linux/kernel/fork.c
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   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/futex.h>
  41#include <linux/compat.h>
  42#include <linux/kthread.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/blkdev.h>
  62#include <linux/fs_struct.h>
  63#include <linux/magic.h>
  64#include <linux/perf_event.h>
  65#include <linux/posix-timers.h>
  66#include <linux/user-return-notifier.h>
  67#include <linux/oom.h>
  68#include <linux/khugepaged.h>
  69
  70#include <asm/pgtable.h>
  71#include <asm/pgalloc.h>
  72#include <asm/uaccess.h>
  73#include <asm/mmu_context.h>
  74#include <asm/cacheflush.h>
  75#include <asm/tlbflush.h>
  76
  77#include <trace/events/sched.h>
  78
  79/*
  80 * Protected counters by write_lock_irq(&tasklist_lock)
  81 */
  82unsigned long total_forks;      /* Handle normal Linux uptimes. */
  83int nr_threads;                 /* The idle threads do not count.. */
  84
  85int max_threads;                /* tunable limit on nr_threads */
  86
  87DEFINE_PER_CPU(unsigned long, process_counts) = 0;
  88
  89__cacheline_aligned DEFINE_RWLOCK(tasklist_lock);  /* outer */
  90
  91#ifdef CONFIG_PROVE_RCU
  92int lockdep_tasklist_lock_is_held(void)
  93{
  94        return lockdep_is_held(&tasklist_lock);
  95}
  96EXPORT_SYMBOL_GPL(lockdep_tasklist_lock_is_held);
  97#endif /* #ifdef CONFIG_PROVE_RCU */
  98
  99int nr_processes(void)
 100{
 101        int cpu;
 102        int total = 0;
 103
 104        for_each_possible_cpu(cpu)
 105                total += per_cpu(process_counts, cpu);
 106
 107        return total;
 108}
 109
 110#ifndef __HAVE_ARCH_TASK_STRUCT_ALLOCATOR
 111# define alloc_task_struct_node(node)           \
 112                kmem_cache_alloc_node(task_struct_cachep, GFP_KERNEL, node)
 113# define free_task_struct(tsk)                  \
 114                kmem_cache_free(task_struct_cachep, (tsk))
 115static struct kmem_cache *task_struct_cachep;
 116#endif
 117
 118#ifndef __HAVE_ARCH_THREAD_INFO_ALLOCATOR
 119static struct thread_info *alloc_thread_info_node(struct task_struct *tsk,
 120                                                  int node)
 121{
 122#ifdef CONFIG_DEBUG_STACK_USAGE
 123        gfp_t mask = GFP_KERNEL | __GFP_ZERO;
 124#else
 125        gfp_t mask = GFP_KERNEL;
 126#endif
 127        struct page *page = alloc_pages_node(node, mask, THREAD_SIZE_ORDER);
 128
 129        return page ? page_address(page) : NULL;
 130}
 131
 132static inline void free_thread_info(struct thread_info *ti)
 133{
 134        free_pages((unsigned long)ti, THREAD_SIZE_ORDER);
 135}
 136#endif
 137
 138/* SLAB cache for signal_struct structures (tsk->signal) */
 139static struct kmem_cache *signal_cachep;
 140
 141/* SLAB cache for sighand_struct structures (tsk->sighand) */
 142struct kmem_cache *sighand_cachep;
 143
 144/* SLAB cache for files_struct structures (tsk->files) */
 145struct kmem_cache *files_cachep;
 146
 147/* SLAB cache for fs_struct structures (tsk->fs) */
 148struct kmem_cache *fs_cachep;
 149
 150/* SLAB cache for vm_area_struct structures */
 151struct kmem_cache *vm_area_cachep;
 152
 153/* SLAB cache for mm_struct structures (tsk->mm) */
 154static struct kmem_cache *mm_cachep;
 155
 156static void account_kernel_stack(struct thread_info *ti, int account)
 157{
 158        struct zone *zone = page_zone(virt_to_page(ti));
 159
 160        mod_zone_page_state(zone, NR_KERNEL_STACK, account);
 161}
 162
 163void free_task(struct task_struct *tsk)
 164{
 165        prop_local_destroy_single(&tsk->dirties);
 166        account_kernel_stack(tsk->stack, -1);
 167        free_thread_info(tsk->stack);
 168        rt_mutex_debug_task_free(tsk);
 169        ftrace_graph_exit_task(tsk);
 170        free_task_struct(tsk);
 171}
 172EXPORT_SYMBOL(free_task);
 173
 174static inline void free_signal_struct(struct signal_struct *sig)
 175{
 176        taskstats_tgid_free(sig);
 177        sched_autogroup_exit(sig);
 178        kmem_cache_free(signal_cachep, sig);
 179}
 180
 181static inline void put_signal_struct(struct signal_struct *sig)
 182{
 183        if (atomic_dec_and_test(&sig->sigcnt))
 184                free_signal_struct(sig);
 185}
 186
 187void __put_task_struct(struct task_struct *tsk)
 188{
 189        WARN_ON(!tsk->exit_state);
 190        WARN_ON(atomic_read(&tsk->usage));
 191        WARN_ON(tsk == current);
 192
 193        exit_creds(tsk);
 194        delayacct_tsk_free(tsk);
 195        put_signal_struct(tsk->signal);
 196
 197        if (!profile_handoff_task(tsk))
 198                free_task(tsk);
 199}
 200EXPORT_SYMBOL_GPL(__put_task_struct);
 201
 202/*
 203 * macro override instead of weak attribute alias, to workaround
 204 * gcc 4.1.0 and 4.1.1 bugs with weak attribute and empty functions.
 205 */
 206#ifndef arch_task_cache_init
 207#define arch_task_cache_init()
 208#endif
 209
 210void __init fork_init(unsigned long mempages)
 211{
 212#ifndef __HAVE_ARCH_TASK_STRUCT_ALLOCATOR
 213#ifndef ARCH_MIN_TASKALIGN
 214#define ARCH_MIN_TASKALIGN      L1_CACHE_BYTES
 215#endif
 216        /* create a slab on which task_structs can be allocated */
 217        task_struct_cachep =
 218                kmem_cache_create("task_struct", sizeof(struct task_struct),
 219                        ARCH_MIN_TASKALIGN, SLAB_PANIC | SLAB_NOTRACK, NULL);
 220#endif
 221
 222        /* do the arch specific task caches init */
 223        arch_task_cache_init();
 224
 225        /*
 226         * The default maximum number of threads is set to a safe
 227         * value: the thread structures can take up at most half
 228         * of memory.
