uipc_sem.c

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/*-
 * Copyright (c) 2002 Alfred Perlstein <alfred@FreeBSD.org>
 * Copyright (c) 2003-2005 SPARTA, Inc.
 * Copyright (c) 2005 Robert N. M. Watson
 * All rights reserved.
 *
 * This software was developed for the FreeBSD Project in part by Network
 * Associates Laboratories, the Security Research Division of Network
 * Associates, Inc. under DARPA/SPAWAR contract N66001-01-C-8035 ("CBOSS"),
 * as part of the DARPA CHATS research program.
 *
 * 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("$BSDSUniX$");

#include "opt_compat.h"
#include "opt_posix.h"

#include <sys/param.h>
#include <sys/capability.h>
#include <sys/condvar.h>
#include <sys/fcntl.h>
#include <sys/file.h>
#include <sys/filedesc.h>
#include <sys/fnv_hash.h>
#include <sys/kernel.h>
#include <sys/ksem.h>
#include <sys/lock.h>
#include <sys/malloc.h>
#include <sys/module.h>
#include <sys/mutex.h>
#include <sys/priv.h>
#include <sys/proc.h>
#include <sys/posix4.h>
#include <sys/_semaphore.h>
#include <sys/stat.h>
#include <sys/syscall.h>
#include <sys/syscallsubr.h>
#include <sys/sysctl.h>
#include <sys/sysent.h>
#include <sys/sysproto.h>
#include <sys/systm.h>
#include <sys/sx.h>
#include <sys/vnode.h>

#include <security/mac/mac_framework.h>

FEATURE(p1003_1b_semaphores, "POSIX P1003.1B semaphores support");
/*
 * TODO
 *
 * - Resource limits?
 * - Replace global sem_lock with mtx_pool locks?
 * - Add a MAC check_create() hook for creating new named semaphores.
 */

#ifndef SEM_MAX
#define SEM_MAX 30
#endif

#ifdef SEM_DEBUG
#define DP(x)   printf x
#else
#define DP(x)
#endif

struct ksem_mapping {
        char            *km_path;
        Fnv32_t         km_fnv;
        struct ksem     *km_ksem;
        LIST_ENTRY(ksem_mapping) km_link;
};

static MALLOC_DEFINE(M_KSEM, "ksem", "semaphore file descriptor");
static LIST_HEAD(, ksem_mapping) *ksem_dictionary;
static struct sx ksem_dict_lock;
static struct mtx ksem_count_lock;
static struct mtx sem_lock;
static u_long ksem_hash;
static int ksem_dead;

#define KSEM_HASH(fnv)  (&ksem_dictionary[(fnv) & ksem_hash])

static int nsems = 0;
SYSCTL_DECL(_p1003_1b);
SYSCTL_INT(_p1003_1b, OID_AUTO, nsems, CTLFLAG_RD, &nsems, 0,
    "Number of active kernel POSIX semaphores");

static int      kern_sem_wait(struct thread *td, semid_t id, int tryflag,
                    struct timespec *abstime);
static int      ksem_access(struct ksem *ks, struct ucred *ucred);
static struct ksem *ksem_alloc(struct ucred *ucred, mode_t mode,
                    unsigned int value);
static int      ksem_create(struct thread *td, const char *path,
                    semid_t *semidp, mode_t mode, unsigned int value,
                    int flags, int compat32);
static void     ksem_drop(struct ksem *ks);
static int      ksem_get(struct thread *td, semid_t id, cap_rights_t rights,
    struct file **fpp);
static struct ksem *ksem_hold(struct ksem *ks);
static void     ksem_insert(char *path, Fnv32_t fnv, struct ksem *ks);
static struct ksem *ksem_lookup(char *path, Fnv32_t fnv);
static void     ksem_module_destroy(void);
static int      ksem_module_init(void);
static int      ksem_remove(char *path, Fnv32_t fnv, struct ucred *ucred);
static int      sem_modload(struct module *module, int cmd, void *arg);

static fo_rdwr_t        ksem_read;
static fo_rdwr_t        ksem_write;
static fo_truncate_t    ksem_truncate;
static fo_ioctl_t       ksem_ioctl;
static fo_poll_t        ksem_poll;
static fo_kqfilter_t    ksem_kqfilter;
static fo_stat_t        ksem_stat;
static fo_close_t       ksem_closef;
static fo_chmod_t       ksem_chmod;
static fo_chown_t       ksem_chown;

