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/sysent.h> 39 #include <sys/sysproto.h> 40 #include <sys/systm.h> 41 #include <machine/atomic.h> 42 43 /* 44 * Acts like "nosys" but can be identified in sysent for dynamic call 45 * number assignment for a limited number of calls. 46 * 47 * Place holder for system call slots reserved for loadable modules. 48 */ 49 int 50 lkmnosys(struct thread *td, struct nosys_args *args) 51 { 52 53 return (nosys(td, args)); 54 } 55 56 int 57 lkmressys(struct thread *td, struct nosys_args *args) 58 { 59 60 return (nosys(td, args)); 61 } 62 63 struct sysent nosys_sysent = { 64 .sy_call = (sy_call_t *)nosys, 65 .sy_systrace_args_func = NULL, 66 .sy_narg = 0, 67 .sy_flags = SYF_CAPENABLED, 68 .sy_auevent = AUE_NULL, 69 .sy_entry = 0, /* DTRACE_IDNONE */ 70 .sy_return = 0, 71 .sy_thrcnt = SY_THR_STATIC, 72 }; 73 74 static void 75 syscall_thread_drain(struct sysent *se) 76 { 77 uint32_t cnt, oldcnt; 78 79 do { 80 oldcnt = se->sy_thrcnt; 81 KASSERT((oldcnt & SY_THR_STATIC) == 0, 82 ("drain on static syscall")); 83 cnt = oldcnt | SY_THR_DRAINING; 84 } while (atomic_cmpset_acq_32(&se->sy_thrcnt, oldcnt, cnt) == 0); 85 while (atomic_cmpset_32(&se->sy_thrcnt, SY_THR_DRAINING, 86 SY_THR_ABSENT) == 0) 87 pause("scdrn", hz/2); 88 } 89 90 int 91 syscall_thread_enter(struct thread *td, struct sysent **se) 92 { 93 uint32_t cnt, oldcnt; 94 95 KASSERT(((*se)->sy_thrcnt & SY_THR_STATIC) == 0, 96 ("%s: not a static syscall", __func__)); 97 98 do { 99 oldcnt = (*se)->sy_thrcnt; 100 if ((oldcnt & (SY_THR_DRAINING | SY_THR_ABSENT)) != 0) { 101 *se = &nosys_sysent; 102 return (0); 103 } 104 cnt = oldcnt + SY_THR_INCR; 105 } while (atomic_cmpset_acq_32(&(*se)->sy_thrcnt, oldcnt, cnt) == 0); 106 return (0); 107 } 108 109 void 110 syscall_thread_exit(struct thread *td, struct sysent *se) 111 { 112 uint32_t cnt, oldcnt; 113 114 KASSERT((se->sy_thrcnt & SY_THR_STATIC) == 0, 115 ("%s: not a static syscall", __func__)); 116 117 do { 118 oldcnt = se->sy_thrcnt; 119 cnt = oldcnt - SY_THR_INCR; 120 } while (atomic_cmpset_rel_32(&se->sy_thrcnt, oldcnt, cnt) == 0); 121 } 122 123 int 124 kern_syscall_register(struct sysent *sysents, int *offset, 125 struct sysent *new_sysent, struct sysent *old_sysent, int flags) 126 { 127 int i; 128 129 if ((flags & ~SY_THR_STATIC) != 0) 130 return (EINVAL); 131 132 if (*offset == NO_SYSCALL) { 133 for (i = 1; i < SYS_MAXSYSCALL; ++i) 134 if (sysents[i].sy_call == (sy_call_t *)lkmnosys) 135 break; 136 if (i == SYS_MAXSYSCALL) 137 return (ENFILE); 138 *offset = i; 139 } else if (*offset < 0 || *offset >= SYS_MAXSYSCALL) { 140 return (EINVAL); 141 } else if (sysents[*offset].sy_call != (sy_call_t *)lkmnosys && 142 sysents[*offset].sy_call != (sy_call_t *)lkmressys) { 143 KASSERT(sysents[*offset].sy_call != NULL, 144 ("undefined syscall %d", *offset)); 145 return (EEXIST); 146 } 147 148 KASSERT(sysents[*offset].sy_thrcnt == SY_THR_ABSENT, 149 ("dynamic syscall is not protected")); 150 *old_sysent = sysents[*offset]; 151 new_sysent->sy_thrcnt = SY_THR_ABSENT; 152 sysents[*offset] = *new_sysent; 