3 * Copyright (C) 1992 Krishna Balasubramanian
4 * Copyright (C) 1995 Eric Schenk, Bruno Haible
6 * IMPLEMENTATION NOTES ON CODE REWRITE (Eric Schenk, January 1995):
7 * This code underwent a massive rewrite in order to solve some problems
8 * with the original code. In particular the original code failed to
9 * wake up processes that were waiting for semval to go to 0 if the
10 * value went to 0 and was then incremented rapidly enough. In solving
11 * this problem I have also modified the implementation so that it
12 * processes pending operations in a FIFO manner, thus give a guarantee
13 * that processes waiting for a lock on the semaphore won't starve
14 * unless another locking process fails to unlock.
15 * In addition the following two changes in behavior have been introduced:
16 * - The original implementation of semop returned the value
17 * last semaphore element examined on success. This does not
18 * match the manual page specifications, and effectively
19 * allows the user to read the semaphore even if they do not
20 * have read permissions. The implementation now returns 0
21 * on success as stated in the manual page.
22 * - There is some confusion over whether the set of undo adjustments
23 * to be performed at exit should be done in an atomic manner.
24 * That is, if we are attempting to decrement the semval should we queue
25 * up and wait until we can do so legally?
26 * The original implementation attempted to do this.
27 * The current implementation does not do so. This is because I don't
28 * think it is the right thing (TM) to do, and because I couldn't
29 * see a clean way to get the old behavior with the new design.
30 * The POSIX standard and SVID should be consulted to determine
31 * what behavior is mandated.
33 * Further notes on refinement (Christoph Rohland, December 1998):
34 * - The POSIX standard says, that the undo adjustments simply should
35 * redo. So the current implementation is o.K.
36 * - The previous code had two flaws:
37 * 1) It actively gave the semaphore to the next waiting process
38 * sleeping on the semaphore. Since this process did not have the
39 * cpu this led to many unnecessary context switches and bad
40 * performance. Now we only check which process should be able to
41 * get the semaphore and if this process wants to reduce some
42 * semaphore value we simply wake it up without doing the
43 * operation. So it has to try to get it later. Thus e.g. the
44 * running process may reacquire the semaphore during the current
45 * time slice. If it only waits for zero or increases the semaphore,
46 * we do the operation in advance and wake it up.
47 * 2) It did not wake up all zero waiting processes. We try to do
48 * better but only get the semops right which only wait for zero or
49 * increase. If there are decrement operations in the operations
50 * array we do the same as before.
52 * With the incarnation of O(1) scheduler, it becomes unnecessary to perform
53 * check/retry algorithm for waking up blocked processes as the new scheduler
54 * is better at handling thread switch than the old one.
56 * /proc/sysvipc/sem support (c) 1999 Dragos Acostachioaie <dragos@iname.com>
58 * SMP-threaded, sysctl's added
59 * (c) 1999 Manfred Spraul <manfred@colorfullife.com>
60 * Enforced range limit on SEM_UNDO
61 * (c) 2001 Red Hat Inc
63 * (c) 2003 Manfred Spraul <manfred@colorfullife.com>
65 * support for audit of ipc object properties and permission changes
66 * Dustin Kirkland <dustin.kirkland@us.ibm.com>
70 * Pavel Emelianov <xemul@openvz.org>
73 #include <linux/slab.h>
74 #include <linux/spinlock.h>
75 #include <linux/init.h>
76 #include <linux/proc_fs.h>
77 #include <linux/time.h>
78 #include <linux/security.h>
79 #include <linux/syscalls.h>
80 #include <linux/audit.h>
81 #include <linux/capability.h>
82 #include <linux/seq_file.h>
83 #include <linux/rwsem.h>
84 #include <linux/nsproxy.h>
85 #include <linux/ipc_namespace.h>
87 #include <asm/uaccess.h>
90 #define sem_ids(ns) ((ns)->ids[IPC_SEM_IDS])
92 #define sem_unlock(sma) ipc_unlock(&(sma)->sem_perm)
93 #define sem_checkid(sma, semid) ipc_checkid(&sma->sem_perm, semid)
95 static int newary(struct ipc_namespace
*, struct ipc_params
*);
96 static void freeary(struct ipc_namespace
*, struct kern_ipc_perm
*);
98 static int sysvipc_sem_proc_show(struct seq_file
*s
, void *it
);
101 #define SEMMSL_FAST 256 /* 512 bytes on stack */
102 #define SEMOPM_FAST 64 /* ~ 372 bytes on stack */
105 * linked list protection:
107 * sem_array.sem_pending{,last},
108 * sem_array.sem_undo: sem_lock() for read/write
109 * sem_undo.proc_next: only "current" is allowed to read/write that field.