/* File descriptor operations. */
static struct fileops ksem_ops = {
        .fo_read = ksem_read,
        .fo_write = ksem_write,
        .fo_truncate = ksem_truncate,
        .fo_ioctl = ksem_ioctl,
        .fo_poll = ksem_poll,
        .fo_kqfilter = ksem_kqfilter,
        .fo_stat = ksem_stat,
        .fo_close = ksem_closef,
        .fo_chmod = ksem_chmod,
        .fo_chown = ksem_chown,
        .fo_flags = DFLAG_PASSABLE
};

FEATURE(posix_sem, "POSIX semaphores");

static int
ksem_read(struct file *fp, struct uio *uio, struct ucred *active_cred,
    int flags, struct thread *td)
{

        return (EOPNOTSUPP);
}

static int
ksem_write(struct file *fp, struct uio *uio, struct ucred *active_cred,
    int flags, struct thread *td)
{

        return (EOPNOTSUPP);
}

static int
ksem_truncate(struct file *fp, off_t length, struct ucred *active_cred,
    struct thread *td)
{

        return (EINVAL);
}

static int
ksem_ioctl(struct file *fp, u_long com, void *data,
    struct ucred *active_cred, struct thread *td)
{

        return (EOPNOTSUPP);
}

static int
ksem_poll(struct file *fp, int events, struct ucred *active_cred,
    struct thread *td)
{

        return (EOPNOTSUPP);
}

static int
ksem_kqfilter(struct file *fp, struct knote *kn)
{

        return (EOPNOTSUPP);
}

static int
ksem_stat(struct file *fp, struct stat *sb, struct ucred *active_cred,
    struct thread *td)
{
        struct ksem *ks;
#ifdef MAC
        int error;
#endif

        ks = fp->f_data;

#ifdef MAC
        error = mac_posixsem_check_stat(active_cred, fp->f_cred, ks);
        if (error)
                return (error);
#endif
        
        /*
         * Attempt to return sanish values for fstat() on a semaphore
         * file descriptor.
         */
        bzero(sb, sizeof(*sb));

        mtx_lock(&sem_lock);
        sb->st_atim = ks->ks_atime;
        sb->st_ctim = ks->ks_ctime;
        sb->st_mtim = ks->ks_mtime;
        sb->st_birthtim = ks->ks_birthtime;
        sb->st_uid = ks->ks_uid;
        sb->st_gid = ks->ks_gid;
        sb->st_mode = S_IFREG | ks->ks_mode;            /* XXX */
        mtx_unlock(&sem_lock);

        return (0);
}

static int
ksem_chmod(struct file *fp, mode_t mode, struct ucred *active_cred,
    struct thread *td)
{
        struct ksem *ks;
        int error;

        error = 0;
        ks = fp->f_data;
        mtx_lock(&sem_lock);
#ifdef MAC
        error = mac_posixsem_check_setmode(active_cred, ks, mode);
        if (error != 0)
                goto out;
#endif
        error = vaccess(VREG, ks->ks_mode, ks->ks_uid, ks->ks_gid, VADMIN,
            active_cred, NULL);
        if (error != 0)
                goto out;
        ks->ks_mode = mode & ACCESSPERMS;
out:
        mtx_unlock(&sem_lock);
        return (error);
}

static int
ksem_chown(struct file *fp, uid_t uid, gid_t gid, struct ucred *active_cred,
    struct thread *td)
{
        struct ksem *ks;
        int error;

        error = 0;
        ks = fp->f_data;
        mtx_lock(&sem_lock);
#ifdef MAC
        error = mac_posixsem_check_setowner(active_cred, ks, uid, gid);
        if (error != 0)
                goto out;
#endif
        if (uid == (uid_t)-1)
                uid = ks->ks_uid;
        if (gid == (gid_t)-1)
                 gid = ks->ks_gid;
        if (((uid != ks->ks_uid && uid != active_cred->cr_uid) ||
            (gid != ks->ks_gid && !groupmember(gid, active_cred))) &&
            (error = priv_check_cred(active_cred, PRIV_VFS_CHOWN, 0)))
                goto out;
        ks->ks_uid = uid;
        ks->ks_gid = gid;
out:
        mtx_unlock(&sem_lock);
        return (error);
}

static int
ksem_closef(struct file *fp, struct thread *td)
{
        struct ksem *ks;

