Merge master.kernel.org:/home/rmk/linux-2.6-serial
[linux-2.6/linux-acpi-2.6/ibm-acpi-2.6.git] / ipc / util.c
blobe00c35f7b2b8055ffc9d516b69343eb6c3158836
1 /*
2 * linux/ipc/util.c
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>
16 #include <linux/mm.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>
30 #include "util.h"
32 /**
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)
41 sem_init();
42 msg_init();
43 shm_init();
44 return 0;
46 __initcall(ipc_init);
48 /**
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
55 * array itself.
58 void __init ipc_init_ids(struct ipc_ids* ids, int size)
60 int i;
61 sema_init(&ids->sem,1);
63 if(size > IPCMNI)
64 size = IPCMNI;
65 ids->in_use = 0;
66 ids->max_id = -1;
67 ids->seq = 0;
69 int seq_limit = INT_MAX/SEQ_MULTIPLIER;
70 if(seq_limit > USHRT_MAX)
71 ids->seq_max = USHRT_MAX;
72 else
73 ids->seq_max = seq_limit;
76 ids->entries = ipc_rcu_alloc(sizeof(struct kern_ipc_perm *)*size +
77 sizeof(struct ipc_id_ary));
79 if(ids->entries == NULL) {
80 printk(KERN_ERR "ipc_init_ids() failed, ipc service disabled.\n");
81 size = 0;
82 ids->entries = &ids->nullentry;
84 ids->entries->size = size;
85 for(i=0;i<size;i++)
86 ids->entries->p[i] = NULL;
89 /**
90 * ipc_findkey - find a key in an ipc identifier set
91 * @ids: Identifier set
92 * @key: The key to find
94 * Requires ipc_ids.sem locked.
95 * Returns the identifier if found or -1 if not.
98 int ipc_findkey(struct ipc_ids* ids, key_t key)
100 int id;
101 struct kern_ipc_perm* p;
102 int max_id = ids->max_id;
105 * rcu_dereference() is not needed here
106 * since ipc_ids.sem is held
108 for (id = 0; id <= max_id; id++) {
109 p = ids->entries->p[id];
110 if(p==NULL)
111 continue;
112 if (key == p->key)
113 return id;
115 return -1;
119 * Requires ipc_ids.sem locked
121 static int grow_ary(struct ipc_ids* ids, int newsize)
123 struct ipc_id_ary* new;
124 struct ipc_id_ary* old;
125 int i;
126 int size = ids->entries->size;
128 if(newsize > IPCMNI)
129 newsize = IPCMNI;
130 if(newsize <= size)
131 return newsize;
133 new = ipc_rcu_alloc(sizeof(struct kern_ipc_perm *)*newsize +
134 sizeof(struct ipc_id_ary));
135 if(new == NULL)
136 return size;
137 new->size = newsize;
138 memcpy(new->p, ids->entries->p, sizeof(struct kern_ipc_perm *)*size +
139 sizeof(struct ipc_id_ary));
140 for(i=size;i<newsize;i++) {
141 new->p[i] = NULL;
143 old = ids->entries;
146 * Use rcu_assign_pointer() to make sure the memcpyed contents
147 * of the new array are visible before the new array becomes visible.
149 rcu_assign_pointer(ids->entries, new);
151 ipc_rcu_putref(old);
152 return newsize;
156 * ipc_addid - add an IPC identifier
157 * @ids: IPC identifier set
158 * @new: new IPC permission set
159 * @size: new size limit for the id array
161 * Add an entry 'new' to the IPC arrays. The permissions object is
162 * initialised and the first free entry is set up and the id assigned
163 * is returned. The list is returned in a locked state on success.
164 * On failure the list is not locked and -1 is returned.
166 * Called with ipc_ids.sem held.
