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