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  * $FreeBSD: src/sys/kern/kern_syscalls.c,v 1.6 1999/10/11 15:19:10 peter Exp $
  27  * $DragonFly: src/sys/kern/kern_syscalls.c,v 1.4 2006/06/05 07:26:10 dillon Exp $
  28  */
  29
  30 #include <sys/param.h>
  31 #include <sys/types.h>
  32 #include <sys/sysmsg.h>
  33 #include <sys/sysent.h>
  34 #include <sys/syscall.h>
  35 #include <sys/module.h>
  36
  37 /*
  38  * Acts like "nosys" but can be identified in sysent for dynamic call
  39  * number assignment for a limited number of calls.
  40  *
  41  * Place holder for system call slots reserved for loadable modules.
  42  */
  43 int
  44 sys_lkmnosys(struct sysmsg *sysmsg, const struct nosys_args *args)
  45 {
  46         return(sys_nosys(sysmsg, args));
  47 }
  48
  49 int
  50 syscall_register(int *offset, struct sysent *new_sysent,
  51                  struct sysent *old_sysent)
  52 {
  53        if (*offset == NO_SYSCALL) {
  54                int i;
  55
  56                for (i = 1; i < SYS_MAXSYSCALL; ++i)
  57                        if (sysent[i].sy_call == (sy_call_t *)sys_lkmnosys)
  58                                break;
  59                if (i == SYS_MAXSYSCALL)
  60                        return ENFILE;
  61                *offset = i;
  62        } else if (*offset < 0 || *offset >= SYS_MAXSYSCALL)
  63                return EINVAL;
  64        else if (sysent[*offset].sy_call != (sy_call_t *)sys_lkmnosys)
  65                return EEXIST;
  66
  67        *old_sysent = sysent[*offset];
  68        sysent[*offset] = *new_sysent;
  69        return 0;
  70 }
  71
  72 int
  73 syscall_deregister(int *offset, struct sysent *old_sysent)
  74 {
  75        if (*offset)
  76                sysent[*offset] = *old_sysent;
  77        return 0;
  78 }
  79
  80 int
  81 syscall_module_handler(struct module *mod, int what, void *arg)
  82 {
  83        struct syscall_module_data *data = (struct syscall_module_data*)arg;
  84        modspecific_t ms;
  85        int error;
  86
  87        switch (what) {
  88        case MOD_LOAD :
  89                error = syscall_register(data->offset, data->new_sysent,
  90                                         &data->old_sysent);
  91                if (error)
  92                        return error;
  93                ms.intval = *data->offset;
  94                module_setspecific(mod, &ms);
  95                if (data->chainevh)
  96                        error = data->chainevh(mod, what, data->chainarg);
  97                return error;
  98
  99        case MOD_UNLOAD :
 100                if (data->chainevh) {
 101                        error = data->chainevh(mod, what, data->chainarg);
 102                        if (error)
 103                                return error;
 104                }
 105                error = syscall_deregister(data->offset, &data->old_sysent);
 106                return error;
 107        }
 108
 109        if (data->chainevh)
 110                return data->chainevh(mod, what, data->chainarg);
 111        else
 112                return 0;
 113 }