4 * Copyright (C) 1991, 1992 Linus Torvalds
8 * 'fork.c' contains the help-routines for the 'fork' system call
9 * (see also entry.S and others).
10 * Fork is rather simple, once you get the hang of it, but the memory
11 * management can be a bitch. See 'mm/memory.c': 'copy_page_range()'
14 #include <linux/slab.h>
15 #include <linux/init.h>
16 #include <linux/unistd.h>
17 #include <linux/module.h>
18 #include <linux/vmalloc.h>
19 #include <linux/completion.h>
20 #include <linux/personality.h>
21 #include <linux/mempolicy.h>
22 #include <linux/sem.h>
23 #include <linux/file.h>
24 #include <linux/fdtable.h>
25 #include <linux/iocontext.h>
26 #include <linux/key.h>
27 #include <linux/binfmts.h>
28 #include <linux/mman.h>
29 #include <linux/mmu_notifier.h>
32 #include <linux/vmacache.h>
33 #include <linux/nsproxy.h>
34 #include <linux/capability.h>
35 #include <linux/cpu.h>
36 #include <linux/cgroup.h>
37 #include <linux/security.h>
38 #include <linux/hugetlb.h>
39 #include <linux/seccomp.h>
40 #include <linux/swap.h>
41 #include <linux/syscalls.h>
42 #include <linux/jiffies.h>
43 #include <linux/futex.h>
44 #include <linux/compat.h>
45 #include <linux/kthread.h>
46 #include <linux/task_io_accounting_ops.h>
47 #include <linux/rcupdate.h>
48 #include <linux/ptrace.h>
49 #include <linux/mount.h>
50 #include <linux/audit.h>
51 #include <linux/memcontrol.h>
52 #include <linux/ftrace.h>
53 #include <linux/proc_fs.h>
54 #include <linux/profile.h>
55 #include <linux/rmap.h>
56 #include <linux/ksm.h>
57 #include <linux/acct.h>
58 #include <linux/tsacct_kern.h>
59 #include <linux/cn_proc.h>
60 #include <linux/freezer.h>
61 #include <linux/delayacct.h>
62 #include <linux/taskstats_kern.h>
63 #include <linux/random.h>
64 #include <linux/tty.h>
65 #include <linux/blkdev.h>
66 #include <linux/fs_struct.h>
67 #include <linux/magic.h>
68 #include <linux/perf_event.h>
69 #include <linux/posix-timers.h>
70 #include <linux/user-return-notifier.h>
71 #include <linux/oom.h>
72 #include <linux/khugepaged.h>
73 #include <linux/signalfd.h>
74 #include <linux/uprobes.h>
75 #include <linux/aio.h>
76 #include <linux/compiler.h>
77 #include <linux/sysctl.h>
79 #include <asm/pgtable.h>
80 #include <asm/pgalloc.h>
81 #include <asm/uaccess.h>
82 #include <asm/mmu_context.h>
83 #include <asm/cacheflush.h>
84 #include <asm/tlbflush.h>
86 #include <trace/events/sched.h>
88 #define CREATE_TRACE_POINTS
89 #include <trace/events/task.h>
92 * Minimum number of threads to boot the kernel
94 #define MIN_THREADS 20
97 * Maximum number of threads
99 #define MAX_THREADS FUTEX_TID_MASK
102 * Protected counters by write_lock_irq(&tasklist_lock)
104 unsigned long total_forks
; /* Handle normal Linux uptimes. */
105 int nr_threads
; /* The idle threads do not count.. */
107 int max_threads
; /* tunable limit on nr_threads */
109 DEFINE_PER_CPU(unsigned long, process_counts
) = 0;
111 __cacheline_aligned
DEFINE_RWLOCK(tasklist_lock
); /* outer */
113 #ifdef CONFIG_PROVE_RCU
114 int lockdep_tasklist_lock_is_held(void)
116 return lockdep_is_held(&tasklist_lock
);
118 EXPORT_SYMBOL_GPL(lockdep_tasklist_lock_is_held
);
119 #endif /* #ifdef CONFIG_PROVE_RCU */
121 int nr_processes(void)
126 for_each_possible_cpu(cpu
)
127 total
+= per_cpu(process_counts
, cpu
);
132 void __weak
arch_release_task_struct(struct task_struct
*tsk
)
136 #ifndef CONFIG_ARCH_TASK_STRUCT_ALLOCATOR
137 static struct kmem_cache
*task_struct_cachep
;
139 static inline struct task_struct
*alloc_task_struct_node(int node
)
141 return kmem_cache_alloc_node(task_struct_cachep
, GFP_KERNEL
, node
);
144 static inline void free_task_struct(struct task_struct
*tsk
)
146 kmem_cache_free(task_struct_cachep
, tsk
);
150 void __weak
arch_release_thread_info(struct thread_info
*ti
)
154 #ifndef CONFIG_ARCH_THREAD_INFO_ALLOCATOR
157 * Allocate pages if THREAD_SIZE is >= PAGE_SIZE, otherwise use a
158 * kmemcache based allocator.
160 # if THREAD_SIZE >= PAGE_SIZE
161 static struct thread_info
*alloc_thread_info_node(struct task_struct
*tsk
,
164 struct page
*page
= alloc_kmem_pages_node(node
, THREADINFO_GFP
,
168 memcg_kmem_update_page_stat(page
, MEMCG_KERNEL_STACK
,
169 1 << THREAD_SIZE_ORDER
);
171 return page
? page_address(page
) : NULL
;
174 static inline void free_thread_info(struct thread_info
*ti
)
176 struct page
*page
= virt_to_page(ti
);
178 memcg_kmem_update_page_stat(page
, MEMCG_KERNEL_STACK
,
179 -(1 << THREAD_SIZE_ORDER
));
180 __free_kmem_pages(page
, THREAD_SIZE_ORDER
);
183 static struct kmem_cache
*thread_info_cache
;
185 static struct thread_info
*alloc_thread_info_node(struct task_struct
*tsk
,
188 return kmem_cache_alloc_node(thread_info_cache
, THREADINFO_GFP
, node
);
191 static void free_thread_info(struct thread_info
*ti
)
193 kmem_cache_free(thread_info_cache
, ti
);
196 void thread_info_cache_init(void)
198 thread_info_cache
= kmem_cache_create("thread_info", THREAD_SIZE
,
199 THREAD_SIZE
, 0, NULL
);
200 BUG_ON(thread_info_cache
== NULL
);
205 /* SLAB cache for signal_struct structures (tsk->signal) */
206 static struct kmem_cache
*signal_cachep
;
208 /* SLAB cache for sighand_struct structures (tsk->sighand) */
209 struct kmem_cache
*sighand_cachep
;
211 /* SLAB cache for files_struct structures (tsk->files) */
212 struct kmem_cache
*files_cachep
;
214 /* SLAB cache for fs_struct structures (tsk->fs) */
215 struct kmem_cache
*fs_cachep
;
217 /* SLAB cache for vm_area_struct structures */
218 struct kmem_cache
*vm_area_cachep
;
220 /* SLAB cache for mm_struct structures (tsk->mm) */
221 static struct kmem_cache
*mm_cachep
;
223 static void account_kernel_stack(struct thread_info
*ti
, int account
)
225 struct zone
*zone
= page_zone(virt_to_page(ti
));
227 mod_zone_page_state(zone
, NR_KERNEL_STACK
, account
);
230 void free_task(struct task_struct
*tsk
)
232 account_kernel_stack(tsk
->stack
, -1);
233 arch_release_thread_info(tsk
->stack
);
234 free_thread_info(tsk
->stack
);
235 rt_mutex_debug_task_free(tsk
);
236 ftrace_graph_exit_task(tsk
);
237 put_seccomp_filter(tsk
);
238 arch_release_task_struct(tsk
);
239 free_task_struct(tsk
);
241 EXPORT_SYMBOL(free_task
);
243 static inline void free_signal_struct(struct signal_struct
*sig
)
245 taskstats_tgid_free(sig
);
246 sched_autogroup_exit(sig
);
247 kmem_cache_free(signal_cachep
, sig
);
250 static inline void put_signal_struct(struct signal_struct
*sig
)
252 if (atomic_dec_and_test(&sig
->sigcnt
))
253 free_signal_struct(sig
);
256 void __put_task_struct(struct task_struct
*tsk
)
258 WARN_ON(!tsk
->exit_state
);
259 WARN_ON(atomic_read(&tsk
->usage
));
260 WARN_ON(tsk
== current
);
264 security_task_free(tsk
);
266 delayacct_tsk_free(tsk
);
267 put_signal_struct(tsk
->signal
);
269 if (!profile_handoff_task(tsk
))
272 EXPORT_SYMBOL_GPL(__put_task_struct
);
274 void __init __weak
arch_task_cache_init(void) { }
279 static void set_max_threads(unsigned int max_threads_suggested
)
284 * The number of threads shall be limited such that the thread
285 * structures may only consume a small part of the available memory.
