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 kern_syscall_register(struct sysent *sysents, int *offset,
113 struct sysent *new_sysent, 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 (sysents[i].sy_call == (sy_call_t *)lkmnosys)
124 if (i == SYS_MAXSYSCALL)
127 } else if (*offset < 0 || *offset >= SYS_MAXSYSCALL)
129 else if (sysents[*offset].sy_call != (sy_call_t *)lkmnosys &&
130 sysents[*offset].sy_call != (sy_call_t *)lkmressys)
133 KASSERT(sysents[*offset].sy_thrcnt == SY_THR_ABSENT,
134 ("dynamic syscall is not protected"));
135 *old_sysent = sysents[*offset];
136 new_sysent->sy_thrcnt = SY_THR_ABSENT;
137 sysents[*offset] = *new_sysent;
138 atomic_store_rel_32(&sysents[*offset].sy_thrcnt, flags);
143 kern_syscall_deregister(struct sysent *sysents, int offset,
144 const struct sysent *old_sysent)
149 return (0); /* XXX? */
151 se = &sysents[offset];
152 if ((se->sy_thrcnt & SY_THR_STATIC) != 0)
154 syscall_thread_drain(se);
155 sysent[offset] = *old_sysent;
160 syscall_module_handler(struct module *mod, int what, void *arg)
163 return (kern_syscall_module_handler(sysent, mod, what, arg));
167 kern_syscall_module_handler(struct sysent *sysents, struct module *mod,
170 struct syscall_module_data *data = arg;
176 error = kern_syscall_register(sysents, data->offset,
177 data->new_sysent, &data->old_sysent, data->flags);
179 /* Leave a mark so we know to safely unload below. */
183 ms.intval = *data->offset;
185 module_setspecific(mod, &ms);
188 error = data->chainevh(mod, what, data->chainarg);
192 * MOD_LOAD failed, so just return without calling the
193 * chained handler since we didn't pass along the MOD_LOAD
196 if (data->offset == NULL)
198 if (data->chainevh) {
199 error = data->chainevh(mod, what, data->chainarg);
203 error = kern_syscall_deregister(sysents, *data->offset,
208 return (data->chainevh(mod, what, data->chainarg));
216 syscall_helper_register(struct syscall_helper_data *sd, int flags)
219 return (kern_syscall_helper_register(sysent, sd, flags));
223 kern_syscall_helper_register(struct sysent *sysents,
224 struct syscall_helper_data *sd, int flags)
226 struct syscall_helper_data *sd1;
229 for (sd1 = sd; sd1->syscall_no != NO_SYSCALL; sd1++) {
230 error = kern_syscall_register(sysents, &sd1->syscall_no,
231 &sd1->new_sysent, &sd1->old_sysent, flags);
233 kern_syscall_helper_unregister(sysents, sd);
242 syscall_helper_unregister(struct syscall_helper_data *sd)
245 return (kern_syscall_helper_unregister(sysent, sd));
249 kern_syscall_helper_unregister(struct sysent *sysents,
250 struct syscall_helper_data *sd)
252 struct syscall_helper_data *sd1;
254 for (sd1 = sd; sd1->registered != 0; sd1++) {
255 kern_syscall_deregister(sysents, sd1->syscall_no,