 229         */
 230        max_threads = mempages / (8 * THREAD_SIZE / PAGE_SIZE);
 231
 232        /*
 233         * we need to allow at least 20 threads to boot a system
 234         */
 235        if (max_threads < 20)
 236                max_threads = 20;
 237
 238        init_task.signal->rlim[RLIMIT_NPROC].rlim_cur = max_threads/2;
 239        init_task.signal->rlim[RLIMIT_NPROC].rlim_max = max_threads/2;
 240        init_task.signal->rlim[RLIMIT_SIGPENDING] =
 241                init_task.signal->rlim[RLIMIT_NPROC];
 242}
 243
 244int __attribute__((weak)) arch_dup_task_struct(struct task_struct *dst,
 245                                               struct task_struct *src)
 246{
 247        *dst = *src;
 248        return 0;
 249}
 250
 251static struct task_struct *dup_task_struct(struct task_struct *orig)
 252{
 253        struct task_struct *tsk;
 254        struct thread_info *ti;
 255        unsigned long *stackend;
 256        int node = tsk_fork_get_node(orig);
 257        int err;
 258
 259        prepare_to_copy(orig);
 260
 261        tsk = alloc_task_struct_node(node);
 262        if (!tsk)
 263                return NULL;
 264
 265        ti = alloc_thread_info_node(tsk, node);
 266        if (!ti) {
 267                free_task_struct(tsk);
 268                return NULL;
 269        }
 270
 271        err = arch_dup_task_struct(tsk, orig);
 272        if (err)
 273                goto out;
 274
 275        tsk->stack = ti;
 276
 277        err = prop_local_init_single(&tsk->dirties);
 278        if (err)
 279                goto out;
 280
 281        setup_thread_stack(tsk, orig);
 282        clear_user_return_notifier(tsk);
 283        clear_tsk_need_resched(tsk);
 284        stackend = end_of_stack(tsk);
 285        *stackend = STACK_END_MAGIC;    /* for overflow detection */
 286
 287#ifdef CONFIG_CC_STACKPROTECTOR
 288        tsk->stack_canary = get_random_int();
 289#endif
 290
 291        /*
 292         * One for us, one for whoever does the "release_task()" (usually
 293         * parent)
 294         */
 295        atomic_set(&tsk->usage, 2);
 296#ifdef CONFIG_BLK_DEV_IO_TRACE
 297        tsk->btrace_seq = 0;
 298#endif
 299        tsk->splice_pipe = NULL;
 300
 301        account_kernel_stack(ti, 1);
 302
 303        return tsk;
 304
 305out:
 306        free_thread_info(ti);
 307        free_task_struct(tsk);
 308        return NULL;
 309}
 310
 311#ifdef CONFIG_MMU
 312static int dup_mmap(struct mm_struct *mm, struct mm_struct *oldmm)
 313{
 314        struct vm_area_struct *mpnt, *tmp, *prev, **pprev;
 315        struct rb_node **rb_link, *rb_parent;
 316        int retval;
 317        unsigned long charge;
 318        struct mempolicy *pol;
 319
 320        down_write(&oldmm->mmap_sem);
 321        flush_cache_dup_mm(oldmm);
 322        /*
 323         * Not linked in yet - no deadlock potential:
 324         */
 325        down_write_nested(&mm->mmap_sem, SINGLE_DEPTH_NESTING);
 326
 327        mm->locked_vm = 0;
 328        mm->mmap = NULL;
 329        mm->mmap_cache = NULL;
 330        mm->free_area_cache = oldmm->mmap_base;
 331        mm->cached_hole_size = ~0UL;
 332        mm->map_count = 0;
 333        cpumask_clear(mm_cpumask(mm));
 334        mm->mm_rb = RB_ROOT;
 335        rb_link = &mm->mm_rb.rb_node;
 336        rb_parent = NULL;
 337        pprev = &mm->mmap;
 338        retval = ksm_fork(mm, oldmm);
 339        if (retval)
 340                goto out;
 341        retval = khugepaged_fork(mm, oldmm);
 342        if (retval)
 343                goto out;
 344
 345        prev = NULL;
 346        for (mpnt = oldmm->mmap; mpnt; mpnt = mpnt->vm_next) {
 347                struct file *file;
 348
 349                if (mpnt->vm_flags & VM_DONTCOPY) {
 350                        long pages = vma_pages(mpnt);
 351                        mm->total_vm -= pages;
 352                        vm_stat_account(mm, mpnt->vm_flags, mpnt->vm_file,
 353                                                                -pages);
 354                        continue;
 355                }
 356                charge = 0;
 357                if (mpnt->vm_flags & VM_ACCOUNT) {
 358                        unsigned int len = (mpnt->vm_end - mpnt->vm_start) >> PAGE_SHIFT;
 359                        if (security_vm_enough_memory(len))
 360                                goto fail_nomem;
 361                        charge = len;
 362                }
 363                tmp = kmem_cache_alloc(vm_area_cachep, GFP_KERNEL);
 364                if (!tmp)
 365                        goto fail_nomem;
 366                *tmp = *mpnt;
 367                INIT_LIST_HEAD(&tmp->anon_vma_chain);
 368                pol = mpol_dup(vma_policy(mpnt));
 369                retval = PTR_ERR(pol);
 370                if (IS_ERR(pol))
 371                        goto fail_nomem_policy;
 372                vma_set_policy(tmp, pol);
 373                tmp->vm_mm = mm;
 374                if (anon_vma_fork(tmp, mpnt))
 375                        goto fail_nomem_anon_vma_fork;
 376                tmp->vm_flags &= ~VM_LOCKED;
 377                tmp->vm_next = tmp->vm_prev = NULL;
 378                file = tmp->vm_file;
 379                if (file) {
 380                        struct inode *inode = file->f_path.dentry->d_inode;
 381                        struct address_space *mapping = file->f_mapping;
 382
 383                        get_file(file);
 384                        if (tmp->vm_flags & VM_DENYWRITE)
 385                                atomic_dec(&inode->i_writecount);
 386                        mutex_lock(&mapping->i_mmap_mutex);
 387                        if (tmp->vm_flags & VM_SHARED)
 388                                mapping->i_mmap_writable++;
 389                        flush_dcache_mmap_lock(mapping);
 390                        /* insert tmp into the share list, just after mpnt */
 391                        vma_prio_tree_add(tmp, mpnt);
 392                        flush_dcache_mmap_unlock(mapping);
 393                        mutex_unlock(&mapping->i_mmap_mutex);
 394                }
 395
 396                /*
 397                 * Clear hugetlb-related page reserves for children. This only
 398                 * affects MAP_PRIVATE mappings. Faults generated by the child
 399                 * are not guaranteed to succeed, even if read-only
 400                 */
 401                if (is_vm_hugetlb_page(tmp))
 402                        reset_vma_resv_huge_pages(tmp);
 403
 404                /*
 405                 * Link in the new vma and copy the page table entries.
 406                 */
 407                *pprev = tmp;
 408                pprev = &tmp->vm_next;
 409                tmp->vm_prev = prev;
 410                prev = tmp;
 411
 412                __vma_link_rb(mm, tmp, rb_link, rb_parent);
 413                rb_link = &tmp->vm_rb.rb_right;
 414                rb_parent = &tmp->vm_rb;
 415
 416                mm->map_count++;
 417                retval = copy_page_range(mm, oldmm, mpnt);
 418
 419                if (tmp->vm_ops && tmp->vm_ops->open)
 420                        tmp->vm_ops->open(tmp);
 421
 422                if (retval)
 423                        goto out;
 424        }
 425        /* a new mm has just been created */
 426        arch_dup_mmap(oldmm, mm);
 427        retval = 0;
 428out:
 429        up_write(&mm->mmap_sem);
 430        flush_tlb_mm(oldmm);
 431        up_write(&oldmm->mmap_sem);
 432        return retval;
 433fail_nomem_anon_vma_fork:
 434        mpol_put(pol);
 435fail_nomem_policy:
 436        kmem_cache_free(vm_area_cachep, tmp);
 437fail_nomem:
 438        retval = -ENOMEM;
 439        vm_unacct_memory(charge);
 440        goto out;
 441}
 442
 443static inline int mm_alloc_pgd(struct mm_struct *mm)
 444{
 445        mm->pgd = pgd_alloc(mm);
 446        if (unlikely(!mm->pgd))
 447                return -ENOMEM;
 448        return 0;
 449}
 450
 451static inline void mm_free_pgd(struct mm_struct *mm)
 452{
 453        pgd_free(mm, mm->pgd);
 454}
 455#else
 456#define dup_mmap(mm, oldmm)     (0)
 457#define mm_alloc_pgd(mm)        (0)
 458#define mm_free_pgd(mm)
 459#endif /* CONFIG_MMU */
 460
 461__cacheline_aligned_in_smp DEFINE_SPINLOCK(mmlist_lock);
 462
 463#define allocate_mm()   (kmem_cache_alloc(mm_cachep, GFP_KERNEL))
 464#define free_mm(mm)     (kmem_cache_free(mm_cachep, (mm)))
 465
 466static unsigned long default_dump_filter = MMF_DUMP_FILTER_DEFAULT;
 467
 468static int __init coredump_filter_setup(char *s)
 469{
 470        default_dump_filter =
 471                (simple_strtoul(s, NULL, 0) << MMF_DUMP_FILTER_SHIFT) &
 472                MMF_DUMP_FILTER_MASK;
 473        return 1;
 474}
 475
 476__setup("coredump_filter=", coredump_filter_setup);
 477
 478#include <linux/init_task.h>
 479
 480static void mm_init_aio(struct mm_struct *mm)
 481{
 482#ifdef CONFIG_AIO
 483        spin_lock_init(&mm->ioctx_lock);
 484        INIT_HLIST_HEAD(&mm->ioctx_list);
 485#endif
 486}
 487
 488static struct mm_struct *mm_init(struct mm_struct *mm, struct task_struct *p)
 489{
 490        atomic_set(&mm->mm_users, 1);
 491        atomic_set(&mm->mm_count, 1);
 492        init_rwsem(&mm->mmap_sem);
 493        INIT_LIST_HEAD(&mm->mmlist);
 494        mm->flags = (current->mm) ?
