Root/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/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>
30#include <linux/fs.h>
31#include <linux/nsproxy.h>
32#include <linux/capability.h>
33#include <linux/cpu.h>
34#include <linux/cgroup.h>
35#include <linux/security.h>
36#include <linux/hugetlb.h>
37#include <linux/swap.h>
38#include <linux/syscalls.h>
39#include <linux/jiffies.h>
40#include <linux/tracehook.h>
41#include <linux/futex.h>
42#include <linux/compat.h>
43#include <linux/task_io_accounting_ops.h>
44#include <linux/rcupdate.h>
45#include <linux/ptrace.h>
46#include <linux/mount.h>
47#include <linux/audit.h>
48#include <linux/memcontrol.h>
49#include <linux/ftrace.h>
50#include <linux/profile.h>
51#include <linux/rmap.h>
52#include <linux/ksm.h>
53#include <linux/acct.h>
54#include <linux/tsacct_kern.h>
55#include <linux/cn_proc.h>
56#include <linux/freezer.h>
57#include <linux/delayacct.h>
58#include <linux/taskstats_kern.h>
59#include <linux/random.h>
60#include <linux/tty.h>
61#include <linux/proc_fs.h>
62#include <linux/blkdev.h>
63#include <linux/fs_struct.h>
64#include <linux/magic.h>
65#include <linux/perf_event.h>
66#include <linux/posix-timers.h>
67#include <linux/user-return-notifier.h>
68
69#include <asm/pgtable.h>
70#include <asm/pgalloc.h>
71#include <asm/uaccess.h>
72#include <asm/mmu_context.h>
73#include <asm/cacheflush.h>
74#include <asm/tlbflush.h>
75
76#include <trace/events/sched.h>
77
78/*
79 * Protected counters by write_lock_irq(&tasklist_lock)
80 */
81unsigned long total_forks; /* Handle normal Linux uptimes. */
82int nr_threads; /* The idle threads do not count.. */
83
84int max_threads; /* tunable limit on nr_threads */
85
86DEFINE_PER_CPU(unsigned long, process_counts) = 0;
87
88__cacheline_aligned DEFINE_RWLOCK(tasklist_lock); /* outer */
89
90#ifdef CONFIG_PROVE_RCU
91int lockdep_tasklist_lock_is_held(void)
92{
93    return lockdep_is_held(&tasklist_lock);
94}
95EXPORT_SYMBOL_GPL(lockdep_tasklist_lock_is_held);
96#endif /* #ifdef CONFIG_PROVE_RCU */
97
98int nr_processes(void)
99{
100    int cpu;
101    int total = 0;
102
103    for_each_possible_cpu(cpu)
104        total += per_cpu(process_counts, cpu);
105
106    return total;
107}
108
109#ifndef __HAVE_ARCH_TASK_STRUCT_ALLOCATOR
110# define alloc_task_struct() kmem_cache_alloc(task_struct_cachep, GFP_KERNEL)
111# define free_task_struct(tsk) kmem_cache_free(task_struct_cachep, (tsk))
112static struct kmem_cache *task_struct_cachep;
113#endif
114
115#ifndef __HAVE_ARCH_THREAD_INFO_ALLOCATOR
116static inline struct thread_info *alloc_thread_info(struct task_struct *tsk)
117{
118#ifdef CONFIG_DEBUG_STACK_USAGE
119    gfp_t mask = GFP_KERNEL | __GFP_ZERO;
120#else
121    gfp_t mask = GFP_KERNEL;
122#endif
123    return (struct thread_info *)__get_free_pages(mask, THREAD_SIZE_ORDER);
124}
125
126static inline void free_thread_info(struct thread_info *ti)
127{
128    free_pages((unsigned long)ti, THREAD_SIZE_ORDER);
129}
130#endif
131
132/* SLAB cache for signal_struct structures (tsk->signal) */
133static struct kmem_cache *signal_cachep;
134
135/* SLAB cache for sighand_struct structures (tsk->sighand) */
136struct kmem_cache *sighand_cachep;
137
138/* SLAB cache for files_struct structures (tsk->files) */
139struct kmem_cache *files_cachep;
140
141/* SLAB cache for fs_struct structures (tsk->fs) */
142struct kmem_cache *fs_cachep;
143
144/* SLAB cache for vm_area_struct structures */
145struct kmem_cache *vm_area_cachep;
146
147/* SLAB cache for mm_struct structures (tsk->mm) */
148static struct kmem_cache *mm_cachep;
149
150static void account_kernel_stack(struct thread_info *ti, int account)
151{
152    struct zone *zone = page_zone(virt_to_page(ti));
153
154    mod_zone_page_state(zone, NR_KERNEL_STACK, account);
155}
156
157void free_task(struct task_struct *tsk)
158{
159    prop_local_destroy_single(&tsk->dirties);
160    account_kernel_stack(tsk->stack, -1);
161    free_thread_info(tsk->stack);
162    rt_mutex_debug_task_free(tsk);
163    ftrace_graph_exit_task(tsk);
164    free_task_struct(tsk);
165}
166EXPORT_SYMBOL(free_task);
167
168static inline void free_signal_struct(struct signal_struct *sig)
169{
170    taskstats_tgid_free(sig);
171    kmem_cache_free(signal_cachep, sig);
172}
173
174static inline void put_signal_struct(struct signal_struct *sig)
175{
176    if (atomic_dec_and_test(&sig->sigcnt))
177        free_signal_struct(sig);
178}
179
180void __put_task_struct(struct task_struct *tsk)
181{
182    WARN_ON(!tsk->exit_state);
183    WARN_ON(atomic_read(&tsk->usage));
184    WARN_ON(tsk == current);
185
186    exit_creds(tsk);
187    delayacct_tsk_free(tsk);
188    put_signal_struct(tsk->signal);
189
190    if (!profile_handoff_task(tsk))
191        free_task(tsk);
192}
193
194/*
195 * macro override instead of weak attribute alias, to workaround
196 * gcc 4.1.0 and 4.1.1 bugs with weak attribute and empty functions.
197 */
198#ifndef arch_task_cache_init
199#define arch_task_cache_init()
200#endif
201
202void __init fork_init(unsigned long mempages)
203{
204#ifndef __HAVE_ARCH_TASK_STRUCT_ALLOCATOR
205#ifndef ARCH_MIN_TASKALIGN
206#define ARCH_MIN_TASKALIGN L1_CACHE_BYTES
207#endif
208    /* create a slab on which task_structs can be allocated */
209    task_struct_cachep =
210        kmem_cache_create("task_struct", sizeof(struct task_struct),
211            ARCH_MIN_TASKALIGN, SLAB_PANIC | SLAB_NOTRACK, NULL);
212#endif
213
214    /* do the arch specific task caches init */
215    arch_task_cache_init();
216
217    /*
218     * The default maximum number of threads is set to a safe
219     * value: the thread structures can take up at most half
220     * of memory.
