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
);
135 void __init
sem_init (void)
137 sem_init_ns(&init_ipc_ns
);
138 ipc_init_proc_interface("sysvipc/sem",
139 " key semid perms nsems uid gid cuid cgid otime ctime\n",
140 IPC_SEM_IDS
, sysvipc_sem_proc_show
);
144 * sem_lock_(check_) routines are called in the paths where the rw_mutex
147 static inline struct sem_array
*sem_lock(struct ipc_namespace
*ns
, int id
)
149 struct kern_ipc_perm
*ipcp
= ipc_lock(&sem_ids(ns
), id
);
152 return (struct sem_array
*)ipcp
;
154 return container_of(ipcp
, struct sem_array
, sem_perm
);
157 static inline struct sem_array
*sem_lock_check(struct ipc_namespace
*ns
,
160 struct kern_ipc_perm
*ipcp
= ipc_lock_check(&sem_ids(ns
), id
);
163 return (struct sem_array
*)ipcp
;
165 return container_of(ipcp
, struct sem_array
, sem_perm
);
168 static inline void sem_lock_and_putref(struct sem_array
*sma
)
170 ipc_lock_by_ptr(&sma
->sem_perm
);
174 static inline void sem_getref_and_unlock(struct sem_array
*sma
)
177 ipc_unlock(&(sma
)->sem_perm
);
180 static inline void sem_putref(struct sem_array
*sma
)
182 ipc_lock_by_ptr(&sma
->sem_perm
);
184 ipc_unlock(&(sma
)->sem_perm
);
187 static inline void sem_rmid(struct ipc_namespace
*ns
, struct sem_array
*s
)
189 ipc_rmid(&sem_ids(ns
), &s
->sem_perm
);
193 * Lockless wakeup algorithm:
194 * Without the check/retry algorithm a lockless wakeup is possible:
195 * - queue.status is initialized to -EINTR before blocking.
196 * - wakeup is performed by
197 * * unlinking the queue entry from sma->sem_pending
198 * * setting queue.status to IN_WAKEUP
199 * This is the notification for the blocked thread that a
200 * result value is imminent.
201 * * call wake_up_process
202 * * set queue.status to the final value.
203 * - the previously blocked thread checks queue.status:
204 * * if it's IN_WAKEUP, then it must wait until the value changes
205 * * if it's not -EINTR, then the operation was completed by
206 * update_queue. semtimedop can return queue.status without
207 * performing any operation on the sem array.
208 * * otherwise it must acquire the spinlock and check what's up.
210 * The two-stage algorithm is necessary to protect against the following
212 * - if queue.status is set after wake_up_process, then the woken up idle
213 * thread could race forward and try (and fail) to acquire sma->lock
214 * before update_queue had a chance to set queue.status
215 * - if queue.status is written before wake_up_process and if the
216 * blocked process is woken up by a signal between writing
217 * queue.status and the wake_up_process, then the woken up
218 * process could return from semtimedop and die by calling
219 * sys_exit before wake_up_process is called. Then wake_up_process
220 * will oops, because the task structure is already invalid.
221 * (yes, this happened on s390 with sysv msg).
227 * newary - Create a new semaphore set
229 * @params: ptr to the structure that contains key, semflg and nsems
231 * Called with sem_ids.rw_mutex held (as a writer)
234 static int newary(struct ipc_namespace
*ns
, struct ipc_params
*params
)
238 struct sem_array
*sma
;
240 key_t key
= params
->key
;
241 int nsems
= params
->u
.nsems
;
242 int semflg
= params
->flg
;
246 if (ns
->used_sems
+ nsems
> ns
->sc_semmns
)
249 size
= sizeof (*sma
) + nsems
* sizeof (struct sem
);
250 sma
= ipc_rcu_alloc(size
);
254 memset (sma
, 0, size
);
256 sma
->sem_perm
.mode
= (semflg
& S_IRWXUGO
);
257 sma
->sem_perm
.key
= key
;
259 sma
->sem_perm
.security
= NULL
;
260 retval
= security_sem_alloc(sma
);
266 id
= ipc_addid(&sem_ids(ns
), &sma
->sem_perm
, ns
->sc_semmni
);
268 security_sem_free(sma
);
272 ns
->used_sems
+= nsems
;
274 sma
->sem_base
= (struct sem
*) &sma
[1];
275 INIT_LIST_HEAD(&sma
->sem_pending
);
276 INIT_LIST_HEAD(&sma
->list_id
);
277 sma
->sem_nsems
= nsems
;
278 sma
->sem_ctime
= get_seconds();
281 return sma
->sem_perm
.id
;
286 * Called with sem_ids.rw_mutex and ipcp locked.
