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) 109 { 110 int i; 111 112 if (*offset == NO_SYSCALL) { 113 for (i = 1; i < SYS_MAXSYSCALL; ++i) 114 if (sysent[i].sy_call == (sy_call_t *)lkmnosys) 115 break; 116 if (i == SYS_MAXSYSCALL) 117 return (ENFILE); 118 *offset = i; 119 } else if (*offset < 0 || *offset >= SYS_MAXSYSCALL) 120 return (EINVAL); 121 else if (sysent[*offset].sy_call != (sy_call_t *)lkmnosys && 122 sysent[*offset].sy_call != (sy_call_t *)lkmressys) 123 return (EEXIST); 124 125 KASSERT(sysent[*offset].sy_thrcnt == SY_THR_ABSENT, 126 ("dynamic syscall is not protected")); 127 *old_sysent = sysent[*offset]; 128 new_sysent->sy_thrcnt = SY_THR_ABSENT; 129 sysent[*offset] = *new_sysent; 130 atomic_store_rel_32(&sysent[*offset].sy_thrcnt, 0); 131 return (0); 132 } 133 134 int 135 syscall_deregister(int *offset, struct sysent *old_sysent) 136 { 137 138 if (*offset) { 139 syscall_thread_drain(&sysent[*offset]); 140 sysent[*offset] = *old_sysent; 141 } 142 return (0); 143 } 144 145 int 146 syscall_module_handler(struct module *mod, int what, void *arg) 147 { 148 struct syscall_module_data *data = arg; 149 modspecific_t ms; 150 int error; 151 152 switch (what) { 153 case MOD_LOAD: 154 error = syscall_register(data->offset, data->new_sysent, 155 &data->old_sysent); 156 if (error) { 157 /* Leave a mark so we know to safely unload below. */ 158 data->offset = NULL; 159 return (error); 160 } 161 ms.intval = *data->offset; 162 MOD_XLOCK; 163 module_setspecific(mod, &ms); 164 MOD_XUNLOCK; 165 if (data->chainevh) 166 error = data->chainevh(mod, what, data->chainarg); 167 return (error); 168 case MOD_UNLOAD: 169 /* 170 * MOD_LOAD failed, so just return without calling the 171 * chained handler since we didn't pass along the MOD_LOAD 172 * event. 173 */ 174 if (data->offset == NULL) 175 return (0); 176 if (data->chainevh) { 177 error = data->chainevh(mod, what, data->chainarg); 178 if (error) 179 return error; 180 } 181 error = syscall_deregister(data->offset, &data->old_sysent); 182 return (error); 183 default: 184 return EOPNOTSUPP; 185 } 186 187 if (data->chainevh) 188 return (data->chainevh(mod, what, data->chainarg)); 189 else 190 return (0); 191 } 192 193 int 194 syscall_helper_register(struct syscall_helper_data *sd) 195 { 196 struct syscall_helper_data *sd1; 197 int error; 198 199 for (sd1 = sd; sd1->syscall_no != NO_SYSCALL; sd1++) { 200 error = syscall_register(&sd1->syscall_no, &sd1->new_sysent, 201 &sd1->old_sysent); 202 if (error != 0) { 203 syscall_helper_unregister(sd); 204 return (error); 205 } 206 sd1->registered = 1; 207 } 208 return (0); 209 } 210 211 int 212 syscall_helper_unregister(struct syscall_helper_data *sd) 213 { 214 struct syscall_helper_data *sd1; 215 216 for (sd1 = sd; sd1->registered != 0; sd1++) { 217 syscall_deregister(&sd1->syscall_no, &sd1->old_sysent); 218 sd1->registered = 0; 219 } 220 return (0); 221 } 222