2 * Copyright (c) 2002 Alfred Perlstein <alfred@FreeBSD.org>
3 * Copyright (c) 2003-2005 SPARTA, Inc.
4 * Copyright (c) 2005 Robert N. M. Watson
7 * This software was developed for the FreeBSD Project in part by Network
8 * Associates Laboratories, the Security Research Division of Network
9 * Associates, Inc. under DARPA/SPAWAR contract N66001-01-C-8035 ("CBOSS"),
10 * as part of the DARPA CHATS research program.
12 * Redistribution and use in source and binary forms, with or without
13 * modification, are permitted provided that the following conditions
15 * 1. Redistributions of source code must retain the above copyright
16 * notice, this list of conditions and the following disclaimer.
17 * 2. Redistributions in binary form must reproduce the above copyright
18 * notice, this list of conditions and the following disclaimer in the
19 * documentation and/or other materials provided with the distribution.
21 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
22 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
23 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
24 * ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
25 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
26 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
27 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
28 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
29 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
30 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
34 #include <sys/cdefs.h>
35 __FBSDID("$FreeBSD$");
37 #include "opt_posix.h"
39 #include <sys/param.h>
40 #include <sys/condvar.h>
41 #include <sys/fcntl.h>
43 #include <sys/filedesc.h>
44 #include <sys/fnv_hash.h>
45 #include <sys/kernel.h>
48 #include <sys/malloc.h>
49 #include <sys/module.h>
50 #include <sys/mutex.h>
53 #include <sys/posix4.h>
54 #include <sys/semaphore.h>
55 #include <sys/_semaphore.h>
57 #include <sys/syscall.h>
58 #include <sys/syscallsubr.h>
59 #include <sys/sysctl.h>
60 #include <sys/sysent.h>
61 #include <sys/sysproto.h>
62 #include <sys/systm.h>
64 #include <sys/vnode.h>
66 #include <security/mac/mac_framework.h>
73 * - Replace global sem_lock with mtx_pool locks?
74 * - Add a MAC check_create() hook for creating new named semaphores.
82 #define DP(x) printf x
91 LIST_ENTRY(ksem_mapping) km_link;
94 static MALLOC_DEFINE(M_KSEM, "ksem", "semaphore file descriptor");
95 static LIST_HEAD(, ksem_mapping) *ksem_dictionary;
96 static struct sx ksem_dict_lock;
97 static struct mtx ksem_count_lock;
98 static struct mtx sem_lock;
99 static u_long ksem_hash;
100 static int ksem_dead;
102 #define KSEM_HASH(fnv) (&ksem_dictionary[(fnv) & ksem_hash])
104 static int nsems = 0;
105 SYSCTL_DECL(_p1003_1b);
106 SYSCTL_INT(_p1003_1b, OID_AUTO, nsems, CTLFLAG_RD, &nsems, 0,
107 "Number of active kernel POSIX semaphores");
109 static int kern_sem_wait(struct thread *td, semid_t id, int tryflag,
110 struct timespec *abstime);
111 static int ksem_access(struct ksem *ks, struct ucred *ucred);
112 static struct ksem *ksem_alloc(struct ucred *ucred, mode_t mode,
114 static int ksem_create(struct thread *td, const char *path,
115 semid_t *semidp, mode_t mode, unsigned int value,
117 static void ksem_drop(struct ksem *ks);
118 static int ksem_get(struct thread *td, semid_t id, struct file **fpp);
119 static struct ksem *ksem_hold(struct ksem *ks);
120 static void ksem_insert(char *path, Fnv32_t fnv, struct ksem *ks);
