257 lines
6.5 KiB
C
257 lines
6.5 KiB
C
/*-
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* SPDX-License-Identifier: BSD-2-Clause-FreeBSD
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*
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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/kernel.h>
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#include <sys/lock.h>
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#include <sys/module.h>
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#include <sys/mutex.h>
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#include <sys/proc.h>
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#include <sys/resourcevar.h>
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#include <sys/sx.h>
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#include <sys/syscall.h>
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#include <sys/sysent.h>
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#include <sys/sysproto.h>
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#include <sys/systm.h>
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#include <machine/atomic.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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static void
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syscall_thread_drain(struct sysent *se)
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{
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u_int32_t cnt, oldcnt;
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do {
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oldcnt = se->sy_thrcnt;
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KASSERT((oldcnt & SY_THR_STATIC) == 0,
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("drain on static syscall"));
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cnt = oldcnt | SY_THR_DRAINING;
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} while (atomic_cmpset_acq_32(&se->sy_thrcnt, oldcnt, cnt) == 0);
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while (atomic_cmpset_32(&se->sy_thrcnt, SY_THR_DRAINING,
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SY_THR_ABSENT) == 0)
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pause("scdrn", hz/2);
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}
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int
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_syscall_thread_enter(struct thread *td, struct sysent *se)
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{
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u_int32_t cnt, oldcnt;
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do {
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oldcnt = se->sy_thrcnt;
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if ((oldcnt & (SY_THR_DRAINING | SY_THR_ABSENT)) != 0)
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return (ENOSYS);
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cnt = oldcnt + SY_THR_INCR;
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} while (atomic_cmpset_acq_32(&se->sy_thrcnt, oldcnt, cnt) == 0);
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return (0);
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}
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void
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_syscall_thread_exit(struct thread *td, struct sysent *se)
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{
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u_int32_t cnt, oldcnt;
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do {
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oldcnt = se->sy_thrcnt;
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cnt = oldcnt - SY_THR_INCR;
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} while (atomic_cmpset_rel_32(&se->sy_thrcnt, oldcnt, cnt) == 0);
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}
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int
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kern_syscall_register(struct sysent *sysents, int *offset,
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struct sysent *new_sysent, struct sysent *old_sysent, int flags)
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{
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int i;
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if ((flags & ~SY_THR_STATIC) != 0)
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return (EINVAL);
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if (*offset == NO_SYSCALL) {
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for (i = 1; i < SYS_MAXSYSCALL; ++i)
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if (sysents[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 (sysents[*offset].sy_call != (sy_call_t *)lkmnosys &&
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sysents[*offset].sy_call != (sy_call_t *)lkmressys)
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return (EEXIST);
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KASSERT(sysents[*offset].sy_thrcnt == SY_THR_ABSENT,
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("dynamic syscall is not protected"));
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*old_sysent = sysents[*offset];
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new_sysent->sy_thrcnt = SY_THR_ABSENT;
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sysents[*offset] = *new_sysent;
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atomic_store_rel_32(&sysents[*offset].sy_thrcnt, flags);
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return (0);
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}
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int
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kern_syscall_deregister(struct sysent *sysents, int offset,
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const struct sysent *old_sysent)
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{
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struct sysent *se;
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if (offset == 0)
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return (0); /* XXX? */
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se = &sysents[offset];
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if ((se->sy_thrcnt & SY_THR_STATIC) != 0)
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return (EINVAL);
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syscall_thread_drain(se);
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sysents[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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return (kern_syscall_module_handler(sysent, mod, what, arg));
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}
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int
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kern_syscall_module_handler(struct sysent *sysents, struct module *mod,
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int what, void *arg)
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{
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struct syscall_module_data *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 = kern_syscall_register(sysents, data->offset,
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data->new_sysent, &data->old_sysent, data->flags);
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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 = kern_syscall_deregister(sysents, *data->offset,
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&data->old_sysent);
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return (error);
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default:
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if (data->chainevh)
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return (data->chainevh(mod, what, data->chainarg));
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return (EOPNOTSUPP);
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}
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/* NOTREACHED */
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}
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int
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syscall_helper_register(struct syscall_helper_data *sd, int flags)
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{
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return (kern_syscall_helper_register(sysent, sd, flags));
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}
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int
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kern_syscall_helper_register(struct sysent *sysents,
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struct syscall_helper_data *sd, int flags)
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{
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struct syscall_helper_data *sd1;
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int error;
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for (sd1 = sd; sd1->syscall_no != NO_SYSCALL; sd1++) {
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error = kern_syscall_register(sysents, &sd1->syscall_no,
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&sd1->new_sysent, &sd1->old_sysent, flags);
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if (error != 0) {
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kern_syscall_helper_unregister(sysents, sd);
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return (error);
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}
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sd1->registered = 1;
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}
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return (0);
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}
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int
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syscall_helper_unregister(struct syscall_helper_data *sd)
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{
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return (kern_syscall_helper_unregister(sysent, sd));
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}
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int
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kern_syscall_helper_unregister(struct sysent *sysents,
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struct syscall_helper_data *sd)
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{
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struct syscall_helper_data *sd1;
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for (sd1 = sd; sd1->registered != 0; sd1++) {
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kern_syscall_deregister(sysents, sd1->syscall_no,
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&sd1->old_sysent);
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sd1->registered = 0;
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}
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return (0);
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}
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