diff options
Diffstat (limited to 'sys/kern/kern_syscalls.c')
| -rw-r--r-- | sys/kern/kern_syscalls.c | 220 |
1 files changed, 220 insertions, 0 deletions
diff --git a/sys/kern/kern_syscalls.c b/sys/kern/kern_syscalls.c new file mode 100644 index 0000000..03f6088 --- /dev/null +++ b/sys/kern/kern_syscalls.c @@ -0,0 +1,220 @@ +/*- + * 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/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; + + do { + oldcnt = se->sy_thrcnt; + if ((oldcnt & SY_THR_STATIC) != 0) + return (0); + 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; + + do { + oldcnt = se->sy_thrcnt; + if ((oldcnt & SY_THR_STATIC) != 0) + return; + cnt = oldcnt - SY_THR_INCR; + } while (atomic_cmpset_rel_32(&se->sy_thrcnt, oldcnt, cnt) == 0); +} + +int +syscall_register(int *offset, struct sysent *new_sysent, + struct sysent *old_sysent) +{ + int i; + + if (*offset == NO_SYSCALL) { + for (i = 1; i < SYS_MAXSYSCALL; ++i) + if (sysent[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 (sysent[*offset].sy_call != (sy_call_t *)lkmnosys && + sysent[*offset].sy_call != (sy_call_t *)lkmressys) + return (EEXIST); + + KASSERT(sysent[*offset].sy_thrcnt == SY_THR_ABSENT, + ("dynamic syscall is not protected")); + *old_sysent = sysent[*offset]; + new_sysent->sy_thrcnt = SY_THR_ABSENT; + sysent[*offset] = *new_sysent; + atomic_store_rel_32(&sysent[*offset].sy_thrcnt, 0); + return (0); +} + +int +syscall_deregister(int *offset, struct sysent *old_sysent) +{ + + if (*offset) { + syscall_thread_drain(&sysent[*offset]); + sysent[*offset] = *old_sysent; + } + return (0); +} + +int +syscall_module_handler(struct module *mod, int what, void *arg) +{ + struct syscall_module_data *data = arg; + modspecific_t ms; + int error; + + switch (what) { + case MOD_LOAD: + error = syscall_register(data->offset, data->new_sysent, + &data->old_sysent); + 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 = syscall_deregister(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) +{ + struct syscall_helper_data *sd1; + int error; + + for (sd1 = sd; sd1->syscall_no != NO_SYSCALL; sd1++) { + error = syscall_register(&sd1->syscall_no, &sd1->new_sysent, + &sd1->old_sysent); + if (error != 0) { + syscall_helper_unregister(sd); + return (error); + } + sd1->registered = 1; + } + return (0); +} + +int +syscall_helper_unregister(struct syscall_helper_data *sd) +{ + struct syscall_helper_data *sd1; + + for (sd1 = sd; sd1->registered != 0; sd1++) { + syscall_deregister(&sd1->syscall_no, &sd1->old_sysent); + sd1->registered = 0; + } + return (0); +} |