221     */
222    max_threads = mempages / (8 * THREAD_SIZE / PAGE_SIZE);
223
224    /*
225     * we need to allow at least 20 threads to boot a system
226     */
227    if(max_threads < 20)
228        max_threads = 20;
229
230    init_task.signal->rlim[RLIMIT_NPROC].rlim_cur = max_threads/2;
231    init_task.signal->rlim[RLIMIT_NPROC].rlim_max = max_threads/2;
232    init_task.signal->rlim[RLIMIT_SIGPENDING] =
233        init_task.signal->rlim[RLIMIT_NPROC];
234}
235
236int __attribute__((weak)) arch_dup_task_struct(struct task_struct *dst,
237                           struct task_struct *src)
238{
239    *dst = *src;
240    return 0;
241}
242
243static struct task_struct *dup_task_struct(struct task_struct *orig)
244{
245    struct task_struct *tsk;
246    struct thread_info *ti;
247    unsigned long *stackend;
248
249    int err;
250
251    prepare_to_copy(orig);
252
253    tsk = alloc_task_struct();
254    if (!tsk)
255        return NULL;
256
257    ti = alloc_thread_info(tsk);
258    if (!ti) {
259        free_task_struct(tsk);
260        return NULL;
261    }
262
263     err = arch_dup_task_struct(tsk, orig);
264    if (err)
265        goto out;
266
267    tsk->stack = ti;
268
269    err = prop_local_init_single(&tsk->dirties);
270    if (err)
271        goto out;
272
273    setup_thread_stack(tsk, orig);
274    clear_user_return_notifier(tsk);
275    stackend = end_of_stack(tsk);
276    *stackend = STACK_END_MAGIC; /* for overflow detection */
277
278#ifdef CONFIG_CC_STACKPROTECTOR
279    tsk->stack_canary = get_random_int();
280#endif
281
282    /* One for us, one for whoever does the "release_task()" (usually parent) */
283    atomic_set(&tsk->usage,2);
284    atomic_set(&tsk->fs_excl, 0);
285#ifdef CONFIG_BLK_DEV_IO_TRACE
286    tsk->btrace_seq = 0;
287#endif
288    tsk->splice_pipe = NULL;
289
290    account_kernel_stack(ti, 1);
291
292    return tsk;
293
294out:
295    free_thread_info(ti);
296    free_task_struct(tsk);
297    return NULL;
298}
299
300#ifdef CONFIG_MMU
301static int dup_mmap(struct mm_struct *mm, struct mm_struct *oldmm)
302{
303    struct vm_area_struct *mpnt, *tmp, *prev, **pprev;
304    struct rb_node **rb_link, *rb_parent;
305    int retval;
306    unsigned long charge;
307    struct mempolicy *pol;
308
309    down_write(&oldmm->mmap_sem);
310    flush_cache_dup_mm(oldmm);
311    /*
312     * Not linked in yet - no deadlock potential:
313     */
314    down_write_nested(&mm->mmap_sem, SINGLE_DEPTH_NESTING);
315
316    mm->locked_vm = 0;
317    mm->mmap = NULL;
318    mm->mmap_cache = NULL;
319    mm->free_area_cache = oldmm->mmap_base;
320    mm->cached_hole_size = ~0UL;
321    mm->map_count = 0;
322    cpumask_clear(mm_cpumask(mm));
323    mm->mm_rb = RB_ROOT;
324    rb_link = &mm->mm_rb.rb_node;
325    rb_parent = NULL;
326    pprev = &mm->mmap;
327    retval = ksm_fork(mm, oldmm);
328    if (retval)
329        goto out;
330
331    prev = NULL;
332    for (mpnt = oldmm->mmap; mpnt; mpnt = mpnt->vm_next) {
333        struct file *file;
334
335        if (mpnt->vm_flags & VM_DONTCOPY) {
336            long pages = vma_pages(mpnt);
337            mm->total_vm -= pages;
338            vm_stat_account(mm, mpnt->vm_flags, mpnt->vm_file,
339                                -pages);
340            continue;
341        }
342        charge = 0;
343        if (mpnt->vm_flags & VM_ACCOUNT) {
344            unsigned int len = (mpnt->vm_end - mpnt->vm_start) >> PAGE_SHIFT;
345            if (security_vm_enough_memory(len))
346                goto fail_nomem;
347            charge = len;
348        }
349        tmp = kmem_cache_alloc(vm_area_cachep, GFP_KERNEL);
350        if (!tmp)
351            goto fail_nomem;
352        *tmp = *mpnt;
353        INIT_LIST_HEAD(&tmp->anon_vma_chain);
354        pol = mpol_dup(vma_policy(mpnt));
355        retval = PTR_ERR(pol);
356        if (IS_ERR(pol))
357            goto fail_nomem_policy;
358        vma_set_policy(tmp, pol);
359        tmp->vm_mm = mm;
360        if (anon_vma_fork(tmp, mpnt))
361            goto fail_nomem_anon_vma_fork;
362        tmp->vm_flags &= ~VM_LOCKED;
363        tmp->vm_next = tmp->vm_prev = NULL;
364        file = tmp->vm_file;
365        if (file) {
366            struct inode *inode = file->f_path.dentry->d_inode;
367            struct address_space *mapping = file->f_mapping;
368
369            get_file(file);
370            if (tmp->vm_flags & VM_DENYWRITE)
371                atomic_dec(&inode->i_writecount);
372            spin_lock(&mapping->i_mmap_lock);
373            if (tmp->vm_flags & VM_SHARED)
374                mapping->i_mmap_writable++;
375            tmp->vm_truncate_count = mpnt->vm_truncate_count;
376            flush_dcache_mmap_lock(mapping);
377            /* insert tmp into the share list, just after mpnt */
378            vma_prio_tree_add(tmp, mpnt);
379            flush_dcache_mmap_unlock(mapping);
380            spin_unlock(&mapping->i_mmap_lock);
381        }
382
383        /*
384         * Clear hugetlb-related page reserves for children. This only
385         * affects MAP_PRIVATE mappings. Faults generated by the child
386         * are not guaranteed to succeed, even if read-only
387         */
388        if (is_vm_hugetlb_page(tmp))
389            reset_vma_resv_huge_pages(tmp);
390
391        /*
392         * Link in the new vma and copy the page table entries.
393         */
394        *pprev = tmp;
395        pprev = &tmp->vm_next;
396        tmp->vm_prev = prev;
397        prev = tmp;
398
399        __vma_link_rb(mm, tmp, rb_link, rb_parent);
400        rb_link = &tmp->vm_rb.rb_right;
401        rb_parent = &tmp->vm_rb;
402
403        mm->map_count++;
404        retval = copy_page_range(mm, oldmm, mpnt);
405
406        if (tmp->vm_ops && tmp->vm_ops->open)
407            tmp->vm_ops->open(tmp);
408
409        if (retval)
410            goto out;
411    }
412    /* a new mm has just been created */
413    arch_dup_mmap(oldmm, mm);
414    retval = 0;
415out:
416    up_write(&mm->mmap_sem);
417    flush_tlb_mm(oldmm);
418    up_write(&oldmm->mmap_sem);
419    return retval;
420fail_nomem_anon_vma_fork:
421    mpol_put(pol);
422fail_nomem_policy:
423    kmem_cache_free(vm_area_cachep, tmp);
424fail_nomem:
425    retval = -ENOMEM;
426    vm_unacct_memory(charge);
427    goto out;
428}
429
430static inline int mm_alloc_pgd(struct mm_struct * mm)
431{
432    mm->pgd = pgd_alloc(mm);
433    if (unlikely(!mm->pgd))
434        return -ENOMEM;
435    return 0;
436}
437
438static inline void mm_free_pgd(struct mm_struct * mm)
439{
440    pgd_free(mm, mm->pgd);
441}
442#else
443#define dup_mmap(mm, oldmm) (0)
444#define mm_alloc_pgd(mm) (0)
445#define mm_free_pgd(mm)
446#endif /* CONFIG_MMU */
447
448__cacheline_aligned_in_smp DEFINE_SPINLOCK(mmlist_lock);
449
450#define allocate_mm() (kmem_cache_alloc(mm_cachep, GFP_KERNEL))
451#define free_mm(mm) (kmem_cache_free(mm_cachep, (mm)))
452
453static unsigned long default_dump_filter = MMF_DUMP_FILTER_DEFAULT;
454
455static int __init coredump_filter_setup(char *s)
456{
457    default_dump_filter =
458        (simple_strtoul(s, NULL, 0) << MMF_DUMP_FILTER_SHIFT) &
459        MMF_DUMP_FILTER_MASK;
460    return 1;
461}
462
463__setup("coredump_filter=", coredump_filter_setup);
464
465#include <linux/init_task.h>
466
467static void mm_init_aio(struct mm_struct *mm)
468{
469#ifdef CONFIG_AIO
470    spin_lock_init(&mm->ioctx_lock);
471    INIT_HLIST_HEAD(&mm->ioctx_list);
472#endif
473}
474
475static struct mm_struct * mm_init(struct mm_struct * mm, struct task_struct *p)
476{
477    atomic_set(&mm->mm_users, 1);
478    atomic_set(&mm->mm_count, 1);
479    init_rwsem(&mm->mmap_sem);
480    INIT_LIST_HEAD(&mm->mmlist);
481    mm->flags = (current->mm) ?
