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>
78 #include <linux/kcov.h>
80 #include <asm/pgtable.h>
81 #include <asm/pgalloc.h>
82 #include <asm/uaccess.h>
83 #include <asm/mmu_context.h>
84 #include <asm/cacheflush.h>
85 #include <asm/tlbflush.h>
87 #include <trace/events/sched.h>
89 #define CREATE_TRACE_POINTS
90 #include <trace/events/task.h>
93 * Minimum number of threads to boot the kernel
95 #define MIN_THREADS 20
98 * Maximum number of threads
100 #define MAX_THREADS FUTEX_TID_MASK
103 * Protected counters by write_lock_irq(&tasklist_lock)
105 unsigned long total_forks
; /* Handle normal Linux uptimes. */
106 int nr_threads
; /* The idle threads do not count.. */
108 int max_threads
; /* tunable limit on nr_threads */
110 DEFINE_PER_CPU(unsigned long, process_counts
) = 0;
112 __cacheline_aligned
DEFINE_RWLOCK(tasklist_lock
); /* outer */
114 #ifdef CONFIG_PROVE_RCU
115 int lockdep_tasklist_lock_is_held(void)
117 return lockdep_is_held(&tasklist_lock
);
119 EXPORT_SYMBOL_GPL(lockdep_tasklist_lock_is_held
);
120 #endif /* #ifdef CONFIG_PROVE_RCU */
122 int nr_processes(void)
127 for_each_possible_cpu(cpu
)
128 total
+= per_cpu(process_counts
, cpu
);
133 void __weak
arch_release_task_struct(struct task_struct
*tsk
)
137 #ifndef CONFIG_ARCH_TASK_STRUCT_ALLOCATOR
138 static struct kmem_cache
*task_struct_cachep
;
140 static inline struct task_struct
*alloc_task_struct_node(int node
)
142 return kmem_cache_alloc_node(task_struct_cachep
, GFP_KERNEL
, node
);
145 static inline void free_task_struct(struct task_struct
*tsk
)
147 kmem_cache_free(task_struct_cachep
, tsk
);
151 void __weak
arch_release_thread_stack(unsigned long *stack
)
155 #ifndef CONFIG_ARCH_THREAD_STACK_ALLOCATOR
158 * Allocate pages if THREAD_SIZE is >= PAGE_SIZE, otherwise use a
159 * kmemcache based allocator.
161 # if THREAD_SIZE >= PAGE_SIZE || defined(CONFIG_VMAP_STACK)
162 static unsigned long *alloc_thread_stack_node(struct task_struct
*tsk
, int node
)
164 #ifdef CONFIG_VMAP_STACK
165 void *stack
= __vmalloc_node_range(THREAD_SIZE
, THREAD_SIZE
,
166 VMALLOC_START
, VMALLOC_END
,
167 THREADINFO_GFP
| __GFP_HIGHMEM
,
170 __builtin_return_address(0));
173 * We can't call find_vm_area() in interrupt context, and
174 * free_thread_stack() can be called in interrupt context,
175 * so cache the vm_struct.
178 tsk
->stack_vm_area
= find_vm_area(stack
);
181 struct page
*page
= alloc_pages_node(node
, THREADINFO_GFP
,
184 return page
? page_address(page
) : NULL
;
188 static inline void free_thread_stack(struct task_struct
*tsk
)
190 if (task_stack_vm_area(tsk
))
193 __free_pages(virt_to_page(tsk
->stack
), THREAD_SIZE_ORDER
);
196 static struct kmem_cache
*thread_stack_cache
;
198 static unsigned long *alloc_thread_stack_node(struct task_struct
*tsk
,
201 return kmem_cache_alloc_node(thread_stack_cache
, THREADINFO_GFP
, node
);
204 static void free_thread_stack(struct task_struct
*tsk
)
206 kmem_cache_free(thread_stack_cache
, tsk
->stack
);
209 void thread_stack_cache_init(void)
211 thread_stack_cache
= kmem_cache_create("thread_stack", THREAD_SIZE
,
212 THREAD_SIZE
, 0, NULL
);
213 BUG_ON(thread_stack_cache
== NULL
);
218 /* SLAB cache for signal_struct structures (tsk->signal) */
219 static struct kmem_cache
*signal_cachep
;
221 /* SLAB cache for sighand_struct structures (tsk->sighand) */
222 struct kmem_cache
*sighand_cachep
;
224 /* SLAB cache for files_struct structures (tsk->files) */
225 struct kmem_cache
*files_cachep
;
227 /* SLAB cache for fs_struct structures (tsk->fs) */
228 struct kmem_cache
*fs_cachep
;
230 /* SLAB cache for vm_area_struct structures */
231 struct kmem_cache
*vm_area_cachep
;
233 /* SLAB cache for mm_struct structures (tsk->mm) */
234 static struct kmem_cache
*mm_cachep
;
236 static void account_kernel_stack(struct task_struct
*tsk
, int account
)
238 void *stack
= task_stack_page(tsk
);
239 struct vm_struct
*vm
= task_stack_vm_area(tsk
);
241 BUILD_BUG_ON(IS_ENABLED(CONFIG_VMAP_STACK
) && PAGE_SIZE
% 1024 != 0);
246 BUG_ON(vm
->nr_pages
!= THREAD_SIZE
/ PAGE_SIZE
);
248 for (i
= 0; i
< THREAD_SIZE
/ PAGE_SIZE
; i
++) {
249 mod_zone_page_state(page_zone(vm
->pages
[i
]),
251 PAGE_SIZE
/ 1024 * account
);
254 /* All stack pages belong to the same memcg. */
255 memcg_kmem_update_page_stat(vm
->pages
[0], MEMCG_KERNEL_STACK_KB
,
256 account
* (THREAD_SIZE
/ 1024));
259 * All stack pages are in the same zone and belong to the
262 struct page
*first_page
= virt_to_page(stack
);
264 mod_zone_page_state(page_zone(first_page
), NR_KERNEL_STACK_KB
,
265 THREAD_SIZE
/ 1024 * account
);
267 memcg_kmem_update_page_stat(first_page
, MEMCG_KERNEL_STACK_KB
,
268 account
* (THREAD_SIZE
/ 1024));
272 static void release_task_stack(struct task_struct
*tsk
)
274 account_kernel_stack(tsk
, -1);
275 arch_release_thread_stack(tsk
->stack
);
276 free_thread_stack(tsk
);
278 #ifdef CONFIG_VMAP_STACK
279 tsk
->stack_vm_area
= NULL
;
283 #ifdef CONFIG_THREAD_INFO_IN_TASK
284 void put_task_stack(struct task_struct
*tsk
)
286 if (atomic_dec_and_test(&tsk
->stack_refcount
))
287 release_task_stack(tsk
);
291 void free_task(struct task_struct
*tsk
)
293 #ifndef CONFIG_THREAD_INFO_IN_TASK
295 * The task is finally done with both the stack and thread_info,
298 release_task_stack(tsk
);
301 * If the task had a separate stack allocation, it should be gone
304 WARN_ON_ONCE(atomic_read(&tsk
->stack_refcount
) != 0);
306 rt_mutex_debug_task_free(tsk
);
307 ftrace_graph_exit_task(tsk
);
308 put_seccomp_filter(tsk
);
309 arch_release_task_struct(tsk
);
310 free_task_struct(tsk
);
312 EXPORT_SYMBOL(free_task
);
314 static inline void free_signal_struct(struct signal_struct
*sig
)
316 taskstats_tgid_free(sig
);
317 sched_autogroup_exit(sig
);
318 kmem_cache_free(signal_cachep
, sig
);
321 static inline void put_signal_struct(struct signal_struct
*sig
)
323 if (atomic_dec_and_test(&sig
->sigcnt
))
324 free_signal_struct(sig
);
327 void __put_task_struct(struct task_struct
*tsk
)
329 WARN_ON(!tsk
->exit_state
);
330 WARN_ON(atomic_read(&tsk
->usage
));
331 WARN_ON(tsk
== current
);
335 security_task_free(tsk
);
337 delayacct_tsk_free(tsk
);
338 put_signal_struct(tsk
->signal
);
340 if (!profile_handoff_task(tsk
))
343 EXPORT_SYMBOL_GPL(__put_task_struct
);
345 void __init __weak
arch_task_cache_init(void) { }
350 static void set_max_threads(unsigned int max_threads_suggested
)
355 * The number of threads shall be limited such that the thread
356 * structures may only consume a small part of the available memory.