113 #define sc_semmsl sem_ctls[0]
114 #define sc_semmns sem_ctls[1]
115 #define sc_semopm sem_ctls[2]
116 #define sc_semmni sem_ctls[3]
118 void sem_init_ns(struct ipc_namespace
*ns
)
120 ns
->sc_semmsl
= SEMMSL
;
121 ns
->sc_semmns
= SEMMNS
;
122 ns
->sc_semopm
= SEMOPM
;
123 ns
->sc_semmni
= SEMMNI
;
125 ipc_init_ids(&ns
->ids
[IPC_SEM_IDS
]);
129 void sem_exit_ns(struct ipc_namespace
*ns
)
131 free_ipcs(ns
, &sem_ids(ns
), freeary
);
132 idr_destroy(&ns
->ids
[IPC_SEM_IDS
].ipcs_idr
);
136 void __init
sem_init (void)
138 sem_init_ns(&init_ipc_ns
);
139 ipc_init_proc_interface("sysvipc/sem",
140 " key semid perms nsems uid gid cuid cgid otime ctime\n",
141 IPC_SEM_IDS
, sysvipc_sem_proc_show
);
145 * sem_lock_(check_) routines are called in the paths where the rw_mutex
148 static inline struct sem_array
*sem_lock(struct ipc_namespace
*ns
, int id
)
150 struct kern_ipc_perm
*ipcp
= ipc_lock(&sem_ids(ns
), id
);
153 return (struct sem_array
*)ipcp
;
155 return container_of(ipcp
, struct sem_array
, sem_perm
);
158 static inline struct sem_array
*sem_lock_check(struct ipc_namespace
*ns
,
161 struct kern_ipc_perm
*ipcp
= ipc_lock_check(&sem_ids(ns
), id
);
164 return (struct sem_array
*)ipcp
;
166 return container_of(ipcp
, struct sem_array
, sem_perm
);
169 static inline void sem_lock_and_putref(struct sem_array
*sma
)
171 ipc_lock_by_ptr(&sma
->sem_perm
);
175 static inline void sem_getref_and_unlock(struct sem_array
*sma
)
178 ipc_unlock(&(sma
)->sem_perm
);
181 static inline void sem_putref(struct sem_array
*sma
)
183 ipc_lock_by_ptr(&sma
->sem_perm
);
185 ipc_unlock(&(sma
)->sem_perm
);
188 static inline void sem_rmid(struct ipc_namespace
*ns
, struct sem_array
*s
)
190 ipc_rmid(&sem_ids(ns
), &s
->sem_perm
);
194 * Lockless wakeup algorithm:
195 * Without the check/retry algorithm a lockless wakeup is possible:
196 * - queue.status is initialized to -EINTR before blocking.
197 * - wakeup is performed by
198 * * unlinking the queue entry from sma->sem_pending
199 * * setting queue.status to IN_WAKEUP
200 * This is the notification for the blocked thread that a
201 * result value is imminent.
202 * * call wake_up_process
203 * * set queue.status to the final value.
204 * - the previously blocked thread checks queue.status:
205 * * if it's IN_WAKEUP, then it must wait until the value changes
206 * * if it's not -EINTR, then the operation was completed by
207 * update_queue. semtimedop can return queue.status without
208 * performing any operation on the sem array.
209 * * otherwise it must acquire the spinlock and check what's up.
211 * The two-stage algorithm is necessary to protect against the following
213 * - if queue.status is set after wake_up_process, then the woken up idle
214 * thread could race forward and try (and fail) to acquire sma->lock
215 * before update_queue had a chance to set queue.status
216 * - if queue.status is written before wake_up_process and if the
217 * blocked process is woken up by a signal between writing
218 * queue.status and the wake_up_process, then the woken up
219 * process could return from semtimedop and die by calling
220 * sys_exit before wake_up_process is called. Then wake_up_process
221 * will oops, because the task structure is already invalid.
222 * (yes, this happened on s390 with sysv msg).
228 * newary - Create a new semaphore set
230 * @params: ptr to the structure that contains key, semflg and nsems
232 * Called with sem_ids.rw_mutex held (as a writer)
235 static int newary(struct ipc_namespace
*ns
, struct ipc_params
*params
)
239 struct sem_array
*sma
;
241 key_t key
= params
->key
;
242 int nsems
= params
->u
.nsems
;
243 int semflg
= params
->flg
;
248 if (ns
->used_sems
+ nsems
> ns
->sc_semmns
)
251 size
= sizeof (*sma
) + nsems
* sizeof (struct sem
);
252 sma
= ipc_rcu_alloc(size
);
256 memset (sma
, 0, size
);
258 sma
->sem_perm
.mode
= (semflg
& S_IRWXUGO
);
259 sma
->sem_perm
.key
= key
;
261 sma
->sem_perm
.security
= NULL
;
262 retval
= security_sem_alloc(sma
);
268 id
= ipc_addid(&sem_ids(ns
), &sma
->sem_perm
, ns
->sc_semmni
);
270 security_sem_free(sma
);
274 ns
->used_sems
+= nsems
;
276 sma
->sem_base
= (struct sem
*) &sma
[1];
278 for (i
= 0; i
< nsems
; i
++)
279 INIT_LIST_HEAD(&sma
->sem_base
[i
].sem_pending
);
281 sma
->complex_count
= 0;
282 INIT_LIST_HEAD(&sma
->sem_pending
);
283 INIT_LIST_HEAD(&sma
->list_id
);
284 sma
->sem_nsems
= nsems
;
285 sma
->sem_ctime
= get_seconds();
288 return sma
->sem_perm
.id
;
293 * Called with sem_ids.rw_mutex and ipcp locked.
295 static inline int sem_security(struct kern_ipc_perm
*ipcp
, int semflg
)
297 struct sem_array
*sma
;
299 sma
= container_of(ipcp
, struct sem_array
, sem_perm
);
300 return security_sem_associate(sma
, semflg
);
304 * Called with sem_ids.rw_mutex and ipcp locked.