482        (current->mm->flags & MMF_INIT_MASK) : default_dump_filter;
483    mm->core_state = NULL;
484    mm->nr_ptes = 0;
485    memset(&mm->rss_stat, 0, sizeof(mm->rss_stat));
486    spin_lock_init(&mm->page_table_lock);
487    mm->free_area_cache = TASK_UNMAPPED_BASE;
488    mm->cached_hole_size = ~0UL;
489    mm_init_aio(mm);
490    mm_init_owner(mm, p);
491
492    if (likely(!mm_alloc_pgd(mm))) {
493        mm->def_flags = 0;
494        mmu_notifier_mm_init(mm);
495        return mm;
496    }
497
498    free_mm(mm);
499    return NULL;
500}
501
502/*
503 * Allocate and initialize an mm_struct.
504 */
505struct mm_struct * mm_alloc(void)
506{
507    struct mm_struct * mm;
508
509    mm = allocate_mm();
510    if (mm) {
511        memset(mm, 0, sizeof(*mm));
512        mm = mm_init(mm, current);
513    }
514    return mm;
515}
516
517/*
518 * Called when the last reference to the mm
519 * is dropped: either by a lazy thread or by
520 * mmput. Free the page directory and the mm.
521 */
522void __mmdrop(struct mm_struct *mm)
523{
524    BUG_ON(mm == &init_mm);
525    mm_free_pgd(mm);
526    destroy_context(mm);
527    mmu_notifier_mm_destroy(mm);
528    free_mm(mm);
529}
530EXPORT_SYMBOL_GPL(__mmdrop);
531
532/*
533 * Decrement the use count and release all resources for an mm.
534 */
535void mmput(struct mm_struct *mm)
536{
537    might_sleep();
538
539    if (atomic_dec_and_test(&mm->mm_users)) {
540        exit_aio(mm);
541        ksm_exit(mm);
542        exit_mmap(mm);
543        set_mm_exe_file(mm, NULL);
544        if (!list_empty(&mm->mmlist)) {
545            spin_lock(&mmlist_lock);
546            list_del(&mm->mmlist);
547            spin_unlock(&mmlist_lock);
548        }
549        put_swap_token(mm);
550        if (mm->binfmt)
551            module_put(mm->binfmt->module);
552        mmdrop(mm);
553    }
554}
555EXPORT_SYMBOL_GPL(mmput);
556
557/**
558 * get_task_mm - acquire a reference to the task's mm
559 *
560 * Returns %NULL if the task has no mm. Checks PF_KTHREAD (meaning
561 * this kernel workthread has transiently adopted a user mm with use_mm,
562 * to do its AIO) is not set and if so returns a reference to it, after
563 * bumping up the use count. User must release the mm via mmput()
564 * after use. Typically used by /proc and ptrace.
565 */
566struct mm_struct *get_task_mm(struct task_struct *task)
567{
568    struct mm_struct *mm;
569
570    task_lock(task);
571    mm = task->mm;
572    if (mm) {
573        if (task->flags & PF_KTHREAD)
574            mm = NULL;
575        else
576            atomic_inc(&mm->mm_users);
577    }
578    task_unlock(task);
579    return mm;
580}
581EXPORT_SYMBOL_GPL(get_task_mm);
582
583/* Please note the differences between mmput and mm_release.
584 * mmput is called whenever we stop holding onto a mm_struct,
585 * error success whatever.
586 *
587 * mm_release is called after a mm_struct has been removed
588 * from the current process.
589 *
590 * This difference is important for error handling, when we
591 * only half set up a mm_struct for a new process and need to restore
592 * the old one. Because we mmput the new mm_struct before
593 * restoring the old one. . .
594 * Eric Biederman 10 January 1998
595 */
596void mm_release(struct task_struct *tsk, struct mm_struct *mm)
597{
598    struct completion *vfork_done = tsk->vfork_done;
599
600    /* Get rid of any futexes when releasing the mm */
601#ifdef CONFIG_FUTEX
602    if (unlikely(tsk->robust_list)) {
603        exit_robust_list(tsk);
604        tsk->robust_list = NULL;
605    }
606#ifdef CONFIG_COMPAT
607    if (unlikely(tsk->compat_robust_list)) {
608        compat_exit_robust_list(tsk);
609        tsk->compat_robust_list = NULL;
610    }
611#endif
612    if (unlikely(!list_empty(&tsk->pi_state_list)))
613        exit_pi_state_list(tsk);
614#endif
615
616    /* Get rid of any cached register state */
617    deactivate_mm(tsk, mm);
618
619    /* notify parent sleeping on vfork() */
620    if (vfork_done) {
621        tsk->vfork_done = NULL;
622        complete(vfork_done);
623    }
624
625    /*
626     * If we're exiting normally, clear a user-space tid field if
627     * requested. We leave this alone when dying by signal, to leave
628     * the value intact in a core dump, and to save the unnecessary
629     * trouble otherwise. Userland only wants this done for a sys_exit.
630     */
631    if (tsk->clear_child_tid) {
632        if (!(tsk->flags & PF_SIGNALED) &&
633            atomic_read(&mm->mm_users) > 1) {
634            /*
635             * We don't check the error code - if userspace has
636             * not set up a proper pointer then tough luck.
637             */
638            put_user(0, tsk->clear_child_tid);
639            sys_futex(tsk->clear_child_tid, FUTEX_WAKE,
640                    1, NULL, NULL, 0);
641        }
642        tsk->clear_child_tid = NULL;
643    }
644}
645
646/*
647 * Allocate a new mm structure and copy contents from the
648 * mm structure of the passed in task structure.
649 */
650struct mm_struct *dup_mm(struct task_struct *tsk)
651{
652    struct mm_struct *mm, *oldmm = current->mm;
653    int err;
654
655    if (!oldmm)
656        return NULL;
657
658    mm = allocate_mm();
659    if (!mm)
660        goto fail_nomem;
661
662    memcpy(mm, oldmm, sizeof(*mm));
663
664    /* Initializing for Swap token stuff */
665    mm->token_priority = 0;
666    mm->last_interval = 0;
667
668    if (!mm_init(mm, tsk))
669        goto fail_nomem;
670
671    if (init_new_context(tsk, mm))
672        goto fail_nocontext;
673
674    dup_mm_exe_file(oldmm, mm);
675
676    err = dup_mmap(mm, oldmm);
677    if (err)
678        goto free_pt;
679
680    mm->hiwater_rss = get_mm_rss(mm);
681    mm->hiwater_vm = mm->total_vm;
682
683    if (mm->binfmt && !try_module_get(mm->binfmt->module))
684        goto free_pt;
685
686    return mm;
687
688free_pt:
689    /* don't put binfmt in mmput, we haven't got module yet */
690    mm->binfmt = NULL;
691    mmput(mm);
692
693fail_nomem:
694    return NULL;
695
696fail_nocontext:
697    /*
698     * If init_new_context() failed, we cannot use mmput() to free the mm
699     * because it calls destroy_context()
700     */
701    mm_free_pgd(mm);
702    free_mm(mm);
703    return NULL;
704}
705
706static int copy_mm(unsigned long clone_flags, struct task_struct * tsk)
707{
708    struct mm_struct * mm, *oldmm;
709    int retval;
710
711    tsk->min_flt = tsk->maj_flt = 0;
712    tsk->nvcsw = tsk->nivcsw = 0;
713#ifdef CONFIG_DETECT_HUNG_TASK
714    tsk->last_switch_count = tsk->nvcsw + tsk->nivcsw;
715#endif
716
717    tsk->mm = NULL;
718    tsk->active_mm = NULL;
719
720    /*
721     * Are we cloning a kernel thread?