358 if (fls64(totalram_pages
) + fls64(PAGE_SIZE
) > 64)
359 threads
= MAX_THREADS
;
361 threads
= div64_u64((u64
) totalram_pages
* (u64
) PAGE_SIZE
,
362 (u64
) THREAD_SIZE
* 8UL);
364 if (threads
> max_threads_suggested
)
365 threads
= max_threads_suggested
;
367 max_threads
= clamp_t(u64
, threads
, MIN_THREADS
, MAX_THREADS
);
370 #ifdef CONFIG_ARCH_WANTS_DYNAMIC_TASK_STRUCT
371 /* Initialized by the architecture: */
372 int arch_task_struct_size __read_mostly
;
375 void __init
fork_init(void)
377 #ifndef CONFIG_ARCH_TASK_STRUCT_ALLOCATOR
378 #ifndef ARCH_MIN_TASKALIGN
379 #define ARCH_MIN_TASKALIGN L1_CACHE_BYTES
381 /* create a slab on which task_structs can be allocated */
382 task_struct_cachep
= kmem_cache_create("task_struct",
383 arch_task_struct_size
, ARCH_MIN_TASKALIGN
,
384 SLAB_PANIC
|SLAB_NOTRACK
|SLAB_ACCOUNT
, NULL
);
387 /* do the arch specific task caches init */
388 arch_task_cache_init();
390 set_max_threads(MAX_THREADS
);
392 init_task
.signal
->rlim
[RLIMIT_NPROC
].rlim_cur
= max_threads
/2;
393 init_task
.signal
->rlim
[RLIMIT_NPROC
].rlim_max
= max_threads
/2;
394 init_task
.signal
->rlim
[RLIMIT_SIGPENDING
] =
395 init_task
.signal
->rlim
[RLIMIT_NPROC
];
398 int __weak
arch_dup_task_struct(struct task_struct
*dst
,
399 struct task_struct
*src
)
405 void set_task_stack_end_magic(struct task_struct
*tsk
)
407 unsigned long *stackend
;
409 stackend
= end_of_stack(tsk
);
410 *stackend
= STACK_END_MAGIC
; /* for overflow detection */
413 static struct task_struct
*dup_task_struct(struct task_struct
*orig
, int node
)
415 struct task_struct
*tsk
;
416 unsigned long *stack
;
417 struct vm_struct
*stack_vm_area
;
420 if (node
== NUMA_NO_NODE
)
421 node
= tsk_fork_get_node(orig
);
422 tsk
= alloc_task_struct_node(node
);
426 stack
= alloc_thread_stack_node(tsk
, node
);
430 stack_vm_area
= task_stack_vm_area(tsk
);
432 err
= arch_dup_task_struct(tsk
, orig
);
435 * arch_dup_task_struct() clobbers the stack-related fields. Make
436 * sure they're properly initialized before using any stack-related
440 #ifdef CONFIG_VMAP_STACK
441 tsk
->stack_vm_area
= stack_vm_area
;
443 #ifdef CONFIG_THREAD_INFO_IN_TASK
444 atomic_set(&tsk
->stack_refcount
, 1);
450 #ifdef CONFIG_SECCOMP
452 * We must handle setting up seccomp filters once we're under
453 * the sighand lock in case orig has changed between now and
454 * then. Until then, filter must be NULL to avoid messing up
455 * the usage counts on the error path calling free_task.
457 tsk
->seccomp
.filter
= NULL
;
460 setup_thread_stack(tsk
, orig
);
461 clear_user_return_notifier(tsk
);
462 clear_tsk_need_resched(tsk
);
463 set_task_stack_end_magic(tsk
);
465 #ifdef CONFIG_CC_STACKPROTECTOR
466 tsk
->stack_canary
= get_random_int();
470 * One for us, one for whoever does the "release_task()" (usually
473 atomic_set(&tsk
->usage
, 2);
474 #ifdef CONFIG_BLK_DEV_IO_TRACE
477 tsk
->splice_pipe
= NULL
;
478 tsk
->task_frag
.page
= NULL
;
479 tsk
->wake_q
.next
= NULL
;
481 account_kernel_stack(tsk
, 1);
488 free_thread_stack(tsk
);
490 free_task_struct(tsk
);
495 static int dup_mmap(struct mm_struct
*mm
, struct mm_struct
*oldmm
)
497 struct vm_area_struct
*mpnt
, *tmp
, *prev
, **pprev
;
498 struct rb_node
**rb_link
, *rb_parent
;
500 unsigned long charge
;
502 uprobe_start_dup_mmap();
503 if (down_write_killable(&oldmm
->mmap_sem
)) {
505 goto fail_uprobe_end
;
507 flush_cache_dup_mm(oldmm
);
508 uprobe_dup_mmap(oldmm
, mm
);
510 * Not linked in yet - no deadlock potential:
512 down_write_nested(&mm
->mmap_sem
, SINGLE_DEPTH_NESTING
);
514 /* No ordering required: file already has been exposed. */
515 RCU_INIT_POINTER(mm
->exe_file
, get_mm_exe_file(oldmm
));
517 mm
->total_vm
= oldmm
->total_vm
;
518 mm
->data_vm
= oldmm
->data_vm
;
519 mm
->exec_vm
= oldmm
->exec_vm
;
520 mm
->stack_vm
= oldmm
->stack_vm
;
522 rb_link
= &mm
->mm_rb
.rb_node
;
525 retval
= ksm_fork(mm
, oldmm
);
528 retval
= khugepaged_fork(mm
, oldmm
);
533 for (mpnt
= oldmm
->mmap
; mpnt
; mpnt
= mpnt
->vm_next
) {
536 if (mpnt
->vm_flags
& VM_DONTCOPY
) {
537 vm_stat_account(mm
, mpnt
->vm_flags
, -vma_pages(mpnt
));
541 if (mpnt
->vm_flags
& VM_ACCOUNT
) {
542 unsigned long len
= vma_pages(mpnt
);
544 if (security_vm_enough_memory_mm(oldmm
, len
)) /* sic */
548 tmp
= kmem_cache_alloc(vm_area_cachep
, GFP_KERNEL
);
552 INIT_LIST_HEAD(&tmp
->anon_vma_chain
);
553 retval
= vma_dup_policy(mpnt
, tmp
);
555 goto fail_nomem_policy
;
557 if (anon_vma_fork(tmp
, mpnt
))
558 goto fail_nomem_anon_vma_fork
;
560 ~(VM_LOCKED
|VM_LOCKONFAULT
|VM_UFFD_MISSING
|VM_UFFD_WP
);
561 tmp
->vm_next
= tmp
->vm_prev
= NULL
;
562 tmp
->vm_userfaultfd_ctx
= NULL_VM_UFFD_CTX
;
565 struct inode
*inode
= file_inode(file
);
566 struct address_space
*mapping
= file
->f_mapping
;
569 if (tmp
->vm_flags
& VM_DENYWRITE
)
570 atomic_dec(&inode
->i_writecount
);
571 i_mmap_lock_write(mapping
);
572 if (tmp
->vm_flags
& VM_SHARED
)
573 atomic_inc(&mapping
->i_mmap_writable
);
574 flush_dcache_mmap_lock(mapping
);
575 /* insert tmp into the share list, just after mpnt */
576 vma_interval_tree_insert_after(tmp
, mpnt
,
578 flush_dcache_mmap_unlock(mapping
);
579 i_mmap_unlock_write(mapping
);
583 * Clear hugetlb-related page reserves for children. This only
584 * affects MAP_PRIVATE mappings. Faults generated by the child
585 * are not guaranteed to succeed, even if read-only
587 if (is_vm_hugetlb_page(tmp
))
588 reset_vma_resv_huge_pages(tmp
);
591 * Link in the new vma and copy the page table entries.
