sys/kern/kern_syscalls.c

   1 /*-
   2  * Copyright (c) 1999 Assar Westerlund
   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  *
  14  * THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
  15  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
  16  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
  17  * ARE DISCLAIMED.  IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
  18  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
  19  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
  20  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
  21  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
  22  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
  23  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
  24  * SUCH DAMAGE.
  25  */
  26
  27 #include <sys/cdefs.h>
  28 __FBSDID("$FreeBSD$");
  29
  30 #include <sys/param.h>
  31 #include <sys/sysproto.h>
  32 #include <sys/sysent.h>
  33 #include <sys/syscall.h>
  34 #include <sys/lock.h>
  35 #include <sys/mutex.h>
  36 #include <sys/sx.h>
  37 #include <sys/module.h>
  38
  39 /*
  40  * Acts like "nosys" but can be identified in sysent for dynamic call
  41  * number assignment for a limited number of calls.
  42  *
  43  * Place holder for system call slots reserved for loadable modules.
  44  */
  45 int
  46 lkmnosys(struct thread *td, struct nosys_args *args)
  47 {
  48         return(nosys(td, args));
  49 }
  50
  51 int
  52 lkmressys(struct thread *td, struct nosys_args *args)
  53 {
  54         return(nosys(td, args));
  55 }
  56
  57 int
  58 syscall_register(int *offset, struct sysent *new_sysent,
  59                  struct sysent *old_sysent)
  60 {
  61        if (*offset == NO_SYSCALL) {
  62                int i;
  63
  64                for (i = 1; i < SYS_MAXSYSCALL; ++i)
  65                        if (sysent[i].sy_call == (sy_call_t *)lkmnosys)
  66                                break;
  67                if (i == SYS_MAXSYSCALL)
  68                        return ENFILE;
  69                *offset = i;
  70        } else if (*offset < 0 || *offset >= SYS_MAXSYSCALL)
  71                return EINVAL;
  72        else if (sysent[*offset].sy_call != (sy_call_t *)lkmnosys &&
  73                                 sysent[*offset].sy_call != (sy_call_t *)lkmressys)
  74                return EEXIST;
  75
  76        *old_sysent = sysent[*offset];
  77        sysent[*offset] = *new_sysent;
  78        return 0;
  79 }
  80
  81 int
  82 syscall_deregister(int *offset, struct sysent *old_sysent)
  83 {
  84        if (*offset)
  85                sysent[*offset] = *old_sysent;
  86        return 0;
  87 }
  88
  89 int
  90 syscall_module_handler(struct module *mod, int what, void *arg)
  91 {
  92        struct syscall_module_data *data = (struct syscall_module_data*)arg;
  93        modspecific_t ms;
  94        int error;
  95
  96        switch (what) {
  97        case MOD_LOAD :
  98                error = syscall_register(data->offset, data->new_sysent,
  99                                         &data->old_sysent);
 100                if (error) {
 101                        /* Leave a mark so we know to safely unload below. */
 102                        data->offset = NULL;
 103                        return error;
 104                }
 105                ms.intval = *data->offset;
 106                MOD_XLOCK;
 107                module_setspecific(mod, &ms);
 108                MOD_XUNLOCK;
 109                if (data->chainevh)
 110                        error = data->chainevh(mod, what, data->chainarg);
 111                return error;
 112
 113        case MOD_UNLOAD :
 114                /*
 115                 * MOD_LOAD failed, so just return without calling the
 116                 * chained handler since we didn't pass along the MOD_LOAD
 117                 * event.
 118                 */
 119                if (data->offset == NULL)
 120                        return (0);
 121                if (data->chainevh) {
 122                        error = data->chainevh(mod, what, data->chainarg);
 123                        if (error)
 124                                return error;
 125                }
 126                error = syscall_deregister(data->offset, &data->old_sysent);
 127                return error;
 128        default :
 129                return EOPNOTSUPP;
 130
 131        }
 132
 133        if (data->chainevh)
 134                return data->chainevh(mod, what, data->chainarg);
 135        else
 136                return 0;
 137 }