3 * Copyright (C) 1992 Krishna Balasubramanian
5 * Sep 1997 - Call suser() last after "normal" permission checks so we
6 * get BSD style process accounting right.
7 * Occurs in several places in the IPC code.
8 * Chris Evans, <chris@ferret.lmh.ox.ac.uk>
9 * Nov 1999 - ipc helper functions, unified SMP locking
10 * Manfred Spraul <manfreds@colorfullife.com>
11 * Oct 2002 - One lock per IPC id. RCU ipc_free for lock-free grow_ary().
12 * Mingming Cao <cmm@us.ibm.com>
15 #include <linux/config.h>
17 #include <linux/shm.h>
18 #include <linux/init.h>
19 #include <linux/msg.h>
20 #include <linux/smp_lock.h>
21 #include <linux/vmalloc.h>
22 #include <linux/slab.h>
23 #include <linux/highuid.h>
24 #include <linux/security.h>
25 #include <linux/rcupdate.h>
26 #include <linux/workqueue.h>
28 #include <asm/unistd.h>
33 * ipc_init - initialise IPC subsystem
35 * The various system5 IPC resources (semaphores, messages and shared
36 * memory are initialised
39 static int __init
ipc_init(void)
49 * ipc_init_ids - initialise IPC identifiers
50 * @ids: Identifier set
51 * @size: Number of identifiers
53 * Given a size for the ipc identifier range (limited below IPCMNI)
54 * set up the sequence range to use then allocate and initialise the
58 void __init
ipc_init_ids(struct ipc_ids
* ids
, int size
)
61 sema_init(&ids
->sem
,1);
70 int seq_limit
= INT_MAX
/SEQ_MULTIPLIER
;
71 if(seq_limit
> USHRT_MAX
)
72 ids
->seq_max
= USHRT_MAX
;
74 ids
->seq_max
= seq_limit
;
77 ids
->entries
= ipc_rcu_alloc(sizeof(struct ipc_id
)*size
);
79 if(ids
->entries
== NULL
) {
80 printk(KERN_ERR
"ipc_init_ids() failed, ipc service disabled.\n");
83 for(i
=0;i
<ids
->size
;i
++)
84 ids
->entries
[i
].p
= NULL
;
88 * ipc_findkey - find a key in an ipc identifier set
89 * @ids: Identifier set
90 * @key: The key to find
92 * Requires ipc_ids.sem locked.
93 * Returns the identifier if found or -1 if not.
96 int ipc_findkey(struct ipc_ids
* ids
, key_t key
)
99 struct kern_ipc_perm
* p
;
100 int max_id
= ids
->max_id
;
103 * read_barrier_depends is not needed here
104 * since ipc_ids.sem is held
106 for (id
= 0; id
<= max_id
; id
++) {
107 p
= ids
->entries
[id
].p
;
117 * Requires ipc_ids.sem locked
119 static int grow_ary(struct ipc_ids
* ids
, int newsize
)
127 if(newsize
<= ids
->size
)
130 new = ipc_rcu_alloc(sizeof(struct ipc_id
)*newsize
);
133 memcpy(new, ids
->entries
, sizeof(struct ipc_id
)*ids
->size
);
134 for(i
=ids
->size
;i
<newsize
;i
++) {
141 * before setting the ids->entries to the new array, there must be a
142 * smp_wmb() to make sure the memcpyed contents of the new array are
143 * visible before the new array becomes visible.
145 smp_wmb(); /* prevent seeing new array uninitialized. */
147 smp_wmb(); /* prevent indexing into old array based on new size. */
150 ipc_rcu_free(old
, sizeof(struct ipc_id
)*i
);
155 * ipc_addid - add an IPC identifier
156 * @ids: IPC identifier set
157 * @new: new IPC permission set
158 * @size: new size limit for the id array
160 * Add an entry 'new' to the IPC arrays. The permissions object is
161 * initialised and the first free entry is set up and the id assigned
162 * is returned. The list is returned in a locked state on success.
163 * On failure the list is not locked and -1 is returned.
165 * Called with ipc_ids.sem held.
