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>
34 #include <sys/mutex.h>
36 #include <sys/resourcevar.h>
38 #include <sys/syscall.h>
39 #include <sys/sysent.h>
40 #include <sys/sysproto.h>
41 #include <sys/systm.h>
42 #include <machine/atomic.h>
45 * Acts like "nosys" but can be identified in sysent for dynamic call
46 * number assignment for a limited number of calls.
48 * Place holder for system call slots reserved for loadable modules.
51 lkmnosys(struct thread *td, struct nosys_args *args)
54 return (nosys(td, args));
58 lkmressys(struct thread *td, struct nosys_args *args)
61 return (nosys(td, args));
65 syscall_thread_drain(struct sysent *se)
67 u_int32_t cnt, oldcnt;
70 oldcnt = se->sy_thrcnt;
71 KASSERT((oldcnt & SY_THR_STATIC) == 0,
72 ("drain on static syscall"));
73 cnt = oldcnt | SY_THR_DRAINING;
74 } while (atomic_cmpset_acq_32(&se->sy_thrcnt, oldcnt, cnt) == 0);
75 while (atomic_cmpset_32(&se->sy_thrcnt, SY_THR_DRAINING,
81 syscall_thread_enter(struct thread *td, struct sysent *se)
83 u_int32_t cnt, oldcnt;
86 oldcnt = se->sy_thrcnt;
87 if ((oldcnt & SY_THR_STATIC) != 0)
89 if ((oldcnt & (SY_THR_DRAINING | SY_THR_ABSENT)) != 0)
91 cnt = oldcnt + SY_THR_INCR;
92 } while (atomic_cmpset_acq_32(&se->sy_thrcnt, oldcnt, cnt) == 0);
97 syscall_thread_exit(struct thread *td, struct sysent *se)
99 u_int32_t cnt, oldcnt;
102 oldcnt = se->sy_thrcnt;
103 if ((oldcnt & SY_THR_STATIC) != 0)
105 cnt = oldcnt - SY_THR_INCR;
106 } while (atomic_cmpset_rel_32(&se->sy_thrcnt, oldcnt, cnt) == 0);
110 syscall_register(int *offset, struct sysent *new_sysent,
111 struct sysent *old_sysent, int flags)
115 if ((flags & ~SY_THR_STATIC) != 0)
118 if (*offset == NO_SYSCALL) {
119 for (i = 1; i < SYS_MAXSYSCALL; ++i)
120 if (sysent[i].sy_call == (sy_call_t *)lkmnosys)
122 if (i == SYS_MAXSYSCALL)
125 } else if (*offset < 0 || *offset >= SYS_MAXSYSCALL)
127 else if (sysent[*offset].sy_call != (sy_call_t *)lkmnosys &&
128 sysent[*offset].sy_call != (sy_call_t *)lkmressys)
131 KASSERT(sysent[*offset].sy_thrcnt == SY_THR_ABSENT,
132 ("dynamic syscall is not protected"));
133 *old_sysent = sysent[*offset];
134 new_sysent->sy_thrcnt = SY_THR_ABSENT;
135 sysent[*offset] = *new_sysent;
136 atomic_store_rel_32(&sysent[*offset].sy_thrcnt, flags);
141 syscall_deregister(int *offset, struct sysent *old_sysent)
146 return (0); /* XXX? */
148 se = &sysent[*offset];
149 if ((se->sy_thrcnt & SY_THR_STATIC) != 0)
151 syscall_thread_drain(se);
152 sysent[*offset] = *old_sysent;
157 syscall_module_handler(struct module *mod, int what, void *arg)
159 struct syscall_module_data *data = arg;
165 error = syscall_register(data->offset, data->new_sysent,
166 &data->old_sysent, data->flags);
168 /* Leave a mark so we know to safely unload below. */
172 ms.intval = *data->offset;
174 module_setspecific(mod, &ms);
177 error = data->chainevh(mod, what, data->chainarg);
181 * MOD_LOAD failed, so just return without calling the
182 * chained handler since we didn't pass along the MOD_LOAD
185 if (data->offset == NULL)
187 if (data->chainevh) {
188 error = data->chainevh(mod, what, data->chainarg);
192 error = syscall_deregister(data->offset, &data->old_sysent);
196 return (data->chainevh(mod, what, data->chainarg));
204 syscall_helper_register(struct syscall_helper_data *sd, int flags)
206 struct syscall_helper_data *sd1;
209 for (sd1 = sd; sd1->syscall_no != NO_SYSCALL; sd1++) {
210 error = syscall_register(&sd1->syscall_no, &sd1->new_sysent,
211 &sd1->old_sysent, flags);
213 syscall_helper_unregister(sd);
222 syscall_helper_unregister(struct syscall_helper_data *sd)
224 struct syscall_helper_data *sd1;
226 for (sd1 = sd; sd1->registered != 0; sd1++) {
227 syscall_deregister(&sd1->syscall_no, &sd1->old_sysent);