03e161fdb1
- If we fail to register the system call during MOD_LOAD, then note that so that we don't try to deregister it or invoke the chained event handler during the subsequent MOD_UNLOAD event. Doing the deregister when the register failed could result in trashing system call entries. - Add a SI_SUB_SYSCALLS just before starting up init and use that to register syscall modules instead of SI_SUB_DRIVERS. Registering system calls as late as possible increases the chances that any other module event handlers or SYSINITs in a module are executed to initialize the data in a kld before a syscall dependent on that data is able to be invoked. MFC after: 3 days
138 lines
4.4 KiB
C
138 lines
4.4 KiB
C
/*-
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* Copyright (c) 1999 Assar Westerlund
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* All rights reserved.
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*
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* Redistribution and use in source and binary forms, with or without
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* modification, are permitted provided that the following conditions
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* are met:
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* 1. Redistributions of source code must retain the above copyright
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* notice, this list of conditions and the following disclaimer.
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* 2. Redistributions in binary form must reproduce the above copyright
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* notice, this list of conditions and the following disclaimer in the
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* documentation and/or other materials provided with the distribution.
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*
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* THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
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* ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
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* IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
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* ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
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* FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
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* DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
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* OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
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* HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
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* LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
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* OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
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* SUCH DAMAGE.
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*/
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#include <sys/cdefs.h>
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__FBSDID("$FreeBSD$");
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#include <sys/param.h>
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#include <sys/sysproto.h>
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#include <sys/sysent.h>
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#include <sys/syscall.h>
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#include <sys/lock.h>
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#include <sys/mutex.h>
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#include <sys/sx.h>
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#include <sys/module.h>
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/*
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* Acts like "nosys" but can be identified in sysent for dynamic call
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* number assignment for a limited number of calls.
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*
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* Place holder for system call slots reserved for loadable modules.
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*/
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int
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lkmnosys(struct thread *td, struct nosys_args *args)
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{
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return(nosys(td, args));
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}
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int
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lkmressys(struct thread *td, struct nosys_args *args)
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{
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return(nosys(td, args));
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}
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int
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syscall_register(int *offset, struct sysent *new_sysent,
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struct sysent *old_sysent)
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{
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if (*offset == NO_SYSCALL) {
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int i;
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for (i = 1; i < SYS_MAXSYSCALL; ++i)
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if (sysent[i].sy_call == (sy_call_t *)lkmnosys)
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break;
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if (i == SYS_MAXSYSCALL)
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return ENFILE;
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*offset = i;
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} else if (*offset < 0 || *offset >= SYS_MAXSYSCALL)
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return EINVAL;
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else if (sysent[*offset].sy_call != (sy_call_t *)lkmnosys &&
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sysent[*offset].sy_call != (sy_call_t *)lkmressys)
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return EEXIST;
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*old_sysent = sysent[*offset];
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sysent[*offset] = *new_sysent;
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return 0;
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}
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int
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syscall_deregister(int *offset, struct sysent *old_sysent)
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{
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if (*offset)
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sysent[*offset] = *old_sysent;
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return 0;
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}
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int
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syscall_module_handler(struct module *mod, int what, void *arg)
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{
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struct syscall_module_data *data = (struct syscall_module_data*)arg;
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modspecific_t ms;
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int error;
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switch (what) {
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case MOD_LOAD :
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error = syscall_register(data->offset, data->new_sysent,
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&data->old_sysent);
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if (error) {
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/* Leave a mark so we know to safely unload below. */
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data->offset = NULL;
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return error;
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}
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ms.intval = *data->offset;
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MOD_XLOCK;
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module_setspecific(mod, &ms);
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MOD_XUNLOCK;
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if (data->chainevh)
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error = data->chainevh(mod, what, data->chainarg);
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return error;
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case MOD_UNLOAD :
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/*
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* MOD_LOAD failed, so just return without calling the
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* chained handler since we didn't pass along the MOD_LOAD
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* event.
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*/
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if (data->offset == NULL)
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return (0);
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if (data->chainevh) {
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error = data->chainevh(mod, what, data->chainarg);
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if (error)
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return error;
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}
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error = syscall_deregister(data->offset, &data->old_sysent);
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return error;
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default :
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return EOPNOTSUPP;
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}
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if (data->chainevh)
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return data->chainevh(mod, what, data->chainarg);
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else
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return 0;
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}
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