168 int ipc_addid(struct ipc_ids
* ids
, struct kern_ipc_perm
* new, int size
)
172 size
= grow_ary(ids
,size
);
175 * read_barrier_depends() is not needed here since
176 * ipc_ids.sem is held
178 for (id
= 0; id
< size
; id
++) {
179 if(ids
->entries
[id
].p
== NULL
)
185 if (id
> ids
->max_id
)
188 new->cuid
= new->uid
= current
->euid
;
189 new->gid
= new->cgid
= current
->egid
;
191 new->seq
= ids
->seq
++;
192 if(ids
->seq
> ids
->seq_max
)
195 new->lock
= SPIN_LOCK_UNLOCKED
;
198 spin_lock(&new->lock
);
199 ids
->entries
[id
].p
= new;
204 * ipc_rmid - remove an IPC identifier
205 * @ids: identifier set
206 * @id: Identifier to remove
208 * The identifier must be valid, and in use. The kernel will panic if
209 * fed an invalid identifier. The entry is removed and internal
210 * variables recomputed. The object associated with the identifier
212 * ipc_ids.sem and the spinlock for this ID is hold before this function
213 * is called, and remain locked on the exit.
216 struct kern_ipc_perm
* ipc_rmid(struct ipc_ids
* ids
, int id
)
218 struct kern_ipc_perm
* p
;
219 int lid
= id
% SEQ_MULTIPLIER
;
224 * do not need a read_barrier_depends() here to force ordering
225 * on Alpha, since the ipc_ids.sem is held.
227 p
= ids
->entries
[lid
].p
;
228 ids
->entries
[lid
].p
= NULL
;
233 if (lid
== ids
->max_id
) {
238 } while (ids
->entries
[lid
].p
== NULL
);
246 * ipc_alloc - allocate ipc space
247 * @size: size desired
249 * Allocate memory from the appropriate pools and return a pointer to it.
250 * NULL is returned if the allocation fails
253 void* ipc_alloc(int size
)
259 out
= kmalloc(size
, GFP_KERNEL
);
264 * ipc_free - free ipc space
265 * @ptr: pointer returned by ipc_alloc
266 * @size: size of block
268 * Free a block created with ipc_alloc. The caller must know the size
269 * used in the allocation call.
272 void ipc_free(void* ptr
, int size
)
280 struct ipc_rcu_kmalloc
283 /* "void *" makes sure alignment of following data is sane. */
287 struct ipc_rcu_vmalloc
290 struct work_struct work
;
291 /* "void *" makes sure alignment of following data is sane. */
295 static inline int rcu_use_vmalloc(int size
)
297 /* Too big for a single page? */
298 if (sizeof(struct ipc_rcu_kmalloc
) + size
> PAGE_SIZE
)
304 * ipc_rcu_alloc - allocate ipc and rcu space
305 * @size: size desired
307 * Allocate memory for the rcu header structure + the object.
308 * Returns the pointer to the object.
309 * NULL is returned if the allocation fails.
312 void* ipc_rcu_alloc(int size
)
316 * We prepend the allocation with the rcu struct, and
317 * workqueue if necessary (for vmalloc).
319 if (rcu_use_vmalloc(size
)) {
320 out
= vmalloc(sizeof(struct ipc_rcu_vmalloc
) + size
);
321 if (out
) out
+= sizeof(struct ipc_rcu_vmalloc
);
323 out
= kmalloc(sizeof(struct ipc_rcu_kmalloc
)+size
, GFP_KERNEL
);
324 if (out
) out
+= sizeof(struct ipc_rcu_kmalloc
);
331 * ipc_schedule_free - free ipc + rcu space
333 * Since RCU callback function is called in bh,
334 * we need to defer the vfree to schedule_work
336 static void ipc_schedule_free(void* arg
)
338 struct ipc_rcu_vmalloc
*free
= arg
;
340 INIT_WORK(&free
->work
, vfree
, free
);
341 schedule_work(&free
->work
);
344 void ipc_rcu_free(void* ptr
, int size
)
346 if (rcu_use_vmalloc(size
)) {
347 struct ipc_rcu_vmalloc
*free
;
348 free
= ptr
- sizeof(*free
);
349 call_rcu(&free
->rcu
, ipc_schedule_free
, free
);
351 struct ipc_rcu_kmalloc
*free
;
352 free
= ptr
- sizeof(*free
);
353 /* kfree takes a "const void *" so gcc warns. So we cast. */
354 call_rcu(&free
->rcu
, (void (*)(void *))kfree
, free
);
360 * ipcperms - check IPC permissions
361 * @ipcp: IPC permission set
362 * @flag: desired permission set.