287 if (fls64(totalram_pages
) + fls64(PAGE_SIZE
) > 64)
288 threads
= MAX_THREADS
;
290 threads
= div64_u64((u64
) totalram_pages
* (u64
) PAGE_SIZE
,
291 (u64
) THREAD_SIZE
* 8UL);
293 if (threads
> max_threads_suggested
)
294 threads
= max_threads_suggested
;
296 max_threads
= clamp_t(u64
, threads
, MIN_THREADS
, MAX_THREADS
);
299 #ifdef CONFIG_ARCH_WANTS_DYNAMIC_TASK_STRUCT
300 /* Initialized by the architecture: */
301 int arch_task_struct_size __read_mostly
;
304 void __init
fork_init(void)
306 #ifndef CONFIG_ARCH_TASK_STRUCT_ALLOCATOR
307 #ifndef ARCH_MIN_TASKALIGN
308 #define ARCH_MIN_TASKALIGN L1_CACHE_BYTES
310 /* create a slab on which task_structs can be allocated */
311 task_struct_cachep
= kmem_cache_create("task_struct",
312 arch_task_struct_size
, ARCH_MIN_TASKALIGN
,
313 SLAB_PANIC
|SLAB_NOTRACK
|SLAB_ACCOUNT
, NULL
);
316 /* do the arch specific task caches init */
317 arch_task_cache_init();
319 set_max_threads(MAX_THREADS
);
321 init_task
.signal
->rlim
[RLIMIT_NPROC
].rlim_cur
= max_threads
/2;
322 init_task
.signal
->rlim
[RLIMIT_NPROC
].rlim_max
= max_threads
/2;
323 init_task
.signal
->rlim
[RLIMIT_SIGPENDING
] =
324 init_task
.signal
->rlim
[RLIMIT_NPROC
];
327 int __weak
arch_dup_task_struct(struct task_struct
*dst
,
328 struct task_struct
*src
)
334 void set_task_stack_end_magic(struct task_struct
*tsk
)
336 unsigned long *stackend
;
338 stackend
= end_of_stack(tsk
);
339 *stackend
= STACK_END_MAGIC
; /* for overflow detection */
342 static struct task_struct
*dup_task_struct(struct task_struct
*orig
)
344 struct task_struct
*tsk
;
345 struct thread_info
*ti
;
346 int node
= tsk_fork_get_node(orig
);
349 tsk
= alloc_task_struct_node(node
);
353 ti
= alloc_thread_info_node(tsk
, node
);
357 err
= arch_dup_task_struct(tsk
, orig
);
362 #ifdef CONFIG_SECCOMP
364 * We must handle setting up seccomp filters once we're under
365 * the sighand lock in case orig has changed between now and
366 * then. Until then, filter must be NULL to avoid messing up
367 * the usage counts on the error path calling free_task.
369 tsk
->seccomp
.filter
= NULL
;
372 setup_thread_stack(tsk
, orig
);
373 clear_user_return_notifier(tsk
);
374 clear_tsk_need_resched(tsk
);
375 set_task_stack_end_magic(tsk
);
377 #ifdef CONFIG_CC_STACKPROTECTOR
378 tsk
->stack_canary
= get_random_int();
382 * One for us, one for whoever does the "release_task()" (usually
385 atomic_set(&tsk
->usage
, 2);
386 #ifdef CONFIG_BLK_DEV_IO_TRACE
389 tsk
->splice_pipe
= NULL
;
390 tsk
->task_frag
.page
= NULL
;
391 tsk
->wake_q
.next
= NULL
;
393 account_kernel_stack(ti
, 1);
398 free_thread_info(ti
);
400 free_task_struct(tsk
);
405 static int dup_mmap(struct mm_struct
*mm
, struct mm_struct
*oldmm
)
407 struct vm_area_struct
*mpnt
, *tmp
, *prev
, **pprev
;
408 struct rb_node
**rb_link
, *rb_parent
;
410 unsigned long charge
;
412 uprobe_start_dup_mmap();
413 down_write(&oldmm
->mmap_sem
);
414 flush_cache_dup_mm(oldmm
);
415 uprobe_dup_mmap(oldmm
, mm
);
417 * Not linked in yet - no deadlock potential:
419 down_write_nested(&mm
->mmap_sem
, SINGLE_DEPTH_NESTING
);
421 /* No ordering required: file already has been exposed. */
422 RCU_INIT_POINTER(mm
->exe_file
, get_mm_exe_file(oldmm
));
424 mm
->total_vm
= oldmm
->total_vm
;
425 mm
->data_vm
= oldmm
->data_vm
;
426 mm
->exec_vm
= oldmm
->exec_vm
;
427 mm
->stack_vm
= oldmm
->stack_vm
;
429 rb_link
= &mm
->mm_rb
.rb_node
;
432 retval
= ksm_fork(mm
, oldmm
);
435 retval
= khugepaged_fork(mm
, oldmm
);
440 for (mpnt
= oldmm
->mmap
; mpnt
; mpnt
= mpnt
->vm_next
) {
443 if (mpnt
->vm_flags
& VM_DONTCOPY
) {
444 vm_stat_account(mm
, mpnt
->vm_flags
, -vma_pages(mpnt
));
448 if (mpnt
->vm_flags
& VM_ACCOUNT
) {
449 unsigned long len
= vma_pages(mpnt
);
451 if (security_vm_enough_memory_mm(oldmm
, len
)) /* sic */
455 tmp
= kmem_cache_alloc(vm_area_cachep
, GFP_KERNEL
);
459 INIT_LIST_HEAD(&tmp
->anon_vma_chain
);
460 retval
= vma_dup_policy(mpnt
, tmp
);
462 goto fail_nomem_policy
;
464 if (anon_vma_fork(tmp
, mpnt
))
465 goto fail_nomem_anon_vma_fork
;
467 ~(VM_LOCKED
|VM_LOCKONFAULT
|VM_UFFD_MISSING
|VM_UFFD_WP
);
468 tmp
->vm_next
= tmp
->vm_prev
= NULL
;
469 tmp
->vm_userfaultfd_ctx
= NULL_VM_UFFD_CTX
;
472 struct inode
*inode
= file_inode(file
);
473 struct address_space
*mapping
= file
->f_mapping
;
476 if (tmp
->vm_flags
& VM_DENYWRITE
)
477 atomic_dec(&inode
->i_writecount
);
478 i_mmap_lock_write(mapping
);
479 if (tmp
->vm_flags
& VM_SHARED
)
480 atomic_inc(&mapping
->i_mmap_writable
);
481 flush_dcache_mmap_lock(mapping
);
482 /* insert tmp into the share list, just after mpnt */
483 vma_interval_tree_insert_after(tmp
, mpnt
,
485 flush_dcache_mmap_unlock(mapping
);
486 i_mmap_unlock_write(mapping
);
490 * Clear hugetlb-related page reserves for children. This only
491 * affects MAP_PRIVATE mappings. Faults generated by the child
492 * are not guaranteed to succeed, even if read-only
494 if (is_vm_hugetlb_page(tmp
))
495 reset_vma_resv_huge_pages(tmp
);
498 * Link in the new vma and copy the page table entries.