121 static struct ksem *ksem_lookup(char *path, Fnv32_t fnv);
122 static void ksem_module_destroy(void);
123 static int ksem_module_init(void);
124 static int ksem_remove(char *path, Fnv32_t fnv, struct ucred *ucred);
125 static int sem_modload(struct module *module, int cmd, void *arg);
127 static fo_rdwr_t ksem_read;
128 static fo_rdwr_t ksem_write;
129 static fo_truncate_t ksem_truncate;
130 static fo_ioctl_t ksem_ioctl;
131 static fo_poll_t ksem_poll;
132 static fo_kqfilter_t ksem_kqfilter;
133 static fo_stat_t ksem_stat;
134 static fo_close_t ksem_closef;
136 /* File descriptor operations. */
137 static struct fileops ksem_ops = {
138 .fo_read = ksem_read,
139 .fo_write = ksem_write,
140 .fo_truncate = ksem_truncate,
141 .fo_ioctl = ksem_ioctl,
142 .fo_poll = ksem_poll,
143 .fo_kqfilter = ksem_kqfilter,
144 .fo_stat = ksem_stat,
145 .fo_close = ksem_closef,
146 .fo_flags = DFLAG_PASSABLE
149 FEATURE(posix_sem, "POSIX semaphores");
152 ksem_read(struct file *fp, struct uio *uio, struct ucred *active_cred,
153 int flags, struct thread *td)
160 ksem_write(struct file *fp, struct uio *uio, struct ucred *active_cred,
161 int flags, struct thread *td)
168 ksem_truncate(struct file *fp, off_t length, struct ucred *active_cred,
176 ksem_ioctl(struct file *fp, u_long com, void *data,
177 struct ucred *active_cred, struct thread *td)
184 ksem_poll(struct file *fp, int events, struct ucred *active_cred,
192 ksem_kqfilter(struct file *fp, struct knote *kn)
199 ksem_stat(struct file *fp, struct stat *sb, struct ucred *active_cred,
210 error = mac_posixsem_check_stat(active_cred, fp->f_cred, ks);
216 * Attempt to return sanish values for fstat() on a semaphore
219 bzero(sb, sizeof(*sb));
220 sb->st_mode = S_IFREG | ks->ks_mode; /* XXX */
222 sb->st_atimespec = ks->ks_atime;
223 sb->st_ctimespec = ks->ks_ctime;
224 sb->st_mtimespec = ks->ks_mtime;
225 sb->st_birthtimespec = ks->ks_birthtime;
226 sb->st_uid = ks->ks_uid;
227 sb->st_gid = ks->ks_gid;
233 ksem_closef(struct file *fp, struct thread *td)
245 * ksem object management including creation and reference counting
249 ksem_alloc(struct ucred *ucred, mode_t mode, unsigned int value)
253 mtx_lock(&ksem_count_lock);
254 if (nsems == p31b_getcfg(CTL_P1003_1B_SEM_NSEMS_MAX) || ksem_dead) {
255 mtx_unlock(&ksem_count_lock);
259 mtx_unlock(&ksem_count_lock);
260 ks = malloc(sizeof(*ks), M_KSEM, M_WAITOK | M_ZERO);
261 ks->ks_uid = ucred->cr_uid;
262 ks->ks_gid = ucred->cr_gid;
264 ks->ks_value = value;
265 cv_init(&ks->ks_cv, "ksem");
266 vfs_timestamp(&ks->ks_birthtime);
267 ks->ks_atime = ks->ks_mtime = ks->ks_ctime = ks->ks_birthtime;
268 refcount_init(&ks->ks_ref, 1);
270 mac_posixsem_init(ks);
271 mac_posixsem_create(ucred, ks);
278 ksem_hold(struct ksem *ks)
281 refcount_acquire(&ks->ks_ref);
286 ksem_drop(struct ksem *ks)
289 if (refcount_release(&ks->ks_ref)) {
291 mac_posixsem_destroy(ks);
293 cv_destroy(&ks->ks_cv);
295 mtx_lock(&ksem_count_lock);
297 mtx_unlock(&ksem_count_lock);
302 * Determine if the credentials have sufficient permissions for read
306 ksem_access(struct ksem *ks, struct ucred *ucred)
310 error = vaccess(VREG, ks->ks_mode, ks->ks_uid, ks->ks_gid,
311 VREAD | VWRITE, ucred, NULL);
313 error = priv_check_cred(ucred, PRIV_SEM_WRITE, 0);
318 * Dictionary management. We maintain an in-kernel dictionary to map
319 * paths to semaphore objects. We use the FNV hash on the path to
320 * store the mappings in a hash table.