169 int ipc_addid(struct ipc_ids* ids, struct kern_ipc_perm* new, int size)
171 int id;
173 size = grow_ary(ids,size);
176 * rcu_dereference()() is not needed here since
177 * ipc_ids.sem is held
179 for (id = 0; id < size; id++) {
180 if(ids->entries->p[id] == NULL)
181 goto found;
183 return -1;
184 found:
185 ids->in_use++;
186 if (id > ids->max_id)
187 ids->max_id = id;
189 new->cuid = new->uid = current->euid;
190 new->gid = new->cgid = current->egid;
192 new->seq = ids->seq++;
193 if(ids->seq > ids->seq_max)
194 ids->seq = 0;
196 spin_lock_init(&new->lock);
197 new->deleted = 0;
198 rcu_read_lock();
199 spin_lock(&new->lock);
200 ids->entries->p[id] = new;
201 return id;
205 * ipc_rmid - remove an IPC identifier
206 * @ids: identifier set
207 * @id: Identifier to remove
209 * The identifier must be valid, and in use. The kernel will panic if
210 * fed an invalid identifier. The entry is removed and internal
211 * variables recomputed. The object associated with the identifier
212 * is returned.
213 * ipc_ids.sem and the spinlock for this ID is hold before this function
214 * is called, and remain locked on the exit.
217 struct kern_ipc_perm* ipc_rmid(struct ipc_ids* ids, int id)
219 struct kern_ipc_perm* p;
220 int lid = id % SEQ_MULTIPLIER;
221 if(lid >= ids->entries->size)
222 BUG();
225 * do not need a rcu_dereference()() here to force ordering
226 * on Alpha, since the ipc_ids.sem is held.
228 p = ids->entries->p[lid];
229 ids->entries->p[lid] = NULL;
230 if(p==NULL)
231 BUG();
232 ids->in_use--;
234 if (lid == ids->max_id) {
235 do {
236 lid--;
237 if(lid == -1)
238 break;
239 } while (ids->entries->p[lid] == NULL);
240 ids->max_id = lid;
242 p->deleted = 1;
243 return p;
247 * ipc_alloc - allocate ipc space
248 * @size: size desired
250 * Allocate memory from the appropriate pools and return a pointer to it.
251 * NULL is returned if the allocation fails
254 void* ipc_alloc(int size)
256 void* out;
257 if(size > PAGE_SIZE)
258 out = vmalloc(size);
259 else
260 out = kmalloc(size, GFP_KERNEL);
261 return out;
265 * ipc_free - free ipc space
266 * @ptr: pointer returned by ipc_alloc
267 * @size: size of block
269 * Free a block created with ipc_alloc. The caller must know the size
270 * used in the allocation call.
273 void ipc_free(void* ptr, int size)
275 if(size > PAGE_SIZE)
276 vfree(ptr);
277 else
278 kfree(ptr);
282 * rcu allocations:
283 * There are three headers that are prepended to the actual allocation:
284 * - during use: ipc_rcu_hdr.
285 * - during the rcu grace period: ipc_rcu_grace.
286 * - [only if vmalloc]: ipc_rcu_sched.
287 * Their lifetime doesn't overlap, thus the headers share the same memory.
288 * Unlike a normal union, they are right-aligned, thus some container_of
289 * forward/backward casting is necessary:
291 struct ipc_rcu_hdr
293 int refcount;
294 int is_vmalloc;
295 void *data[0];
299 struct ipc_rcu_grace
301 struct rcu_head rcu;
302 /* "void *" makes sure alignment of following data is sane. */
303 void *data[0];
306 struct ipc_rcu_sched
308 struct work_struct work;
309 /* "void *" makes sure alignment of following data is sane. */
310 void *data[0];
313 #define HDRLEN_KMALLOC (sizeof(struct ipc_rcu_grace) > sizeof(struct ipc_rcu_hdr) ? \
314 sizeof(struct ipc_rcu_grace) : sizeof(struct ipc_rcu_hdr))
315 #define HDRLEN_VMALLOC (sizeof(struct ipc_rcu_sched) > HDRLEN_KMALLOC ? \
316 sizeof(struct ipc_rcu_sched) : HDRLEN_KMALLOC)
318 static inline int rcu_use_vmalloc(int size)
320 /* Too big for a single page? */
321 if (HDRLEN_KMALLOC + size > PAGE_SIZE)
322 return 1;
323 return 0;
327 * ipc_rcu_alloc - allocate ipc and rcu space
328 * @size: size desired
330 * Allocate memory for the rcu header structure + the object.
