Annotation of prex/sys/ipc/object.c, Revision 1.1
1.1 ! nbrk 1: /*-
! 2: * Copyright (c) 2005-2007, Kohsuke Ohtani
! 3: * All rights reserved.
! 4: *
! 5: * Redistribution and use in source and binary forms, with or without
! 6: * modification, are permitted provided that the following conditions
! 7: * are met:
! 8: * 1. Redistributions of source code must retain the above copyright
! 9: * notice, this list of conditions and the following disclaimer.
! 10: * 2. Redistributions in binary form must reproduce the above copyright
! 11: * notice, this list of conditions and the following disclaimer in the
! 12: * documentation and/or other materials provided with the distribution.
! 13: * 3. Neither the name of the author nor the names of any co-contributors
! 14: * may be used to endorse or promote products derived from this software
! 15: * without specific prior written permission.
! 16: *
! 17: * THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
! 18: * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
! 19: * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
! 20: * ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
! 21: * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
! 22: * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
! 23: * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
! 24: * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
! 25: * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
! 26: * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
! 27: * SUCH DAMAGE.
! 28: */
! 29:
! 30: /*
! 31: * object.c - object service
! 32: */
! 33:
! 34: /*
! 35: * General Design:
! 36: *
! 37: * An object represents service, state, or policies etc. To
! 38: * manipulate objects, kernel provide 3 functions: create, delete,
! 39: * lookup. Prex task will create an object to provide its interface
! 40: * to other tasks. The tasks will communicate by sending a message
! 41: * to the object each other. For example, a server task creates some
! 42: * objects and client task will send a request message to it.
! 43: *
! 44: * A substance of object is stored in kernel space, and it is
! 45: * protected from user mode code. Each object data is managed with
! 46: * the hash table by using its name string. Usually, an object has
! 47: * a unique name within a system. Before a task sends a message to
! 48: * the specific object, it must obtain the object ID by looking up
! 49: * the name of the target object.
! 50: *
! 51: * An object can be created without its name. These object can be
! 52: * used as private objects that are used by threads in same task.
! 53: */
! 54:
! 55: #include <kernel.h>
! 56: #include <queue.h>
! 57: #include <kmem.h>
! 58: #include <sched.h>
! 59: #include <task.h>
! 60: #include <ipc.h>
! 61:
! 62: #define OBJ_MAXBUCKETS 32 /* Size of object hash buckets */
! 63:
! 64: /*
! 65: * Object hash table
! 66: *
! 67: * All objects are hashed by its name string. If an object
! 68: * has no name, it is linked to index zero. The scheduler
! 69: * must be locked when this table is touched.
! 70: */
! 71: static struct list obj_table[OBJ_MAXBUCKETS];
! 72:
! 73: /*
! 74: * Calculate the hash index for specified name string.
! 75: * The name can be NULL if the object does not have its
! 76: * name.
! 77: */
! 78: static u_int
! 79: object_hash(const char *name)
! 80: {
! 81: u_int h = 0;
! 82:
! 83: if (name == NULL)
! 84: return 0;
! 85: while (*name)
! 86: h = ((h << 5) + h) + *name++;
! 87: return h & (OBJ_MAXBUCKETS - 1);
! 88: }
! 89:
! 90: /*
! 91: * Helper function to find the object from the specified name.
! 92: * Returns NULL if not found.
! 93: */
! 94: static object_t
! 95: object_find(const char *name)
! 96: {
! 97: list_t head, n;
! 98: object_t obj = NULL;
! 99:
! 100: head = &obj_table[object_hash(name)];
! 101:
! 102: for (n = list_first(head); n != head; n = list_next(n)) {
! 103: obj = list_entry(n, struct object, hash_link);
! 104: if (!strncmp(obj->name, name, MAXOBJNAME))
! 105: break;
! 106: }
! 107: if (n == head)
! 108: return NULL;
! 109: return obj;
! 110: }
! 111:
! 112: /*
! 113: * Search an object in the object name space. The object
! 114: * name must be null-terminated string. The object ID is
! 115: * returned in obj on success.
