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 static void 65 syscall_thread_drain(struct sysent *se) 66 { 67 uint32_t cnt, oldcnt; 68 69 do { 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, 76 SY_THR_ABSENT) == 0) 77 pause("scdrn", hz/2); 78 } 79 80 int 81 syscall_thread_enter(struct thread *td, struct sysent *se) 82 { 83 uint32_t cnt, oldcnt; 84 85 KASSERT((se->sy_thrcnt & SY_THR_STATIC) == 0, 86 ("%s: not a static syscall", __func__)); 87 88 do { 89 oldcnt = se->sy_thrcnt; 90 if ((oldcnt & (SY_THR_DRAINING | SY_THR_ABSENT)) != 0) 91 return (ENOSYS); 92 cnt = oldcnt + SY_THR_INCR; 93 } while (atomic_cmpset_acq_32(&se->sy_thrcnt, oldcnt, cnt) == 0); 94 return (0); 95 } 96 97 void 98 syscall_thread_exit(struct thread *td, struct sysent *se) 99 { 100 uint32_t cnt, oldcnt; 101 102 KASSERT((se->sy_thrcnt & SY_THR_STATIC) == 0, 103 ("%s: not a static syscall", __func__)); 104 105 do { 106 oldcnt = se->sy_thrcnt; 107 cnt = oldcnt - SY_THR_INCR; 108 } while (atomic_cmpset_rel_32(&se->sy_thrcnt, oldcnt, cnt) == 0); 109 } 110 111 int 112 kern_syscall_register(struct sysent *sysents, int *offset, 113 struct sysent *new_sysent, struct sysent *old_sysent, int flags) 114 { 115 int i; 116 117 if ((flags & ~SY_THR_STATIC) != 0) 118 return (EINVAL); 119 120 if (*offset == NO_SYSCALL) { 121 for (i = 1; i < SYS_MAXSYSCALL; ++i) 122 if (sysents[i].sy_call == (sy_call_t *)lkmnosys) 123 break; 124 if (i == SYS_MAXSYSCALL) 125 return (ENFILE); 126 *offset = i; 127 } else if (*offset < 0 || *offset >= SYS_MAXSYSCALL) { 128 return (EINVAL); 129 } else if (sysents[*offset].sy_call != (sy_call_t *)lkmnosys && 130 sysents[*offset].sy_call != (sy_call_t *)lkmressys) { 131 KASSERT(sysents[*offset].sy_call != NULL, 132 ("undefined syscall %d", *offset)); 133 return (EEXIST); 134 } 135 136 KASSERT(sysents[*offset].sy_thrcnt == SY_THR_ABSENT, 137 ("dynamic syscall is not protected")); 138 *old_sysent = sysents[*offset]; 139 new_sysent->sy_thrcnt = SY_THR_ABSENT; 140 sysents[*offset] = *new_sysent; 141 atomic_store_rel_32(&sysents[*offset].sy_thrcnt, flags); 142 return (0); 143 } 144 145 int 146 kern_syscall_deregister(struct sysent *sysents, int offset, 147 const struct sysent *old_sysent) 148 { 149 struct sysent *se; 150 151 if (offset == 0) 152 return (0); /* XXX? */ 153 154 se = &sysents[offset]; 155 if ((se->sy_thrcnt & SY_THR_STATIC) != 0) 156 return (EINVAL); 157 syscall_thread_drain(se); 158 sysents[offset] = *old_sysent; 159 return (0); 160 } 161 162 int 163 syscall_module_handler(struct module *mod, int what, void *arg) 164 { 165 166 return (kern_syscall_module_handler(sysent, mod, what, arg)); 167 } 168 169 int 170 kern_syscall_module_handler(struct sysent *sysents, struct module *mod, 171 int what, void *arg) 172 { 173 struct syscall_module_data *data = arg; 174 modspecific_t ms; 175 int error; 176 177 bzero(&ms, sizeof(ms)); 178 switch (what) { 179 case MOD_LOAD: 180 error = kern_syscall_register(sysents, data->offset, 181 data->new_sysent, &data->old_sysent, data->flags); 182 if (error) { 183 /* Leave a mark so we know to safely unload below. */ 184 data->offset = NULL; 185 return (error); 186 } 187 ms.intval = *data->offset; 188 MOD_XLOCK; 189 module_setspecific(mod, &ms); 190 MOD_XUNLOCK; 191 if (data->chainevh) 192 error = data->chainevh(mod, what, data->chainarg); 193 return (error); 194 case MOD_UNLOAD: 195 /* 196 * MOD_LOAD failed, so just return without calling the 197 * chained handler since we didn't pass along the MOD_LOAD 198 * event. 199 */ 200 if (data->offset == NULL) 201 return (0); 202 if (data->chainevh) { 203 error = data->chainevh(mod, what, data->chainarg); 204 if (error) 205 return error; 206 } 207 error = kern_syscall_deregister(sysents, *data->offset, 208 &data->old_sysent); 209 return (error); 210 default: 211 if (data->chainevh) 212 return (data->chainevh(mod, what, data->chainarg)); 213 return (EOPNOTSUPP); 214 } 215 216 /* NOTREACHED */ 217 } 218 219 int 220 syscall_helper_register(struct syscall_helper_data *sd, int flags) 221 { 222 223 return (kern_syscall_helper_register(sysent, sd, flags)); 224 } 225 226 int 227 kern_syscall_helper_register(struct sysent *sysents, 228 struct syscall_helper_data *sd, int flags) 229 { 230 struct syscall_helper_data *sd1; 231 int error; 232 233 for (sd1 = sd; sd1->syscall_no != NO_SYSCALL; sd1++) { 234 error = kern_syscall_register(sysents, &sd1->syscall_no, 235 &sd1->new_sysent, &sd1->old_sysent, flags); 236 if (error != 0) { 237 kern_syscall_helper_unregister(sysents, sd); 238 return (error); 239 } 240 sd1->registered = 1; 241 } 242 return (0); 243 } 244 245 int 246 syscall_helper_unregister(struct syscall_helper_data *sd) 247 { 248 249 return (kern_syscall_helper_unregister(sysent, sd)); 250 } 251 252 int 253 kern_syscall_helper_unregister(struct sysent *sysents, 254 struct syscall_helper_data *sd) 255 { 256 struct syscall_helper_data *sd1; 257 258 for (sd1 = sd; sd1->registered != 0; sd1++) { 259 kern_syscall_deregister(sysents, sd1->syscall_no, 260 &sd1->old_sysent); 261 sd1->registered = 0; 262 } 263 return (0); 264 } 265