Disallow writes to filesystems mounted read-only via NULLFS. In this case
[dragonfly.git] / sys / kern / kern_syscalls.c
CommitLineData
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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 $
753fd850 27 * $DragonFly: src/sys/kern/kern_syscalls.c,v 1.4 2006/06/05 07:26:10 dillon Exp $
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28 */
29
30#include <sys/param.h>
31#include <sys/sysproto.h>
32#include <sys/sysent.h>
33#include <sys/syscall.h>
34#include <sys/module.h>
35
36/*
37 * Acts like "nosys" but can be identified in sysent for dynamic call
38 * number assignment for a limited number of calls.
39 *
40 * Place holder for system call slots reserved for loadable modules.
41 */
42int
753fd850 43sys_lkmnosys(struct nosys_args *args)
984263bc 44{
753fd850 45 return(sys_nosys(args));
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46}
47
48int
49syscall_register(int *offset, struct sysent *new_sysent,
50 struct sysent *old_sysent)
51{
52 if (*offset == NO_SYSCALL) {
53 int i;
54
55 for (i = 1; i < SYS_MAXSYSCALL; ++i)
753fd850 56 if (sysent[i].sy_call == (sy_call_t *)sys_lkmnosys)
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57 break;
58 if (i == SYS_MAXSYSCALL)
59 return ENFILE;
60 *offset = i;
61 } else if (*offset < 0 || *offset >= SYS_MAXSYSCALL)
62 return EINVAL;
753fd850 63 else if (sysent[*offset].sy_call != (sy_call_t *)sys_lkmnosys)
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64 return EEXIST;
65
66 *old_sysent = sysent[*offset];
67 sysent[*offset] = *new_sysent;
68 return 0;
69}
70
71int
72syscall_deregister(int *offset, struct sysent *old_sysent)
73{
74 if (*offset)
75 sysent[*offset] = *old_sysent;
76 return 0;
77}
78
79int
80syscall_module_handler(struct module *mod, int what, void *arg)
81{
82 struct syscall_module_data *data = (struct syscall_module_data*)arg;
83 modspecific_t ms;
84 int error;
85
86 switch (what) {
87 case MOD_LOAD :
88 error = syscall_register(data->offset, data->new_sysent,
89 &data->old_sysent);
90 if (error)
91 return error;
92 ms.intval = *data->offset;
93 module_setspecific(mod, &ms);
94 if (data->chainevh)
95 error = data->chainevh(mod, what, data->chainarg);
96 return error;
97
98 case MOD_UNLOAD :
99 if (data->chainevh) {
100 error = data->chainevh(mod, what, data->chainarg);
101 if (error)
102 return error;
103 }
104 error = syscall_deregister(data->offset, &data->old_sysent);
105 return error;
106 }
107
108 if (data->chainevh)
109 return data->chainevh(mod, what, data->chainarg);
110 else
111 return 0;
112}