501 pprev
= &tmp
->vm_next
;
505 __vma_link_rb(mm
, tmp
, rb_link
, rb_parent
);
506 rb_link
= &tmp
->vm_rb
.rb_right
;
507 rb_parent
= &tmp
->vm_rb
;
510 retval
= copy_page_range(mm
, oldmm
, mpnt
);
512 if (tmp
->vm_ops
&& tmp
->vm_ops
->open
)
513 tmp
->vm_ops
->open(tmp
);
518 /* a new mm has just been created */
519 arch_dup_mmap(oldmm
, mm
);
522 up_write(&mm
->mmap_sem
);
524 up_write(&oldmm
->mmap_sem
);
525 uprobe_end_dup_mmap();
527 fail_nomem_anon_vma_fork
:
528 mpol_put(vma_policy(tmp
));
530 kmem_cache_free(vm_area_cachep
, tmp
);
533 vm_unacct_memory(charge
);
537 static inline int mm_alloc_pgd(struct mm_struct
*mm
)
539 mm
->pgd
= pgd_alloc(mm
);
540 if (unlikely(!mm
->pgd
))
545 static inline void mm_free_pgd(struct mm_struct
*mm
)
547 pgd_free(mm
, mm
->pgd
);
550 static int dup_mmap(struct mm_struct
*mm
, struct mm_struct
*oldmm
)
552 down_write(&oldmm
->mmap_sem
);
553 RCU_INIT_POINTER(mm
->exe_file
, get_mm_exe_file(oldmm
));
554 up_write(&oldmm
->mmap_sem
);
557 #define mm_alloc_pgd(mm) (0)
558 #define mm_free_pgd(mm)
559 #endif /* CONFIG_MMU */
561 __cacheline_aligned_in_smp
DEFINE_SPINLOCK(mmlist_lock
);
563 #define allocate_mm() (kmem_cache_alloc(mm_cachep, GFP_KERNEL))
564 #define free_mm(mm) (kmem_cache_free(mm_cachep, (mm)))
566 static unsigned long default_dump_filter
= MMF_DUMP_FILTER_DEFAULT
;
568 static int __init
coredump_filter_setup(char *s
)
570 default_dump_filter
=
571 (simple_strtoul(s
, NULL
, 0) << MMF_DUMP_FILTER_SHIFT
) &
572 MMF_DUMP_FILTER_MASK
;
576 __setup("coredump_filter=", coredump_filter_setup
);
578 #include <linux/init_task.h>
580 static void mm_init_aio(struct mm_struct
*mm
)
583 spin_lock_init(&mm
->ioctx_lock
);
584 mm
->ioctx_table
= NULL
;
588 static void mm_init_owner(struct mm_struct
*mm
, struct task_struct
*p
)
595 static struct mm_struct
*mm_init(struct mm_struct
*mm
, struct task_struct
*p
)
599 mm
->vmacache_seqnum
= 0;
600 atomic_set(&mm
->mm_users
, 1);
601 atomic_set(&mm
->mm_count
, 1);
602 init_rwsem(&mm
->mmap_sem
);
603 INIT_LIST_HEAD(&mm
->mmlist
);
604 mm
->core_state
= NULL
;
605 atomic_long_set(&mm
->nr_ptes
, 0);
610 memset(&mm
->rss_stat
, 0, sizeof(mm
->rss_stat
));
611 spin_lock_init(&mm
->page_table_lock
);
614 mm_init_owner(mm
, p
);
615 mmu_notifier_mm_init(mm
);
616 clear_tlb_flush_pending(mm
);
617 #if defined(CONFIG_TRANSPARENT_HUGEPAGE) && !USE_SPLIT_PMD_PTLOCKS
618 mm
->pmd_huge_pte
= NULL
;
622 mm
->flags
= current
->mm
->flags
& MMF_INIT_MASK
;
623 mm
->def_flags
= current
->mm
->def_flags
& VM_INIT_DEF_MASK
;
625 mm
->flags
= default_dump_filter
;
629 if (mm_alloc_pgd(mm
))
632 if (init_new_context(p
, mm
))
644 static void check_mm(struct mm_struct
*mm
)
648 for (i
= 0; i
< NR_MM_COUNTERS
; i
++) {
649 long x
= atomic_long_read(&mm
->rss_stat
.count
[i
]);
652 printk(KERN_ALERT
"BUG: Bad rss-counter state "
653 "mm:%p idx:%d val:%ld\n", mm
, i
, x
);
656 if (atomic_long_read(&mm
->nr_ptes
))
657 pr_alert("BUG: non-zero nr_ptes on freeing mm: %ld\n",
658 atomic_long_read(&mm
->nr_ptes
));
660 pr_alert("BUG: non-zero nr_pmds on freeing mm: %ld\n",
663 #if defined(CONFIG_TRANSPARENT_HUGEPAGE) && !USE_SPLIT_PMD_PTLOCKS
664 VM_BUG_ON_MM(mm
->pmd_huge_pte
, mm
);
669 * Allocate and initialize an mm_struct.
671 struct mm_struct
*mm_alloc(void)
673 struct mm_struct
*mm
;
679 memset(mm
, 0, sizeof(*mm
));
680 return mm_init(mm
, current
);
684 * Called when the last reference to the mm
685 * is dropped: either by a lazy thread or by
686 * mmput. Free the page directory and the mm.
688 void __mmdrop(struct mm_struct
*mm
)
690 BUG_ON(mm
== &init_mm
);
693 mmu_notifier_mm_destroy(mm
);
697 EXPORT_SYMBOL_GPL(__mmdrop
);
700 * Decrement the use count and release all resources for an mm.
702 void mmput(struct mm_struct
*mm
)
706 if (atomic_dec_and_test(&mm
->mm_users
)) {
707 uprobe_clear_state(mm
);
710 khugepaged_exit(mm
); /* must run before exit_mmap */
712 set_mm_exe_file(mm
, NULL
);
713 if (!list_empty(&mm
->mmlist
)) {
714 spin_lock(&mmlist_lock
);
715 list_del(&mm
->mmlist
);
716 spin_unlock(&mmlist_lock
);
719 module_put(mm
->binfmt
->module
);
723 EXPORT_SYMBOL_GPL(mmput
);
726 * set_mm_exe_file - change a reference to the mm's executable file
728 * This changes mm's executable file (shown as symlink /proc/[pid]/exe).
730 * Main users are mmput() and sys_execve(). Callers prevent concurrent
731 * invocations: in mmput() nobody alive left, in execve task is single
732 * threaded. sys_prctl(PR_SET_MM_MAP/EXE_FILE) also needs to set the
733 * mm->exe_file, but does so without using set_mm_exe_file() in order
734 * to do avoid the need for any locks.
736 void set_mm_exe_file(struct mm_struct
*mm
, struct file
*new_exe_file
)
738 struct file
*old_exe_file
;
741 * It is safe to dereference the exe_file without RCU as
742 * this function is only called if nobody else can access
743 * this mm -- see comment above for justification.
745 old_exe_file
= rcu_dereference_raw(mm
->exe_file
);
748 get_file(new_exe_file
);
749 rcu_assign_pointer(mm
->exe_file
, new_exe_file
);
755 * get_mm_exe_file - acquire a reference to the mm's executable file
757 * Returns %NULL if mm has no associated executable file.
758 * User must release file via fput().
760 struct file
*get_mm_exe_file(struct mm_struct
*mm
)
762 struct file
*exe_file
;
765 exe_file
= rcu_dereference(mm
->exe_file
);
766 if (exe_file
&& !get_file_rcu(exe_file
))
771 EXPORT_SYMBOL(get_mm_exe_file
);
774 * get_task_mm - acquire a reference to the task's mm
776 * Returns %NULL if the task has no mm. Checks PF_KTHREAD (meaning
777 * this kernel workthread has transiently adopted a user mm with use_mm,
778 * to do its AIO) is not set and if so returns a reference to it, after
779 * bumping up the use count. User must release the mm via mmput()
780 * after use. Typically used by /proc and ptrace.
782 struct mm_struct
*get_task_mm(struct task_struct
*task
)
784 struct mm_struct
*mm
;
789 if (task
->flags
& PF_KTHREAD
)
792 atomic_inc(&mm
->mm_users
);
797 EXPORT_SYMBOL_GPL(get_task_mm
);
799 struct mm_struct
*mm_access(struct task_struct
*task
, unsigned int mode
)
801 struct mm_struct
*mm
;
804 err
= mutex_lock_killable(&task
->signal
->cred_guard_mutex
);
808 mm
= get_task_mm(task
);
809 if (mm
&& mm
!= current
->mm
&&
810 !ptrace_may_access(task
, mode
)) {
812 mm
= ERR_PTR(-EACCES
);
814 mutex_unlock(&task
->signal
->cred_guard_mutex
);
819 static void complete_vfork_done(struct task_struct
*tsk
)
821 struct completion
*vfork
;
824 vfork
= tsk
->vfork_done
;
826 tsk
->vfork_done
= NULL
;
832 static int wait_for_vfork_done(struct task_struct
*child
,
833 struct completion
*vfork
)
837 freezer_do_not_count();
838 killed
= wait_for_completion_killable(vfork
);
843 child
->vfork_done
= NULL
;
847 put_task_struct(child
);
851 /* Please note the differences between mmput and mm_release.