306 static inline int sem_more_checks(struct kern_ipc_perm
*ipcp
,
307 struct ipc_params
*params
)
309 struct sem_array
*sma
;
311 sma
= container_of(ipcp
, struct sem_array
, sem_perm
);
312 if (params
->u
.nsems
> sma
->sem_nsems
)
318 SYSCALL_DEFINE3(semget
, key_t
, key
, int, nsems
, int, semflg
)
320 struct ipc_namespace
*ns
;
321 struct ipc_ops sem_ops
;
322 struct ipc_params sem_params
;
324 ns
= current
->nsproxy
->ipc_ns
;
326 if (nsems
< 0 || nsems
> ns
->sc_semmsl
)
329 sem_ops
.getnew
= newary
;
330 sem_ops
.associate
= sem_security
;
331 sem_ops
.more_checks
= sem_more_checks
;
333 sem_params
.key
= key
;
334 sem_params
.flg
= semflg
;
335 sem_params
.u
.nsems
= nsems
;
337 return ipcget(ns
, &sem_ids(ns
), &sem_ops
, &sem_params
);
341 * Determine whether a sequence of semaphore operations would succeed
342 * all at once. Return 0 if yes, 1 if need to sleep, else return error code.
345 static int try_atomic_semop (struct sem_array
* sma
, struct sembuf
* sops
,
346 int nsops
, struct sem_undo
*un
, int pid
)
352 for (sop
= sops
; sop
< sops
+ nsops
; sop
++) {
353 curr
= sma
->sem_base
+ sop
->sem_num
;
354 sem_op
= sop
->sem_op
;
355 result
= curr
->semval
;
357 if (!sem_op
&& result
)
365 if (sop
->sem_flg
& SEM_UNDO
) {
366 int undo
= un
->semadj
[sop
->sem_num
] - sem_op
;
368 * Exceeding the undo range is an error.
370 if (undo
< (-SEMAEM
- 1) || undo
> SEMAEM
)
373 curr
->semval
= result
;
377 while (sop
>= sops
) {
378 sma
->sem_base
[sop
->sem_num
].sempid
= pid
;
379 if (sop
->sem_flg
& SEM_UNDO
)
380 un
->semadj
[sop
->sem_num
] -= sop
->sem_op
;
391 if (sop
->sem_flg
& IPC_NOWAIT
)
398 while (sop
>= sops
) {
399 sma
->sem_base
[sop
->sem_num
].semval
-= sop
->sem_op
;
406 /** wake_up_sem_queue_prepare(q, error): Prepare wake-up
407 * @q: queue entry that must be signaled
408 * @error: Error value for the signal
410 * Prepare the wake-up of the queue entry q.
412 static void wake_up_sem_queue_prepare(struct list_head
*pt
,
413 struct sem_queue
*q
, int error
)
415 if (list_empty(pt
)) {
417 * Hold preempt off so that we don't get preempted and have the
418 * wakee busy-wait until we're scheduled back on.
422 q
->status
= IN_WAKEUP
;
425 list_add_tail(&q
->simple_list
, pt
);
429 * wake_up_sem_queue_do(pt) - do the actual wake-up
430 * @pt: list of tasks to be woken up
432 * Do the actual wake-up.
433 * The function is called without any locks held, thus the semaphore array
434 * could be destroyed already and the tasks can disappear as soon as the
435 * status is set to the actual return code.
437 static void wake_up_sem_queue_do(struct list_head
*pt
)
439 struct sem_queue
*q
, *t
;
442 did_something
= !list_empty(pt
);
443 list_for_each_entry_safe(q
, t
, pt
, simple_list
) {
444 wake_up_process(q
->sleeper
);
445 /* q can disappear immediately after writing q->status. */
453 static void unlink_queue(struct sem_array
*sma
, struct sem_queue
*q
)
457 list_del(&q
->simple_list
);
459 sma
->complex_count
--;
462 /** check_restart(sma, q)
463 * @sma: semaphore array
464 * @q: the operation that just completed
466 * update_queue is O(N^2) when it restarts scanning the whole queue of
467 * waiting operations. Therefore this function checks if the restart is
468 * really necessary. It is called after a previously waiting operation
471 static int check_restart(struct sem_array
*sma
, struct sem_queue
*q
)
476 /* if the operation didn't modify the array, then no restart */
480 /* pending complex operations are too difficult to analyse */
481 if (sma
->complex_count
)
484 /* we were a sleeping complex operation. Too difficult */
488 curr
= sma
->sem_base
+ q
->sops
[0].sem_num
;
490 /* No-one waits on this queue */
491 if (list_empty(&curr
->sem_pending
))
494 /* the new semaphore value */
496 /* It is impossible that someone waits for the new value:
497 * - q is a previously sleeping simple operation that
498 * altered the array. It must be a decrement, because
499 * simple increments never sleep.
500 * - The value is not 0, thus wait-for-zero won't proceed.
501 * - If there are older (higher priority) decrements
502 * in the queue, then they have observed the original
503 * semval value and couldn't proceed. The operation
504 * decremented to value - thus they won't proceed either.
506 BUG_ON(q
->sops
[0].sem_op
>= 0);
510 * semval is 0. Check if there are wait-for-zero semops.
511 * They must be the first entries in the per-semaphore simple queue
513 h
= list_first_entry(&curr
->sem_pending
, struct sem_queue
, simple_list
);
514 BUG_ON(h
->nsops
!= 1);
515 BUG_ON(h
->sops
[0].sem_num
!= q
->sops
[0].sem_num
);
517 /* Yes, there is a wait-for-zero semop. Restart */
518 if (h
->sops
[0].sem_op
== 0)
521 /* Again - no-one is waiting for the new value. */
527 * update_queue(sma, semnum): Look for tasks that can be completed.
528 * @sma: semaphore array.
529 * @semnum: semaphore that was modified.
530 * @pt: list head for the tasks that must be woken up.
532 * update_queue must be called after a semaphore in a semaphore array
533 * was modified. If multiple semaphore were modified, then @semnum
535 * The tasks that must be woken up are added to @pt. The return code
536 * is stored in q->pid.
537 * The function return 1 if at least one semop was completed successfully.
