <linux/tty.h>
77 #include <linux/blkdev.h>
78 #include <linux/fs_struct.h>
79 #include <linux/magic.h>
80 #include <linux/sched/mm.h>
81 #include <linux/perf_event.h>
82 #include <linux/posix-timers.h>
83 #include <linux/user-return-notifier.h>
84 #include <linux/oom.h>
85 #include <linux/khugepaged.h>
86 #include <linux/signalfd.h>
87 #include <linux/uprobes.h>
88 #include <linux/aio.h>
89 #include <linux/compiler.h>
90 #include <linux/sysctl.h>
91 #include <linux/kcov.h>
92 #include <linux/livepatch.h>
93 #include <linux/thread_info.h>
94
95 #include <asm/pgtable.h>
96 #include <asm/pgalloc.h>
97 #include <linux/uaccess.h>
98 #include <asm/mmu_context.h>
99 #include <asm/cacheflush.h>
100 #include <asm/tlbflush.h>
101
102 #include <trace/events/sched.h>
103
104 #define CREATE_TRACE_POINTS
105 #include <trace/events/task.h>
106
107 /*
108  * Minimum number of threads to boot the kernel
109  */
110 #define MIN_THREADS 20
111
112 /*
113  * Maximum number of threads
114  */
115 #define MAX_THREADS FUTEX_TID_MASK
116
117 /*
118  * Protected counters by write_lock_irq(&tasklist_lock)
119  */
120 unsigned long total_forks;      /* Handle normal Linux uptimes. */
121 int nr_threads;                 /* The idle threads do not count.. */
122
123 int max_threads;                /* tunable limit on nr_threads */
124
125 DEFINE_PER_CPU(unsigned long, process_counts) = 0;
126
127 __cacheline_aligned DEFINE_RWLOCK(tasklist_lock);  /* outer */
128
129 #ifdef CONFIG_PROVE_RCU
130 int lockdep_tasklist_lock_is_held(void)
131 {
132         return lockdep_is_held(&tasklist_lock);
133 }
134 EXPORT_SYMBOL_GPL(lockdep_tasklist_lock_is_held);
135 #endif /* #ifdef CONFIG_PROVE_RCU */
136
137 int nr_processes(void)
138 {
139         int cpu;
140         int total = 0;
141
142         for_each_possible_cpu(cpu)
143                 total += per_cpu(process_counts, cpu);
144
145         return total;
146 }
147
148 void __weak arch_release_task_struct(struct task_struct *tsk)
149 {
150 }
151
152 #ifndef CONFIG_ARCH_TASK_STRUCT_ALLOCATOR
153 static struct kmem_cache *task_struct_cachep;
154
155 static inline struct task_struct *alloc_task_struct_node(int node)
156 {
157         return kmem_cache_alloc_node(task_struct_cachep, GFP_KERNEL, node);
158 }
159
160 static inline void free_task_struct(struct task_struct *tsk)
161 {
162         kmem_cache_free(task_struct_cachep, tsk);
163 }
164 #endif
165
166 void __weak arch_release_thread_stack(unsigned long *stack)
167 {
168 }
169
170 #ifndef CONFIG_ARCH_THREAD_STACK_ALLOCATOR
171
172 /*
173  * Allocate pages if THREAD_SIZE is >= PAGE_SIZE, otherwise use a
174  * kmemcache based allocator.
175  */
176 # if THREAD_SIZE >= PAGE_SIZE || defined(CONFIG_VMAP_STACK)
177
178 #ifdef CONFIG_VMAP_STACK
179 /*
180  * vmalloc() is a bit slow, and calling vfree() enough times will force a TLB
181  * flush.  Try to minimize the number of calls by caching stacks.
182  */
183 #define NR_CACHED_STACKS 2
184 static DEFINE_PER_CPU(struct vm_struct *, cached_stacks[NR_CACHED_STACKS]);
185
186 static int free_vm_stack_cache(unsigned int cpu)
187 {
188         struct vm_struct **cached_vm_stacks = per_cpu_ptr(cached_stacks, cpu);
189         int i;
190
191         for (i = 0; i < NR_CACHED_STACKS; i++) {
192                 struct vm_struct *vm_stack = cached_vm_stacks[i];
193
194                 if (!vm_stack)
195                         continue;
196
197                 vfree(vm_stack->addr);
198                 cached_vm_stacks[i] = NULL;
199         }
200
201         return 0;
202 }
203 #endif
204
205 static unsigned long *alloc_thread_stack_node(struct task_struct *tsk, int node)
206 {
207 #ifdef CONFIG_VMAP_STACK
208         void *stack;
209         int i;
210
211         for (i = 0; i < NR_CACHED_STACKS; i++) {
212                 struct vm_struct *s;
213
214                 s = this_cpu_xchg(cached_stacks[i], NULL);
215
216                 if (!s)
217                         continue;
218
219 #ifdef CONFIG_DEBUG_KMEMLEAK
220                 /* Clear stale pointers from reused stack. */
221                 memset(s->addr, 0, THREAD_SIZE);
222 #endif
223                 tsk->stack_vm_area = s;
224                 return s->addr;
225         }
226
227         stack = __vmalloc_node_range(THREAD_SIZE, THREAD_ALIGN,
228                                      VMALLOC_START, VMALLOC_END,
229                                      THREADINFO_GFP,
230                                      PAGE_KERNEL,
231                                      0, node, __builtin_return_address(0));
232
233         /*
234          * We can't call find_vm_area() in interrupt context, and
235          * free_thread_stack() can be called in interrupt context,
236          * so cache the vm_struct.
237          */
238         if (stack)
239                 tsk->stack_vm_area = find_vm_area(stack);
240         return stack;
241 #else
242         struct page *page = alloc_pages_node(node, THREADINFO_GFP,
243                                              THREAD_SIZE_ORDER);
244
245         return page ? page_address(page) : NULL;
246 #endif
247 }
248
249 static inline void free_thread_stack(struct task_struct *tsk)
250 {
251 #ifdef CONFIG_VMAP_STACK
252         if (task_stack_vm_area(tsk)) {
253                 int i;
254
255                 for (i = 0; i < NR_CACHED_STACKS; i++) {
256                         if (this_cpu_cmpxchg(cached_stacks[i],
257                                         NULL, tsk->stack_vm_area) != NULL)
258                                 continue;
259
260                         return;
261                 }
262
263                 vfree_atomic(tsk->stack);
264                 return;
265         }
266 #endif
267
268         __free_pages(virt_to_page(tsk->stack), THREAD_SIZE_ORDER);
269 }
270 # else
271 static struct kmem_cache *thread_stack_cache;
272
273 static unsigned long *alloc_thread_stack_node(struct task_struct *tsk,
274                                                   int node)
275 {
276         return kmem_cache_alloc_node(thread_stack_cache, THREADINFO_GFP, node);
277 }
278
279 static void free_thread_stack(struct task_struct *tsk)
280 {
281         kmem_cache_free(thread_stack_cache, tsk->stack);
282 }
283
284 void thread_stack_cache_init(void)
285 {
286         thread_stack_cache = kmem_cache_create_usercopy("thread_stack",
287                                         THREAD_SIZE, THREAD_SIZE, 0, 0,
288                                         THREAD_SIZE, NULL);
289         BUG_ON(thread_stack_cache == NULL);
290 }
291 # endif
292 #endif
293
294 /* SLAB cache for signal_struct structures (tsk->signal) */
295 static struct kmem_cache *signal_cachep;
296
297 /* SLAB cache for sighand_struct structures (tsk->sighand) */
298 struct kmem_cache *sighand_cachep;
299
300 /* SLAB cache for files_struct structures (tsk->files) */
301 struct kmem_cache *files_cachep;
302
303 /* SLAB cache for fs_struct structures (tsk->fs) */
304 struct kmem_cache *fs_cachep;
305
306 /* SLAB cache for vm_area_struct structures */
307 struct kmem_cache *vm_area_cachep;
308
309 /* SLAB cache for mm_struct structures (tsk->mm) */
310 static struct kmem_cache *mm_cachep;
311
312 static void account_kernel_stack(struct task_struct *tsk, int account)
313 {
314         void *stack = task_stack_page(tsk);
315         struct vm_struct *vm = task_stack_vm_area(tsk);
316
317         BUILD_BUG_ON(IS_ENABLED(CONFIG_VMAP_STACK) && PAGE_SIZE % 1024 != 0);
318
319         if (vm) {
320                 int i;
321
322                 BUG_ON(vm->nr_pages != THREAD_SIZE / PAGE_SIZE);
323
324                 for (i = 0; i < THREAD_SIZE / PAGE_SIZE; i++) {
325                         mod_zone_page_state(page_zone(vm->pages[i]),
326                                             NR_KERNEL_STACK_KB,
327                                             PAGE_SIZE / 1024 * account);
328                 }
329
330                 /* All stack pages belong to the same memcg. */
331                 mod_memcg_page_state(vm->pages[0], MEMCG_KERNEL_STACK_KB,
332                                      account * (THREAD_SIZE / 1024));
333         } else {
334                 /*
335                  * All stack pages are in the same zone and belong to the
336                  * same memcg.
337                  */
338                 struct page *first_page = virt_to_page(stack);
339
340                 mod_zone_page_state(page_zone(first_page), NR_KERNEL_STACK_KB,
341                                     THREAD_SIZE / 1024 * account);
342
343                 mod_memcg_page_state(first_page, MEMCG_KERNEL_STACK_KB,
344                                      account * (THREAD_SIZE / 1024));
345         }
346 }
347
348 static void release_task_stack(struct task_struct *tsk)
349 {
350         if (WARN_ON(tsk->state != TASK_DEAD))
351                 return;  /* Better to leak the stack than to free prematurely */
352
353         account_kernel_stack(tsk, -1);
354         arch_release_thread_stack(tsk->stack);
355         free_thread_stack(tsk);
356         tsk->stack = NULL;
357 #ifdef CONFIG_VMAP_STACK
358         tsk->stack_vm_area = NULL;
359 #endif
360 }
361
362 #ifdef CONFIG_THREAD_INFO_IN_TASK
363 void put_task_stack(struct task_struct *tsk)
364 {
365         if (atomic_dec_and_test(&tsk->stack_refcount))
366                 release_task_stack(tsk);
367 }
368 #endif
369
370 void free_task(struct task_struct *tsk)
371 {
372 #ifndef CONFIG_THREAD_INFO_IN_TASK
373         /*
374          * The task is finally done with both the stack and thread_info,
375          * so free both.
376          */
377         release_task_stack(tsk);
378 #else
379         /*
380          * If the task had a separate stack allocation, it should be gone
381          * by now.
