The Design and Implementation of the FreeBSD Operating System, Second Edition
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FreeBSD/Linux Kernel Cross Reference
sys/kern/uipc_sem.c

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    1 /*-
    2  * Copyright (c) 2002 Alfred Perlstein <alfred@FreeBSD.org>
    3  * Copyright (c) 2003-2005 SPARTA, Inc.
    4  * Copyright (c) 2005 Robert N. M. Watson
    5  * All rights reserved.
    6  *
    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.
   11  *
   12  * Redistribution and use in source and binary forms, with or without
   13  * modification, are permitted provided that the following conditions
   14  * are met:
   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.
   20  *
   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
   31  * SUCH DAMAGE.
   32  */
   33 
   34 #include <sys/cdefs.h>
   35 __FBSDID("$FreeBSD$");
   36 
   37 #include "opt_compat.h"
   38 #include "opt_posix.h"
   39 
   40 #include <sys/param.h>
   41 #include <sys/capability.h>
   42 #include <sys/condvar.h>
   43 #include <sys/fcntl.h>
   44 #include <sys/file.h>
   45 #include <sys/filedesc.h>
   46 #include <sys/fnv_hash.h>
   47 #include <sys/kernel.h>
   48 #include <sys/ksem.h>
   49 #include <sys/lock.h>
   50 #include <sys/malloc.h>
   51 #include <sys/module.h>
   52 #include <sys/mutex.h>
   53 #include <sys/priv.h>
   54 #include <sys/proc.h>
   55 #include <sys/posix4.h>
   56 #include <sys/_semaphore.h>
   57 #include <sys/stat.h>
   58 #include <sys/syscall.h>
   59 #include <sys/syscallsubr.h>
   60 #include <sys/sysctl.h>
   61 #include <sys/sysent.h>
   62 #include <sys/sysproto.h>
   63 #include <sys/systm.h>
   64 #include <sys/sx.h>
   65 #include <sys/vnode.h>
   66 
   67 #include <security/mac/mac_framework.h>
   68 
   69 FEATURE(p1003_1b_semaphores, "POSIX P1003.1B semaphores support");
   70 /*
   71  * TODO
   72  *
   73  * - Resource limits?
   74  * - Replace global sem_lock with mtx_pool locks?
   75  * - Add a MAC check_create() hook for creating new named semaphores.
   76  */
   77 
   78 #ifndef SEM_MAX
   79 #define SEM_MAX 30
   80 #endif
   81 
   82 #ifdef SEM_DEBUG
   83 #define DP(x)   printf x
   84 #else
   85 #define DP(x)
   86 #endif
   87 
   88 struct ksem_mapping {
   89         char            *km_path;
   90         Fnv32_t         km_fnv;
   91         struct ksem     *km_ksem;
   92         LIST_ENTRY(ksem_mapping) km_link;
   93 };
   94 
   95 static MALLOC_DEFINE(M_KSEM, "ksem", "semaphore file descriptor");
   96 static LIST_HEAD(, ksem_mapping) *ksem_dictionary;
   97 static struct sx ksem_dict_lock;
   98 static struct mtx ksem_count_lock;
   99 static struct mtx sem_lock;
  100 static u_long ksem_hash;
  101 static int ksem_dead;
  102 
  103 #define KSEM_HASH(fnv)  (&ksem_dictionary[(fnv) & ksem_hash])
  104 
  105 static int nsems = 0;
  106 SYSCTL_DECL(_p1003_1b);
  107 SYSCTL_INT(_p1003_1b, OID_AUTO, nsems, CTLFLAG_RD, &nsems, 0,
  108     "Number of active kernel POSIX semaphores");
  109 
  110 static int      kern_sem_wait(struct thread *td, semid_t id, int tryflag,
  111                     struct timespec *abstime);
  112 static int      ksem_access(struct ksem *ks, struct ucred *ucred);
  113 static struct ksem *ksem_alloc(struct ucred *ucred, mode_t mode,
  114                     unsigned int value);
  115 static int      ksem_create(struct thread *td, const char *path,
  116                     semid_t *semidp, mode_t mode, unsigned int value,
  117                     int flags, int compat32);
  118 static void     ksem_drop(struct ksem *ks);
  119 static int      ksem_get(struct thread *td, semid_t id, cap_rights_t rights,
  120     struct file **fpp);
  121 static struct ksem *ksem_hold(struct ksem *ks);
  122 static void     ksem_insert(char *path, Fnv32_t fnv, struct ksem *ks);
  123 static struct ksem *ksem_lookup(char *path, Fnv32_t fnv);
  124 static void     ksem_module_destroy(void);
  125 static int      ksem_module_init(void);
  126 static int      ksem_remove(char *path, Fnv32_t fnv, struct ucred *ucred);
  127 static int      sem_modload(struct module *module, int cmd, void *arg);
  128 
  129 static fo_rdwr_t        ksem_read;
  130 static fo_rdwr_t        ksem_write;
  131 static fo_truncate_t    ksem_truncate;
  132 static fo_ioctl_t       ksem_ioctl;
  133 static fo_poll_t        ksem_poll;
  134 static fo_kqfilter_t    ksem_kqfilter;
  135 static fo_stat_t        ksem_stat;
  136 static fo_close_t       ksem_closef;
  137 static fo_chmod_t       ksem_chmod;
  138 static fo_chown_t       ksem_chown;
  139 
  140 /* File descriptor operations. */
  141 static struct fileops ksem_ops = {
  142         .fo_read = ksem_read,
  143         .fo_write = ksem_write,
