linux/kernel/fork.c
<<
>>
Prefs
   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/seccomp.h>
  38#include <linux/swap.h>
  39#include <linux/syscalls.h>
  40#include <linux/jiffies.h>
  41#include <linux/futex.h>
  42#include <linux/compat.h>
  43#include <linux/kthread.h>
  44#include <linux/task_io_accounting_ops.h>
  45#include <linux/rcupdate.h>
  46#include <linux/ptrace.h>
  47#include <linux/mount.h>
  48#include <linux/audit.h>
  49#include <linux/memcontrol.h>
  50#include <linux/ftrace.h>
  51#include <linux/proc_fs.h>
  52#include <linux/profile.h>
  53#include <linux/rmap.h>
  54#include <linux/ksm.h>
  55#include <linux/acct.h>
  56#include <linux/tsacct_kern.h>
  57#include <linux/cn_proc.h>
  58#include <linux/freezer.h>
  59#include <linux/delayacct.h>
  60#include <linux/taskstats_kern.h>
  61#include <linux/random.h>
  62#include <linux/tty.h>
  63#include <linux/blkdev.h>
  64#include <linux/fs_struct.h>
  65#include <linux/magic.h>
  66#include <linux/perf_event.h>
  67#include <linux/posix-timers.h>
  68#include <linux/user-return-notifier.h>
  69#include <linux/oom.h>
  70#include <linux/khugepaged.h>
  71#include <linux/signalfd.h>
  72#include <linux/uprobes.h>
  73
  74#include <asm/pgtable.h>
  75#include <asm/pgalloc.h>
  76#include <asm/uaccess.h>
  77#include <asm/mmu_context.h>
  78#include <asm/cacheflush.h>
  79#include <asm/tlbflush.h>
  80
  81#include <trace/events/sched.h>
  82
  83#define CREATE_TRACE_POINTS
  84#include <trace/events/task.h>
  85
  86/*
  87 * Protected counters by write_lock_irq(&tasklist_lock)
  88 */
  89unsigned long total_forks;      /* Handle normal Linux uptimes. */
  90int nr_threads;                 /* The idle threads do not count.. */
  91
  92int max_threads;                /* tunable limit on nr_threads */
  93
  94DEFINE_PER_CPU(unsigned long, process_counts) = 0;
  95
  96__cacheline_aligned DEFINE_RWLOCK(tasklist_lock);  /* outer */
  97
  98#ifdef CONFIG_PROVE_RCU
  99int lockdep_tasklist_lock_is_held(void)
 100{
 101        return lockdep_is_held(&tasklist_lock);
 102}
 103EXPORT_SYMBOL_GPL(lockdep_tasklist_lock_is_held);
 104#endif /* #ifdef CONFIG_PROVE_RCU */
 105
 106int nr_processes(void)
 107{
 108        int cpu;
 109        int total = 0;
 110
 111        for_each_possible_cpu(cpu)
 112                total += per_cpu(process_counts, cpu);
 113
 114        return total;
 115}
 116
 117void __weak arch_release_task_struct(struct task_struct *tsk)
 118{
 119}
 120
 121#ifndef CONFIG_ARCH_TASK_STRUCT_ALLOCATOR
 122static struct kmem_cache *task_struct_cachep;
 123
 124static inline struct task_struct *alloc_task_struct_node(int node)
 125{
 126        return kmem_cache_alloc_node(task_struct_cachep, GFP_KERNEL, node);
 127}
 128
 129static inline void free_task_struct(struct task_struct *tsk)
 130{
 131        kmem_cache_free(task_struct_cachep, tsk);
 132}
 133#endif
 134
 135void __weak arch_release_thread_info(struct thread_info *ti)
 136{
 137}
 138
 139#ifndef CONFIG_ARCH_THREAD_INFO_ALLOCATOR
 140
 141/*
 142 * Allocate pages if THREAD_SIZE is >= PAGE_SIZE, otherwise use a
 143 * kmemcache based allocator.
 144 */
 145# if THREAD_SIZE >= PAGE_SIZE
 146static struct thread_info *alloc_thread_info_node(struct task_struct *tsk,
 147                                                  int node)
 148{
 149        struct page *page = alloc_pages_node(node, THREADINFO_GFP,
 150                                             THREAD_SIZE_ORDER);
 151
 152        return page ? page_address(page) : NULL;
 153}
 154
 155static inline void free_thread_info(struct thread_info *ti)
 156{
 157        free_pages((unsigned long)ti, THREAD_SIZE_ORDER);
 158}
 159# else
 160static struct kmem_cache *thread_info_cache;
 161
 162static struct thread_info *alloc_thread_info_node(struct task_struct *tsk,
 163                                                  int node)
 164{
 165        return kmem_cache_alloc_node(thread_info_cache, THREADINFO_GFP, node);
 166}
 167
 168static void free_thread_info(struct thread_info *ti)
 169{
 170        kmem_cache_free(thread_info_cache, ti);
 171}
 172
 173void thread_info_cache_init(void)
 174{
 175        thread_info_cache = kmem_cache_create("thread_info", THREAD_SIZE,
 176                                              THREAD_SIZE, 0, NULL);
 177        BUG_ON(thread_info_cache == NULL);
 178}
 179# endif
 180#endif
 181
 182/* SLAB cache for signal_struct structures (tsk->signal) */
 183static struct kmem_cache *signal_cachep;
 184
 185/* SLAB cache for sighand_struct structures (tsk->sighand) */
 186struct kmem_cache *sighand_cachep;
 187
 188/* SLAB cache for files_struct structures (tsk->files) */
 189struct kmem_cache *files_cachep;
 190
 191/* SLAB cache for fs_struct structures (tsk->fs) */
 192struct kmem_cache *fs_cachep;
 193
 194/* SLAB cache for vm_area_struct structures */
 195struct kmem_cache *vm_area_cachep;
 196
 197/* SLAB cache for mm_struct structures (tsk->mm) */
 198static struct kmem_cache *mm_cachep;
 199
 200static void account_kernel_stack(struct thread_info *ti, int account)
 201{
 202        struct zone *zone = page_zone(virt_to_page(ti));
 203
 204        mod_zone_page_state(zone, NR_KERNEL_STACK, account);
 205}
 206
 207void free_task(struct task_struct *tsk)
 208{
 209        account_kernel_stack(tsk->stack, -1);
 210        arch_release_thread_info(tsk->stack);
 211        free_thread_info(tsk->stack);
 212        rt_mutex_debug_task_free(tsk);
 213        ftrace_graph_exit_task(tsk);
 214        put_seccomp_filter(tsk);
 215        arch_release_task_struct(tsk);
 216        free_task_struct(tsk);
 217}
 218EXPORT_SYMBOL(free_task);
 219
 220static inline void free_signal_struct(struct signal_struct *sig)
 221{
 222        taskstats_tgid_free(sig);
 223        sched_autogroup_exit(sig);
 224        kmem_cache_free(signal_cachep, sig);
 225}
 226
 227static inline void put_signal_struct(struct signal_struct *sig)
 228{
 229        if (atomic_dec_and_test(&sig->sigcnt))
 230                free_signal_struct(sig);
 231}
 232
 233void __put_task_struct(struct task_struct *tsk)
 234{
 235        WARN_ON(!tsk->exit_state);
 236        WARN_ON(atomic_read(&tsk->usage));
 237        WARN_ON(tsk == current);
 238
 239        security_task_free(tsk);
 240        exit_creds(tsk);
 241        delayacct_tsk_free(tsk);
 242        put_signal_struct(tsk->signal);
 243
 244        if (!profile_handoff_task(tsk))
 245                free_task(tsk);
 246}
 247EXPORT_SYMBOL_GPL(__put_task_struct);
 248
 249void __init __weak arch_task_cache_init(void) { }
 250
 251void __init fork_init(unsigned long mempages)
 252{
 253#ifndef CONFIG_ARCH_TASK_STRUCT_ALLOCATOR
 254#ifndef ARCH_MIN_TASKALIGN
 255#define ARCH_MIN_TASKALIGN      L1_CACHE_BYTES
 256#endif
 257        /* create a slab on which task_structs can be allocated */
 258        task_struct_cachep =
 259                kmem_cache_create("task_struct", sizeof(struct task_struct),
 260                        ARCH_MIN_TASKALIGN, SLAB_PANIC | SLAB_NOTRACK, NULL);
 261#endif
 262
 263        /* do the arch specific task caches init */
 264        arch_task_cache_init();
 265
 266        /*
 267         * The default maximum number of threads is set to a safe
 268         * value: the thread structures can take up at most half
 269         * of memory.
