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/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 static void 64 syscall_thread_drain(struct sysent *se) 65 { 66 u_int32_t cnt, oldcnt; 67 68 do { 69 oldcnt = se->sy_thrcnt; 70 KASSERT((oldcnt & SY_THR_STATIC) == 0, 71 ("drain on static syscall")); 72 cnt = oldcnt | SY_THR_DRAINING; 73 } while (atomic_cmpset_acq_32(&se->sy_thrcnt, oldcnt, cnt) == 0); 74 while (atomic_cmpset_32(&se->sy_thrcnt, SY_THR_DRAINING, 75 SY_THR_ABSENT) == 0) 76 pause("scdrn", hz/2); 77 } 78 79 int 80 syscall_thread_enter(struct thread *td, struct sysent *se) 81 { 82 u_int32_t cnt, oldcnt; 83 84 do { 85 oldcnt = se->sy_thrcnt; 86 if ((oldcnt & SY_THR_STATIC) != 0) 87 return (0); 88 if ((oldcnt & (SY_THR_DRAINING | SY_THR_ABSENT)) != 0) 89 return (ENOSYS); 90 cnt = oldcnt + SY_THR_INCR; 91 } while (atomic_cmpset_acq_32(&se->sy_thrcnt, oldcnt, cnt) == 0); 92 return (0); 93 } 94 95 void 96 syscall_thread_exit(struct thread *td, struct sysent *se) 97 { 98 u_int32_t cnt, oldcnt; 99 100 do { 101 oldcnt = se->sy_thrcnt; 102 if ((oldcnt & SY_THR_STATIC) != 0) 103 return; 104 cnt = oldcnt - SY_THR_INCR; 105 } while (atomic_cmpset_rel_32(&se->sy_thrcnt, oldcnt, cnt) == 0); 106 } 107 108 int 109 syscall_register(int *offset, struct sysent *new_sysent, 110 struct sysent *old_sysent, int flags) 111 { 112 int i; 113 114 if ((flags & ~SY_THR_STATIC) != 0) 115 return (EINVAL); 116 117 if (*offset == NO_SYSCALL) { 118 for (i = 1; i < SYS_MAXSYSCALL; ++i) 119 if (sysent[i].sy_call == (sy_call_t *)lkmnosys) 120 break; 121 if (i == SYS_MAXSYSCALL) 122 return (ENFILE); 123 *offset = i; 124 } else if (*offset < 0 || *offset >= SYS_MAXSYSCALL) 125 return (EINVAL); 126 else if (sysent[*offset].sy_call != (sy_call_t *)lkmnosys && 127 sysent[*offset].sy_call != (sy_call_t *)lkmressys) 128 return (EEXIST); 129 130 KASSERT(sysent[*offset].sy_thrcnt == SY_THR_ABSENT, 131 ("dynamic syscall is not protected")); 132 *old_sysent = sysent[*offset]; 133 new_sysent->sy_thrcnt = SY_THR_ABSENT; 134 sysent[*offset] = *new_sysent; 135 atomic_store_rel_32(&sysent[*offset].sy_thrcnt, flags); 136 return (0); 137 } 138 139 int 140 syscall_deregister(int *offset, struct sysent *old_sysent) 141 { 142 struct sysent *se; 143 144 if (*offset == 0) 145 return (0); /* XXX? */ 146 147 se = &sysent[*offset]; 148 if ((se->sy_thrcnt & SY_THR_STATIC) != 0) 149 return (EINVAL); 150 syscall_thread_drain(se); 151 sysent[*offset] = *old_sysent; 152 return (0); 153 } 154 155 int 156 syscall_module_handler(struct module *mod, int what, void *arg) 157 { 158 struct syscall_module_data *data = arg; 159 modspecific_t ms; 160 int error; 161 162 switch (what) { 163 case MOD_LOAD: 164 error = syscall_register(data->offset, data->new_sysent, 165 &data->old_sysent, data->flags); 166 if (error) { 167 /* Leave a mark so we know to safely unload below. */ 168 data->offset = NULL; 169 return (error); 170 } 171 ms.intval = *data->offset; 172 MOD_XLOCK; 173 module_setspecific(mod, &ms); 174 MOD_XUNLOCK; 175 if (data->chainevh) 176 error = data->chainevh(mod, what, data->chainarg); 177 return (error); 178 case MOD_UNLOAD: 179 /* 180 * MOD_LOAD failed, so just return without calling the 181 * chained handler since we didn't pass along the MOD_LOAD 182 * event. 183 */ 184 if (data->offset == NULL) 185 return (0); 186 if (data->chainevh) { 187 error = data->chainevh(mod, what, data->chainarg); 188 if (error) 189 return error; 190 } 191 error = syscall_deregister(data->offset, &data->old_sysent); 192 return (error); 193 default: 194 if (data->chainevh) 195 return (data->chainevh(mod, what, data->chainarg)); 196 return (EOPNOTSUPP); 197 } 198 199 /* NOTREACHED */ 200 } 201 202 int 203 syscall_helper_register(struct syscall_helper_data *sd, int flags) 204 { 205 struct syscall_helper_data *sd1; 206 int error; 207 208 for (sd1 = sd; sd1->syscall_no != NO_SYSCALL; sd1++) { 209 error = syscall_register(&sd1->syscall_no, &sd1->new_sysent, 210 &sd1->old_sysent, flags); 211 if (error != 0) { 212 syscall_helper_unregister(sd); 213 return (error); 214 } 215 sd1->registered = 1; 216 } 217 return (0); 218 } 219 220 int 221 syscall_helper_unregister(struct syscall_helper_data *sd) 222 { 223 struct syscall_helper_data *sd1; 224 225 for (sd1 = sd; sd1->registered != 0; sd1++) { 226 syscall_deregister(&sd1->syscall_no, &sd1->old_sysent); 227 sd1->registered = 0; 228 } 229 return (0); 230 } 231