1 /*- 2 * SPDX-License-Identifier: BSD-2-Clause 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/param.h> 30 #include <sys/kernel.h> 31 #include <sys/lock.h> 32 #include <sys/module.h> 33 #include <sys/mutex.h> 34 #include <sys/proc.h> 35 #include <sys/resourcevar.h> 36 #include <sys/sx.h> 37 #include <sys/syscall.h> 38 #include <sys/syscallsubr.h> 39 #include <sys/sysent.h> 40 #include <sys/sysproto.h> 41 #include <sys/systm.h> 42 #include <machine/atomic.h> 43 44 /* 45 * Acts like "nosys" but can be identified in sysent for dynamic call 46 * number assignment for a limited number of calls. 47 * 48 * Place holder for system call slots reserved for loadable modules. 49 */ 50 int 51 lkmnosys(struct thread *td, struct nosys_args *args) 52 { 53 54 return (kern_nosys(td, 0)); 55 } 56 57 int 58 lkmressys(struct thread *td, struct nosys_args *args) 59 { 60 61 return (kern_nosys(td, 0)); 62 } 63 64 struct sysent nosys_sysent = { 65 .sy_call = (sy_call_t *)nosys, 66 .sy_systrace_args_func = NULL, 67 .sy_narg = 0, 68 .sy_flags = SYF_CAPENABLED, 69 .sy_auevent = AUE_NULL, 70 .sy_entry = 0, /* DTRACE_IDNONE */ 71 .sy_return = 0, 72 .sy_thrcnt = SY_THR_STATIC, 73 }; 74 75 static void 76 syscall_thread_drain(struct sysent *se) 77 { 78 uint32_t cnt, oldcnt; 79 80 do { 81 oldcnt = se->sy_thrcnt; 82 KASSERT((oldcnt & SY_THR_STATIC) == 0, 83 ("drain on static syscall")); 84 cnt = oldcnt | SY_THR_DRAINING; 85 } while (atomic_cmpset_acq_32(&se->sy_thrcnt, oldcnt, cnt) == 0); 86 while (atomic_cmpset_32(&se->sy_thrcnt, SY_THR_DRAINING, 87 SY_THR_ABSENT) == 0) 88 pause("scdrn", hz/2); 89 } 90 91 int 92 syscall_thread_enter(struct thread *td, struct sysent **se) 93 { 94 uint32_t cnt, oldcnt; 95 96 KASSERT(((*se)->sy_thrcnt & SY_THR_STATIC) == 0, 97 ("%s: not a static syscall", __func__)); 98 99 do { 100 oldcnt = (*se)->sy_thrcnt; 101 if ((oldcnt & (SY_THR_DRAINING | SY_THR_ABSENT)) != 0) { 102 *se = &nosys_sysent; 103 return (0); 104 } 105 cnt = oldcnt + SY_THR_INCR; 106 } while (atomic_cmpset_acq_32(&(*se)->sy_thrcnt, oldcnt, cnt) == 0); 107 return (0); 108 } 109 110 void 111 syscall_thread_exit(struct thread *td, struct sysent *se) 112 { 113 uint32_t cnt, oldcnt; 114 115 KASSERT((se->sy_thrcnt & SY_THR_STATIC) == 0, 116 ("%s: not a static syscall", __func__)); 117 118 do { 119 oldcnt = se->sy_thrcnt; 120 cnt = oldcnt - SY_THR_INCR; 121 } while (atomic_cmpset_rel_32(&se->sy_thrcnt, oldcnt, cnt) == 0); 122 } 123 124 int 125 kern_syscall_register(struct sysent *sysents, int *offset, 126 struct sysent *new_sysent, struct sysent *old_sysent, int flags) 127 { 128 int i; 129 130 if ((flags & ~SY_THR_STATIC) != 0) 131 return (EINVAL); 132 133 if (*offset == NO_SYSCALL) { 134 for (i = 1; i < SYS_MAXSYSCALL; ++i) 135 if (sysents[i].sy_call == (sy_call_t *)lkmnosys) 136 break; 137 if (i == SYS_MAXSYSCALL) 138 return (ENFILE); 139 *offset = i; 140 } else if (*offset < 0 || *offset >= SYS_MAXSYSCALL) { 141 return (EINVAL); 142 } else if (sysents[*offset].sy_call != (sy_call_t *)lkmnosys && 143 sysents[*offset].sy_call != (sy_call_t *)lkmressys) { 144 KASSERT(sysents[*offset].sy_call != NULL, 145 ("undefined syscall %d", *offset)); 146 return (EEXIST); 147 } 148 149 KASSERT(sysents[*offset].sy_thrcnt == SY_THR_ABSENT, 150 ("dynamic syscall is not protected")); 151 *old_sysent = sysents[*offset]; 152 new_sysent->sy_thrcnt = SY_THR_ABSENT; 153 sysents[*offset] = *new_sysent; 154 atomic_store_rel_32(&sysents[*offset].sy_thrcnt, flags); 155 return (0); 156 } 157 158 int 159 kern_syscall_deregister(struct sysent *sysents, int offset, 160 const struct sysent *old_sysent) 161 { 162 struct sysent *se; 163 164 if (offset == 0) { 165 /* 166 * Syscall #0 is reserved and is not dynamically registered. 