594 pprev
= &tmp
->vm_next
;
598 __vma_link_rb(mm
, tmp
, rb_link
, rb_parent
);
599 rb_link
= &tmp
->vm_rb
.rb_right
;
600 rb_parent
= &tmp
->vm_rb
;
603 retval
= copy_page_range(mm
, oldmm
, mpnt
);
605 if (tmp
->vm_ops
&& tmp
->vm_ops
->open
)
606 tmp
->vm_ops
->open(tmp
);
611 /* a new mm has just been created */
612 arch_dup_mmap(oldmm
, mm
);
615 up_write(&mm
->mmap_sem
);
617 up_write(&oldmm
->mmap_sem
);
619 uprobe_end_dup_mmap();
621 fail_nomem_anon_vma_fork
:
622 mpol_put(vma_policy(tmp
));
624 kmem_cache_free(vm_area_cachep
, tmp
);
627 vm_unacct_memory(charge
);
631 static inline int mm_alloc_pgd(struct mm_struct
*mm
)
633 mm
->pgd
= pgd_alloc(mm
);
634 if (unlikely(!mm
->pgd
))
639 static inline void mm_free_pgd(struct mm_struct
*mm
)
641 pgd_free(mm
, mm
->pgd
);
644 static int dup_mmap(struct mm_struct
*mm
, struct mm_struct
*oldmm
)
646 down_write(&oldmm
->mmap_sem
);
647 RCU_INIT_POINTER(mm
->exe_file
, get_mm_exe_file(oldmm
));
648 up_write(&oldmm
->mmap_sem
);
651 #define mm_alloc_pgd(mm) (0)
652 #define mm_free_pgd(mm)
653 #endif /* CONFIG_MMU */
655 __cacheline_aligned_in_smp
DEFINE_SPINLOCK(mmlist_lock
);
657 #define allocate_mm() (kmem_cache_alloc(mm_cachep, GFP_KERNEL))
658 #define free_mm(mm) (kmem_cache_free(mm_cachep, (mm)))
660 static unsigned long default_dump_filter
= MMF_DUMP_FILTER_DEFAULT
;
662 static int __init
coredump_filter_setup(char *s
)
664 default_dump_filter
=
665 (simple_strtoul(s
, NULL
, 0) << MMF_DUMP_FILTER_SHIFT
) &
666 MMF_DUMP_FILTER_MASK
;
670 __setup("coredump_filter=", coredump_filter_setup
);
672 #include <linux/init_task.h>
674 static void mm_init_aio(struct mm_struct
*mm
)
677 spin_lock_init(&mm
->ioctx_lock
);
678 mm
->ioctx_table
= NULL
;
682 static void mm_init_owner(struct mm_struct
*mm
, struct task_struct
*p
)
689 static struct mm_struct
*mm_init(struct mm_struct
*mm
, struct task_struct
*p
)
693 mm
->vmacache_seqnum
= 0;
694 atomic_set(&mm
->mm_users
, 1);
695 atomic_set(&mm
->mm_count
, 1);
696 init_rwsem(&mm
->mmap_sem
);
697 INIT_LIST_HEAD(&mm
->mmlist
);
698 mm
->core_state
= NULL
;
699 atomic_long_set(&mm
->nr_ptes
, 0);
704 memset(&mm
->rss_stat
, 0, sizeof(mm
->rss_stat
));
705 spin_lock_init(&mm
->page_table_lock
);
708 mm_init_owner(mm
, p
);
709 mmu_notifier_mm_init(mm
);
710 clear_tlb_flush_pending(mm
);
711 #if defined(CONFIG_TRANSPARENT_HUGEPAGE) && !USE_SPLIT_PMD_PTLOCKS
712 mm
->pmd_huge_pte
= NULL
;
716 mm
->flags
= current
->mm
->flags
& MMF_INIT_MASK
;
717 mm
->def_flags
= current
->mm
->def_flags
& VM_INIT_DEF_MASK
;
719 mm
->flags
= default_dump_filter
;
723 if (mm_alloc_pgd(mm
))
726 if (init_new_context(p
, mm
))
738 static void check_mm(struct mm_struct
*mm
)
742 for (i
= 0; i
< NR_MM_COUNTERS
; i
++) {
743 long x
= atomic_long_read(&mm
->rss_stat
.count
[i
]);
746 printk(KERN_ALERT
"BUG: Bad rss-counter state "
747 "mm:%p idx:%d val:%ld\n", mm
, i
, x
);
750 if (atomic_long_read(&mm
->nr_ptes
))
751 pr_alert("BUG: non-zero nr_ptes on freeing mm: %ld\n",
752 atomic_long_read(&mm
->nr_ptes
));
754 pr_alert("BUG: non-zero nr_pmds on freeing mm: %ld\n",
757 #if defined(CONFIG_TRANSPARENT_HUGEPAGE) && !USE_SPLIT_PMD_PTLOCKS
758 VM_BUG_ON_MM(mm
->pmd_huge_pte
, mm
);
763 * Allocate and initialize an mm_struct.
765 struct mm_struct
*mm_alloc(void)
767 struct mm_struct
*mm
;
773 memset(mm
, 0, sizeof(*mm
));
774 return mm_init(mm
, current
);
778 * Called when the last reference to the mm
779 * is dropped: either by a lazy thread or by
780 * mmput. Free the page directory and the mm.
782 void __mmdrop(struct mm_struct
*mm
)
784 BUG_ON(mm
== &init_mm
);
787 mmu_notifier_mm_destroy(mm
);
791 EXPORT_SYMBOL_GPL(__mmdrop
);
793 static inline void __mmput(struct mm_struct
*mm
)
795 VM_BUG_ON(atomic_read(&mm
->mm_users
));
797 uprobe_clear_state(mm
);
800 khugepaged_exit(mm
); /* must run before exit_mmap */
802 set_mm_exe_file(mm
, NULL
);
803 if (!list_empty(&mm
->mmlist
)) {
804 spin_lock(&mmlist_lock
);
805 list_del(&mm
->mmlist
);
806 spin_unlock(&mmlist_lock
);
809 module_put(mm
->binfmt
->module
);
814 * Decrement the use count and release all resources for an mm.
816 void mmput(struct mm_struct
*mm
)
820 if (atomic_dec_and_test(&mm
->mm_users
))
823 EXPORT_SYMBOL_GPL(mmput
);
826 static void mmput_async_fn(struct work_struct
*work
)
828 struct mm_struct
*mm
= container_of(work
, struct mm_struct
, async_put_work
);
832 void mmput_async(struct mm_struct
*mm
)
834 if (atomic_dec_and_test(&mm
->mm_users
)) {
835 INIT_WORK(&mm
->async_put_work
, mmput_async_fn
);
836 schedule_work(&mm
->async_put_work
);
842 * set_mm_exe_file - change a reference to the mm's executable file
844 * This changes mm's executable file (shown as symlink /proc/[pid]/exe).
846 * Main users are mmput() and sys_execve(). Callers prevent concurrent
847 * invocations: in mmput() nobody alive left, in execve task is single
848 * threaded. sys_prctl(PR_SET_MM_MAP/EXE_FILE) also needs to set the
849 * mm->exe_file, but does so without using set_mm_exe_file() in order
850 * to do avoid the need for any locks.
852 void set_mm_exe_file(struct mm_struct
*mm
, struct file
*new_exe_file
)
854 struct file
*old_exe_file
;
857 * It is safe to dereference the exe_file without RCU as
858 * this function is only called if nobody else can access
859 * this mm -- see comment above for justification.
861 old_exe_file
= rcu_dereference_raw(mm
->exe_file
);
864 get_file(new_exe_file
);
865 rcu_assign_pointer(mm
->exe_file
, new_exe_file
);
871 * get_mm_exe_file - acquire a reference to the mm's executable file
873 * Returns %NULL if mm has no associated executable file.
874 * User must release file via fput().
876 struct file
*get_mm_exe_file(struct mm_struct
*mm
)
878 struct file
*exe_file
;
881 exe_file
= rcu_dereference(mm
->exe_file
);
882 if (exe_file
&& !get_file_rcu(exe_file
))
887 EXPORT_SYMBOL(get_mm_exe_file
);
890 * get_task_exe_file - acquire a reference to the task's executable file
892 * Returns %NULL if task's mm (if any) has no associated executable file or
893 * this is a kernel thread with borrowed mm (see the comment above get_task_mm).
894 * User must release file via fput().
896 struct file
*get_task_exe_file(struct task_struct
*task
)
898 struct file
*exe_file
= NULL
;
899 struct mm_struct
*mm
;
904 if (!(task
->flags
& PF_KTHREAD
))
905 exe_file
= get_mm_exe_file(mm
);
910 EXPORT_SYMBOL(get_task_exe_file
);
913 * get_task_mm - acquire a reference to the task's mm
915 * Returns %NULL if the task has no mm. Checks PF_KTHREAD (meaning
916 * this kernel workthread has transiently adopted a user mm with use_mm,
917 * to do its AIO) is not set and if so returns a reference to it, after
918 * bumping up the use count. User must release the mm via mmput()
919 * after use. Typically used by /proc and ptrace.