  144         .fo_truncate = ksem_truncate,
  145         .fo_ioctl = ksem_ioctl,
  146         .fo_poll = ksem_poll,
  147         .fo_kqfilter = ksem_kqfilter,
  148         .fo_stat = ksem_stat,
  149         .fo_close = ksem_closef,
  150         .fo_chmod = ksem_chmod,
  151         .fo_chown = ksem_chown,
  152         .fo_flags = DFLAG_PASSABLE
  153 };
  154 
  155 FEATURE(posix_sem, "POSIX semaphores");
  156 
  157 static int
  158 ksem_read(struct file *fp, struct uio *uio, struct ucred *active_cred,
  159     int flags, struct thread *td)
  160 {
  161 
  162         return (EOPNOTSUPP);
  163 }
  164 
  165 static int
  166 ksem_write(struct file *fp, struct uio *uio, struct ucred *active_cred,
  167     int flags, struct thread *td)
  168 {
  169 
  170         return (EOPNOTSUPP);
  171 }
  172 
  173 static int
  174 ksem_truncate(struct file *fp, off_t length, struct ucred *active_cred,
  175     struct thread *td)
  176 {
  177 
  178         return (EINVAL);
  179 }
  180 
  181 static int
  182 ksem_ioctl(struct file *fp, u_long com, void *data,
  183     struct ucred *active_cred, struct thread *td)
  184 {
  185 
  186         return (EOPNOTSUPP);
  187 }
  188 
  189 static int
  190 ksem_poll(struct file *fp, int events, struct ucred *active_cred,
  191     struct thread *td)
  192 {
  193 
  194         return (EOPNOTSUPP);
  195 }
  196 
  197 static int
  198 ksem_kqfilter(struct file *fp, struct knote *kn)
  199 {
  200 
  201         return (EOPNOTSUPP);
  202 }
  203 
  204 static int
  205 ksem_stat(struct file *fp, struct stat *sb, struct ucred *active_cred,
  206     struct thread *td)
  207 {
  208         struct ksem *ks;
  209 #ifdef MAC
  210         int error;
  211 #endif
  212 
  213         ks = fp->f_data;
  214 
  215 #ifdef MAC
  216         error = mac_posixsem_check_stat(active_cred, fp->f_cred, ks);
  217         if (error)
  218                 return (error);
  219 #endif
  220         
  221         /*
  222          * Attempt to return sanish values for fstat() on a semaphore
  223          * file descriptor.
  224          */
  225         bzero(sb, sizeof(*sb));
  226 
  227         mtx_lock(&sem_lock);
  228         sb->st_atim = ks->ks_atime;
  229         sb->st_ctim = ks->ks_ctime;
  230         sb->st_mtim = ks->ks_mtime;
  231         sb->st_birthtim = ks->ks_birthtime;
  232         sb->st_uid = ks->ks_uid;
  233         sb->st_gid = ks->ks_gid;
  234         sb->st_mode = S_IFREG | ks->ks_mode;            /* XXX */
  235         mtx_unlock(&sem_lock);
  236 
  237         return (0);
  238 }
  239 
  240 static int
  241 ksem_chmod(struct file *fp, mode_t mode, struct ucred *active_cred,
  242     struct thread *td)
  243 {
  244         struct ksem *ks;
  245         int error;
  246 
  247         error = 0;
  248         ks = fp->f_data;
  249         mtx_lock(&sem_lock);
  250 #ifdef MAC
  251         error = mac_posixsem_check_setmode(active_cred, ks, mode);
  252         if (error != 0)
  253                 goto out;
  254 #endif
  255         error = vaccess(VREG, ks->ks_mode, ks->ks_uid, ks->ks_gid, VADMIN,
  256             active_cred, NULL);
  257         if (error != 0)
  258                 goto out;
  259         ks->ks_mode = mode & ACCESSPERMS;
  260 out:
  261         mtx_unlock(&sem_lock);
  262         return (error);
  263 }
  264 
  265 static int
  266 ksem_chown(struct file *fp, uid_t uid, gid_t gid, struct ucred *active_cred,
  267     struct thread *td)
  268 {
  269         struct ksem *ks;
  270         int error;
  271 
  272         error = 0;
  273         ks = fp->f_data;
  274         mtx_lock(&sem_lock);
  275 #ifdef MAC
  276         error = mac_posixsem_check_setowner(active_cred, ks, uid, gid);
  277         if (error != 0)
  278                 goto out;
  279 #endif
  280         if (uid == (uid_t)-1)
  281                 uid = ks->ks_uid;
  282         if (gid == (gid_t)-1)
  283                  gid = ks->ks_gid;
  284         if (((uid != ks->ks_uid && uid != active_cred->cr_uid) ||
  285             (gid != ks->ks_gid && !groupmember(gid, active_cred))) &&
  286             (error = priv_check_cred(active_cred, PRIV_VFS_CHOWN, 0)))
  287                 goto out;
  288         ks->ks_uid = uid;
  289         ks->ks_gid = gid;
  290 out:
  291         mtx_unlock(&sem_lock);
  292         return (error);
  293 }
  294 
  295 static int
  296 ksem_closef(struct file *fp, struct thread *td)
  297 {
  298         struct ksem *ks;
  299 
  300         ks = fp->f_data;
  301         fp->f_data = NULL;
  302         ksem_drop(ks);
  303 
  304         return (0);
  305 }
  306 
  307 /*
  308  * ksem object management including creation and reference counting
  309  * routines.