539 static int update_queue(struct sem_array
*sma
, int semnum
, struct list_head
*pt
)
542 struct list_head
*walk
;
543 struct list_head
*pending_list
;
545 int semop_completed
= 0;
547 /* if there are complex operations around, then knowing the semaphore
548 * that was modified doesn't help us. Assume that multiple semaphores
551 if (sma
->complex_count
)
555 pending_list
= &sma
->sem_pending
;
556 offset
= offsetof(struct sem_queue
, list
);
558 pending_list
= &sma
->sem_base
[semnum
].sem_pending
;
559 offset
= offsetof(struct sem_queue
, simple_list
);
563 walk
= pending_list
->next
;
564 while (walk
!= pending_list
) {
567 q
= (struct sem_queue
*)((char *)walk
- offset
);
570 /* If we are scanning the single sop, per-semaphore list of
571 * one semaphore and that semaphore is 0, then it is not
572 * necessary to scan the "alter" entries: simple increments
573 * that affect only one entry succeed immediately and cannot
574 * be in the per semaphore pending queue, and decrements
575 * cannot be successful if the value is already 0.
577 if (semnum
!= -1 && sma
->sem_base
[semnum
].semval
== 0 &&
581 error
= try_atomic_semop(sma
, q
->sops
, q
->nsops
,
584 /* Does q->sleeper still need to sleep? */
588 unlink_queue(sma
, q
);
594 restart
= check_restart(sma
, q
);
597 wake_up_sem_queue_prepare(pt
, q
, error
);
601 return semop_completed
;
605 * do_smart_update(sma, sops, nsops, otime, pt) - optimized update_queue
606 * @sma: semaphore array
607 * @sops: operations that were performed
608 * @nsops: number of operations
609 * @otime: force setting otime
610 * @pt: list head of the tasks that must be woken up.
612 * do_smart_update() does the required called to update_queue, based on the
613 * actual changes that were performed on the semaphore array.
614 * Note that the function does not do the actual wake-up: the caller is
615 * responsible for calling wake_up_sem_queue_do(@pt).
616 * It is safe to perform this call after dropping all locks.
618 static void do_smart_update(struct sem_array
*sma
, struct sembuf
*sops
, int nsops
,
619 int otime
, struct list_head
*pt
)
623 if (sma
->complex_count
|| sops
== NULL
) {
624 if (update_queue(sma
, -1, pt
))
629 for (i
= 0; i
< nsops
; i
++) {
630 if (sops
[i
].sem_op
> 0 ||
631 (sops
[i
].sem_op
< 0 &&
632 sma
->sem_base
[sops
[i
].sem_num
].semval
== 0))
633 if (update_queue(sma
, sops
[i
].sem_num
, pt
))
638 sma
->sem_otime
= get_seconds();
642 /* The following counts are associated to each semaphore:
643 * semncnt number of tasks waiting on semval being nonzero
644 * semzcnt number of tasks waiting on semval being zero
645 * This model assumes that a task waits on exactly one semaphore.
646 * Since semaphore operations are to be performed atomically, tasks actually
647 * wait on a whole sequence of semaphores simultaneously.
648 * The counts we return here are a rough approximation, but still
649 * warrant that semncnt+semzcnt>0 if the task is on the pending queue.
651 static int count_semncnt (struct sem_array
* sma
, ushort semnum
)
654 struct sem_queue
* q
;
657 list_for_each_entry(q
, &sma
->sem_pending
, list
) {
658 struct sembuf
* sops
= q
->sops
;
659 int nsops
= q
->nsops
;
661 for (i
= 0; i
< nsops
; i
++)
662 if (sops
[i
].sem_num
== semnum
663 && (sops
[i
].sem_op
< 0)
664 && !(sops
[i
].sem_flg
& IPC_NOWAIT
))
670 static int count_semzcnt (struct sem_array
* sma
, ushort semnum
)
673 struct sem_queue
* q
;
676 list_for_each_entry(q
, &sma
->sem_pending
, list
) {
677 struct sembuf
* sops
= q
->sops
;
678 int nsops
= q
->nsops
;
680 for (i
= 0; i
< nsops
; i
++)
681 if (sops
[i
].sem_num
== semnum
682 && (sops
[i
].sem_op
== 0)
683 && !(sops
[i
].sem_flg
& IPC_NOWAIT
))
689 static void free_un(struct rcu_head
*head
)
691 struct sem_undo
*un
= container_of(head
, struct sem_undo
, rcu
);
695 /* Free a semaphore set. freeary() is called with sem_ids.rw_mutex locked
696 * as a writer and the spinlock for this semaphore set hold. sem_ids.rw_mutex
697 * remains locked on exit.