382          */
383         WARN_ON_ONCE(atomic_read(&tsk->stack_refcount) != 0);
384 #endif
385         rt_mutex_debug_task_free(tsk);
386         ftrace_graph_exit_task(tsk);
387         put_seccomp_filter(tsk);
388         arch_release_task_struct(tsk);
389         if (tsk->flags & PF_KTHREAD)
390                 free_kthread_struct(tsk);
391         free_task_struct(tsk);
392 }
393 EXPORT_SYMBOL(free_task);
394
395 #ifdef CONFIG_MMU
396 static __latent_entropy int dup_mmap(struct mm_struct *mm,
397                                         struct mm_struct *oldmm)
398 {
399         struct vm_area_struct *mpnt, *tmp, *prev, **pprev;
400         struct rb_node **rb_link, *rb_parent;
401         int retval;
402         unsigned long charge;
403         LIST_HEAD(uf);
404
405         uprobe_start_dup_mmap();
406         if (down_write_killable(&oldmm->mmap_sem)) {
407                 retval = -EINTR;
408                 goto fail_uprobe_end;
409         }
410         flush_cache_dup_mm(oldmm);
411         uprobe_dup_mmap(oldmm, mm);
412         /*
413          * Not linked in yet - no deadlock potential:
414          */
415         down_write_nested(&mm->mmap_sem, SINGLE_DEPTH_NESTING);
416
417         /* No ordering required: file already has been exposed. */
418         RCU_INIT_POINTER(mm->exe_file, get_mm_exe_file(oldmm));
419
420         mm->total_vm = oldmm->total_vm;
421         mm->data_vm = oldmm->data_vm;
422         mm->exec_vm = oldmm->exec_vm;
423         mm->stack_vm = oldmm->stack_vm;
424
425         rb_link = &mm->mm_rb.rb_node;
426         rb_parent = NULL;
427         pprev = &mm->mmap;
428         retval = ksm_fork(mm, oldmm);
429         if (retval)
430                 goto out;
431         retval = khugepaged_fork(mm, oldmm);
432         if (retval)
433                 goto out;
434
435         prev = NULL;
436         for (mpnt = oldmm->mmap; mpnt; mpnt = mpnt->vm_next) {
437                 struct file *file;
438
439                 if (mpnt->vm_flags & VM_DONTCOPY) {
440                         vm_stat_account(mm, mpnt->vm_flags, -vma_pages(mpnt));
441                         continue;
442                 }
443                 charge = 0;
444                 if (mpnt->vm_flags & VM_ACCOUNT) {
445                         unsigned long len = vma_pages(mpnt);
446
447                         if (security_vm_enough_memory_mm(oldmm, len)) /* sic */
448                                 goto fail_nomem;
449                         charge = len;
450                 }
451                 tmp = kmem_cache_alloc(vm_area_cachep, GFP_KERNEL);
452                 if (!tmp)
453                         goto fail_nomem;
454                 *tmp = *mpnt;
455                 INIT_LIST_HEAD(&tmp->anon_vma_chain);
456                 retval = vma_dup_policy(mpnt, tmp);
457                 if (retval)
458                         goto fail_nomem_policy;
459                 tmp->vm_mm = mm;
460                 retval = dup_userfaultfd(tmp, &uf);
461                 if (retval)
462                         goto fail_nomem_anon_vma_fork;
463                 if (tmp->vm_flags & VM_WIPEONFORK) {
464                         /* VM_WIPEONFORK gets a clean slate in the child. */
465                         tmp->anon_vma = NULL;
466                         if (anon_vma_prepare(tmp))
467                                 goto fail_nomem_anon_vma_fork;
468                 } else if (anon_vma_fork(tmp, mpnt))
469                         goto fail_nomem_anon_vma_fork;
470                 tmp->vm_flags &= ~(VM_LOCKED | VM_LOCKONFAULT);
471                 tmp->vm_next = tmp->vm_prev = NULL;
472                 file = tmp->vm_file;
473                 if (file) {
474                         struct inode *inode = file_inode(file);
475                         struct address_space *mapping = file->f_mapping;
476
477                         get_file(file);
478                         if (tmp->vm_flags & VM_DENYWRITE)
479                                 atomic_dec(&inode->i_writecount);
480                         i_mmap_lock_write(mapping);
481                         if (tmp->vm_flags & VM_SHARED)
482                                 atomic_inc(&mapping->i_mmap_writable);
483                         flush_dcache_mmap_lock(mapping);
484                         /* insert tmp into the share list, just after mpnt */
485                         vma_interval_tree_insert_after(tmp, mpnt,
486                                         &mapping->i_mmap);
487                         flush_dcache_mmap_unlock(mapping);
488                         i_mmap_unlock_write(mapping);
489                 }
490
491                 /*
492                  * Clear hugetlb-related page reserves for children. This only
493                  * affects MAP_PRIVATE mappings. Faults generated by the child
494                  * are not guaranteed to succeed, even if read-only
495                  */
496                 if (is_vm_hugetlb_page(tmp))
497                         reset_vma_resv_huge_pages(tmp);
498
499                 /*
500                  * Link in the new vma and copy the page table entries.
501                  */
502                 *pprev = tmp;
503                 pprev = &tmp->vm_next;
504                 tmp->vm_prev = prev;
505                 prev = tmp;
506
507                 __vma_link_rb(mm, tmp, rb_link, rb_parent);
508                 rb_link = &tmp->vm_rb.rb_right;
509                 rb_parent = &tmp->vm_rb;
510
511                 mm->map_count++;
512                 if (!(tmp->vm_flags & VM_WIPEONFORK))
513                         retval = copy_page_range(mm, oldmm, mpnt);
514
515                 if (tmp->vm_ops && tmp->vm_ops->open)
516                         tmp->vm_ops->open(tmp);
517
518                 if (retval)
519                         goto out;
520         }
521         /* a new mm has just been created */
522         arch_dup_mmap(oldmm, mm);
523         retval = 0;
524 out:
525         up_write(&mm->mmap_sem);
526         flush_tlb_mm(oldmm);
527         up_write(&oldmm->mmap_sem);
528         dup_userfaultfd_complete(&uf);
529 fail_uprobe_end:
530         uprobe_end_dup_mmap();
531         return retval;
532 fail_nomem_anon_vma_fork:
533         mpol_put(vma_policy(tmp));
534 fail_nomem_policy:
535         kmem_cache_free(vm_area_cachep, tmp);
536 fail_nomem:
537         retval = -ENOMEM;
538         vm_unacct_memory(charge);
539         goto out;
540 }
541
542 static inline int mm_alloc_pgd(struct mm_struct *mm)
543 {
544         mm->pgd = pgd_alloc(mm);
545         if (unlikely(!mm->pgd))
546                 return -ENOMEM;
547         return 0;
548 }
549
550 static inline void mm_free_pgd(struct mm_struct *mm)
551 {
552         pgd_free(mm, mm->pgd);
553 }
554 #else
555 static int dup_mmap(struct mm_struct *mm, struct mm_struct *oldmm)
556 {
557         down_write(&oldmm->mmap_sem);
558         RCU_INIT_POINTER(mm->exe_file, get_mm_exe_file(oldmm));
559         up_write(&oldmm->mmap_sem);
560         return 0;
561 }
562 #define mm_alloc_pgd(mm)        (0)
563 #define mm_free_pgd(mm)
564 #endif /* CONFIG_MMU */
565
566 static void check_mm(struct mm_struct *mm)
567 {
568         int i;
569
570         for (i = 0; i < NR_MM_COUNTERS; i++) {
571                 long x = atomic_long_read(&mm->rss_stat.count[i]);
572
573                 if (unlikely(x))
574                         printk(KERN_ALERT "BUG: Bad rss-counter state "
575                                           "mm:%p idx:%d val:%ld\n", mm, i, x);
576         }
577
578         if (mm_pgtables_bytes(mm))
579                 pr_alert("BUG: non-zero pgtables_bytes on freeing mm: %ld\n",
580                                 mm_pgtables_bytes(mm));
581
582 #if defined(CONFIG_TRANSPARENT_HUGEPAGE) && !USE_SPLIT_PMD_PTLOCKS
583         VM_BUG_ON_MM(mm->pmd_huge_pte, mm);
584 #endif
585 }
586
587 #define allocate_mm()   (kmem_cache_alloc(mm_cachep, GFP_KERNEL))
588 #define free_mm(mm)     (kmem_cache_free(mm_cachep, (mm)))
589
590 /*
591  * Called when the last reference to the mm
592  * is dropped: either by a lazy thread or by
593  * mmput. Free the page directory and the mm.
594  */
595 static void __mmdrop(struct mm_struct *mm)
596 {
597         BUG_ON(mm == &init_mm);
598         mm_free_pgd(mm);
599         destroy_context(mm);
600         hmm_mm_destroy(mm);
601         mmu_notifier_mm_destroy(mm);
602         check_mm(mm);
603         put_user_ns(mm->user_ns);
604         free_mm(mm);
605 }
606
607 void mmdrop(struct mm_struct *mm)
608 {
609         /*
610          * The implicit full barrier implied by atomic_dec_and_test() is
611          * required by the membarrier system call before returning to
612          * user-space, after storing to rq->curr.
613          */
614         if (unlikely(atomic_dec_and_test(&mm->mm_count)))
615                 __mmdrop(mm);
616 }
617 EXPORT_SYMBOL_GPL(mmdrop);
618
619 static void mmdrop_async_fn(struct work_struct *work)
620 {
621         struct mm_struct *mm;
622
623         mm = container_of(work, struct mm_struct, async_put_work);
624         __mmdrop(mm);
625 }
626
627 static void mmdrop_async(struct mm_struct *mm)
628 {
629         if (unlikely(atomic_dec_and_test(&mm->mm_count))) {
630                 INIT_WORK(&mm->async_put_work, mmdrop_async_fn);
631                 schedule_work(&mm->async_put_work);
632         }
633 }
634
635 static inline void free_signal_struct(struct signal_struct *sig)
636 {
637         taskstats_tgid_free(sig);
638         sched_autogroup_exit(sig);
639         /*
640          * __mmdrop is not safe to call from softirq context on x86 due to
641          * pgd_dtor so postpone it to the async context
642          */
643         if (sig->oom_mm)
644                 mmdrop_async(sig->oom_mm);
645         kmem_cache_free(signal_cachep, sig);
646 }
647
648 static inline void put_signal_struct(struct signal_struct *sig)
649 {
650         if (atomic_dec_and_test(&sig->sigcnt))
651                 free_signal_struct(sig);
652 }
653
654 void __put_task_struct(struct task_struct *tsk)
655 {
656         WARN_ON(!tsk->exit_state);
657         WARN_ON(atomic_read(&tsk->usage));
658         WARN_ON(tsk == current);
659
660         cgroup_free(tsk);
661         task_numa_free(tsk);
662         security_task_free(tsk);
663         exit_creds(tsk);
664         delayacct_tsk_free(tsk);
665         put_signal_struct(tsk->signal);
666
667         if (!profile_handoff_task(tsk))
668                 free_task(tsk);
669 }
670 EXPORT_SYMBOL_GPL(__put_task_struct);
671
672 void __init __weak arch_task_cache_init(void) { }
673
674 /*
675  * set_max_threads
676  */
677 static void set_max_threads(unsigned int max_threads_suggested)
678 {
679         u64 threads;
680
681         /*
682          * The number of threads shall be limited such that the thread
683          * structures may only consume a small part of the available memory.
684          */
685         if (fls64(totalram_pages) + fls64(PAGE_SIZE) > 64)
686                 threads = MAX_THREADS;
687         else
688                 threads = div64_u64((u64) totalram_pages * (u64) PAGE_SIZE,
689                                     (u64) THREAD_SIZE * 8UL);
690
691         if (threads > max_threads_suggested)
692                 threads = max_threads_suggested;
693
694         max_threads = clamp_t(u64, threads, MIN_THREADS, MAX_THREADS);
695 }
696
697 #ifdef CONFIG_ARCH_WANTS_DYNAMIC_TASK_STRUCT
698 /* Initialized by the architecture: */
699 int arch_task_struct_size __read_mostly;
700 #endif
701
702 static void task_struct_whitelist(unsigned long *offset, unsigned long *size)
703 {
704         /* Fetch thread_struct whitelist for the architecture. */
705         arch_thread_struct_whitelist(offset, size);
706
707         /*
708          * Handle zero-sized whitelist or empty thread_struct, otherwise
709          * adjust offset to position of thread_struct in task_struct.