        ks = fp->f_data;
        fp->f_data = NULL;
        ksem_drop(ks);

        return (0);
}

/*
 * ksem object management including creation and reference counting
 * routines.
 */
static struct ksem *
ksem_alloc(struct ucred *ucred, mode_t mode, unsigned int value)
{
        struct ksem *ks;

        mtx_lock(&ksem_count_lock);
        if (nsems == p31b_getcfg(CTL_P1003_1B_SEM_NSEMS_MAX) || ksem_dead) {
                mtx_unlock(&ksem_count_lock);
                return (NULL);
        }
        nsems++;
        mtx_unlock(&ksem_count_lock);
        ks = malloc(sizeof(*ks), M_KSEM, M_WAITOK | M_ZERO);
        ks->ks_uid = ucred->cr_uid;
        ks->ks_gid = ucred->cr_gid;
        ks->ks_mode = mode;
        ks->ks_value = value;
        cv_init(&ks->ks_cv, "ksem");
        vfs_timestamp(&ks->ks_birthtime);
        ks->ks_atime = ks->ks_mtime = ks->ks_ctime = ks->ks_birthtime;
        refcount_init(&ks->ks_ref, 1);
#ifdef MAC
        mac_posixsem_init(ks);
        mac_posixsem_create(ucred, ks);
#endif

        return (ks);
}

static struct ksem *
ksem_hold(struct ksem *ks)
{

        refcount_acquire(&ks->ks_ref);
        return (ks);
}

static void
ksem_drop(struct ksem *ks)
{

        if (refcount_release(&ks->ks_ref)) {
#ifdef MAC
                mac_posixsem_destroy(ks);
#endif
                cv_destroy(&ks->ks_cv);
                free(ks, M_KSEM);
                mtx_lock(&ksem_count_lock);
                nsems--;
                mtx_unlock(&ksem_count_lock);
        }
}

/*
 * Determine if the credentials have sufficient permissions for read
 * and write access.
 */
static int
ksem_access(struct ksem *ks, struct ucred *ucred)
{
        int error;

        error = vaccess(VREG, ks->ks_mode, ks->ks_uid, ks->ks_gid,
            VREAD | VWRITE, ucred, NULL);
        if (error)
                error = priv_check_cred(ucred, PRIV_SEM_WRITE, 0);
        return (error);
}

/*
 * Dictionary management.  We maintain an in-kernel dictionary to map
 * paths to semaphore objects.  We use the FNV hash on the path to
 * store the mappings in a hash table.
 */
static struct ksem *
ksem_lookup(char *path, Fnv32_t fnv)
{
        struct ksem_mapping *map;

        LIST_FOREACH(map, KSEM_HASH(fnv), km_link) {
                if (map->km_fnv != fnv)
                        continue;
                if (strcmp(map->km_path, path) == 0)
                        return (map->km_ksem);
        }

        return (NULL);
}

static void
ksem_insert(char *path, Fnv32_t fnv, struct ksem *ks)
{
        struct ksem_mapping *map;

        map = malloc(sizeof(struct ksem_mapping), M_KSEM, M_WAITOK);
        map->km_path = path;
        map->km_fnv = fnv;
        map->km_ksem = ksem_hold(ks);
        ks->ks_path = path;
        LIST_INSERT_HEAD(KSEM_HASH(fnv), map, km_link);
}

static int
ksem_remove(char *path, Fnv32_t fnv, struct ucred *ucred)
{
        struct ksem_mapping *map;
        int error;

        LIST_FOREACH(map, KSEM_HASH(fnv), km_link) {
                if (map->km_fnv != fnv)
                        continue;
                if (strcmp(map->km_path, path) == 0) {
#ifdef MAC
                        error = mac_posixsem_check_unlink(ucred, map->km_ksem);
                        if (error)
                                return (error);
#endif
                        error = ksem_access(map->km_ksem, ucred);
                        if (error)
                                return (error);
                        map->km_ksem->ks_path = NULL;
                        LIST_REMOVE(map, km_link);
                        ksem_drop(map->km_ksem);
                        free(map->km_path, M_KSEM);
                        free(map, M_KSEM);
                        return (0);
                }
        }

        return (ENOENT);
}

static void
ksem_info_impl(struct ksem *ks, char *path, size_t size, uint32_t *value)
{

        if (ks->ks_path == NULL)
                return;
        sx_slock(&ksem_dict_lock);
        if (ks->ks_path != NULL)
                strlcpy(path, ks->ks_path, size);
        if (value != NULL)
                *value = ks->ks_value;
        sx_sunlock(&ksem_dict_lock);
}

static int
ksem_create_copyout_semid(struct thread *td, semid_t *semidp, int fd,
    int compat32)
{
        semid_t semid;
#ifdef COMPAT_32BIT
        int32_t semid32;
#endif
        void *ptr;
        size_t ptrs;