852 * mmput is called whenever we stop holding onto a mm_struct,
853 * error success whatever.
855 * mm_release is called after a mm_struct has been removed
856 * from the current process.
858 * This difference is important for error handling, when we
859 * only half set up a mm_struct for a new process and need to restore
860 * the old one. Because we mmput the new mm_struct before
861 * restoring the old one. . .
862 * Eric Biederman 10 January 1998
864 void mm_release(struct task_struct
*tsk
, struct mm_struct
*mm
)
866 /* Get rid of any futexes when releasing the mm */
868 if (unlikely(tsk
->robust_list
)) {
869 exit_robust_list(tsk
);
870 tsk
->robust_list
= NULL
;
873 if (unlikely(tsk
->compat_robust_list
)) {
874 compat_exit_robust_list(tsk
);
875 tsk
->compat_robust_list
= NULL
;
878 if (unlikely(!list_empty(&tsk
->pi_state_list
)))
879 exit_pi_state_list(tsk
);
882 uprobe_free_utask(tsk
);
884 /* Get rid of any cached register state */
885 deactivate_mm(tsk
, mm
);
888 * If we're exiting normally, clear a user-space tid field if
889 * requested. We leave this alone when dying by signal, to leave
890 * the value intact in a core dump, and to save the unnecessary
891 * trouble, say, a killed vfork parent shouldn't touch this mm.
892 * Userland only wants this done for a sys_exit.
894 if (tsk
->clear_child_tid
) {
895 if (!(tsk
->flags
& PF_SIGNALED
) &&
896 atomic_read(&mm
->mm_users
) > 1) {
898 * We don't check the error code - if userspace has
899 * not set up a proper pointer then tough luck.
901 put_user(0, tsk
->clear_child_tid
);
902 sys_futex(tsk
->clear_child_tid
, FUTEX_WAKE
,
905 tsk
->clear_child_tid
= NULL
;
909 * All done, finally we can wake up parent and return this mm to him.
910 * Also kthread_stop() uses this completion for synchronization.
913 complete_vfork_done(tsk
);
917 * Allocate a new mm structure and copy contents from the
918 * mm structure of the passed in task structure.
920 static struct mm_struct
*dup_mm(struct task_struct
*tsk
)
922 struct mm_struct
*mm
, *oldmm
= current
->mm
;
929 memcpy(mm
, oldmm
, sizeof(*mm
));
931 if (!mm_init(mm
, tsk
))
934 err
= dup_mmap(mm
, oldmm
);
938 mm
->hiwater_rss
= get_mm_rss(mm
);
939 mm
->hiwater_vm
= mm
->total_vm
;
941 if (mm
->binfmt
&& !try_module_get(mm
->binfmt
->module
))
947 /* don't put binfmt in mmput, we haven't got module yet */
955 static int copy_mm(unsigned long clone_flags
, struct task_struct
*tsk
)
957 struct mm_struct
*mm
, *oldmm
;
960 tsk
->min_flt
= tsk
->maj_flt
= 0;
961 tsk
->nvcsw
= tsk
->nivcsw
= 0;
962 #ifdef CONFIG_DETECT_HUNG_TASK
963 tsk
->last_switch_count
= tsk
->nvcsw
+ tsk
->nivcsw
;
967 tsk
->active_mm
= NULL
;
970 * Are we cloning a kernel thread?
972 * We need to steal a active VM for that..
978 /* initialize the new vmacache entries */
981 if (clone_flags
& CLONE_VM
) {
982 atomic_inc(&oldmm
->mm_users
);
1001 static int copy_fs(unsigned long clone_flags
, struct task_struct
*tsk
)
1003 struct fs_struct
*fs
= current
->fs
;
1004 if (clone_flags
& CLONE_FS
) {
1005 /* tsk->fs is already what we want */
1006 spin_lock(&fs
->lock
);
1008 spin_unlock(&fs
->lock
);
1012 spin_unlock(&fs
->lock
);
1015 tsk
->fs
= copy_fs_struct(fs
);
1021 static int copy_files(unsigned long clone_flags
, struct task_struct
*tsk
)
1023 struct files_struct
*oldf
, *newf
;
1027 * A background process may not have any files ...
1029 oldf
= current
->files
;
1033 if (clone_flags
& CLONE_FILES
) {
1034 atomic_inc(&oldf
->count
);
1038 newf
= dup_fd(oldf
, &error
);
1048 static int copy_io(unsigned long clone_flags
, struct task_struct
*tsk
)
1051 struct io_context
*ioc
= current
->io_context
;
1052 struct io_context
*new_ioc
;
1057 * Share io context with parent, if CLONE_IO is set
1059 if (clone_flags
& CLONE_IO
) {
1061 tsk
->io_context
= ioc
;
1062 } else if (ioprio_valid(ioc
->ioprio
)) {
1063 new_ioc
= get_task_io_context(tsk
, GFP_KERNEL
, NUMA_NO_NODE
);
1064 if (unlikely(!new_ioc
))
1067 new_ioc
->ioprio
= ioc
->ioprio
;
1068 put_io_context(new_ioc
);
1074 static int copy_sighand(unsigned long clone_flags
, struct task_struct
*tsk
)
1076 struct sighand_struct
*sig
;
1078 if (clone_flags
& CLONE_SIGHAND
) {
1079 atomic_inc(¤t
->sighand
->count
);
1082 sig
= kmem_cache_alloc(sighand_cachep
, GFP_KERNEL
);
1083 rcu_assign_pointer(tsk
->sighand
, sig
);
1087 atomic_set(&sig
->count
, 1);
1088 memcpy(sig
->action
, current
->sighand
->action
, sizeof(sig
->action
));
1092 void __cleanup_sighand(struct sighand_struct
*sighand
)
1094 if (atomic_dec_and_test(&sighand
->count
)) {
1095 signalfd_cleanup(sighand
);
1097 * sighand_cachep is SLAB_DESTROY_BY_RCU so we can free it
1098 * without an RCU grace period, see __lock_task_sighand().
1100 kmem_cache_free(sighand_cachep
, sighand
);
1105 * Initialize POSIX timer handling for a thread group.
1107 static void posix_cpu_timers_init_group(struct signal_struct
*sig
)
1109 unsigned long cpu_limit
;
1111 cpu_limit
= READ_ONCE(sig
->rlim
[RLIMIT_CPU
].rlim_cur
);
1112 if (cpu_limit
!= RLIM_INFINITY
) {
1113 sig
->cputime_expires
.prof_exp
= secs_to_cputime(cpu_limit
);
1114 sig
->cputimer
.running
= true;
1117 /* The timer lists. */
1118 INIT_LIST_HEAD(&sig
->cpu_timers
[0]);
1119 INIT_LIST_HEAD(&sig
->cpu_timers
[1]);
1120 INIT_LIST_HEAD(&sig
->cpu_timers
[2]);
1123 static int copy_signal(unsigned long clone_flags
, struct task_struct
*tsk
)
1125 struct signal_struct
*sig
;
1127 if (clone_flags
& CLONE_THREAD
)
1130 sig
= kmem_cache_zalloc(signal_cachep
, GFP_KERNEL
);
1135 sig
->nr_threads
= 1;
1136 atomic_set(&sig
->live
, 1);
1137 atomic_set(&sig
->sigcnt
, 1);
1139 /* list_add(thread_node, thread_head) without INIT_LIST_HEAD() */
1140 sig
->thread_head
= (struct list_head
)LIST_HEAD_INIT(tsk
->thread_node
);
1141 tsk
->thread_node
= (struct list_head
)LIST_HEAD_INIT(sig
->thread_head
);
1143 init_waitqueue_head(&sig
->wait_chldexit
);
1144 sig
->curr_target
= tsk
;
1145 init_sigpending(&sig
->shared_pending
);
1146 INIT_LIST_HEAD(&sig
->posix_timers
);
1147 seqlock_init(&sig
->stats_lock
);
1148 prev_cputime_init(&sig
->prev_cputime
);
1150 hrtimer_init(&sig
->real_timer
, CLOCK_MONOTONIC
, HRTIMER_MODE_REL
);
1151 sig
->real_timer
.function
= it_real_fn
;
1153 task_lock(current
->group_leader
);
1154 memcpy(sig
->rlim
, current
->signal
->rlim
, sizeof sig
->rlim
);
1155 task_unlock(current
->group_leader
);
1157 posix_cpu_timers_init_group(sig
);
1159 tty_audit_fork(sig
);
1160 sched_autogroup_fork(sig
);
1162 sig
->oom_score_adj
= current
->signal
->oom_score_adj
;
1163 sig
->oom_score_adj_min
= current
->signal
->oom_score_adj_min
;
1165 sig
->has_child_subreaper
= current
->signal
->has_child_subreaper
||
1166 current
->signal
->is_child_subreaper
;
1168 mutex_init(&sig
->cred_guard_mutex
);
1173 static void copy_seccomp(struct task_struct
*p
)
1175 #ifdef CONFIG_SECCOMP
1177 * Must be called with sighand->lock held, which is common to
1178 * all threads in the group. Holding cred_guard_mutex is not
1179 * needed because this new task is not yet running and cannot
1182 assert_spin_locked(¤t
->sighand
->siglock
);
1184 /* Ref-count the new filter user, and assign it. */
1185 get_seccomp_filter(current
);
1186 p
->seccomp
= current
->seccomp
;
1189 * Explicitly enable no_new_privs here in case it got set
1190 * between the task_struct being duplicated and holding the
1191 * sighand lock. The seccomp state and nnp must be in sync.