  310  */
  311 static struct ksem *
  312 ksem_alloc(struct ucred *ucred, mode_t mode, unsigned int value)
  313 {
  314         struct ksem *ks;
  315 
  316         mtx_lock(&ksem_count_lock);
  317         if (nsems == p31b_getcfg(CTL_P1003_1B_SEM_NSEMS_MAX) || ksem_dead) {
  318                 mtx_unlock(&ksem_count_lock);
  319                 return (NULL);
  320         }
  321         nsems++;
  322         mtx_unlock(&ksem_count_lock);
  323         ks = malloc(sizeof(*ks), M_KSEM, M_WAITOK | M_ZERO);
  324         ks->ks_uid = ucred->cr_uid;
  325         ks->ks_gid = ucred->cr_gid;
  326         ks->ks_mode = mode;
  327         ks->ks_value = value;
  328         cv_init(&ks->ks_cv, "ksem");
  329         vfs_timestamp(&ks->ks_birthtime);
  330         ks->ks_atime = ks->ks_mtime = ks->ks_ctime = ks->ks_birthtime;
  331         refcount_init(&ks->ks_ref, 1);
  332 #ifdef MAC
  333         mac_posixsem_init(ks);
  334         mac_posixsem_create(ucred, ks);
  335 #endif
  336 
  337         return (ks);
  338 }
  339 
  340 static struct ksem *
  341 ksem_hold(struct ksem *ks)
  342 {
  343 
  344         refcount_acquire(&ks->ks_ref);
  345         return (ks);
  346 }
  347 
  348 static void
  349 ksem_drop(struct ksem *ks)
  350 {
  351 
  352         if (refcount_release(&ks->ks_ref)) {
  353 #ifdef MAC
  354                 mac_posixsem_destroy(ks);
  355 #endif
  356                 cv_destroy(&ks->ks_cv);
  357                 free(ks, M_KSEM);
  358                 mtx_lock(&ksem_count_lock);
  359                 nsems--;
  360                 mtx_unlock(&ksem_count_lock);
  361         }
  362 }
  363 
  364 /*
  365  * Determine if the credentials have sufficient permissions for read
  366  * and write access.
  367  */
  368 static int
  369 ksem_access(struct ksem *ks, struct ucred *ucred)
  370 {
  371         int error;
  372 
  373         error = vaccess(VREG, ks->ks_mode, ks->ks_uid, ks->ks_gid,
  374             VREAD | VWRITE, ucred, NULL);
  375         if (error)
  376                 error = priv_check_cred(ucred, PRIV_SEM_WRITE, 0);
  377         return (error);
  378 }
  379 
  380 /*
  381  * Dictionary management.  We maintain an in-kernel dictionary to map
  382  * paths to semaphore objects.  We use the FNV hash on the path to
  383  * store the mappings in a hash table.