 495                (current->mm->flags & MMF_INIT_MASK) : default_dump_filter;
 496        mm->core_state = NULL;
 497        mm->nr_ptes = 0;
 498        memset(&mm->rss_stat, 0, sizeof(mm->rss_stat));
 499        spin_lock_init(&mm->page_table_lock);
 500        mm->free_area_cache = TASK_UNMAPPED_BASE;
 501        mm->cached_hole_size = ~0UL;
 502        mm_init_aio(mm);
 503        mm_init_owner(mm, p);
 504        atomic_set(&mm->oom_disable_count, 0);
 505
 506        if (likely(!mm_alloc_pgd(mm))) {
 507                mm->def_flags = 0;
 508                mmu_notifier_mm_init(mm);
 509                return mm;
 510        }
 511
 512        free_mm(mm);
 513        return NULL;
 514}
 515
 516/*
 517 * Allocate and initialize an mm_struct.
 518 */
 519struct mm_struct *mm_alloc(void)
 520{
 521        struct mm_struct *mm;
 522
 523        mm = allocate_mm();
 524        if (!mm)
 525                return NULL;
 526
 527        memset(mm, 0, sizeof(*mm));
 528        mm_init_cpumask(mm);
 529        return mm_init(mm, current);
 530}
 531
 532/*
 533 * Called when the last reference to the mm
 534 * is dropped: either by a lazy thread or by
 535 * mmput. Free the page directory and the mm.
 536 */
 537void __mmdrop(struct mm_struct *mm)
 538{
 539        BUG_ON(mm == &init_mm);
 540        mm_free_pgd(mm);
 541        destroy_context(mm);
 542        mmu_notifier_mm_destroy(mm);
 543#ifdef CONFIG_TRANSPARENT_HUGEPAGE
 544        VM_BUG_ON(mm->pmd_huge_pte);
 545#endif
 546        free_mm(mm);
 547}
 548EXPORT_SYMBOL_GPL(__mmdrop);
 549
 550/*
 551 * Decrement the use count and release all resources for an mm.
 552 */
 553void mmput(struct mm_struct *mm)
 554{
 555        might_sleep();
 556
 557        if (atomic_dec_and_test(&mm->mm_users)) {
 558                exit_aio(mm);
 559                ksm_exit(mm);
 560                khugepaged_exit(mm); /* must run before exit_mmap */
 561                exit_mmap(mm);
 562                set_mm_exe_file(mm, NULL);
 563                if (!list_empty(&mm->mmlist)) {
 564                        spin_lock(&mmlist_lock);
 565                        list_del(&mm->mmlist);
 566                        spin_unlock(&mmlist_lock);
 567                }
 568                put_swap_token(mm);
 569                if (mm->binfmt)
 570                        module_put(mm->binfmt->module);
 571                mmdrop(mm);
 572        }
 573}
 574EXPORT_SYMBOL_GPL(mmput);
 575
 576/*
 577 * We added or removed a vma mapping the executable. The vmas are only mapped
 578 * during exec and are not mapped with the mmap system call.
 579 * Callers must hold down_write() on the mm's mmap_sem for these
 580 */
 581void added_exe_file_vma(struct mm_struct *mm)
 582{
 583        mm->num_exe_file_vmas++;
 584}
 585
 586void removed_exe_file_vma(struct mm_struct *mm)
 587{
 588        mm->num_exe_file_vmas--;
 589        if ((mm->num_exe_file_vmas == 0) && mm->exe_file) {
 590                fput(mm->exe_file);
 591                mm->exe_file = NULL;
 592        }
 593
 594}
 595
 596void set_mm_exe_file(struct mm_struct *mm, struct file *new_exe_file)
 597{
 598        if (new_exe_file)
 599                get_file(new_exe_file);
 600        if (mm->exe_file)
 601                fput(mm->exe_file);
 602        mm->exe_file = new_exe_file;
 603        mm->num_exe_file_vmas = 0;
 604}
 605
 606struct file *get_mm_exe_file(struct mm_struct *mm)
 607{
 608        struct file *exe_file;
 609
 610        /* We need mmap_sem to protect against races with removal of
 611         * VM_EXECUTABLE vmas */
 612        down_read(&mm->mmap_sem);
 613        exe_file = mm->exe_file;
 614        if (exe_file)
 615                get_file(exe_file);
 616        up_read(&mm->mmap_sem);
 617        return exe_file;
 618}
 619
 620static void dup_mm_exe_file(struct mm_struct *oldmm, struct mm_struct *newmm)
 621{
 622        /* It's safe to write the exe_file pointer without exe_file_lock because
 623         * this is called during fork when the task is not yet in /proc */
 624        newmm->exe_file = get_mm_exe_file(oldmm);
 625}
 626
 627/**
 628 * get_task_mm - acquire a reference to the task's mm
 629 *
 630 * Returns %NULL if the task has no mm.  Checks PF_KTHREAD (meaning
 631 * this kernel workthread has transiently adopted a user mm with use_mm,
 632 * to do its AIO) is not set and if so returns a reference to it, after
 633 * bumping up the use count.  User must release the mm via mmput()
 634 * after use.  Typically used by /proc and ptrace.
 635 */
 636struct mm_struct *get_task_mm(struct task_struct *task)
 637{
 638        struct mm_struct *mm;
 639
 640        task_lock(task);
 641        mm = task->mm;
 642        if (mm) {
 643                if (task->flags & PF_KTHREAD)
 644                        mm = NULL;
 645                else
 646                        atomic_inc(&mm->mm_users);
 647        }
 648        task_unlock(task);
 649        return mm;
 650}
 651EXPORT_SYMBOL_GPL(get_task_mm);
 652
 653/* Please note the differences between mmput and mm_release.
 654 * mmput is called whenever we stop holding onto a mm_struct,
 655 * error success whatever.
 656 *
 657 * mm_release is called after a mm_struct has been removed
 658 * from the current process.
 659 *
 660 * This difference is important for error handling, when we
 661 * only half set up a mm_struct for a new process and need to restore
 662 * the old one.  Because we mmput the new mm_struct before
 663 * restoring the old one. . .
 664 * Eric Biederman 10 January 1998
 665 */
 666void mm_release(struct task_struct *tsk, struct mm_struct *mm)
 667{
 668        struct completion *vfork_done = tsk->vfork_done;
 669
 670        /* Get rid of any futexes when releasing the mm */
 671#ifdef CONFIG_FUTEX
 672        if (unlikely(tsk->robust_list)) {
 673                exit_robust_list(tsk);
 674                tsk->robust_list = NULL;
 675        }
 676#ifdef CONFIG_COMPAT
 677        if (unlikely(tsk->compat_robust_list)) {
 678                compat_exit_robust_list(tsk);
 679                tsk->compat_robust_list = NULL;
 680        }
 681#endif
 682        if (unlikely(!list_empty(&tsk->pi_state_list)))
 683                exit_pi_state_list(tsk);
 684#endif
 685
 686        /* Get rid of any cached register state */
 687        deactivate_mm(tsk, mm);
 688
 689        /* notify parent sleeping on vfork() */
 690        if (vfork_done) {
 691                tsk->vfork_done = NULL;
 692                complete(vfork_done);
 693        }
 694
 695        /*
 696         * If we're exiting normally, clear a user-space tid field if
 697         * requested.  We leave this alone when dying by signal, to leave
 698         * the value intact in a core dump, and to save the unnecessary
 699         * trouble otherwise.  Userland only wants this done for a sys_exit.
 700         */
 701        if (tsk->clear_child_tid) {
 702                if (!(tsk->flags & PF_SIGNALED) &&
 703                    atomic_read(&mm->mm_users) > 1) {
 704                        /*
 705                         * We don't check the error code - if userspace has
 706                         * not set up a proper pointer then tough luck.