722     *
723     * We need to steal a active VM for that..
724     */
725    oldmm = current->mm;
726    if (!oldmm)
727        return 0;
728
729    if (clone_flags & CLONE_VM) {
730        atomic_inc(&oldmm->mm_users);
731        mm = oldmm;
732        goto good_mm;
733    }
734
735    retval = -ENOMEM;
736    mm = dup_mm(tsk);
737    if (!mm)
738        goto fail_nomem;
739
740good_mm:
741    /* Initializing for Swap token stuff */
742    mm->token_priority = 0;
743    mm->last_interval = 0;
744
745    tsk->mm = mm;
746    tsk->active_mm = mm;
747    return 0;
748
749fail_nomem:
750    return retval;
751}
752
753static int copy_fs(unsigned long clone_flags, struct task_struct *tsk)
754{
755    struct fs_struct *fs = current->fs;
756    if (clone_flags & CLONE_FS) {
757        /* tsk->fs is already what we want */
758        spin_lock(&fs->lock);
759        if (fs->in_exec) {
760            spin_unlock(&fs->lock);
761            return -EAGAIN;
762        }
763        fs->users++;
764        spin_unlock(&fs->lock);
765        return 0;
766    }
767    tsk->fs = copy_fs_struct(fs);
768    if (!tsk->fs)
769        return -ENOMEM;
770    return 0;
771}
772
773static int copy_files(unsigned long clone_flags, struct task_struct * tsk)
774{
775    struct files_struct *oldf, *newf;
776    int error = 0;
777
778    /*
779     * A background process may not have any files ...
780     */
781    oldf = current->files;
782    if (!oldf)
783        goto out;
784
785    if (clone_flags & CLONE_FILES) {
786        atomic_inc(&oldf->count);
787        goto out;
788    }
789
790    newf = dup_fd(oldf, &error);
791    if (!newf)
792        goto out;
793
794    tsk->files = newf;
795    error = 0;
796out:
797    return error;
798}
799
800static int copy_io(unsigned long clone_flags, struct task_struct *tsk)
801{
802#ifdef CONFIG_BLOCK
803    struct io_context *ioc = current->io_context;
804
805    if (!ioc)
806        return 0;
807    /*
808     * Share io context with parent, if CLONE_IO is set
809     */
810    if (clone_flags & CLONE_IO) {
811        tsk->io_context = ioc_task_link(ioc);
812        if (unlikely(!tsk->io_context))
813            return -ENOMEM;
814    } else if (ioprio_valid(ioc->ioprio)) {
815        tsk->io_context = alloc_io_context(GFP_KERNEL, -1);
816        if (unlikely(!tsk->io_context))
817            return -ENOMEM;
818
819        tsk->io_context->ioprio = ioc->ioprio;
820    }
821#endif
822    return 0;
823}
824
825static int copy_sighand(unsigned long clone_flags, struct task_struct *tsk)
826{
827    struct sighand_struct *sig;
828
829    if (clone_flags & CLONE_SIGHAND) {
830        atomic_inc(&current->sighand->count);
831        return 0;
832    }
833    sig = kmem_cache_alloc(sighand_cachep, GFP_KERNEL);
834    rcu_assign_pointer(tsk->sighand, sig);
835    if (!sig)
836        return -ENOMEM;
837    atomic_set(&sig->count, 1);
838    memcpy(sig->action, current->sighand->action, sizeof(sig->action));
839    return 0;
840}
841
842void __cleanup_sighand(struct sighand_struct *sighand)
843{
844    if (atomic_dec_and_test(&sighand->count))
845        kmem_cache_free(sighand_cachep, sighand);
846}
847
848
849/*
850 * Initialize POSIX timer handling for a thread group.
851 */
852static void posix_cpu_timers_init_group(struct signal_struct *sig)
853{
854    unsigned long cpu_limit;
855
856    /* Thread group counters. */
857    thread_group_cputime_init(sig);
858
859    cpu_limit = ACCESS_ONCE(sig->rlim[RLIMIT_CPU].rlim_cur);
860    if (cpu_limit != RLIM_INFINITY) {
861        sig->cputime_expires.prof_exp = secs_to_cputime(cpu_limit);
862        sig->cputimer.running = 1;
863    }
864
865    /* The timer lists. */
866    INIT_LIST_HEAD(&sig->cpu_timers[0]);
867    INIT_LIST_HEAD(&sig->cpu_timers[1]);
868    INIT_LIST_HEAD(&sig->cpu_timers[2]);
869}
870
871static int copy_signal(unsigned long clone_flags, struct task_struct *tsk)
872{
873    struct signal_struct *sig;
874
875    if (clone_flags & CLONE_THREAD)
876        return 0;
877
878    sig = kmem_cache_zalloc(signal_cachep, GFP_KERNEL);
879    tsk->signal = sig;
880    if (!sig)
881        return -ENOMEM;
882
883    sig->nr_threads = 1;
884    atomic_set(&sig->live, 1);
885    atomic_set(&sig->sigcnt, 1);
886    init_waitqueue_head(&sig->wait_chldexit);
887    if (clone_flags & CLONE_NEWPID)
888        sig->flags |= SIGNAL_UNKILLABLE;
889    sig->curr_target = tsk;
890    init_sigpending(&sig->shared_pending);
891    INIT_LIST_HEAD(&sig->posix_timers);
892
893    hrtimer_init(&sig->real_timer, CLOCK_MONOTONIC, HRTIMER_MODE_REL);
894    sig->real_timer.function = it_real_fn;
895
896    task_lock(current->group_leader);
897    memcpy(sig->rlim, current->signal->rlim, sizeof sig->rlim);
898    task_unlock(current->group_leader);
899
900    posix_cpu_timers_init_group(sig);
901
902    tty_audit_fork(sig);
903
904    sig->oom_adj = current->signal->oom_adj;
905    sig->oom_score_adj = current->signal->oom_score_adj;
906
907    return 0;
908}
909
910static void copy_flags(unsigned long clone_flags, struct task_struct *p)
911{
912    unsigned long new_flags = p->flags;
913
914    new_flags &= ~(PF_SUPERPRIV | PF_WQ_WORKER);
915    new_flags |= PF_FORKNOEXEC;
916    new_flags |= PF_STARTING;
917    p->flags = new_flags;
918    clear_freeze_flag(p);
919}
920
921SYSCALL_DEFINE1(set_tid_address, int __user *, tidptr)
922{
923    current->clear_child_tid = tidptr;
924
925    return task_pid_vnr(current);
926}
927
928static void rt_mutex_init_task(struct task_struct *p)
929{
930    raw_spin_lock_init(&p->pi_lock);
931#ifdef CONFIG_RT_MUTEXES
932    plist_head_init_raw(&p->pi_waiters, &p->pi_lock);
933    p->pi_blocked_on = NULL;
934#endif
935}
936
937#ifdef CONFIG_MM_OWNER
938void mm_init_owner(struct mm_struct *mm, struct task_struct *p)
939{
940    mm->owner = p;
941}
942#endif /* CONFIG_MM_OWNER */
943
944/*
945 * Initialize POSIX timer handling for a single task.