288 static inline int sem_security(struct kern_ipc_perm
*ipcp
, int semflg
)
290 struct sem_array
*sma
;
292 sma
= container_of(ipcp
, struct sem_array
, sem_perm
);
293 return security_sem_associate(sma
, semflg
);
297 * Called with sem_ids.rw_mutex and ipcp locked.
299 static inline int sem_more_checks(struct kern_ipc_perm
*ipcp
,
300 struct ipc_params
*params
)
302 struct sem_array
*sma
;
304 sma
= container_of(ipcp
, struct sem_array
, sem_perm
);
305 if (params
->u
.nsems
> sma
->sem_nsems
)
311 SYSCALL_DEFINE3(semget
, key_t
, key
, int, nsems
, int, semflg
)
313 struct ipc_namespace
*ns
;
314 struct ipc_ops sem_ops
;
315 struct ipc_params sem_params
;
317 ns
= current
->nsproxy
->ipc_ns
;
319 if (nsems
< 0 || nsems
> ns
->sc_semmsl
)
322 sem_ops
.getnew
= newary
;
323 sem_ops
.associate
= sem_security
;
324 sem_ops
.more_checks
= sem_more_checks
;
326 sem_params
.key
= key
;
327 sem_params
.flg
= semflg
;
328 sem_params
.u
.nsems
= nsems
;
330 return ipcget(ns
, &sem_ids(ns
), &sem_ops
, &sem_params
);
334 * Determine whether a sequence of semaphore operations would succeed
335 * all at once. Return 0 if yes, 1 if need to sleep, else return error code.
338 static int try_atomic_semop (struct sem_array
* sma
, struct sembuf
* sops
,
339 int nsops
, struct sem_undo
*un
, int pid
)
345 for (sop
= sops
; sop
< sops
+ nsops
; sop
++) {
346 curr
= sma
->sem_base
+ sop
->sem_num
;
347 sem_op
= sop
->sem_op
;
348 result
= curr
->semval
;
350 if (!sem_op
&& result
)
358 if (sop
->sem_flg
& SEM_UNDO
) {
359 int undo
= un
->semadj
[sop
->sem_num
] - sem_op
;
361 * Exceeding the undo range is an error.
363 if (undo
< (-SEMAEM
- 1) || undo
> SEMAEM
)
366 curr
->semval
= result
;
370 while (sop
>= sops
) {
371 sma
->sem_base
[sop
->sem_num
].sempid
= pid
;
372 if (sop
->sem_flg
& SEM_UNDO
)
373 un
->semadj
[sop
->sem_num
] -= sop
->sem_op
;
377 sma
->sem_otime
= get_seconds();
385 if (sop
->sem_flg
& IPC_NOWAIT
)
392 while (sop
>= sops
) {
393 sma
->sem_base
[sop
->sem_num
].semval
-= sop
->sem_op
;
400 /* Go through the pending queue for the indicated semaphore
401 * looking for tasks that can be completed.
403 static void update_queue (struct sem_array
* sma
)
406 struct sem_queue
* q
;
408 q
= list_entry(sma
->sem_pending
.next
, struct sem_queue
, list
);
409 while (&q
->list
!= &sma
->sem_pending
) {
410 error
= try_atomic_semop(sma
, q
->sops
, q
->nsops
,
413 /* Does q->sleeper still need to sleep? */
418 * Continue scanning. The next operation
419 * that must be checked depends on the type of the
420 * completed operation:
421 * - if the operation modified the array, then
422 * restart from the head of the queue and
423 * check for threads that might be waiting
424 * for semaphore values to become 0.
