kern_syscalls.c revision 92547 
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: head/sys/kern/kern_syscalls.c 92547 2002-03-18 07:45:30Z arr $
27 */
28
29#include <sys/param.h>
30#include <sys/sysproto.h>
31#include <sys/sysent.h>
32#include <sys/syscall.h>
33#include <sys/lock.h>
34#include <sys/mutex.h>
35#include <sys/sx.h>
36#include <sys/module.h>
37
38/*
39 * Acts like "nosys" but can be identified in sysent for dynamic call
40 * number assignment for a limited number of calls.
41 *
42 * Place holder for system call slots reserved for loadable modules.
43 */
44int
45lkmnosys(struct thread *td, struct nosys_args *args)
46{
47	return(nosys(td, args));
48}
49
50int
51lkmressys(struct thread *td, struct nosys_args *args)
52{
53	return(nosys(td, args));
54}
55
56int
57syscall_register(int *offset, struct sysent *new_sysent,
58		 struct sysent *old_sysent)
59{
60       if (*offset == NO_SYSCALL) {
61               int i;
62
63               for (i = 1; i < SYS_MAXSYSCALL; ++i)
64                       if (sysent[i].sy_call == (sy_call_t *)lkmnosys)
65                               break;
66               if (i == SYS_MAXSYSCALL)
67                       return ENFILE;
68               *offset = i;
69       } else if (*offset < 0 || *offset >= SYS_MAXSYSCALL)
70               return EINVAL;
71       else if (sysent[*offset].sy_call != (sy_call_t *)lkmnosys &&
72				sysent[*offset].sy_call != (sy_call_t *)lkmressys)
73               return EEXIST;
74
75       *old_sysent = sysent[*offset];
76       sysent[*offset] = *new_sysent;
77       return 0;
78}
79
80int
81syscall_deregister(int *offset, struct sysent *old_sysent)
82{
83       if (*offset)
84               sysent[*offset] = *old_sysent;
85       return 0;
86}
87
88int
89syscall_module_handler(struct module *mod, int what, void *arg)
90{
91       struct syscall_module_data *data = (struct syscall_module_data*)arg;
92       modspecific_t ms;
93       int error;
94
95       switch (what) {
96       case MOD_LOAD :
97               error = syscall_register(data->offset, data->new_sysent,
98                                        &data->old_sysent);
99               if (error)
100                       return error;
101	       ms.intval = *data->offset;
102	       MOD_XLOCK;
103	       module_setspecific(mod, &ms);
104	       MOD_XUNLOCK;
105               if (data->chainevh)
106                       error = data->chainevh(mod, what, data->chainarg);
107               return error;
108
109       case MOD_UNLOAD :
110               if (data->chainevh) {
111                       error = data->chainevh(mod, what, data->chainarg);
112                       if (error)
113                               return error;
114               }
115               error = syscall_deregister(data->offset, &data->old_sysent);
116               return error;
117       }
118
119       if (data->chainevh)
120               return data->chainevh(mod, what, data->chainarg);
121       else
122               return 0;
123}
124