921 struct mm_struct
*get_task_mm(struct task_struct
*task
)
923 struct mm_struct
*mm
;
928 if (task
->flags
& PF_KTHREAD
)
931 atomic_inc(&mm
->mm_users
);
936 EXPORT_SYMBOL_GPL(get_task_mm
);
938 struct mm_struct
*mm_access(struct task_struct
*task
, unsigned int mode
)
940 struct mm_struct
*mm
;
943 err
= mutex_lock_killable(&task
->signal
->cred_guard_mutex
);
947 mm
= get_task_mm(task
);
948 if (mm
&& mm
!= current
->mm
&&
949 !ptrace_may_access(task
, mode
)) {
951 mm
= ERR_PTR(-EACCES
);
953 mutex_unlock(&task
->signal
->cred_guard_mutex
);
958 static void complete_vfork_done(struct task_struct
*tsk
)
960 struct completion
*vfork
;
963 vfork
= tsk
->vfork_done
;
965 tsk
->vfork_done
= NULL
;
971 static int wait_for_vfork_done(struct task_struct
*child
,
972 struct completion
*vfork
)
976 freezer_do_not_count();
977 killed
= wait_for_completion_killable(vfork
);
982 child
->vfork_done
= NULL
;
986 put_task_struct(child
);
990 /* Please note the differences between mmput and mm_release.
991 * mmput is called whenever we stop holding onto a mm_struct,
992 * error success whatever.
994 * mm_release is called after a mm_struct has been removed
995 * from the current process.
997 * This difference is important for error handling, when we
998 * only half set up a mm_struct for a new process and need to restore
999 * the old one. Because we mmput the new mm_struct before
1000 * restoring the old one. . .
1001 * Eric Biederman 10 January 1998
1003 void mm_release(struct task_struct
*tsk
, struct mm_struct
*mm
)
1005 /* Get rid of any futexes when releasing the mm */
1007 if (unlikely(tsk
->robust_list
)) {
1008 exit_robust_list(tsk
);
1009 tsk
->robust_list
= NULL
;
1011 #ifdef CONFIG_COMPAT
1012 if (unlikely(tsk
->compat_robust_list
)) {
1013 compat_exit_robust_list(tsk
);
1014 tsk
->compat_robust_list
= NULL
;
1017 if (unlikely(!list_empty(&tsk
->pi_state_list
)))
1018 exit_pi_state_list(tsk
);
1021 uprobe_free_utask(tsk
);
1023 /* Get rid of any cached register state */
1024 deactivate_mm(tsk
, mm
);
1027 * Signal userspace if we're not exiting with a core dump
1028 * because we want to leave the value intact for debugging
1031 if (tsk
->clear_child_tid
) {
1032 if (!(tsk
->signal
->flags
& SIGNAL_GROUP_COREDUMP
) &&
1033 atomic_read(&mm
->mm_users
) > 1) {
1035 * We don't check the error code - if userspace has
1036 * not set up a proper pointer then tough luck.
1038 put_user(0, tsk
->clear_child_tid
);
1039 sys_futex(tsk
->clear_child_tid
, FUTEX_WAKE
,
1042 tsk
->clear_child_tid
= NULL
;
1046 * All done, finally we can wake up parent and return this mm to him.
1047 * Also kthread_stop() uses this completion for synchronization.
1049 if (tsk
->vfork_done
)
1050 complete_vfork_done(tsk
);
1054 * Allocate a new mm structure and copy contents from the
1055 * mm structure of the passed in task structure.
1057 static struct mm_struct
*dup_mm(struct task_struct
*tsk
)
1059 struct mm_struct
*mm
, *oldmm
= current
->mm
;
1066 memcpy(mm
, oldmm
, sizeof(*mm
));
1068 if (!mm_init(mm
, tsk
))
1071 err
= dup_mmap(mm
, oldmm
);
1075 mm
->hiwater_rss
= get_mm_rss(mm
);
1076 mm
->hiwater_vm
= mm
->total_vm
;
1078 if (mm
->binfmt
&& !try_module_get(mm
->binfmt
->module
))
1084 /* don't put binfmt in mmput, we haven't got module yet */
1092 static int copy_mm(unsigned long clone_flags
, struct task_struct
*tsk
)
1094 struct mm_struct
*mm
, *oldmm
;
1097 tsk
->min_flt
= tsk
->maj_flt
= 0;
1098 tsk
->nvcsw
= tsk
->nivcsw
= 0;
1099 #ifdef CONFIG_DETECT_HUNG_TASK
1100 tsk
->last_switch_count
= tsk
->nvcsw
+ tsk
->nivcsw
;
1104 tsk
->active_mm
= NULL
;
1107 * Are we cloning a kernel thread?
1109 * We need to steal a active VM for that..
1111 oldmm
= current
->mm
;
1115 /* initialize the new vmacache entries */
1116 vmacache_flush(tsk
);
1118 if (clone_flags
& CLONE_VM
) {
1119 atomic_inc(&oldmm
->mm_users
);
1131 tsk
->active_mm
= mm
;
1138 static int copy_fs(unsigned long clone_flags
, struct task_struct
*tsk
)
1140 struct fs_struct
*fs
= current
->fs
;
1141 if (clone_flags
& CLONE_FS
) {
1142 /* tsk->fs is already what we want */
1143 spin_lock(&fs
->lock
);
1145 spin_unlock(&fs
->lock
);
1149 spin_unlock(&fs
->lock
);
1152 tsk
->fs
= copy_fs_struct(fs
);
1158 static int copy_files(unsigned long clone_flags
, struct task_struct
*tsk
)
1160 struct files_struct
*oldf
, *newf
;
1164 * A background process may not have any files ...
1166 oldf
= current
->files
;
1170 if (clone_flags
& CLONE_FILES
) {
1171 atomic_inc(&oldf
->count
);
1175 newf
= dup_fd(oldf
, &error
);
1185 static int copy_io(unsigned long clone_flags
, struct task_struct
*tsk
)
1188 struct io_context
*ioc
= current
->io_context
;
1189 struct io_context
*new_ioc
;
1194 * Share io context with parent, if CLONE_IO is set
1196 if (clone_flags
& CLONE_IO
) {
1198 tsk
->io_context
= ioc
;
1199 } else if (ioprio_valid(ioc
->ioprio
)) {
1200 new_ioc
= get_task_io_context(tsk
, GFP_KERNEL
, NUMA_NO_NODE
);
1201 if (unlikely(!new_ioc
))
1204 new_ioc
->ioprio
= ioc
->ioprio
;
1205 put_io_context(new_ioc
);
1211 static int copy_sighand(unsigned long clone_flags
, struct task_struct
*tsk
)
1213 struct sighand_struct
*sig
;
1215 if (clone_flags
& CLONE_SIGHAND
) {
1216 atomic_inc(¤t
->sighand
->count
);
1219 sig
= kmem_cache_alloc(sighand_cachep
, GFP_KERNEL
);
1220 rcu_assign_pointer(tsk
->sighand
, sig
);
1224 atomic_set(&sig
->count
, 1);
1225 memcpy(sig
->action
, current
->sighand
->action
, sizeof(sig
->action
));
1229 void __cleanup_sighand(struct sighand_struct
*sighand
)
1231 if (atomic_dec_and_test(&sighand
->count
)) {
1232 signalfd_cleanup(sighand
);
1234 * sighand_cachep is SLAB_DESTROY_BY_RCU so we can free it
1235 * without an RCU grace period, see __lock_task_sighand().
1237 kmem_cache_free(sighand_cachep
, sighand
);
1242 * Initialize POSIX timer handling for a thread group.