425 * - if the operation didn't modify the array,
426 * then just continue.
427 * The order of list_del() and reading ->next
428 * is crucial: In the former case, the list_del()
429 * must be done first [because we might be the
430 * first entry in ->sem_pending], in the latter
431 * case the list_del() must be done last
432 * [because the list is invalid after the list_del()]
436 n
= list_entry(sma
->sem_pending
.next
,
437 struct sem_queue
, list
);
439 n
= list_entry(q
->list
.next
, struct sem_queue
,
444 /* wake up the waiting thread */
445 q
->status
= IN_WAKEUP
;
447 wake_up_process(q
->sleeper
);
448 /* hands-off: q will disappear immediately after
455 q
= list_entry(q
->list
.next
, struct sem_queue
, list
);
460 /* The following counts are associated to each semaphore:
461 * semncnt number of tasks waiting on semval being nonzero
462 * semzcnt number of tasks waiting on semval being zero
463 * This model assumes that a task waits on exactly one semaphore.
464 * Since semaphore operations are to be performed atomically, tasks actually
465 * wait on a whole sequence of semaphores simultaneously.
466 * The counts we return here are a rough approximation, but still
467 * warrant that semncnt+semzcnt>0 if the task is on the pending queue.
469 static int count_semncnt (struct sem_array
* sma
, ushort semnum
)
472 struct sem_queue
* q
;
475 list_for_each_entry(q
, &sma
->sem_pending
, list
) {
476 struct sembuf
* sops
= q
->sops
;
477 int nsops
= q
->nsops
;
479 for (i
= 0; i
< nsops
; i
++)
480 if (sops
[i
].sem_num
== semnum
481 && (sops
[i
].sem_op
< 0)
482 && !(sops
[i
].sem_flg
& IPC_NOWAIT
))
488 static int count_semzcnt (struct sem_array
* sma
, ushort semnum
)
491 struct sem_queue
* q
;
494 list_for_each_entry(q
, &sma
->sem_pending
, list
) {
495 struct sembuf
* sops
= q
->sops
;
496 int nsops
= q
->nsops
;
498 for (i
= 0; i
< nsops
; i
++)
499 if (sops
[i
].sem_num
== semnum
500 && (sops
[i
].sem_op
== 0)
501 && !(sops
[i
].sem_flg
& IPC_NOWAIT
))
507 static void free_un(struct rcu_head
*head
)
509 struct sem_undo
*un
= container_of(head
, struct sem_undo
, rcu
);
513 /* Free a semaphore set. freeary() is called with sem_ids.rw_mutex locked
514 * as a writer and the spinlock for this semaphore set hold. sem_ids.rw_mutex
515 * remains locked on exit.
517 static void freeary(struct ipc_namespace
*ns
, struct kern_ipc_perm
*ipcp
)
519 struct sem_undo
*un
, *tu
;
520 struct sem_queue
*q
, *tq
;
521 struct sem_array
*sma
= container_of(ipcp
, struct sem_array
, sem_perm
);
523 /* Free the existing undo structures for this semaphore set. */
524 assert_spin_locked(&sma
->sem_perm
.lock
);
525 list_for_each_entry_safe(un
, tu
, &sma
->list_id
, list_id
) {
526 list_del(&un
->list_id
);
527 spin_lock(&un
->ulp
->lock
);
529 list_del_rcu(&un
->list_proc
);
530 spin_unlock(&un
->ulp
->lock
);
531 call_rcu(&un
->rcu
, free_un
);
534 /* Wake up all pending processes and let them fail with EIDRM. */
535 list_for_each_entry_safe(q
, tq
, &sma
->sem_pending
, list
) {
538 q
->status
= IN_WAKEUP
;
539 wake_up_process(q
->sleeper
); /* doesn't sleep */