323 ksem_lookup(char *path, Fnv32_t fnv)
325 struct ksem_mapping *map;
327 LIST_FOREACH(map, KSEM_HASH(fnv), km_link) {
328 if (map->km_fnv != fnv)
330 if (strcmp(map->km_path, path) == 0)
331 return (map->km_ksem);
338 ksem_insert(char *path, Fnv32_t fnv, struct ksem *ks)
340 struct ksem_mapping *map;
342 map = malloc(sizeof(struct ksem_mapping), M_KSEM, M_WAITOK);
345 map->km_ksem = ksem_hold(ks);
346 LIST_INSERT_HEAD(KSEM_HASH(fnv), map, km_link);
350 ksem_remove(char *path, Fnv32_t fnv, struct ucred *ucred)
352 struct ksem_mapping *map;
355 LIST_FOREACH(map, KSEM_HASH(fnv), km_link) {
356 if (map->km_fnv != fnv)
358 if (strcmp(map->km_path, path) == 0) {
360 error = mac_posixsem_check_unlink(ucred, map->km_ksem);
364 error = ksem_access(map->km_ksem, ucred);
367 LIST_REMOVE(map, km_link);
368 ksem_drop(map->km_ksem);
369 free(map->km_path, M_KSEM);
378 /* Other helper routines. */
380 ksem_create(struct thread *td, const char *name, semid_t *semidp, mode_t mode,
381 unsigned int value, int flags)
383 struct filedesc *fdp;
391 if (value > SEM_VALUE_MAX)
394 fdp = td->td_proc->p_fd;
395 mode = (mode & ~fdp->fd_cmask) & ACCESSPERMS;
396 error = falloc(td, &fp, &fd);
404 * Go ahead and copyout the file descriptor now. This is a bit
405 * premature, but it is a lot easier to handle errors as opposed
406 * to later when we've possibly created a new semaphore, etc.
409 error = copyout(&semid, semidp, sizeof(semid));
411 fdclose(fdp, fp, fd, td);
417 /* Create an anonymous semaphore. */
418 ks = ksem_alloc(td->td_ucred, mode, value);
422 ks->ks_flags |= KS_ANONYMOUS;
424 path = malloc(MAXPATHLEN, M_KSEM, M_WAITOK);
425 error = copyinstr(name, path, MAXPATHLEN, NULL);
427 /* Require paths to start with a '/' character. */
428 if (error == 0 && path[0] != '/')
431 fdclose(fdp, fp, fd, td);
437 fnv = fnv_32_str(path, FNV1_32_INIT);
438 sx_xlock(&ksem_dict_lock);
439 ks = ksem_lookup(path, fnv);
441 /* Object does not exist, create it if requested. */
442 if (flags & O_CREAT) {
443 ks = ksem_alloc(td->td_ucred, mode, value);
447 ksem_insert(path, fnv, ks);
454 * Object already exists, obtain a new
455 * reference if requested and permitted.
457 if ((flags & (O_CREAT | O_EXCL)) ==
462 error = mac_posixsem_check_open(td->td_ucred,
466 error = ksem_access(ks, td->td_ucred);
475 sx_xunlock(&ksem_dict_lock);
481 KASSERT(ks == NULL, ("ksem_create error with a ksem"));
482 fdclose(fdp, fp, fd, td);
486 KASSERT(ks != NULL, ("ksem_create w/o a ksem"));
488 finit(fp, FREAD | FWRITE, DTYPE_SEM, ks, &ksem_ops);
491 if (fdp->fd_ofiles[fd] == fp)
492 fdp->fd_ofileflags[fd] |= UF_EXCLOSE;
493 FILEDESC_XUNLOCK(fdp);
500 ksem_get(struct thread *td, semid_t id, struct file **fpp)
506 error = fget(td, id, &fp);
509 if (fp->f_type != DTYPE_SEM) {
514 if (ks->ks_flags & KS_DEAD) {
523 #ifndef _SYS_SYSPROTO_H_
524 struct ksem_init_args {
530 ksem_init(struct thread *td, struct ksem_init_args *uap)
533 return (ksem_create(td, NULL, uap->idp, S_IRWXU | S_IRWXG, uap->value,
537 #ifndef _SYS_SYSPROTO_H_
538 struct ksem_open_args {
547 ksem_open(struct thread *td, struct ksem_open_args *uap)