1193 if (task_no_new_privs(current
))
1194 task_set_no_new_privs(p
);
1197 * If the parent gained a seccomp mode after copying thread
1198 * flags and between before we held the sighand lock, we have
1199 * to manually enable the seccomp thread flag here.
1201 if (p
->seccomp
.mode
!= SECCOMP_MODE_DISABLED
)
1202 set_tsk_thread_flag(p
, TIF_SECCOMP
);
1206 SYSCALL_DEFINE1(set_tid_address
, int __user
*, tidptr
)
1208 current
->clear_child_tid
= tidptr
;
1210 return task_pid_vnr(current
);
1213 static void rt_mutex_init_task(struct task_struct
*p
)
1215 raw_spin_lock_init(&p
->pi_lock
);
1216 #ifdef CONFIG_RT_MUTEXES
1217 p
->pi_waiters
= RB_ROOT
;
1218 p
->pi_waiters_leftmost
= NULL
;
1219 p
->pi_blocked_on
= NULL
;
1224 * Initialize POSIX timer handling for a single task.
1226 static void posix_cpu_timers_init(struct task_struct
*tsk
)
1228 tsk
->cputime_expires
.prof_exp
= 0;
1229 tsk
->cputime_expires
.virt_exp
= 0;
1230 tsk
->cputime_expires
.sched_exp
= 0;
1231 INIT_LIST_HEAD(&tsk
->cpu_timers
[0]);
1232 INIT_LIST_HEAD(&tsk
->cpu_timers
[1]);
1233 INIT_LIST_HEAD(&tsk
->cpu_timers
[2]);
1237 init_task_pid(struct task_struct
*task
, enum pid_type type
, struct pid
*pid
)
1239 task
->pids
[type
].pid
= pid
;
1243 * This creates a new process as a copy of the old one,
1244 * but does not actually start it yet.
1246 * It copies the registers, and all the appropriate
1247 * parts of the process environment (as per the clone
1248 * flags). The actual kick-off is left to the caller.
1250 static struct task_struct
*copy_process(unsigned long clone_flags
,
1251 unsigned long stack_start
,
1252 unsigned long stack_size
,
1253 int __user
*child_tidptr
,
1259 struct task_struct
*p
;
1261 if ((clone_flags
& (CLONE_NEWNS
|CLONE_FS
)) == (CLONE_NEWNS
|CLONE_FS
))
1262 return ERR_PTR(-EINVAL
);
1264 if ((clone_flags
& (CLONE_NEWUSER
|CLONE_FS
)) == (CLONE_NEWUSER
|CLONE_FS
))
1265 return ERR_PTR(-EINVAL
);
1268 * Thread groups must share signals as well, and detached threads
1269 * can only be started up within the thread group.
1271 if ((clone_flags
& CLONE_THREAD
) && !(clone_flags
& CLONE_SIGHAND
))
1272 return ERR_PTR(-EINVAL
);
1275 * Shared signal handlers imply shared VM. By way of the above,
1276 * thread groups also imply shared VM. Blocking this case allows
1277 * for various simplifications in other code.
1279 if ((clone_flags
& CLONE_SIGHAND
) && !(clone_flags
& CLONE_VM
))
1280 return ERR_PTR(-EINVAL
);
1283 * Siblings of global init remain as zombies on exit since they are
1284 * not reaped by their parent (swapper). To solve this and to avoid
1285 * multi-rooted process trees, prevent global and container-inits
1286 * from creating siblings.
1288 if ((clone_flags
& CLONE_PARENT
) &&
1289 current
->signal
->flags
& SIGNAL_UNKILLABLE
)
1290 return ERR_PTR(-EINVAL
);
1293 * If the new process will be in a different pid or user namespace
1294 * do not allow it to share a thread group with the forking task.
1296 if (clone_flags
& CLONE_THREAD
) {
1297 if ((clone_flags
& (CLONE_NEWUSER
| CLONE_NEWPID
)) ||
1298 (task_active_pid_ns(current
) !=
1299 current
->nsproxy
->pid_ns_for_children
))
1300 return ERR_PTR(-EINVAL
);
1303 retval
= security_task_create(clone_flags
);
1308 p
= dup_task_struct(current
);
1312 ftrace_graph_init_task(p
);
1314 rt_mutex_init_task(p
);
1316 #ifdef CONFIG_PROVE_LOCKING
1317 DEBUG_LOCKS_WARN_ON(!p
->hardirqs_enabled
);
1318 DEBUG_LOCKS_WARN_ON(!p
->softirqs_enabled
);
1321 if (atomic_read(&p
->real_cred
->user
->processes
) >=
1322 task_rlimit(p
, RLIMIT_NPROC
)) {
1323 if (p
->real_cred
->user
!= INIT_USER
&&
1324 !capable(CAP_SYS_RESOURCE
) && !capable(CAP_SYS_ADMIN
))
1327 current
->flags
&= ~PF_NPROC_EXCEEDED
;
1329 retval
= copy_creds(p
, clone_flags
);
1334 * If multiple threads are within copy_process(), then this check
1335 * triggers too late. This doesn't hurt, the check is only there
1336 * to stop root fork bombs.