699 static void freeary(struct ipc_namespace
*ns
, struct kern_ipc_perm
*ipcp
)
701 struct sem_undo
*un
, *tu
;
702 struct sem_queue
*q
, *tq
;
703 struct sem_array
*sma
= container_of(ipcp
, struct sem_array
, sem_perm
);
704 struct list_head tasks
;
706 /* Free the existing undo structures for this semaphore set. */
707 assert_spin_locked(&sma
->sem_perm
.lock
);
708 list_for_each_entry_safe(un
, tu
, &sma
->list_id
, list_id
) {
709 list_del(&un
->list_id
);
710 spin_lock(&un
->ulp
->lock
);
712 list_del_rcu(&un
->list_proc
);
713 spin_unlock(&un
->ulp
->lock
);
714 call_rcu(&un
->rcu
, free_un
);
717 /* Wake up all pending processes and let them fail with EIDRM. */
718 INIT_LIST_HEAD(&tasks
);
719 list_for_each_entry_safe(q
, tq
, &sma
->sem_pending
, list
) {
720 unlink_queue(sma
, q
);
721 wake_up_sem_queue_prepare(&tasks
, q
, -EIDRM
);
724 /* Remove the semaphore set from the IDR */
728 wake_up_sem_queue_do(&tasks
);
729 ns
->used_sems
-= sma
->sem_nsems
;
730 security_sem_free(sma
);
734 static unsigned long copy_semid_to_user(void __user
*buf
, struct semid64_ds
*in
, int version
)
738 return copy_to_user(buf
, in
, sizeof(*in
));
743 ipc64_perm_to_ipc_perm(&in
->sem_perm
, &out
.sem_perm
);
745 out
.sem_otime
= in
->sem_otime
;
746 out
.sem_ctime
= in
->sem_ctime
;
747 out
.sem_nsems
= in
->sem_nsems
;
749 return copy_to_user(buf
, &out
, sizeof(out
));
756 static int semctl_nolock(struct ipc_namespace
*ns
, int semid
,
757 int cmd
, int version
, union semun arg
)
760 struct sem_array
*sma
;
766 struct seminfo seminfo
;
769 err
= security_sem_semctl(NULL
, cmd
);
773 memset(&seminfo
,0,sizeof(seminfo
));
774 seminfo
.semmni
= ns
->sc_semmni
;
775 seminfo
.semmns
= ns
->sc_semmns
;
776 seminfo
.semmsl
= ns
->sc_semmsl
;
777 seminfo
.semopm
= ns
->sc_semopm
;
778 seminfo
.semvmx
= SEMVMX
;
779 seminfo
.semmnu
= SEMMNU
;
780 seminfo
.semmap
= SEMMAP
;
781 seminfo
.semume
= SEMUME
;
782 down_read(&sem_ids(ns
).rw_mutex
);
783 if (cmd
== SEM_INFO
) {
784 seminfo
.semusz
= sem_ids(ns
).in_use
;
785 seminfo
.semaem
= ns
->used_sems
;
787 seminfo
.semusz
= SEMUSZ
;
788 seminfo
.semaem
= SEMAEM
;
790 max_id
= ipc_get_maxid(&sem_ids(ns
));
791 up_read(&sem_ids(ns
).rw_mutex
);
792 if (copy_to_user (arg
.__buf
, &seminfo
, sizeof(struct seminfo
)))
794 return (max_id
< 0) ? 0: max_id
;
799 struct semid64_ds tbuf
;
802 if (cmd
== SEM_STAT
) {
803 sma
= sem_lock(ns
, semid
);
806 id
= sma
->sem_perm
.id
;
808 sma
= sem_lock_check(ns
, semid
);
815 if (ipcperms (&sma
->sem_perm
, S_IRUGO
))
818 err
= security_sem_semctl(sma
, cmd
);
822 memset(&tbuf
, 0, sizeof(tbuf
));
824 kernel_to_ipc64_perm(&sma
->sem_perm
, &tbuf
.sem_perm
);
825 tbuf
.sem_otime
= sma
->sem_otime
;
826 tbuf
.sem_ctime
= sma
->sem_ctime
;
827 tbuf
.sem_nsems
= sma
->sem_nsems
;
829 if (copy_semid_to_user (arg
.buf
, &tbuf
, version
))
841 static int semctl_main(struct ipc_namespace
*ns
, int semid
, int semnum
,
842 int cmd
, int version
, union semun arg
)
844 struct sem_array
*sma
;
847 ushort fast_sem_io
[SEMMSL_FAST
];
848 ushort
* sem_io
= fast_sem_io
;
850 struct list_head tasks
;
852 sma
= sem_lock_check(ns
, semid
);
856 INIT_LIST_HEAD(&tasks
);
857 nsems
= sma
->sem_nsems
;
860 if (ipcperms (&sma
->sem_perm
, (cmd
==SETVAL
||cmd
==SETALL
)?S_IWUGO
:S_IRUGO
))
863 err
= security_sem_semctl(sma
, cmd
);
871 ushort __user
*array
= arg
.array
;
874 if(nsems
> SEMMSL_FAST
) {
875 sem_getref_and_unlock(sma
);
877 sem_io
= ipc_alloc(sizeof(ushort
)*nsems
);
883 sem_lock_and_putref(sma
);
884 if (sma
->sem_perm
.deleted
) {
891 for (i
= 0; i
< sma
->sem_nsems
; i
++)
892 sem_io
[i
] = sma
->sem_base
[i
].semval
;
895 if(copy_to_user(array
, sem_io
, nsems
*sizeof(ushort
)))
904 sem_getref_and_unlock(sma
);
906 if(nsems
> SEMMSL_FAST
) {
907 sem_io
= ipc_alloc(sizeof(ushort
)*nsems
);
914 if (copy_from_user (sem_io
, arg
.array
, nsems
*sizeof(ushort
))) {
920 for (i
= 0; i
< nsems
; i
++) {
921 if (sem_io
[i
] > SEMVMX
) {
927 sem_lock_and_putref(sma
);
928 if (sma
->sem_perm
.deleted
) {
934 for (i
= 0; i
< nsems
; i
++)
935 sma
->sem_base
[i
].semval
= sem_io
[i
];
937 assert_spin_locked(&sma
->sem_perm
.lock
);
938 list_for_each_entry(un
, &sma
->list_id
, list_id
) {
939 for (i
= 0; i
< nsems
; i
++)
942 sma
->sem_ctime
= get_seconds();
943 /* maybe some queued-up processes were waiting for this */
944 do_smart_update(sma
, NULL
, 0, 0, &tasks
);
948 /* GETVAL, GETPID, GETNCTN, GETZCNT, SETVAL: fall-through */
951 if(semnum
< 0 || semnum
>= nsems
)
954 curr
= &sma
->sem_base
[semnum
];
964 err
= count_semncnt(sma
,semnum
);
967 err
= count_semzcnt(sma
,semnum
);
975 if (val
> SEMVMX
|| val
< 0)
978 assert_spin_locked(&sma
->sem_perm
.lock
);
979 list_for_each_entry(un
, &sma
->list_id
, list_id
)
980 un
->semadj
[semnum
] = 0;
983 curr
->sempid
= task_tgid_vnr(current
);
984 sma
->sem_ctime
= get_seconds();
985 /* maybe some queued-up processes were waiting for this */
986 do_smart_update(sma
, NULL
, 0, 0, &tasks
);
993 wake_up_sem_queue_do(&tasks
);
996 if(sem_io
!= fast_sem_io
)
997 ipc_free(sem_io
, sizeof(ushort
)*nsems
);
1001 static inline unsigned long
1002 copy_semid_from_user(struct semid64_ds
*out
, void __user
*buf
, int version
)
1006 if (copy_from_user(out
, buf
, sizeof(*out
)))
1011 struct semid_ds tbuf_old
;
1013 if(copy_from_user(&tbuf_old
, buf
, sizeof(tbuf_old
)))
1016 out
->sem_perm
.uid
= tbuf_old
.sem_perm
.uid
;
1017 out
->sem_perm
.gid
= tbuf_old
.sem_perm
.gid
;
1018 out
->sem_perm
.mode
= tbuf_old
.sem_perm
.mode
;
1028 * This function handles some semctl commands which require the rw_mutex
1029 * to be held in write mode.