364 * Check user, group, other permissions for access
365 * to ipc resources. return 0 if allowed
368 int ipcperms (struct kern_ipc_perm
*ipcp
, short flag
)
369 { /* flag will most probably be 0 or S_...UGO from <linux/stat.h> */
370 int requested_mode
, granted_mode
;
372 requested_mode
= (flag
>> 6) | (flag
>> 3) | flag
;
373 granted_mode
= ipcp
->mode
;
374 if (current
->euid
== ipcp
->cuid
|| current
->euid
== ipcp
->uid
)
376 else if (in_group_p(ipcp
->cgid
) || in_group_p(ipcp
->gid
))
378 /* is there some bit set in requested_mode but not in granted_mode? */
379 if ((requested_mode
& ~granted_mode
& 0007) &&
380 !capable(CAP_IPC_OWNER
))
383 return security_ipc_permission(ipcp
, flag
);
387 * Functions to convert between the kern_ipc_perm structure and the
388 * old/new ipc_perm structures
392 * kernel_to_ipc64_perm - convert kernel ipc permissions to user
393 * @in: kernel permissions
394 * @out: new style IPC permissions
396 * Turn the kernel object 'in' into a set of permissions descriptions
397 * for returning to userspace (out).
401 void kernel_to_ipc64_perm (struct kern_ipc_perm
*in
, struct ipc64_perm
*out
)
406 out
->cuid
= in
->cuid
;
407 out
->cgid
= in
->cgid
;
408 out
->mode
= in
->mode
;
413 * ipc64_perm_to_ipc_perm - convert old ipc permissions to new
414 * @in: new style IPC permissions
415 * @out: old style IPC permissions
417 * Turn the new style permissions object in into a compatibility
418 * object and store it into the 'out' pointer.
421 void ipc64_perm_to_ipc_perm (struct ipc64_perm
*in
, struct ipc_perm
*out
)
424 SET_UID(out
->uid
, in
->uid
);
425 SET_GID(out
->gid
, in
->gid
);
426 SET_UID(out
->cuid
, in
->cuid
);
427 SET_GID(out
->cgid
, in
->cgid
);
428 out
->mode
= in
->mode
;
433 * So far only shm_get_stat() calls ipc_get() via shm_get(), so ipc_get()
434 * is called with shm_ids.sem locked. Since grow_ary() is also called with
435 * shm_ids.sem down(for Shared Memory), there is no need to add read
436 * barriers here to gurantee the writes in grow_ary() are seen in order
439 * However ipc_get() itself does not necessary require ipc_ids.sem down. So
440 * if in the future ipc_get() is used by other places without ipc_ids.sem
441 * down, then ipc_get() needs read memery barriers as ipc_lock() does.
443 struct kern_ipc_perm
* ipc_get(struct ipc_ids
* ids
, int id
)
445 struct kern_ipc_perm
* out
;
446 int lid
= id
% SEQ_MULTIPLIER
;
449 out
= ids
->entries
[lid
].p
;
453 struct kern_ipc_perm
* ipc_lock(struct ipc_ids
* ids
, int id
)
455 struct kern_ipc_perm
* out
;
456 int lid
= id
% SEQ_MULTIPLIER
;
457 struct ipc_id
* entries
;
460 if(lid
>= ids
->size
) {
466 * Note: The following two read barriers are corresponding
467 * to the two write barriers in grow_ary(). They guarantee
468 * the writes are seen in the same order on the read side.
469 * smp_rmb() has effect on all CPUs. read_barrier_depends()
470 * is used if there are data dependency between two reads, and
471 * has effect only on Alpha.
473 smp_rmb(); /* prevent indexing old array with new size */
474 entries
= ids
->entries
;
475 read_barrier_depends(); /*prevent seeing new array unitialized */
476 out
= entries
[lid
].p
;
481 spin_lock(&out
->lock
);
483 /* ipc_rmid() may have already freed the ID while ipc_lock
484 * was spinning: here verify that the structure is still valid
487 spin_unlock(&out
->lock
);
494 void ipc_unlock(struct kern_ipc_perm
* perm
)
496 spin_unlock(&perm
->lock
);
500 int ipc_buildid(struct ipc_ids
* ids
, int id
, int seq
)
502 return SEQ_MULTIPLIER
*seq
+ id
;
505 int ipc_checkid(struct ipc_ids
* ids
, struct kern_ipc_perm
* ipcp
, int uid
)
507 if(uid
/SEQ_MULTIPLIER
!= ipcp
->seq
)
512 #ifdef __ARCH_WANT_IPC_PARSE_VERSION
516 * ipc_parse_version - IPC call version
517 * @cmd: pointer to command
519 * Return IPC_64 for new style IPC and IPC_OLD for old style IPC.
520 * The cmd value is turned from an encoding command and version into
521 * just the command code.
524 int ipc_parse_version (int *cmd
)
534 #endif /* __ARCH_WANT_IPC_PARSE_VERSION */