! 116: */
! 117: int
! 118: object_lookup(const char *name, object_t *objp)
! 119: {
! 120: object_t obj;
! 121: size_t len;
! 122: char str[MAXOBJNAME];
! 123:
! 124: if (umem_strnlen(name, MAXOBJNAME, &len))
! 125: return EFAULT;
! 126: if (len == 0 || len >= MAXOBJNAME)
! 127: return ESRCH;
! 128: if (umem_copyin(name, str, len + 1))
! 129: return EFAULT;
! 130:
! 131: sched_lock();
! 132: obj = object_find(str);
! 133: sched_unlock();
! 134:
! 135: if (obj == NULL)
! 136: return ENOENT;
! 137: if (umem_copyout(&obj, objp, sizeof(object_t)))
! 138: return EFAULT;
! 139: return 0;
! 140: }
! 141:
! 142: /*
! 143: * Create a new object.
! 144: *
! 145: * The ID of the new object is stored in pobj on success.
! 146: * The name of the object must be unique in the system.
! 147: * Or, the object can be created without name by setting
! 148: * NULL as name argument. This object can be used as a
! 149: * private object which can be accessed only by threads in
! 150: * same task.
! 151: */
! 152: int
! 153: object_create(const char *name, object_t *objp)
! 154: {
! 155: object_t obj = 0;
! 156: char str[MAXOBJNAME];
! 157: task_t self;
! 158: size_t len = 0;
! 159:
! 160: if (name != NULL) {
! 161: if (umem_strnlen(name, MAXOBJNAME, &len))
! 162: return EFAULT;
! 163: if (len >= MAXOBJNAME)
! 164: return ENAMETOOLONG;
! 165: if (umem_copyin(name, str, len + 1))
! 166: return EFAULT;
! 167: }
! 168: str[len] = '\0';
! 169: sched_lock();
! 170:
! 171: /*
! 172: * Check user buffer first. This can reduce the error
! 173: * recovery for the subsequence resource allocations.
! 174: */
! 175: if (umem_copyout(&obj, objp, sizeof(object_t))) {
! 176: sched_unlock();
! 177: return EFAULT;
! 178: }
! 179: if (object_find(str) != NULL) {
! 180: sched_unlock();
! 181: return EEXIST;
! 182: }
! 183: if ((obj = kmem_alloc(sizeof(struct object))) == NULL) {
! 184: sched_unlock();
! 185: return ENOMEM;
! 186: }
! 187: if (name != NULL)
! 188: strlcpy(obj->name, str, len + 1);
! 189:
! 190: self = cur_task();
! 191: obj->owner = self;
! 192: obj->magic = OBJECT_MAGIC;
! 193: queue_init(&obj->sendq);
! 194: queue_init(&obj->recvq);
! 195: list_insert(&obj_table[object_hash(name)], &obj->hash_link);
! 196: list_insert(&self->objects, &obj->task_link);
! 197:
! 198: umem_copyout(&obj, objp, sizeof(object_t));
! 199: sched_unlock();
! 200: return 0;
! 201: }
! 202:
! 203: /*
! 204: * Destroy an object.
! 205: *
! 206: * A thread can delete the object only when the target
! 207: * object is created by the thread of the same task. All
! 208: * pending messages related to the deleted object are
! 209: * automatically canceled.
! 210: */
! 211: int
! 212: object_destroy(object_t obj)
! 213: {
! 214: int err = 0;
! 215:
! 216: sched_lock();
! 217: if (!object_valid(obj)) {
! 218: err = EINVAL;
! 219: } else if (obj->owner != cur_task()) {
! 220: err = EACCES;
! 221: } else {
! 222: obj->magic = 0;
! 223: msg_cancel(obj);
! 224: list_remove(&obj->task_link);
! 225: list_remove(&obj->hash_link);
! 226: kmem_free(obj);
! 227: }
! 228: sched_unlock();
! 229: return err;
! 230: }
! 231:
! 232: void
! 233: object_init(void)
! 234: {
! 235: int i;
! 236:
! 237: for (i = 0; i < OBJ_MAXBUCKETS; i++)
! 238: list_init(&obj_table[i]);
! 239: }
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