946 */
947static void posix_cpu_timers_init(struct task_struct *tsk)
948{
949    tsk->cputime_expires.prof_exp = cputime_zero;
950    tsk->cputime_expires.virt_exp = cputime_zero;
951    tsk->cputime_expires.sched_exp = 0;
952    INIT_LIST_HEAD(&tsk->cpu_timers[0]);
953    INIT_LIST_HEAD(&tsk->cpu_timers[1]);
954    INIT_LIST_HEAD(&tsk->cpu_timers[2]);
955}
956
957/*
958 * This creates a new process as a copy of the old one,
959 * but does not actually start it yet.
960 *
961 * It copies the registers, and all the appropriate
962 * parts of the process environment (as per the clone
963 * flags). The actual kick-off is left to the caller.
964 */
965static struct task_struct *copy_process(unsigned long clone_flags,
966                    unsigned long stack_start,
967                    struct pt_regs *regs,
968                    unsigned long stack_size,
969                    int __user *child_tidptr,
970                    struct pid *pid,
971                    int trace)
972{
973    int retval;
974    struct task_struct *p;
975    int cgroup_callbacks_done = 0;
976
977    if ((clone_flags & (CLONE_NEWNS|CLONE_FS)) == (CLONE_NEWNS|CLONE_FS))
978        return ERR_PTR(-EINVAL);
979
980    /*
981     * Thread groups must share signals as well, and detached threads
982     * can only be started up within the thread group.
983     */
984    if ((clone_flags & CLONE_THREAD) && !(clone_flags & CLONE_SIGHAND))
985        return ERR_PTR(-EINVAL);
986
987    /*
988     * Shared signal handlers imply shared VM. By way of the above,
989     * thread groups also imply shared VM. Blocking this case allows
990     * for various simplifications in other code.
991     */
992    if ((clone_flags & CLONE_SIGHAND) && !(clone_flags & CLONE_VM))
993        return ERR_PTR(-EINVAL);
994
995    /*
996     * Siblings of global init remain as zombies on exit since they are
997     * not reaped by their parent (swapper). To solve this and to avoid
998     * multi-rooted process trees, prevent global and container-inits
999     * from creating siblings.
1000     */
1001    if ((clone_flags & CLONE_PARENT) &&
1002                current->signal->flags & SIGNAL_UNKILLABLE)
1003        return ERR_PTR(-EINVAL);
1004
1005    retval = security_task_create(clone_flags);
1006    if (retval)
1007        goto fork_out;
1008
1009    retval = -ENOMEM;
1010    p = dup_task_struct(current);
1011    if (!p)
1012        goto fork_out;
1013
1014    ftrace_graph_init_task(p);
1015
1016    rt_mutex_init_task(p);
1017
1018#ifdef CONFIG_PROVE_LOCKING
1019    DEBUG_LOCKS_WARN_ON(!p->hardirqs_enabled);
1020    DEBUG_LOCKS_WARN_ON(!p->softirqs_enabled);
1021#endif
1022    retval = -EAGAIN;
1023    if (atomic_read(&p->real_cred->user->processes) >=
1024            task_rlimit(p, RLIMIT_NPROC)) {
1025        if (!capable(CAP_SYS_ADMIN) && !capable(CAP_SYS_RESOURCE) &&
1026            p->real_cred->user != INIT_USER)
1027            goto bad_fork_free;
1028    }
1029
1030    retval = copy_creds(p, clone_flags);
1031    if (retval < 0)
1032        goto bad_fork_free;
1033
1034    /*
1035     * If multiple threads are within copy_process(), then this check
1036     * triggers too late. This doesn't hurt, the check is only there
1037     * to stop root fork bombs.
1038     */
1039    retval = -EAGAIN;
1040    if (nr_threads >= max_threads)
1041        goto bad_fork_cleanup_count;
1042
1043    if (!try_module_get(task_thread_info(p)->exec_domain->module))
1044        goto bad_fork_cleanup_count;
1045
1046    p->did_exec = 0;
1047    delayacct_tsk_init(p); /* Must remain after dup_task_struct() */
1048    copy_flags(clone_flags, p);
1049    INIT_LIST_HEAD(&p->children);
1050    INIT_LIST_HEAD(&p->sibling);
1051    rcu_copy_process(p);
1052    p->vfork_done = NULL;
1053    spin_lock_init(&p->alloc_lock);
1054
1055    init_sigpending(&p->pending);
1056
1057    p->utime = cputime_zero;
1058    p->stime = cputime_zero;
1059    p->gtime = cputime_zero;
1060    p->utimescaled = cputime_zero;
1061    p->stimescaled = cputime_zero;
1062#ifndef CONFIG_VIRT_CPU_ACCOUNTING
1063    p->prev_utime = cputime_zero;
1064    p->prev_stime = cputime_zero;
1065#endif
1066#if defined(SPLIT_RSS_COUNTING)
1067    memset(&p->rss_stat, 0, sizeof(p->rss_stat));
1068#endif
1069
1070    p->default_timer_slack_ns = current->timer_slack_ns;
1071
1072    task_io_accounting_init(&p->ioac);
1073    acct_clear_integrals(p);
1074
1075    posix_cpu_timers_init(p);
1076
1077    p->lock_depth = -1; /* -1 = no lock */
1078    do_posix_clock_monotonic_gettime(&p->start_time);
1079    p->real_start_time = p->start_time;
1080    monotonic_to_bootbased(&p->real_start_time);
1081    p->io_context = NULL;
1082    p->audit_context = NULL;
1083    cgroup_fork(p);
1084#ifdef CONFIG_NUMA
1085    p->mempolicy = mpol_dup(p->mempolicy);
1086     if (IS_ERR(p->mempolicy)) {
1087         retval = PTR_ERR(p->mempolicy);
1088         p->mempolicy = NULL;
1089         goto bad_fork_cleanup_cgroup;
1090     }
1091    mpol_fix_fork_child_flag(p);
1092#endif
1093#ifdef CONFIG_TRACE_IRQFLAGS
1094    p->irq_events = 0;
1095#ifdef __ARCH_WANT_INTERRUPTS_ON_CTXSW
1096    p->hardirqs_enabled = 1;
1097#else
1098    p->hardirqs_enabled = 0;
1099#endif
1100    p->hardirq_enable_ip = 0;
1101    p->hardirq_enable_event = 0;
1102    p->hardirq_disable_ip = _THIS_IP_;
1103    p->hardirq_disable_event = 0;
1104    p->softirqs_enabled = 1;
1105    p->softirq_enable_ip = _THIS_IP_;
1106    p->softirq_enable_event = 0;
1107    p->softirq_disable_ip = 0;
1108    p->softirq_disable_event = 0;
1109    p->hardirq_context = 0;
1110    p->softirq_context = 0;
1111#endif
1112#ifdef CONFIG_LOCKDEP
1113    p->lockdep_depth = 0; /* no locks held yet */
1114    p->curr_chain_key = 0;
1115    p->lockdep_recursion = 0;
1116#endif
1117
1118#ifdef CONFIG_DEBUG_MUTEXES
1119    p->blocked_on = NULL; /* not blocked yet */
1120#endif
1121#ifdef CONFIG_CGROUP_MEM_RES_CTLR
1122    p->memcg_batch.do_batch = 0;
1123    p->memcg_batch.memcg = NULL;
1124#endif
1125
1126    /* Perform scheduler related setup. Assign this task to a CPU. */
1127    sched_fork(p, clone_flags);
1128
1129    retval = perf_event_init_task(p);
1130    if (retval)
1131        goto bad_fork_cleanup_policy;
1132
1133    if ((retval = audit_alloc(p)))
1134        goto bad_fork_cleanup_policy;
1135    /* copy all the process information */
1136    if ((retval = copy_semundo(clone_flags, p)))
1137        goto bad_fork_cleanup_audit;
1138    if ((retval = copy_files(clone_flags, p)))
1139        goto bad_fork_cleanup_semundo;
1140    if ((retval = copy_fs(clone_flags, p)))
1141        goto bad_fork_cleanup_files;
1142    if ((retval = copy_sighand(clone_flags, p)))
1143        goto bad_fork_cleanup_fs;
1144    if ((retval = copy_signal(clone_flags, p)))
1145        goto bad_fork_cleanup_sighand;
1146    if ((retval = copy_mm(clone_flags, p)))
1147        goto bad_fork_cleanup_signal;
1148    if ((retval = copy_namespaces(clone_flags, p)))
1149        goto bad_fork_cleanup_mm;
1150    if ((retval = copy_io(clone_flags, p)))
1151        goto bad_fork_cleanup_namespaces;
1152    retval = copy_thread(clone_flags, stack_start, stack_size, p, regs);
1153    if (retval)
1154        goto bad_fork_cleanup_io;
1155
1156    if (pid != &init_struct_pid) {
1157        retval = -ENOMEM;
1158        pid = alloc_pid(p->nsproxy->pid_ns);
1159        if (!pid)
1160            goto bad_fork_cleanup_io;
1161
1162        if (clone_flags & CLONE_NEWPID) {
1163            retval = pid_ns_prepare_proc(p->nsproxy->pid_ns);
1164            if (retval < 0)
1165                goto bad_fork_free_pid;
1166        }
1167    }
1168
1169    p->pid = pid_nr(pid);
1170    p->tgid = p->pid;
1171    if (clone_flags & CLONE_THREAD)
1172        p->tgid = current->tgid;
1173
1174    if (current->nsproxy != p->nsproxy) {
1175        retval = ns_cgroup_clone(p, pid);
1176        if (retval)
1177            goto bad_fork_free_pid;
1178    }
1179
1180    p->set_child_tid = (clone_flags & CLONE_CHILD_SETTID) ? child_tidptr : NULL;
1181    /*
1182     * Clear TID on mm_release()?