710          */
711         if (unlikely(*size == 0))
712                 *offset = 0;
713         else
714                 *offset += offsetof(struct task_struct, thread);
715 }
716
717 void __init fork_init(void)
718 {
719         int i;
720 #ifndef CONFIG_ARCH_TASK_STRUCT_ALLOCATOR
721 #ifndef ARCH_MIN_TASKALIGN
722 #define ARCH_MIN_TASKALIGN      0
723 #endif
724         int align = max_t(int, L1_CACHE_BYTES, ARCH_MIN_TASKALIGN);
725         unsigned long useroffset, usersize;
726
727         /* create a slab on which task_structs can be allocated */
728         task_struct_whitelist(&useroffset, &usersize);
729         task_struct_cachep = kmem_cache_create_usercopy("task_struct",
730                         arch_task_struct_size, align,
731                         SLAB_PANIC|SLAB_ACCOUNT,
732                         useroffset, usersize, NULL);
733 #endif
734
735         /* do the arch specific task caches init */
736         arch_task_cache_init();
737
738         set_max_threads(MAX_THREADS);
739
740         init_task.signal->rlim[RLIMIT_NPROC].rlim_cur = max_threads/2;
741         init_task.signal->rlim[RLIMIT_NPROC].rlim_max = max_threads/2;
742         init_task.signal->rlim[RLIMIT_SIGPENDING] =
743                 init_task.signal->rlim[RLIMIT_NPROC];
744
745         for (i = 0; i < UCOUNT_COUNTS; i++) {
746                 init_user_ns.ucount_max[i] = max_threads/2;
747         }
748
749 #ifdef CONFIG_VMAP_STACK
750         cpuhp_setup_state(CPUHP_BP_PREPARE_DYN, "fork:vm_stack_cache",
751                           NULL, free_vm_stack_cache);
752 #endif
753
754         lockdep_init_task(&init_task);
755 }
756
757 int __weak arch_dup_task_struct(struct task_struct *dst,
758                                                struct task_struct *src)
759 {
760         *dst = *src;
761         return 0;
762 }
763
764 void set_task_stack_end_magic(struct task_struct *tsk)
765 {
766         unsigned long *stackend;
767
768         stackend = end_of_stack(tsk);
769         *stackend = STACK_END_MAGIC;    /* for overflow detection */
770 }
771
772 static struct task_struct *dup_task_struct(struct task_struct *orig, int node)
773 {
774         struct task_struct *tsk;
775         unsigned long *stack;
776         struct vm_struct *stack_vm_area;
777         int err;
778
779         if (node == NUMA_NO_NODE)
780                 node = tsk_fork_get_node(orig);
781         tsk = alloc_task_struct_node(node);
782         if (!tsk)
783                 return NULL;
784
785         stack = alloc_thread_stack_node(tsk, node);
786         if (!stack)
787                 goto free_tsk;
788
789         stack_vm_area = task_stack_vm_area(tsk);
790
791         err = arch_dup_task_struct(tsk, orig);
792
793         /*
794          * arch_dup_task_struct() clobbers the stack-related fields.  Make
795          * sure they're properly initialized before using any stack-related
796          * functions again.
797          */
798         tsk->stack = stack;
799 #ifdef CONFIG_VMAP_STACK
800         tsk->stack_vm_area = stack_vm_area;
801 #endif
802 #ifdef CONFIG_THREAD_INFO_IN_TASK
803         atomic_set(&tsk->stack_refcount, 1);
804 #endif
805
806         if (err)
807                 goto free_stack;
808
809 #ifdef CONFIG_SECCOMP
810         /*
811          * We must handle setting up seccomp filters once we're under
812          * the sighand lock in case orig has changed between now and
813          * then. Until then, filter must be NULL to avoid messing up
814          * the usage counts on the error path calling free_task.
815          */
816         tsk->seccomp.filter = NULL;
817 #endif
818
819         setup_thread_stack(tsk, orig);
820         clear_user_return_notifier(tsk);
821         clear_tsk_need_resched(tsk);
822         set_task_stack_end_magic(tsk);
823
824 #ifdef CONFIG_CC_STACKPROTECTOR
825         tsk->stack_canary = get_random_canary();
826 #endif
827
828         /*
829          * One for us, one for whoever does the "release_task()" (usually
830          * parent)
831          */
832         atomic_set(&tsk->usage, 2);
833 #ifdef CONFIG_BLK_DEV_IO_TRACE
834         tsk->btrace_seq = 0;
835 #endif
836         tsk->splice_pipe = NULL;
837         tsk->task_frag.page = NULL;
838         tsk->wake_q.next = NULL;
839
840         account_kernel_stack(tsk, 1);
841
842         kcov_task_init(tsk);
843
844 #ifdef CONFIG_FAULT_INJECTION
845         tsk->fail_nth = 0;
846 #endif
847
848         return tsk;
849
850 free_stack:
851         free_thread_stack(tsk);
852 free_tsk:
853         free_task_struct(tsk);
854         return NULL;
855 }
856
857 __cacheline_aligned_in_smp DEFINE_SPINLOCK(mmlist_lock);
858
859 static unsigned long default_dump_filter = MMF_DUMP_FILTER_DEFAULT;
860
861 static int __init coredump_filter_setup(char *s)
862 {
863         default_dump_filter =
864                 (simple_strtoul(s, NULL, 0) << MMF_DUMP_FILTER_SHIFT) &
865                 MMF_DUMP_FILTER_MASK;
866         return 1;
867 }
868
869 __setup("coredump_filter=", coredump_filter_setup);
870
871 #include <linux/init_task.h>
872
873 static void mm_init_aio(struct mm_struct *mm)
874 {
875 #ifdef CONFIG_AIO
876         spin_lock_init(&mm->ioctx_lock);
877         mm->ioctx_table = NULL;
878 #endif
879 }
880
881 static void mm_init_owner(struct mm_struct *mm, struct task_struct *p)
882 {
883 #ifdef CONFIG_MEMCG
884         mm->owner = p;
885 #endif
886 }
887
888 static void mm_init_uprobes_state(struct mm_struct *mm)
889 {
890 #ifdef CONFIG_UPROBES
891         mm->uprobes_state.xol_area = NULL;
892 #endif
893 }
894
895 static struct mm_struct *mm_init(struct mm_struct *mm, struct task_struct *p,
896         struct user_namespace *user_ns)
897 {
898         mm->mmap = NULL;
899         mm->mm_rb = RB_ROOT;
900         mm->vmacache_seqnum = 0;
901         atomic_set(&mm->mm_users, 1);
902         atomic_set(&mm->mm_count, 1);
903         init_rwsem(&mm->mmap_sem);
904         INIT_LIST_HEAD(&mm->mmlist);
905         mm->core_state = NULL;
906         mm_pgtables_bytes_init(mm);
907         mm->map_count = 0;
908         mm->locked_vm = 0;
909         mm->pinned_vm = 0;
910         memset(&mm->rss_stat, 0, sizeof(mm->rss_stat));
911         spin_lock_init(&mm->page_table_lock);
912         mm_init_cpumask(mm);
913         mm_init_aio(mm);
914         mm_init_owner(mm, p);
915         RCU_INIT_POINTER(mm->exe_file, NULL);
916         mmu_notifier_mm_init(mm);
917         hmm_mm_init(mm);
918         init_tlb_flush_pending(mm);
919 #if defined(CONFIG_TRANSPARENT_HUGEPAGE) && !USE_SPLIT_PMD_PTLOCKS
920         mm->pmd_huge_pte = NULL;
921 #endif
922         mm_init_uprobes_state(mm);
923
924         if (current->mm) {
925                 mm->flags = current->mm->flags & MMF_INIT_MASK;
926                 mm->def_flags = current->mm->def_flags & VM_INIT_DEF_MASK;
927         } else {
928                 mm->flags = default_dump_filter;
929                 mm->def_flags = 0;
930         }
931
932         if (mm_alloc_pgd(mm))
933                 goto fail_nopgd;
934
935         if (init_new_context(p, mm))
936                 goto fail_nocontext;
937
938         mm->user_ns = get_user_ns(user_ns);
939         return mm;
940
941 fail_nocontext:
942         mm_free_pgd(mm);
943 fail_nopgd:
944         free_mm(mm);
945         return NULL;
946 }
947
948 /*
949  * Allocate and initialize an mm_struct.
950  */
951 struct mm_struct *mm_alloc(void)
952 {
953         struct mm_struct *mm;
954
955         mm = allocate_mm();
956         if (!mm)
957                 return NULL;
958
959         memset(mm, 0, sizeof(*mm));
960         return mm_init(mm, current, current_user_ns());
961 }
962
963 static inline void __mmput(struct mm_struct *mm)
964 {
965         VM_BUG_ON(atomic_read(&mm->mm_users));
966
967         uprobe_clear_state(mm);
968         exit_aio(mm);
969         ksm_exit(mm);
970         khugepaged_exit(mm); /* must run before exit_mmap */
971         exit_mmap(mm);
972         mm_put_huge_zero_page(mm);
973         set_mm_exe_file(mm, NULL);
974         if (!list_empty(&mm->mmlist)) {
975                 spin_lock(&mmlist_lock);
976                 list_del(&mm->mmlist);
977                 spin_unlock(&mmlist_lock);
978         }
979         if (mm->binfmt)
980                 module_put(mm->binfmt->module);
981         mmdrop(mm);
982 }
983
984 /*
985  * Decrement the use count and release all resources for an mm.
986  */
987 void mmput(struct mm_struct *mm)
988 {
989         might_sleep();
990
991         if (atomic_dec_and_test(&mm->mm_users))
992                 __mmput(mm);
993 }
994 EXPORT_SYMBOL_GPL(mmput);
995
996 #ifdef CONFIG_MMU
997 static void mmput_async_fn(struct work_struct *work)
998 {
999         struct mm_struct *mm = container_of(work, struct mm_struct,
1000                                             async_put_work);
1001
1002         __mmput(mm);
1003 }
1004
1005 void mmput_async(struct mm_struct *mm)
1006 {
1007         if (atomic_dec_and_test(&mm->mm_users)) {
1008                 INIT_WORK(&mm->async_put_work, mmput_async_fn);
1009                 schedule_work(&mm->async_put_work);
1010         }
1011 }
1012 #endif
1013
1014 /**
1015  * set_mm_exe_file - change a reference to the mm's executable file
1016  *
1017  * This changes mm's executable file (shown as symlink /proc/[pid]/exe).
1018  *
1019  * Main users are mmput() and sys_execve(). Callers prevent concurrent
1020  * invocations: in mmput() nobody alive left, in execve task is single
1021  * threaded. sys_prctl(PR_SET_MM_MAP/EXE_FILE) also needs to set the
1022  * mm->exe_file, but does so without using set_mm_exe_file() in order
1023  * to do avoid the need for any locks.
1024  */
1025 void set_mm_exe_file(struct mm_struct *mm, struct file *new_exe_file)
1026 {
1027         struct file *old_exe_file;
1028
1029         /*
1030          * It is safe to dereference the exe_file without RCU as
1031          * this function is only called if nobody else can access
1032          * this mm -- see comment above for justification.
