1 /*- 2 * Copyright (c) 1999 Assar Westerlund 3 * All rights reserved. 4 * 5 * Redistribution and use in source and binary forms, with or without 6 * modification, are permitted provided that the following conditions 7 * are met: 8 * 1. Redistributions of source code must retain the above copyright 9 * notice, this list of conditions and the following disclaimer. 10 * 2. Redistributions in binary form must reproduce the above copyright 11 * notice, this list of conditions and the following disclaimer in the 12 * documentation and/or other materials provided with the distribution. 13 * 14 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND 15 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 16 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 17 * ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE 18 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 19 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 20 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 21 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 22 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 23 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 24 * SUCH DAMAGE. 25 */ 26 27 #include <sys/cdefs.h> 28 __FBSDID("$FreeBSD$"); 29 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 u_int32_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 u_int32_t cnt, oldcnt; 84 85 do { 86 oldcnt = se->sy_thrcnt; 87 if ((oldcnt & SY_THR_STATIC) != 0) 88 return (0); 89 if ((oldcnt & (SY_THR_DRAINING | SY_THR_ABSENT)) != 0) 90 return (ENOSYS); 91 cnt = oldcnt + SY_THR_INCR; 92 } while (atomic_cmpset_acq_32(&se->sy_thrcnt, oldcnt, cnt) == 0); 93 return (0); 94 } 95 96 void 97 syscall_thread_exit(struct thread *td, struct sysent *se) 98 { 99 u_int32_t cnt, oldcnt; 100 101 do { 102 oldcnt = se->sy_thrcnt; 103 if ((oldcnt & SY_THR_STATIC) != 0) 104 return; 105 cnt = oldcnt - SY_THR_INCR; 106 } while (atomic_cmpset_rel_32(&se->sy_thrcnt, oldcnt, cnt) == 0); 107 } 108 109 int 110 syscall_register(int *offset, struct sysent *new_sysent, 111 struct sysent *old_sysent, int flags) 112 { 113 int i; 114 115 if ((flags & ~SY_THR_STATIC) != 0) 116 return (EINVAL); 117 118 if (*offset == NO_SYSCALL) { 119 for (i = 1; i < SYS_MAXSYSCALL; ++i) 120 if (sysent[i].sy_call == (sy_call_t *)lkmnosys) 121 break; 122 if (i == SYS_MAXSYSCALL) 123 return (ENFILE); 124 *offset = i; 125 } else if (*offset < 0 || *offset >= SYS_MAXSYSCALL) 126 return (EINVAL); 127 else if (sysent[*offset].sy_call != (sy_call_t *)lkmnosys && 128 sysent[*offset].sy_call != (sy_call_t *)lkmressys) 129 return (EEXIST); 130 131 KASSERT(sysent[*offset].sy_thrcnt == SY_THR_ABSENT, 132 ("dynamic syscall is not protected")); 133 *old_sysent = sysent[*offset]; 134 new_sysent->sy_thrcnt = SY_THR_ABSENT; 135 sysent[*offset] = *new_sysent; 136 atomic_store_rel_32(&sysent[*offset].sy_thrcnt, flags); 137 return (0); 138 } 139 140 int 141 syscall_deregister(int *offset, struct sysent *old_sysent) 142 { 143 struct sysent *se; 144 145 if (*offset == 0) 146 return (0); /* XXX? */ 147 148 se = &sysent[*offset]; 149 if ((se->sy_thrcnt & SY_THR_STATIC) != 0) 150 return (EINVAL); 151 syscall_thread_drain(se); 152 sysent[*offset] = *old_sysent; 153 return (0); 154 } 155 156 int 157 syscall_module_handler(struct module *mod, int what, void *arg) 158 { 159 struct syscall_module_data *data = arg; 160 modspecific_t ms; 161 int error; 162 163 switch (what) { 164 case MOD_LOAD: 165 error = syscall_register(data->offset, data->new_sysent, 166 &data->old_sysent, data->flags); 167 if (error) { 168 /* Leave a mark so we know to safely unload below. */ 169 data->offset = NULL; 170 return (error); 171 } 172 ms.intval = *data->offset; 173 MOD_XLOCK; 174 module_setspecific(mod, &ms); 175 MOD_XUNLOCK; 176 if (data->chainevh) 177 error = data->chainevh(mod, what, data->chainarg); 178 return (error); 179 case MOD_UNLOAD: 180 /* 181 * MOD_LOAD failed, so just return without calling the 182 * chained handler since we didn't pass along the MOD_LOAD 183 * event. 184 */ 185 if (data->offset == NULL) 186 return (0); 187 if (data->chainevh) { 188 error = data->chainevh(mod, what, data->chainarg); 189 if (error) 190 return error; 191 } 192 error = syscall_deregister(data->offset, &data->old_sysent); 193 return (error); 194 default: 195 if (data->chainevh) 196 return (data->chainevh(mod, what, data->chainarg)); 197 return (EOPNOTSUPP); 198 } 199 200 /* NOTREACHED */ 201 } 202 203 int 204 syscall_helper_register(struct syscall_helper_data *sd, int flags) 205 { 206 struct syscall_helper_data *sd1; 207 int error; 208 209 for (sd1 = sd; sd1->syscall_no != NO_SYSCALL; sd1++) { 210 error = syscall_register(&sd1->syscall_no, &sd1->new_sysent, 211 &sd1->old_sysent, flags); 212 if (error != 0) { 213 syscall_helper_unregister(sd); 214 return (error); 215 } 216 sd1->registered = 1; 217 } 218 return (0); 219 } 220 221 int 222 syscall_helper_unregister(struct syscall_helper_data *sd) 223 { 224 struct syscall_helper_data *sd1; 225 226 for (sd1 = sd; sd1->registered != 0; sd1++) { 227 syscall_deregister(&sd1->syscall_no, &sd1->old_sysent); 228 sd1->registered = 0; 229 } 230 return (0); 231 } 232