153 atomic_store_rel_32(&sysents[*offset].sy_thrcnt, flags); 154 return (0); 155 } 156 157 int 158 kern_syscall_deregister(struct sysent *sysents, int offset, 159 const struct sysent *old_sysent) 160 { 161 struct sysent *se; 162 163 if (offset == 0) 164 return (0); /* XXX? */ 165 166 se = &sysents[offset]; 167 if ((se->sy_thrcnt & SY_THR_STATIC) != 0) 168 return (EINVAL); 169 syscall_thread_drain(se); 170 sysents[offset] = *old_sysent; 171 return (0); 172 } 173 174 int 175 syscall_module_handler(struct module *mod, int what, void *arg) 176 { 177 178 return (kern_syscall_module_handler(sysent, mod, what, arg)); 179 } 180 181 int 182 kern_syscall_module_handler(struct sysent *sysents, struct module *mod, 183 int what, void *arg) 184 { 185 struct syscall_module_data *data = arg; 186 modspecific_t ms; 187 int error; 188 189 bzero(&ms, sizeof(ms)); 190 switch (what) { 191 case MOD_LOAD: 192 error = kern_syscall_register(sysents, data->offset, 193 data->new_sysent, &data->old_sysent, data->flags); 194 if (error) { 195 /* Leave a mark so we know to safely unload below. */ 196 data->offset = NULL; 197 return (error); 198 } 199 ms.intval = *data->offset; 200 MOD_XLOCK; 201 module_setspecific(mod, &ms); 202 MOD_XUNLOCK; 203 if (data->chainevh) 204 error = data->chainevh(mod, what, data->chainarg); 205 return (error); 206 case MOD_UNLOAD: 207 /* 208 * MOD_LOAD failed, so just return without calling the 209 * chained handler since we didn't pass along the MOD_LOAD 210 * event. 211 */ 212 if (data->offset == NULL) 213 return (0); 214 if (data->chainevh) { 215 error = data->chainevh(mod, what, data->chainarg); 216 if (error) 217 return error; 218 } 219 error = kern_syscall_deregister(sysents, *data->offset, 220 &data->old_sysent); 221 return (error); 222 default: 223 if (data->chainevh) 224 return (data->chainevh(mod, what, data->chainarg)); 225 return (EOPNOTSUPP); 226 } 227 228 /* NOTREACHED */ 229 } 230 231 int 232 syscall_helper_register(struct syscall_helper_data *sd, int flags) 233 { 234 235 return (kern_syscall_helper_register(sysent, sd, flags)); 236 } 237 238 int 239 kern_syscall_helper_register(struct sysent *sysents, 240 struct syscall_helper_data *sd, int flags) 241 { 242 struct syscall_helper_data *sd1; 243 int error; 244 245 for (sd1 = sd; sd1->syscall_no != NO_SYSCALL; sd1++) { 246 error = kern_syscall_register(sysents, &sd1->syscall_no, 247 &sd1->new_sysent, &sd1->old_sysent, flags); 248 if (error != 0) { 249 kern_syscall_helper_unregister(sysents, sd); 250 return (error); 251 } 252 sd1->registered = 1; 253 } 254 return (0); 255 } 256 257 int 258 syscall_helper_unregister(struct syscall_helper_data *sd) 259 { 260 261 return (kern_syscall_helper_unregister(sysent, sd)); 262 } 263 264 int 265 kern_syscall_helper_unregister(struct sysent *sysents, 266 struct syscall_helper_data *sd) 267 { 268 struct syscall_helper_data *sd1; 269 270 for (sd1 = sd; sd1->registered != 0; sd1++) { 271 kern_syscall_deregister(sysents, sd1->syscall_no, 272 &sd1->old_sysent); 273 sd1->registered = 0; 274 } 275 return (0); 276 } 277