server/semaphore.c

   1 /*
   2  * Server-side semaphore management
   3  *
   4  * Copyright (C) 1998 Alexandre Julliard
   5  *
   6  * This library is free software; you can redistribute it and/or
   7  * modify it under the terms of the GNU Lesser General Public
   8  * License as published by the Free Software Foundation; either
   9  * version 2.1 of the License, or (at your option) any later version.
  10  *
  11  * This library is distributed in the hope that it will be useful,
  12  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  13  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  14  * Lesser General Public License for more details.
  15  *
  16  * You should have received a copy of the GNU Lesser General Public
  17  * License along with this library; if not, write to the Free Software
  18  * Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301, USA
  19  */
  20
  21 #include "config.h"
  22
  23 #include <assert.h>
  24 #include <stdio.h>
  25 #include <stdlib.h>
  26 #include <stdarg.h>
  27 #include <sys/types.h>
  28
  29 #include "ntstatus.h"
  30 #define WIN32_NO_STATUS
  31 #include "windef.h"
  32 #include "winternl.h"
  33
  34 #include "handle.h"
  35 #include "thread.h"
  36 #include "request.h"
  37 #include "security.h"
  38
  39 static const WCHAR semaphore_name[] = {'S','e','m','a','p','h','o','r','e'};
  40
  41 struct type_descr semaphore_type =
  42 {
  43     { semaphore_name, sizeof(semaphore_name) },   /* name */
  44     SEMAPHORE_ALL_ACCESS,                         /* valid_access */
  45     {                                             /* mapping */
  46         STANDARD_RIGHTS_READ | SEMAPHORE_QUERY_STATE,
  47         STANDARD_RIGHTS_WRITE | SEMAPHORE_MODIFY_STATE,
  48         STANDARD_RIGHTS_EXECUTE | SYNCHRONIZE,
  49         SEMAPHORE_ALL_ACCESS
  50     },
  51 };
  52
  53 struct semaphore
  54 {
  55     struct object  obj;    /* object header */
  56     unsigned int   count;  /* current count */
  57     unsigned int   max;    /* maximum possible count */
  58 };
  59
  60 static void semaphore_dump( struct object *obj, int verbose );
  61 static int semaphore_signaled( struct object *obj, struct wait_queue_entry *entry );
  62 static void semaphore_satisfied( struct object *obj, struct wait_queue_entry *entry );
  63 static int semaphore_signal( struct object *obj, unsigned int access );
  64
  65 static const struct object_ops semaphore_ops =
  66 {
  67     sizeof(struct semaphore),      /* size */
  68     &semaphore_type,               /* type */
  69     semaphore_dump,                /* dump */
  70     add_queue,                     /* add_queue */
  71     remove_queue,                  /* remove_queue */
  72     semaphore_signaled,            /* signaled */
  73     semaphore_satisfied,           /* satisfied */
  74     semaphore_signal,              /* signal */
  75     no_get_fd,                     /* get_fd */
  76     default_map_access,            /* map_access */
  77     default_get_sd,                /* get_sd */
  78     default_set_sd,                /* set_sd */
  79     default_get_full_name,         /* get_full_name */
  80     no_lookup_name,                /* lookup_name */
  81     directory_link_name,           /* link_name */
  82     default_unlink_name,           /* unlink_name */
  83     no_open_file,                  /* open_file */
  84     no_kernel_obj_list,            /* get_kernel_obj_list */
  85     no_close_handle,               /* close_handle */
  86     no_destroy                     /* destroy */
  87 };
  88
  89
  90 static struct semaphore *create_semaphore( struct object *root, const struct unicode_str *name,
  91                                            unsigned int attr, unsigned int initial, unsigned int max,
  92                                            const struct security_descriptor *sd )
  93 {
  94     struct semaphore *sem;
  95
  96     if (!max || (initial > max))
  97     {
  98         set_error( STATUS_INVALID_PARAMETER );
  99         return NULL;
 100     }
 101     if ((sem = create_named_object( root, &semaphore_ops, name, attr, sd )))
 102     {
 103         if (get_error() != STATUS_OBJECT_NAME_EXISTS)