1033          */
1034         old_exe_file = rcu_dereference_raw(mm->exe_file);
1035
1036         if (new_exe_file)
1037                 get_file(new_exe_file);
1038         rcu_assign_pointer(mm->exe_file, new_exe_file);
1039         if (old_exe_file)
1040                 fput(old_exe_file);
1041 }
1042
1043 /**
1044  * get_mm_exe_file - acquire a reference to the mm's executable file
1045  *
1046  * Returns %NULL if mm has no associated executable file.
1047  * User must release file via fput().
1048  */
1049 struct file *get_mm_exe_file(struct mm_struct *mm)
1050 {
1051         struct file *exe_file;
1052
1053         rcu_read_lock();
1054         exe_file = rcu_dereference(mm->exe_file);
1055         if (exe_file && !get_file_rcu(exe_file))
1056                 exe_file = NULL;
1057         rcu_read_unlock();
1058         return exe_file;
1059 }
1060 EXPORT_SYMBOL(get_mm_exe_file);
1061
1062 /**
1063  * get_task_exe_file - acquire a reference to the task's executable file
1064  *
1065  * Returns %NULL if task's mm (if any) has no associated executable file or
1066  * this is a kernel thread with borrowed mm (see the comment above get_task_mm).
1067  * User must release file via fput().
1068  */
1069 struct file *get_task_exe_file(struct task_struct *task)
1070 {
1071         struct file *exe_file = NULL;
1072         struct mm_struct *mm;
1073
1074         task_lock(task);
1075         mm = task->mm;
1076         if (mm) {
1077                 if (!(task->flags & PF_KTHREAD))
1078                         exe_file = get_mm_exe_file(mm);
1079         }
1080         task_unlock(task);
1081         return exe_file;
1082 }
1083 EXPORT_SYMBOL(get_task_exe_file);
1084
1085 /**
1086  * get_task_mm - acquire a reference to the task's mm
1087  *
1088  * Returns %NULL if the task has no mm.  Checks PF_KTHREAD (meaning
1089  * this kernel workthread has transiently adopted a user mm with use_mm,
1090  * to do its AIO) is not set and if so returns a reference to it, after
1091  * bumping up the use count.  User must release the mm via mmput()
1092  * after use.  Typically used by /proc and ptrace.
1093  */
1094 struct mm_struct *get_task_mm(struct task_struct *task)
1095 {
1096         struct mm_struct *mm;
1097
1098         task_lock(task);
1099         mm = task->mm;
1100         if (mm) {
1101                 if (task->flags & PF_KTHREAD)
1102                         mm = NULL;
1103                 else
1104                         mmget(mm);
1105         }
1106         task_unlock(task);
1107         return mm;
1108 }
1109 EXPORT_SYMBOL_GPL(get_task_mm);
1110
1111 struct mm_struct *mm_access(struct task_struct *task, unsigned int mode)
1112 {
1113         struct mm_struct *mm;
1114         int err;
1115
1116         err =  mutex_lock_killable(&task->signal->cred_guard_mutex);
1117         if (err)
1118                 return ERR_PTR(err);
1119
1120         mm = get_task_mm(task);
1121         if (mm && mm != current->mm &&
1122                         !ptrace_may_access(task, mode)) {
1123                 mmput(mm);
1124                 mm = ERR_PTR(-EACCES);
1125         }
1126         mutex_unlock(&task->signal->cred_guard_mutex);
1127
1128         return mm;
1129 }
1130
1131 static void complete_vfork_done(struct task_struct *tsk)
1132 {
1133         struct completion *vfork;
1134
1135         task_lock(tsk);
1136         vfork = tsk->vfork_done;
1137         if (likely(vfork)) {
1138                 tsk->vfork_done = NULL;
1139                 complete(vfork);
1140         }
1141         task_unlock(tsk);
1142 }
1143
1144 static int wait_for_vfork_done(struct task_struct *child,
1145                                 struct completion *vfork)
1146 {
1147         int killed;
1148
1149         freezer_do_not_count();
1150         killed = wait_for_completion_killable(vfork);
1151         freezer_count();
1152
1153         if (killed) {
1154                 task_lock(child);
1155                 child->vfork_done = NULL;
1156                 task_unlock(child);
1157         }
1158
1159         put_task_struct(child);
1160         return killed;
1161 }
1162
1163 /* Please note the differences between mmput and mm_release.
1164  * mmput is called whenever we stop holding onto a mm_struct,
1165  * error success whatever.
1166  *
1167  * mm_release is called after a mm_struct has been removed
1168  * from the current process.
1169  *
1170  * This difference is important for error handling, when we
1171  * only half set up a mm_struct for a new process and need to restore
1172  * the old one.  Because we mmput the new mm_struct before
1173  * restoring the old one. . .
1174  * Eric Biederman 10 January 1998
1175  */
1176 void mm_release(struct task_struct *tsk, struct mm_struct *mm)
1177 {
1178         /* Get rid of any futexes when releasing the mm */
1179 #ifdef CONFIG_FUTEX
1180         if (unlikely(tsk->robust_list)) {
1181                 exit_robust_list(tsk);
1182                 tsk->robust_list = NULL;
1183         }
1184 #ifdef CONFIG_COMPAT
1185         if (unlikely(tsk->compat_robust_list)) {
1186                 compat_exit_robust_list(tsk);
1187                 tsk->compat_robust_list = NULL;
1188         }
1189 #endif
1190         if (unlikely(!list_empty(&tsk->pi_state_list)))
1191                 exit_pi_state_list(tsk);
1192 #endif
1193
1194         uprobe_free_utask(tsk);
1195
1196         /* Get rid of any cached register state */
1197         deactivate_mm(tsk, mm);
1198
1199         /*
1200          * Signal userspace if we're not exiting with a core dump
1201          * because we want to leave the value intact for debugging
1202          * purposes.
1203          */
1204         if (tsk->clear_child_tid) {
1205                 if (!(tsk->signal->flags & SIGNAL_GROUP_COREDUMP) &&
1206                     atomic_read(&mm->mm_users) > 1) {
1207                         /*
1208                          * We don't check the error code - if userspace has
1209                          * not set up a proper pointer then tough luck.
1210                          */
1211                         put_user(0, tsk->clear_child_tid);
1212                         sys_futex(tsk->clear_child_tid, FUTEX_WAKE,
1213                                         1, NULL, NULL, 0);
1214                 }
1215                 tsk->clear_child_tid = NULL;
1216         }
1217
1218         /*
1219          * All done, finally we can wake up parent and return this mm to him.
1220          * Also kthread_stop() uses this completion for synchronization.
1221          */
1222         if (tsk->vfork_done)
1223                 complete_vfork_done(tsk);
1224 }
1225
1226 /*
1227  * Allocate a new mm structure and copy contents from the
1228  * mm structure of the passed in task structure.
1229  */
1230 static struct mm_struct *dup_mm(struct task_struct *tsk)
1231 {
1232         struct mm_struct *mm, *oldmm = current->mm;
1233         int err;
1234
1235         mm = allocate_mm();
1236         if (!mm)
1237                 goto fail_nomem;
1238
1239         memcpy(mm, oldmm, sizeof(*mm));
1240
1241         if (!mm_init(mm, tsk, mm->user_ns))
1242                 goto fail_nomem;
1243
1244         err = dup_mmap(mm, oldmm);
1245         if (err)
1246                 goto free_pt;
1247
1248         mm->hiwater_rss = get_mm_rss(mm);
1249         mm->hiwater_vm = mm->total_vm;
1250
1251         if (mm->binfmt && !try_module_get(mm->binfmt->module))
1252                 goto free_pt;
1253
1254         return mm;
1255
1256 free_pt:
1257         /* don't put binfmt in mmput, we haven't got module yet */
1258         mm->binfmt = NULL;
1259         mmput(mm);
1260
1261 fail_nomem:
1262         return NULL;
1263 }
1264
1265 static int copy_mm(unsigned long clone_flags, struct task_struct *tsk)
1266 {
1267         struct mm_struct *mm, *oldmm;
1268         int retval;
1269
1270         tsk->min_flt = tsk->maj_flt = 0;
1271         tsk->nvcsw = tsk->nivcsw = 0;
1272 #ifdef CONFIG_DETECT_HUNG_TASK
1273         tsk->last_switch_count = tsk->nvcsw + tsk->nivcsw;
1274 #endif
1275
1276         tsk->mm = NULL;
1277         tsk->active_mm = NULL;
1278
1279         /*
1280          * Are we cloning a kernel thread?
1281          *
1282          * We need to steal a active VM for that..
1283          */
1284         oldmm = current->mm;
1285         if (!oldmm)
1286                 return 0;
1287
1288         /* initialize the new vmacache entries */
1289         vmacache_flush(tsk);
1290
1291         if (clone_flags & CLONE_VM) {
1292                 mmget(oldmm);
1293                 mm = oldmm;
1294                 goto good_mm;
1295         }
1296
1297         retval = -ENOMEM;
1298         mm = dup_mm(tsk);
1299         if (!mm)
1300                 goto fail_nomem;
1301
1302 good_mm:
1303         tsk->mm = mm;
1304         tsk->active_mm = mm;
1305         return 0;
1306
1307 fail_nomem:
1308         return retval;
1309 }
1310
1311 static int copy_fs(unsigned long clone_flags, struct task_struct *tsk)
1312 {
1313         struct fs_struct *fs = current->fs;
1314         if (clone_flags & CLONE_FS) {
1315                 /* tsk->fs is already what we want */
1316                 spin_lock(&fs->lock);
1317                 if (fs->in_exec) {
1318                         spin_unlock(&fs->lock);
1319                         return -EAGAIN;
1320                 }
1321                 fs->users++;
1322                 spin_unlock(&fs->lock);
1323                 return 0;
1324         }
1325         tsk->fs = copy_fs_struct(fs);
1326         if (!tsk->fs)
1327                 return -ENOMEM;
1328         return 0;
1329 }
1330
1331 static int copy_files(unsigned long clone_flags, struct task_struct *tsk)
1332 {
1333         struct files_struct *oldf, *newf;
1334         int error = 0;
1335
1336         /*
1337          * A background process may not have any files ...