550 DP((">>> ksem_open start, pid=%d\n", (int)td->td_proc->p_pid));
552 if ((uap->oflag & ~(O_CREAT | O_EXCL)) != 0)
554 return (ksem_create(td, uap->name, uap->idp, uap->mode, uap->value,
558 #ifndef _SYS_SYSPROTO_H_
559 struct ksem_unlink_args {
564 ksem_unlink(struct thread *td, struct ksem_unlink_args *uap)
570 path = malloc(MAXPATHLEN, M_TEMP, M_WAITOK);
571 error = copyinstr(uap->name, path, MAXPATHLEN, NULL);
577 fnv = fnv_32_str(path, FNV1_32_INIT);
578 sx_xlock(&ksem_dict_lock);
579 error = ksem_remove(path, fnv, td->td_ucred);
580 sx_xunlock(&ksem_dict_lock);
586 #ifndef _SYS_SYSPROTO_H_
587 struct ksem_close_args {
592 ksem_close(struct thread *td, struct ksem_close_args *uap)
598 error = ksem_get(td, uap->id, &fp);
602 if (ks->ks_flags & KS_ANONYMOUS) {
606 error = kern_close(td, uap->id);
611 #ifndef _SYS_SYSPROTO_H_
612 struct ksem_post_args {
617 ksem_post(struct thread *td, struct ksem_post_args *uap)
623 error = ksem_get(td, uap->id, &fp);
630 error = mac_posixsem_check_post(td->td_ucred, fp->f_cred, ks);
634 if (ks->ks_value == SEM_VALUE_MAX) {
639 if (ks->ks_waiters > 0)
640 cv_signal(&ks->ks_cv);
642 vfs_timestamp(&ks->ks_ctime);
644 mtx_unlock(&sem_lock);
649 #ifndef _SYS_SYSPROTO_H_
650 struct ksem_wait_args {
655 ksem_wait(struct thread *td, struct ksem_wait_args *uap)
658 return (kern_sem_wait(td, uap->id, 0, NULL));
661 #ifndef _SYS_SYSPROTO_H_
662 struct ksem_timedwait_args {
664 const struct timespec *abstime;
668 ksem_timedwait(struct thread *td, struct ksem_timedwait_args *uap)
670 struct timespec abstime;
675 * We allow a null timespec (wait forever).
677 if (uap->abstime == NULL)
680 error = copyin(uap->abstime, &abstime, sizeof(abstime));
683 if (abstime.tv_nsec >= 1000000000 || abstime.tv_nsec < 0)
687 return (kern_sem_wait(td, uap->id, 0, ts));
690 #ifndef _SYS_SYSPROTO_H_
691 struct ksem_trywait_args {
696 ksem_trywait(struct thread *td, struct ksem_trywait_args *uap)
699 return (kern_sem_wait(td, uap->id, 1, NULL));
703 kern_sem_wait(struct thread *td, semid_t id, int tryflag,
704 struct timespec *abstime)
706 struct timespec ts1, ts2;
712 DP((">>> kern_sem_wait entered! pid=%d\n", (int)td->td_proc->p_pid));
713 error = ksem_get(td, id, &fp);
718 DP((">>> kern_sem_wait critical section entered! pid=%d\n",
719 (int)td->td_proc->p_pid));
721 error = mac_posixsem_check_wait(td->td_ucred, fp->f_cred, ks);
723 DP(("kern_sem_wait mac failed\n"));
727 DP(("kern_sem_wait value = %d, tryflag %d\n", ks->ks_value, tryflag));
728 vfs_timestamp(&ks->ks_atime);
729 while (ks->ks_value == 0) {
733 else if (abstime == NULL)
734 error = cv_wait_sig(&ks->ks_cv, &sem_lock);
739 timespecsub(&ts1, &ts2);
740 TIMESPEC_TO_TIMEVAL(&tv, &ts1);
745 error = cv_timedwait_sig(&ks->ks_cv,
746 &sem_lock, tvtohz(&tv));
747 if (error != EWOULDBLOCK)
756 DP(("kern_sem_wait value post-decrement = %d\n", ks->ks_value));
759 mtx_unlock(&sem_lock);
761 DP(("<<< kern_sem_wait leaving, pid=%d, error = %d\n",
762 (int)td->td_proc->p_pid, error));
766 #ifndef _SYS_SYSPROTO_H_
767 struct ksem_getvalue_args {
773 ksem_getvalue(struct thread *td, struct ksem_getvalue_args *uap)
779 error = ksem_get(td, uap->id, &fp);