1183     */
1184    p->clear_child_tid = (clone_flags & CLONE_CHILD_CLEARTID) ? child_tidptr: NULL;
1185#ifdef CONFIG_FUTEX
1186    p->robust_list = NULL;
1187#ifdef CONFIG_COMPAT
1188    p->compat_robust_list = NULL;
1189#endif
1190    INIT_LIST_HEAD(&p->pi_state_list);
1191    p->pi_state_cache = NULL;
1192#endif
1193    /*
1194     * sigaltstack should be cleared when sharing the same VM
1195     */
1196    if ((clone_flags & (CLONE_VM|CLONE_VFORK)) == CLONE_VM)
1197        p->sas_ss_sp = p->sas_ss_size = 0;
1198
1199    /*
1200     * Syscall tracing and stepping should be turned off in the
1201     * child regardless of CLONE_PTRACE.
1202     */
1203    user_disable_single_step(p);
1204    clear_tsk_thread_flag(p, TIF_SYSCALL_TRACE);
1205#ifdef TIF_SYSCALL_EMU
1206    clear_tsk_thread_flag(p, TIF_SYSCALL_EMU);
1207#endif
1208    clear_all_latency_tracing(p);
1209
1210    /* ok, now we should be set up.. */
1211    p->exit_signal = (clone_flags & CLONE_THREAD) ? -1 : (clone_flags & CSIGNAL);
1212    p->pdeath_signal = 0;
1213    p->exit_state = 0;
1214
1215    /*
1216     * Ok, make it visible to the rest of the system.
1217     * We dont wake it up yet.
1218     */
1219    p->group_leader = p;
1220    INIT_LIST_HEAD(&p->thread_group);
1221
1222    /* Now that the task is set up, run cgroup callbacks if
1223     * necessary. We need to run them before the task is visible
1224     * on the tasklist. */
1225    cgroup_fork_callbacks(p);
1226    cgroup_callbacks_done = 1;
1227
1228    /* Need tasklist lock for parent etc handling! */
1229    write_lock_irq(&tasklist_lock);
1230
1231    /* CLONE_PARENT re-uses the old parent */
1232    if (clone_flags & (CLONE_PARENT|CLONE_THREAD)) {
1233        p->real_parent = current->real_parent;
1234        p->parent_exec_id = current->parent_exec_id;
1235    } else {
1236        p->real_parent = current;
1237        p->parent_exec_id = current->self_exec_id;
1238    }
1239
1240    spin_lock(&current->sighand->siglock);
1241
1242    /*
1243     * Process group and session signals need to be delivered to just the
1244     * parent before the fork or both the parent and the child after the
1245     * fork. Restart if a signal comes in before we add the new process to
1246     * it's process group.
1247     * A fatal signal pending means that current will exit, so the new
1248     * thread can't slip out of an OOM kill (or normal SIGKILL).
1249      */
1250    recalc_sigpending();
1251    if (signal_pending(current)) {
1252        spin_unlock(&current->sighand->siglock);
1253        write_unlock_irq(&tasklist_lock);
1254        retval = -ERESTARTNOINTR;
1255        goto bad_fork_free_pid;
1256    }
1257
1258    if (clone_flags & CLONE_THREAD) {
1259        current->signal->nr_threads++;
1260        atomic_inc(&current->signal->live);
1261        atomic_inc(&current->signal->sigcnt);
1262        p->group_leader = current->group_leader;
1263        list_add_tail_rcu(&p->thread_group, &p->group_leader->thread_group);
1264    }
1265
1266    if (likely(p->pid)) {
1267        tracehook_finish_clone(p, clone_flags, trace);
1268
1269        if (thread_group_leader(p)) {
1270            if (clone_flags & CLONE_NEWPID)
1271                p->nsproxy->pid_ns->child_reaper = p;
1272
1273            p->signal->leader_pid = pid;
1274            p->signal->tty = tty_kref_get(current->signal->tty);
1275            attach_pid(p, PIDTYPE_PGID, task_pgrp(current));
1276            attach_pid(p, PIDTYPE_SID, task_session(current));
1277            list_add_tail(&p->sibling, &p->real_parent->children);
1278            list_add_tail_rcu(&p->tasks, &init_task.tasks);
1279            __get_cpu_var(process_counts)++;
1280        }
1281        attach_pid(p, PIDTYPE_PID, pid);
1282        nr_threads++;
1283    }
1284
1285    total_forks++;
1286    spin_unlock(&current->sighand->siglock);
1287    write_unlock_irq(&tasklist_lock);
1288    proc_fork_connector(p);
1289    cgroup_post_fork(p);
1290    perf_event_fork(p);
1291    return p;
1292
1293bad_fork_free_pid:
1294    if (pid != &init_struct_pid)
1295        free_pid(pid);
1296bad_fork_cleanup_io:
1297    if (p->io_context)
1298        exit_io_context(p);
1299bad_fork_cleanup_namespaces:
1300    exit_task_namespaces(p);
1301bad_fork_cleanup_mm:
1302    if (p->mm)
1303        mmput(p->mm);
1304bad_fork_cleanup_signal:
1305    if (!(clone_flags & CLONE_THREAD))
1306        free_signal_struct(p->signal);
1307bad_fork_cleanup_sighand:
1308    __cleanup_sighand(p->sighand);
1309bad_fork_cleanup_fs:
1310    exit_fs(p); /* blocking */
1311bad_fork_cleanup_files:
1312    exit_files(p); /* blocking */
1313bad_fork_cleanup_semundo:
1314    exit_sem(p);
1315bad_fork_cleanup_audit:
1316    audit_free(p);
1317bad_fork_cleanup_policy:
1318    perf_event_free_task(p);
1319#ifdef CONFIG_NUMA
1320    mpol_put(p->mempolicy);
1321bad_fork_cleanup_cgroup:
1322#endif
1323    cgroup_exit(p, cgroup_callbacks_done);
1324    delayacct_tsk_free(p);
1325    module_put(task_thread_info(p)->exec_domain->module);
1326bad_fork_cleanup_count:
1327    atomic_dec(&p->cred->user->processes);
1328    exit_creds(p);
1329bad_fork_free:
1330    free_task(p);
1331fork_out:
1332    return ERR_PTR(retval);
1333}
1334
1335noinline struct pt_regs * __cpuinit __attribute__((weak)) idle_regs(struct pt_regs *regs)
1336{
1337    memset(regs, 0, sizeof(struct pt_regs));
1338    return regs;
1339}
1340
1341static inline void init_idle_pids(struct pid_link *links)
1342{
1343    enum pid_type type;
1344
1345    for (type = PIDTYPE_PID; type < PIDTYPE_MAX; ++type) {
1346        INIT_HLIST_NODE(&links[type].node); /* not really needed */
1347        links[type].pid = &init_struct_pid;
1348    }
1349}
1350
1351struct task_struct * __cpuinit fork_idle(int cpu)
1352{
1353    struct task_struct *task;
1354    struct pt_regs regs;
1355
1356    task = copy_process(CLONE_VM, 0, idle_regs(&regs), 0, NULL,
1357                &init_struct_pid, 0);
1358    if (!IS_ERR(task)) {
1359        init_idle_pids(task->pids);
1360        init_idle(task, cpu);
1361    }
1362
1363    return task;
1364}
1365
1366/*
1367 * Ok, this is the main fork-routine.
