kern_syscalls.c revision 160882 
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: head/sys/kern/kern_syscalls.c 160882 2006-08-01 16:32:20Z jhb $");
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 */
45int
46lkmnosys(struct thread *td, struct nosys_args *args)
47{
48	return(nosys(td, args));
49}
50
51int
52lkmressys(struct thread *td, struct nosys_args *args)
53{
54	return(nosys(td, args));
55}
56
57int
58syscall_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
81int
82syscall_deregister(int *offset, struct sysent *old_sysent)
83{
84       if (*offset)
85               sysent[*offset] = *old_sysent;
86       return 0;
87}
88
89int
90syscall_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}
138