 707                         */
 708                        put_user(0, tsk->clear_child_tid);
 709                        sys_futex(tsk->clear_child_tid, FUTEX_WAKE,
 710                                        1, NULL, NULL, 0);
 711                }
 712                tsk->clear_child_tid = NULL;
 713        }
 714}
 715
 716/*
 717 * Allocate a new mm structure and copy contents from the
 718 * mm structure of the passed in task structure.
 719 */
 720struct mm_struct *dup_mm(struct task_struct *tsk)
 721{
 722        struct mm_struct *mm, *oldmm = current->mm;
 723        int err;
 724
 725        if (!oldmm)
 726                return NULL;
 727
 728        mm = allocate_mm();
 729        if (!mm)
 730                goto fail_nomem;
 731
 732        memcpy(mm, oldmm, sizeof(*mm));
 733        mm_init_cpumask(mm);
 734
 735        /* Initializing for Swap token stuff */
 736        mm->token_priority = 0;
 737        mm->last_interval = 0;
 738
 739#ifdef CONFIG_TRANSPARENT_HUGEPAGE
 740        mm->pmd_huge_pte = NULL;
 741#endif
 742
 743        if (!mm_init(mm, tsk))
 744                goto fail_nomem;
 745
 746        if (init_new_context(tsk, mm))
 747                goto fail_nocontext;
 748
 749        dup_mm_exe_file(oldmm, mm);
 750
 751        err = dup_mmap(mm, oldmm);
 752        if (err)
 753                goto free_pt;
 754
 755        mm->hiwater_rss = get_mm_rss(mm);
 756        mm->hiwater_vm = mm->total_vm;
 757
 758        if (mm->binfmt && !try_module_get(mm->binfmt->module))
 759                goto free_pt;
 760
 761        return mm;
 762
 763free_pt:
 764        /* don't put binfmt in mmput, we haven't got module yet */
 765        mm->binfmt = NULL;
 766        mmput(mm);
 767
 768fail_nomem:
 769        return NULL;
 770
 771fail_nocontext:
 772        /*
 773         * If init_new_context() failed, we cannot use mmput() to free the mm
 774         * because it calls destroy_context()
 775         */
 776        mm_free_pgd(mm);
 777        free_mm(mm);
 778        return NULL;
 779}
 780
 781static int copy_mm(unsigned long clone_flags, struct task_struct *tsk)
 782{
 783        struct mm_struct *mm, *oldmm;
 784        int retval;
 785
 786        tsk->min_flt = tsk->maj_flt = 0;
 787        tsk->nvcsw = tsk->nivcsw = 0;
 788#ifdef CONFIG_DETECT_HUNG_TASK
 789        tsk->last_switch_count = tsk->nvcsw + tsk->nivcsw;
 790#endif
 791
 792        tsk->mm = NULL;
 793        tsk->active_mm = NULL;
 794
 795        /*
 796         * Are we cloning a kernel thread?
 797         *
 798         * We need to steal a active VM for that..
 799         */
 800        oldmm = current->mm;
 801        if (!oldmm)
 802                return 0;
 803
 804        if (clone_flags & CLONE_VM) {
 805                atomic_inc(&oldmm->mm_users);
 806                mm = oldmm;
 807                goto good_mm;
 808        }
 809
 810        retval = -ENOMEM;
 811        mm = dup_mm(tsk);
 812        if (!mm)
 813                goto fail_nomem;
 814
 815good_mm:
 816        /* Initializing for Swap token stuff */
 817        mm->token_priority = 0;
 818        mm->last_interval = 0;
 819        if (tsk->signal->oom_score_adj == OOM_SCORE_ADJ_MIN)
 820                atomic_inc(&mm->oom_disable_count);
 821
 822        tsk->mm = mm;
 823        tsk->active_mm = mm;
 824        return 0;
 825
 826fail_nomem:
 827        return retval;
 828}
 829
 830static int copy_fs(unsigned long clone_flags, struct task_struct *tsk)
 831{
 832        struct fs_struct *fs = current->fs;
 833        if (clone_flags & CLONE_FS) {
 834                /* tsk->fs is already what we want */
 835                spin_lock(&fs->lock);
 836                if (fs->in_exec) {
 837                        spin_unlock(&fs->lock);
 838                        return -EAGAIN;
 839                }
 840                fs->users++;
 841                spin_unlock(&fs->lock);
 842                return 0;
 843        }
 844        tsk->fs = copy_fs_struct(fs);
 845        if (!tsk->fs)
 846                return -ENOMEM;
 847        return 0;
 848}
 849
 850static int copy_files(unsigned long clone_flags, struct task_struct *tsk)
 851{
 852        struct files_struct *oldf, *newf;
 853        int error = 0;
 854
 855        /*
 856         * A background process may not have any files ...
 857         */
 858        oldf = current->files;
 859        if (!oldf)
 860                goto out;
 861
 862        if (clone_flags & CLONE_FILES) {
 863                atomic_inc(&oldf->count);
 864                goto out;
 865        }
 866
 867        newf = dup_fd(oldf, &error);
 868        if (!newf)
 869                goto out;
 870
 871        tsk->files = newf;
 872        error = 0;
 873out:
 874        return error;
 875}
 876
 877static int copy_io(unsigned long clone_flags, struct task_struct *tsk)
 878{
 879#ifdef CONFIG_BLOCK
 880        struct io_context *ioc = current->io_context;
 881
 882        if (!ioc)
 883                return 0;
 884        /*
 885         * Share io context with parent, if CLONE_IO is set
 886         */
 887        if (clone_flags & CLONE_IO) {
 888                tsk->io_context = ioc_task_link(ioc);
 889                if (unlikely(!tsk->io_context))
 890                        return -ENOMEM;
 891        } else if (ioprio_valid(ioc->ioprio)) {
 892                tsk->io_context = alloc_io_context(GFP_KERNEL, -1);
 893                if (unlikely(!tsk->io_context))
 894                        return -ENOMEM;
 895
 896                tsk->io_context->ioprio = ioc->ioprio;
 897        }
 898#endif
 899        return 0;
 900}
 901
 902static int copy_sighand(unsigned long clone_flags, struct task_struct *tsk)
 903{
 904        struct sighand_struct *sig;
 905
 906        if (clone_flags & CLONE_SIGHAND) {
 907                atomic_inc(&current->sighand->count);
 908                return 0;
 909        }
 910        sig = kmem_cache_alloc(sighand_cachep, GFP_KERNEL);
 911        rcu_assign_pointer(tsk->sighand, sig);
 912        if (!sig)
 913                return -ENOMEM;
 914        atomic_set(&sig->count, 1);
 915        memcpy(sig->action, current->sighand->action, sizeof(sig->action));
 916        return 0;
 917}
 918
 919void __cleanup_sighand(struct sighand_struct *sighand)
 920{
 921        if (atomic_dec_and_test(&sighand->count))
 922                kmem_cache_free(sighand_cachep, sighand);
 923}
 924
 925
 926/*
 927 * Initialize POSIX timer handling for a thread group.