  384  */
  385 static struct ksem *
  386 ksem_lookup(char *path, Fnv32_t fnv)
  387 {
  388         struct ksem_mapping *map;
  389 
  390         LIST_FOREACH(map, KSEM_HASH(fnv), km_link) {
  391                 if (map->km_fnv != fnv)
  392                         continue;
  393                 if (strcmp(map->km_path, path) == 0)
  394                         return (map->km_ksem);
  395         }
  396 
  397         return (NULL);
  398 }
  399 
  400 static void
  401 ksem_insert(char *path, Fnv32_t fnv, struct ksem *ks)
  402 {
  403         struct ksem_mapping *map;
  404 
  405         map = malloc(sizeof(struct ksem_mapping), M_KSEM, M_WAITOK);
  406         map->km_path = path;
  407         map->km_fnv = fnv;
  408         map->km_ksem = ksem_hold(ks);
  409         ks->ks_path = path;
  410         LIST_INSERT_HEAD(KSEM_HASH(fnv), map, km_link);
  411 }
  412 
  413 static int
  414 ksem_remove(char *path, Fnv32_t fnv, struct ucred *ucred)
  415 {
  416         struct ksem_mapping *map;
  417         int error;
  418 
  419         LIST_FOREACH(map, KSEM_HASH(fnv), km_link) {
  420                 if (map->km_fnv != fnv)
  421                         continue;
  422                 if (strcmp(map->km_path, path) == 0) {
  423 #ifdef MAC
  424                         error = mac_posixsem_check_unlink(ucred, map->km_ksem);
  425                         if (error)
  426                                 return (error);
  427 #endif
  428                         error = ksem_access(map->km_ksem, ucred);
  429                         if (error)
  430                                 return (error);
  431                         map->km_ksem->ks_path = NULL;
  432                         LIST_REMOVE(map, km_link);
  433                         ksem_drop(map->km_ksem);
  434                         free(map->km_path, M_KSEM);
  435                         free(map, M_KSEM);
  436                         return (0);
  437                 }
  438         }
  439 
  440         return (ENOENT);
  441 }
  442 
  443 static void
  444 ksem_info_impl(struct ksem *ks, char *path, size_t size, uint32_t *value)
  445 {
  446 
  447         if (ks->ks_path == NULL)
  448                 return;
  449         sx_slock(&ksem_dict_lock);
  450         if (ks->ks_path != NULL)
  451                 strlcpy(path, ks->ks_path, size);
  452         if (value != NULL)
  453                 *value = ks->ks_value;
  454         sx_sunlock(&ksem_dict_lock);
  455 }
  456 
  457 static int
  458 ksem_create_copyout_semid(struct thread *td, semid_t *semidp, int fd,
  459     int compat32)
  460 {
  461         semid_t semid;
  462 #ifdef COMPAT_FREEBSD32
  463         int32_t semid32;
  464 #endif
  465         void *ptr;
  466         size_t ptrs;
  467 
  468 #ifdef COMPAT_FREEBSD32
  469         if (compat32) {
  470                 semid32 = fd;
  471                 ptr = &semid32;
  472                 ptrs = sizeof(semid32);
  473         } else {
  474 #endif
  475                 semid = fd;
  476                 ptr = &semid;
  477                 ptrs = sizeof(semid);
  478                 compat32 = 0; /* silence gcc */
  479 #ifdef COMPAT_FREEBSD32
  480         }
  481 #endif
  482 
  483         return (copyout(ptr, semidp, ptrs));
  484 }
  485 
  486 /* Other helper routines. */
  487 static int
  488 ksem_create(struct thread *td, const char *name, semid_t *semidp, mode_t mode,
  489     unsigned int value, int flags, int compat32)
  490 {
  491         struct filedesc *fdp;
  492         struct ksem *ks;
  493         struct file *fp;
  494         char *path;
  495         Fnv32_t fnv;
  496         int error, fd;
  497 
  498         if (value > SEM_VALUE_MAX)
  499                 return (EINVAL);
  500 
  501         fdp = td->td_proc->p_fd;
  502         mode = (mode & ~fdp->fd_cmask) & ACCESSPERMS;
  503         error = falloc(td, &fp, &fd, O_CLOEXEC);
  504         if (error) {
  505                 if (name == NULL)
  506                         error = ENOSPC;
  507                 return (error);
  508         }
  509 
  510         /*
  511          * Go ahead and copyout the file descriptor now.  This is a bit
  512          * premature, but it is a lot easier to handle errors as opposed
  513          * to later when we've possibly created a new semaphore, etc.
  514          */
  515         error = ksem_create_copyout_semid(td, semidp, fd, compat32);
  516         if (error) {
  517                 fdclose(fdp, fp, fd, td);
  518                 fdrop(fp, td);
  519                 return (error);
  520         }
  521 
  522         if (name == NULL) {
  523                 /* Create an anonymous semaphore. */
  524                 ks = ksem_alloc(td->td_ucred, mode, value);
  525                 if (ks == NULL)
  526                         error = ENOSPC;
  527                 else
  528                         ks->ks_flags |= KS_ANONYMOUS;
  529         } else {
  530                 path = malloc(MAXPATHLEN, M_KSEM, M_WAITOK);
  531                 error = copyinstr(name, path, MAXPATHLEN, NULL);
  532 
  533                 /* Require paths to start with a '/' character. */
  534                 if (error == 0 && path[0] != '/')
  535                         error = EINVAL;
  536                 if (error) {
  537                         fdclose(fdp, fp, fd, td);
  538                         fdrop(fp, td);
  539                         free(path, M_KSEM);
  540                         return (error);
  541                 }
  542 
  543                 fnv = fnv_32_str(path, FNV1_32_INIT);
  544                 sx_xlock(&ksem_dict_lock);
  545                 ks = ksem_lookup(path, fnv);
  546                 if (ks == NULL) {
  547                         /* Object does not exist, create it if requested. */
  548                         if (flags & O_CREAT) {
  549                                 ks = ksem_alloc(td->td_ucred, mode, value);
  550                                 if (ks == NULL)
  551                                         error = ENFILE;
  552                                 else {
  553                                         ksem_insert(path, fnv, ks);
  554                                         path = NULL;
  555                                 }
  556                         } else
  557                                 error = ENOENT;
  558                 } else {
  559                         /*
  560                          * Object already exists, obtain a new
  561                          * reference if requested and permitted.