1030 * NOTE: no locks must be held, the rw_mutex is taken inside this function.
1032 static int semctl_down(struct ipc_namespace
*ns
, int semid
,
1033 int cmd
, int version
, union semun arg
)
1035 struct sem_array
*sma
;
1037 struct semid64_ds semid64
;
1038 struct kern_ipc_perm
*ipcp
;
1040 if(cmd
== IPC_SET
) {
1041 if (copy_semid_from_user(&semid64
, arg
.buf
, version
))
1045 ipcp
= ipcctl_pre_down(&sem_ids(ns
), semid
, cmd
, &semid64
.sem_perm
, 0);
1047 return PTR_ERR(ipcp
);
1049 sma
= container_of(ipcp
, struct sem_array
, sem_perm
);
1051 err
= security_sem_semctl(sma
, cmd
);
1060 ipc_update_perm(&semid64
.sem_perm
, ipcp
);
1061 sma
->sem_ctime
= get_seconds();
1070 up_write(&sem_ids(ns
).rw_mutex
);
1074 SYSCALL_DEFINE(semctl
)(int semid
, int semnum
, int cmd
, union semun arg
)
1078 struct ipc_namespace
*ns
;
1083 version
= ipc_parse_version(&cmd
);
1084 ns
= current
->nsproxy
->ipc_ns
;
1091 err
= semctl_nolock(ns
, semid
, cmd
, version
, arg
);
1100 err
= semctl_main(ns
,semid
,semnum
,cmd
,version
,arg
);
1104 err
= semctl_down(ns
, semid
, cmd
, version
, arg
);
1110 #ifdef CONFIG_HAVE_SYSCALL_WRAPPERS
1111 asmlinkage
long SyS_semctl(int semid
, int semnum
, int cmd
, union semun arg
)
1113 return SYSC_semctl((int) semid
, (int) semnum
, (int) cmd
, arg
);
1115 SYSCALL_ALIAS(sys_semctl
, SyS_semctl
);
1118 /* If the task doesn't already have a undo_list, then allocate one
1119 * here. We guarantee there is only one thread using this undo list,
1120 * and current is THE ONE
1122 * If this allocation and assignment succeeds, but later
1123 * portions of this code fail, there is no need to free the sem_undo_list.
1124 * Just let it stay associated with the task, and it'll be freed later
1127 * This can block, so callers must hold no locks.
1129 static inline int get_undo_list(struct sem_undo_list
**undo_listp
)
1131 struct sem_undo_list
*undo_list
;
1133 undo_list
= current
->sysvsem
.undo_list
;
1135 undo_list
= kzalloc(sizeof(*undo_list
), GFP_KERNEL
);
1136 if (undo_list
== NULL
)
1138 spin_lock_init(&undo_list
->lock
);
1139 atomic_set(&undo_list
->refcnt
, 1);
1140 INIT_LIST_HEAD(&undo_list
->list_proc
);
1142 current
->sysvsem
.undo_list
= undo_list
;
1144 *undo_listp
= undo_list
;
1148 static struct sem_undo
*__lookup_undo(struct sem_undo_list
*ulp
, int semid
)
1150 struct sem_undo
*un
;
1152 list_for_each_entry_rcu(un
, &ulp
->list_proc
, list_proc
) {
1153 if (un
->semid
== semid
)
1159 static struct sem_undo
*lookup_undo(struct sem_undo_list
*ulp
, int semid
)
1161 struct sem_undo
*un
;
1163 assert_spin_locked(&ulp
->lock
);
1165 un
= __lookup_undo(ulp
, semid
);
1167 list_del_rcu(&un
->list_proc
);
1168 list_add_rcu(&un
->list_proc
, &ulp
->list_proc
);
1174 * find_alloc_undo - Lookup (and if not present create) undo array
1176 * @semid: semaphore array id
1178 * The function looks up (and if not present creates) the undo structure.
1179 * The size of the undo structure depends on the size of the semaphore
1180 * array, thus the alloc path is not that straightforward.
