kern_syscalls.c revision 83366 
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 83366 2001-09-12 08:38:13Z julian $
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/module.h>
34
35/*
36 * Acts like "nosys" but can be identified in sysent for dynamic call
37 * number assignment for a limited number of calls.
38 *
39 * Place holder for system call slots reserved for loadable modules.
40 */
41int
42lkmnosys(struct thread *td, struct nosys_args *args)
43{
44	return(nosys(td, args));
45}
46
47int
48lkmressys(struct thread *td, struct nosys_args *args)
49{
50	return(nosys(td, args));
51}
52
53int
54syscall_register(int *offset, struct sysent *new_sysent,
55		 struct sysent *old_sysent)
56{
57       if (*offset == NO_SYSCALL) {
58               int i;
59
60               for (i = 1; i < SYS_MAXSYSCALL; ++i)
61                       if (sysent[i].sy_call == (sy_call_t *)lkmnosys)
62                               break;
63               if (i == SYS_MAXSYSCALL)
64                       return ENFILE;
65               *offset = i;
66       } else if (*offset < 0 || *offset >= SYS_MAXSYSCALL)
67               return EINVAL;
68       else if (sysent[*offset].sy_call != (sy_call_t *)lkmnosys &&
69				sysent[*offset].sy_call != (sy_call_t *)lkmressys)
70               return EEXIST;
71
72       *old_sysent = sysent[*offset];
73       sysent[*offset] = *new_sysent;
74       return 0;
75}
76
77int
78syscall_deregister(int *offset, struct sysent *old_sysent)
79{
80       if (*offset)
81               sysent[*offset] = *old_sysent;
82       return 0;
83}
84
85int
86syscall_module_handler(struct module *mod, int what, void *arg)
87{
88       struct syscall_module_data *data = (struct syscall_module_data*)arg;
89       modspecific_t ms;
90       int error;
91
92       switch (what) {
93       case MOD_LOAD :
94               error = syscall_register(data->offset, data->new_sysent,
95                                        &data->old_sysent);
96               if (error)
97                       return error;
98	       ms.intval = *data->offset;
99	       module_setspecific(mod, &ms);
100               if (data->chainevh)
101                       error = data->chainevh(mod, what, data->chainarg);
102               return error;
103
104       case MOD_UNLOAD :
105               if (data->chainevh) {
106                       error = data->chainevh(mod, what, data->chainarg);
107                       if (error)
108                               return error;
109               }
110               error = syscall_deregister(data->offset, &data->old_sysent);
111               return error;
112       }
113
114       if (data->chainevh)
115               return data->chainevh(mod, what, data->chainarg);
116       else
117               return 0;
118}
119