1244 static void posix_cpu_timers_init_group(struct signal_struct
*sig
)
1246 unsigned long cpu_limit
;
1248 cpu_limit
= READ_ONCE(sig
->rlim
[RLIMIT_CPU
].rlim_cur
);
1249 if (cpu_limit
!= RLIM_INFINITY
) {
1250 sig
->cputime_expires
.prof_exp
= secs_to_cputime(cpu_limit
);
1251 sig
->cputimer
.running
= true;
1254 /* The timer lists. */
1255 INIT_LIST_HEAD(&sig
->cpu_timers
[0]);
1256 INIT_LIST_HEAD(&sig
->cpu_timers
[1]);
1257 INIT_LIST_HEAD(&sig
->cpu_timers
[2]);
1260 static int copy_signal(unsigned long clone_flags
, struct task_struct
*tsk
)
1262 struct signal_struct
*sig
;
1264 if (clone_flags
& CLONE_THREAD
)
1267 sig
= kmem_cache_zalloc(signal_cachep
, GFP_KERNEL
);
1272 sig
->nr_threads
= 1;
1273 atomic_set(&sig
->live
, 1);
1274 atomic_set(&sig
->sigcnt
, 1);
1276 /* list_add(thread_node, thread_head) without INIT_LIST_HEAD() */
1277 sig
->thread_head
= (struct list_head
)LIST_HEAD_INIT(tsk
->thread_node
);
1278 tsk
->thread_node
= (struct list_head
)LIST_HEAD_INIT(sig
->thread_head
);
1280 init_waitqueue_head(&sig
->wait_chldexit
);
1281 sig
->curr_target
= tsk
;
1282 init_sigpending(&sig
->shared_pending
);
1283 INIT_LIST_HEAD(&sig
->posix_timers
);
1284 seqlock_init(&sig
->stats_lock
);
1285 prev_cputime_init(&sig
->prev_cputime
);
1287 hrtimer_init(&sig
->real_timer
, CLOCK_MONOTONIC
, HRTIMER_MODE_REL
);
1288 sig
->real_timer
.function
= it_real_fn
;
1290 task_lock(current
->group_leader
);
1291 memcpy(sig
->rlim
, current
->signal
->rlim
, sizeof sig
->rlim
);
1292 task_unlock(current
->group_leader
);
1294 posix_cpu_timers_init_group(sig
);
1296 tty_audit_fork(sig
);
1297 sched_autogroup_fork(sig
);
1299 sig
->oom_score_adj
= current
->signal
->oom_score_adj
;
1300 sig
->oom_score_adj_min
= current
->signal
->oom_score_adj_min
;
1302 sig
->has_child_subreaper
= current
->signal
->has_child_subreaper
||
1303 current
->signal
->is_child_subreaper
;
1305 mutex_init(&sig
->cred_guard_mutex
);
1310 static void copy_seccomp(struct task_struct
*p
)
1312 #ifdef CONFIG_SECCOMP
1314 * Must be called with sighand->lock held, which is common to
1315 * all threads in the group. Holding cred_guard_mutex is not
1316 * needed because this new task is not yet running and cannot
1319 assert_spin_locked(¤t
->sighand
->siglock
);
1321 /* Ref-count the new filter user, and assign it. */
1322 get_seccomp_filter(current
);
1323 p
->seccomp
= current
->seccomp
;
1326 * Explicitly enable no_new_privs here in case it got set
1327 * between the task_struct being duplicated and holding the
1328 * sighand lock. The seccomp state and nnp must be in sync.
1330 if (task_no_new_privs(current
))
1331 task_set_no_new_privs(p
);
1334 * If the parent gained a seccomp mode after copying thread
1335 * flags and between before we held the sighand lock, we have
1336 * to manually enable the seccomp thread flag here.
1338 if (p
->seccomp
.mode
!= SECCOMP_MODE_DISABLED
)
1339 set_tsk_thread_flag(p
, TIF_SECCOMP
);
1343 SYSCALL_DEFINE1(set_tid_address
, int __user
*, tidptr
)
1345 current
->clear_child_tid
= tidptr
;
1347 return task_pid_vnr(current
);
1350 static void rt_mutex_init_task(struct task_struct
*p
)
1352 raw_spin_lock_init(&p
->pi_lock
);
1353 #ifdef CONFIG_RT_MUTEXES
1354 p
->pi_waiters
= RB_ROOT
;
1355 p
->pi_waiters_leftmost
= NULL
;
1356 p
->pi_blocked_on
= NULL
;
1361 * Initialize POSIX timer handling for a single task.
1363 static void posix_cpu_timers_init(struct task_struct
*tsk
)
1365 tsk
->cputime_expires
.prof_exp
= 0;
1366 tsk
->cputime_expires
.virt_exp
= 0;
1367 tsk
->cputime_expires
.sched_exp
= 0;
1368 INIT_LIST_HEAD(&tsk
->cpu_timers
[0]);
1369 INIT_LIST_HEAD(&tsk
->cpu_timers
[1]);
1370 INIT_LIST_HEAD(&tsk
->cpu_timers
[2]);
1374 init_task_pid(struct task_struct
*task
, enum pid_type type
, struct pid
*pid
)
1376 task
->pids
[type
].pid
= pid
;
1380 * This creates a new process as a copy of the old one,
1381 * but does not actually start it yet.
1383 * It copies the registers, and all the appropriate
1384 * parts of the process environment (as per the clone
1385 * flags). The actual kick-off is left to the caller.
1387 static struct task_struct
*copy_process(unsigned long clone_flags
,
1388 unsigned long stack_start
,
1389 unsigned long stack_size
,
1390 int __user
*child_tidptr
,
1397 struct task_struct
*p
;
1399 if ((clone_flags
& (CLONE_NEWNS
|CLONE_FS
)) == (CLONE_NEWNS
|CLONE_FS
))
1400 return ERR_PTR(-EINVAL
);
1402 if ((clone_flags
& (CLONE_NEWUSER
|CLONE_FS
)) == (CLONE_NEWUSER
|CLONE_FS
))
1403 return ERR_PTR(-EINVAL
);
1406 * Thread groups must share signals as well, and detached threads
1407 * can only be started up within the thread group.
1409 if ((clone_flags
& CLONE_THREAD
) && !(clone_flags
& CLONE_SIGHAND
))
1410 return ERR_PTR(-EINVAL
);
1413 * Shared signal handlers imply shared VM. By way of the above,
1414 * thread groups also imply shared VM. Blocking this case allows
1415 * for various simplifications in other code.
1417 if ((clone_flags
& CLONE_SIGHAND
) && !(clone_flags
& CLONE_VM
))
1418 return ERR_PTR(-EINVAL
);
1421 * Siblings of global init remain as zombies on exit since they are
1422 * not reaped by their parent (swapper). To solve this and to avoid
1423 * multi-rooted process trees, prevent global and container-inits
1424 * from creating siblings.
1426 if ((clone_flags
& CLONE_PARENT
) &&
1427 current
->signal
->flags
& SIGNAL_UNKILLABLE
)
1428 return ERR_PTR(-EINVAL
);
1431 * If the new process will be in a different pid or user namespace
1432 * do not allow it to share a thread group with the forking task.
1434 if (clone_flags
& CLONE_THREAD
) {
1435 if ((clone_flags
& (CLONE_NEWUSER
| CLONE_NEWPID
)) ||
1436 (task_active_pid_ns(current
) !=
1437 current
->nsproxy
->pid_ns_for_children
))
1438 return ERR_PTR(-EINVAL
);
1441 retval
= security_task_create(clone_flags
);
1446 p
= dup_task_struct(current
, node
);
1450 ftrace_graph_init_task(p
);
1452 rt_mutex_init_task(p
);
1454 #ifdef CONFIG_PROVE_LOCKING
1455 DEBUG_LOCKS_WARN_ON(!p
->hardirqs_enabled
);
1456 DEBUG_LOCKS_WARN_ON(!p
->softirqs_enabled
);
1459 if (atomic_read(&p
->real_cred
->user
->processes
) >=
1460 task_rlimit(p
, RLIMIT_NPROC
)) {
1461 if (p
->real_cred
->user
!= INIT_USER
&&
1462 !capable(CAP_SYS_RESOURCE
) && !capable(CAP_SYS_ADMIN
))
1465 current
->flags
&= ~PF_NPROC_EXCEEDED
;
1467 retval
= copy_creds(p
, clone_flags
);
1472 * If multiple threads are within copy_process(), then this check
1473 * triggers too late. This doesn't hurt, the check is only there
1474 * to stop root fork bombs.