541 q
->status
= -EIDRM
; /* hands-off q */
544 /* Remove the semaphore set from the IDR */
548 ns
->used_sems
-= sma
->sem_nsems
;
549 security_sem_free(sma
);
553 static unsigned long copy_semid_to_user(void __user
*buf
, struct semid64_ds
*in
, int version
)
557 return copy_to_user(buf
, in
, sizeof(*in
));
562 ipc64_perm_to_ipc_perm(&in
->sem_perm
, &out
.sem_perm
);
564 out
.sem_otime
= in
->sem_otime
;
565 out
.sem_ctime
= in
->sem_ctime
;
566 out
.sem_nsems
= in
->sem_nsems
;
568 return copy_to_user(buf
, &out
, sizeof(out
));
575 static int semctl_nolock(struct ipc_namespace
*ns
, int semid
,
576 int cmd
, int version
, union semun arg
)
579 struct sem_array
*sma
;
585 struct seminfo seminfo
;
588 err
= security_sem_semctl(NULL
, cmd
);
592 memset(&seminfo
,0,sizeof(seminfo
));
593 seminfo
.semmni
= ns
->sc_semmni
;
594 seminfo
.semmns
= ns
->sc_semmns
;
595 seminfo
.semmsl
= ns
->sc_semmsl
;
596 seminfo
.semopm
= ns
->sc_semopm
;
597 seminfo
.semvmx
= SEMVMX
;
598 seminfo
.semmnu
= SEMMNU
;
599 seminfo
.semmap
= SEMMAP
;
600 seminfo
.semume
= SEMUME
;
601 down_read(&sem_ids(ns
).rw_mutex
);
602 if (cmd
== SEM_INFO
) {
603 seminfo
.semusz
= sem_ids(ns
).in_use
;
604 seminfo
.semaem
= ns
->used_sems
;
606 seminfo
.semusz
= SEMUSZ
;
607 seminfo
.semaem
= SEMAEM
;
609 max_id
= ipc_get_maxid(&sem_ids(ns
));
610 up_read(&sem_ids(ns
).rw_mutex
);
611 if (copy_to_user (arg
.__buf
, &seminfo
, sizeof(struct seminfo
)))
613 return (max_id
< 0) ? 0: max_id
;
618 struct semid64_ds tbuf
;
621 if (cmd
== SEM_STAT
) {
622 sma
= sem_lock(ns
, semid
);
625 id
= sma
->sem_perm
.id
;
627 sma
= sem_lock_check(ns
, semid
);
634 if (ipcperms (&sma
->sem_perm
, S_IRUGO
))
637 err
= security_sem_semctl(sma
, cmd
);
641 memset(&tbuf
, 0, sizeof(tbuf
));
643 kernel_to_ipc64_perm(&sma
->sem_perm
, &tbuf
.sem_perm
);
644 tbuf
.sem_otime
= sma
->sem_otime
;
645 tbuf
.sem_ctime
= sma
->sem_ctime
;
646 tbuf
.sem_nsems
= sma
->sem_nsems
;
648 if (copy_semid_to_user (arg
.buf
, &tbuf
, version
))
661 static int semctl_main(struct ipc_namespace
*ns
, int semid
, int semnum
,
662 int cmd
, int version
, union semun arg
)
664 struct sem_array
*sma
;
667 ushort fast_sem_io
[SEMMSL_FAST
];
668 ushort
* sem_io
= fast_sem_io
;
671 sma
= sem_lock_check(ns
, semid
);
675 nsems
= sma
->sem_nsems
;
678 if (ipcperms (&sma
->sem_perm
, (cmd
==SETVAL
||cmd
==SETALL
)?S_IWUGO
:S_IRUGO
))
681 err
= security_sem_semctl(sma
, cmd
);
689 ushort __user
*array
= arg
.array
;
692 if(nsems
> SEMMSL_FAST
) {
693 sem_getref_and_unlock(sma
);
695 sem_io
= ipc_alloc(sizeof(ushort
)*nsems
);
701 sem_lock_and_putref(sma
);
702 if (sma
->sem_perm
.deleted
) {
709 for (i
= 0; i
< sma
->sem_nsems
; i
++)
710 sem_io
[i
] = sma
->sem_base
[i
].semval
;
713 if(copy_to_user(array
, sem_io
, nsems
*sizeof(ushort
)))
722 sem_getref_and_unlock(sma
);
724 if(nsems
> SEMMSL_FAST
) {
725 sem_io
= ipc_alloc(sizeof(ushort
)*nsems
);
732 if (copy_from_user (sem_io
, arg
.array
, nsems
*sizeof(ushort
))) {
738 for (i
= 0; i
< nsems
; i
++) {
739 if (sem_io
[i
] > SEMVMX
) {
745 sem_lock_and_putref(sma
