2 * SPDX-License-Identifier: BSD-2-Clause-FreeBSD
4 * Copyright (c) 1999 Assar Westerlund
7 * Redistribution and use in source and binary forms, with or without
8 * modification, are permitted provided that the following conditions
10 * 1. Redistributions of source code must retain the above copyright
11 * notice, this list of conditions and the following disclaimer.
12 * 2. Redistributions in binary form must reproduce the above copyright
13 * notice, this list of conditions and the following disclaimer in the
14 * documentation and/or other materials provided with the distribution.
16 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
17 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
18 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
19 * ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
20 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
21 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
22 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
23 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
24 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
25 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
29 #include <sys/cdefs.h>
30 __FBSDID("$FreeBSD$");
32 #include <sys/param.h>
33 #include <sys/kernel.h>
35 #include <sys/module.h>
36 #include <sys/mutex.h>
38 #include <sys/resourcevar.h>
40 #include <sys/syscall.h>
41 #include <sys/sysent.h>
42 #include <sys/sysproto.h>
43 #include <sys/systm.h>
44 #include <machine/atomic.h>
47 * Acts like "nosys" but can be identified in sysent for dynamic call
48 * number assignment for a limited number of calls.
50 * Place holder for system call slots reserved for loadable modules.
53 lkmnosys(struct thread *td, struct nosys_args *args)
56 return (nosys(td, args));
60 lkmressys(struct thread *td, struct nosys_args *args)
63 return (nosys(td, args));
67 syscall_thread_drain(struct sysent *se)
69 u_int32_t cnt, oldcnt;
72 oldcnt = se->sy_thrcnt;
73 KASSERT((oldcnt & SY_THR_STATIC) == 0,
74 ("drain on static syscall"));
75 cnt = oldcnt | SY_THR_DRAINING;
76 } while (atomic_cmpset_acq_32(&se->sy_thrcnt, oldcnt, cnt) == 0);
77 while (atomic_cmpset_32(&se->sy_thrcnt, SY_THR_DRAINING,
83 syscall_thread_enter(struct thread *td, struct sysent *se)
85 u_int32_t cnt, oldcnt;
88 oldcnt = se->sy_thrcnt;
89 if ((oldcnt & SY_THR_STATIC) != 0)
91 if ((oldcnt & (SY_THR_DRAINING | SY_THR_ABSENT)) != 0)
93 cnt = oldcnt + SY_THR_INCR;
94 } while (atomic_cmpset_acq_32(&se->sy_thrcnt, oldcnt, cnt) == 0);
99 syscall_thread_exit(struct thread *td, struct sysent *se)
101 u_int32_t cnt, oldcnt;
104 oldcnt = se->sy_thrcnt;
105 if ((oldcnt & SY_THR_STATIC) != 0)
107 cnt = oldcnt - SY_THR_INCR;
108 } while (atomic_cmpset_rel_32(&se->sy_thrcnt, oldcnt, cnt) == 0);
112 syscall_register(int *offset, struct sysent *new_sysent,
113 struct sysent *old_sysent, int flags)
117 if ((flags & ~SY_THR_STATIC) != 0)
120 if (*offset == NO_SYSCALL) {
121 for (i = 1; i < SYS_MAXSYSCALL; ++i)
122 if (sysent[i].sy_call == (sy_call_t *)lkmnosys)
124 if (i == SYS_MAXSYSCALL)
127 } else if (*offset < 0 || *offset >= SYS_MAXSYSCALL)
129 else if (sysent[*offset].sy_call != (sy_call_t *)lkmnosys &&
130 sysent[*offset].sy_call != (sy_call_t *)lkmressys)
133 KASSERT(sysent[*offset].sy_thrcnt == SY_THR_ABSENT,
134 ("dynamic syscall is not protected"));
135 *old_sysent = sysent[*offset];
136 new_sysent->sy_thrcnt = SY_THR_ABSENT;
137 sysent[*offset] = *new_sysent;
138 atomic_store_rel_32(&sysent[*offset].sy_thrcnt, flags);
143 syscall_deregister(int *offset, struct sysent *old_sysent)
148 return (0); /* XXX? */
150 se = &sysent[*offset];
151 if ((se->sy_thrcnt & SY_THR_STATIC) != 0)
153 syscall_thread_drain(se);
154 sysent[*offset] = *old_sysent;
159 syscall_module_handler(struct module *mod, int what, void *arg)
161 struct syscall_module_data *data = arg;
167 error = syscall_register(data->offset, data->new_sysent,
168 &data->old_sysent, data->flags);
170 /* Leave a mark so we know to safely unload below. */
174 ms.intval = *data->offset;
176 module_setspecific(mod, &ms);
179 error = data->chainevh(mod, what, data->chainarg);
183 * MOD_LOAD failed, so just return without calling the
184 * chained handler since we didn't pass along the MOD_LOAD
187 if (data->offset == NULL)
189 if (data->chainevh) {
190 error = data->chainevh(mod, what, data->chainarg);
194 error = syscall_deregister(data->offset, &data->old_sysent);
198 return (data->chainevh(mod, what, data->chainarg));
206 syscall_helper_register(struct syscall_helper_data *sd, int flags)
208 struct syscall_helper_data *sd1;
211 for (sd1 = sd; sd1->syscall_no != NO_SYSCALL; sd1++) {
212 error = syscall_register(&sd1->syscall_no, &sd1->new_sysent,
213 &sd1->old_sysent, flags);
215 syscall_helper_unregister(sd);
224 syscall_helper_unregister(struct syscall_helper_data *sd)
226 struct syscall_helper_data *sd1;
228 for (sd1 = sd; sd1->registered != 0; sd1++) {
229 syscall_deregister(&sd1->syscall_no, &sd1->old_sysent);