  562                          */
  563                         if ((flags & (O_CREAT | O_EXCL)) ==
  564                             (O_CREAT | O_EXCL))
  565                                 error = EEXIST;
  566                         else {
  567 #ifdef MAC
  568                                 error = mac_posixsem_check_open(td->td_ucred,
  569                                     ks);
  570                                 if (error == 0)
  571 #endif
  572                                 error = ksem_access(ks, td->td_ucred);
  573                         }
  574                         if (error == 0)
  575                                 ksem_hold(ks);
  576 #ifdef INVARIANTS
  577                         else
  578                                 ks = NULL;
  579 #endif
  580                 }
  581                 sx_xunlock(&ksem_dict_lock);
  582                 if (path)
  583                         free(path, M_KSEM);
  584         }
  585 
  586         if (error) {
  587                 KASSERT(ks == NULL, ("ksem_create error with a ksem"));
  588                 fdclose(fdp, fp, fd, td);
  589                 fdrop(fp, td);
  590                 return (error);
  591         }
  592         KASSERT(ks != NULL, ("ksem_create w/o a ksem"));
  593 
  594         finit(fp, FREAD | FWRITE, DTYPE_SEM, ks, &ksem_ops);
  595 
  596         fdrop(fp, td);
  597 
  598         return (0);
  599 }
  600 
  601 static int
  602 ksem_get(struct thread *td, semid_t id, cap_rights_t rights, struct file **fpp)
  603 {
  604         struct ksem *ks;
  605         struct file *fp;
  606         int error;
  607 
  608         error = fget(td, id, rights, &fp);
  609         if (error)
  610                 return (EINVAL);
  611         if (fp->f_type != DTYPE_SEM) {
  612                 fdrop(fp, td);
  613                 return (EINVAL);
  614         }
  615         ks = fp->f_data;
  616         if (ks->ks_flags & KS_DEAD) {
  617                 fdrop(fp, td);
  618                 return (EINVAL);
  619         }
  620         *fpp = fp;
  621         return (0);
  622 }
  623 
  624 /* System calls. */
  625 #ifndef _SYS_SYSPROTO_H_
  626 struct ksem_init_args {
  627         unsigned int    value;
  628         semid_t         *idp;
  629 };
  630 #endif
  631 int
  632 sys_ksem_init(struct thread *td, struct ksem_init_args *uap)
  633 {
  634 
  635         return (ksem_create(td, NULL, uap->idp, S_IRWXU | S_IRWXG, uap->value,
  636             0, 0));
  637 }
  638 
  639 #ifndef _SYS_SYSPROTO_H_
  640 struct ksem_open_args {
  641         char            *name;
  642         int             oflag;
  643         mode_t          mode;
  644         unsigned int    value;
  645         semid_t         *idp;   
  646 };
  647 #endif
  648 int
  649 sys_ksem_open(struct thread *td, struct ksem_open_args *uap)
  650 {
  651 
  652         DP((">>> ksem_open start, pid=%d\n", (int)td->td_proc->p_pid));
  653 
  654         if ((uap->oflag & ~(O_CREAT | O_EXCL)) != 0)
  655                 return (EINVAL);
  656         return (ksem_create(td, uap->name, uap->idp, uap->mode, uap->value,
  657             uap->oflag, 0));
  658 }
  659 
  660 #ifndef _SYS_SYSPROTO_H_
  661 struct ksem_unlink_args {
  662         char            *name;
  663 };
  664 #endif
  665 int
  666 sys_ksem_unlink(struct thread *td, struct ksem_unlink_args *uap)
  667 {
  668         char *path;
  669         Fnv32_t fnv;
  670         int error;
  671 
  672         path = malloc(MAXPATHLEN, M_TEMP, M_WAITOK);
  673         error = copyinstr(uap->name, path, MAXPATHLEN, NULL);
  674         if (error) {
  675                 free(path, M_TEMP);
  676                 return (error);
  677         }
  678 
  679         fnv = fnv_32_str(path, FNV1_32_INIT);
  680         sx_xlock(&ksem_dict_lock);
  681         error = ksem_remove(path, fnv, td->td_ucred);
  682         sx_xunlock(&ksem_dict_lock);
  683         free(path, M_TEMP);
  684 
  685         return (error);
  686 }
  687 
  688 #ifndef _SYS_SYSPROTO_H_
  689 struct ksem_close_args {
  690         semid_t         id;
  691 };
  692 #endif
  693 int
  694 sys_ksem_close(struct thread *td, struct ksem_close_args *uap)
  695 {
  696         struct ksem *ks;
  697         struct file *fp;
  698         int error;
  699 
  700         /* No capability rights required to close a semaphore. */
  701         error = ksem_get(td, uap->id, 0, &fp);
  702         if (error)
  703                 return (error);
  704         ks = fp->f_data;
  705         if (ks->ks_flags & KS_ANONYMOUS) {
  706                 fdrop(fp, td);
  707                 return (EINVAL);
  708         }