 270         */
 271        max_threads = mempages / (8 * THREAD_SIZE / PAGE_SIZE);
 272
 273        /*
 274         * we need to allow at least 20 threads to boot a system
 275         */
 276        if (max_threads < 20)
 277                max_threads = 20;
 278
 279        init_task.signal->rlim[RLIMIT_NPROC].rlim_cur = max_threads/2;
 280        init_task.signal->rlim[RLIMIT_NPROC].rlim_max = max_threads/2;
 281        init_task.signal->rlim[RLIMIT_SIGPENDING] =
 282                init_task.signal->rlim[RLIMIT_NPROC];
 283}
 284
 285int __attribute__((weak)) arch_dup_task_struct(struct task_struct *dst,
 286                                               struct task_struct *src)
 287{
 288        *dst = *src;
 289        return 0;
 290}
 291
 292static struct task_struct *dup_task_struct(struct task_struct *orig)
 293{
 294        struct task_struct *tsk;
 295        struct thread_info *ti;
 296        unsigned long *stackend;
 297        int node = tsk_fork_get_node(orig);
 298        int err;
 299
 300        tsk = alloc_task_struct_node(node);
 301        if (!tsk)
 302                return NULL;
 303
 304        ti = alloc_thread_info_node(tsk, node);
 305        if (!ti)
 306                goto free_tsk;
 307
 308        err = arch_dup_task_struct(tsk, orig);
 309        if (err)
 310                goto free_ti;
 311
 312        tsk->stack = ti;
 313
 314        setup_thread_stack(tsk, orig);
 315        clear_user_return_notifier(tsk);
 316        clear_tsk_need_resched(tsk);
 317        stackend = end_of_stack(tsk);
 318        *stackend = STACK_END_MAGIC;    /* for overflow detection */
 319
 320#ifdef CONFIG_CC_STACKPROTECTOR
 321        tsk->stack_canary = get_random_int();
 322#endif
 323
 324        /*
 325         * One for us, one for whoever does the "release_task()" (usually
 326         * parent)
 327         */
 328        atomic_set(&tsk->usage, 2);
 329#ifdef CONFIG_BLK_DEV_IO_TRACE
 330        tsk->btrace_seq = 0;
 331#endif
 332        tsk->splice_pipe = NULL;
 333        tsk->task_frag.page = NULL;
 334
 335        account_kernel_stack(ti, 1);
 336
 337        return tsk;
 338
 339free_ti:
 340        free_thread_info(ti);
 341free_tsk:
 342        free_task_struct(tsk);
 343        return NULL;
 344}
 345
 346#ifdef CONFIG_MMU
 347static int dup_mmap(struct mm_struct *mm, struct mm_struct *oldmm)
 348{
 349        struct vm_area_struct *mpnt, *tmp, *prev, **pprev;
 350        struct rb_node **rb_link, *rb_parent;
 351        int retval;
 352        unsigned long charge;
 353        struct mempolicy *pol;
 354
 355        down_write(&oldmm->mmap_sem);
 356        flush_cache_dup_mm(oldmm);
 357        uprobe_dup_mmap(oldmm, mm);
 358        /*
 359         * Not linked in yet - no deadlock potential:
 360         */
 361        down_write_nested(&mm->mmap_sem, SINGLE_DEPTH_NESTING);
 362
 363        mm->locked_vm = 0;
 364        mm->mmap = NULL;
 365        mm->mmap_cache = NULL;
 366        mm->free_area_cache = oldmm->mmap_base;
 367        mm->cached_hole_size = ~0UL;
 368        mm->map_count = 0;
 369        cpumask_clear(mm_cpumask(mm));
 370        mm->mm_rb = RB_ROOT;
 371        rb_link = &mm->mm_rb.rb_node;
 372        rb_parent = NULL;
 373        pprev = &mm->mmap;
 374        retval = ksm_fork(mm, oldmm);
 375        if (retval)
 376                goto out;
 377        retval = khugepaged_fork(mm, oldmm);
 378        if (retval)
 379                goto out;
 380
 381        prev = NULL;
 382        for (mpnt = oldmm->mmap; mpnt; mpnt = mpnt->vm_next) {
 383                struct file *file;
 384
 385                if (mpnt->vm_flags & VM_DONTCOPY) {
 386                        vm_stat_account(mm, mpnt->vm_flags, mpnt->vm_file,
 387                                                        -vma_pages(mpnt));
 388                        continue;
 389                }
 390                charge = 0;
 391                if (mpnt->vm_flags & VM_ACCOUNT) {
 392                        unsigned long len = vma_pages(mpnt);
 393
 394                        if (security_vm_enough_memory_mm(oldmm, len)) /* sic */
 395                                goto fail_nomem;
 396                        charge = len;
 397                }
 398                tmp = kmem_cache_alloc(vm_area_cachep, GFP_KERNEL);
 399                if (!tmp)
 400                        goto fail_nomem;
 401                *tmp = *mpnt;
 402                INIT_LIST_HEAD(&tmp->anon_vma_chain);
 403                pol = mpol_dup(vma_policy(mpnt));
 404                retval = PTR_ERR(pol);
 405                if (IS_ERR(pol))
 406                        goto fail_nomem_policy;
 407                vma_set_policy(tmp, pol);
 408                tmp->vm_mm = mm;
 409                if (anon_vma_fork(tmp, mpnt))
 410                        goto fail_nomem_anon_vma_fork;
 411                tmp->vm_flags &= ~VM_LOCKED;
 412                tmp->vm_next = tmp->vm_prev = NULL;
 413                file = tmp->vm_file;
 414                if (file) {
 415                        struct inode *inode = file->f_path.dentry->d_inode;
 416                        struct address_space *mapping = file->f_mapping;
 417
 418                        get_file(file);
 419                        if (tmp->vm_flags & VM_DENYWRITE)
 420                                atomic_dec(&inode->i_writecount);
 421                        mutex_lock(&mapping->i_mmap_mutex);
 422                        if (tmp->vm_flags & VM_SHARED)
 423                                mapping->i_mmap_writable++;
 424                        flush_dcache_mmap_lock(mapping);
 425                        /* insert tmp into the share list, just after mpnt */
 426                        if (unlikely(tmp->vm_flags & VM_NONLINEAR))
 427                                vma_nonlinear_insert(tmp,
 428                                                &mapping->i_mmap_nonlinear);
 429                        else
 430                                vma_interval_tree_insert_after(tmp, mpnt,
 431                                                        &mapping->i_mmap);
 432                        flush_dcache_mmap_unlock(mapping);
 433                        mutex_unlock(&mapping->i_mmap_mutex);
 434                }
 435
 436                /*
 437                 * Clear hugetlb-related page reserves for children. This only
 438                 * affects MAP_PRIVATE mappings. Faults generated by the child
 439                 * are not guaranteed to succeed, even if read-only
 440                 */
 441                if (is_vm_hugetlb_page(tmp))
 442                        reset_vma_resv_huge_pages(tmp);
 443
 444                /*
 445                 * Link in the new vma and copy the page table entries.