331 * Returns the pointer to the object.
332 * NULL is returned if the allocation fails.
335 void* ipc_rcu_alloc(int size)
337 void* out;
339 * We prepend the allocation with the rcu struct, and
340 * workqueue if necessary (for vmalloc).
342 if (rcu_use_vmalloc(size)) {
343 out = vmalloc(HDRLEN_VMALLOC + size);
344 if (out) {
345 out += HDRLEN_VMALLOC;
346 container_of(out, struct ipc_rcu_hdr, data)->is_vmalloc = 1;
347 container_of(out, struct ipc_rcu_hdr, data)->refcount = 1;
349 } else {
350 out = kmalloc(HDRLEN_KMALLOC + size, GFP_KERNEL);
351 if (out) {
352 out += HDRLEN_KMALLOC;
353 container_of(out, struct ipc_rcu_hdr, data)->is_vmalloc = 0;
354 container_of(out, struct ipc_rcu_hdr, data)->refcount = 1;
358 return out;
361 void ipc_rcu_getref(void *ptr)
363 container_of(ptr, struct ipc_rcu_hdr, data)->refcount++;
367 * ipc_schedule_free - free ipc + rcu space
369 * Since RCU callback function is called in bh,
370 * we need to defer the vfree to schedule_work
372 static void ipc_schedule_free(struct rcu_head *head)
374 struct ipc_rcu_grace *grace =
375 container_of(head, struct ipc_rcu_grace, rcu);
376 struct ipc_rcu_sched *sched =
377 container_of(&(grace->data[0]), struct ipc_rcu_sched, data[0]);
379 INIT_WORK(&sched->work, vfree, sched);
380 schedule_work(&sched->work);
384 * ipc_immediate_free - free ipc + rcu space
386 * Free from the RCU callback context
389 static void ipc_immediate_free(struct rcu_head *head)
391 struct ipc_rcu_grace *free =
392 container_of(head, struct ipc_rcu_grace, rcu);
393 kfree(free);
396 void ipc_rcu_putref(void *ptr)
398 if (--container_of(ptr, struct ipc_rcu_hdr, data)->refcount > 0)
399 return;
401 if (container_of(ptr, struct ipc_rcu_hdr, data)->is_vmalloc) {
402 call_rcu(&container_of(ptr, struct ipc_rcu_grace, data)->rcu,
403 ipc_schedule_free);
404 } else {
405 call_rcu(&container_of(ptr, struct ipc_rcu_grace, data)->rcu,
406 ipc_immediate_free);
411 * ipcperms - check IPC permissions
412 * @ipcp: IPC permission set
413 * @flag: desired permission set.
415 * Check user, group, other permissions for access
416 * to ipc resources. return 0 if allowed
419 int ipcperms (struct kern_ipc_perm *ipcp, short flag)
420 { /* flag will most probably be 0 or S_...UGO from <linux/stat.h> */
421 int requested_mode, granted_mode;
423 requested_mode = (flag >> 6) | (flag >> 3) | flag;
424 granted_mode = ipcp->mode;
425 if (current->euid == ipcp->cuid || current->euid == ipcp->uid)
426 granted_mode >>= 6;
427 else if (in_group_p(ipcp->cgid) || in_group_p(ipcp->gid))
428 granted_mode >>= 3;
429 /* is there some bit set in requested_mode but not in granted_mode? */
430 if ((requested_mode & ~granted_mode & 0007) &&
431 !capable(CAP_IPC_OWNER))
432 return -1;
434 return security_ipc_permission(ipcp, flag);
438 * Functions to convert between the kern_ipc_perm structure and the
439 * old/new ipc_perm structures
443 * kernel_to_ipc64_perm - convert kernel ipc permissions to user
444 * @in: kernel permissions
445 * @out: new style IPC permissions
447 * Turn the kernel object 'in' into a set of permissions descriptions
448 * for returning to userspace (out).