1477 if (nr_threads
>= max_threads
)
1478 goto bad_fork_cleanup_count
;
1480 delayacct_tsk_init(p
); /* Must remain after dup_task_struct() */
1481 p
->flags
&= ~(PF_SUPERPRIV
| PF_WQ_WORKER
);
1482 p
->flags
|= PF_FORKNOEXEC
;
1483 INIT_LIST_HEAD(&p
->children
);
1484 INIT_LIST_HEAD(&p
->sibling
);
1485 rcu_copy_process(p
);
1486 p
->vfork_done
= NULL
;
1487 spin_lock_init(&p
->alloc_lock
);
1489 init_sigpending(&p
->pending
);
1491 p
->utime
= p
->stime
= p
->gtime
= 0;
1492 p
->utimescaled
= p
->stimescaled
= 0;
1493 prev_cputime_init(&p
->prev_cputime
);
1495 #ifdef CONFIG_VIRT_CPU_ACCOUNTING_GEN
1496 seqcount_init(&p
->vtime_seqcount
);
1498 p
->vtime_snap_whence
= VTIME_INACTIVE
;
1501 #if defined(SPLIT_RSS_COUNTING)
1502 memset(&p
->rss_stat
, 0, sizeof(p
->rss_stat
));
1505 p
->default_timer_slack_ns
= current
->timer_slack_ns
;
1507 task_io_accounting_init(&p
->ioac
);
1508 acct_clear_integrals(p
);
1510 posix_cpu_timers_init(p
);
1512 p
->start_time
= ktime_get_ns();
1513 p
->real_start_time
= ktime_get_boot_ns();
1514 p
->io_context
= NULL
;
1515 p
->audit_context
= NULL
;
1518 p
->mempolicy
= mpol_dup(p
->mempolicy
);
1519 if (IS_ERR(p
->mempolicy
)) {
1520 retval
= PTR_ERR(p
->mempolicy
);
1521 p
->mempolicy
= NULL
;
1522 goto bad_fork_cleanup_threadgroup_lock
;
1525 #ifdef CONFIG_CPUSETS
1526 p
->cpuset_mem_spread_rotor
= NUMA_NO_NODE
;
1527 p
->cpuset_slab_spread_rotor
= NUMA_NO_NODE
;
1528 seqcount_init(&p
->mems_allowed_seq
);
1530 #ifdef CONFIG_TRACE_IRQFLAGS
1532 p
->hardirqs_enabled
= 0;
1533 p
->hardirq_enable_ip
= 0;
1534 p
->hardirq_enable_event
= 0;
1535 p
->hardirq_disable_ip
= _THIS_IP_
;
1536 p
->hardirq_disable_event
= 0;
1537 p
->softirqs_enabled
= 1;
1538 p
->softirq_enable_ip
= _THIS_IP_
;
1539 p
->softirq_enable_event
= 0;
1540 p
->softirq_disable_ip
= 0;
1541 p
->softirq_disable_event
= 0;
1542 p
->hardirq_context
= 0;
1543 p
->softirq_context
= 0;
1546 p
->pagefault_disabled
= 0;
1548 #ifdef CONFIG_LOCKDEP
1549 p
->lockdep_depth
= 0; /* no locks held yet */
1550 p
->curr_chain_key
= 0;
1551 p
->lockdep_recursion
= 0;
1554 #ifdef CONFIG_DEBUG_MUTEXES
1555 p
->blocked_on
= NULL
; /* not blocked yet */
1557 #ifdef CONFIG_BCACHE
1558 p
->sequential_io
= 0;
1559 p
->sequential_io_avg
= 0;
1562 /* Perform scheduler related setup. Assign this task to a CPU. */
1563 retval
= sched_fork(clone_flags
, p
);
1565 goto bad_fork_cleanup_policy
;
1567 retval
= perf_event_init_task(p
);
1569 goto bad_fork_cleanup_policy
;
1570 retval
= audit_alloc(p
);
1572 goto bad_fork_cleanup_perf
;
1573 /* copy all the process information */
1575 retval
= copy_semundo(clone_flags
, p
);
1577 goto bad_fork_cleanup_audit
;
1578 retval
= copy_files(clone_flags
, p
);
1580 goto bad_fork_cleanup_semundo
;
1581 retval
= copy_fs(clone_flags
, p
);
1583 goto bad_fork_cleanup_files
;
1584 retval
= copy_sighand(clone_flags
, p
);
1586 goto bad_fork_cleanup_fs
;
1587 retval
= copy_signal(clone_flags
, p
);
1589 goto bad_fork_cleanup_sighand
;
1590 retval
= copy_mm(clone_flags
, p
);
1592 goto bad_fork_cleanup_signal
;
1593 retval
= copy_namespaces(clone_flags
, p
);
1595 goto bad_fork_cleanup_mm
;
1596 retval
= copy_io(clone_flags
, p
);
1598 goto bad_fork_cleanup_namespaces
;
1599 retval
= copy_thread_tls(clone_flags
, stack_start
, stack_size
, p
, tls
);
1601 goto bad_fork_cleanup_io
;
1603 if (pid
!= &init_struct_pid
) {
1604 pid
= alloc_pid(p
->nsproxy
->pid_ns_for_children
);
1606 retval
= PTR_ERR(pid
);
1607 goto bad_fork_cleanup_thread
;
1611 p
->set_child_tid
= (clone_flags
& CLONE_CHILD_SETTID
) ? child_tidptr
: NULL
;
1613 * Clear TID on mm_release()?
1615 p
->clear_child_tid
= (clone_flags
& CLONE_CHILD_CLEARTID
) ? child_tidptr
: NULL
;
1620 p
->robust_list
= NULL
;
1621 #ifdef CONFIG_COMPAT
1622 p
->compat_robust_list
= NULL
;
1624 INIT_LIST_HEAD(&p
->pi_state_list
);
1625 p
->pi_state_cache
= NULL
;
1628 * sigaltstack should be cleared when sharing the same VM
1630 if ((clone_flags
& (CLONE_VM
|CLONE_VFORK
)) == CLONE_VM
)
1634 * Syscall tracing and stepping should be turned off in the
1635 * child regardless of CLONE_PTRACE.
1637 user_disable_single_step(p
);
1638 clear_tsk_thread_flag(p
, TIF_SYSCALL_TRACE
);
1639 #ifdef TIF_SYSCALL_EMU
1640 clear_tsk_thread_flag(p
, TIF_SYSCALL_EMU
);
1642 clear_all_latency_tracing(p
);
1644 /* ok, now we should be set up.. */
1645 p
->pid
= pid_nr(pid
);
1646 if (clone_flags
& CLONE_THREAD
) {
1647 p
->exit_signal
= -1;
1648 p
->group_leader
= current
->group_leader
;
1649 p
->tgid
= current
->tgid
;
1651 if (clone_flags
& CLONE_PARENT
)
1652 p
->exit_signal
= current
->group_leader
->exit_signal
;
1654 p
->exit_signal
= (clone_flags
& CSIGNAL
);
1655 p
->group_leader
= p
;
1660 p
->nr_dirtied_pause
= 128 >> (PAGE_SHIFT
- 10);
1661 p
->dirty_paused_when
= 0;
1663 p
->pdeath_signal
= 0;
1664 INIT_LIST_HEAD(&p
->thread_group
);
1665 p
->task_works
= NULL
;
1667 threadgroup_change_begin(current
);
1669 * Ensure that the cgroup subsystem policies allow the new process to be
1670 * forked. It should be noted the the new process's css_set can be changed
1671 * between here and cgroup_post_fork() if an organisation operation is in
1674 retval
= cgroup_can_fork(p
);
1676 goto bad_fork_free_pid
;
1679 * Make it visible to the rest of the system, but dont wake it up yet.
1680 * Need tasklist lock for parent etc handling!
1682 write_lock_irq(&tasklist_lock
);
1684 /* CLONE_PARENT re-uses the old parent */
1685 if (clone_flags
& (CLONE_PARENT
|CLONE_THREAD
)) {
1686 p
->real_parent
= current
->real_parent
;
1687 p
->parent_exec_id
= current
->parent_exec_id
;
1689 p
->real_parent
= current
;
1690 p
->parent_exec_id
= current
->self_exec_id
;
1693 spin_lock(¤t
->sighand
->siglock
);
1696 * Copy seccomp details explicitly here, in case they were changed
1697 * before holding sighand lock.
1702 * Process group and session signals need to be delivered to just the
1703 * parent before the fork or both the parent and the child after the
1704 * fork. Restart if a signal comes in before we add the new process to
1705 * it's process group.
1706 * A fatal signal pending means that current will exit, so the new
1707 * thread can't slip out of an OOM kill (or normal SIGKILL).