 446                 */
 447                *pprev = tmp;
 448                pprev = &tmp->vm_next;
 449                tmp->vm_prev = prev;
 450                prev = tmp;
 451
 452                __vma_link_rb(mm, tmp, rb_link, rb_parent);
 453                rb_link = &tmp->vm_rb.rb_right;
 454                rb_parent = &tmp->vm_rb;
 455
 456                mm->map_count++;
 457                retval = copy_page_range(mm, oldmm, mpnt);
 458
 459                if (tmp->vm_ops && tmp->vm_ops->open)
 460                        tmp->vm_ops->open(tmp);
 461
 462                if (retval)
 463                        goto out;
 464        }
 465        /* a new mm has just been created */
 466        arch_dup_mmap(oldmm, mm);
 467        retval = 0;
 468out:
 469        up_write(&mm->mmap_sem);
 470        flush_tlb_mm(oldmm);
 471        up_write(&oldmm->mmap_sem);
 472        return retval;
 473fail_nomem_anon_vma_fork:
 474        mpol_put(pol);
 475fail_nomem_policy:
 476        kmem_cache_free(vm_area_cachep, tmp);
 477fail_nomem:
 478        retval = -ENOMEM;
 479        vm_unacct_memory(charge);
 480        goto out;
 481}
 482
 483static inline int mm_alloc_pgd(struct mm_struct *mm)
 484{
 485        mm->pgd = pgd_alloc(mm);
 486        if (unlikely(!mm->pgd))
 487                return -ENOMEM;
 488        return 0;
 489}
 490
 491static inline void mm_free_pgd(struct mm_struct *mm)
 492{
 493        pgd_free(mm, mm->pgd);
 494}
 495#else
 496#define dup_mmap(mm, oldmm)     (0)
 497#define mm_alloc_pgd(mm)        (0)
 498#define mm_free_pgd(mm)
 499#endif /* CONFIG_MMU */
 500
 501__cacheline_aligned_in_smp DEFINE_SPINLOCK(mmlist_lock);
 502
 503#define allocate_mm()   (kmem_cache_alloc(mm_cachep, GFP_KERNEL))
 504#define free_mm(mm)     (kmem_cache_free(mm_cachep, (mm)))
 505
 506static unsigned long default_dump_filter = MMF_DUMP_FILTER_DEFAULT;
 507
 508static int __init coredump_filter_setup(char *s)
 509{
 510        default_dump_filter =
 511                (simple_strtoul(s, NULL, 0) << MMF_DUMP_FILTER_SHIFT) &
 512                MMF_DUMP_FILTER_MASK;
 513        return 1;
 514}
 515
 516__setup("coredump_filter=", coredump_filter_setup);
 517
 518#include <linux/init_task.h>
 519
 520static void mm_init_aio(struct mm_struct *mm)
 521{
 522#ifdef CONFIG_AIO
 523        spin_lock_init(&mm->ioctx_lock);
 524        INIT_HLIST_HEAD(&mm->ioctx_list);
 525#endif
 526}
 527
 528static struct mm_struct *mm_init(struct mm_struct *mm, struct task_struct *p)
 529{
 530        atomic_set(&mm->mm_users, 1);
 531        atomic_set(&mm->mm_count, 1);
 532        init_rwsem(&mm->mmap_sem);
 533        INIT_LIST_HEAD(&mm->mmlist);
 534        mm->flags = (current->mm) ?
 535                (current->mm->flags & MMF_INIT_MASK) : default_dump_filter;
 536        mm->core_state = NULL;
 537        mm->nr_ptes = 0;
 538        memset(&mm->rss_stat, 0, sizeof(mm->rss_stat));
 539        spin_lock_init(&mm->page_table_lock);
 540        mm->free_area_cache = TASK_UNMAPPED_BASE;
 541        mm->cached_hole_size = ~0UL;
 542        mm_init_aio(mm);
 543        mm_init_owner(mm, p);
 544
 545        if (likely(!mm_alloc_pgd(mm))) {
 546                mm->def_flags = 0;
 547                mmu_notifier_mm_init(mm);
 548                return mm;
 549        }
 550
 551        free_mm(mm);
 552        return NULL;
 553}
 554
 555static void check_mm(struct mm_struct *mm)
 556{
 557        int i;
 558
 559        for (i = 0; i < NR_MM_COUNTERS; i++) {
 560                long x = atomic_long_read(&mm->rss_stat.count[i]);
 561
 562                if (unlikely(x))
 563                        printk(KERN_ALERT "BUG: Bad rss-counter state "
 564                                          "mm:%p idx:%d val:%ld\n", mm, i, x);
 565        }
 566
 567#ifdef CONFIG_TRANSPARENT_HUGEPAGE
 568        VM_BUG_ON(mm->pmd_huge_pte);
 569#endif
 570}
 571
 572/*
 573 * Allocate and initialize an mm_struct.
 574 */
 575struct mm_struct *mm_alloc(void)
 576{
 577        struct mm_struct *mm;
 578
 579        mm = allocate_mm();
 580        if (!mm)
 581                return NULL;
 582
 583        memset(mm, 0, sizeof(*mm));
 584        mm_init_cpumask(mm);
 585        return mm_init(mm, current);
 586}
 587
 588/*
 589 * Called when the last reference to the mm
 590 * is dropped: either by a lazy thread or by
 591 * mmput. Free the page directory and the mm.
 592 */
 593void __mmdrop(struct mm_struct *mm)
 594{
 595        BUG_ON(mm == &init_mm);
 596        mm_free_pgd(mm);
 597        destroy_context(mm);
 598        mmu_notifier_mm_destroy(mm);
 599        check_mm(mm);
 600        free_mm(mm);
 601}
 602EXPORT_SYMBOL_GPL(__mmdrop);
 603
 604/*
 605 * Decrement the use count and release all resources for an mm.
 606 */
 607void mmput(struct mm_struct *mm)
 608{
 609        might_sleep();
 610
 611        if (atomic_dec_and_test(&mm->mm_users)) {
 612                uprobe_clear_state(mm);
 613                exit_aio(mm);
 614                ksm_exit(mm);
 615                khugepaged_exit(mm); /* must run before exit_mmap */
 616                exit_mmap(mm);
 617                set_mm_exe_file(mm, NULL);
 618                if (!list_empty(&mm->mmlist)) {
 619                        spin_lock(&mmlist_lock);
 620                        list_del(&mm->mmlist);
 621                        spin_unlock(&mmlist_lock);
 622                }
 623                if (mm->binfmt)
 624                        module_put(mm->binfmt->module);
 625                mmdrop(mm);
 626        }
 627}
 628EXPORT_SYMBOL_GPL(mmput);
 629
 630void set_mm_exe_file(struct mm_struct *mm, struct file *new_exe_file)
 631{
 632        if (new_exe_file)
 633                get_file(new_exe_file);
 634        if (mm->exe_file)
 635                fput(mm->exe_file);
 636        mm->exe_file = new_exe_file;
 637}
 638
 639struct file *get_mm_exe_file(struct mm_struct *mm)
 640{
 641        struct file *exe_file;
 642
 643        /* We need mmap_sem to protect against races with removal of exe_file */
 644        down_read(&mm->mmap_sem);
 645        exe_file = mm->exe_file;
 646        if (exe_file)
 647                get_file(exe_file);
 648        up_read(&mm->mmap_sem);
 649        return exe_file;
 650}
 651
 652static void dup_mm_exe_file(struct mm_struct *oldmm, struct mm_struct *newmm)
 653{
 654        /* It's safe to write the exe_file pointer without exe_file_lock because
 655         * this is called during fork when the task is not yet in /proc */
 656        newmm->exe_file = get_mm_exe_file(oldmm);
 657}
 658
 659/**
 660 * get_task_mm - acquire a reference to the task's mm
 661 *
 662 * Returns %NULL if the task has no mm.  Checks PF_KTHREAD (meaning
 663 * this kernel workthread has transiently adopted a user mm with use_mm,
 664 * to do its AIO) is not set and if so returns a reference to it, after
 665 * bumping up the use count.  User must release the mm via mmput()
 666 * after use.  Typically used by /proc and ptrace.
 667 */
 668struct mm_struct *get_task_mm(struct task_struct *task)
 669{
 670        struct mm_struct *mm;
 671
 672        task_lock(task);
 673        mm = task->mm;
 674        if (mm) {
 675                if (task->flags & PF_KTHREAD)
 676                        mm = NULL;
 677                else
 678                        atomic_inc(&mm->mm_users);
 679        }
 680        task_unlock(task);
 681        return mm;
 682}
 683EXPORT_SYMBOL_GPL(get_task_mm);
 684
 685struct mm_struct *mm_access(struct task_struct *task, unsigned int mode)
 686{
 687        struct mm_struct *mm;
 688        int err;
 689
 690        err =  mutex_lock_killable(&task->signal->cred_guard_mutex);
 691        if (err)
 692                return ERR_PTR(err);
 693
 694        mm = get_task_mm(task);
 695        if (mm && mm != current->mm &&
 696                        !ptrace_may_access(task, mode)) {
 697                mmput(mm);
 698                mm = ERR_PTR(-EACCES);
 699        }
 700        mutex_unlock(&task->signal->cred_guard_mutex);
 701
 702        return mm;
 703}
 704
 705static void complete_vfork_done(struct task_struct *tsk)
 706{
 707        struct completion *vfork;
 708
 709        task_lock(tsk);
 710        vfork = tsk->vfork_done;
 711        if (likely(vfork)) {
 712                tsk->vfork_done = NULL;
 713                complete(vfork);
 714        }
 715        task_unlock(tsk);
 716}
 717
 718static int wait_for_vfork_done(struct task_struct *child,
 719                                struct completion *vfork)
 720{
 721        int killed;
 722
 723        freezer_do_not_count();
 724        killed = wait_for_completion_killable(vfork);
 725        freezer_count();
 726
 727        if (killed) {
 728                task_lock(child);
 729                child->vfork_done = NULL;
 730                task_unlock(child);
 731        }
 732
 733        put_task_struct(child);
 734        return killed;
 735}
 736
 737/* Please note the differences between mmput and mm_release.