1181 * Lifetime-rules: sem_undo is rcu-protected, on success, the function
1182 * performs a rcu_read_lock().
1184 static struct sem_undo
*find_alloc_undo(struct ipc_namespace
*ns
, int semid
)
1186 struct sem_array
*sma
;
1187 struct sem_undo_list
*ulp
;
1188 struct sem_undo
*un
, *new;
1192 error
= get_undo_list(&ulp
);
1194 return ERR_PTR(error
);
1197 spin_lock(&ulp
->lock
);
1198 un
= lookup_undo(ulp
, semid
);
1199 spin_unlock(&ulp
->lock
);
1200 if (likely(un
!=NULL
))
1204 /* no undo structure around - allocate one. */
1205 /* step 1: figure out the size of the semaphore array */
1206 sma
= sem_lock_check(ns
, semid
);
1208 return ERR_PTR(PTR_ERR(sma
));
1210 nsems
= sma
->sem_nsems
;
1211 sem_getref_and_unlock(sma
);
1213 /* step 2: allocate new undo structure */
1214 new = kzalloc(sizeof(struct sem_undo
) + sizeof(short)*nsems
, GFP_KERNEL
);
1217 return ERR_PTR(-ENOMEM
);
1220 /* step 3: Acquire the lock on semaphore array */
1221 sem_lock_and_putref(sma
);
1222 if (sma
->sem_perm
.deleted
) {
1225 un
= ERR_PTR(-EIDRM
);
1228 spin_lock(&ulp
->lock
);
1231 * step 4: check for races: did someone else allocate the undo struct?
1233 un
= lookup_undo(ulp
, semid
);
1238 /* step 5: initialize & link new undo structure */
1239 new->semadj
= (short *) &new[1];
1242 assert_spin_locked(&ulp
->lock
);
1243 list_add_rcu(&new->list_proc
, &ulp
->list_proc
);
1244 assert_spin_locked(&sma
->sem_perm
.lock
);
1245 list_add(&new->list_id
, &sma
->list_id
);
1249 spin_unlock(&ulp
->lock
);
1256 SYSCALL_DEFINE4(semtimedop
, int, semid
, struct sembuf __user
*, tsops
,
1257 unsigned, nsops
, const struct timespec __user
*, timeout
)
1259 int error
= -EINVAL
;
1260 struct sem_array
*sma
;
1261 struct sembuf fast_sops
[SEMOPM_FAST
];
1262 struct sembuf
* sops
= fast_sops
, *sop
;
1263 struct sem_undo
*un
;
1264 int undos
= 0, alter
= 0, max
;
1265 struct sem_queue queue
;
1266 unsigned long jiffies_left
= 0;
1267 struct ipc_namespace
*ns
;
1268 struct list_head tasks
;
1270 ns
= current
->nsproxy
->ipc_ns
;
1272 if (nsops
< 1 || semid
< 0)
1274 if (nsops
> ns
->sc_semopm
)
1276 if(nsops
> SEMOPM_FAST
) {
1277 sops
= kmalloc(sizeof(*sops
)*nsops
,GFP_KERNEL
);
1281 if (copy_from_user (sops
, tsops
, nsops
* sizeof(*tsops
))) {
1286 struct timespec _timeout
;
1287 if (copy_from_user(&_timeout
, timeout
, sizeof(*timeout
))) {
1291 if (_timeout
.tv_sec
< 0 || _timeout
.tv_nsec
< 0 ||
1292 _timeout
.tv_nsec
>= 1000000000L) {
1296 jiffies_left
= timespec_to_jiffies(&_timeout
);
1299 for (sop
= sops
; sop
< sops
+ nsops
; sop
++) {
1300 if (sop
->sem_num
>= max
)
1302 if (sop
->sem_flg
& SEM_UNDO
)
1304 if (sop
->sem_op
!= 0)
1309 un
= find_alloc_undo(ns
, semid
);
1311 error
= PTR_ERR(un
);
1317 INIT_LIST_HEAD(&tasks
);
1319 sma
= sem_lock_check(ns
, semid
);
1323 error
= PTR_ERR(sma
);
1328 * semid identifiers are not unique - find_alloc_undo may have
1329 * allocated an undo structure, it was invalidated by an RMID
1330 * and now a new array with received the same id. Check and fail.
1331 * This case can be detected checking un->semid. The existance of
1332 * "un" itself is guaranteed by rcu.
1336 if (un
->semid
== -1) {
1338 goto out_unlock_free
;
1341 * rcu lock can be released, "un" cannot disappear:
1342 * - sem_lock is acquired, thus IPC_RMID is
1344 * - exit_sem is impossible, it always operates on
1345 * current (or a dead task).
1353 if (max
>= sma
->sem_nsems
)
1354 goto out_unlock_free
;
1357 if (ipcperms(&sma
->sem_perm
, alter
? S_IWUGO
: S_IRUGO
))
1358 goto out_unlock_free
;
1360 error
= security_sem_semop(sma
, sops
, nsops
, alter
);
1362 goto out_unlock_free
;
1364 error
= try_atomic_semop (sma
, sops
, nsops
, un
, task_tgid_vnr(current
));
1366 if (alter
&& error
== 0)
1367 do_smart_update(sma
, sops
, nsops
, 1, &tasks
);
1369 goto out_unlock_free
;
1372 /* We need to sleep on this operation, so we put the current
1373 * task into the pending queue and go to sleep.