);
746 if (sma
->sem_perm
.deleted
) {
752 for (i
= 0; i
< nsems
; i
++)
753 sma
->sem_base
[i
].semval
= sem_io
[i
];
755 assert_spin_locked(&sma
->sem_perm
.lock
);
756 list_for_each_entry(un
, &sma
->list_id
, list_id
) {
757 for (i
= 0; i
< nsems
; i
++)
760 sma
->sem_ctime
= get_seconds();
761 /* maybe some queued-up processes were waiting for this */
766 /* GETVAL, GETPID, GETNCTN, GETZCNT, SETVAL: fall-through */
769 if(semnum
< 0 || semnum
>= nsems
)
772 curr
= &sma
->sem_base
[semnum
];
782 err
= count_semncnt(sma
,semnum
);
785 err
= count_semzcnt(sma
,semnum
);
793 if (val
> SEMVMX
|| val
< 0)
796 assert_spin_locked(&sma
->sem_perm
.lock
);
797 list_for_each_entry(un
, &sma
->list_id
, list_id
)
798 un
->semadj
[semnum
] = 0;
801 curr
->sempid
= task_tgid_vnr(current
);
802 sma
->sem_ctime
= get_seconds();
803 /* maybe some queued-up processes were waiting for this */
812 if(sem_io
!= fast_sem_io
)
813 ipc_free(sem_io
, sizeof(ushort
)*nsems
);
817 static inline unsigned long
818 copy_semid_from_user(struct semid64_ds
*out
, void __user
*buf
, int version
)
822 if (copy_from_user(out
, buf
, sizeof(*out
)))
827 struct semid_ds tbuf_old
;
829 if(copy_from_user(&tbuf_old
, buf
, sizeof(tbuf_old
)))
832 out
->sem_perm
.uid
= tbuf_old
.sem_perm
.uid
;
833 out
->sem_perm
.gid
= tbuf_old
.sem_perm
.gid
;
834 out
->sem_perm
.mode
= tbuf_old
.sem_perm
.mode
;
844 * This function handles some semctl commands which require the rw_mutex
845 * to be held in write mode.
846 * NOTE: no locks must be held, the rw_mutex is taken inside this function.
848 static int semctl_down(struct ipc_namespace
*ns
, int semid
,
849 int cmd
, int version
, union semun arg
)
851 struct sem_array
*sma
;
853 struct semid64_ds semid64
;
854 struct kern_ipc_perm
*ipcp
;
857 if (copy_semid_from_user(&semid64
, arg
.buf
, version
))
861 ipcp
= ipcctl_pre_down(&sem_ids(ns
), semid
, cmd
, &semid64
.sem_perm
, 0);
863 return PTR_ERR(ipcp
);
865 sma
= container_of(ipcp
, struct sem_array
, sem_perm
);
867 err
= security_sem_semctl(sma
, cmd
);
876 ipc_update_perm(&semid64
.sem_perm
, ipcp
);
877 sma
->sem_ctime
= get_seconds();
886 up_write(&sem_ids(ns
).rw_mutex
);
890 SYSCALL_DEFINE(semctl
)(int semid
, int semnum
, int cmd
, union semun arg
)
894 struct ipc_namespace
*ns
;
899 version
= ipc_parse_version(&cmd
);
900 ns
= current
->nsproxy
->ipc_ns
;
907 err
= semctl_nolock(ns
, semid
, cmd
, version
, arg
);
916 err
= semctl_main(ns
,semid
,semnum
,cmd
,version
,arg
);
920 err
= semctl_down(ns
, semid
, cmd
, version
, arg
);
926 #ifdef CONFIG_HAVE_SYSCALL_WRAPPERS
927 asmlinkage
long SyS_semctl(int semid
, int semnum
, int cmd
, union semun arg
)
929 return SYSC_semctl((int) semid
, (int) semnum
, (int) cmd
, arg
);
931 SYSCALL_ALIAS(sys_semctl
, SyS_semctl
);
934 /* If the task doesn't already have a undo_list, then allocate one
935 * here. We guarantee there is only one thread using this undo list,
936 * and current is THE ONE
938 * If this allocation and assignment succeeds, but later
939 * portions of this code fail, there is no need to free the sem_undo_list.