 104         {
 105             /* initialize it if it didn't already exist */
 106             sem->count = initial;
 107             sem->max   = max;
 108         }
 109     }
 110     return sem;
 111 }
 112
 113 static int release_semaphore( struct semaphore *sem, unsigned int count,
 114                               unsigned int *prev )
 115 {
 116     if (prev) *prev = sem->count;
 117     if (sem->count + count < sem->count || sem->count + count > sem->max)
 118     {
 119         set_error( STATUS_SEMAPHORE_LIMIT_EXCEEDED );
 120         return 0;
 121     }
 122     else if (sem->count)
 123     {
 124         /* there cannot be any thread to wake up if the count is != 0 */
 125         sem->count += count;
 126     }
 127     else
 128     {
 129         sem->count = count;
 130         wake_up( &sem->obj, count );
 131     }
 132     return 1;
 133 }
 134
 135 static void semaphore_dump( struct object *obj, int verbose )
 136 {
 137     struct semaphore *sem = (struct semaphore *)obj;
 138     assert( obj->ops == &semaphore_ops );
 139     fprintf( stderr, "Semaphore count=%d max=%d\n", sem->count, sem->max );
 140 }
 141
 142 static int semaphore_signaled( struct object *obj, struct wait_queue_entry *entry )
 143 {
 144     struct semaphore *sem = (struct semaphore *)obj;
 145     assert( obj->ops == &semaphore_ops );
 146     return (sem->count > 0);
 147 }
 148
 149 static void semaphore_satisfied( struct object *obj, struct wait_queue_entry *entry )
 150 {
 151     struct semaphore *sem = (struct semaphore *)obj;
 152     assert( obj->ops == &semaphore_ops );
 153     assert( sem->count );
 154     sem->count--;
 155 }
 156
 157 static int semaphore_signal( struct object *obj, unsigned int access )
 158 {
 159     struct semaphore *sem = (struct semaphore *)obj;
 160     assert( obj->ops == &semaphore_ops );
 161
 162     if (!(access & SEMAPHORE_MODIFY_STATE))
 163     {
 164         set_error( STATUS_ACCESS_DENIED );
 165         return 0;
 166     }
 167     return release_semaphore( sem, 1, NULL );
 168 }
 169
 170 /* create a semaphore */
 171 DECL_HANDLER(create_semaphore)
 172 {
 173     struct semaphore *sem;
 174     struct unicode_str name;
 175     struct object *root;
 176     const struct security_descriptor *sd;
 177     const struct object_attributes *objattr = get_req_object_attributes( &sd, &name, &root );
 178
 179     if (!objattr) return;
 180
 181     if ((sem = create_semaphore( root, &name, objattr->attributes, req->initial, req->max, sd )))
 182     {
 183         if (get_error() == STATUS_OBJECT_NAME_EXISTS)
 184             reply->handle = alloc_handle( current->process, sem, req->access, objattr->attributes );
 185         else
 186             reply->handle = alloc_handle_no_access_check( current->process, sem,
 187                                                           req->access, objattr->attributes );
 188         release_object( sem );
 189     }
 190
 191     if (root) release_object( root );
 192 }
 193
 194 /* open a handle to a semaphore */
 195 DECL_HANDLER(open_semaphore)
 196 {
 197     struct unicode_str name = get_req_unicode_str();
 198
 199     reply->handle = open_object( current->process, req->rootdir, req->access,
 200                                  &semaphore_ops, &name, req->attributes );
 201 }
 202
 203 /* release a semaphore */
 204 DECL_HANDLER(release_semaphore)
 205 {
 206     struct semaphore *sem;
 207
 208     if ((sem = (struct semaphore *)get_handle_obj( current->process, req->handle,
 209                                                    SEMAPHORE_MODIFY_STATE, &semaphore_ops )))
 210     {
 211         release_semaphore( sem, req->count, &reply->prev_count );
 212         release_object( sem );
 213     }
 214 }
 215
 216 /* query details about the semaphore */
 217 DECL_HANDLER(query_semaphore)
 218 {
 219     struct semaphore *sem;
 220
 221     if ((sem = (struct semaphore *)get_handle_obj( current->process, req->handle,
 222                                                    SEMAPHORE_QUERY_STATE, &semaphore_ops )))
 223     {
 224         reply->current = sem->count;
 225         reply->max = sem->max;
 226         release_object( sem );
 227     }
 228 }