#ifdef COMPAT_32BIT
        if (compat32) {
                semid32 = fd;
                ptr = &semid32;
                ptrs = sizeof(semid32);
        } else {
#endif
                semid = fd;
                ptr = &semid;
                ptrs = sizeof(semid);
                compat32 = 0; /* silence gcc */
#ifdef COMPAT_32BIT
        }
#endif

        return (copyout(ptr, semidp, ptrs));
}

/* Other helper routines. */
static int
ksem_create(struct thread *td, const char *name, semid_t *semidp, mode_t mode,
    unsigned int value, int flags, int compat32)
{
        struct filedesc *fdp;
        struct ksem *ks;
        struct file *fp;
        char *path;
        Fnv32_t fnv;
        int error, fd;

        if (value > SEM_VALUE_MAX)
                return (EINVAL);

        fdp = td->td_proc->p_fd;
        mode = (mode & ~fdp->fd_cmask) & ACCESSPERMS;
        error = falloc(td, &fp, &fd, O_CLOEXEC);
        if (error) {
                if (name == NULL)
                        error = ENOSPC;
                return (error);
        }

        /*
         * Go ahead and copyout the file descriptor now.  This is a bit
         * premature, but it is a lot easier to handle errors as opposed
         * to later when we've possibly created a new semaphore, etc.
         */
        error = ksem_create_copyout_semid(td, semidp, fd, compat32);
        if (error) {
                fdclose(fdp, fp, fd, td);
                fdrop(fp, td);
                return (error);
        }

        if (name == NULL) {
                /* Create an anonymous semaphore. */
                ks = ksem_alloc(td->td_ucred, mode, value);
                if (ks == NULL)
                        error = ENOSPC;
                else
                        ks->ks_flags |= KS_ANONYMOUS;
        } else {
                path = malloc(MAXPATHLEN, M_KSEM, M_WAITOK);
                error = copyinstr(name, path, MAXPATHLEN, NULL);

                /* Require paths to start with a '/' character. */
                if (error == 0 && path[0] != '/')
                        error = EINVAL;
                if (error) {
                        fdclose(fdp, fp, fd, td);
                        fdrop(fp, td);
                        free(path, M_KSEM);
                        return (error);
                }

                fnv = fnv_32_str(path, FNV1_32_INIT);
                sx_xlock(&ksem_dict_lock);
                ks = ksem_lookup(path, fnv);
                if (ks == NULL) {
                        /* Object does not exist, create it if requested. */
                        if (flags & O_CREAT) {
                                ks = ksem_alloc(td->td_ucred, mode, value);
                                if (ks == NULL)
                                        error = ENFILE;
                                else {
                                        ksem_insert(path, fnv, ks);
                                        path = NULL;
                                }
                        } else
                                error = ENOENT;
                } else {
                        /*
                         * Object already exists, obtain a new
                         * reference if requested and permitted.
                         */
                        if ((flags & (O_CREAT | O_EXCL)) ==
                            (O_CREAT | O_EXCL))
                                error = EEXIST;
                        else {
#ifdef MAC
                                error = mac_posixsem_check_open(td->td_ucred,
                                    ks);
                                if (error == 0)
#endif
                                error = ksem_access(ks, td->td_ucred);
                        }
                        if (error == 0)
                                ksem_hold(ks);
#ifdef INVARIANTS
                        else
                                ks = NULL;
#endif
                }
                sx_xunlock(&ksem_dict_lock);
                if (path)
                        free(path, M_KSEM);
        }

        if (error) {
                KASSERT(ks == NULL, ("ksem_create error with a ksem"));
                fdclose(fdp, fp, fd, td);
                fdrop(fp, td);
                return (error);
        }
        KASSERT(ks != NULL, ("ksem_create w/o a ksem"));

        finit(fp, FREAD | FWRITE, DTYPE_SEM, ks, &ksem_ops);

        fdrop(fp, td);

        return (0);
}

static int
ksem_get(struct thread *td, semid_t id, cap_rights_t rights, struct file **fpp)
{
        struct ksem *ks;
        struct file *fp;
        int error;

        error = fget(td, id, rights, &fp);
        if (error)
                return (EINVAL);
        if (fp->f_type != DTYPE_SEM) {
                fdrop(fp, td);
                return (EINVAL);
        }
        ks = fp->f_data;
        if (ks->ks_flags & KS_DEAD) {
                fdrop(fp, td);
                return (EINVAL);
        }
        *fpp = fp;
        return (0);
}