 738 * mmput is called whenever we stop holding onto a mm_struct,
 739 * error success whatever.
 740 *
 741 * mm_release is called after a mm_struct has been removed
 742 * from the current process.
 743 *
 744 * This difference is important for error handling, when we
 745 * only half set up a mm_struct for a new process and need to restore
 746 * the old one.  Because we mmput the new mm_struct before
 747 * restoring the old one. . .
 748 * Eric Biederman 10 January 1998
 749 */
 750void mm_release(struct task_struct *tsk, struct mm_struct *mm)
 751{
 752        /* Get rid of any futexes when releasing the mm */
 753#ifdef CONFIG_FUTEX
 754        if (unlikely(tsk->robust_list)) {
 755                exit_robust_list(tsk);
 756                tsk->robust_list = NULL;
 757        }
 758#ifdef CONFIG_COMPAT
 759        if (unlikely(tsk->compat_robust_list)) {
 760                compat_exit_robust_list(tsk);
 761                tsk->compat_robust_list = NULL;
 762        }
 763#endif
 764        if (unlikely(!list_empty(&tsk->pi_state_list)))
 765                exit_pi_state_list(tsk);
 766#endif
 767
 768        uprobe_free_utask(tsk);
 769
 770        /* Get rid of any cached register state */
 771        deactivate_mm(tsk, mm);
 772
 773        /*
 774         * If we're exiting normally, clear a user-space tid field if
 775         * requested.  We leave this alone when dying by signal, to leave
 776         * the value intact in a core dump, and to save the unnecessary
 777         * trouble, say, a killed vfork parent shouldn't touch this mm.
 778         * Userland only wants this done for a sys_exit.
 779         */
 780        if (tsk->clear_child_tid) {
 781                if (!(tsk->flags & PF_SIGNALED) &&
 782                    atomic_read(&mm->mm_users) > 1) {
 783                        /*
 784                         * We don't check the error code - if userspace has
 785                         * not set up a proper pointer then tough luck.
 786                         */
 787                        put_user(0, tsk->clear_child_tid);
 788                        sys_futex(tsk->clear_child_tid, FUTEX_WAKE,
 789                                        1, NULL, NULL, 0);
 790                }
 791                tsk->clear_child_tid = NULL;
 792        }
 793
 794        /*
 795         * All done, finally we can wake up parent and return this mm to him.
 796         * Also kthread_stop() uses this completion for synchronization.
 797         */
 798        if (tsk->vfork_done)
 799                complete_vfork_done(tsk);
 800}
 801
 802/*
 803 * Allocate a new mm structure and copy contents from the
 804 * mm structure of the passed in task structure.
 805 */
 806struct mm_struct *dup_mm(struct task_struct *tsk)
 807{
 808        struct mm_struct *mm, *oldmm = current->mm;
 809        int err;
 810
 811        if (!oldmm)
 812                return NULL;
 813
 814        mm = allocate_mm();
 815        if (!mm)
 816                goto fail_nomem;
 817
 818        memcpy(mm, oldmm, sizeof(*mm));
 819        mm_init_cpumask(mm);
 820
 821#ifdef CONFIG_TRANSPARENT_HUGEPAGE
 822        mm->pmd_huge_pte = NULL;
 823#endif
 824        if (!mm_init(mm, tsk))
 825                goto fail_nomem;
 826
 827        if (init_new_context(tsk, mm))
 828                goto fail_nocontext;
 829
 830        dup_mm_exe_file(oldmm, mm);
 831
 832        err = dup_mmap(mm, oldmm);
 833        if (err)
 834                goto free_pt;
 835
 836        mm->hiwater_rss = get_mm_rss(mm);
 837        mm->hiwater_vm = mm->total_vm;
 838
 839        if (mm->binfmt && !try_module_get(mm->binfmt->module))
 840                goto free_pt;
 841
 842        return mm;
 843
 844free_pt:
 845        /* don't put binfmt in mmput, we haven't got module yet */
 846        mm->binfmt = NULL;
 847        mmput(mm);
 848
 849fail_nomem:
 850        return NULL;
 851
 852fail_nocontext:
 853        /*
 854         * If init_new_context() failed, we cannot use mmput() to free the mm
 855         * because it calls destroy_context()
 856         */
 857        mm_free_pgd(mm);
 858        free_mm(mm);
 859        return NULL;
 860}
 861
 862static int copy_mm(unsigned long clone_flags, struct task_struct *tsk)
 863{
 864        struct mm_struct *mm, *oldmm;
 865        int retval;
 866
 867        tsk->min_flt = tsk->maj_flt = 0;
 868        tsk->nvcsw = tsk->nivcsw = 0;
 869#ifdef CONFIG_DETECT_HUNG_TASK
 870        tsk->last_switch_count = tsk->nvcsw + tsk->nivcsw;
 871#endif
 872
 873        tsk->mm = NULL;
 874        tsk->active_mm = NULL;
 875
 876        /*
 877         * Are we cloning a kernel thread?
 878         *
 879         * We need to steal a active VM for that..
 880         */
 881        oldmm = current->mm;
 882        if (!oldmm)
 883                return 0;
 884
 885        if (clone_flags & CLONE_VM) {
 886                atomic_inc(&oldmm->mm_users);
 887                mm = oldmm;
 888                goto good_mm;
 889        }
 890
 891        retval = -ENOMEM;
 892        mm = dup_mm(tsk);
 893        if (!mm)
 894                goto fail_nomem;
 895
 896good_mm:
 897        tsk->mm = mm;
 898        tsk->active_mm = mm;
 899        return 0;
 900
 901fail_nomem:
 902        return retval;
 903}
 904
 905static int copy_fs(unsigned long clone_flags, struct task_struct *tsk)
 906{
 907        struct fs_struct *fs = current->fs;
 908        if (clone_flags & CLONE_FS) {
 909                /* tsk->fs is already what we want */
 910                spin_lock(&fs->lock);
 911                if (fs->in_exec) {
 912                        spin_unlock(&fs->lock);
 913                        return -EAGAIN;
 914                }
 915                fs->users++;
 916                spin_unlock(&fs->lock);
 917                return 0;
 918        }
 919        tsk->fs = copy_fs_struct(fs);
 920        if (!tsk->fs)
 921                return -ENOMEM;
 922        return 0;
 923}
 924
 925static int copy_files(unsigned long clone_flags, struct task_struct *tsk)
 926{
 927        struct files_struct *oldf, *newf;
 928        int error = 0;
 929
 930        /*
 931         * A background process may not have any files ...
 932         */
 933        oldf = current->files;
 934        if (!oldf)
 935                goto out;
 936
 937        if (clone_flags & CLONE_FILES) {
 938                atomic_inc(&oldf->count);
 939                goto out;
 940        }
 941
 942        newf = dup_fd(oldf, &error);
 943        if (!newf)
 944                goto out;
 945
 946        tsk->files = newf;
 947        error = 0;
 948out:
 949        return error;
 950}
 951
 952static int copy_io(unsigned long clone_flags, struct task_struct *tsk)
 953{
 954#ifdef CONFIG_BLOCK
 955        struct io_context *ioc = current->io_context;
 956        struct io_context *new_ioc;
 957
 958        if (!ioc)
 959                return 0;
 960        /*
 961         * Share io context with parent, if CLONE_IO is set
 962         */
 963        if (clone_flags & CLONE_IO) {
 964                ioc_task_link(ioc);
 965                tsk->io_context = ioc;
 966        } else if (ioprio_valid(ioc->ioprio)) {
 967                new_ioc = get_task_io_context(tsk, GFP_KERNEL, NUMA_NO_NODE);
 968                if (unlikely(!new_ioc))
 969                        return -ENOMEM;
 970
 971                new_ioc->ioprio = ioc->ioprio;
 972                put_io_context(new_ioc);
 973        }
 974#endif
 975        return 0;
 976}
 977
 978static int copy_sighand(unsigned long clone_flags, struct task_struct *tsk)
 979{
 980        struct sighand_struct *sig;
 981
 982        if (clone_flags & CLONE_SIGHAND) {
 983                atomic_inc(&current->sighand->count);
 984                return 0;
 985        }
 986        sig = kmem_cache_alloc(sighand_cachep, GFP_KERNEL);
 987        rcu_assign_pointer(tsk->sighand, sig);
 988        if (!sig)
 989                return -ENOMEM;
 990        atomic_set(&sig->count, 1);
 991        memcpy(sig->action, current->sighand->action, sizeof(sig->action));
 992        return 0;
 993}
 994
 995void __cleanup_sighand(struct sighand_struct *sighand)
 996{
 997        if (atomic_dec_and_test(&sighand->count)) {
 998                signalfd_cleanup(sighand);
 999                kmem_cache_free(sighand_cachep, sighand);
1000        }
1001}
1002
1003
1004/*
1005 * Initialize POSIX timer handling for a thread group.