  709         error = kern_close(td, uap->id);
  710         fdrop(fp, td);
  711         return (error);
  712 }
  713 
  714 #ifndef _SYS_SYSPROTO_H_
  715 struct ksem_post_args {
  716         semid_t id;
  717 };
  718 #endif
  719 int
  720 sys_ksem_post(struct thread *td, struct ksem_post_args *uap)
  721 {
  722         struct file *fp;
  723         struct ksem *ks;
  724         int error;
  725 
  726         error = ksem_get(td, uap->id, CAP_SEM_POST, &fp);
  727         if (error)
  728                 return (error);
  729         ks = fp->f_data;
  730 
  731         mtx_lock(&sem_lock);
  732 #ifdef MAC
  733         error = mac_posixsem_check_post(td->td_ucred, fp->f_cred, ks);
  734         if (error)
  735                 goto err;
  736 #endif
  737         if (ks->ks_value == SEM_VALUE_MAX) {
  738                 error = EOVERFLOW;
  739                 goto err;
  740         }
  741         ++ks->ks_value;
  742         if (ks->ks_waiters > 0)
  743                 cv_signal(&ks->ks_cv);
  744         error = 0;
  745         vfs_timestamp(&ks->ks_ctime);
  746 err:
  747         mtx_unlock(&sem_lock);
  748         fdrop(fp, td);
  749         return (error);
  750 }
  751 
  752 #ifndef _SYS_SYSPROTO_H_
  753 struct ksem_wait_args {
  754         semid_t         id;
  755 };
  756 #endif
  757 int
  758 sys_ksem_wait(struct thread *td, struct ksem_wait_args *uap)
  759 {
  760 
  761         return (kern_sem_wait(td, uap->id, 0, NULL));
  762 }
  763 
  764 #ifndef _SYS_SYSPROTO_H_
  765 struct ksem_timedwait_args {
  766         semid_t         id;
  767         const struct timespec *abstime;
  768 };
  769 #endif
  770 int
  771 sys_ksem_timedwait(struct thread *td, struct ksem_timedwait_args *uap)
  772 {
  773         struct timespec abstime;
  774         struct timespec *ts;
  775         int error;
  776 
  777         /*
  778          * We allow a null timespec (wait forever).
  779          */
  780         if (uap->abstime == NULL)
  781                 ts = NULL;
  782         else {
  783                 error = copyin(uap->abstime, &abstime, sizeof(abstime));
  784                 if (error != 0)
  785                         return (error);
  786                 if (abstime.tv_nsec >= 1000000000 || abstime.tv_nsec < 0)
  787                         return (EINVAL);
  788                 ts = &abstime;
  789         }
  790         return (kern_sem_wait(td, uap->id, 0, ts));
  791 }
  792 
  793 #ifndef _SYS_SYSPROTO_H_
  794 struct ksem_trywait_args {
  795         semid_t         id;
  796 };
  797 #endif
  798 int
  799 sys_ksem_trywait(struct thread *td, struct ksem_trywait_args *uap)
  800 {
  801 
  802         return (kern_sem_wait(td, uap->id, 1, NULL));
  803 }
  804 
  805 static int
  806 kern_sem_wait(struct thread *td, semid_t id, int tryflag,
  807     struct timespec *abstime)
  808 {
  809         struct timespec ts1, ts2;
  810         struct timeval tv;
  811         struct file *fp;
  812         struct ksem *ks;
  813         int error;
  814 
  815         DP((">>> kern_sem_wait entered! pid=%d\n", (int)td->td_proc->p_pid));
  816         error = ksem_get(td, id, CAP_SEM_WAIT, &fp);
  817         if (error)
  818                 return (error);
  819         ks = fp->f_data;
  820         mtx_lock(&sem_lock);
  821         DP((">>> kern_sem_wait critical section entered! pid=%d\n",
  822             (int)td->td_proc->p_pid));
  823 #ifdef MAC
  824         error = mac_posixsem_check_wait(td->td_ucred, fp->f_cred, ks);
  825         if (error) {
  826                 DP(("kern_sem_wait mac failed\n"));
  827                 goto err;
  828         }
  829 #endif
  830         DP(("kern_sem_wait value = %d, tryflag %d\n", ks->ks_value, tryflag));
  831         vfs_timestamp(&ks->ks_atime);
  832         while (ks->ks_value == 0) {
  833                 ks->ks_waiters++;
  834                 if (tryflag != 0)
  835                         error = EAGAIN;
  836                 else if (abstime == NULL)
  837                         error = cv_wait_sig(&ks->ks_cv, &sem_lock);
  838                 else {
  839                         for (;;) {
  840                                 ts1 = *abstime;
  841                                 getnanotime(&ts2);
  842                                 timespecsub(&ts1, &ts2);
  843                                 TIMESPEC_TO_TIMEVAL(&tv, &ts1);
  844                                 if (tv.tv_sec < 0) {
  845                                         error = ETIMEDOUT;
  846                                         break;
  847                                 }
  848                                 error = cv_timedwait_sig(&ks->ks_cv,
