2 * Copyright (c) 1999 Assar Westerlund
5 * Redistribution and use in source and binary forms, with or without
6 * modification, are permitted provided that the following conditions
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.
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
27 #include <sys/cdefs.h>
28 __FBSDID("$FreeBSD$");
30 #include <sys/param.h>
31 #include <sys/kernel.h>
33 #include <sys/module.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>
42 * Acts like "nosys" but can be identified in sysent for dynamic call
43 * number assignment for a limited number of calls.
45 * Place holder for system call slots reserved for loadable modules.
48 lkmnosys(struct thread *td, struct nosys_args *args)
51 return (nosys(td, args));
55 lkmressys(struct thread *td, struct nosys_args *args)
58 return (nosys(td, args));
62 syscall_thread_drain(struct sysent *se)
64 u_int32_t cnt, oldcnt;
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,
78 syscall_thread_enter(struct thread *td, struct sysent *se)
80 u_int32_t cnt, oldcnt;
83 oldcnt = se->sy_thrcnt;
84 if ((oldcnt & SY_THR_STATIC) != 0)
86 if ((oldcnt & (SY_THR_DRAINING | SY_THR_ABSENT)) != 0)
88 cnt = oldcnt + SY_THR_INCR;
89 } while (atomic_cmpset_acq_32(&se->sy_thrcnt, oldcnt, cnt) == 0);
94 syscall_thread_exit(struct thread *td, struct sysent *se)
96 u_int32_t cnt, oldcnt;
99 oldcnt = se->sy_thrcnt;
100 if ((oldcnt & SY_THR_STATIC) != 0)
102 cnt = oldcnt - SY_THR_INCR;
103 } while (atomic_cmpset_rel_32(&se->sy_thrcnt, oldcnt, cnt) == 0);
107 syscall_register(int *offset, struct sysent *new_sysent,
108 struct sysent *old_sysent)
112 if (*offset == NO_SYSCALL) {
113 for (i = 1; i < SYS_MAXSYSCALL; ++i)
114 if (sysent[i].sy_call == (sy_call_t *)lkmnosys)
116 if (i == SYS_MAXSYSCALL)
119 } else if (*offset < 0 || *offset >= SYS_MAXSYSCALL)
121 else if (sysent[*offset].sy_call != (sy_call_t *)lkmnosys &&
122 sysent[*offset].sy_call != (sy_call_t *)lkmressys)
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);
135 syscall_deregister(int *offset, struct sysent *old_sysent)
139 syscall_thread_drain(&sysent[*offset]);
140 sysent[*offset] = *old_sysent;
146 syscall_module_handler(struct module *mod, int what, void *arg)
148 struct syscall_module_data *data = arg;
154 error = syscall_register(data->offset, data->new_sysent,
157 /* Leave a mark so we know to safely unload below. */
161 ms.intval = *data->offset;
163 module_setspecific(mod, &ms);
166 error = data->chainevh(mod, what, data->chainarg);
170 * MOD_LOAD failed, so just return without calling the
171 * chained handler since we didn't pass along the MOD_LOAD
174 if (data->offset == NULL)
176 if (data->chainevh) {
177 error = data->chainevh(mod, what, data->chainarg);
181 error = syscall_deregister(data->offset, &data->old_sysent);
185 return (data->chainevh(mod, what, data->chainarg));
193 syscall_helper_register(struct syscall_helper_data *sd)
195 struct syscall_helper_data *sd1;
198 for (sd1 = sd; sd1->syscall_no != NO_SYSCALL; sd1++) {
199 error = syscall_register(&sd1->syscall_no, &sd1->new_sysent,
202 syscall_helper_unregister(sd);
211 syscall_helper_unregister(struct syscall_helper_data *sd)
213 struct syscall_helper_data *sd1;
215 for (sd1 = sd; sd1->registered != 0; sd1++) {
216 syscall_deregister(&sd1->syscall_no, &sd1->old_sysent);