1368 *
1369 * It copies the process, and if successful kick-starts
1370 * it and waits for it to finish using the VM if required.
1371 */
1372long do_fork(unsigned long clone_flags,
1373          unsigned long stack_start,
1374          struct pt_regs *regs,
1375          unsigned long stack_size,
1376          int __user *parent_tidptr,
1377          int __user *child_tidptr)
1378{
1379    struct task_struct *p;
1380    int trace = 0;
1381    long nr;
1382
1383    /*
1384     * Do some preliminary argument and permissions checking before we
1385     * actually start allocating stuff
1386     */
1387    if (clone_flags & CLONE_NEWUSER) {
1388        if (clone_flags & CLONE_THREAD)
1389            return -EINVAL;
1390        /* hopefully this check will go away when userns support is
1391         * complete
1392         */
1393        if (!capable(CAP_SYS_ADMIN) || !capable(CAP_SETUID) ||
1394                !capable(CAP_SETGID))
1395            return -EPERM;
1396    }
1397
1398    /*
1399     * We hope to recycle these flags after 2.6.26
1400     */
1401    if (unlikely(clone_flags & CLONE_STOPPED)) {
1402        static int __read_mostly count = 100;
1403
1404        if (count > 0 && printk_ratelimit()) {
1405            char comm[TASK_COMM_LEN];
1406
1407            count--;
1408            printk(KERN_INFO "fork(): process `%s' used deprecated "
1409                    "clone flags 0x%lx\n",
1410                get_task_comm(comm, current),
1411                clone_flags & CLONE_STOPPED);
1412        }
1413    }
1414
1415    /*
1416     * When called from kernel_thread, don't do user tracing stuff.
1417     */
1418    if (likely(user_mode(regs)))
1419        trace = tracehook_prepare_clone(clone_flags);
1420
1421    p = copy_process(clone_flags, stack_start, regs, stack_size,
1422             child_tidptr, NULL, trace);
1423    /*
1424     * Do this prior waking up the new thread - the thread pointer
1425     * might get invalid after that point, if the thread exits quickly.
1426     */
1427    if (!IS_ERR(p)) {
1428        struct completion vfork;
1429
1430        trace_sched_process_fork(current, p);
1431
1432        nr = task_pid_vnr(p);
1433
1434        if (clone_flags & CLONE_PARENT_SETTID)
1435            put_user(nr, parent_tidptr);
1436
1437        if (clone_flags & CLONE_VFORK) {
1438            p->vfork_done = &vfork;
1439            init_completion(&vfork);
1440        }
1441
1442        audit_finish_fork(p);
1443        tracehook_report_clone(regs, clone_flags, nr, p);
1444
1445        /*
1446         * We set PF_STARTING at creation in case tracing wants to
1447         * use this to distinguish a fully live task from one that
1448         * hasn't gotten to tracehook_report_clone() yet. Now we
1449         * clear it and set the child going.
1450         */
1451        p->flags &= ~PF_STARTING;
1452
1453        if (unlikely(clone_flags & CLONE_STOPPED)) {
1454            /*
1455             * We'll start up with an immediate SIGSTOP.
1456             */
1457            sigaddset(&p->pending.signal, SIGSTOP);
1458            set_tsk_thread_flag(p, TIF_SIGPENDING);
1459            __set_task_state(p, TASK_STOPPED);
1460        } else {
1461            wake_up_new_task(p, clone_flags);
1462        }
1463
1464        tracehook_report_clone_complete(trace, regs,
1465                        clone_flags, nr, p);
1466
1467        if (clone_flags & CLONE_VFORK) {
1468            freezer_do_not_count();
1469            wait_for_completion(&vfork);
1470            freezer_count();
1471            tracehook_report_vfork_done(p, nr);
1472        }
1473    } else {
1474        nr = PTR_ERR(p);
1475    }
1476    return nr;
1477}
1478
1479#ifndef ARCH_MIN_MMSTRUCT_ALIGN
1480#define ARCH_MIN_MMSTRUCT_ALIGN 0
1481#endif
1482
1483static void sighand_ctor(void *data)
1484{
1485    struct sighand_struct *sighand = data;
1486
1487    spin_lock_init(&sighand->siglock);
1488    init_waitqueue_head(&sighand->signalfd_wqh);
1489}
1490
1491void __init proc_caches_init(void)
1492{
1493    sighand_cachep = kmem_cache_create("sighand_cache",
1494            sizeof(struct sighand_struct), 0,
1495            SLAB_HWCACHE_ALIGN|SLAB_PANIC|SLAB_DESTROY_BY_RCU|
1496            SLAB_NOTRACK, sighand_ctor);
1497    signal_cachep = kmem_cache_create("signal_cache",
1498            sizeof(struct signal_struct), 0,
1499            SLAB_HWCACHE_ALIGN|SLAB_PANIC|SLAB_NOTRACK, NULL);
1500    files_cachep = kmem_cache_create("files_cache",
1501            sizeof(struct files_struct), 0,
1502            SLAB_HWCACHE_ALIGN|SLAB_PANIC|SLAB_NOTRACK, NULL);
1503    fs_cachep = kmem_cache_create("fs_cache",
1504            sizeof(struct fs_struct), 0,
1505            SLAB_HWCACHE_ALIGN|SLAB_PANIC|SLAB_NOTRACK, NULL);
1506    mm_cachep = kmem_cache_create("mm_struct",
1507            sizeof(struct mm_struct), ARCH_MIN_MMSTRUCT_ALIGN,
1508            SLAB_HWCACHE_ALIGN|SLAB_PANIC|SLAB_NOTRACK, NULL);
1509    vm_area_cachep = KMEM_CACHE(vm_area_struct, SLAB_PANIC);
1510    mmap_init();
1511}
1512
1513/*
1514 * Check constraints on flags passed to the unshare system call and
1515 * force unsharing of additional process context as appropriate.
1516 */
1517static void check_unshare_flags(unsigned long *flags_ptr)
1518{
1519    /*
1520     * If unsharing a thread from a thread group, must also
1521     * unshare vm.
1522     */
1523    if (*flags_ptr & CLONE_THREAD)
1524        *flags_ptr |= CLONE_VM;
1525
1526    /*
1527     * If unsharing vm, must also unshare signal handlers.