1006 */
1007static void posix_cpu_timers_init_group(struct signal_struct *sig)
1008{
1009        unsigned long cpu_limit;
1010
1011        /* Thread group counters. */
1012        thread_group_cputime_init(sig);
1013
1014        cpu_limit = ACCESS_ONCE(sig->rlim[RLIMIT_CPU].rlim_cur);
1015        if (cpu_limit != RLIM_INFINITY) {
1016                sig->cputime_expires.prof_exp = secs_to_cputime(cpu_limit);
1017                sig->cputimer.running = 1;
1018        }
1019
1020        /* The timer lists. */
1021        INIT_LIST_HEAD(&sig->cpu_timers[0]);
1022        INIT_LIST_HEAD(&sig->cpu_timers[1]);
1023        INIT_LIST_HEAD(&sig->cpu_timers[2]);
1024}
1025
1026static int copy_signal(unsigned long clone_flags, struct task_struct *tsk)
1027{
1028        struct signal_struct *sig;
1029
1030        if (clone_flags & CLONE_THREAD)
1031                return 0;
1032
1033        sig = kmem_cache_zalloc(signal_cachep, GFP_KERNEL);
1034        tsk->signal = sig;
1035        if (!sig)
1036                return -ENOMEM;
1037
1038        sig->nr_threads = 1;
1039        atomic_set(&sig->live, 1);
1040        atomic_set(&sig->sigcnt, 1);
1041        init_waitqueue_head(&sig->wait_chldexit);
1042        if (clone_flags & CLONE_NEWPID)
1043                sig->flags |= SIGNAL_UNKILLABLE;
1044        sig->curr_target = tsk;
1045        init_sigpending(&sig->shared_pending);
1046        INIT_LIST_HEAD(&sig->posix_timers);
1047
1048        hrtimer_init(&sig->real_timer, CLOCK_MONOTONIC, HRTIMER_MODE_REL);
1049        sig->real_timer.function = it_real_fn;
1050
1051        task_lock(current->group_leader);
1052        memcpy(sig->rlim, current->signal->rlim, sizeof sig->rlim);
1053        task_unlock(current->group_leader);
1054
1055        posix_cpu_timers_init_group(sig);
1056
1057        tty_audit_fork(sig);
1058        sched_autogroup_fork(sig);
1059
1060#ifdef CONFIG_CGROUPS
1061        init_rwsem(&sig->group_rwsem);
1062#endif
1063
1064        sig->oom_score_adj = current->signal->oom_score_adj;
1065        sig->oom_score_adj_min = current->signal->oom_score_adj_min;
1066
1067        sig->has_child_subreaper = current->signal->has_child_subreaper ||
1068                                   current->signal->is_child_subreaper;
1069
1070        mutex_init(&sig->cred_guard_mutex);
1071
1072        return 0;
1073}
1074
1075static void copy_flags(unsigned long clone_flags, struct task_struct *p)
1076{
1077        unsigned long new_flags = p->flags;
1078
1079        new_flags &= ~(PF_SUPERPRIV | PF_WQ_WORKER);
1080        new_flags |= PF_FORKNOEXEC;
1081        p->flags = new_flags;
1082}
1083
1084SYSCALL_DEFINE1(set_tid_address, int __user *, tidptr)
1085{
1086        current->clear_child_tid = tidptr;
1087
1088        return task_pid_vnr(current);
1089}
1090
1091static void rt_mutex_init_task(struct task_struct *p)
1092{
1093        raw_spin_lock_init(&p->pi_lock);
1094#ifdef CONFIG_RT_MUTEXES
1095        plist_head_init(&p->pi_waiters);
1096        p->pi_blocked_on = NULL;
1097#endif
1098}
1099
1100#ifdef CONFIG_MM_OWNER
1101void mm_init_owner(struct mm_struct *mm, struct task_struct *p)
1102{
1103        mm->owner = p;
1104}
1105#endif /* CONFIG_MM_OWNER */
1106
1107/*
1108 * Initialize POSIX timer handling for a single task.
1109 */
1110static void posix_cpu_timers_init(struct task_struct *tsk)
1111{
1112        tsk->cputime_expires.prof_exp = 0;
1113        tsk->cputime_expires.virt_exp = 0;
1114        tsk->cputime_expires.sched_exp = 0;
1115        INIT_LIST_HEAD(&tsk->cpu_timers[0]);
1116        INIT_LIST_HEAD(&tsk->cpu_timers[1]);
1117        INIT_LIST_HEAD(&tsk->cpu_timers[2]);
1118}
1119
1120/*
1121 * This creates a new process as a copy of the old one,
1122 * but does not actually start it yet.
1123 *
1124 * It copies the registers, and all the appropriate
1125 * parts of the process environment (as per the clone
1126 * flags). The actual kick-off is left to the caller.
1127 */
1128static struct task_struct *copy_process(unsigned long clone_flags,
1129                                        unsigned long stack_start,
1130                                        struct pt_regs *regs,
1131                                        unsigned long stack_size,
1132                                        int __user *child_tidptr,
1133                                        struct pid *pid,
1134                                        int trace)
1135{
1136        int retval;
1137        struct task_struct *p;
1138
1139        if ((clone_flags & (CLONE_NEWNS|CLONE_FS)) == (CLONE_NEWNS|CLONE_FS))
1140                return ERR_PTR(-EINVAL);
1141
1142        /*
1143         * Thread groups must share signals as well, and detached threads
1144         * can only be started up within the thread group.
1145         */
1146        if ((clone_flags & CLONE_THREAD) && !(clone_flags & CLONE_SIGHAND))
1147                return ERR_PTR(-EINVAL);
1148
1149        /*
1150         * Shared signal handlers imply shared VM. By way of the above,
1151         * thread groups also imply shared VM. Blocking this case allows
1152         * for various simplifications in other code.
1153         */
1154        if ((clone_flags & CLONE_SIGHAND) && !(clone_flags & CLONE_VM))
1155                return ERR_PTR(-EINVAL);
1156
1157        /*
1158         * Siblings of global init remain as zombies on exit since they are
1159         * not reaped by their parent (swapper). To solve this and to avoid
1160         * multi-rooted process trees, prevent global and container-inits
1161         * from creating siblings.
1162         */
1163        if ((clone_flags & CLONE_PARENT) &&
1164                                current->signal->flags & SIGNAL_UNKILLABLE)
1165                return ERR_PTR(-EINVAL);
1166
1167        retval = security_task_create(clone_flags);
1168        if (retval)
1169                goto fork_out;
1170
1171        retval = -ENOMEM;
1172        p = dup_task_struct(current);
1173        if (!p)
1174                goto fork_out;
1175
1176        ftrace_graph_init_task(p);
1177        get_seccomp_filter(p);
1178
1179        rt_mutex_init_task(p);
1180
1181#ifdef CONFIG_PROVE_LOCKING
1182        DEBUG_LOCKS_WARN_ON(!p->hardirqs_enabled);
1183        DEBUG_LOCKS_WARN_ON(!p->softirqs_enabled);
1184#endif
1185        retval = -EAGAIN;
1186        if (atomic_read(&p->real_cred->user->processes) >=
1187                        task_rlimit(p, RLIMIT_NPROC)) {
1188                if (!capable(CAP_SYS_ADMIN) && !capable(CAP_SYS_RESOURCE) &&
1189                    p->real_cred->user != INIT_USER)
1190                        goto bad_fork_free;
1191        }
1192        current->flags &= ~PF_NPROC_EXCEEDED;
1193
1194        retval = copy_creds(p, clone_flags);
1195        if (retval < 0)
1196                goto bad_fork_free;
1197
1198        /*
1199         * If multiple threads are within copy_process(), then this check
1200         * triggers too late. This doesn't hurt, the check is only there
1201         * to stop root fork bombs.