1339 if (nr_threads
>= max_threads
)
1340 goto bad_fork_cleanup_count
;
1342 delayacct_tsk_init(p
); /* Must remain after dup_task_struct() */
1343 p
->flags
&= ~(PF_SUPERPRIV
| PF_WQ_WORKER
);
1344 p
->flags
|= PF_FORKNOEXEC
;
1345 INIT_LIST_HEAD(&p
->children
);
1346 INIT_LIST_HEAD(&p
->sibling
);
1347 rcu_copy_process(p
);
1348 p
->vfork_done
= NULL
;
1349 spin_lock_init(&p
->alloc_lock
);
1351 init_sigpending(&p
->pending
);
1353 p
->utime
= p
->stime
= p
->gtime
= 0;
1354 p
->utimescaled
= p
->stimescaled
= 0;
1355 prev_cputime_init(&p
->prev_cputime
);
1357 #ifdef CONFIG_VIRT_CPU_ACCOUNTING_GEN
1358 seqcount_init(&p
->vtime_seqcount
);
1360 p
->vtime_snap_whence
= VTIME_INACTIVE
;
1363 #if defined(SPLIT_RSS_COUNTING)
1364 memset(&p
->rss_stat
, 0, sizeof(p
->rss_stat
));
1367 p
->default_timer_slack_ns
= current
->timer_slack_ns
;
1369 task_io_accounting_init(&p
->ioac
);
1370 acct_clear_integrals(p
);
1372 posix_cpu_timers_init(p
);
1374 p
->start_time
= ktime_get_ns();
1375 p
->real_start_time
= ktime_get_boot_ns();
1376 p
->io_context
= NULL
;
1377 p
->audit_context
= NULL
;
1378 threadgroup_change_begin(current
);
1381 p
->mempolicy
= mpol_dup(p
->mempolicy
);
1382 if (IS_ERR(p
->mempolicy
)) {
1383 retval
= PTR_ERR(p
->mempolicy
);
1384 p
->mempolicy
= NULL
;
1385 goto bad_fork_cleanup_threadgroup_lock
;
1388 #ifdef CONFIG_CPUSETS
1389 p
->cpuset_mem_spread_rotor
= NUMA_NO_NODE
;
1390 p
->cpuset_slab_spread_rotor
= NUMA_NO_NODE
;
1391 seqcount_init(&p
->mems_allowed_seq
);
1393 #ifdef CONFIG_TRACE_IRQFLAGS
1395 p
->hardirqs_enabled
= 0;
1396 p
->hardirq_enable_ip
= 0;
1397 p
->hardirq_enable_event
= 0;
1398 p
->hardirq_disable_ip
= _THIS_IP_
;
1399 p
->hardirq_disable_event
= 0;
1400 p
->softirqs_enabled
= 1;
1401 p
->softirq_enable_ip
= _THIS_IP_
;
1402 p
->softirq_enable_event
= 0;
1403 p
->softirq_disable_ip
= 0;
1404 p
->softirq_disable_event
= 0;
1405 p
->hardirq_context
= 0;
1406 p
->softirq_context
= 0;
1409 p
->pagefault_disabled
= 0;
1411 #ifdef CONFIG_LOCKDEP
1412 p
->lockdep_depth
= 0; /* no locks held yet */
1413 p
->curr_chain_key
= 0;
1414 p
->lockdep_recursion
= 0;
1417 #ifdef CONFIG_DEBUG_MUTEXES
1418 p
->blocked_on
= NULL
; /* not blocked yet */
1420 #ifdef CONFIG_BCACHE
1421 p
->sequential_io
= 0;
1422 p
->sequential_io_avg
= 0;
1425 /* Perform scheduler related setup. Assign this task to a CPU. */
1426 retval
= sched_fork(clone_flags
, p
);
1428 goto bad_fork_cleanup_policy
;
1430 retval
= perf_event_init_task(p
);
1432 goto bad_fork_cleanup_policy
;
1433 retval
= audit_alloc(p
);
1435 goto bad_fork_cleanup_perf
;
1436 /* copy all the process information */
1438 retval
= copy_semundo(clone_flags
, p
);
1440 goto bad_fork_cleanup_audit
;
1441 retval
= copy_files(clone_flags
, p
);
1443 goto bad_fork_cleanup_semundo
;
1444 retval
= copy_fs(clone_flags
, p
);
1446 goto bad_fork_cleanup_files
;
1447 retval
= copy_sighand(clone_flags
, p
);
1449 goto bad_fork_cleanup_fs
;
1450 retval
= copy_signal(clone_flags
, p
);
1452 goto bad_fork_cleanup_sighand
;
1453 retval
= copy_mm(clone_flags
, p
);
1455 goto bad_fork_cleanup_signal
;
1456 retval
= copy_namespaces(clone_flags
, p
);
1458 goto bad_fork_cleanup_mm
;
1459 retval
= copy_io(clone_flags
, p
);
1461 goto bad_fork_cleanup_namespaces
;
1462 retval
= copy_thread_tls(clone_flags
, stack_start
, stack_size
, p
, tls
);
1464 goto bad_fork_cleanup_io
;
1466 if (pid
!= &init_struct_pid
) {
1467 pid
= alloc_pid(p
->nsproxy
->pid_ns_for_children
);
1469 retval
= PTR_ERR(pid
);
1470 goto bad_fork_cleanup_io
;
1474 p
->set_child_tid
= (clone_flags
& CLONE_CHILD_SETTID
) ? child_tidptr
: NULL
;
1476 * Clear TID on mm_release()?
1478 p
->clear_child_tid
= (clone_flags
& CLONE_CHILD_CLEARTID
) ? child_tidptr
: NULL
;
1483 p
->robust_list
= NULL
;
1484 #ifdef CONFIG_COMPAT
1485 p
->compat_robust_list
= NULL
;
1487 INIT_LIST_HEAD(&p
->pi_state_list
);
1488 p
->pi_state_cache
= NULL
;
1491 * sigaltstack should be cleared when sharing the same VM
1493 if ((clone_flags
& (CLONE_VM
|CLONE_VFORK
)) == CLONE_VM
)
1494 p
->sas_ss_sp
= p
->sas_ss_size
= 0;
1497 * Syscall tracing and stepping should be turned off in the
1498 * child regardless of CLONE_PTRACE.
1500 user_disable_single_step(p
);
1501 clear_tsk_thread_flag(p
, TIF_SYSCALL_TRACE
);
1502 #ifdef TIF_SYSCALL_EMU
1503 clear_tsk_thread_flag(p
, TIF_SYSCALL_EMU
);
1505 clear_all_latency_tracing(p
);
1507 /* ok, now we should be set up.. */
1508 p
->pid
= pid_nr(pid
);
1509 if (clone_flags
& CLONE_THREAD
) {
1510 p
->exit_signal
= -1;
1511 p
->group_leader
= current
->group_leader
;
1512 p
->tgid
= current
->tgid
;
1514 if (clone_flags
& CLONE_PARENT
)
1515 p
->exit_signal
= current
->group_leader
->exit_signal
;
1517 p
->exit_signal
= (clone_flags
& CSIGNAL
);
1518 p
->group_leader
= p
;
1523 p
->nr_dirtied_pause
= 128 >> (PAGE_SHIFT
- 10);
1524 p
->dirty_paused_when
= 0;
1526 p
->pdeath_signal
= 0;
1527 INIT_LIST_HEAD(&p
->thread_group
);
1528 p
->task_works
= NULL
;
1531 * Ensure that the cgroup subsystem policies allow the new process to be
1532 * forked. It should be noted the the new process's css_set can be changed
1533 * between here and cgroup_post_fork() if an organisation operation is in
1536 retval
= cgroup_can_fork(p
);
1538 goto bad_fork_free_pid
;
1541 * Make it visible to the rest of the system, but dont wake it up yet.
1542 * Need tasklist lock for parent etc handling!
1544 write_lock_irq(&tasklist_lock
);
1546 /* CLONE_PARENT re-uses the old parent */
1547 if (clone_flags
& (CLONE_PARENT
|CLONE_THREAD
)) {
1548 p
->real_parent
= current
->real_parent
;
1549 p
->parent_exec_id
= current
->parent_exec_id
;
1551 p
->real_parent
= current
;
1552 p
->parent_exec_id
= current
->self_exec_id
;
1555 spin_lock(¤t
->sighand
->siglock
);
1558 * Copy seccomp details explicitly here, in case they were changed
1559 * before holding sighand lock.
1564 * Process group and session signals need to be delivered to just the
1565 * parent before the fork or both the parent and the child after the
1566 * fork. Restart if a signal comes in before we add the new process to
1567 * it's process group.
1568 * A fatal signal pending means that current will exit, so the new
1569 * thread can't slip out of an OOM kill (or normal SIGKILL).