1338          */
1339         oldf = current->files;
1340         if (!oldf)
1341                 goto out;
1342
1343         if (clone_flags & CLONE_FILES) {
1344                 atomic_inc(&oldf->count);
1345                 goto out;
1346         }
1347
1348         newf = dup_fd(oldf, &error);
1349         if (!newf)
1350                 goto out;
1351
1352         tsk->files = newf;
1353         error = 0;
1354 out:
1355         return error;
1356 }
1357
1358 static int copy_io(unsigned long clone_flags, struct task_struct *tsk)
1359 {
1360 #ifdef CONFIG_BLOCK
1361         struct io_context *ioc = current->io_context;
1362         struct io_context *new_ioc;
1363
1364         if (!ioc)
1365                 return 0;
1366         /*
1367          * Share io context with parent, if CLONE_IO is set
1368          */
1369         if (clone_flags & CLONE_IO) {
1370                 ioc_task_link(ioc);
1371                 tsk->io_context = ioc;
1372         } else if (ioprio_valid(ioc->ioprio)) {
1373                 new_ioc = get_task_io_context(tsk, GFP_KERNEL, NUMA_NO_NODE);
1374                 if (unlikely(!new_ioc))
1375                         return -ENOMEM;
1376
1377                 new_ioc->ioprio = ioc->ioprio;
1378                 put_io_context(new_ioc);
1379         }
1380 #endif
1381         return 0;
1382 }
1383
1384 static int copy_sighand(unsigned long clone_flags, struct task_struct *tsk)
1385 {
1386         struct sighand_struct *sig;
1387
1388         if (clone_flags & CLONE_SIGHAND) {
1389                 atomic_inc(&current->sighand->count);
1390                 return 0;
1391         }
1392         sig = kmem_cache_alloc(sighand_cachep, GFP_KERNEL);
1393         rcu_assign_pointer(tsk->sighand, sig);
1394         if (!sig)
1395                 return -ENOMEM;
1396
1397         atomic_set(&sig->count, 1);
1398         memcpy(sig->action, current->sighand->action, sizeof(sig->action));
1399         return 0;
1400 }
1401
1402 void __cleanup_sighand(struct sighand_struct *sighand)
1403 {
1404         if (atomic_dec_and_test(&sighand->count)) {
1405                 signalfd_cleanup(sighand);
1406                 /*
1407                  * sighand_cachep is SLAB_TYPESAFE_BY_RCU so we can free it
1408                  * without an RCU grace period, see __lock_task_sighand().
1409                  */
1410                 kmem_cache_free(sighand_cachep, sighand);
1411         }
1412 }
1413
1414 #ifdef CONFIG_POSIX_TIMERS
1415 /*
1416  * Initialize POSIX timer handling for a thread group.
1417  */
1418 static void posix_cpu_timers_init_group(struct signal_struct *sig)
1419 {
1420         unsigned long cpu_limit;
1421
1422         cpu_limit = READ_ONCE(sig->rlim[RLIMIT_CPU].rlim_cur);
1423         if (cpu_limit != RLIM_INFINITY) {
1424                 sig->cputime_expires.prof_exp = cpu_limit * NSEC_PER_SEC;
1425                 sig->cputimer.running = true;
1426         }
1427
1428         /* The timer lists. */
1429         INIT_LIST_HEAD(&sig->cpu_timers[0]);
1430         INIT_LIST_HEAD(&sig->cpu_timers[1]);
1431         INIT_LIST_HEAD(&sig->cpu_timers[2]);
1432 }
1433 #else
1434 static inline void posix_cpu_timers_init_group(struct signal_struct *sig) { }
1435 #endif
1436
1437 static int copy_signal(unsigned long clone_flags, struct task_struct *tsk)
1438 {
1439         struct signal_struct *sig;
1440
1441         if (clone_flags & CLONE_THREAD)
1442                 return 0;
1443
1444         sig = kmem_cache_zalloc(signal_cachep, GFP_KERNEL);
1445         tsk->signal = sig;
1446         if (!sig)
1447                 return -ENOMEM;
1448
1449         sig->nr_threads = 1;
1450         atomic_set(&sig->live, 1);
1451         atomic_set(&sig->sigcnt, 1);
1452
1453         /* list_add(thread_node, thread_head) without INIT_LIST_HEAD() */
1454         sig->thread_head = (struct list_head)LIST_HEAD_INIT(tsk->thread_node);
1455         tsk->thread_node = (struct list_head)LIST_HEAD_INIT(sig->thread_head);
1456
1457         init_waitqueue_head(&sig->wait_chldexit);
1458         sig->curr_target = tsk;
1459         init_sigpending(&sig->shared_pending);
1460         seqlock_init(&sig->stats_lock);
1461         prev_cputime_init(&sig->prev_cputime);
1462
1463 #ifdef CONFIG_POSIX_TIMERS
1464         INIT_LIST_HEAD(&sig->posix_timers);
1465         hrtimer_init(&sig->real_timer, CLOCK_MONOTONIC, HRTIMER_MODE_REL);
1466         sig->real_timer.function = it_real_fn;
1467 #endif
1468
1469         task_lock(current->group_leader);
1470         memcpy(sig->rlim, current->signal->rlim, sizeof sig->rlim);
1471         task_unlock(current->group_leader);
1472
1473         posix_cpu_timers_init_group(sig);
1474
1475         tty_audit_fork(sig);
1476         sched_autogroup_fork(sig);
1477
1478         sig->oom_score_adj = current->signal->oom_score_adj;
1479         sig->oom_score_adj_min = current->signal->oom_score_adj_min;
1480
1481         mutex_init(&sig->cred_guard_mutex);
1482
1483         return 0;
1484 }
1485
1486 static void copy_seccomp(struct task_struct *p)
1487 {
1488 #ifdef CONFIG_SECCOMP
1489         /*
1490          * Must be called with sighand->lock held, which is common to
1491          * all threads in the group. Holding cred_guard_mutex is not
1492          * needed because this new task is not yet running and cannot
1493          * be racing exec.
1494          */
1495         assert_spin_locked(&current->sighand->siglock);
1496
1497         /* Ref-count the new filter user, and assign it. */
1498         get_seccomp_filter(current);
1499         p->seccomp = current->seccomp;
1500
1501         /*
1502          * Explicitly enable no_new_privs here in case it got set
1503          * between the task_struct being duplicated and holding the
1504          * sighand lock. The seccomp state and nnp must be in sync.
1505          */
1506         if (task_no_new_privs(current))
1507                 task_set_no_new_privs(p);
1508
1509         /*
1510          * If the parent gained a seccomp mode after copying thread
1511          * flags and between before we held the sighand lock, we have
1512          * to manually enable the seccomp thread flag here.
1513          */
1514         if (p->seccomp.mode != SECCOMP_MODE_DISABLED)
1515                 set_tsk_thread_flag(p, TIF_SECCOMP);
1516 #endif
1517 }
1518
1519 SYSCALL_DEFINE1(set_tid_address, int __user *, tidptr)
1520 {
1521         current->clear_child_tid = tidptr;
1522
1523         return task_pid_vnr(current);
1524 }
1525
1526 static void rt_mutex_init_task(struct task_struct *p)
1527 {
1528         raw_spin_lock_init(&p->pi_lock);
1529 #ifdef CONFIG_RT_MUTEXES
1530         p->pi_waiters = RB_ROOT_CACHED;
1531         p->pi_top_task = NULL;
1532         p->pi_blocked_on = NULL;
1533 #endif
1534 }
1535
1536 #ifdef CONFIG_POSIX_TIMERS
1537 /*
1538  * Initialize POSIX timer handling for a single task.
1539  */
1540 static void posix_cpu_timers_init(struct task_struct *tsk)
1541 {
1542         tsk->cputime_expires.prof_exp = 0;
1543         tsk->cputime_expires.virt_exp = 0;
1544         tsk->cputime_expires.sched_exp = 0;
1545         INIT_LIST_HEAD(&tsk->cpu_timers[0]);
1546         INIT_LIST_HEAD(&tsk->cpu_timers[1]);
1547         INIT_LIST_HEAD(&tsk->cpu_timers[2]);
1548 }
1549 #else
1550 static inline void posix_cpu_timers_init(struct task_struct *tsk) { }
1551 #endif
1552
1553 static inline void
1554 init_task_pid(struct task_struct *task, enum pid_type type, struct pid *pid)
1555 {
1556          task->pids[type].pid = pid;
1557 }
1558
1559 static inline void rcu_copy_process(struct task_struct *p)
1560 {
1561 #ifdef CONFIG_PREEMPT_RCU
1562         p->rcu_read_lock_nesting = 0;
1563         p->rcu_read_unlock_special.s = 0;
1564         p->rcu_blocked_node = NULL;
1565         INIT_LIST_HEAD(&p->rcu_node_entry);
1566 #endif /* #ifdef CONFIG_PREEMPT_RCU */
1567 #ifdef CONFIG_TASKS_RCU
1568         p->rcu_tasks_holdout = false;
1569         INIT_LIST_HEAD(&p->rcu_tasks_holdout_list);
1570         p->rcu_tasks_idle_cpu = -1;
1571 #endif /* #ifdef CONFIG_TASKS_RCU */
1572 }
1573
1574 /*
1575  * This creates a new process as a copy of the old one,
1576  * but does not actually start it yet.
1577  *
1578  * It copies the registers, and all the appropriate
1579  * parts of the process environment (as per the clone
1580  * flags). The actual kick-off is left to the caller.
1581  */
1582 static __latent_entropy struct task_struct *copy_process(
1583                                         unsigned long clone_flags,
1584                                         unsigned long stack_start,
1585                                         unsigned long stack_size,
1586                                         int __user *child_tidptr,
1587                                         struct pid *pid,
1588                                         int trace,
1589                                         unsigned long tls,
1590                                         int node)
1591 {
1592         int retval;
1593         struct task_struct *p;
1594
1595         if ((clone_flags & (CLONE_NEWNS|CLONE_FS)) == (CLONE_NEWNS|CLONE_FS))
1596                 return ERR_PTR(-EINVAL);
1597
1598         if ((clone_flags & (CLONE_NEWUSER|CLONE_FS)) == (CLONE_NEWUSER|CLONE_FS))
1599                 return ERR_PTR(-EINVAL);
1600
1601         /*
1602          * Thread groups must share signals as well, and detached threads
1603          * can only be started up within the thread group.
1604          */
1605         if ((clone_flags & CLONE_THREAD) && !(clone_flags & CLONE_SIGHAND))
1606                 return ERR_PTR(-EINVAL);
1607
1608         /*
1609          * Shared signal handlers imply shared VM. By way of the above,
1610          * thread groups also imply shared VM. Blocking this case allows
1611          * for various simplifications in other code.
1612          */
1613         if ((clone_flags & CLONE_SIGHAND) && !(clone_flags & CLONE_VM))
1614                 return ERR_PTR(-EINVAL);
1615
1616         /*
1617          * Siblings of global init remain as zombies on exit since they are
1618          * not reaped by their parent (swapper). To solve this and to avoid
1619          * multi-rooted process trees, prevent global and container-inits
1620          * from creating siblings.
1621          */
1622         if ((clone_flags & CLONE_PARENT) &&
1623                                 current->signal->flags & SIGNAL_UNKILLABLE)
1624                 return ERR_PTR(-EINVAL);
1625
1626         /*
1627          * If the new process will be in a different pid or user namespace
1628          * do not allow it to share a thread group with the forking task.
1629          */
1630         if (clone_flags & CLONE_THREAD) {
1631                 if ((clone_flags & (CLONE_NEWUSER | CLONE_NEWPID)) ||
1632                     (task_active_pid_ns(current) !=
1633                                 current->nsproxy->pid_ns_for_children))
1634                         return ERR_PTR(-EINVAL);
1635         }
1636
1637         retval = -ENOMEM;
1638         p = dup_task_struct(current, node);
1639         if (!p)
1640                 goto fork_out;
1641
1642         /*
1643          * This _must_ happen before we call free_task(), i.e. before we jump
1644          * to any of the bad_fork_* labels. This is to avoid freeing
1645          * p->set_child_tid which is (ab)used as a kthread's data pointer for
1646          * kernel threads (PF_KTHREAD).
1647          */
1648         p->set_child_tid = (clone_flags & CLONE_CHILD_SETTID) ? child_tidptr : NULL;
1649         /*
1650          * Clear TID on mm_release()?