1528     */
1529    if (*flags_ptr & CLONE_VM)
1530        *flags_ptr |= CLONE_SIGHAND;
1531
1532    /*
1533     * If unsharing namespace, must also unshare filesystem information.
1534     */
1535    if (*flags_ptr & CLONE_NEWNS)
1536        *flags_ptr |= CLONE_FS;
1537}
1538
1539/*
1540 * Unsharing of tasks created with CLONE_THREAD is not supported yet
1541 */
1542static int unshare_thread(unsigned long unshare_flags)
1543{
1544    if (unshare_flags & CLONE_THREAD)
1545        return -EINVAL;
1546
1547    return 0;
1548}
1549
1550/*
1551 * Unshare the filesystem structure if it is being shared
1552 */
1553static int unshare_fs(unsigned long unshare_flags, struct fs_struct **new_fsp)
1554{
1555    struct fs_struct *fs = current->fs;
1556
1557    if (!(unshare_flags & CLONE_FS) || !fs)
1558        return 0;
1559
1560    /* don't need lock here; in the worst case we'll do useless copy */
1561    if (fs->users == 1)
1562        return 0;
1563
1564    *new_fsp = copy_fs_struct(fs);
1565    if (!*new_fsp)
1566        return -ENOMEM;
1567
1568    return 0;
1569}
1570
1571/*
1572 * Unsharing of sighand is not supported yet
1573 */
1574static int unshare_sighand(unsigned long unshare_flags, struct sighand_struct **new_sighp)
1575{
1576    struct sighand_struct *sigh = current->sighand;
1577
1578    if ((unshare_flags & CLONE_SIGHAND) && atomic_read(&sigh->count) > 1)
1579        return -EINVAL;
1580    else
1581        return 0;
1582}
1583
1584/*
1585 * Unshare vm if it is being shared
1586 */
1587static int unshare_vm(unsigned long unshare_flags, struct mm_struct **new_mmp)
1588{
1589    struct mm_struct *mm = current->mm;
1590
1591    if ((unshare_flags & CLONE_VM) &&
1592        (mm && atomic_read(&mm->mm_users) > 1)) {
1593        return -EINVAL;
1594    }
1595
1596    return 0;
1597}
1598
1599/*
1600 * Unshare file descriptor table if it is being shared
1601 */
1602static int unshare_fd(unsigned long unshare_flags, struct files_struct **new_fdp)
1603{
1604    struct files_struct *fd = current->files;
1605    int error = 0;
1606
1607    if ((unshare_flags & CLONE_FILES) &&
1608        (fd && atomic_read(&fd->count) > 1)) {
1609        *new_fdp = dup_fd(fd, &error);
1610        if (!*new_fdp)
1611            return error;
1612    }
1613
1614    return 0;
1615}
1616
1617/*
1618 * unshare allows a process to 'unshare' part of the process
1619 * context which was originally shared using clone. copy_*
1620 * functions used by do_fork() cannot be used here directly
1621 * because they modify an inactive task_struct that is being
1622 * constructed. Here we are modifying the current, active,
1623 * task_struct.
1624 */
1625SYSCALL_DEFINE1(unshare, unsigned long, unshare_flags)
1626{
1627    int err = 0;
1628    struct fs_struct *fs, *new_fs = NULL;
1629    struct sighand_struct *new_sigh = NULL;
1630    struct mm_struct *mm, *new_mm = NULL, *active_mm = NULL;
1631    struct files_struct *fd, *new_fd = NULL;
1632    struct nsproxy *new_nsproxy = NULL;
1633    int do_sysvsem = 0;
1634
1635    check_unshare_flags(&unshare_flags);
1636
1637    /* Return -EINVAL for all unsupported flags */
1638    err = -EINVAL;
1639    if (unshare_flags & ~(CLONE_THREAD|CLONE_FS|CLONE_NEWNS|CLONE_SIGHAND|
1640                CLONE_VM|CLONE_FILES|CLONE_SYSVSEM|
1641                CLONE_NEWUTS|CLONE_NEWIPC|CLONE_NEWNET))
1642        goto bad_unshare_out;
1643
1644    /*
1645     * CLONE_NEWIPC must also detach from the undolist: after switching
1646     * to a new ipc namespace, the semaphore arrays from the old
1647     * namespace are unreachable.
1648     */
1649    if (unshare_flags & (CLONE_NEWIPC|CLONE_SYSVSEM))
1650        do_sysvsem = 1;
1651    if ((err = unshare_thread(unshare_flags)))
1652        goto bad_unshare_out;
1653    if ((err = unshare_fs(unshare_flags, &new_fs)))
1654        goto bad_unshare_cleanup_thread;
1655    if ((err = unshare_sighand(unshare_flags, &new_sigh)))
1656        goto bad_unshare_cleanup_fs;
1657    if ((err = unshare_vm(unshare_flags, &new_mm)))
1658        goto bad_unshare_cleanup_sigh;
1659    if ((err = unshare_fd(unshare_flags, &new_fd)))
1660        goto bad_unshare_cleanup_vm;
1661    if ((err = unshare_nsproxy_namespaces(unshare_flags, &new_nsproxy,
1662            new_fs)))
1663        goto bad_unshare_cleanup_fd;
1664
1665    if (new_fs || new_mm || new_fd || do_sysvsem || new_nsproxy) {
1666        if (do_sysvsem) {
1667            /*
1668             * CLONE_SYSVSEM is equivalent to sys_exit().
1669             */
1670            exit_sem(current);
1671        }
1672
1673        if (new_nsproxy) {
1674            switch_task_namespaces(current, new_nsproxy);
1675            new_nsproxy = NULL;
1676        }
1677
1678        task_lock(current);
1679
1680        if (new_fs) {
1681            fs = current->fs;
1682            spin_lock(&fs->lock);
1683            current->fs = new_fs;
1684            if (--fs->users)
1685                new_fs = NULL;
1686            else
1687                new_fs = fs;
1688            spin_unlock(&fs->lock);
1689        }
1690
1691        if (new_mm) {
1692            mm = current->mm;
1693            active_mm = current->active_mm;
1694            current->mm = new_mm;
1695            current->active_mm = new_mm;
1696            activate_mm(active_mm, new_mm);
1697            new_mm = mm;
1698        }
1699
1700        if (new_fd) {
1701            fd = current->files;
1702            current->files = new_fd;
1703            new_fd = fd;
1704        }
1705
1706        task_unlock(current);
1707    }
1708
1709    if (new_nsproxy)
1710        put_nsproxy(new_nsproxy);
1711
1712bad_unshare_cleanup_fd:
1713    if (new_fd)
1714        put_files_struct(new_fd);
1715
1716bad_unshare_cleanup_vm:
1717    if (new_mm)
1718        mmput(new_mm);
1719
1720bad_unshare_cleanup_sigh:
1721    if (new_sigh)
1722        if (atomic_dec_and_test(&new_sigh->count))
1723            kmem_cache_free(sighand_cachep, new_sigh);
1724
1725bad_unshare_cleanup_fs:
1726    if (new_fs)
1727        free_fs_struct(new_fs);
1728
1729bad_unshare_cleanup_thread:
1730bad_unshare_out:
1731    return err;
1732}
1733
1734/*
1735 * Helper to unshare the files of the current task.
1736 * We don't want to expose copy_files internals to
1737 * the exec layer of the kernel.
1738 */
1739
1740int unshare_files(struct files_struct **displaced)
1741{
1742    struct task_struct *task = current;
1743    struct files_struct *copy = NULL;
1744    int error;
1745
1746    error = unshare_fd(CLONE_FILES, &copy);
1747    if (error || !copy) {
1748        *displaced = NULL;
1749        return error;
1750    }
1751    *displaced = task->files;
1752    task_lock(task);
1753    task->files = copy;
1754    task_unlock(task);
1755    return 0;
1756}
1757

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