786 error = mac_posixsem_check_getvalue(td->td_ucred, fp->f_cred, ks);
788 mtx_unlock(&sem_lock);
794 vfs_timestamp(&ks->ks_atime);
795 mtx_unlock(&sem_lock);
797 error = copyout(&val, uap->val, sizeof(val));
801 #ifndef _SYS_SYSPROTO_H_
802 struct ksem_destroy_args {
807 ksem_destroy(struct thread *td, struct ksem_destroy_args *uap)
813 error = ksem_get(td, uap->id, &fp);
817 if (!(ks->ks_flags & KS_ANONYMOUS)) {
822 if (ks->ks_waiters != 0) {
823 mtx_unlock(&sem_lock);
827 ks->ks_flags |= KS_DEAD;
828 mtx_unlock(&sem_lock);
830 error = kern_close(td, uap->id);
836 #define SYSCALL_DATA(syscallname) \
837 static int syscallname##_syscall = SYS_##syscallname; \
838 static int syscallname##_registered; \
839 static struct sysent syscallname##_old_sysent; \
840 MAKE_SYSENT(syscallname);
842 #define SYSCALL_REGISTER(syscallname) do { \
843 error = syscall_register(& syscallname##_syscall, \
844 & syscallname##_sysent, & syscallname##_old_sysent); \
847 syscallname##_registered = 1; \
850 #define SYSCALL_DEREGISTER(syscallname) do { \
851 if (syscallname##_registered) { \
852 syscallname##_registered = 0; \
853 syscall_deregister(& syscallname##_syscall, \
854 & syscallname##_old_sysent); \
858 SYSCALL_DATA(ksem_init);
859 SYSCALL_DATA(ksem_open);
860 SYSCALL_DATA(ksem_unlink);
861 SYSCALL_DATA(ksem_close);
862 SYSCALL_DATA(ksem_post);
863 SYSCALL_DATA(ksem_wait);
864 SYSCALL_DATA(ksem_timedwait);
865 SYSCALL_DATA(ksem_trywait);
866 SYSCALL_DATA(ksem_getvalue);
867 SYSCALL_DATA(ksem_destroy);
870 ksem_module_init(void)
874 mtx_init(&sem_lock, "sem", NULL, MTX_DEF);
875 mtx_init(&ksem_count_lock, "ksem count", NULL, MTX_DEF);
876 sx_init(&ksem_dict_lock, "ksem dictionary");
877 ksem_dictionary = hashinit(1024, M_KSEM, &ksem_hash);
878 p31b_setcfg(CTL_P1003_1B_SEM_NSEMS_MAX, SEM_MAX);
879 p31b_setcfg(CTL_P1003_1B_SEM_VALUE_MAX, SEM_VALUE_MAX);
881 SYSCALL_REGISTER(ksem_init);
882 SYSCALL_REGISTER(ksem_open);
883 SYSCALL_REGISTER(ksem_unlink);
884 SYSCALL_REGISTER(ksem_close);
885 SYSCALL_REGISTER(ksem_post);
886 SYSCALL_REGISTER(ksem_wait);
887 SYSCALL_REGISTER(ksem_timedwait);
888 SYSCALL_REGISTER(ksem_trywait);
889 SYSCALL_REGISTER(ksem_getvalue);
890 SYSCALL_REGISTER(ksem_destroy);
895 ksem_module_destroy(void)
898 SYSCALL_DEREGISTER(ksem_init);
899 SYSCALL_DEREGISTER(ksem_open);
900 SYSCALL_DEREGISTER(ksem_unlink);
901 SYSCALL_DEREGISTER(ksem_close);
902 SYSCALL_DEREGISTER(ksem_post);
903 SYSCALL_DEREGISTER(ksem_wait);
904 SYSCALL_DEREGISTER(ksem_timedwait);
905 SYSCALL_DEREGISTER(ksem_trywait);
906 SYSCALL_DEREGISTER(ksem_getvalue);
907 SYSCALL_DEREGISTER(ksem_destroy);
909 hashdestroy(ksem_dictionary, M_KSEM, ksem_hash);
910 sx_destroy(&ksem_dict_lock);
911 mtx_destroy(&ksem_count_lock);
912 mtx_destroy(&sem_lock);
916 sem_modload(struct module *module, int cmd, void *arg)
922 error = ksem_module_init();
924 ksem_module_destroy();
928 mtx_lock(&ksem_count_lock);
931 mtx_unlock(&ksem_count_lock);
935 mtx_unlock(&ksem_count_lock);
936 ksem_module_destroy();
948 static moduledata_t sem_mod = {
954 DECLARE_MODULE(sem, sem_mod, SI_SUB_SYSV_SEM, SI_ORDER_FIRST);
955 MODULE_VERSION(sem, 1);