1 /*- 2 * SPDX-License-Identifier: BSD-2-Clause-FreeBSD 3 * 4 * Copyright (c) 1999 Assar Westerlund 5 * All rights reserved. 6 * 7 * Redistribution and use in source and binary forms, with or without 8 * modification, are permitted provided that the following conditions 9 * are met: 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. 15 * 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 26 * SUCH DAMAGE. 27 */ 28 29 #include <sys/cdefs.h> 30 __FBSDID("$FreeBSD$"); 31 32 #include <sys/param.h> 33 #include <sys/kernel.h> 34 #include <sys/lock.h> 35 #include <sys/module.h> 36 #include <sys/mutex.h> 37 #include <sys/proc.h> 38 #include <sys/resourcevar.h> 39 #include <sys/sx.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> 45 46 /* 47 * Acts like "nosys" but can be identified in sysent for dynamic call 48 * number assignment for a limited number of calls. 49 * 50 * Place holder for system call slots reserved for loadable modules. 51 */ 52 int 53 lkmnosys(struct thread *td, struct nosys_args *args) 54 { 55 56 return (nosys(td, args)); 57 } 58 59 int 60 lkmressys(struct thread *td, struct nosys_args *args) 61 { 62 63 return (nosys(td, args)); 64 } 65 66 static void 67 syscall_thread_drain(struct sysent *se) 68 { 69 u_int32_t cnt, oldcnt; 70 71 do { 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, 78 SY_THR_ABSENT) == 0) 79 pause("scdrn", hz/2); 80 } 81 82 int 83 _syscall_thread_enter(struct thread *td, struct sysent *se) 84 { 85 u_int32_t cnt, oldcnt; 86 87 do { 88 oldcnt = se->sy_thrcnt; 89 if ((oldcnt & (SY_THR_DRAINING | SY_THR_ABSENT)) != 0) 90 return (ENOSYS); 91 cnt = oldcnt + SY_THR_INCR; 92 } while (atomic_cmpset_acq_32(&se->sy_thrcnt, oldcnt, cnt) == 0); 93 return (0); 94 } 95 96 void 97 _syscall_thread_exit(struct thread *td, struct sysent *se) 98 { 99 u_int32_t cnt, oldcnt; 100 101 do { 102 oldcnt = se->sy_thrcnt; 103 cnt = oldcnt - SY_THR_INCR; 104 } while (atomic_cmpset_rel_32(&se->sy_thrcnt, oldcnt, cnt) == 0); 105 } 106 107 int 108 kern_syscall_register(struct sysent *sysents, int *offset, 109 struct sysent *new_sysent, struct sysent *old_sysent, int flags) 110 { 111 int i; 112 113 if ((flags & ~SY_THR_STATIC) != 0) 114 return (EINVAL); 115 116 if (*offset == NO_SYSCALL) { 117 for (i = 1; i < SYS_MAXSYSCALL; ++i) 118 if (sysents[i].sy_call == (sy_call_t *)lkmnosys) 119 break; 120 if (i == SYS_MAXSYSCALL) 121 return (ENFILE); 122 *offset = i; 123 } else if (*offset < 0 || *offset >= SYS_MAXSYSCALL) 124 return (EINVAL); 125 else if (sysents[*offset].sy_call != (sy_call_t *)lkmnosys && 126 sysents[*offset].sy_call != (sy_call_t *)lkmressys) 127 return (EEXIST); 128 129 KASSERT(sysents[*offset].sy_thrcnt == SY_THR_ABSENT, 130 ("dynamic syscall is not protected")); 131 *old_sysent = sysents[*offset]; 132 new_sysent->sy_thrcnt = SY_THR_ABSENT; 133 sysents[*offset] = *new_sysent; 134 atomic_store_rel_32(&sysents[*offset].sy_thrcnt, flags); 135 return (0); 136 } 137 138 int 139 kern_syscall_deregister(struct sysent *sysents, int offset, 140 const struct sysent *old_sysent) 141 { 142 struct sysent *se; 143 144 if (offset == 0) 145 return (0); /* XXX? */ 146 147 se = &sysents[offset]; 148 if ((se->sy_thrcnt & SY_THR_STATIC) != 0) 149 return (EINVAL); 150 syscall_thread_drain(se); 151 sysent[offset] = *old_sysent; 152 return (0); 153 } 154 155 int 156 syscall_module_handler(struct module *mod, int what, void *arg) 157 { 158 159 return (kern_syscall_module_handler(sysent, mod, what, arg)); 160 } 161 162 int 163 kern_syscall_module_handler(struct sysent *sysents, struct module *mod, 164 int what, void *arg) 165 { 166 struct syscall_module_data *data = arg; 167 modspecific_t ms; 168 int error; 169 170 switch (what) { 171 case MOD_LOAD: 172 error = kern_syscall_register(sysents, data->offset, 173 data->new_sysent, &data->old_sysent, data->flags); 174 if (error) { 175 /* Leave a mark so we know to safely unload below. */ 176 data->offset = NULL; 177 return (error); 178 } 179 ms.intval = *data->offset; 180 MOD_XLOCK; 181 module_setspecific(mod, &ms); 182 MOD_XUNLOCK; 183 if (data->chainevh) 184 error = data->chainevh(mod, what, data->chainarg); 185 return (error); 186 case MOD_UNLOAD: 187 /* 188 * MOD_LOAD failed, so just return without calling the 189 * chained handler since we didn't pass along the MOD_LOAD 190 * event. 191 */ 192 if (data->offset == NULL) 193 return (0); 194 if (data->chainevh) { 195 error = data->chainevh(mod, what, data->chainarg); 196 if (error) 197 return error; 198 } 199 error = kern_syscall_deregister(sysents, *data->offset, 200 &data->old_sysent); 201 return (error); 202 default: 203 if (data->chainevh) 204 return (data->chainevh(mod, what, data->chainarg)); 205 return (EOPNOTSUPP); 206 } 207 208 /* NOTREACHED */ 209 } 210 211 int 212 syscall_helper_register(struct syscall_helper_data *sd, int flags) 213 { 214 215 return (kern_syscall_helper_register(sysent, sd, flags)); 216 } 217 218 int 219 kern_syscall_helper_register(struct sysent *sysents, 220 struct syscall_helper_data *sd, int flags) 221 { 222 struct syscall_helper_data *sd1; 223 int error; 224 225 for (sd1 = sd; sd1->syscall_no != NO_SYSCALL; sd1++) { 226 error = kern_syscall_register(sysents, &sd1->syscall_no, 227 &sd1->new_sysent, &sd1->old_sysent, flags); 228 if (error != 0) { 229 kern_syscall_helper_unregister(sysents, sd); 230 return (error); 231 } 232 sd1->registered = 1; 233 } 234 return (0); 235 } 236 237 int 238 syscall_helper_unregister(struct syscall_helper_data *sd) 239 { 240 241 return (kern_syscall_helper_unregister(sysent, sd)); 242 } 243 244 int 245 kern_syscall_helper_unregister(struct sysent *sysents, 246 struct syscall_helper_data *sd) 247 { 248 struct syscall_helper_data *sd1; 249 250 for (sd1 = sd; sd1->registered != 0; sd1++) { 251 kern_syscall_deregister(sysents, sd1->syscall_no, 252 &sd1->old_sysent); 253 sd1->registered = 0; 254 } 255 return (0); 256 } 257