1571 recalc_sigpending();
1572 if (signal_pending(current
)) {
1573 spin_unlock(¤t
->sighand
->siglock
);
1574 write_unlock_irq(&tasklist_lock
);
1575 retval
= -ERESTARTNOINTR
;
1576 goto bad_fork_cancel_cgroup
;
1579 if (likely(p
->pid
)) {
1580 ptrace_init_task(p
, (clone_flags
& CLONE_PTRACE
) || trace
);
1582 init_task_pid(p
, PIDTYPE_PID
, pid
);
1583 if (thread_group_leader(p
)) {
1584 init_task_pid(p
, PIDTYPE_PGID
, task_pgrp(current
));
1585 init_task_pid(p
, PIDTYPE_SID
, task_session(current
));
1587 if (is_child_reaper(pid
)) {
1588 ns_of_pid(pid
)->child_reaper
= p
;
1589 p
->signal
->flags
|= SIGNAL_UNKILLABLE
;
1592 p
->signal
->leader_pid
= pid
;
1593 p
->signal
->tty
= tty_kref_get(current
->signal
->tty
);
1594 list_add_tail(&p
->sibling
, &p
->real_parent
->children
);
1595 list_add_tail_rcu(&p
->tasks
, &init_task
.tasks
);
1596 attach_pid(p
, PIDTYPE_PGID
);
1597 attach_pid(p
, PIDTYPE_SID
);
1598 __this_cpu_inc(process_counts
);
1600 current
->signal
->nr_threads
++;
1601 atomic_inc(¤t
->signal
->live
);
1602 atomic_inc(¤t
->signal
->sigcnt
);
1603 list_add_tail_rcu(&p
->thread_group
,
1604 &p
->group_leader
->thread_group
);
1605 list_add_tail_rcu(&p
->thread_node
,
1606 &p
->signal
->thread_head
);
1608 attach_pid(p
, PIDTYPE_PID
);
1613 spin_unlock(¤t
->sighand
->siglock
);
1614 syscall_tracepoint_update(p
);
1615 write_unlock_irq(&tasklist_lock
);
1617 proc_fork_connector(p
);
1618 cgroup_post_fork(p
);
1619 threadgroup_change_end(current
);
1622 trace_task_newtask(p
, clone_flags
);
1623 uprobe_copy_process(p
, clone_flags
);
1627 bad_fork_cancel_cgroup
:
1628 cgroup_cancel_fork(p
);
1630 if (pid
!= &init_struct_pid
)
1632 bad_fork_cleanup_io
:
1635 bad_fork_cleanup_namespaces
:
1636 exit_task_namespaces(p
);
1637 bad_fork_cleanup_mm
:
1640 bad_fork_cleanup_signal
:
1641 if (!(clone_flags
& CLONE_THREAD
))
1642 free_signal_struct(p
->signal
);
1643 bad_fork_cleanup_sighand
:
1644 __cleanup_sighand(p
->sighand
);
1645 bad_fork_cleanup_fs
:
1646 exit_fs(p
); /* blocking */
1647 bad_fork_cleanup_files
:
1648 exit_files(p
); /* blocking */
1649 bad_fork_cleanup_semundo
:
1651 bad_fork_cleanup_audit
:
1653 bad_fork_cleanup_perf
:
1654 perf_event_free_task(p
);
1655 bad_fork_cleanup_policy
:
1657 mpol_put(p
->mempolicy
);
1658 bad_fork_cleanup_threadgroup_lock
:
1660 threadgroup_change_end(current
);
1661 delayacct_tsk_free(p
);
1662 bad_fork_cleanup_count
:
1663 atomic_dec(&p
->cred
->user
->processes
);
1668 return ERR_PTR(retval
);
1671 static inline void init_idle_pids(struct pid_link
*links
)
1675 for (type
= PIDTYPE_PID
; type
< PIDTYPE_MAX
; ++type
) {
1676 INIT_HLIST_NODE(&links
[type
].node
); /* not really needed */
1677 links
[type
].pid
= &init_struct_pid
;
1681 struct task_struct
*fork_idle(int cpu
)
1683 struct task_struct
*task
;
1684 task
= copy_process(CLONE_VM
, 0, 0, NULL
, &init_struct_pid
, 0, 0);
1685 if (!IS_ERR(task
)) {
1686 init_idle_pids(task
->pids
);
1687 init_idle(task
, cpu
);
1694 * Ok, this is the main fork-routine.
1696 * It copies the process, and if successful kick-starts
1697 * it and waits for it to finish using the VM if required.
1699 long _do_fork(unsigned long clone_flags
,
1700 unsigned long stack_start
,
1701 unsigned long stack_size
,
1702 int __user
*parent_tidptr
,
1703 int __user
*child_tidptr
,
1706 struct task_struct
*p
;
1711 * Determine whether and which event to report to ptracer. When
1712 * called from kernel_thread or CLONE_UNTRACED is explicitly
1713 * requested, no event is reported; otherwise, report if the event
1714 * for the type of forking is enabled.
1716 if (!(clone_flags
& CLONE_UNTRACED
)) {
1717 if (clone_flags
& CLONE_VFORK
)
1718 trace
= PTRACE_EVENT_VFORK
;
1719 else if ((clone_flags
& CSIGNAL
) != SIGCHLD
)
1720 trace
= PTRACE_EVENT_CLONE
;
1722 trace
= PTRACE_EVENT_FORK
;
1724 if (likely(!ptrace_event_enabled(current
, trace
)))
1728 p
= copy_process(clone_flags
, stack_start
, stack_size
,
1729 child_tidptr
, NULL
, trace
, tls
);
1731 * Do this prior waking up the new thread - the thread pointer
1732 * might get invalid after that point, if the thread exits quickly.
1735 struct completion vfork
;
1738 trace_sched_process_fork(current
, p
);
1740 pid
= get_task_pid(p
, PIDTYPE_PID
);
1743 if (clone_flags
& CLONE_PARENT_SETTID
)
1744 put_user(nr
, parent_tidptr
);
1746 if (clone_flags
& CLONE_VFORK
) {
1747 p
->vfork_done
= &vfork
;
1748 init_completion(&vfork
);
1752 wake_up_new_task(p
);
1754 /* forking complete and child started to run, tell ptracer */
1755 if (unlikely(trace
))
1756 ptrace_event_pid(trace
, pid
);
1758 if (clone_flags
& CLONE_VFORK
) {
1759 if (!wait_for_vfork_done(p
, &vfork
))
1760 ptrace_event_pid(PTRACE_EVENT_VFORK_DONE
, pid
);
1770 #ifndef CONFIG_HAVE_COPY_THREAD_TLS
1771 /* For compatibility with architectures that call do_fork directly rather than
1772 * using the syscall entry points below. */
1773 long do_fork(unsigned long clone_flags
,
1774 unsigned long stack_start
,
1775 unsigned long stack_size
,
1776 int __user
*parent_tidptr
,
1777 int __user
*child_tidptr
)
1779 return _do_fork(clone_flags
, stack_start
, stack_size
,
1780 parent_tidptr
, child_tidptr
, 0);
1785 * Create a kernel thread.
1787 pid_t
kernel_thread(int (*fn
)(void *), void *arg
, unsigned long flags
)
1789 return _do_fork(flags
|CLONE_VM
|CLONE_UNTRACED
, (unsigned long)fn
,
1790 (unsigned long)arg
, NULL
, NULL
, 0);
1793 #ifdef __ARCH_WANT_SYS_FORK
1794 SYSCALL_DEFINE0(fork
)
1797 return _do_fork(SIGCHLD
, 0, 0, NULL
, NULL
, 0);
1799 /* can not support in nommu mode */
1805 #ifdef __ARCH_WANT_SYS_VFORK
1806 SYSCALL_DEFINE0(vfork
)
1808 return _do_fork(CLONE_VFORK
| CLONE_VM
| SIGCHLD
, 0,
1813 #ifdef __ARCH_WANT_SYS_CLONE
1814 #ifdef CONFIG_CLONE_BACKWARDS
1815 SYSCALL_DEFINE5(clone
, unsigned long, clone_flags
, unsigned long, newsp
,
1816 int __user
*, parent_tidptr
,
1818 int __user
*, child_tidptr
)
1819 #elif defined(CONFIG_CLONE_BACKWARDS2)
1820 SYSCALL_DEFINE5(clone
, unsigned long, newsp
, unsigned long, clone_flags
,
1821 int __user
*, parent_tidptr
,
1822 int __user
*, child_tidptr
,
1824 #elif defined(CONFIG_CLONE_BACKWARDS3)
1825 SYSCALL_DEFINE6(clone
, unsigned long, clone_flags
, unsigned long, newsp
,
1827 int __user
*, parent_tidptr
,
1828 int __user
*, child_tidptr
,
1831 SYSCALL_DEFINE5(clone
, unsigned long, clone_flags
, unsigned long, newsp
,
1832 int __user
*, parent_tidptr
,
1833 int __user
*, child_tidptr
,
1837 return _do_fork(clone_flags
, newsp
, 0, parent_tidptr
, child_tidptr
, tls
);
1841 #ifndef ARCH_MIN_MMSTRUCT_ALIGN
1842 #define ARCH_MIN_MMSTRUCT_ALIGN 0
1845 static void sighand_ctor(void *data
)
1847 struct sighand_struct
*sighand
= data
;
1849 spin_lock_init(&sighand
->siglock
);
1850 init_waitqueue_head(&sighand
->signalfd_wqh
);
1853 void __init
proc_caches_init(void)
1855 sighand_cachep
= kmem_cache_create("sighand_cache",
1856 sizeof(struct sighand_struct
), 0,
1857 SLAB_HWCACHE_ALIGN
|SLAB_PANIC
|SLAB_DESTROY_BY_RCU
|
1858 SLAB_NOTRACK
|SLAB_ACCOUNT
, sighand_ctor
);
1859 signal_cachep
= kmem_cache_create("signal_cache",
1860 sizeof(struct signal_struct
), 0,
1861 SLAB_HWCACHE_ALIGN
|SLAB_PANIC
|SLAB_NOTRACK
|SLAB_ACCOUNT
,
1863 files_cachep
= kmem_cache_create("files_cache",
1864 sizeof(struct files_struct
), 0,
1865 SLAB_HWCACHE_ALIGN
|SLAB_PANIC
|SLAB_NOTRACK
|SLAB_ACCOUNT
,
1867 fs_cachep
= kmem_cache_create("fs_cache",
1868 sizeof(struct fs_struct
), 0,
1869 SLAB_HWCACHE_ALIGN
|SLAB_PANIC
|SLAB_NOTRACK
|SLAB_ACCOUNT
,
1872 * FIXME! The "sizeof(struct mm_struct)" currently includes the
1873 * whole struct cpumask for the OFFSTACK case. We could change
1874 * this to *only* allocate as much of it as required by the
1875 * maximum number of CPU's we can ever have. The cpumask_allocation
1876 * is at the end of the structure, exactly for that reason.