452 void kernel_to_ipc64_perm (struct kern_ipc_perm *in, struct ipc64_perm *out)
454 out->key = in->key;
455 out->uid = in->uid;
456 out->gid = in->gid;
457 out->cuid = in->cuid;
458 out->cgid = in->cgid;
459 out->mode = in->mode;
460 out->seq = in->seq;
464 * ipc64_perm_to_ipc_perm - convert old ipc permissions to new
465 * @in: new style IPC permissions
466 * @out: old style IPC permissions
468 * Turn the new style permissions object in into a compatibility
469 * object and store it into the 'out' pointer.
472 void ipc64_perm_to_ipc_perm (struct ipc64_perm *in, struct ipc_perm *out)
474 out->key = in->key;
475 SET_UID(out->uid, in->uid);
476 SET_GID(out->gid, in->gid);
477 SET_UID(out->cuid, in->cuid);
478 SET_GID(out->cgid, in->cgid);
479 out->mode = in->mode;
480 out->seq = in->seq;
484 * So far only shm_get_stat() calls ipc_get() via shm_get(), so ipc_get()
485 * is called with shm_ids.sem locked. Since grow_ary() is also called with
486 * shm_ids.sem down(for Shared Memory), there is no need to add read
487 * barriers here to gurantee the writes in grow_ary() are seen in order
488 * here (for Alpha).
490 * However ipc_get() itself does not necessary require ipc_ids.sem down. So
491 * if in the future ipc_get() is used by other places without ipc_ids.sem
492 * down, then ipc_get() needs read memery barriers as ipc_lock() does.
494 struct kern_ipc_perm* ipc_get(struct ipc_ids* ids, int id)
496 struct kern_ipc_perm* out;
497 int lid = id % SEQ_MULTIPLIER;
498 if(lid >= ids->entries->size)
499 return NULL;
500 out = ids->entries->p[lid];
501 return out;
504 struct kern_ipc_perm* ipc_lock(struct ipc_ids* ids, int id)
506 struct kern_ipc_perm* out;
507 int lid = id % SEQ_MULTIPLIER;
508 struct ipc_id_ary* entries;
510 rcu_read_lock();
511 entries = rcu_dereference(ids->entries);
512 if(lid >= entries->size) {
513 rcu_read_unlock();
514 return NULL;
516 out = entries->p[lid];
517 if(out == NULL) {
518 rcu_read_unlock();
519 return NULL;
521 spin_lock(&out->lock);
523 /* ipc_rmid() may have already freed the ID while ipc_lock
524 * was spinning: here verify that the structure is still valid
526 if (out->deleted) {
527 spin_unlock(&out->lock);
528 rcu_read_unlock();
529 return NULL;
531 return out;
534 void ipc_lock_by_ptr(struct kern_ipc_perm *perm)
536 rcu_read_lock();
537 spin_lock(&perm->lock);
540 void ipc_unlock(struct kern_ipc_perm* perm)
542 spin_unlock(&perm->lock);
543 rcu_read_unlock();
546 int ipc_buildid(struct ipc_ids* ids, int id, int seq)
548 return SEQ_MULTIPLIER*seq + id;
551 int ipc_checkid(struct ipc_ids* ids, struct kern_ipc_perm* ipcp, int uid)
553 if(uid/SEQ_MULTIPLIER != ipcp->seq)
554 return 1;
555 return 0;
558 #ifdef __ARCH_WANT_IPC_PARSE_VERSION
562 * ipc_parse_version - IPC call version
563 * @cmd: pointer to command
565 * Return IPC_64 for new style IPC and IPC_OLD for old style IPC.
566 * The cmd value is turned from an encoding command and version into
567 * just the command code.
570 int ipc_parse_version (int *cmd)
572 if (*cmd & IPC_64) {
573 *cmd ^= IPC_64;
574 return IPC_64;
575 } else {
576 return IPC_OLD;
580 #endif /* __ARCH_WANT_IPC_PARSE_VERSION */