 928 */
 929static void posix_cpu_timers_init_group(struct signal_struct *sig)
 930{
 931        unsigned long cpu_limit;
 932
 933        /* Thread group counters. */
 934        thread_group_cputime_init(sig);
 935
 936        cpu_limit = ACCESS_ONCE(sig->rlim[RLIMIT_CPU].rlim_cur);
 937        if (cpu_limit != RLIM_INFINITY) {
 938                sig->cputime_expires.prof_exp = secs_to_cputime(cpu_limit);
 939                sig->cputimer.running = 1;
 940        }
 941
 942        /* The timer lists. */
 943        INIT_LIST_HEAD(&sig->cpu_timers[0]);
 944        INIT_LIST_HEAD(&sig->cpu_timers[1]);
 945        INIT_LIST_HEAD(&sig->cpu_timers[2]);
 946}
 947
 948static int copy_signal(unsigned long clone_flags, struct task_struct *tsk)
 949{
 950        struct signal_struct *sig;
 951
 952        if (clone_flags & CLONE_THREAD)
 953                return 0;
 954
 955        sig = kmem_cache_zalloc(signal_cachep, GFP_KERNEL);
 956        tsk->signal = sig;
 957        if (!sig)
 958                return -ENOMEM;
 959
 960        sig->nr_threads = 1;
 961        atomic_set(&sig->live, 1);
 962        atomic_set(&sig->sigcnt, 1);
 963        init_waitqueue_head(&sig->wait_chldexit);
 964        if (clone_flags & CLONE_NEWPID)
 965                sig->flags |= SIGNAL_UNKILLABLE;
 966        sig->curr_target = tsk;
 967        init_sigpending(&sig->shared_pending);
 968        INIT_LIST_HEAD(&sig->posix_timers);
 969
 970        hrtimer_init(&sig->real_timer, CLOCK_MONOTONIC, HRTIMER_MODE_REL);
 971        sig->real_timer.function = it_real_fn;
 972
 973        task_lock(current->group_leader);
 974        memcpy(sig->rlim, current->signal->rlim, sizeof sig->rlim);
 975        task_unlock(current->group_leader);
 976
 977        posix_cpu_timers_init_group(sig);
 978
 979        tty_audit_fork(sig);
 980        sched_autogroup_fork(sig);
 981
 982#ifdef CONFIG_CGROUPS
 983        init_rwsem(&sig->threadgroup_fork_lock);
 984#endif
 985
 986        sig->oom_adj = current->signal->oom_adj;
 987        sig->oom_score_adj = current->signal->oom_score_adj;
 988        sig->oom_score_adj_min = current->signal->oom_score_adj_min;
 989
 990        mutex_init(&sig->cred_guard_mutex);
 991
 992        return 0;
 993}
 994
 995static void copy_flags(unsigned long clone_flags, struct task_struct *p)
 996{
 997        unsigned long new_flags = p->flags;
 998
 999        new_flags &= ~(PF_SUPERPRIV | PF_WQ_WORKER);
1000        new_flags |= PF_FORKNOEXEC;
1001        new_flags |= PF_STARTING;
1002        p->flags = new_flags;
1003        clear_freeze_flag(p);
1004}
1005
1006SYSCALL_DEFINE1(set_tid_address, int __user *, tidptr)
1007{
1008        current->clear_child_tid = tidptr;
1009
1010        return task_pid_vnr(current);
1011}
1012
1013static void rt_mutex_init_task(struct task_struct *p)
1014{
1015        raw_spin_lock_init(&p->pi_lock);
1016#ifdef CONFIG_RT_MUTEXES
1017        plist_head_init(&p->pi_waiters);
1018        p->pi_blocked_on = NULL;
1019#endif
1020}
1021
1022#ifdef CONFIG_MM_OWNER
1023void mm_init_owner(struct mm_struct *mm, struct task_struct *p)
1024{
1025        mm->owner = p;
1026}
1027#endif /* CONFIG_MM_OWNER */
1028
1029/*
1030 * Initialize POSIX timer handling for a single task.
1031 */
1032static void posix_cpu_timers_init(struct task_struct *tsk)
1033{
1034        tsk->cputime_expires.prof_exp = cputime_zero;
1035        tsk->cputime_expires.virt_exp = cputime_zero;
1036        tsk->cputime_expires.sched_exp = 0;
1037        INIT_LIST_HEAD(&tsk->cpu_timers[0]);
1038        INIT_LIST_HEAD(&tsk->cpu_timers[1]);
1039        INIT_LIST_HEAD(&tsk->cpu_timers[2]);
1040}
1041
1042/*
1043 * This creates a new process as a copy of the old one,
1044 * but does not actually start it yet.
1045 *
1046 * It copies the registers, and all the appropriate
1047 * parts of the process environment (as per the clone
1048 * flags). The actual kick-off is left to the caller.
1049 */
1050static struct task_struct *copy_process(unsigned long clone_flags,
1051                                        unsigned long stack_start,
1052                                        struct pt_regs *regs,
1053                                        unsigned long stack_size,
1054                                        int __user *child_tidptr,
1055                                        struct pid *pid,
1056                                        int trace)
1057{
1058        int retval;
1059        struct task_struct *p;
1060        int cgroup_callbacks_done = 0;
1061
1062        if ((clone_flags & (CLONE_NEWNS|CLONE_FS)) == (CLONE_NEWNS|CLONE_FS))
1063                return ERR_PTR(-EINVAL);
1064
1065        /*
1066         * Thread groups must share signals as well, and detached threads
1067         * can only be started up within the thread group.
1068         */
1069        if ((clone_flags & CLONE_THREAD) && !(clone_flags & CLONE_SIGHAND))
1070                return ERR_PTR(-EINVAL);
1071
1072        /*
1073         * Shared signal handlers imply shared VM. By way of the above,
1074         * thread groups also imply shared VM. Blocking this case allows
1075         * for various simplifications in other code.
1076         */
1077        if ((clone_flags & CLONE_SIGHAND) && !(clone_flags & CLONE_VM))
1078                return ERR_PTR(-EINVAL);
1079
1080        /*
1081         * Siblings of global init remain as zombies on exit since they are
1082         * not reaped by their parent (swapper). To solve this and to avoid
1083         * multi-rooted process trees, prevent global and container-inits
1084         * from creating siblings.
1085         */
1086        if ((clone_flags & CLONE_PARENT) &&
1087                                current->signal->flags & SIGNAL_UNKILLABLE)
1088                return ERR_PTR(-EINVAL);
1089
1090        retval = security_task_create(clone_flags);
1091        if (retval)
1092                goto fork_out;
1093
1094        retval = -ENOMEM;
1095        p = dup_task_struct(current);
1096        if (!p)
1097                goto fork_out;
1098
1099        ftrace_graph_init_task(p);
1100
1101        rt_mutex_init_task(p);
1102
1103#ifdef CONFIG_PROVE_LOCKING
1104        DEBUG_LOCKS_WARN_ON(!p->hardirqs_enabled);
1105        DEBUG_LOCKS_WARN_ON(!p->softirqs_enabled);
1106#endif
1107        retval = -EAGAIN;
1108        if (atomic_read(&p->real_cred->user->processes) >=
1109                        task_rlimit(p, RLIMIT_NPROC)) {
1110                if (!capable(CAP_SYS_ADMIN) && !capable(CAP_SYS_RESOURCE) &&
1111                    p->real_cred->user != INIT_USER)
1112                        goto bad_fork_free;
1113        }
1114        current->flags &= ~PF_NPROC_EXCEEDED;
1115
1116        retval = copy_creds(p, clone_flags);
1117        if (retval < 0)
1118                goto bad_fork_free;
1119
1120        /*
1121         * If multiple threads are within copy_process(), then this check
1122         * triggers too late. This doesn't hurt, the check is only there
1123         * to stop root fork bombs.