  849                                     &sem_lock, tvtohz(&tv));
  850                                 if (error != EWOULDBLOCK)
  851                                         break;
  852                         }
  853                 }
  854                 ks->ks_waiters--;
  855                 if (error)
  856                         goto err;
  857         }
  858         ks->ks_value--;
  859         DP(("kern_sem_wait value post-decrement = %d\n", ks->ks_value));
  860         error = 0;
  861 err:
  862         mtx_unlock(&sem_lock);
  863         fdrop(fp, td);
  864         DP(("<<< kern_sem_wait leaving, pid=%d, error = %d\n",
  865             (int)td->td_proc->p_pid, error));
  866         return (error);
  867 }
  868 
  869 #ifndef _SYS_SYSPROTO_H_
  870 struct ksem_getvalue_args {
  871         semid_t         id;
  872         int             *val;
  873 };
  874 #endif
  875 int
  876 sys_ksem_getvalue(struct thread *td, struct ksem_getvalue_args *uap)
  877 {
  878         struct file *fp;
  879         struct ksem *ks;
  880         int error, val;
  881 
  882         error = ksem_get(td, uap->id, CAP_SEM_GETVALUE, &fp);
  883         if (error)
  884                 return (error);
  885         ks = fp->f_data;
  886 
  887         mtx_lock(&sem_lock);
  888 #ifdef MAC
  889         error = mac_posixsem_check_getvalue(td->td_ucred, fp->f_cred, ks);
  890         if (error) {
  891                 mtx_unlock(&sem_lock);
  892                 fdrop(fp, td);
  893                 return (error);
  894         }
  895 #endif
  896         val = ks->ks_value;
  897         vfs_timestamp(&ks->ks_atime);
  898         mtx_unlock(&sem_lock);
  899         fdrop(fp, td);
  900         error = copyout(&val, uap->val, sizeof(val));
  901         return (error);
  902 }
  903 
  904 #ifndef _SYS_SYSPROTO_H_
  905 struct ksem_destroy_args {
  906         semid_t         id;
  907 };
  908 #endif
  909 int
  910 sys_ksem_destroy(struct thread *td, struct ksem_destroy_args *uap)
  911 {
  912         struct file *fp;
  913         struct ksem *ks;
  914         int error;
  915 
  916         /* No capability rights required to close a semaphore. */
  917         error = ksem_get(td, uap->id, 0, &fp);
  918         if (error)
  919                 return (error);
  920         ks = fp->f_data;
  921         if (!(ks->ks_flags & KS_ANONYMOUS)) {
  922                 fdrop(fp, td);
  923                 return (EINVAL);
  924         }
  925         mtx_lock(&sem_lock);
  926         if (ks->ks_waiters != 0) {
  927                 mtx_unlock(&sem_lock);
  928                 error = EBUSY;
  929                 goto err;
  930         }
  931         ks->ks_flags |= KS_DEAD;
  932         mtx_unlock(&sem_lock);
  933 
  934         error = kern_close(td, uap->id);
  935 err:
  936         fdrop(fp, td);
  937         return (error);
  938 }
  939 
  940 static struct syscall_helper_data ksem_syscalls[] = {
  941         SYSCALL_INIT_HELPER(ksem_init),
  942         SYSCALL_INIT_HELPER(ksem_open),
  943         SYSCALL_INIT_HELPER(ksem_unlink),
  944         SYSCALL_INIT_HELPER(ksem_close),
  945         SYSCALL_INIT_HELPER(ksem_post),
  946         SYSCALL_INIT_HELPER(ksem_wait),
  947         SYSCALL_INIT_HELPER(ksem_timedwait),
  948         SYSCALL_INIT_HELPER(ksem_trywait),
  949         SYSCALL_INIT_HELPER(ksem_getvalue),
  950         SYSCALL_INIT_HELPER(ksem_destroy),
  951         SYSCALL_INIT_LAST
  952 };
  953 
  954 #ifdef COMPAT_FREEBSD32
  955 #include <compat/freebsd32/freebsd32.h>
  956 #include <compat/freebsd32/freebsd32_proto.h>
  957 #include <compat/freebsd32/freebsd32_signal.h>
  958 #include <compat/freebsd32/freebsd32_syscall.h>
  959 #include <compat/freebsd32/freebsd32_util.h>
  960 
  961 int
  962 freebsd32_ksem_init(struct thread *td, struct freebsd32_ksem_init_args *uap)
  963 {
  964 
  965         return (ksem_create(td, NULL, uap->idp, S_IRWXU | S_IRWXG, uap->value,
  966             0, 1));
  967 }
  968 
  969 int
  970 freebsd32_ksem_open(struct thread *td, struct freebsd32_ksem_open_args *uap)
  971 {
  972 
  973         if ((uap->oflag & ~(O_CREAT | O_EXCL)) != 0)
  974                 return (EINVAL);
  975         return (ksem_create(td, uap->name, uap->idp, uap->mode, uap->value,
  976             uap->oflag, 1));
  977 }
  978 
  979 int
  980 freebsd32_ksem_timedwait(struct thread *td,
  981     struct freebsd32_ksem_timedwait_args *uap)
  982 {
  983         struct timespec32 abstime32;
  984         struct timespec *ts, abstime;
  985         int error;
  986 
  987         /*
  988          * We allow a null timespec (wait forever).