940 * Just let it stay associated with the task, and it'll be freed later
943 * This can block, so callers must hold no locks.
945 static inline int get_undo_list(struct sem_undo_list
**undo_listp
)
947 struct sem_undo_list
*undo_list
;
949 undo_list
= current
->sysvsem
.undo_list
;
951 undo_list
= kzalloc(sizeof(*undo_list
), GFP_KERNEL
);
952 if (undo_list
== NULL
)
954 spin_lock_init(&undo_list
->lock
);
955 atomic_set(&undo_list
->refcnt
, 1);
956 INIT_LIST_HEAD(&undo_list
->list_proc
);
958 current
->sysvsem
.undo_list
= undo_list
;
960 *undo_listp
= undo_list
;
964 static struct sem_undo
*lookup_undo(struct sem_undo_list
*ulp
, int semid
)
966 struct sem_undo
*walk
;
968 list_for_each_entry_rcu(walk
, &ulp
->list_proc
, list_proc
) {
969 if (walk
->semid
== semid
)
976 * find_alloc_undo - Lookup (and if not present create) undo array
978 * @semid: semaphore array id
980 * The function looks up (and if not present creates) the undo structure.
981 * The size of the undo structure depends on the size of the semaphore
982 * array, thus the alloc path is not that straightforward.
983 * Lifetime-rules: sem_undo is rcu-protected, on success, the function
984 * performs a rcu_read_lock().
986 static struct sem_undo
*find_alloc_undo(struct ipc_namespace
*ns
, int semid
)
988 struct sem_array
*sma
;
989 struct sem_undo_list
*ulp
;
990 struct sem_undo
*un
, *new;
994 error
= get_undo_list(&ulp
);
996 return ERR_PTR(error
);
999 spin_lock(&ulp
->lock
);
1000 un
= lookup_undo(ulp
, semid
);
1001 spin_unlock(&ulp
->lock
);
1002 if (likely(un
!=NULL
))
1006 /* no undo structure around - allocate one. */
1007 /* step 1: figure out the size of the semaphore array */
1008 sma
= sem_lock_check(ns
, semid
);
1010 return ERR_PTR(PTR_ERR(sma
));
1012 nsems
= sma
->sem_nsems
;
1013 sem_getref_and_unlock(sma
);
1015 /* step 2: allocate new undo structure */
1016 new = kzalloc(sizeof(struct sem_undo
) + sizeof(short)*nsems
, GFP_KERNEL
);
1019 return ERR_PTR(-ENOMEM
);
1022 /* step 3: Acquire the lock on semaphore array */
1023 sem_lock_and_putref(sma
);
1024 if (sma
->sem_perm
.deleted
) {
1027 un
= ERR_PTR(-EIDRM
);
1030 spin_lock(&ulp
->lock
);
1033 * step 4: check for races: did someone else allocate the undo struct?