1651          */
1652         p->clear_child_tid = (clone_flags & CLONE_CHILD_CLEARTID) ? child_tidptr : NULL;
1653
1654         ftrace_graph_init_task(p);
1655
1656         rt_mutex_init_task(p);
1657
1658 #ifdef CONFIG_PROVE_LOCKING
1659         DEBUG_LOCKS_WARN_ON(!p->hardirqs_enabled);
1660         DEBUG_LOCKS_WARN_ON(!p->softirqs_enabled);
1661 #endif
1662         retval = -EAGAIN;
1663         if (atomic_read(&p->real_cred->user->processes) >=
1664                         task_rlimit(p, RLIMIT_NPROC)) {
1665                 if (p->real_cred->user != INIT_USER &&
1666                     !capable(CAP_SYS_RESOURCE) && !capable(CAP_SYS_ADMIN))
1667                         goto bad_fork_free;
1668         }
1669         current->flags &= ~PF_NPROC_EXCEEDED;
1670
1671         retval = copy_creds(p, clone_flags);
1672         if (retval < 0)
1673                 goto bad_fork_free;
1674
1675         /*
1676          * If multiple threads are within copy_process(), then this check
1677          * triggers too late. This doesn't hurt, the check is only there
1678          * to stop root fork bombs.
1679          */
1680         retval = -EAGAIN;
1681         if (nr_threads >= max_threads)
1682                 goto bad_fork_cleanup_count;
1683
1684         delayacct_tsk_init(p);  /* Must remain after dup_task_struct() */
1685         p->flags &= ~(PF_SUPERPRIV | PF_WQ_WORKER | PF_IDLE);
1686         p->flags |= PF_FORKNOEXEC;
1687         INIT_LIST_HEAD(&p->children);
1688         INIT_LIST_HEAD(&p->sibling);
1689         rcu_copy_process(p);
1690         p->vfork_done = NULL;
1691         spin_lock_init(&p->alloc_lock);
1692
1693         init_sigpending(&p->pending);
1694
1695         p->utime = p->stime = p->gtime = 0;
1696 #ifdef CONFIG_ARCH_HAS_SCALED_CPUTIME
1697         p->utimescaled = p->stimescaled = 0;
1698 #endif
1699         prev_cputime_init(&p->prev_cputime);
1700
1701 #ifdef CONFIG_VIRT_CPU_ACCOUNTING_GEN
1702         seqcount_init(&p->vtime.seqcount);
1703         p->vtime.starttime = 0;
1704         p->vtime.state = VTIME_INACTIVE;
1705 #endif
1706
1707 #if defined(SPLIT_RSS_COUNTING)
1708         memset(&p->rss_stat, 0, sizeof(p->rss_stat));
1709 #endif
1710
1711         p->default_timer_slack_ns = current->timer_slack_ns;
1712
1713         task_io_accounting_init(&p->ioac);
1714         acct_clear_integrals(p);
1715
1716         posix_cpu_timers_init(p);
1717
1718         p->start_time = ktime_get_ns();
1719         p->real_start_time = ktime_get_boot_ns();
1720         p->io_context = NULL;
1721         p->audit_context = NULL;
1722         cgroup_fork(p);
1723 #ifdef CONFIG_NUMA
1724         p->mempolicy = mpol_dup(p->mempolicy);
1725         if (IS_ERR(p->mempolicy)) {
1726                 retval = PTR_ERR(p->mempolicy);
1727                 p->mempolicy = NULL;
1728                 goto bad_fork_cleanup_threadgroup_lock;
1729         }
1730 #endif
1731 #ifdef CONFIG_CPUSETS
1732         p->cpuset_mem_spread_rotor = NUMA_NO_NODE;
1733         p->cpuset_slab_spread_rotor = NUMA_NO_NODE;
1734         seqcount_init(&p->mems_allowed_seq);
1735 #endif
1736 #ifdef CONFIG_TRACE_IRQFLAGS
1737         p->irq_events = 0;
1738         p->hardirqs_enabled = 0;
1739         p->hardirq_enable_ip = 0;
1740         p->hardirq_enable_event = 0;
1741         p->hardirq_disable_ip = _THIS_IP_;
1742         p->hardirq_disable_event = 0;
1743         p->softirqs_enabled = 1;
1744         p->softirq_enable_ip = _THIS_IP_;
1745         p->softirq_enable_event = 0;
1746         p->softirq_disable_ip = 0;
1747         p->softirq_disable_event = 0;
1748         p->hardirq_context = 0;
1749         p->softirq_context = 0;
1750 #endif
1751
1752         p->pagefault_disabled = 0;
1753
1754 #ifdef CONFIG_LOCKDEP
1755         p->lockdep_depth = 0; /* no locks held yet */
1756         p->curr_chain_key = 0;
1757         p->lockdep_recursion = 0;
1758         lockdep_init_task(p);
1759 #endif
1760
1761 #ifdef CONFIG_DEBUG_MUTEXES
1762         p->blocked_on = NULL; /* not blocked yet */
1763 #endif
1764 #ifdef CONFIG_BCACHE
1765         p->sequential_io        = 0;
1766         p->sequential_io_avg    = 0;
1767 #endif
1768
1769         /* Perform scheduler related setup. Assign this task to a CPU. */
1770         retval = sched_fork(clone_flags, p);
1771         if (retval)
1772                 goto bad_fork_cleanup_policy;
1773
1774         retval = perf_event_init_task(p);
1775         if (retval)
1776                 goto bad_fork_cleanup_policy;
1777         retval = audit_alloc(p);
1778         if (retval)
1779                 goto bad_fork_cleanup_perf;
1780         /* copy all the process information */
1781         shm_init_task(p);
1782         retval = security_task_alloc(p, clone_flags);
1783         if (retval)
1784                 goto bad_fork_cleanup_audit;
1785         retval = copy_semundo(clone_flags, p);
1786         if (retval)
1787                 goto bad_fork_cleanup_security;
1788         retval = copy_files(clone_flags, p);
1789         if (retval)
1790                 goto bad_fork_cleanup_semundo;
1791         retval = copy_fs(clone_flags, p);
1792         if (retval)
1793                 goto bad_fork_cleanup_files;
1794         retval = copy_sighand(clone_flags, p);
1795         if (retval)
1796                 goto bad_fork_cleanup_fs;
1797         retval = copy_signal(clone_flags, p);
1798         if (retval)
1799                 goto bad_fork_cleanup_sighand;
1800         retval = copy_mm(clone_flags, p);
1801         if (retval)
1802                 goto bad_fork_cleanup_signal;
1803         retval = copy_namespaces(clone_flags, p);
1804         if (retval)
1805                 goto bad_fork_cleanup_mm;
1806         retval = copy_io(clone_flags, p);
1807         if (retval)
1808                 goto bad_fork_cleanup_namespaces;
1809         retval = copy_thread_tls(clone_flags, stack_start, stack_size, p, tls);
1810         if (retval)
1811                 goto bad_fork_cleanup_io;
1812
1813         if (pid != &init_struct_pid) {
1814                 pid = alloc_pid(p->nsproxy->pid_ns_for_children);
1815                 if (IS_ERR(pid)) {
1816                         retval = PTR_ERR(pid);
1817                         goto bad_fork_cleanup_thread;
1818                 }
1819         }
1820
1821 #ifdef CONFIG_BLOCK
1822         p->plug = NULL;
1823 #endif
1824 #ifdef CONFIG_FUTEX
1825         p->robust_list = NULL;
1826 #ifdef CONFIG_COMPAT
1827         p->compat_robust_list = NULL;
1828 #endif
1829         INIT_LIST_HEAD(&p->pi_state_list);
1830         p->pi_state_cache = NULL;
1831 #endif
1832         /*
1833          * sigaltstack should be cleared when sharing the same VM
1834          */
1835         if ((clone_flags & (CLONE_VM|CLONE_VFORK)) == CLONE_VM)
1836                 sas_ss_reset(p);
1837
1838         /*
1839          * Syscall tracing and stepping should be turned off in the
1840          * child regardless of CLONE_PTRACE.
1841          */
1842         user_disable_single_step(p);
1843         clear_tsk_thread_flag(p, TIF_SYSCALL_TRACE);
1844 #ifdef TIF_SYSCALL_EMU
1845         clear_tsk_thread_flag(p, TIF_SYSCALL_EMU);
1846 #endif
1847         clear_all_latency_tracing(p);
1848
1849         /* ok, now we should be set up.. */
1850         p->pid = pid_nr(pid);
1851         if (clone_flags & CLONE_THREAD) {
1852                 p->exit_signal = -1;
1853                 p->group_leader = current->group_leader;
1854                 p->tgid = current->tgid;
1855         } else {
1856                 if (clone_flags & CLONE_PARENT)
1857                         p->exit_signal = current->group_leader->exit_signal;
1858                 else
1859                         p->exit_signal = (clone_flags & CSIGNAL);
1860                 p->group_leader = p;
1861                 p->tgid = p->pid;
1862         }
1863
1864         p->nr_dirtied = 0;
1865         p->nr_dirtied_pause = 128 >> (PAGE_SHIFT - 10);
1866         p->dirty_paused_when = 0;
1867
1868         p->pdeath_signal = 0;
1869         INIT_LIST_HEAD(&p->thread_group);
1870         p->task_works = NULL;
1871
1872         cgroup_threadgroup_change_begin(current);
1873         /*
1874          * Ensure that the cgroup subsystem policies allow the new process to be
1875          * forked. It should be noted the the new process's css_set can be changed
1876          * between here and cgroup_post_fork() if an organisation operation is in
1877          * progress.
1878          */
1879         retval = cgroup_can_fork(p);
1880         if (retval)
1881                 goto bad_fork_free_pid;
1882
1883         /*
1884          * Make it visible to the rest of the system, but dont wake it up yet.
1885          * Need tasklist lock for parent etc handling!
1886          */
1887         write_lock_irq(&tasklist_lock);
1888
1889         /* CLONE_PARENT re-uses the old parent */
1890         if (clone_flags & (CLONE_PARENT|CLONE_THREAD)) {
1891                 p->real_parent = current->real_parent;
1892                 p->parent_exec_id = current->parent_exec_id;
1893         } else {
1894                 p->real_parent = current;
1895                 p->parent_exec_id = current->self_exec_id;
1896         }
1897
1898         klp_copy_process(p);
1899
1900         spin_lock(&current->sighand->siglock);
1901
1902         /*
1903          * Copy seccomp details explicitly here, in case they were changed
1904          * before holding sighand lock.
1905          */
1906         copy_seccomp(p);
1907
1908         /*
1909          * Process group and session signals need to be delivered to just the
1910          * parent before the fork or both the parent and the child after the
1911          * fork. Restart if a signal comes in before we add the new process to
1912          * it's process group.
1913          * A fatal signal pending means that current will exit, so the new
1914          * thread can't slip out of an OOM kill (or normal SIGKILL).
1915         */
1916         recalc_sigpending();
1917         if (signal_pending(current)) {
1918                 retval = -ERESTARTNOINTR;
1919                 goto bad_fork_cancel_cgroup;
1920         }
1921         if (unlikely(!(ns_of_pid(pid)->pid_allocated & PIDNS_ADDING))) {
1922                 retval = -ENOMEM;
1923                 goto bad_fork_cancel_cgroup;
1924         }
1925
1926         if (likely(p->pid)) {
1927                 ptrace_init_task(p, (clone_flags & CLONE_PTRACE) || trace);
1928
1929                 init_task_pid(p, PIDTYPE_PID, pid);
1930                 if (thread_group_leader(p)) {
1931                         init_task_pid(p, PIDTYPE_PGID, task_pgrp(current));
1932                         init_task_pid(p, PIDTYPE_SID, task_session(current));
1933
1934                         if (is_child_reaper(pid)) {
1935                                 ns_of_pid(pid)->child_reaper = p;
1936                                 p->signal->flags |= SIGNAL_UNKILLABLE;
1937                         }
1938
1939                         p->signal->leader_pid = pid;
1940                         p->signal->tty = tty_kref_get(current->signal->tty);
1941                         /*
1942                          * Inherit has_child_subreaper flag under the same
1943                          * tasklist_lock with adding child to the process tree
1944                          * for propagate_has_child_subreaper optimization.