1124         */
1125        retval = -EAGAIN;
1126        if (nr_threads >= max_threads)
1127                goto bad_fork_cleanup_count;
1128
1129        if (!try_module_get(task_thread_info(p)->exec_domain->module))
1130                goto bad_fork_cleanup_count;
1131
1132        p->did_exec = 0;
1133        delayacct_tsk_init(p);  /* Must remain after dup_task_struct() */
1134        copy_flags(clone_flags, p);
1135        INIT_LIST_HEAD(&p->children);
1136        INIT_LIST_HEAD(&p->sibling);
1137        rcu_copy_process(p);
1138        p->vfork_done = NULL;
1139        spin_lock_init(&p->alloc_lock);
1140
1141        init_sigpending(&p->pending);
1142
1143        p->utime = cputime_zero;
1144        p->stime = cputime_zero;
1145        p->gtime = cputime_zero;
1146        p->utimescaled = cputime_zero;
1147        p->stimescaled = cputime_zero;
1148#ifndef CONFIG_VIRT_CPU_ACCOUNTING
1149        p->prev_utime = cputime_zero;
1150        p->prev_stime = cputime_zero;
1151#endif
1152#if defined(SPLIT_RSS_COUNTING)
1153        memset(&p->rss_stat, 0, sizeof(p->rss_stat));
1154#endif
1155
1156        p->default_timer_slack_ns = current->timer_slack_ns;
1157
1158        task_io_accounting_init(&p->ioac);
1159        acct_clear_integrals(p);
1160
1161        posix_cpu_timers_init(p);
1162
1163        do_posix_clock_monotonic_gettime(&p->start_time);
1164        p->real_start_time = p->start_time;
1165        monotonic_to_bootbased(&p->real_start_time);
1166        p->io_context = NULL;
1167        p->audit_context = NULL;
1168        if (clone_flags & CLONE_THREAD)
1169                threadgroup_fork_read_lock(current);
1170        cgroup_fork(p);
1171#ifdef CONFIG_NUMA
1172        p->mempolicy = mpol_dup(p->mempolicy);
1173        if (IS_ERR(p->mempolicy)) {
1174                retval = PTR_ERR(p->mempolicy);
1175                p->mempolicy = NULL;
1176                goto bad_fork_cleanup_cgroup;
1177        }
1178        mpol_fix_fork_child_flag(p);
1179#endif
1180#ifdef CONFIG_CPUSETS
1181        p->cpuset_mem_spread_rotor = NUMA_NO_NODE;
1182        p->cpuset_slab_spread_rotor = NUMA_NO_NODE;
1183#endif
1184#ifdef CONFIG_TRACE_IRQFLAGS
1185        p->irq_events = 0;
1186#ifdef __ARCH_WANT_INTERRUPTS_ON_CTXSW
1187        p->hardirqs_enabled = 1;
1188#else
1189        p->hardirqs_enabled = 0;
1190#endif
1191        p->hardirq_enable_ip = 0;
1192        p->hardirq_enable_event = 0;
1193        p->hardirq_disable_ip = _THIS_IP_;
1194        p->hardirq_disable_event = 0;
1195        p->softirqs_enabled = 1;
1196        p->softirq_enable_ip = _THIS_IP_;
1197        p->softirq_enable_event = 0;
1198        p->softirq_disable_ip = 0;
1199        p->softirq_disable_event = 0;
1200        p->hardirq_context = 0;
1201        p->softirq_context = 0;
1202#endif
1203#ifdef CONFIG_LOCKDEP
1204        p->lockdep_depth = 0; /* no locks held yet */
1205        p->curr_chain_key = 0;
1206        p->lockdep_recursion = 0;
1207#endif
1208
1209#ifdef CONFIG_DEBUG_MUTEXES
1210        p->blocked_on = NULL; /* not blocked yet */
1211#endif
1212#ifdef CONFIG_CGROUP_MEM_RES_CTLR
1213        p->memcg_batch.do_batch = 0;
1214        p->memcg_batch.memcg = NULL;
1215#endif
1216
1217        /* Perform scheduler related setup. Assign this task to a CPU. */
1218        sched_fork(p);
1219
1220        retval = perf_event_init_task(p);
1221        if (retval)
1222                goto bad_fork_cleanup_policy;
1223        retval = audit_alloc(p);
1224        if (retval)
1225                goto bad_fork_cleanup_policy;
1226        /* copy all the process information */
1227        retval = copy_semundo(clone_flags, p);
1228        if (retval)
1229                goto bad_fork_cleanup_audit;
1230        retval = copy_files(clone_flags, p);
1231        if (retval)
1232                goto bad_fork_cleanup_semundo;
1233        retval = copy_fs(clone_flags, p);
1234        if (retval)
1235                goto bad_fork_cleanup_files;
1236        retval = copy_sighand(clone_flags, p);
1237        if (retval)
1238                goto bad_fork_cleanup_fs;
1239        retval = copy_signal(clone_flags, p);
1240        if (retval)
1241                goto bad_fork_cleanup_sighand;
1242        retval = copy_mm(clone_flags, p);
1243        if (retval)
1244                goto bad_fork_cleanup_signal;
1245        retval = copy_namespaces(clone_flags, p);
1246        if (retval)
1247                goto bad_fork_cleanup_mm;
1248        retval = copy_io(clone_flags, p);
1249        if (retval)
1250                goto bad_fork_cleanup_namespaces;
1251        retval = copy_thread(clone_flags, stack_start, stack_size, p, regs);
1252        if (retval)
1253                goto bad_fork_cleanup_io;
1254
1255        if (pid != &init_struct_pid) {
1256                retval = -ENOMEM;
1257                pid = alloc_pid(p->nsproxy->pid_ns);
1258                if (!pid)
1259                        goto bad_fork_cleanup_io;
1260        }
1261
1262        p->pid = pid_nr(pid);
1263        p->tgid = p->pid;
1264        if (clone_flags & CLONE_THREAD)
1265                p->tgid = current->tgid;
1266
1267        p->set_child_tid = (clone_flags & CLONE_CHILD_SETTID) ? child_tidptr : NULL;
1268        /*
1269         * Clear TID on mm_release()?
1270         */
1271        p->clear_child_tid = (clone_flags & CLONE_CHILD_CLEARTID) ? child_tidptr : NULL;
1272#ifdef CONFIG_BLOCK
1273        p->plug = NULL;
1274#endif
1275#ifdef CONFIG_FUTEX
1276        p->robust_list = NULL;
1277#ifdef CONFIG_COMPAT
1278        p->compat_robust_list = NULL;
1279#endif
1280        INIT_LIST_HEAD(&p->pi_state_list);
1281        p->pi_state_cache = NULL;
1282#endif
1283        /*
1284         * sigaltstack should be cleared when sharing the same VM
1285         */
1286        if ((clone_flags & (CLONE_VM|CLONE_VFORK)) == CLONE_VM)
1287                p->sas_ss_sp = p->sas_ss_size = 0;
1288
1289        /*
1290         * Syscall tracing and stepping should be turned off in the
1291         * child regardless of CLONE_PTRACE.
1292         */
1293        user_disable_single_step(p);
1294        clear_tsk_thread_flag(p, TIF_SYSCALL_TRACE);
1295#ifdef TIF_SYSCALL_EMU
1296        clear_tsk_thread_flag(p, TIF_SYSCALL_EMU);
1297#endif
1298        clear_all_latency_tracing(p);
1299
1300        /* ok, now we should be set up.. */
1301        p->exit_signal = (clone_flags & CLONE_THREAD) ? -1 : (clone_flags & CSIGNAL);
1302        p->pdeath_signal = 0;
1303        p->exit_state = 0;
1304
1305        /*
1306         * Ok, make it visible to the rest of the system.
1307         * We dont wake it up yet.
1308         */
1309        p->group_leader = p;
1310        INIT_LIST_HEAD(&p->thread_group);
1311
1312        /* Now that the task is set up, run cgroup callbacks if
1313         * necessary. We need to run them before the task is visible
1314         * on the tasklist. */
1315        cgroup_fork_callbacks(p);
1316        cgroup_callbacks_done = 1;
1317
1318        /* Need tasklist lock for parent etc handling! */
1319        write_lock_irq(&tasklist_lock);
1320
1321        /* CLONE_PARENT re-uses the old parent */
1322        if (clone_flags & (CLONE_PARENT|CLONE_THREAD)) {
1323                p->real_parent = current->real_parent;
1324                p->parent_exec_id = current->parent_exec_id;
1325        } else {
1326                p->real_parent = current;
1327                p->parent_exec_id = current->self_exec_id;
1328        }
1329
1330        spin_lock(&current->sighand->siglock);
1331
1332        /*
1333         * Process group and session signals need to be delivered to just the
1334         * parent before the fork or both the parent and the child after the
1335         * fork. Restart if a signal comes in before we add the new process to
1336         * it's process group.
1337         * A fatal signal pending means that current will exit, so the new
1338         * thread can't slip out of an OOM kill (or normal SIGKILL).