167 * Treat deregistration as a no-op to simplify module unload 168 * paths. 169 */ 170 return (0); 171 } 172 173 se = &sysents[offset]; 174 if ((se->sy_thrcnt & SY_THR_STATIC) != 0) 175 return (EINVAL); 176 syscall_thread_drain(se); 177 sysents[offset] = *old_sysent; 178 return (0); 179 } 180 181 int 182 syscall_module_handler(struct module *mod, int what, void *arg) 183 { 184 185 return (kern_syscall_module_handler(sysent, mod, what, arg)); 186 } 187 188 int 189 kern_syscall_module_handler(struct sysent *sysents, struct module *mod, 190 int what, void *arg) 191 { 192 struct syscall_module_data *data = arg; 193 modspecific_t ms; 194 int error; 195 196 bzero(&ms, sizeof(ms)); 197 switch (what) { 198 case MOD_LOAD: 199 error = kern_syscall_register(sysents, data->offset, 200 data->new_sysent, &data->old_sysent, data->flags); 201 if (error) { 202 /* Leave a mark so we know to safely unload below. */ 203 data->offset = NULL; 204 return (error); 205 } 206 ms.intval = *data->offset; 207 MOD_XLOCK; 208 module_setspecific(mod, &ms); 209 MOD_XUNLOCK; 210 if (data->chainevh) 211 error = data->chainevh(mod, what, data->chainarg); 212 return (error); 213 case MOD_UNLOAD: 214 /* 215 * MOD_LOAD failed, so just return without calling the 216 * chained handler since we didn't pass along the MOD_LOAD 217 * event. 218 */ 219 if (data->offset == NULL) 220 return (0); 221 if (data->chainevh) { 222 error = data->chainevh(mod, what, data->chainarg); 223 if (error) 224 return error; 225 } 226 error = kern_syscall_deregister(sysents, *data->offset, 227 &data->old_sysent); 228 return (error); 229 default: 230 if (data->chainevh) 231 return (data->chainevh(mod, what, data->chainarg)); 232 return (EOPNOTSUPP); 233 } 234 235 /* NOTREACHED */ 236 } 237 238 int 239 syscall_helper_register(struct syscall_helper_data *sd, int flags) 240 { 241 242 return (kern_syscall_helper_register(sysent, sd, flags)); 243 } 244 245 int 246 kern_syscall_helper_register(struct sysent *sysents, 247 struct syscall_helper_data *sd, int flags) 248 { 249 struct syscall_helper_data *sd1; 250 int error; 251 252 for (sd1 = sd; sd1->syscall_no != NO_SYSCALL; sd1++) { 253 error = kern_syscall_register(sysents, &sd1->syscall_no, 254 &sd1->new_sysent, &sd1->old_sysent, flags); 255 if (error != 0) { 256 kern_syscall_helper_unregister(sysents, sd); 257 return (error); 258 } 259 sd1->registered = 1; 260 } 261 return (0); 262 } 263 264 int 265 syscall_helper_unregister(struct syscall_helper_data *sd) 266 { 267 268 return (kern_syscall_helper_unregister(sysent, sd)); 269 } 270 271 int 272 kern_syscall_helper_unregister(struct sysent *sysents, 273 struct syscall_helper_data *sd) 274 { 275 struct syscall_helper_data *sd1; 276 277 for (sd1 = sd; sd1->registered != 0; sd1++) { 278 kern_syscall_deregister(sysents, sd1->syscall_no, 279 &sd1->old_sysent); 280 sd1->registered = 0; 281 } 282 return (0); 283 } 284