  989          */
  990         if (uap->abstime == NULL)
  991                 ts = NULL;
  992         else {
  993                 error = copyin(uap->abstime, &abstime32, sizeof(abstime32));
  994                 if (error != 0)
  995                         return (error);
  996                 CP(abstime32, abstime, tv_sec);
  997                 CP(abstime32, abstime, tv_nsec);
  998                 if (abstime.tv_nsec >= 1000000000 || abstime.tv_nsec < 0)
  999                         return (EINVAL);
 1000                 ts = &abstime;
 1001         }
 1002         return (kern_sem_wait(td, uap->id, 0, ts));
 1003 }
 1004 
 1005 static struct syscall_helper_data ksem32_syscalls[] = {
 1006         SYSCALL32_INIT_HELPER(freebsd32_ksem_init),
 1007         SYSCALL32_INIT_HELPER(freebsd32_ksem_open),
 1008         SYSCALL32_INIT_HELPER_COMPAT(ksem_unlink),
 1009         SYSCALL32_INIT_HELPER_COMPAT(ksem_close),
 1010         SYSCALL32_INIT_HELPER_COMPAT(ksem_post),
 1011         SYSCALL32_INIT_HELPER_COMPAT(ksem_wait),
 1012         SYSCALL32_INIT_HELPER(freebsd32_ksem_timedwait),
 1013         SYSCALL32_INIT_HELPER_COMPAT(ksem_trywait),
 1014         SYSCALL32_INIT_HELPER_COMPAT(ksem_getvalue),
 1015         SYSCALL32_INIT_HELPER_COMPAT(ksem_destroy),
 1016         SYSCALL_INIT_LAST
 1017 };
 1018 #endif
 1019 
 1020 static int
 1021 ksem_module_init(void)
 1022 {
 1023         int error;
 1024 
 1025         mtx_init(&sem_lock, "sem", NULL, MTX_DEF);
 1026         mtx_init(&ksem_count_lock, "ksem count", NULL, MTX_DEF);
 1027         sx_init(&ksem_dict_lock, "ksem dictionary");
 1028         ksem_dictionary = hashinit(1024, M_KSEM, &ksem_hash);
 1029         p31b_setcfg(CTL_P1003_1B_SEMAPHORES, 200112L);
 1030         p31b_setcfg(CTL_P1003_1B_SEM_NSEMS_MAX, SEM_MAX);
 1031         p31b_setcfg(CTL_P1003_1B_SEM_VALUE_MAX, SEM_VALUE_MAX);
 1032         ksem_info = ksem_info_impl;
 1033 
 1034         error = syscall_helper_register(ksem_syscalls);
 1035         if (error)
 1036                 return (error);
 1037 #ifdef COMPAT_FREEBSD32
 1038         error = syscall32_helper_register(ksem32_syscalls);
 1039         if (error)
 1040                 return (error);
 1041 #endif
 1042         return (0);
 1043 }
 1044 
 1045 static void
 1046 ksem_module_destroy(void)
 1047 {
 1048 
 1049 #ifdef COMPAT_FREEBSD32
 1050         syscall32_helper_unregister(ksem32_syscalls);
 1051 #endif
 1052         syscall_helper_unregister(ksem_syscalls);
 1053 
 1054         ksem_info = NULL;
 1055         p31b_setcfg(CTL_P1003_1B_SEMAPHORES, 0);
 1056         hashdestroy(ksem_dictionary, M_KSEM, ksem_hash);
 1057         sx_destroy(&ksem_dict_lock);
 1058         mtx_destroy(&ksem_count_lock);
 1059         mtx_destroy(&sem_lock);
 1060         p31b_unsetcfg(CTL_P1003_1B_SEM_VALUE_MAX);
 1061         p31b_unsetcfg(CTL_P1003_1B_SEM_NSEMS_MAX);
 1062 }
 1063 
 1064 static int
 1065 sem_modload(struct module *module, int cmd, void *arg)
 1066 {
 1067         int error = 0;
 1068 
 1069         switch (cmd) {
 1070         case MOD_LOAD:
 1071                 error = ksem_module_init();
 1072                 if (error)
 1073                         ksem_module_destroy();
 1074                 break;
 1075 
 1076         case MOD_UNLOAD:
 1077                 mtx_lock(&ksem_count_lock);
 1078                 if (nsems != 0) {
 1079                         error = EOPNOTSUPP;
 1080                         mtx_unlock(&ksem_count_lock);
 1081                         break;
 1082                 }
 1083                 ksem_dead = 1;
 1084                 mtx_unlock(&ksem_count_lock);
 1085                 ksem_module_destroy();
 1086                 break;
 1087 
 1088         case MOD_SHUTDOWN:
 1089                 break;
 1090         default:
 1091                 error = EINVAL;
 1092                 break;
 1093         }
 1094         return (error);
 1095 }
 1096 
 1097 static moduledata_t sem_mod = {
 1098         "sem",
 1099         &sem_modload,
 1100         NULL
 1101 };
 1102 
 1103 DECLARE_MODULE(sem, sem_mod, SI_SUB_SYSV_SEM, SI_ORDER_FIRST);
 1104 MODULE_VERSION(sem, 1);

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