1878 mm_cachep
= kmem_cache_create("mm_struct",
1879 sizeof(struct mm_struct
), ARCH_MIN_MMSTRUCT_ALIGN
,
1880 SLAB_HWCACHE_ALIGN
|SLAB_PANIC
|SLAB_NOTRACK
|SLAB_ACCOUNT
,
1882 vm_area_cachep
= KMEM_CACHE(vm_area_struct
, SLAB_PANIC
|SLAB_ACCOUNT
);
1884 nsproxy_cache_init();
1888 * Check constraints on flags passed to the unshare system call.
1890 static int check_unshare_flags(unsigned long unshare_flags
)
1892 if (unshare_flags
& ~(CLONE_THREAD
|CLONE_FS
|CLONE_NEWNS
|CLONE_SIGHAND
|
1893 CLONE_VM
|CLONE_FILES
|CLONE_SYSVSEM
|
1894 CLONE_NEWUTS
|CLONE_NEWIPC
|CLONE_NEWNET
|
1895 CLONE_NEWUSER
|CLONE_NEWPID
|CLONE_NEWCGROUP
))
1898 * Not implemented, but pretend it works if there is nothing
1899 * to unshare. Note that unsharing the address space or the
1900 * signal handlers also need to unshare the signal queues (aka
1903 if (unshare_flags
& (CLONE_THREAD
| CLONE_SIGHAND
| CLONE_VM
)) {
1904 if (!thread_group_empty(current
))
1907 if (unshare_flags
& (CLONE_SIGHAND
| CLONE_VM
)) {
1908 if (atomic_read(¤t
->sighand
->count
) > 1)
1911 if (unshare_flags
& CLONE_VM
) {
1912 if (!current_is_single_threaded())
1920 * Unshare the filesystem structure if it is being shared
1922 static int unshare_fs(unsigned long unshare_flags
, struct fs_struct
**new_fsp
)
1924 struct fs_struct
*fs
= current
->fs
;
1926 if (!(unshare_flags
& CLONE_FS
) || !fs
)
1929 /* don't need lock here; in the worst case we'll do useless copy */
1933 *new_fsp
= copy_fs_struct(fs
);
1941 * Unshare file descriptor table if it is being shared
1943 static int unshare_fd(unsigned long unshare_flags
, struct files_struct
**new_fdp
)
1945 struct files_struct
*fd
= current
->files
;
1948 if ((unshare_flags
& CLONE_FILES
) &&
1949 (fd
&& atomic_read(&fd
->count
) > 1)) {
1950 *new_fdp
= dup_fd(fd
, &error
);
1959 * unshare allows a process to 'unshare' part of the process
1960 * context which was originally shared using clone. copy_*
1961 * functions used by do_fork() cannot be used here directly
1962 * because they modify an inactive task_struct that is being
1963 * constructed. Here we are modifying the current, active,
1966 SYSCALL_DEFINE1(unshare
, unsigned long, unshare_flags
)
1968 struct fs_struct
*fs
, *new_fs
= NULL
;
1969 struct files_struct
*fd
, *new_fd
= NULL
;
1970 struct cred
*new_cred
= NULL
;
1971 struct nsproxy
*new_nsproxy
= NULL
;
1976 * If unsharing a user namespace must also unshare the thread group
1977 * and unshare the filesystem root and working directories.
1979 if (unshare_flags
& CLONE_NEWUSER
)
1980 unshare_flags
|= CLONE_THREAD
| CLONE_FS
;
1982 * If unsharing vm, must also unshare signal handlers.
1984 if (unshare_flags
& CLONE_VM
)
1985 unshare_flags
|= CLONE_SIGHAND
;
1987 * If unsharing a signal handlers, must also unshare the signal queues.
1989 if (unshare_flags
& CLONE_SIGHAND
)
1990 unshare_flags
|= CLONE_THREAD
;
1992 * If unsharing namespace, must also unshare filesystem information.
1994 if (unshare_flags
& CLONE_NEWNS
)
1995 unshare_flags
|= CLONE_FS
;
1997 err
= check_unshare_flags(unshare_flags
);
1999 goto bad_unshare_out
;
2001 * CLONE_NEWIPC must also detach from the undolist: after switching
2002 * to a new ipc namespace, the semaphore arrays from the old
2003 * namespace are unreachable.
2005 if (unshare_flags
& (CLONE_NEWIPC
|CLONE_SYSVSEM
))
2007 err
= unshare_fs(unshare_flags
, &new_fs
);
2009 goto bad_unshare_out
;
2010 err
= unshare_fd(unshare_flags
, &new_fd
);
2012 goto bad_unshare_cleanup_fs
;
2013 err
= unshare_userns(unshare_flags
, &new_cred
);
2015 goto bad_unshare_cleanup_fd
;
2016 err
= unshare_nsproxy_namespaces(unshare_flags
, &new_nsproxy
,
2019 goto bad_unshare_cleanup_cred
;
2021 if (new_fs
|| new_fd
|| do_sysvsem
|| new_cred
|| new_nsproxy
) {
2024 * CLONE_SYSVSEM is equivalent to sys_exit().
2028 if (unshare_flags
& CLONE_NEWIPC
) {
2029 /* Orphan segments in old ns (see sem above). */
2031 shm_init_task(current
);
2035 switch_task_namespaces(current
, new_nsproxy
);
2041 spin_lock(&fs
->lock
);
2042 current
->fs
= new_fs
;
2047 spin_unlock(&fs
->lock
);
2051 fd
= current
->files
;
2052 current
->files
= new_fd
;
2056 task_unlock(current
);
2059 /* Install the new user namespace */
2060 commit_creds(new_cred
);
2065 bad_unshare_cleanup_cred
:
2068 bad_unshare_cleanup_fd
:
2070 put_files_struct(new_fd
);
2072 bad_unshare_cleanup_fs
:
2074 free_fs_struct(new_fs
);
2081 * Helper to unshare the files of the current task.
2082 * We don't want to expose copy_files internals to
2083 * the exec layer of the kernel.
2086 int unshare_files(struct files_struct
**displaced
)
2088 struct task_struct
*task
= current
;
2089 struct files_struct
*copy
= NULL
;
2092 error
= unshare_fd(CLONE_FILES
, ©
);
2093 if (error
|| !copy
) {
2097 *displaced
= task
->files
;
2104 int sysctl_max_threads(struct ctl_table
*table
, int write
,
2105 void __user
*buffer
, size_t *lenp
, loff_t
*ppos
)
2109 int threads
= max_threads
;
2110 int min
= MIN_THREADS
;
2111 int max
= MAX_THREADS
;
2118 ret
= proc_dointvec_minmax(&t
, write
, buffer
, lenp
, ppos
);
2122 set_max_threads(threads
);