1945                          */
1946                         p->signal->has_child_subreaper = p->real_parent->signal->has_child_subreaper ||
1947                                                          p->real_parent->signal->is_child_subreaper;
1948                         list_add_tail(&p->sibling, &p->real_parent->children);
1949                         list_add_tail_rcu(&p->tasks, &init_task.tasks);
1950                         attach_pid(p, PIDTYPE_PGID);
1951                         attach_pid(p, PIDTYPE_SID);
1952                         __this_cpu_inc(process_counts);
1953                 } else {
1954                         current->signal->nr_threads++;
1955                         atomic_inc(&current->signal->live);
1956                         atomic_inc(&current->signal->sigcnt);
1957                         list_add_tail_rcu(&p->thread_group,
1958                                           &p->group_leader->thread_group);
1959                         list_add_tail_rcu(&p->thread_node,
1960                                           &p->signal->thread_head);
1961                 }
1962                 attach_pid(p, PIDTYPE_PID);
1963                 nr_threads++;
1964         }
1965
1966         total_forks++;
1967         spin_unlock(&current->sighand->siglock);
1968         syscall_tracepoint_update(p);
1969         write_unlock_irq(&tasklist_lock);
1970
1971         proc_fork_connector(p);
1972         cgroup_post_fork(p);
1973         cgroup_threadgroup_change_end(current);
1974         perf_event_fork(p);
1975
1976         trace_task_newtask(p, clone_flags);
1977         uprobe_copy_process(p, clone_flags);
1978
1979         return p;
1980
1981 bad_fork_cancel_cgroup:
1982         spin_unlock(&current->sighand->siglock);
1983         write_unlock_irq(&tasklist_lock);
1984         cgroup_cancel_fork(p);
1985 bad_fork_free_pid:
1986         cgroup_threadgroup_change_end(current);
1987         if (pid != &init_struct_pid)
1988                 free_pid(pid);
1989 bad_fork_cleanup_thread:
1990         exit_thread(p);
1991 bad_fork_cleanup_io:
1992         if (p->io_context)
1993                 exit_io_context(p);
1994 bad_fork_cleanup_namespaces:
1995         exit_task_namespaces(p);
1996 bad_fork_cleanup_mm:
1997         if (p->mm)
1998                 mmput(p->mm);
1999 bad_fork_cleanup_signal:
2000         if (!(clone_flags & CLONE_THREAD))
2001                 free_signal_struct(p->signal);
2002 bad_fork_cleanup_sighand:
2003         __cleanup_sighand(p->sighand);
2004 bad_fork_cleanup_fs:
2005         exit_fs(p); /* blocking */
2006 bad_fork_cleanup_files:
2007         exit_files(p); /* blocking */
2008 bad_fork_cleanup_semundo:
2009         exit_sem(p);
2010 bad_fork_cleanup_security:
2011         security_task_free(p);
2012 bad_fork_cleanup_audit:
2013         audit_free(p);
2014 bad_fork_cleanup_perf:
2015         perf_event_free_task(p);
2016 bad_fork_cleanup_policy:
2017         lockdep_free_task(p);
2018 #ifdef CONFIG_NUMA
2019         mpol_put(p->mempolicy);
2020 bad_fork_cleanup_threadgroup_lock:
2021 #endif
2022         delayacct_tsk_free(p);
2023 bad_fork_cleanup_count:
2024         atomic_dec(&p->cred->user->processes);
2025         exit_creds(p);
2026 bad_fork_free:
2027         p->state = TASK_DEAD;
2028         put_task_stack(p);
2029         free_task(p);
2030 fork_out:
2031         return ERR_PTR(retval);
2032 }
2033
2034 static inline void init_idle_pids(struct pid_link *links)
2035 {
2036         enum pid_type type;
2037
2038         for (type = PIDTYPE_PID; type < PIDTYPE_MAX; ++type) {
2039                 INIT_HLIST_NODE(&links[type].node); /* not really needed */
2040                 links[type].pid = &init_struct_pid;
2041         }
2042 }
2043
2044 struct task_struct *fork_idle(int cpu)
2045 {
2046         struct task_struct *task;
2047         task = copy_process(CLONE_VM, 0, 0, NULL, &init_struct_pid, 0, 0,
2048                             cpu_to_node(cpu));
2049         if (!IS_ERR(task)) {
2050                 init_idle_pids(task->pids);
2051                 init_idle(task, cpu);
2052         }
2053
2054         return task;
2055 }
2056
2057 /*
2058  *  Ok, this is the main fork-routine.
2059  *
2060  * It copies the process, and if successful kick-starts
2061  * it and waits for it to finish using the VM if required.
2062  */
2063 long _do_fork(unsigned long clone_flags,
2064               unsigned long stack_start,
2065               unsigned long stack_size,
2066               int __user *parent_tidptr,
2067               int __user *child_tidptr,
2068               unsigned long tls)
2069 {
2070         struct task_struct *p;
2071         int trace = 0;
2072         long nr;
2073
2074         /*
2075          * Determine whether and which event to report to ptracer.  When
2076          * called from kernel_thread or CLONE_UNTRACED is explicitly
2077          * requested, no event is reported; otherwise, report if the event
2078          * for the type of forking is enabled.
2079          */
2080         if (!(clone_flags & CLONE_UNTRACED)) {
2081                 if (clone_flags & CLONE_VFORK)
2082                         trace = PTRACE_EVENT_VFORK;
2083                 else if ((clone_flags & CSIGNAL) != SIGCHLD)
2084                         trace = PTRACE_EVENT_CLONE;
2085                 else
2086                         trace = PTRACE_EVENT_FORK;
2087
2088                 if (likely(!ptrace_event_enabled(current, trace)))
2089                         trace = 0;
2090         }
2091
2092         p = copy_process(clone_flags, stack_start, stack_size,
2093                          child_tidptr, NULL, trace, tls, NUMA_NO_NODE);
2094         add_latent_entropy();
2095         /*
2096          * Do this prior waking up the new thread - the thread pointer
2097          * might get invalid after that point, if the thread exits quickly.
2098          */
2099         if (!IS_ERR(p)) {
2100                 struct completion vfork;
2101                 struct pid *pid;
2102
2103                 trace_sched_process_fork(current, p);
2104
2105                 pid = get_task_pid(p, PIDTYPE_PID);
2106                 nr = pid_vnr(pid);
2107
2108                 if (clone_flags & CLONE_PARENT_SETTID)
2109                         put_user(nr, parent_tidptr);
2110
2111                 if (clone_flags & CLONE_VFORK) {
2112                         p->vfork_done = &vfork;
2113                         init_completion(&vfork);
2114                         get_task_struct(p);
2115                 }
2116
2117                 wake_up_new_task(p);
2118
2119                 /* forking complete and child started to run, tell ptracer */
2120                 if (unlikely(trace))
2121                         ptrace_event_pid(trace, pid);
2122
2123                 if (clone_flags & CLONE_VFORK) {
2124                         if (!wait_for_vfork_done(p, &vfork))
2125                                 ptrace_event_pid(PTRACE_EVENT_VFORK_DONE, pid);
2126                 }
2127
2128                 put_pid(pid);
2129         } else {
2130                 nr = PTR_ERR(p);
2131         }
2132         return nr;
2133 }
2134
2135 #ifndef CONFIG_HAVE_COPY_THREAD_TLS
2136 /* For compatibility with architectures that call do_fork directly rather than
2137  * using the syscall entry points below. */
2138 long do_fork(unsigned long clone_flags,
2139               unsigned long stack_start,
2140               unsigned long stack_size,
2141               int __user *parent_tidptr,
2142               int __user *child_tidptr)
2143 {
2144         return _do_fork(clone_flags, stack_start, stack_size,
2145                         parent_tidptr, child_tidptr, 0);
2146 }
2147 #endif
2148
2149 /*
2150  * Create a kernel thread.
2151  */
2152 pid_t kernel_thread(int (*fn)(void *), void *arg, unsigned long flags)
2153 {
2154         return _do_fork(flags|CLONE_VM|CLONE_UNTRACED, (unsigned long)fn,
2155                 (unsigned long)arg, NULL, NULL, 0);
2156 }
2157
2158 #ifdef __ARCH_WANT_SYS_FORK
2159 SYSCALL_DEFINE0(fork)
2160 {
2161 #ifdef CONFIG_MMU
2162         return _do_fork(SIGCHLD, 0, 0, NULL, NULL, 0);
2163 #else
2164         /* can not support in nommu mode */
2165         return -EINVAL;
2166 #endif
2167 }
2168 #endif
2169
2170 #ifdef __ARCH_WANT_SYS_VFORK
2171 SYSCALL_DEFINE0(vfork)
2172 {
2173         return _do_fork(CLONE_VFORK | CLONE_VM | SIGCHLD, 0,
2174                         0, NULL, NULL, 0);
2175 }
2176 #endif
2177
2178 #ifdef __ARCH_WANT_SYS_CLONE
2179 #ifdef CONFIG_CLONE_BACKWARDS
2180 SYSCALL_DEFINE5(clone, unsigned long, clone_flags, unsigned long, newsp,
2181                  int __user *, parent_tidptr,
2182                  unsigned long, tls,
2183                  int __user *, child_tidptr)
2184 #elif defined(CONFIG_CLONE_BACKWARDS2)
2185 SYSCALL_DEFINE5(clone, unsigned long, newsp, unsigned long, clone_flags,
2186                  int __user *, parent_tidptr,
2187                  int __user *, child_tidptr,
2188                  unsigned long, tls)
2189 #elif defined(CONFIG_CLONE_BACKWARDS3)
2190 SYSCALL_DEFINE6(clone, unsigned long, clone_flags, unsigned long, newsp,
2191                 int, stack_size,
2192                 int __user *, parent_tidptr,
2193                 int __user *, child_tidptr,
2194                 unsigned long, tls)
2195 #else
2196 SYSCALL_DEFINE5(clone, unsigned long, clone_flags, unsigned long, newsp,
2197                  int __user *, parent_tidptr,
2198                  int __user *, child_tidptr,
2199                  unsigned long, tls)
2200 #endif
2201 {
2202         return _do_fork(clone_flags, newsp, 0, parent_tidptr, child_tidptr, tls);
2203 }
2204 #endif
2205
2206 void walk_process_tree(struct task_struct *top, proc_visitor visitor, void *data)
2207 {
2208         struct task_struct *leader, *parent, *child;
2209         int res;
2210
2211         read_lock(&tasklist_lock);
2212         leader = top = top->group_leader;
2213 down:
2214         for_each_thread(leader, parent) {
2215                 list_for_each_entry(child, &parent->children, sibling) {
2216                         res = visitor(child, data);
2217                         if (res) {
2218                                 if (res < 0)
2219                                         goto out;
2220                                 leader = child;
2221                                 goto down;
2222                         }
2223 up:
2224                         ;
2225                 }
2226         }
2227
2228         if (leader != top) {
2229                 child = leader;
2230                 parent = child->real_parent;
2231                 leader = parent->group_leader;
2232                 goto up;
2233         }
2234 out:
2235         read_unlock(&tasklist_lock);
2236 }
2237
2238 #ifndef ARCH_MIN_MMSTRUCT_ALIGN
2239 #define ARCH_MIN_MMSTRUCT_ALIGN 0
2240 #endif
2241
2242 static void sighand_ctor(void *data)
2243 {
2244         struct sighand_struct *sighand = data;
2245
2246         spin_lock_init(&sighand->siglock);
2247         init_waitqueue_head(&sighand->signalfd_wqh);
2248 }
2249
2250 void __init proc_caches_init(void)
2251 {
2252         sighand_cachep = kmem_cache_create("sighand_cache",
2253                         sizeof(struct sighand_struct), 0,
2254                         SLAB_HWCACHE_ALIGN|SLAB_PANIC|SLAB_TYPESAFE_BY_RCU|
2255                         SLAB_ACCOUNT, sighand_ctor);
2256         signal_cachep = kmem_cache_create("signal_cache",
2257                         sizeof(struct signal_struct), 0,
2258                         SLAB_HWCACHE_ALIGN|SLAB_PANIC|SLAB_ACCOUNT,
2259                         NULL);
2260         files_cachep = kmem_cache_create("files_cache",
2261                         sizeof(struct files_struct), 0,
2262                         SLAB_HWCACHE_ALIGN|SLAB_PANIC|SLAB_ACCOUNT,
2263                         NULL);
2264         fs_cachep = kmem_cache_create("fs_cache",
2265                         sizeof(struct fs_struct), 0,
2266                         SLAB_HWCACHE_ALIGN|SLAB_PANIC|SLAB_ACCOUNT,
2267                         NULL);
2268         /*
2269          * FIXME! The "sizeof(struct mm_struct)" currently includes the
2270          * whole struct cpumask for the OFFSTACK case. We could change
2271          * this to *only* allocate as much of it as required by the
2272          * maximum number of CPU's we can ever have.  The cpumask_allocation
2273          * is at the end of the structure, exactly for that reason.
