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/sx.h> 35 #include <sys/syscall.h> 36 #include <sys/sysent.h> 37 #include <sys/sysproto.h> 38 #include <sys/systm.h> 39 #include <machine/atomic.h> 40 41 /* 42 * Acts like "nosys" but can be identified in sysent for dynamic call 43 * number assignment for a limited number of calls. 44 * 45 * Place holder for system call slots reserved for loadable modules. 46 */ 47 int 48 lkmnosys(struct thread *td, struct nosys_args *args) 49 { 50 51 return (nosys(td, args)); 52 } 53 54 int 55 lkmressys(struct thread *td, struct nosys_args *args) 56 { 57 58 return (nosys(td, args)); 59 } 60 61 static void 62 syscall_thread_drain(struct sysent *se) 63 { 64 u_int32_t cnt, oldcnt; 65 66 do { 67 oldcnt = se->sy_thrcnt; 68 KASSERT((oldcnt & SY_THR_STATIC) == 0, 69 ("drain on static syscall")); 70 cnt = oldcnt | SY_THR_DRAINING; 71 } while (atomic_cmpset_acq_32(&se->sy_thrcnt, oldcnt, cnt) == 0); 72 while (atomic_cmpset_32(&se->sy_thrcnt, SY_THR_DRAINING, 73 SY_THR_ABSENT) == 0) 74 pause("scdrn", hz/2); 75 } 76 77 int 78 syscall_thread_enter(struct thread *td, struct sysent *se) 79 { 80 u_int32_t cnt, oldcnt; 81 82 do { 83 oldcnt = se->sy_thrcnt; 84 if ((oldcnt & SY_THR_STATIC) != 0) 85 return (0); 86 if ((oldcnt & (SY_THR_DRAINING | SY_THR_ABSENT)) != 0) 87 return (ENOSYS); 88 cnt = oldcnt + SY_THR_INCR; 89 } while (atomic_cmpset_acq_32(&se->sy_thrcnt, oldcnt, cnt) == 0); 90 return (0); 91 } 92 93 void 94 syscall_thread_exit(struct thread *td, struct sysent *se) 95 { 96 u_int32_t cnt, oldcnt; 97 98 do { 99 oldcnt = se->sy_thrcnt; 100 if ((oldcnt & SY_THR_STATIC) != 0) 101 return; 102 cnt = oldcnt - SY_THR_INCR; 103 } while (atomic_cmpset_rel_32(&se->sy_thrcnt, oldcnt, cnt) == 0); 104 } 105 106 int 107 syscall_register(int *offset, struct sysent *new_sysent, 108 struct sysent *old_sysent, int flags) 109 { 110 int i; 111 112 if ((flags & ~SY_THR_STATIC) != 0) 113 return (EINVAL); 114 115 if (*offset == NO_SYSCALL) { 116 for (i = 1; i < SYS_MAXSYSCALL; ++i) 117 if (sysent[i].sy_call == (sy_call_t *)lkmnosys) 118 break; 119 if (i == SYS_MAXSYSCALL) 120 return (ENFILE); 121 *offset = i; 122 } else if (*offset < 0 || *offset >= SYS_MAXSYSCALL) 123 return (EINVAL); 124 else if (sysent[*offset].sy_call != (sy_call_t *)lkmnosys && 125 sysent[*offset].sy_call != (sy_call_t *)lkmressys) 126 return (EEXIST); 127 128 KASSERT(sysent[*offset].sy_thrcnt == SY_THR_ABSENT, 129 ("dynamic syscall is not protected")); 130 *old_sysent = sysent[*offset]; 131 new_sysent->sy_thrcnt = SY_THR_ABSENT; 132 sysent[*offset] = *new_sysent; 133 atomic_store_rel_32(&sysent[*offset].sy_thrcnt, flags); 134 return (0); 135 } 136 137 int 138 syscall_deregister(int *offset, struct sysent *old_sysent) 139 { 140 struct sysent *se; 141 142 if (*offset == 0) 143 return (0); /* XXX? */ 144 145 se = &sysent[*offset]; 146 if ((se->sy_thrcnt & SY_THR_STATIC) != 0) 147 return (EINVAL); 148 syscall_thread_drain(se); 149 sysent[*offset] = *old_sysent; 150 return (0); 151 } 152 153 int 154 syscall_module_handler(struct module *mod, int what, void *arg) 155 { 156 struct syscall_module_data *data = arg; 157 modspecific_t ms; 158 int error; 159 160 switch (what) { 161 case MOD_LOAD: 162 error = syscall_register(data->offset, data->new_sysent, 163 &data->old_sysent, data->flags); 164 if (error) { 165 /* Leave a mark so we know to safely unload below. */ 166 data->offset = NULL; 167 return (error); 168 } 169 ms.intval = *data->offset; 170 MOD_XLOCK; 171 module_setspecific(mod, &ms); 172 MOD_XUNLOCK; 173 if (data->chainevh) 174 error = data->chainevh(mod, what, data->chainarg); 175 return (error); 176 case MOD_UNLOAD: 177 /* 178 * MOD_LOAD failed, so just return without calling the 179 * chained handler since we didn't pass along the MOD_LOAD 180 * event. 181 */ 182 if (data->offset == NULL) 183 return (0); 184 if (data->chainevh) { 185 error = data->chainevh(mod, what, data->chainarg); 186 if (error) 187 return error; 188 } 189 error = syscall_deregister(data->offset, &data->old_sysent); 190 return (error); 191 default: 192 if (data->chainevh) 193 return (data->chainevh(mod, what, data->chainarg)); 194 return (EOPNOTSUPP); 195 } 196 197 /* NOTREACHED */ 198 } 199 200 int 201 syscall_helper_register(struct syscall_helper_data *sd, int flags) 202 { 203 struct syscall_helper_data *sd1; 204 int error; 205 206 for (sd1 = sd; sd1->syscall_no != NO_SYSCALL; sd1++) { 207 error = syscall_register(&sd1->syscall_no, &sd1->new_sysent, 208 &sd1->old_sysent, flags); 209 if (error != 0) { 210 syscall_helper_unregister(sd); 211 return (error); 212 } 213 sd1->registered = 1; 214 } 215 return (0); 216 } 217 218 int 219 syscall_helper_unregister(struct syscall_helper_data *sd) 220 { 221 struct syscall_helper_data *sd1; 222 223 for (sd1 = sd; sd1->registered != 0; sd1++) { 224 syscall_deregister(&sd1->syscall_no, &sd1->old_sysent); 225 sd1->registered = 0; 226 } 227 return (0); 228 } 229