1339        */
1340        recalc_sigpending();
1341        if (signal_pending(current)) {
1342                spin_unlock(&current->sighand->siglock);
1343                write_unlock_irq(&tasklist_lock);
1344                retval = -ERESTARTNOINTR;
1345                goto bad_fork_free_pid;
1346        }
1347
1348        if (clone_flags & CLONE_THREAD) {
1349                current->signal->nr_threads++;
1350                atomic_inc(&current->signal->live);
1351                atomic_inc(&current->signal->sigcnt);
1352                p->group_leader = current->group_leader;
1353                list_add_tail_rcu(&p->thread_group, &p->group_leader->thread_group);
1354        }
1355
1356        if (likely(p->pid)) {
1357                ptrace_init_task(p, (clone_flags & CLONE_PTRACE) || trace);
1358
1359                if (thread_group_leader(p)) {
1360                        if (is_child_reaper(pid))
1361                                p->nsproxy->pid_ns->child_reaper = p;
1362
1363                        p->signal->leader_pid = pid;
1364                        p->signal->tty = tty_kref_get(current->signal->tty);
1365                        attach_pid(p, PIDTYPE_PGID, task_pgrp(current));
1366                        attach_pid(p, PIDTYPE_SID, task_session(current));
1367                        list_add_tail(&p->sibling, &p->real_parent->children);
1368                        list_add_tail_rcu(&p->tasks, &init_task.tasks);
1369                        __this_cpu_inc(process_counts);
1370                }
1371                attach_pid(p, PIDTYPE_PID, pid);
1372                nr_threads++;
1373        }
1374
1375        total_forks++;
1376        spin_unlock(&current->sighand->siglock);
1377        write_unlock_irq(&tasklist_lock);
1378        proc_fork_connector(p);
1379        cgroup_post_fork(p);
1380        if (clone_flags & CLONE_THREAD)
1381                threadgroup_fork_read_unlock(current);
1382        perf_event_fork(p);
1383        return p;
1384
1385bad_fork_free_pid:
1386        if (pid != &init_struct_pid)
1387                free_pid(pid);
1388bad_fork_cleanup_io:
1389        if (p->io_context)
1390                exit_io_context(p);
1391bad_fork_cleanup_namespaces:
1392        exit_task_namespaces(p);
1393bad_fork_cleanup_mm:
1394        if (p->mm) {
1395                task_lock(p);
1396                if (p->signal->oom_score_adj == OOM_SCORE_ADJ_MIN)
1397                        atomic_dec(&p->mm->oom_disable_count);
1398                task_unlock(p);
1399                mmput(p->mm);
1400        }
1401bad_fork_cleanup_signal:
1402        if (!(clone_flags & CLONE_THREAD))
1403                free_signal_struct(p->signal);
1404bad_fork_cleanup_sighand:
1405        __cleanup_sighand(p->sighand);
1406bad_fork_cleanup_fs:
1407        exit_fs(p); /* blocking */
1408bad_fork_cleanup_files:
1409        exit_files(p); /* blocking */
1410bad_fork_cleanup_semundo:
1411        exit_sem(p);
1412bad_fork_cleanup_audit:
1413        audit_free(p);
1414bad_fork_cleanup_policy:
1415        perf_event_free_task(p);
1416#ifdef CONFIG_NUMA
1417        mpol_put(p->mempolicy);
1418bad_fork_cleanup_cgroup:
1419#endif
1420        if (clone_flags & CLONE_THREAD)
1421                threadgroup_fork_read_unlock(current);
1422        cgroup_exit(p, cgroup_callbacks_done);
1423        delayacct_tsk_free(p);
1424        module_put(task_thread_info(p)->exec_domain->module);
1425bad_fork_cleanup_count:
1426        atomic_dec(&p->cred->user->processes);
1427        exit_creds(p);
1428bad_fork_free:
1429        free_task(p);
1430fork_out:
1431        return ERR_PTR(retval);
1432}
1433
1434noinline struct pt_regs * __cpuinit __attribute__((weak)) idle_regs(struct pt_regs *regs)
1435{
1436        memset(regs, 0, sizeof(struct pt_regs));
1437        return regs;
1438}
1439
1440static inline void init_idle_pids(struct pid_link *links)
1441{
1442        enum pid_type type;
1443
1444        for (type = PIDTYPE_PID; type < PIDTYPE_MAX; ++type) {
1445                INIT_HLIST_NODE(&links[type].node); /* not really needed */
1446                links[type].pid = &init_struct_pid;
1447        }
1448}
1449
1450struct task_struct * __cpuinit fork_idle(int cpu)
1451{
1452        struct task_struct *task;
1453        struct pt_regs regs;
1454
1455        task = copy_process(CLONE_VM, 0, idle_regs(&regs), 0, NULL,
1456                            &init_struct_pid, 0);
1457        if (!IS_ERR(task)) {
1458                init_idle_pids(task->pids);
1459                init_idle(task, cpu);
1460        }
1461
1462        return task;
1463}
1464
1465/*
1466 *  Ok, this is the main fork-routine.
1467 *
1468 * It copies the process, and if successful kick-starts
1469 * it and waits for it to finish using the VM if required.
1470 */
1471long do_fork(unsigned long clone_flags,
1472              unsigned long stack_start,
1473              struct pt_regs *regs,
1474              unsigned long stack_size,
1475              int __user *parent_tidptr,
1476              int __user *child_tidptr)
1477{
1478        struct task_struct *p;
1479        int trace = 0;
1480        long nr;
1481
1482        /*
1483         * Do some preliminary argument and permissions checking before we
1484         * actually start allocating stuff
1485         */
1486        if (clone_flags & CLONE_NEWUSER) {
1487                if (clone_flags & CLONE_THREAD)
1488                        return -EINVAL;
1489                /* hopefully this check will go away when userns support is
1490                 * complete
1491                 */
1492                if (!capable(CAP_SYS_ADMIN) || !capable(CAP_SETUID) ||
1493                                !capable(CAP_SETGID))
1494                        return -EPERM;
1495        }
1496
1497        /*
1498         * Determine whether and which event to report to ptracer.  When
1499         * called from kernel_thread or CLONE_UNTRACED is explicitly
1500         * requested, no event is reported; otherwise, report if the event
1501         * for the type of forking is enabled.
1502         */
1503        if (likely(user_mode(regs)) && !(clone_flags & CLONE_UNTRACED)) {
1504                if (clone_flags & CLONE_VFORK)
1505                        trace = PTRACE_EVENT_VFORK;
1506                else if ((clone_flags & CSIGNAL) != SIGCHLD)
1507                        trace = PTRACE_EVENT_CLONE;
1508                else
1509                        trace = PTRACE_EVENT_FORK;
1510
1511                if (likely(!ptrace_event_enabled(current, trace)))
1512                        trace = 0;
1513        }
1514
1515        p = copy_process(clone_flags, stack_start, regs, stack_size,
1516                         child_tidptr, NULL, trace);
1517        /*
1518         * Do this prior waking up the new thread - the thread pointer
1519         * might get invalid after that point, if the thread exits quickly.
1520         */
1521        if (!IS_ERR(p)) {
1522                struct completion vfork;
1523
1524                trace_sched_process_fork(current, p);
1525
1526                nr = task_pid_vnr(p);
1527
1528                if (clone_flags & CLONE_PARENT_SETTID)
1529                        put_user(nr, parent_tidptr);
1530
1531                if (clone_flags & CLONE_VFORK) {
1532                        p->vfork_done = &vfork;
1533                        init_completion(&vfork);
1534                }
1535
1536                audit_finish_fork(p);
1537
1538                /*
1539                 * We set PF_STARTING at creation in case tracing wants to
1540                 * use this to distinguish a fully live task from one that
1541                 * hasn't finished SIGSTOP raising yet.  Now we clear it
1542                 * and set the child going.
