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/*-
* SPDX-License-Identifier: BSD-2-Clause-FreeBSD
*
* Copyright (c) 1999 Assar Westerlund
* All rights reserved.
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions
* are met:
* 1. Redistributions of source code must retain the above copyright
* notice, this list of conditions and the following disclaimer.
* 2. Redistributions in binary form must reproduce the above copyright
* notice, this list of conditions and the following disclaimer in the
* documentation and/or other materials provided with the distribution.
*
* THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
* ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
* IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
* ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
* FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
* DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
* OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
* HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
* LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
* OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
* SUCH DAMAGE.
*/
#include <sys/cdefs.h>
__FBSDID("$FreeBSD$");
#include <sys/param.h>
#include <sys/kernel.h>
#include <sys/lock.h>
#include <sys/module.h>
#include <sys/mutex.h>
#include <sys/proc.h>
#include <sys/resourcevar.h>
#include <sys/sx.h>
#include <sys/syscall.h>
#include <sys/sysent.h>
#include <sys/sysproto.h>
#include <sys/systm.h>
#include <machine/atomic.h>
/*
* Acts like "nosys" but can be identified in sysent for dynamic call
* number assignment for a limited number of calls.
*
* Place holder for system call slots reserved for loadable modules.
*/
int
lkmnosys(struct thread *td, struct nosys_args *args)
{
return (nosys(td, args));
}
int
lkmressys(struct thread *td, struct nosys_args *args)
{
return (nosys(td, args));
}
static void
syscall_thread_drain(struct sysent *se)
{
u_int32_t cnt, oldcnt;
do {
oldcnt = se->sy_thrcnt;
KASSERT((oldcnt & SY_THR_STATIC) == 0,
("drain on static syscall"));
cnt = oldcnt | SY_THR_DRAINING;
} while (atomic_cmpset_acq_32(&se->sy_thrcnt, oldcnt, cnt) == 0);
while (atomic_cmpset_32(&se->sy_thrcnt, SY_THR_DRAINING,
SY_THR_ABSENT) == 0)
pause("scdrn", hz/2);
}
int
syscall_thread_enter(struct thread *td, struct sysent *se)
{
u_int32_t cnt, oldcnt;
KASSERT((se->sy_thrcnt & SY_THR_STATIC) == 0,
("%s: not a static syscall", __func__));
do {
oldcnt = se->sy_thrcnt;
if ((oldcnt & (SY_THR_DRAINING | SY_THR_ABSENT)) != 0)
return (ENOSYS);
cnt = oldcnt + SY_THR_INCR;
} while (atomic_cmpset_acq_32(&se->sy_thrcnt, oldcnt, cnt) == 0);
return (0);
}
void
syscall_thread_exit(struct thread *td, struct sysent *se)
{
u_int32_t cnt, oldcnt;
KASSERT((se->sy_thrcnt & SY_THR_STATIC) == 0,
("%s: not a static syscall", __func__));
do {
oldcnt = se->sy_thrcnt;
cnt = oldcnt - SY_THR_INCR;
} while (atomic_cmpset_rel_32(&se->sy_thrcnt, oldcnt, cnt) == 0);
}
int
kern_syscall_register(struct sysent *sysents, int *offset,
struct sysent *new_sysent, struct sysent *old_sysent, int flags)
{
int i;
if ((flags & ~SY_THR_STATIC) != 0)
return (EINVAL);
if (*offset == NO_SYSCALL) {
for (i = 1; i < SYS_MAXSYSCALL; ++i)
if (sysents[i].sy_call == (sy_call_t *)lkmnosys)
break;
if (i == SYS_MAXSYSCALL)
return (ENFILE);
*offset = i;
} else if (*offset < 0 || *offset >= SYS_MAXSYSCALL) {
return (EINVAL);
} else if (sysents[*offset].sy_call != (sy_call_t *)lkmnosys &&
sysents[*offset].sy_call != (sy_call_t *)lkmressys) {
KASSERT(sysents[*offset].sy_call != NULL,
("undefined syscall %d", *offset));
return (EEXIST);
}
KASSERT(sysents[*offset].sy_thrcnt == SY_THR_ABSENT,
("dynamic syscall is not protected"));
*old_sysent = sysents[*offset];
new_sysent->sy_thrcnt = SY_THR_ABSENT;
sysents[*offset] = *new_sysent;
atomic_store_rel_32(&sysents[*offset].sy_thrcnt, flags);
return (0);
}
int
kern_syscall_deregister(struct sysent *sysents, int offset,
const struct sysent *old_sysent)
{
struct sysent *se;
if (offset == 0)
return (0); /* XXX? */
se = &sysents[offset];
if ((se->sy_thrcnt & SY_THR_STATIC) != 0)
return (EINVAL);
syscall_thread_drain(se);
sysents[offset] = *old_sysent;
return (0);
}
int
syscall_module_handler(struct module *mod, int what, void *arg)
{
return (kern_syscall_module_handler(sysent, mod, what, arg));
}
int
kern_syscall_module_handler(struct sysent *sysents, struct module *mod,
int what, void *arg)
{
struct syscall_module_data *data = arg;
modspecific_t ms;
int error;
switch (what) {
case MOD_LOAD:
error = kern_syscall_register(sysents, data->offset,
data->new_sysent, &data->old_sysent, data->flags);
if (error) {
/* Leave a mark so we know to safely unload below. */
data->offset = NULL;
return (error);
}
ms.intval = *data->offset;
MOD_XLOCK;
module_setspecific(mod, &ms);
MOD_XUNLOCK;
if (data->chainevh)
error = data->chainevh(mod, what, data->chainarg);
return (error);
case MOD_UNLOAD:
/*
* MOD_LOAD failed, so just return without calling the
* chained handler since we didn't pass along the MOD_LOAD
* event.
*/
if (data->offset == NULL)
return (0);
if (data->chainevh) {
error = data->chainevh(mod, what, data->chainarg);
if (error)
return error;
}
error = kern_syscall_deregister(sysents, *data->offset,
&data->old_sysent);
return (error);
default:
if (data->chainevh)
return (data->chainevh(mod, what, data->chainarg));
return (EOPNOTSUPP);
}
/* NOTREACHED */
}
int
syscall_helper_register(struct syscall_helper_data *sd, int flags)
{
return (kern_syscall_helper_register(sysent, sd, flags));
}
int
kern_syscall_helper_register(struct sysent *sysents,
struct syscall_helper_data *sd, int flags)
{
struct syscall_helper_data *sd1;
int error;
for (sd1 = sd; sd1->syscall_no != NO_SYSCALL; sd1++) {
error = kern_syscall_register(sysents, &sd1->syscall_no,
&sd1->new_sysent, &sd1->old_sysent, flags);
if (error != 0) {
kern_syscall_helper_unregister(sysents, sd);
return (error);
}
sd1->registered = 1;
}
return (0);
}
int
syscall_helper_unregister(struct syscall_helper_data *sd)
{
return (kern_syscall_helper_unregister(sysent, sd));
}
int
kern_syscall_helper_unregister(struct sysent *sysents,
struct syscall_helper_data *sd)
{
struct syscall_helper_data *sd1;
for (sd1 = sd; sd1->registered != 0; sd1++) {
kern_syscall_deregister(sysents, sd1->syscall_no,
&sd1->old_sysent);
sd1->registered = 0;
}
return (0);
}
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