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/cdefs.h> 30 #include <sys/param.h> 31 #include <sys/kernel.h> 32 #include <sys/lock.h> 33 #include <sys/module.h> 34 #include <sys/mutex.h> 35 #include <sys/proc.h> 36 #include <sys/resourcevar.h> 37 #include <sys/sx.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> 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 (nosys(td, args)); 55 } 56 57 int 58 lkmressys(struct thread *td, struct nosys_args *args) 59 { 60 61 return (nosys(td, args)); 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 return (0); /* XXX? */ 166 167 se = &sysents[offset]; 168 if ((se->sy_thrcnt & SY_THR_STATIC) != 0) 169 return (EINVAL); 170 syscall_thread_drain(se); 171 sysents[offset] = *old_sysent; 172 return (0); 173 } 174 175 int 176 syscall_module_handler(struct module *mod, int what, void *arg) 177 { 178 179 return (kern_syscall_module_handler(sysent, mod, what, arg)); 180 } 181 182 int 183 kern_syscall_module_handler(struct sysent *sysents, struct module *mod, 184 int what, void *arg) 185 { 186 struct syscall_module_data *data = arg; 187 modspecific_t ms; 188 int error; 189 190 bzero(&ms, sizeof(ms)); 191 switch (what) { 192 case MOD_LOAD: 193 error = kern_syscall_register(sysents, data->offset, 194 data->new_sysent, &data->old_sysent, data->flags); 195 if (error) { 196 /* Leave a mark so we know to safely unload below. */ 197 data->offset = NULL; 198 return (error); 199 } 200 ms.intval = *data->offset; 201 MOD_XLOCK; 202 module_setspecific(mod, &ms); 203 MOD_XUNLOCK; 204 if (data->chainevh) 205 error = data->chainevh(mod, what, data->chainarg); 206 return (error); 207 case MOD_UNLOAD: 208 /* 209 * MOD_LOAD failed, so just return without calling the 210 * chained handler since we didn't pass along the MOD_LOAD 211 * event. 212 */ 213 if (data->offset == NULL) 214 return (0); 215 if (data->chainevh) { 216 error = data->chainevh(mod, what, data->chainarg); 217 if (error) 218 return error; 219 } 220 error = kern_syscall_deregister(sysents, *data->offset, 221 &data->old_sysent); 222 return (error); 223 default: 224 if (data->chainevh) 225 return (data->chainevh(mod, what, data->chainarg)); 226 return (EOPNOTSUPP); 227 } 228 229 /* NOTREACHED */ 230 } 231 232 int 233 syscall_helper_register(struct syscall_helper_data *sd, int flags) 234 { 235 236 return (kern_syscall_helper_register(sysent, sd, flags)); 237 } 238 239 int 240 kern_syscall_helper_register(struct sysent *sysents, 241 struct syscall_helper_data *sd, int flags) 242 { 243 struct syscall_helper_data *sd1; 244 int error; 245 246 for (sd1 = sd; sd1->syscall_no != NO_SYSCALL; sd1++) { 247 error = kern_syscall_register(sysents, &sd1->syscall_no, 248 &sd1->new_sysent, &sd1->old_sysent, flags); 249 if (error != 0) { 250 kern_syscall_helper_unregister(sysents, sd); 251 return (error); 252 } 253 sd1->registered = 1; 254 } 255 return (0); 256 } 257 258 int 259 syscall_helper_unregister(struct syscall_helper_data *sd) 260 { 261 262 return (kern_syscall_helper_unregister(sysent, sd)); 263 } 264 265 int 266 kern_syscall_helper_unregister(struct sysent *sysents, 267 struct syscall_helper_data *sd) 268 { 269 struct syscall_helper_data *sd1; 270 271 for (sd1 = sd; sd1->registered != 0; sd1++) { 272 kern_syscall_deregister(sysents, sd1->syscall_no, 273 &sd1->old_sysent); 274 sd1->registered = 0; 275 } 276 return (0); 277 } 278