2274          */
2275         mm_cachep = kmem_cache_create_usercopy("mm_struct",
2276                         sizeof(struct mm_struct), ARCH_MIN_MMSTRUCT_ALIGN,
2277                         SLAB_HWCACHE_ALIGN|SLAB_PANIC|SLAB_ACCOUNT,
2278                         offsetof(struct mm_struct, saved_auxv),
2279                         sizeof_field(struct mm_struct, saved_auxv),
2280                         NULL);
2281         vm_area_cachep = KMEM_CACHE(vm_area_struct, SLAB_PANIC|SLAB_ACCOUNT);
2282         mmap_init();
2283         nsproxy_cache_init();
2284 }
2285
2286 /*
2287  * Check constraints on flags passed to the unshare system call.
2288  */
2289 static int check_unshare_flags(unsigned long unshare_flags)
2290 {
2291         if (unshare_flags & ~(CLONE_THREAD|CLONE_FS|CLONE_NEWNS|CLONE_SIGHAND|
2292                                 CLONE_VM|CLONE_FILES|CLONE_SYSVSEM|
2293                                 CLONE_NEWUTS|CLONE_NEWIPC|CLONE_NEWNET|
2294                                 CLONE_NEWUSER|CLONE_NEWPID|CLONE_NEWCGROUP))
2295                 return -EINVAL;
2296         /*
2297          * Not implemented, but pretend it works if there is nothing
2298          * to unshare.  Note that unsharing the address space or the
2299          * signal handlers also need to unshare the signal queues (aka
2300          * CLONE_THREAD).
2301          */
2302         if (unshare_flags & (CLONE_THREAD | CLONE_SIGHAND | CLONE_VM)) {
2303                 if (!thread_group_empty(current))
2304                         return -EINVAL;
2305         }
2306         if (unshare_flags & (CLONE_SIGHAND | CLONE_VM)) {
2307                 if (atomic_read(&current->sighand->count) > 1)
2308                         return -EINVAL;
2309         }
2310         if (unshare_flags & CLONE_VM) {
2311                 if (!current_is_single_threaded())
2312                         return -EINVAL;
2313         }
2314
2315         return 0;
2316 }
2317
2318 /*
2319  * Unshare the filesystem structure if it is being shared
2320  */
2321 static int unshare_fs(unsigned long unshare_flags, struct fs_struct **new_fsp)
2322 {
2323         struct fs_struct *fs = current->fs;
2324
2325         if (!(unshare_flags & CLONE_FS) || !fs)
2326                 return 0;
2327
2328         /* don't need lock here; in the worst case we'll do useless copy */
2329         if (fs->users == 1)
2330                 return 0;
2331
2332         *new_fsp = copy_fs_struct(fs);
2333         if (!*new_fsp)
2334                 return -ENOMEM;
2335
2336         return 0;
2337 }
2338
2339 /*
2340  * Unshare file descriptor table if it is being shared
2341  */
2342 static int unshare_fd(unsigned long unshare_flags, struct files_struct **new_fdp)
2343 {
2344         struct files_struct *fd = current->files;
2345         int error = 0;
2346
2347         if ((unshare_flags & CLONE_FILES) &&
2348             (fd && atomic_read(&fd->count) > 1)) {
2349                 *new_fdp = dup_fd(fd, &error);
2350                 if (!*new_fdp)
2351                         return error;
2352         }
2353
2354         return 0;
2355 }
2356
2357 /*
2358  * unshare allows a process to 'unshare' part of the process
2359  * context which was originally shared using clone.  copy_*
2360  * functions used by do_fork() cannot be used here directly
2361  * because they modify an inactive task_struct that is being
2362  * constructed. Here we are modifying the current, active,
2363  * task_struct.
2364  */
2365 SYSCALL_DEFINE1(unshare, unsigned long, unshare_flags)
2366 {
2367         struct fs_struct *fs, *new_fs = NULL;
2368         struct files_struct *fd, *new_fd = NULL;
2369         struct cred *new_cred = NULL;
2370         struct nsproxy *new_nsproxy = NULL;
2371         int do_sysvsem = 0;
2372         int err;
2373
2374         /*
2375          * If unsharing a user namespace must also unshare the thread group
2376          * and unshare the filesystem root and working directories.
2377          */
2378         if (unshare_flags & CLONE_NEWUSER)
2379                 unshare_flags |= CLONE_THREAD | CLONE_FS;
2380         /*
2381          * If unsharing vm, must also unshare signal handlers.
2382          */
2383         if (unshare_flags & CLONE_VM)
2384                 unshare_flags |= CLONE_SIGHAND;
2385         /*
2386          * If unsharing a signal handlers, must also unshare the signal queues.
2387          */
2388         if (unshare_flags & CLONE_SIGHAND)
2389                 unshare_flags |= CLONE_THREAD;
2390         /*
2391          * If unsharing namespace, must also unshare filesystem information.
2392          */
2393         if (unshare_flags & CLONE_NEWNS)
2394                 unshare_flags |= CLONE_FS;
2395
2396         err = check_unshare_flags(unshare_flags);
2397         if (err)
2398                 goto bad_unshare_out;
2399         /*
2400          * CLONE_NEWIPC must also detach from the undolist: after switching
2401          * to a new ipc namespace, the semaphore arrays from the old
2402          * namespace are unreachable.
2403          */
2404         if (unshare_flags & (CLONE_NEWIPC|CLONE_SYSVSEM))
2405                 do_sysvsem = 1;
2406         err = unshare_fs(unshare_flags, &new_fs);
2407         if (err)
2408                 goto bad_unshare_out;
2409         err = unshare_fd(unshare_flags, &new_fd);
2410         if (err)
2411                 goto bad_unshare_cleanup_fs;
2412         err = unshare_userns(unshare_flags, &new_cred);
2413         if (err)
2414                 goto bad_unshare_cleanup_fd;
2415         err = unshare_nsproxy_namespaces(unshare_flags, &new_nsproxy,
2416                                          new_cred, new_fs);
2417         if (err)
2418                 goto bad_unshare_cleanup_cred;
2419
2420         if (new_fs || new_fd || do_sysvsem || new_cred || new_nsproxy) {
2421                 if (do_sysvsem) {
2422                         /*
2423                          * CLONE_SYSVSEM is equivalent to sys_exit().
2424                          */
2425                         exit_sem(current);
2426                 }
2427                 if (unshare_flags & CLONE_NEWIPC) {
2428                         /* Orphan segments in old ns (see sem above). */
2429                         exit_shm(current);
2430                         shm_init_task(current);
2431                 }
2432
2433                 if (new_nsproxy)
2434                         switch_task_namespaces(current, new_nsproxy);
2435
2436                 task_lock(current);
2437
2438                 if (new_fs) {
2439                         fs = current->fs;
2440                         spin_lock(&fs->lock);
2441                         current->fs = new_fs;
2442                         if (--fs->users)
2443                                 new_fs = NULL;
2444                         else
2445                                 new_fs = fs;
2446                         spin_unlock(&fs->lock);
2447                 }
2448
2449                 if (new_fd) {
2450                         fd = current->files;
2451                         current->files = new_fd;
2452                         new_fd = fd;
2453                 }
2454
2455                 task_unlock(current);
2456
2457                 if (new_cred) {
2458                         /* Install the new user namespace */
2459                         commit_creds(new_cred);
2460                         new_cred = NULL;
2461                 }
2462         }
2463
2464         perf_event_namespaces(current);
2465
2466 bad_unshare_cleanup_cred:
2467         if (new_cred)
2468                 put_cred(new_cred);
2469 bad_unshare_cleanup_fd:
2470         if (new_fd)
2471                 put_files_struct(new_fd);
2472
2473 bad_unshare_cleanup_fs:
2474         if (new_fs)
2475                 free_fs_struct(new_fs);
2476
2477 bad_unshare_out:
2478         return err;
2479 }
2480
2481 /*
2482  *      Helper to unshare the files of the current task.
2483  *      We don't want to expose copy_files internals to
2484  *      the exec layer of the kernel.
2485  */
2486
2487 int unshare_files(struct files_struct **displaced)
2488 {
2489         struct task_struct *task = current;
2490         struct files_struct *copy = NULL;
2491         int error;
2492
2493         error = unshare_fd(CLONE_FILES, &copy);
2494         if (error || !copy) {
2495                 *displaced = NULL;
2496                 return error;
2497         }
2498         *displaced = task->files;
2499         task_lock(task);
2500         task->files = copy;
2501         task_unlock(task);
2502         return 0;
2503 }
2504
2505 int sysctl_max_threads(struct ctl_table *table, int write,
2506                        void __user *buffer, size_t *lenp, loff_t *ppos)
2507 {
2508         struct ctl_table t;
2509         int ret;
2510         int threads = max_threads;
2511         int min = MIN_THREADS;
2512         int max = MAX_THREADS;
2513
2514         t = *table;
2515         t.data = &threads;
2516         t.extra1 = &min;
2517         t.extra2 = &max;
2518
2519         ret = proc_dointvec_minmax(&t, write, buffer, lenp, ppos);
2520         if (ret || !write)
2521                 return ret;
2522
2523         set_max_threads(threads);
2524
2525         return 0;
2526 }