1202         */
1203        retval = -EAGAIN;
1204        if (nr_threads >= max_threads)
1205                goto bad_fork_cleanup_count;
1206
1207        if (!try_module_get(task_thread_info(p)->exec_domain->module))
1208                goto bad_fork_cleanup_count;
1209
1210        p->did_exec = 0;
1211        delayacct_tsk_init(p);  /* Must remain after dup_task_struct() */
1212        copy_flags(clone_flags, p);
1213        INIT_LIST_HEAD(&p->children);
1214        INIT_LIST_HEAD(&p->sibling);
1215        rcu_copy_process(p);
1216        p->vfork_done = NULL;
1217        spin_lock_init(&p->alloc_lock);
1218
1219        init_sigpending(&p->pending);
1220
1221        p->utime = p->stime = p->gtime = 0;
1222        p->utimescaled = p->stimescaled = 0;
1223#ifndef CONFIG_VIRT_CPU_ACCOUNTING
1224        p->prev_utime = p->prev_stime = 0;
1225#endif
1226#if defined(SPLIT_RSS_COUNTING)
1227        memset(&p->rss_stat, 0, sizeof(p->rss_stat));
1228#endif
1229
1230        p->default_timer_slack_ns = current->timer_slack_ns;
1231
1232        task_io_accounting_init(&p->ioac);
1233        acct_clear_integrals(p);
1234
1235        posix_cpu_timers_init(p);
1236
1237        do_posix_clock_monotonic_gettime(&p->start_time);
1238        p->real_start_time = p->start_time;
1239        monotonic_to_bootbased(&p->real_start_time);
1240        p->io_context = NULL;
1241        p->audit_context = NULL;
1242        if (clone_flags & CLONE_THREAD)
1243                threadgroup_change_begin(current);
1244        cgroup_fork(p);
1245#ifdef CONFIG_NUMA
1246        p->mempolicy = mpol_dup(p->mempolicy);
1247        if (IS_ERR(p->mempolicy)) {
1248                retval = PTR_ERR(p->mempolicy);
1249                p->mempolicy = NULL;
1250                goto bad_fork_cleanup_cgroup;
1251        }
1252        mpol_fix_fork_child_flag(p);
1253#endif
1254#ifdef CONFIG_CPUSETS
1255        p->cpuset_mem_spread_rotor = NUMA_NO_NODE;
1256        p->cpuset_slab_spread_rotor = NUMA_NO_NODE;
1257        seqcount_init(&p->mems_allowed_seq);
1258#endif
1259#ifdef CONFIG_TRACE_IRQFLAGS
1260        p->irq_events = 0;
1261        p->hardirqs_enabled = 0;
1262        p->hardirq_enable_ip = 0;
1263        p->hardirq_enable_event = 0;
1264        p->hardirq_disable_ip = _THIS_IP_;
1265        p->hardirq_disable_event = 0;
1266        p->softirqs_enabled = 1;
1267        p->softirq_enable_ip = _THIS_IP_;
1268        p->softirq_enable_event = 0;
1269        p->softirq_disable_ip = 0;
1270        p->softirq_disable_event = 0;
1271        p->hardirq_context = 0;
1272        p->softirq_context = 0;
1273#endif
1274#ifdef CONFIG_LOCKDEP
1275        p->lockdep_depth = 0; /* no locks held yet */
1276        p->curr_chain_key = 0;
1277        p->lockdep_recursion = 0;
1278#endif
1279
1280#ifdef CONFIG_DEBUG_MUTEXES
1281        p->blocked_on = NULL; /* not blocked yet */
1282#endif
1283#ifdef CONFIG_MEMCG
1284        p->memcg_batch.do_batch = 0;
1285        p->memcg_batch.memcg = NULL;
1286#endif
1287
1288        /* Perform scheduler related setup. Assign this task to a CPU. */
1289        sched_fork(p);
1290
1291        retval = perf_event_init_task(p);
1292        if (retval)
1293                goto bad_fork_cleanup_policy;
1294        retval = audit_alloc(p);
1295        if (retval)
1296                goto bad_fork_cleanup_policy;
1297        /* copy all the process information */
1298        retval = copy_semundo(clone_flags, p);
1299        if (retval)
1300                goto bad_fork_cleanup_audit;
1301        retval = copy_files(clone_flags, p);
1302        if (retval)
1303                goto bad_fork_cleanup_semundo;
1304        retval = copy_fs(clone_flags, p);
1305        if (retval)
1306                goto bad_fork_cleanup_files;
1307        retval = copy_sighand(clone_flags, p);
1308        if (retval)
1309                goto bad_fork_cleanup_fs;
1310        retval = copy_signal(clone_flags, p);
1311        if (retval)
1312                goto bad_fork_cleanup_sighand;
1313        retval = copy_mm(clone_flags, p);
1314        if (retval)
1315                goto bad_fork_cleanup_signal;
1316        retval = copy_namespaces(clone_flags, p);
1317        if (retval)
1318                goto bad_fork_cleanup_mm;
1319        retval = copy_io(clone_flags, p);
1320        if (retval)
1321                goto bad_fork_cleanup_namespaces;
1322        retval = copy_thread(clone_flags, stack_start, stack_size, p, regs);
1323        if (retval)
1324                goto bad_fork_cleanup_io;
1325
1326        if (pid != &init_struct_pid) {
1327                retval = -ENOMEM;
1328                pid = alloc_pid(p->nsproxy->pid_ns);
1329                if (!pid)
1330                        goto bad_fork_cleanup_io;
1331        }
1332
1333        p->pid = pid_nr(pid);
1334        p->tgid = p->pid;
1335        if (clone_flags & CLONE_THREAD)
1336                p->tgid = current->tgid;
1337
1338        p->set_child_tid = (clone_flags & CLONE_CHILD_SETTID) ? child_tidptr : NULL;
1339        /*
1340         * Clear TID on mm_release()?
1341         */
1342        p->clear_child_tid = (clone_flags & CLONE_CHILD_CLEARTID) ? child_tidptr : NULL;
1343#ifdef CONFIG_BLOCK
1344        p->plug = NULL;
1345#endif
1346#ifdef CONFIG_FUTEX
1347        p->robust_list = NULL;
1348#ifdef CONFIG_COMPAT
1349        p->compat_robust_list = NULL;
1350#endif
1351        INIT_LIST_HEAD(&p->pi_state_list);
1352        p->pi_state_cache = NULL;
1353#endif
1354        uprobe_copy_process(p);
1355        /*
1356         * sigaltstack should be cleared when sharing the same VM
1357         */
1358        if ((clone_flags & (CLONE_VM|CLONE_VFORK)) == CLONE_VM)
1359                p->sas_ss_sp = p->sas_ss_size = 0;
1360
1361        /*
1362         * Syscall tracing and stepping should be turned off in the
1363         * child regardless of CLONE_PTRACE.
1364         */
1365        user_disable_single_step(p);
1366        clear_tsk_thread_flag(p, TIF_SYSCALL_TRACE);
1367#ifdef TIF_SYSCALL_EMU
1368        clear_tsk_thread_flag(p, TIF_SYSCALL_EMU);
1369#endif
1370        clear_all_latency_tracing(p);
1371
1372        /* ok, now we should be set up.. */
1373        if (clone_flags & CLONE_THREAD)
1374                p->exit_signal = -1;
1375        else if (clone_flags & CLONE_PARENT)
1376                p->exit_signal = current->group_leader->exit_signal;
1377        else
1378                p->exit_signal = (clone_flags & CSIGNAL);
1379
1380        p->pdeath_signal = 0;
1381        p->exit_state = 0;
1382
1383        p->nr_dirtied = 0;
1384        p->nr_dirtied_pause = 128 >> (PAGE_SHIFT - 10);
1385        p->dirty_paused_when = 0;
1386
1387        /*
1388         * Ok, make it visible to the rest of the system.
1389         * We dont wake it up yet.
1390         */
1391        p->group_leader = p;
1392        INIT_LIST_HEAD(&p->thread_group);
1393        p->task_works = NULL;
1394
1395        /* Need tasklist lock for parent etc handling! */
1396        write_lock_irq(&tasklist_lock);
1397
1398        /* CLONE_PARENT re-uses the old parent */
1399        if (clone_flags & (CLONE_PARENT|CLONE_THREAD)) {
1400                p->real_parent = current->real_parent;
1401                p->parent_exec_id = current->parent_exec_id;
1402        } else {
1403                p->real_parent = current;
1404                p->parent_exec_id = current->self_exec_id;
1405        }
1406
1407        spin_lock(&current->sighand->siglock);
1408
1409        /*
1410         * Process group and session signals need to be delivered to just the
1411         * parent before the fork or both the parent and the child after the
1412         * fork. Restart if a signal comes in before we add the new process to
1413         * it's process group.