1035 un
= lookup_undo(ulp
, semid
);
1040 /* step 5: initialize & link new undo structure */
1041 new->semadj
= (short *) &new[1];
1044 assert_spin_locked(&ulp
->lock
);
1045 list_add_rcu(&new->list_proc
, &ulp
->list_proc
);
1046 assert_spin_locked(&sma
->sem_perm
.lock
);
1047 list_add(&new->list_id
, &sma
->list_id
);
1051 spin_unlock(&ulp
->lock
);
1058 SYSCALL_DEFINE4(semtimedop
, int, semid
, struct sembuf __user
*, tsops
,
1059 unsigned, nsops
, const struct timespec __user
*, timeout
)
1061 int error
= -EINVAL
;
1062 struct sem_array
*sma
;
1063 struct sembuf fast_sops
[SEMOPM_FAST
];
1064 struct sembuf
* sops
= fast_sops
, *sop
;
1065 struct sem_undo
*un
;
1066 int undos
= 0, alter
= 0, max
;
1067 struct sem_queue queue
;
1068 unsigned long jiffies_left
= 0;
1069 struct ipc_namespace
*ns
;
1071 ns
= current
->nsproxy
->ipc_ns
;
1073 if (nsops
< 1 || semid
< 0)
1075 if (nsops
> ns
->sc_semopm
)
1077 if(nsops
> SEMOPM_FAST
) {
1078 sops
= kmalloc(sizeof(*sops
)*nsops
,GFP_KERNEL
);
1082 if (copy_from_user (sops
, tsops
, nsops
* sizeof(*tsops
))) {
1087 struct timespec _timeout
;
1088 if (copy_from_user(&_timeout
, timeout
, sizeof(*timeout
))) {
1092 if (_timeout
.tv_sec
< 0 || _timeout
.tv_nsec
< 0 ||
1093 _timeout
.tv_nsec
>= 1000000000L) {
1097 jiffies_left
= timespec_to_jiffies(&_timeout
);
1100 for (sop
= sops
; sop
< sops
+ nsops
; sop
++) {
1101 if (sop
->sem_num
>= max
)
1103 if (sop
->sem_flg
& SEM_UNDO
)
1105 if (sop
->sem_op
!= 0)
1110 un
= find_alloc_undo(ns
, semid
);
1112 error
= PTR_ERR(un
);
1118 sma
= sem_lock_check(ns
, semid
);
1122 error
= PTR_ERR(sma
);
1127 * semid identifiers are not unique - find_alloc_undo may have
1128 * allocated an undo structure, it was invalidated by an RMID
1129 * and now a new array with received the same id. Check and fail.
1130 * This case can be detected checking un->semid. The existance of
1131 * "un" itself is guaranteed by rcu.
1135 if (un
->semid
== -1) {
1137 goto out_unlock_free
;
1140 * rcu lock can be released, "un" cannot disappear:
1141 * - sem_lock is acquired, thus IPC_RMID is
1143 * - exit_sem is impossible, it always operates on
1144 * current (or a dead task).
1152 if (max
>= sma
->sem_nsems
)
1153 goto out_unlock_free
;
1156 if (ipcperms(&sma
->sem_perm
, alter
? S_IWUGO
: S_IRUGO
))
1157 goto out_unlock_free
;
1159 error
= security_sem_semop(sma
, sops
, nsops
, alter
);
1161 goto out_unlock_free
;
1163 error
= try_atomic_semop (sma
, sops
, nsops
, un
, task_tgid_vnr(current
));
1165 if (alter
&& error
== 0)
1167 goto out_unlock_free
;
1170 /* We need to sleep on this operation, so we put the current
1171 * task into the pending queue and go to sleep.
1175 queue
.nsops
= nsops
;
1177 queue
.pid
= task_tgid_vnr(current
);
1178 queue
.alter
= alter
;
1180 list_add_tail(&queue
.list
, &sma
->sem_pending
);
1182 list_add(&queue
.list
, &sma
->sem_pending
);
1184 queue
.status
= -EINTR
;
1185 queue
.sleeper
= current
;
1186 current
->state
= TASK_INTERRUPTIBLE
;
1190 jiffies_left
= schedule_timeout(jiffies_left
);
1194 error
= queue
.status
;
1195 while(unlikely(error
== IN_WAKEUP
)) {
1197 error
= queue
.status
;
1200 if (error
!= -EINTR
) {
1201 /* fast path: update_queue already obtained all requested
1206 sma
= sem_lock(ns
, semid
);
1213 * If queue.status != -EINTR we are woken up by another process
1215 error
= queue
.status
;
1216 if (error
!= -EINTR
) {
1217 goto out_unlock_free
;
1221 * If an interrupt occurred we have to clean up the queue
1223 if (timeout
&& jiffies_left
== 0)
1225 list_del(&queue
.list
);
1230 if(sops
!= fast_sops
)
1235 SYSCALL_DEFINE3(semop
, int, semid
, struct sembuf __user
*, tsops
,
1238 return sys_semtimedop(semid
, tsops
, nsops
, NULL
);
1241 /* If CLONE_SYSVSEM is set, establish sharing of SEM_UNDO state between
1242 * parent and child tasks.