1709 recalc_sigpending();
1710 if (signal_pending(current
)) {
1711 spin_unlock(¤t
->sighand
->siglock
);
1712 write_unlock_irq(&tasklist_lock
);
1713 retval
= -ERESTARTNOINTR
;
1714 goto bad_fork_cancel_cgroup
;
1717 if (likely(p
->pid
)) {
1718 ptrace_init_task(p
, (clone_flags
& CLONE_PTRACE
) || trace
);
1720 init_task_pid(p
, PIDTYPE_PID
, pid
);
1721 if (thread_group_leader(p
)) {
1722 init_task_pid(p
, PIDTYPE_PGID
, task_pgrp(current
));
1723 init_task_pid(p
, PIDTYPE_SID
, task_session(current
));
1725 if (is_child_reaper(pid
)) {
1726 ns_of_pid(pid
)->child_reaper
= p
;
1727 p
->signal
->flags
|= SIGNAL_UNKILLABLE
;
1730 p
->signal
->leader_pid
= pid
;
1731 p
->signal
->tty
= tty_kref_get(current
->signal
->tty
);
1732 list_add_tail(&p
->sibling
, &p
->real_parent
->children
);
1733 list_add_tail_rcu(&p
->tasks
, &init_task
.tasks
);
1734 attach_pid(p
, PIDTYPE_PGID
);
1735 attach_pid(p
, PIDTYPE_SID
);
1736 __this_cpu_inc(process_counts
);
1738 current
->signal
->nr_threads
++;
1739 atomic_inc(¤t
->signal
->live
);
1740 atomic_inc(¤t
->signal
->sigcnt
);
1741 list_add_tail_rcu(&p
->thread_group
,
1742 &p
->group_leader
->thread_group
);
1743 list_add_tail_rcu(&p
->thread_node
,
1744 &p
->signal
->thread_head
);
1746 attach_pid(p
, PIDTYPE_PID
);
1751 spin_unlock(¤t
->sighand
->siglock
);
1752 syscall_tracepoint_update(p
);
1753 write_unlock_irq(&tasklist_lock
);
1755 proc_fork_connector(p
);
1756 cgroup_post_fork(p
);
1757 threadgroup_change_end(current
);
1760 trace_task_newtask(p
, clone_flags
);
1761 uprobe_copy_process(p
, clone_flags
);
1765 bad_fork_cancel_cgroup
:
1766 cgroup_cancel_fork(p
);
1768 threadgroup_change_end(current
);
1769 if (pid
!= &init_struct_pid
)
1771 bad_fork_cleanup_thread
:
1773 bad_fork_cleanup_io
:
1776 bad_fork_cleanup_namespaces
:
1777 exit_task_namespaces(p
);
1778 bad_fork_cleanup_mm
:
1781 bad_fork_cleanup_signal
:
1782 if (!(clone_flags
& CLONE_THREAD
))
1783 free_signal_struct(p
->signal
);
1784 bad_fork_cleanup_sighand
:
1785 __cleanup_sighand(p
->sighand
);
1786 bad_fork_cleanup_fs
:
1787 exit_fs(p
); /* blocking */
1788 bad_fork_cleanup_files
:
1789 exit_files(p
); /* blocking */
1790 bad_fork_cleanup_semundo
:
1792 bad_fork_cleanup_audit
:
1794 bad_fork_cleanup_perf
:
1795 perf_event_free_task(p
);
1796 bad_fork_cleanup_policy
:
1798 mpol_put(p
->mempolicy
);
1799 bad_fork_cleanup_threadgroup_lock
:
1801 delayacct_tsk_free(p
);
1802 bad_fork_cleanup_count
:
1803 atomic_dec(&p
->cred
->user
->processes
);
1809 return ERR_PTR(retval
);
1812 static inline void init_idle_pids(struct pid_link
*links
)
1816 for (type
= PIDTYPE_PID
; type
< PIDTYPE_MAX
; ++type
) {
1817 INIT_HLIST_NODE(&links
[type
].node
); /* not really needed */
1818 links
[type
].pid
= &init_struct_pid
;
1822 struct task_struct
*fork_idle(int cpu
)
1824 struct task_struct
*task
;
1825 task
= copy_process(CLONE_VM
, 0, 0, NULL
, &init_struct_pid
, 0, 0,
1827 if (!IS_ERR(task
)) {
1828 init_idle_pids(task
->pids
);
1829 init_idle(task
, cpu
);
1836 * Ok, this is the main fork-routine.
1838 * It copies the process, and if successful kick-starts
1839 * it and waits for it to finish using the VM if required.
1841 long _do_fork(unsigned long clone_flags
,
1842 unsigned long stack_start
,
1843 unsigned long stack_size
,
1844 int __user
*parent_tidptr
,
1845 int __user
*child_tidptr
,
1848 struct task_struct
*p
;
1853 * Determine whether and which event to report to ptracer. When
1854 * called from kernel_thread or CLONE_UNTRACED is explicitly
1855 * requested, no event is reported; otherwise, report if the event
1856 * for the type of forking is enabled.
1858 if (!(clone_flags
& CLONE_UNTRACED
)) {
1859 if (clone_flags
& CLONE_VFORK
)
1860 trace
= PTRACE_EVENT_VFORK
;
1861 else if ((clone_flags
& CSIGNAL
) != SIGCHLD
)
1862 trace
= PTRACE_EVENT_CLONE
;
1864 trace
= PTRACE_EVENT_FORK
;
1866 if (likely(!ptrace_event_enabled(current
, trace
)))
1870 p
= copy_process(clone_flags
, stack_start
, stack_size
,
1871 child_tidptr
, NULL
, trace
, tls
, NUMA_NO_NODE
);
1873 * Do this prior waking up the new thread - the thread pointer
1874 * might get invalid after that point, if the thread exits quickly.
1877 struct completion vfork
;
1880 trace_sched_process_fork(current
, p
);
1882 pid
= get_task_pid(p
, PIDTYPE_PID
);
1885 if (clone_flags
& CLONE_PARENT_SETTID
)
1886 put_user(nr
, parent_tidptr
);
1888 if (clone_flags
& CLONE_VFORK
) {
1889 p
->vfork_done
= &vfork
;
1890 init_completion(&vfork
);
1894 wake_up_new_task(p
);
1896 /* forking complete and child started to run, tell ptracer */
1897 if (unlikely(trace
))
1898 ptrace_event_pid(trace
, pid
);
1900 if (clone_flags
& CLONE_VFORK
) {
1901 if (!wait_for_vfork_done(p
, &vfork
))
1902 ptrace_event_pid(PTRACE_EVENT_VFORK_DONE
, pid
);
1912 #ifndef CONFIG_HAVE_COPY_THREAD_TLS
1913 /* For compatibility with architectures that call do_fork directly rather than
1914 * using the syscall entry points below. */
1915 long do_fork(unsigned long clone_flags
,
1916 unsigned long stack_start
,
1917 unsigned long stack_size
,
1918 int __user
*parent_tidptr
,
1919 int __user
*child_tidptr
)
1921 return _do_fork(clone_flags
, stack_start
, stack_size
,
1922 parent_tidptr
, child_tidptr
, 0);
1927 * Create a kernel thread.
1929 pid_t
kernel_thread(int (*fn
)(void *), void *arg
, unsigned long flags
)
1931 return _do_fork(flags
|CLONE_VM
|CLONE_UNTRACED
, (unsigned long)fn
,
1932 (unsigned long)arg
, NULL
, NULL
, 0);
1935 #ifdef __ARCH_WANT_SYS_FORK
1936 SYSCALL_DEFINE0(fork
)
1939 return _do_fork(SIGCHLD
, 0, 0, NULL
, NULL
, 0);
1941 /* can not support in nommu mode */
1947 #ifdef __ARCH_WANT_SYS_VFORK
1948 SYSCALL_DEFINE0(vfork
)
1950 return _do_fork(CLONE_VFORK
| CLONE_VM
| SIGCHLD
, 0,
1955 #ifdef __ARCH_WANT_SYS_CLONE
1956 #ifdef CONFIG_CLONE_BACKWARDS
1957 SYSCALL_DEFINE5(clone
, unsigned long, clone_flags
, unsigned long, newsp
,
1958 int __user
*, parent_tidptr
,
1960 int __user
*, child_tidptr
)
1961 #elif defined(CONFIG_CLONE_BACKWARDS2)
1962 SYSCALL_DEFINE5(clone
, unsigned long, newsp
, unsigned long, clone_flags
,
1963 int __user
*, parent_tidptr
,
1964 int __user
*, child_tidptr
,
1966 #elif defined(CONFIG_CLONE_BACKWARDS3)
1967 SYSCALL_DEFINE6(clone
, unsigned long, clone_flags
, unsigned long, newsp
,
1969 int __user
*, parent_tidptr
,
1970 int __user
*, child_tidptr
,
1973 SYSCALL_DEFINE5(clone
, unsigned long, clone_flags
, unsigned long, newsp
,
1974 int __user
*, parent_tidptr
,
1975 int __user
*, child_tidptr
,
1979 return _do_fork(clone_flags
, newsp
, 0, parent_tidptr
, child_tidptr
, tls
);
1983 #ifndef ARCH_MIN_MMSTRUCT_ALIGN
1984 #define ARCH_MIN_MMSTRUCT_ALIGN 0
1987 static void sighand_ctor(void *data
)
1989 struct sighand_struct
*sighand
= data
;
1991 spin_lock_init(&sighand
->siglock
);
1992 init_waitqueue_head(&sighand
->signalfd_wqh
);
1995 void __init
proc_caches_init(void)
1997 sighand_cachep
= kmem_cache_create("sighand_cache",
1998 sizeof(struct sighand_struct
), 0,
1999 SLAB_HWCACHE_ALIGN
|SLAB_PANIC
|SLAB_DESTROY_BY_RCU
|
2000 SLAB_NOTRACK
|SLAB_ACCOUNT
, sighand_ctor
);
2001 signal_cachep
= kmem_cache_create("signal_cache",
2002 sizeof(struct signal_struct
), 0,
2003 SLAB_HWCACHE_ALIGN
|SLAB_PANIC
|SLAB_NOTRACK
|SLAB_ACCOUNT
,
2005 files_cachep
= kmem_cache_create("files_cache",
2006 sizeof(struct files_struct
), 0,
2007 SLAB_HWCACHE_ALIGN
|SLAB_PANIC
|SLAB_NOTRACK
|SLAB_ACCOUNT
,
2009 fs_cachep
= kmem_cache_create("fs_cache",
2010 sizeof(struct fs_struct
), 0,
2011 SLAB_HWCACHE_ALIGN
|SLAB_PANIC
|SLAB_NOTRACK
|SLAB_ACCOUNT
,
2014 * FIXME! The "sizeof(struct mm_struct)" currently includes the
2015 * whole struct cpumask for the OFFSTACK case. We could change
2016 * this to *only* allocate as much of it as required by the
2017 * maximum number of CPU's we can ever have. The cpumask_allocation
2018 * is at the end of the structure, exactly for that reason.