1414         * A fatal signal pending means that current will exit, so the new
1415         * thread can't slip out of an OOM kill (or normal SIGKILL).
1416        */
1417        recalc_sigpending();
1418        if (signal_pending(current)) {
1419                spin_unlock(&current->sighand->siglock);
1420                write_unlock_irq(&tasklist_lock);
1421                retval = -ERESTARTNOINTR;
1422                goto bad_fork_free_pid;
1423        }
1424
1425        if (clone_flags & CLONE_THREAD) {
1426                current->signal->nr_threads++;
1427                atomic_inc(&current->signal->live);
1428                atomic_inc(&current->signal->sigcnt);
1429                p->group_leader = current->group_leader;
1430                list_add_tail_rcu(&p->thread_group, &p->group_leader->thread_group);
1431        }
1432
1433        if (likely(p->pid)) {
1434                ptrace_init_task(p, (clone_flags & CLONE_PTRACE) || trace);
1435
1436                if (thread_group_leader(p)) {
1437                        if (is_child_reaper(pid))
1438                                p->nsproxy->pid_ns->child_reaper = p;
1439
1440                        p->signal->leader_pid = pid;
1441                        p->signal->tty = tty_kref_get(current->signal->tty);
1442                        attach_pid(p, PIDTYPE_PGID, task_pgrp(current));
1443                        attach_pid(p, PIDTYPE_SID, task_session(current));
1444                        list_add_tail(&p->sibling, &p->real_parent->children);
1445                        list_add_tail_rcu(&p->tasks, &init_task.tasks);
1446                        __this_cpu_inc(process_counts);
1447                }
1448                attach_pid(p, PIDTYPE_PID, pid);
1449                nr_threads++;
1450        }
1451
1452        total_forks++;
1453        spin_unlock(&current->sighand->siglock);
1454        write_unlock_irq(&tasklist_lock);
1455        proc_fork_connector(p);
1456        cgroup_post_fork(p);
1457        if (clone_flags & CLONE_THREAD)
1458                threadgroup_change_end(current);
1459        perf_event_fork(p);
1460
1461        trace_task_newtask(p, clone_flags);
1462
1463        return p;
1464
1465bad_fork_free_pid:
1466        if (pid != &init_struct_pid)
1467                free_pid(pid);
1468bad_fork_cleanup_io:
1469        if (p->io_context)
1470                exit_io_context(p);
1471bad_fork_cleanup_namespaces:
1472        if (unlikely(clone_flags & CLONE_NEWPID))
1473                pid_ns_release_proc(p->nsproxy->pid_ns);
1474        exit_task_namespaces(p);
1475bad_fork_cleanup_mm:
1476        if (p->mm)
1477                mmput(p->mm);
1478bad_fork_cleanup_signal:
1479        if (!(clone_flags & CLONE_THREAD))
1480                free_signal_struct(p->signal);
1481bad_fork_cleanup_sighand:
1482        __cleanup_sighand(p->sighand);
1483bad_fork_cleanup_fs:
1484        exit_fs(p); /* blocking */
1485bad_fork_cleanup_files:
1486        exit_files(p); /* blocking */
1487bad_fork_cleanup_semundo:
1488        exit_sem(p);
1489bad_fork_cleanup_audit:
1490        audit_free(p);
1491bad_fork_cleanup_policy:
1492        perf_event_free_task(p);
1493#ifdef CONFIG_NUMA
1494        mpol_put(p->mempolicy);
1495bad_fork_cleanup_cgroup:
1496#endif
1497        if (clone_flags & CLONE_THREAD)
1498                threadgroup_change_end(current);
1499        cgroup_exit(p, 0);
1500        delayacct_tsk_free(p);
1501        module_put(task_thread_info(p)->exec_domain->module);
1502bad_fork_cleanup_count:
1503        atomic_dec(&p->cred->user->processes);
1504        exit_creds(p);
1505bad_fork_free:
1506        free_task(p);
1507fork_out:
1508        return ERR_PTR(retval);
1509}
1510
1511noinline struct pt_regs * __cpuinit __attribute__((weak)) idle_regs(struct pt_regs *regs)
1512{
1513        memset(regs, 0, sizeof(struct pt_regs));
1514        return regs;
1515}
1516
1517static inline void init_idle_pids(struct pid_link *links)
1518{
1519        enum pid_type type;
1520
1521        for (type = PIDTYPE_PID; type < PIDTYPE_MAX; ++type) {
1522                INIT_HLIST_NODE(&links[type].node); /* not really needed */
1523                links[type].pid = &init_struct_pid;
1524        }
1525}
1526
1527struct task_struct * __cpuinit fork_idle(int cpu)
1528{
1529        struct task_struct *task;
1530        struct pt_regs regs;
1531
1532        task = copy_process(CLONE_VM, 0, idle_regs(&regs), 0, NULL,
1533                            &init_struct_pid, 0);
1534        if (!IS_ERR(task)) {
1535                init_idle_pids(task->pids);
1536                init_idle(task, cpu);
1537        }
1538
1539        return task;
1540}
1541
1542/*
1543 *  Ok, this is the main fork-routine.
1544 *
1545 * It copies the process, and if successful kick-starts
1546 * it and waits for it to finish using the VM if required.
1547 */
1548long do_fork(unsigned long clone_flags,
1549              unsigned long stack_start,
1550              struct pt_regs *regs,
1551              unsigned long stack_size,
1552              int __user *parent_tidptr,
1553              int __user *child_tidptr)
1554{
1555        struct task_struct *p;
1556        int trace = 0;
1557        long nr;
1558
1559        /*
1560         * Do some preliminary argument and permissions checking before we
1561         * actually start allocating stuff
1562         */
1563        if (clone_flags & CLONE_NEWUSER) {
1564                if (clone_flags & CLONE_THREAD)
1565                        return -EINVAL;
1566                /* hopefully this check will go away when userns support is
1567                 * complete
1568                 */
1569                if (!capable(CAP_SYS_ADMIN) || !capable(CAP_SETUID) ||
1570                                !capable(CAP_SETGID))
1571                        return -EPERM;
1572        }
1573
1574        /*
1575         * Determine whether and which event to report to ptracer.  When
1576         * called from kernel_thread or CLONE_UNTRACED is explicitly
1577         * requested, no event is reported; otherwise, report if the event
1578         * for the type of forking is enabled.
1579         */
1580        if (!(clone_flags & CLONE_UNTRACED) && likely(user_mode(regs))) {
1581                if (clone_flags & CLONE_VFORK)
1582                        trace = PTRACE_EVENT_VFORK;
1583                else if ((clone_flags & CSIGNAL) != SIGCHLD)
1584                        trace = PTRACE_EVENT_CLONE;
1585                else
1586                        trace = PTRACE_EVENT_FORK;
1587
1588                if (likely(!ptrace_event_enabled(current, trace)))
1589                        trace = 0;
1590        }
1591
1592        p = copy_process(clone_flags, stack_start, regs, stack_size,
1593                         child_tidptr, NULL, trace);
1594        /*
1595         * Do this prior waking up the new thread - the thread pointer
1596         * might get invalid after that point, if the thread exits quickly.
1597         */
1598        if (!IS_ERR(p)) {
1599                struct completion vfork;
1600
1601                trace_sched_process_fork(current, p);
1602
1603                nr = task_pid_vnr(p);
1604
1605                if (clone_flags & CLONE_PARENT_SETTID)
1606                        put_user(nr, parent_tidptr);
1607
1608                if (clone_flags & CLONE_VFORK) {
1609                        p->vfork_done = &vfork;
1610                        init_completion(&vfork);
1611                        get_task_struct(p);
1612                }
1613
1614                wake_up_new_task(p);
1615
1616                /* forking complete and child started to run, tell ptracer */
1617                if (unlikely(trace))
1618                        ptrace_event(trace, nr);
1619
1620                if (clone_flags & CLONE_VFORK) {
1621                        if (!wait_for_vfork_done(p, &vfork))
1622                                ptrace_event(PTRACE_EVENT_VFORK_DONE, nr);
1623                }
1624        } else {
1625                nr = PTR_ERR(p);
1626        }
1627        return nr;
1628}
1629
1630#ifdef CONFIG_GENERIC_KERNEL_THREAD
1631/*
1632 * Create a kernel thread.