1543                 */
1544                p->flags &= ~PF_STARTING;
1545
1546                wake_up_new_task(p);
1547
1548                /* forking complete and child started to run, tell ptracer */
1549                if (unlikely(trace))
1550                        ptrace_event(trace, nr);
1551
1552                if (clone_flags & CLONE_VFORK) {
1553                        freezer_do_not_count();
1554                        wait_for_completion(&vfork);
1555                        freezer_count();
1556                        ptrace_event(PTRACE_EVENT_VFORK_DONE, nr);
1557                }
1558        } else {
1559                nr = PTR_ERR(p);
1560        }
1561        return nr;
1562}
1563
1564#ifndef ARCH_MIN_MMSTRUCT_ALIGN
1565#define ARCH_MIN_MMSTRUCT_ALIGN 0
1566#endif
1567
1568static void sighand_ctor(void *data)
1569{
1570        struct sighand_struct *sighand = data;
1571
1572        spin_lock_init(&sighand->siglock);
1573        init_waitqueue_head(&sighand->signalfd_wqh);
1574}
1575
1576void __init proc_caches_init(void)
1577{
1578        sighand_cachep = kmem_cache_create("sighand_cache",
1579                        sizeof(struct sighand_struct), 0,
1580                        SLAB_HWCACHE_ALIGN|SLAB_PANIC|SLAB_DESTROY_BY_RCU|
1581                        SLAB_NOTRACK, sighand_ctor);
1582        signal_cachep = kmem_cache_create("signal_cache",
1583                        sizeof(struct signal_struct), 0,
1584                        SLAB_HWCACHE_ALIGN|SLAB_PANIC|SLAB_NOTRACK, NULL);
1585        files_cachep = kmem_cache_create("files_cache",
1586                        sizeof(struct files_struct), 0,
1587                        SLAB_HWCACHE_ALIGN|SLAB_PANIC|SLAB_NOTRACK, NULL);
1588        fs_cachep = kmem_cache_create("fs_cache",
1589                        sizeof(struct fs_struct), 0,
1590                        SLAB_HWCACHE_ALIGN|SLAB_PANIC|SLAB_NOTRACK, NULL);
1591        /*
1592         * FIXME! The "sizeof(struct mm_struct)" currently includes the
1593         * whole struct cpumask for the OFFSTACK case. We could change
1594         * this to *only* allocate as much of it as required by the
1595         * maximum number of CPU's we can ever have.  The cpumask_allocation
1596         * is at the end of the structure, exactly for that reason.
1597         */
1598        mm_cachep = kmem_cache_create("mm_struct",
1599                        sizeof(struct mm_struct), ARCH_MIN_MMSTRUCT_ALIGN,
1600                        SLAB_HWCACHE_ALIGN|SLAB_PANIC|SLAB_NOTRACK, NULL);
1601        vm_area_cachep = KMEM_CACHE(vm_area_struct, SLAB_PANIC);
1602        mmap_init();
1603        nsproxy_cache_init();
1604}
1605
1606/*
1607 * Check constraints on flags passed to the unshare system call.
1608 */
1609static int check_unshare_flags(unsigned long unshare_flags)
1610{
1611        if (unshare_flags & ~(CLONE_THREAD|CLONE_FS|CLONE_NEWNS|CLONE_SIGHAND|
1612                                CLONE_VM|CLONE_FILES|CLONE_SYSVSEM|
1613                                CLONE_NEWUTS|CLONE_NEWIPC|CLONE_NEWNET))
1614                return -EINVAL;
1615        /*
1616         * Not implemented, but pretend it works if there is nothing to
1617         * unshare. Note that unsharing CLONE_THREAD or CLONE_SIGHAND
1618         * needs to unshare vm.
1619         */
1620        if (unshare_flags & (CLONE_THREAD | CLONE_SIGHAND | CLONE_VM)) {
1621                /* FIXME: get_task_mm() increments ->mm_users */
1622                if (atomic_read(&current->mm->mm_users) > 1)
1623                        return -EINVAL;
1624        }
1625
1626        return 0;
1627}
1628
1629/*
1630 * Unshare the filesystem structure if it is being shared
1631 */
1632static int unshare_fs(unsigned long unshare_flags, struct fs_struct **new_fsp)
1633{
1634        struct fs_struct *fs = current->fs;
1635
1636        if (!(unshare_flags & CLONE_FS) || !fs)
1637                return 0;
1638
1639        /* don't need lock here; in the worst case we'll do useless copy */
1640        if (fs->users == 1)
1641                return 0;
1642
1643        *new_fsp = copy_fs_struct(fs);
1644        if (!*new_fsp)
1645                return -ENOMEM;
1646
1647        return 0;
1648}
1649
1650/*
1651 * Unshare file descriptor table if it is being shared
1652 */
1653static int unshare_fd(unsigned long unshare_flags, struct files_struct **new_fdp)
1654{
1655        struct files_struct *fd = current->files;
1656        int error = 0;
1657
1658        if ((unshare_flags & CLONE_FILES) &&
1659            (fd && atomic_read(&fd->count) > 1)) {
1660                *new_fdp = dup_fd(fd, &error);
1661                if (!*new_fdp)
1662                        return error;
1663        }
1664
1665        return 0;
1666}
1667
1668/*
1669 * unshare allows a process to 'unshare' part of the process
1670 * context which was originally shared using clone.  copy_*
1671 * functions used by do_fork() cannot be used here directly
1672 * because they modify an inactive task_struct that is being
1673 * constructed. Here we are modifying the current, active,
1674 * task_struct.
1675 */
1676SYSCALL_DEFINE1(unshare, unsigned long, unshare_flags)
1677{
1678        struct fs_struct *fs, *new_fs = NULL;
1679        struct files_struct *fd, *new_fd = NULL;
1680        struct nsproxy *new_nsproxy = NULL;
1681        int do_sysvsem = 0;
1682        int err;
1683
1684        err = check_unshare_flags(unshare_flags);
1685        if (err)
1686                goto bad_unshare_out;
1687
1688        /*
1689         * If unsharing namespace, must also unshare filesystem information.
1690         */
1691        if (unshare_flags & CLONE_NEWNS)
1692                unshare_flags |= CLONE_FS;
1693        /*
1694         * CLONE_NEWIPC must also detach from the undolist: after switching
1695         * to a new ipc namespace, the semaphore arrays from the old
1696         * namespace are unreachable.
1697         */
1698        if (unshare_flags & (CLONE_NEWIPC|CLONE_SYSVSEM))
1699                do_sysvsem = 1;
1700        err = unshare_fs(unshare_flags, &new_fs);
1701        if (err)
1702                goto bad_unshare_out;
1703        err = unshare_fd(unshare_flags, &new_fd);
1704        if (err)
1705                goto bad_unshare_cleanup_fs;
1706        err = unshare_nsproxy_namespaces(unshare_flags, &new_nsproxy, new_fs);
1707        if (err)
1708                goto bad_unshare_cleanup_fd;
1709
1710        if (new_fs || new_fd || do_sysvsem || new_nsproxy) {
1711                if (do_sysvsem) {
1712                        /*
1713                         * CLONE_SYSVSEM is equivalent to sys_exit().
1714                         */
1715                        exit_sem(current);
1716                }
1717
1718                if (new_nsproxy) {
1719                        switch_task_namespaces(current, new_nsproxy);
1720                        new_nsproxy = NULL;
1721                }
1722
1723                task_lock(current);
1724
1725                if (new_fs) {
1726                        fs = current->fs;
1727                        spin_lock(&fs->lock);
1728                        current->fs = new_fs;
1729                        if (--fs->users)
1730                                new_fs = NULL;
1731                        else
1732                                new_fs = fs;
1733                        spin_unlock(&fs->lock);
1734                }
1735
1736                if (new_fd) {
1737                        fd = current->files;
1738                        current->files = new_fd;
1739                        new_fd = fd;
1740                }
1741
1742                task_unlock(current);
1743        }
1744
1745        if (new_nsproxy)
1746                put_nsproxy(new_nsproxy);
1747
1748bad_unshare_cleanup_fd:
1749        if (new_fd)
1750                put_files_struct(new_fd);
1751
1752bad_unshare_cleanup_fs:
1753        if (new_fs)
1754                free_fs_struct(new_fs);
1755
1756bad_unshare_out:
1757        return err;
1758}
1759
1760/*
1761 *      Helper to unshare the files of the current task.
1762 *      We don't want to expose copy_files internals to
1763 *      the exec layer of the kernel.
1764 */
1765
1766int unshare_files(struct files_struct **displaced)
1767{
1768        struct task_struct *task = current;
1769        struct files_struct *copy = NULL;
1770        int error;
1771
1772        error = unshare_fd(CLONE_FILES, &copy);
1773        if (error || !copy) {
1774                *displaced = NULL;
1775                return error;
1776        }
1777        *displaced = task->files;
1778        task_lock(task);
1779        task->files = copy;
1780        task_unlock(task);
1781        return 0;
1782}
1783
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