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: releng/10.2/sys/kern/kern_syscalls.c 214181 2010-10-21 20:31:50Z delphij $");
29
30 #include <sys/param.h>
31 #include <sys/kernel.h>
32 #include <sys/lock.h>
33 #include <sys/module.h>
34 #include <sys/sx.h>
35 #include <sys/syscall.h>
36 #include <sys/sysent.h>
37 #include <sys/sysproto.h>
38 #include <sys/systm.h>
39 #include <machine/atomic.h>
40
41 /*
42 * Acts like "nosys" but can be identified in sysent for dynamic call
43 * number assignment for a limited number of calls.
44 *
45 * Place holder for system call slots reserved for loadable modules.
46 */
47 int
48 lkmnosys(struct thread *td, struct nosys_args *args)
49 {
50
51 return (nosys(td, args));
52 }
53
54 int
55 lkmressys(struct thread *td, struct nosys_args *args)
56 {
57
58 return (nosys(td, args));
59 }
60
61 static void
62 syscall_thread_drain(struct sysent *se)
63 {
64 u_int32_t cnt, oldcnt;
65
66 do {
67 oldcnt = se->sy_thrcnt;
68 KASSERT((oldcnt & SY_THR_STATIC) == 0,
69 ("drain on static syscall"));
70 cnt = oldcnt | SY_THR_DRAINING;
71 } while (atomic_cmpset_acq_32(&se->sy_thrcnt, oldcnt, cnt) == 0);
72 while (atomic_cmpset_32(&se->sy_thrcnt, SY_THR_DRAINING,
73 SY_THR_ABSENT) == 0)
74 pause("scdrn", hz/2);
75 }
76
77 int
78 syscall_thread_enter(struct thread *td, struct sysent *se)
79 {
80 u_int32_t cnt, oldcnt;
81
82 do {
83 oldcnt = se->sy_thrcnt;
84 if ((oldcnt & SY_THR_STATIC) != 0)
85 return (0);
86 if ((oldcnt & (SY_THR_DRAINING | SY_THR_ABSENT)) != 0)
87 return (ENOSYS);
88 cnt = oldcnt + SY_THR_INCR;
89 } while (atomic_cmpset_acq_32(&se->sy_thrcnt, oldcnt, cnt) == 0);
90 return (0);
91 }
92
93 void
94 syscall_thread_exit(struct thread *td, struct sysent *se)
95 {
96 u_int32_t cnt, oldcnt;
97
98 do {
99 oldcnt = se->sy_thrcnt;
100 if ((oldcnt & SY_THR_STATIC) != 0)
101 return;
102 cnt = oldcnt - SY_THR_INCR;
103 } while (atomic_cmpset_rel_32(&se->sy_thrcnt, oldcnt, cnt) == 0);
104 }
105
106 int
107 syscall_register(int *offset, struct sysent *new_sysent,
108 struct sysent *old_sysent)
109 {
110 int i;
111
112 if (*offset == NO_SYSCALL) {
113 for (i = 1; i < SYS_MAXSYSCALL; ++i)
114 if (sysent[i].sy_call == (sy_call_t *)lkmnosys)
115 break;
116 if (i == SYS_MAXSYSCALL)
117 return (ENFILE);
118 *offset = i;
119 } else if (*offset < 0 || *offset >= SYS_MAXSYSCALL)
120 return (EINVAL);
121 else if (sysent[*offset].sy_call != (sy_call_t *)lkmnosys &&
122 sysent[*offset].sy_call != (sy_call_t *)lkmressys)
123 return (EEXIST);
124
125 KASSERT(sysent[*offset].sy_thrcnt == SY_THR_ABSENT,
126 ("dynamic syscall is not protected"));
127 *old_sysent = sysent[*offset];
128 new_sysent->sy_thrcnt = SY_THR_ABSENT;
129 sysent[*offset] = *new_sysent;
130 atomic_store_rel_32(&sysent[*offset].sy_thrcnt, 0);
131 return (0);
132 }
133
134 int
135 syscall_deregister(int *offset, struct sysent *old_sysent)
136 {
137
138 if (*offset) {
139 syscall_thread_drain(&sysent[*offset]);
140 sysent[*offset] = *old_sysent;
141 }
142 return (0);
143 }
144
145 int
146 syscall_module_handler(struct module *mod, int what, void *arg)
147 {
148 struct syscall_module_data *data = arg;
149 modspecific_t ms;
150 int error;
151
152 switch (what) {
153 case MOD_LOAD:
154 error = syscall_register(data->offset, data->new_sysent,
155 &data->old_sysent);
156 if (error) {
157 /* Leave a mark so we know to safely unload below. */
158 data->offset = NULL;
159 return (error);
160 }
161 ms.intval = *data->offset;
162 MOD_XLOCK;
163 module_setspecific(mod, &ms);
164 MOD_XUNLOCK;
165 if (data->chainevh)
166 error = data->chainevh(mod, what, data->chainarg);
167 return (error);
168 case MOD_UNLOAD:
169 /*
170 * MOD_LOAD failed, so just return without calling the
171 * chained handler since we didn't pass along the MOD_LOAD
172 * event.
173 */
174 if (data->offset == NULL)
175 return (0);
176 if (data->chainevh) {
177 error = data->chainevh(mod, what, data->chainarg);
178 if (error)
179 return error;
180 }
181 error = syscall_deregister(data->offset, &data->old_sysent);
182 return (error);
183 default:
184 if (data->chainevh)
185 return (data->chainevh(mod, what, data->chainarg));
186 return (EOPNOTSUPP);
187 }
188
189 /* NOTREACHED */
190 }
191
192 int
193 syscall_helper_register(struct syscall_helper_data *sd)
194 {
195 struct syscall_helper_data *sd1;
196 int error;
197
198 for (sd1 = sd; sd1->syscall_no != NO_SYSCALL; sd1++) {
199 error = syscall_register(&sd1->syscall_no, &sd1->new_sysent,
200 &sd1->old_sysent);
201 if (error != 0) {
202 syscall_helper_unregister(sd);
203 return (error);
204 }
205 sd1->registered = 1;
206 }
207 return (0);
208 }
209
210 int
211 syscall_helper_unregister(struct syscall_helper_data *sd)
212 {
213 struct syscall_helper_data *sd1;
214
215 for (sd1 = sd; sd1->registered != 0; sd1++) {
216 syscall_deregister(&sd1->syscall_no, &sd1->old_sysent);
217 sd1->registered = 0;
218 }
219 return (0);
220 }
Cache object: 8295e9e88e5a358298d9667535faa2bb
|