1377 queue
.nsops
= nsops
;
1379 queue
.pid
= task_tgid_vnr(current
);
1380 queue
.alter
= alter
;
1382 list_add_tail(&queue
.list
, &sma
->sem_pending
);
1384 list_add(&queue
.list
, &sma
->sem_pending
);
1388 curr
= &sma
->sem_base
[sops
->sem_num
];
1391 list_add_tail(&queue
.simple_list
, &curr
->sem_pending
);
1393 list_add(&queue
.simple_list
, &curr
->sem_pending
);
1395 INIT_LIST_HEAD(&queue
.simple_list
);
1396 sma
->complex_count
++;
1399 queue
.status
= -EINTR
;
1400 queue
.sleeper
= current
;
1401 current
->state
= TASK_INTERRUPTIBLE
;
1405 jiffies_left
= schedule_timeout(jiffies_left
);
1409 error
= queue
.status
;
1410 while(unlikely(error
== IN_WAKEUP
)) {
1412 error
= queue
.status
;
1415 if (error
!= -EINTR
) {
1416 /* fast path: update_queue already obtained all requested
1421 sma
= sem_lock(ns
, semid
);
1428 * If queue.status != -EINTR we are woken up by another process
1430 error
= queue
.status
;
1431 if (error
!= -EINTR
) {
1432 goto out_unlock_free
;
1436 * If an interrupt occurred we have to clean up the queue
1438 if (timeout
&& jiffies_left
== 0)
1440 unlink_queue(sma
, &queue
);
1445 wake_up_sem_queue_do(&tasks
);
1447 if(sops
!= fast_sops
)
1452 SYSCALL_DEFINE3(semop
, int, semid
, struct sembuf __user
*, tsops
,
1455 return sys_semtimedop(semid
, tsops
, nsops
, NULL
);
1458 /* If CLONE_SYSVSEM is set, establish sharing of SEM_UNDO state between
1459 * parent and child tasks.
1462 int copy_semundo(unsigned long clone_flags
, struct task_struct
*tsk
)
1464 struct sem_undo_list
*undo_list
;
1467 if (clone_flags
& CLONE_SYSVSEM
) {
1468 error
= get_undo_list(&undo_list
);
1471 atomic_inc(&undo_list
->refcnt
);
1472 tsk
->sysvsem
.undo_list
= undo_list
;
1474 tsk
->sysvsem
.undo_list
= NULL
;
1480 * add semadj values to semaphores, free undo structures.
1481 * undo structures are not freed when semaphore arrays are destroyed
1482 * so some of them may be out of date.
1483 * IMPLEMENTATION NOTE: There is some confusion over whether the
1484 * set of adjustments that needs to be done should be done in an atomic
1485 * manner or not. That is, if we are attempting to decrement the semval
1486 * should we queue up and wait until we can do so legally?
1487 * The original implementation attempted to do this (queue and wait).
1488 * The current implementation does not do so. The POSIX standard
1489 * and SVID should be consulted to determine what behavior is mandated.
1491 void exit_sem(struct task_struct
*tsk
)
1493 struct sem_undo_list
*ulp
;
1495 ulp
= tsk
->sysvsem
.undo_list
;
1498 tsk
->sysvsem
.undo_list
= NULL
;
1500 if (!atomic_dec_and_test(&ulp
->refcnt
))
1504 struct sem_array
*sma
;
1505 struct sem_undo
*un
;
1506 struct list_head tasks
;
1511 un
= list_entry_rcu(ulp
->list_proc
.next
,
1512 struct sem_undo
, list_proc
);
1513 if (&un
->list_proc
== &ulp
->list_proc
)
1522 sma
= sem_lock_check(tsk
->nsproxy
->ipc_ns
, un
->semid
);
1524 /* exit_sem raced with IPC_RMID, nothing to do */
1528 un
= __lookup_undo(ulp
, semid
);
1530 /* exit_sem raced with IPC_RMID+semget() that created
1531 * exactly the same semid. Nothing to do.
1537 /* remove un from the linked lists */
1538 assert_spin_locked(&sma
->sem_perm
.lock
);
1539 list_del(&un
->list_id
);
1541 spin_lock(&ulp
->lock
);
1542 list_del_rcu(&un
->list_proc
);
1543 spin_unlock(&ulp
->lock
);
1545 /* perform adjustments registered in un */
1546 for (i
= 0; i
< sma
->sem_nsems
; i
++) {
1547 struct sem
* semaphore
= &sma
->sem_base
[i
];
1548 if (un
->semadj
[i
]) {
1549 semaphore
->semval
+= un
->semadj
[i
];
1551 * Range checks of the new semaphore value,
1552 * not defined by sus:
1553 * - Some unices ignore the undo entirely
1554 * (e.g. HP UX 11i 11.22, Tru64 V5.1)
1555 * - some cap the value (e.g. FreeBSD caps
1556 * at 0, but doesn't enforce SEMVMX)
1558 * Linux caps the semaphore value, both at 0
1561 * Manfred <manfred@colorfullife.com>
1563 if (semaphore
->semval
< 0)
1564 semaphore
->semval
= 0;
1565 if (semaphore
->semval
> SEMVMX
)
1566 semaphore
->semval
= SEMVMX
;
1567 semaphore
->sempid
= task_tgid_vnr(current
);
1570 /* maybe some queued-up processes were waiting for this */
1571 INIT_LIST_HEAD(&tasks
);
1572 do_smart_update(sma
, NULL
, 0, 1, &tasks
);
1574 wake_up_sem_queue_do(&tasks
);
1576 call_rcu(&un
->rcu
, free_un
);
1581 #ifdef CONFIG_PROC_FS
1582 static int sysvipc_sem_proc_show(struct seq_file
*s
, void *it
)
1584 struct sem_array
*sma
= it
;
1586 return seq_printf(s
,
1587 "%10d %10d %4o %10u %5u %5u %5u %5u %10lu %10lu\n",