2020 mm_cachep
= kmem_cache_create("mm_struct",
2021 sizeof(struct mm_struct
), ARCH_MIN_MMSTRUCT_ALIGN
,
2022 SLAB_HWCACHE_ALIGN
|SLAB_PANIC
|SLAB_NOTRACK
|SLAB_ACCOUNT
,
2024 vm_area_cachep
= KMEM_CACHE(vm_area_struct
, SLAB_PANIC
|SLAB_ACCOUNT
);
2026 nsproxy_cache_init();
2030 * Check constraints on flags passed to the unshare system call.
2032 static int check_unshare_flags(unsigned long unshare_flags
)
2034 if (unshare_flags
& ~(CLONE_THREAD
|CLONE_FS
|CLONE_NEWNS
|CLONE_SIGHAND
|
2035 CLONE_VM
|CLONE_FILES
|CLONE_SYSVSEM
|
2036 CLONE_NEWUTS
|CLONE_NEWIPC
|CLONE_NEWNET
|
2037 CLONE_NEWUSER
|CLONE_NEWPID
|CLONE_NEWCGROUP
))
2040 * Not implemented, but pretend it works if there is nothing
2041 * to unshare. Note that unsharing the address space or the
2042 * signal handlers also need to unshare the signal queues (aka
2045 if (unshare_flags
& (CLONE_THREAD
| CLONE_SIGHAND
| CLONE_VM
)) {
2046 if (!thread_group_empty(current
))
2049 if (unshare_flags
& (CLONE_SIGHAND
| CLONE_VM
)) {
2050 if (atomic_read(¤t
->sighand
->count
) > 1)
2053 if (unshare_flags
& CLONE_VM
) {
2054 if (!current_is_single_threaded())
2062 * Unshare the filesystem structure if it is being shared
2064 static int unshare_fs(unsigned long unshare_flags
, struct fs_struct
**new_fsp
)
2066 struct fs_struct
*fs
= current
->fs
;
2068 if (!(unshare_flags
& CLONE_FS
) || !fs
)
2071 /* don't need lock here; in the worst case we'll do useless copy */
2075 *new_fsp
= copy_fs_struct(fs
);
2083 * Unshare file descriptor table if it is being shared
2085 static int unshare_fd(unsigned long unshare_flags
, struct files_struct
**new_fdp
)
2087 struct files_struct
*fd
= current
->files
;
2090 if ((unshare_flags
& CLONE_FILES
) &&
2091 (fd
&& atomic_read(&fd
->count
) > 1)) {
2092 *new_fdp
= dup_fd(fd
, &error
);
2101 * unshare allows a process to 'unshare' part of the process
2102 * context which was originally shared using clone. copy_*
2103 * functions used by do_fork() cannot be used here directly
2104 * because they modify an inactive task_struct that is being
2105 * constructed. Here we are modifying the current, active,
2108 SYSCALL_DEFINE1(unshare
, unsigned long, unshare_flags
)
2110 struct fs_struct
*fs
, *new_fs
= NULL
;
2111 struct files_struct
*fd
, *new_fd
= NULL
;
2112 struct cred
*new_cred
= NULL
;
2113 struct nsproxy
*new_nsproxy
= NULL
;
2118 * If unsharing a user namespace must also unshare the thread group
2119 * and unshare the filesystem root and working directories.
2121 if (unshare_flags
& CLONE_NEWUSER
)
2122 unshare_flags
|= CLONE_THREAD
| CLONE_FS
;
2124 * If unsharing vm, must also unshare signal handlers.
2126 if (unshare_flags
& CLONE_VM
)
2127 unshare_flags
|= CLONE_SIGHAND
;
2129 * If unsharing a signal handlers, must also unshare the signal queues.
2131 if (unshare_flags
& CLONE_SIGHAND
)
2132 unshare_flags
|= CLONE_THREAD
;
2134 * If unsharing namespace, must also unshare filesystem information.
2136 if (unshare_flags
& CLONE_NEWNS
)
2137 unshare_flags
|= CLONE_FS
;
2139 err
= check_unshare_flags(unshare_flags
);
2141 goto bad_unshare_out
;
2143 * CLONE_NEWIPC must also detach from the undolist: after switching
2144 * to a new ipc namespace, the semaphore arrays from the old
2145 * namespace are unreachable.
2147 if (unshare_flags
& (CLONE_NEWIPC
|CLONE_SYSVSEM
))
2149 err
= unshare_fs(unshare_flags
, &new_fs
);
2151 goto bad_unshare_out
;
2152 err
= unshare_fd(unshare_flags
, &new_fd
);
2154 goto bad_unshare_cleanup_fs
;
2155 err
= unshare_userns(unshare_flags
, &new_cred
);
2157 goto bad_unshare_cleanup_fd
;
2158 err
= unshare_nsproxy_namespaces(unshare_flags
, &new_nsproxy
,
2161 goto bad_unshare_cleanup_cred
;
2163 if (new_fs
|| new_fd
|| do_sysvsem
|| new_cred
|| new_nsproxy
) {
2166 * CLONE_SYSVSEM is equivalent to sys_exit().
2170 if (unshare_flags
& CLONE_NEWIPC
) {
2171 /* Orphan segments in old ns (see sem above). */
2173 shm_init_task(current
);
2177 switch_task_namespaces(current
, new_nsproxy
);
2183 spin_lock(&fs
->lock
);
2184 current
->fs
= new_fs
;
2189 spin_unlock(&fs
->lock
);
2193 fd
= current
->files
;
2194 current
->files
= new_fd
;
2198 task_unlock(current
);
2201 /* Install the new user namespace */
2202 commit_creds(new_cred
);
2207 bad_unshare_cleanup_cred
:
2210 bad_unshare_cleanup_fd
:
2212 put_files_struct(new_fd
);
2214 bad_unshare_cleanup_fs
:
2216 free_fs_struct(new_fs
);
2223 * Helper to unshare the files of the current task.
2224 * We don't want to expose copy_files internals to
2225 * the exec layer of the kernel.
2228 int unshare_files(struct files_struct
**displaced
)
2230 struct task_struct
*task
= current
;
2231 struct files_struct
*copy
= NULL
;
2234 error
= unshare_fd(CLONE_FILES
, ©
);
2235 if (error
|| !copy
) {
2239 *displaced
= task
->files
;
2246 int sysctl_max_threads(struct ctl_table
*table
, int write
,
2247 void __user
*buffer
, size_t *lenp
, loff_t
*ppos
)
2251 int threads
= max_threads
;
2252 int min
= MIN_THREADS
;
2253 int max
= MAX_THREADS
;
2260 ret
= proc_dointvec_minmax(&t
, write
, buffer
, lenp
, ppos
);
2264 set_max_threads(threads
);