1633 */
1634pid_t kernel_thread(int (*fn)(void *), void *arg, unsigned long flags)
1635{
1636        return do_fork(flags|CLONE_VM|CLONE_UNTRACED, (unsigned long)fn, NULL,
1637                (unsigned long)arg, NULL, NULL);
1638}
1639#endif
1640
1641#ifndef ARCH_MIN_MMSTRUCT_ALIGN
1642#define ARCH_MIN_MMSTRUCT_ALIGN 0
1643#endif
1644
1645static void sighand_ctor(void *data)
1646{
1647        struct sighand_struct *sighand = data;
1648
1649        spin_lock_init(&sighand->siglock);
1650        init_waitqueue_head(&sighand->signalfd_wqh);
1651}
1652
1653void __init proc_caches_init(void)
1654{
1655        sighand_cachep = kmem_cache_create("sighand_cache",
1656                        sizeof(struct sighand_struct), 0,
1657                        SLAB_HWCACHE_ALIGN|SLAB_PANIC|SLAB_DESTROY_BY_RCU|
1658                        SLAB_NOTRACK, sighand_ctor);
1659        signal_cachep = kmem_cache_create("signal_cache",
1660                        sizeof(struct signal_struct), 0,
1661                        SLAB_HWCACHE_ALIGN|SLAB_PANIC|SLAB_NOTRACK, NULL);
1662        files_cachep = kmem_cache_create("files_cache",
1663                        sizeof(struct files_struct), 0,
1664                        SLAB_HWCACHE_ALIGN|SLAB_PANIC|SLAB_NOTRACK, NULL);
1665        fs_cachep = kmem_cache_create("fs_cache",
1666                        sizeof(struct fs_struct), 0,
1667                        SLAB_HWCACHE_ALIGN|SLAB_PANIC|SLAB_NOTRACK, NULL);
1668        /*
1669         * FIXME! The "sizeof(struct mm_struct)" currently includes the
1670         * whole struct cpumask for the OFFSTACK case. We could change
1671         * this to *only* allocate as much of it as required by the
1672         * maximum number of CPU's we can ever have.  The cpumask_allocation
1673         * is at the end of the structure, exactly for that reason.
1674         */
1675        mm_cachep = kmem_cache_create("mm_struct",
1676                        sizeof(struct mm_struct), ARCH_MIN_MMSTRUCT_ALIGN,
1677                        SLAB_HWCACHE_ALIGN|SLAB_PANIC|SLAB_NOTRACK, NULL);
1678        vm_area_cachep = KMEM_CACHE(vm_area_struct, SLAB_PANIC);
1679        mmap_init();
1680        nsproxy_cache_init();
1681}
1682
1683/*
1684 * Check constraints on flags passed to the unshare system call.
1685 */
1686static int check_unshare_flags(unsigned long unshare_flags)
1687{
1688        if (unshare_flags & ~(CLONE_THREAD|CLONE_FS|CLONE_NEWNS|CLONE_SIGHAND|
1689                                CLONE_VM|CLONE_FILES|CLONE_SYSVSEM|
1690                                CLONE_NEWUTS|CLONE_NEWIPC|CLONE_NEWNET))
1691                return -EINVAL;
1692        /*
1693         * Not implemented, but pretend it works if there is nothing to
1694         * unshare. Note that unsharing CLONE_THREAD or CLONE_SIGHAND
1695         * needs to unshare vm.
1696         */
1697        if (unshare_flags & (CLONE_THREAD | CLONE_SIGHAND | CLONE_VM)) {
1698                /* FIXME: get_task_mm() increments ->mm_users */
1699                if (atomic_read(&current->mm->mm_users) > 1)
1700                        return -EINVAL;
1701        }
1702
1703        return 0;
1704}
1705
1706/*
1707 * Unshare the filesystem structure if it is being shared
1708 */
1709static int unshare_fs(unsigned long unshare_flags, struct fs_struct **new_fsp)
1710{
1711        struct fs_struct *fs = current->fs;
1712
1713        if (!(unshare_flags & CLONE_FS) || !fs)
1714                return 0;
1715
1716        /* don't need lock here; in the worst case we'll do useless copy */
1717        if (fs->users == 1)
1718                return 0;
1719
1720        *new_fsp = copy_fs_struct(fs);
1721        if (!*new_fsp)
1722                return -ENOMEM;
1723
1724        return 0;
1725}
1726
1727/*
1728 * Unshare file descriptor table if it is being shared
1729 */
1730static int unshare_fd(unsigned long unshare_flags, struct files_struct **new_fdp)
1731{
1732        struct files_struct *fd = current->files;
1733        int error = 0;
1734
1735        if ((unshare_flags & CLONE_FILES) &&
1736            (fd && atomic_read(&fd->count) > 1)) {
1737                *new_fdp = dup_fd(fd, &error);
1738                if (!*new_fdp)
1739                        return error;
1740        }
1741
1742        return 0;
1743}
1744
1745/*
1746 * unshare allows a process to 'unshare' part of the process
1747 * context which was originally shared using clone.  copy_*
1748 * functions used by do_fork() cannot be used here directly
1749 * because they modify an inactive task_struct that is being
1750 * constructed. Here we are modifying the current, active,
1751 * task_struct.
1752 */
1753SYSCALL_DEFINE1(unshare, unsigned long, unshare_flags)
1754{
1755        struct fs_struct *fs, *new_fs = NULL;
1756        struct files_struct *fd, *new_fd = NULL;
1757        struct nsproxy *new_nsproxy = NULL;
1758        int do_sysvsem = 0;
1759        int err;
1760
1761        err = check_unshare_flags(unshare_flags);
1762        if (err)
1763                goto bad_unshare_out;
1764
1765        /*
1766         * If unsharing namespace, must also unshare filesystem information.
1767         */
1768        if (unshare_flags & CLONE_NEWNS)
1769                unshare_flags |= CLONE_FS;
1770        /*
1771         * CLONE_NEWIPC must also detach from the undolist: after switching
1772         * to a new ipc namespace, the semaphore arrays from the old
1773         * namespace are unreachable.
1774         */
1775        if (unshare_flags & (CLONE_NEWIPC|CLONE_SYSVSEM))
1776                do_sysvsem = 1;
1777        err = unshare_fs(unshare_flags, &new_fs);
1778        if (err)
1779                goto bad_unshare_out;
1780        err = unshare_fd(unshare_flags, &new_fd);
1781        if (err)
1782                goto bad_unshare_cleanup_fs;
1783        err = unshare_nsproxy_namespaces(unshare_flags, &new_nsproxy, new_fs);
1784        if (err)
1785                goto bad_unshare_cleanup_fd;
1786
1787        if (new_fs || new_fd || do_sysvsem || new_nsproxy) {
1788                if (do_sysvsem) {
1789                        /*
1790                         * CLONE_SYSVSEM is equivalent to sys_exit().
1791                         */
1792                        exit_sem(current);
1793                }
1794
1795                if (new_nsproxy) {
1796                        switch_task_namespaces(current, new_nsproxy);
1797                        new_nsproxy = NULL;
1798                }
1799
1800                task_lock(current);
1801
1802                if (new_fs) {
1803                        fs = current->fs;
1804                        spin_lock(&fs->lock);
1805                        current->fs = new_fs;
1806                        if (--fs->users)
1807                                new_fs = NULL;
1808                        else
1809                                new_fs = fs;
1810                        spin_unlock(&fs->lock);
1811                }
1812
1813                if (new_fd) {
1814                        fd = current->files;
1815                        current->files = new_fd;
1816                        new_fd = fd;
1817                }
1818
1819                task_unlock(current);
1820        }
1821
1822        if (new_nsproxy)
1823                put_nsproxy(new_nsproxy);
1824
1825bad_unshare_cleanup_fd:
1826        if (new_fd)
1827                put_files_struct(new_fd);
1828
1829bad_unshare_cleanup_fs:
1830        if (new_fs)
1831                free_fs_struct(new_fs);
1832
1833bad_unshare_out:
1834        return err;
1835}
1836
1837/*
1838 *      Helper to unshare the files of the current task.
1839 *      We don't want to expose copy_files internals to
1840 *      the exec layer of the kernel.
1841 */
1842
1843int unshare_files(struct files_struct **displaced)
1844{
1845        struct task_struct *task = current;
1846        struct files_struct *copy = NULL;
1847        int error;
1848
1849        error = unshare_fd(CLONE_FILES, &copy);
1850        if (error || !copy) {
1851                *displaced = NULL;
1852                return error;
1853        }
1854        *displaced = task->files;
1855        task_lock(task);
1856        task->files = copy;
1857        task_unlock(task);
1858        return 0;
1859}
1860
lxr.linux.no kindly hosted by Redpill Linpro AS, provider of Linux consulting and operations services since 1995.