1245 int copy_semundo(unsigned long clone_flags
, struct task_struct
*tsk
)
1247 struct sem_undo_list
*undo_list
;
1250 if (clone_flags
& CLONE_SYSVSEM
) {
1251 error
= get_undo_list(&undo_list
);
1254 atomic_inc(&undo_list
->refcnt
);
1255 tsk
->sysvsem
.undo_list
= undo_list
;
1257 tsk
->sysvsem
.undo_list
= NULL
;
1263 * add semadj values to semaphores, free undo structures.
1264 * undo structures are not freed when semaphore arrays are destroyed
1265 * so some of them may be out of date.
1266 * IMPLEMENTATION NOTE: There is some confusion over whether the
1267 * set of adjustments that needs to be done should be done in an atomic
1268 * manner or not. That is, if we are attempting to decrement the semval
1269 * should we queue up and wait until we can do so legally?
1270 * The original implementation attempted to do this (queue and wait).
1271 * The current implementation does not do so. The POSIX standard
1272 * and SVID should be consulted to determine what behavior is mandated.
1274 void exit_sem(struct task_struct
*tsk
)
1276 struct sem_undo_list
*ulp
;
1278 ulp
= tsk
->sysvsem
.undo_list
;
1281 tsk
->sysvsem
.undo_list
= NULL
;
1283 if (!atomic_dec_and_test(&ulp
->refcnt
))
1287 struct sem_array
*sma
;
1288 struct sem_undo
*un
;
1293 un
= list_entry(rcu_dereference(ulp
->list_proc
.next
),
1294 struct sem_undo
, list_proc
);
1295 if (&un
->list_proc
== &ulp
->list_proc
)
1304 sma
= sem_lock_check(tsk
->nsproxy
->ipc_ns
, un
->semid
);
1306 /* exit_sem raced with IPC_RMID, nothing to do */
1310 un
= lookup_undo(ulp
, semid
);
1312 /* exit_sem raced with IPC_RMID+semget() that created
1313 * exactly the same semid. Nothing to do.
1319 /* remove un from the linked lists */
1320 assert_spin_locked(&sma
->sem_perm
.lock
);
1321 list_del(&un
->list_id
);
1323 spin_lock(&ulp
->lock
);
1324 list_del_rcu(&un
->list_proc
);
1325 spin_unlock(&ulp
->lock
);
1327 /* perform adjustments registered in un */
1328 for (i
= 0; i
< sma
->sem_nsems
; i
++) {
1329 struct sem
* semaphore
= &sma
->sem_base
[i
];
1330 if (un
->semadj
[i
]) {
1331 semaphore
->semval
+= un
->semadj
[i
];
1333 * Range checks of the new semaphore value,
1334 * not defined by sus:
1335 * - Some unices ignore the undo entirely
1336 * (e.g. HP UX 11i 11.22, Tru64 V5.1)
1337 * - some cap the value (e.g. FreeBSD caps
1338 * at 0, but doesn't enforce SEMVMX)
1340 * Linux caps the semaphore value, both at 0
1343 * Manfred <manfred@colorfullife.com>
1345 if (semaphore
->semval
< 0)
1346 semaphore
->semval
= 0;
1347 if (semaphore
->semval
> SEMVMX
)
1348 semaphore
->semval
= SEMVMX
;
1349 semaphore
->sempid
= task_tgid_vnr(current
);
1352 sma
->sem_otime
= get_seconds();
1353 /* maybe some queued-up processes were waiting for this */
1357 call_rcu(&un
->rcu
, free_un
);
1362 #ifdef CONFIG_PROC_FS
1363 static int sysvipc_sem_proc_show(struct seq_file
*s
, void *it
)
1365 struct sem_array
*sma
= it
;
1367 return seq_printf(s
,
1368 "%10d %10d %4o %10lu %5u %5u %5u %5u %10lu %10lu\n",
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