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 uint32_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 uint32_t cnt, oldcnt; 86 87 KASSERT((se->sy_thrcnt & SY_THR_STATIC) == 0, 88 ("%s: not a static syscall", __func__)); 89 90 do { 91 oldcnt = se->sy_thrcnt; 92 if ((oldcnt & (SY_THR_DRAINING | SY_THR_ABSENT)) != 0) 93 return (ENOSYS); 94 cnt = oldcnt + SY_THR_INCR; 95 } while (atomic_cmpset_acq_32(&se->sy_thrcnt, oldcnt, cnt) == 0); 96 return (0); 97 } 98 99 void 100 syscall_thread_exit(struct thread *td, struct sysent *se) 101 { 102 uint32_t cnt, oldcnt; 103 104 KASSERT((se->sy_thrcnt & SY_THR_STATIC) == 0, 105 ("%s: not a static syscall", __func__)); 106 107 do { 108 oldcnt = se->sy_thrcnt; 109 cnt = oldcnt - SY_THR_INCR; 110 } while (atomic_cmpset_rel_32(&se->sy_thrcnt, oldcnt, cnt) == 0); 111 } 112 113 int 114 kern_syscall_register(struct sysent *sysents, int *offset, 115 struct sysent *new_sysent, struct sysent *old_sysent, int flags) 116 { 117 int i; 118 119 if ((flags & ~SY_THR_STATIC) != 0) 120 return (EINVAL); 121 122 if (*offset == NO_SYSCALL) { 123 for (i = 1; i < SYS_MAXSYSCALL; ++i) 124 if (sysents[i].sy_call == (sy_call_t *)lkmnosys) 125 break; 126 if (i == SYS_MAXSYSCALL) 127 return (ENFILE); 128 *offset = i; 129 } else if (*offset < 0 || *offset >= SYS_MAXSYSCALL) { 130 return (EINVAL); 131 } else if (sysents[*offset].sy_call != (sy_call_t *)lkmnosys && 132 sysents[*offset].sy_call != (sy_call_t *)lkmressys) { 133 KASSERT(sysents[*offset].sy_call != NULL, 134 ("undefined syscall %d", *offset)); 135 return (EEXIST); 136 } 137 138 KASSERT(sysents[*offset].sy_thrcnt == SY_THR_ABSENT, 139 ("dynamic syscall is not protected")); 140 *old_sysent = sysents[*offset]; 141 new_sysent->sy_thrcnt = SY_THR_ABSENT; 142 sysents[*offset] = *new_sysent; 143 atomic_store_rel_32(&sysents[*offset].sy_thrcnt, flags); 144 return (0); 145 } 146 147 int 148 kern_syscall_deregister(struct sysent *sysents, int offset, 149 const struct sysent *old_sysent) 150 { 151 struct sysent *se; 152 153 if (offset == 0) 154 return (0); /* XXX? */ 155 156 se = &sysents[offset]; 157 if ((se->sy_thrcnt & SY_THR_STATIC) != 0) 158 return (EINVAL); 159 syscall_thread_drain(se); 160 sysents[offset] = *old_sysent; 161 return (0); 162 } 163 164 int 165 syscall_module_handler(struct module *mod, int what, void *arg) 166 { 167 168 return (kern_syscall_module_handler(sysent, mod, what, arg)); 169 } 170 171 int 172 kern_syscall_module_handler(struct sysent *sysents, struct module *mod, 173 int what, void *arg) 174 { 175 struct syscall_module_data *data = arg; 176 modspecific_t ms; 177 int error; 178 179 switch (what) { 180 case MOD_LOAD: 181 error = kern_syscall_register(sysents, data->offset, 182 data->new_sysent, &data->old_sysent, data->flags); 183 if (error) { 184 /* Leave a mark so we know to safely unload below. */ 185 data->offset = NULL; 186 return (error); 187 } 188 ms.intval = *data->offset; 189 MOD_XLOCK; 190 module_setspecific(mod, &ms); 191 MOD_XUNLOCK; 192 if (data->chainevh) 193 error = data->chainevh(mod, what, data->chainarg); 194 return (error); 195 case MOD_UNLOAD: 196 /* 197 * MOD_LOAD failed, so just return without calling the 198 * chained handler since we didn't pass along the MOD_LOAD 199 * event. 200 */ 201 if (data->offset == NULL) 202 return (0); 203 if (data->chainevh) { 204 error = data->chainevh(mod, what, data->chainarg); 205 if (error) 206 return error; 207 } 208 error = kern_syscall_deregister(sysents, *data->offset, 209 &data->old_sysent); 210 return (error); 211 default: 212 if (data->chainevh) 213 return (data->chainevh(mod, what, data->chainarg)); 214 return (EOPNOTSUPP); 215 } 216 217 /* NOTREACHED */ 218 } 219 220 int 221 syscall_helper_register(struct syscall_helper_data *sd, int flags) 222 { 223 224 return (kern_syscall_helper_register(sysent, sd, flags)); 225 } 226 227 int 228 kern_syscall_helper_register(struct sysent *sysents, 229 struct syscall_helper_data *sd, int flags) 230 { 231 struct syscall_helper_data *sd1; 232 int error; 233 234 for (sd1 = sd; sd1->syscall_no != NO_SYSCALL; sd1++) { 235 error = kern_syscall_register(sysents, &sd1->syscall_no, 236 &sd1->new_sysent, &sd1->old_sysent, flags); 237 if (error != 0) { 238 kern_syscall_helper_unregister(sysents, sd); 239 return (error); 240 } 241 sd1->registered = 1; 242 } 243 return (0); 244 } 245 246 int 247 syscall_helper_unregister(struct syscall_helper_data *sd) 248 { 249 250 return (kern_syscall_helper_unregister(sysent, sd)); 251 } 252 253 int 254 kern_syscall_helper_unregister(struct sysent *sysents, 255 struct syscall_helper_data *sd) 256 { 257 struct syscall_helper_data *sd1; 258 259 for (sd1 = sd; sd1->registered != 0; sd1++) { 260 kern_syscall_deregister(sysents, sd1->syscall_no, 261 &sd1->old_sysent); 262 sd1->registered = 0; 263 } 264 return (0); 265 } 266