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/lock.h> 32 #include <sys/module.h> 33 #include <sys/sx.h> 34 #include <sys/syscall.h> 35 #include <sys/sysent.h> 36 #include <sys/sysproto.h> 37 38 /* 39 * Acts like "nosys" but can be identified in sysent for dynamic call 40 * number assignment for a limited number of calls. 41 * 42 * Place holder for system call slots reserved for loadable modules. 43 */ 44 int 45 lkmnosys(struct thread *td, struct nosys_args *args) 46 { 47 48 return (nosys(td, args)); 49 } 50 51 int 52 lkmressys(struct thread *td, struct nosys_args *args) 53 { 54 55 return (nosys(td, args)); 56 } 57 58 int 59 syscall_register(int *offset, struct sysent *new_sysent, 60 struct sysent *old_sysent) 61 { 62 int i; 63 64 if (*offset == NO_SYSCALL) { 65 for (i = 1; i < SYS_MAXSYSCALL; ++i) 66 if (sysent[i].sy_call == (sy_call_t *)lkmnosys) 67 break; 68 if (i == SYS_MAXSYSCALL) 69 return (ENFILE); 70 *offset = i; 71 } else if (*offset < 0 || *offset >= SYS_MAXSYSCALL) 72 return (EINVAL); 73 else if (sysent[*offset].sy_call != (sy_call_t *)lkmnosys && 74 sysent[*offset].sy_call != (sy_call_t *)lkmressys) 75 return (EEXIST); 76 77 *old_sysent = sysent[*offset]; 78 sysent[*offset] = *new_sysent; 79 return (0); 80 } 81 82 int 83 syscall_deregister(int *offset, struct sysent *old_sysent) 84 { 85 86 if (*offset) 87 sysent[*offset] = *old_sysent; 88 return (0); 89 } 90 91 int 92 syscall_module_handler(struct module *mod, int what, void *arg) 93 { 94 struct syscall_module_data *data = arg; 95 modspecific_t ms; 96 int error; 97 98 switch (what) { 99 case MOD_LOAD: 100 error = syscall_register(data->offset, data->new_sysent, 101 &data->old_sysent); 102 if (error) { 103 /* Leave a mark so we know to safely unload below. */ 104 data->offset = NULL; 105 return (error); 106 } 107 ms.intval = *data->offset; 108 MOD_XLOCK; 109 module_setspecific(mod, &ms); 110 MOD_XUNLOCK; 111 if (data->chainevh) 112 error = data->chainevh(mod, what, data->chainarg); 113 return (error); 114 case MOD_UNLOAD: 115 /* 116 * MOD_LOAD failed, so just return without calling the 117 * chained handler since we didn't pass along the MOD_LOAD 118 * event. 119 */ 120 if (data->offset == NULL) 121 return (0); 122 if (data->chainevh) { 123 error = data->chainevh(mod, what, data->chainarg); 124 if (error) 125 return error; 126 } 127 error = syscall_deregister(data->offset, &data->old_sysent); 128 return (error); 129 default: 130 return EOPNOTSUPP; 131 } 132 133 if (data->chainevh) 134 return (data->chainevh(mod, what, data->chainarg)); 135 else 136 return (0); 137 } 138