/* System calls. */
#ifndef _SYS_SYSPROTO_H_
struct ksem_init_args {
        unsigned int    value;
        semid_t         *idp;
};
#endif
int
sys_ksem_init(struct thread *td, struct ksem_init_args *uap)
{

        return (ksem_create(td, NULL, uap->idp, S_IRWXU | S_IRWXG, uap->value,
            0, 0));
}

#ifndef _SYS_SYSPROTO_H_
struct ksem_open_args {
        char            *name;
        int             oflag;
        mode_t          mode;
        unsigned int    value;
        semid_t         *idp;   
};
#endif
int
sys_ksem_open(struct thread *td, struct ksem_open_args *uap)
{

        DP((">>> ksem_open start, pid=%d\n", (int)td->td_proc->p_pid));

        if ((uap->oflag & ~(O_CREAT | O_EXCL)) != 0)
                return (EINVAL);
        return (ksem_create(td, uap->name, uap->idp, uap->mode, uap->value,
            uap->oflag, 0));
}

#ifndef _SYS_SYSPROTO_H_
struct ksem_unlink_args {
        char            *name;
};
#endif
int
sys_ksem_unlink(struct thread *td, struct ksem_unlink_args *uap)
{
        char *path;
        Fnv32_t fnv;
        int error;

        path = malloc(MAXPATHLEN, M_TEMP, M_WAITOK);
        error = copyinstr(uap->name, path, MAXPATHLEN, NULL);
        if (error) {
                free(path, M_TEMP);
                return (error);
        }

        fnv = fnv_32_str(path, FNV1_32_INIT);
        sx_xlock(&ksem_dict_lock);
        error = ksem_remove(path, fnv, td->td_ucred);
        sx_xunlock(&ksem_dict_lock);
        free(path, M_TEMP);

        return (error);
}

#ifndef _SYS_SYSPROTO_H_
struct ksem_close_args {
        semid_t         id;
};
#endif
int
sys_ksem_close(struct thread *td, struct ksem_close_args *uap)
{
        struct ksem *ks;
        struct file *fp;
        int error;

        /* No capability rights required to close a semaphore. */
        error = ksem_get(td, uap->id, 0, &fp);
        if (error)
                return (error);
        ks = fp->f_data;
        if (ks->ks_flags & KS_ANONYMOUS) {
                fdrop(fp, td);
                return (EINVAL);
        }
        error = kern_close(td, uap->id);
        fdrop(fp, td);
        return (error);
}

#ifndef _SYS_SYSPROTO_H_
struct ksem_post_args {
        semid_t id;
};
#endif
int
sys_ksem_post(struct thread *td, struct ksem_post_args *uap)
{
        struct file *fp;
        struct ksem *ks;
        int error;

        error = ksem_get(td, uap->id, CAP_SEM_POST, &fp);
        if (error)
                return (error);
        ks = fp->f_data;

        mtx_lock(&sem_lock);
#ifdef MAC
        error = mac_posixsem_check_post(td->td_ucred, fp->f_cred, ks);
        if (error)
                goto err;
#endif
        if (ks->ks_value == SEM_VALUE_MAX) {
                error = EOVERFLOW;
                goto err;
        }
        ++ks->ks_value;
        if (ks->ks_waiters > 0)
                cv_signal(&ks->ks_cv);
        error = 0;
        vfs_timestamp(&ks->ks_ctime);
err:
        mtx_unlock(&sem_lock);
        fdrop(fp, td);
        return (error);
}

#ifndef _SYS_SYSPROTO_H_
struct ksem_wait_args {
        semid_t         id;
};
#endif
int
sys_ksem_wait(struct thread *td, struct ksem_wait_args *uap)
{

        return (kern_sem_wait(td, uap->id, 0, NULL));
}

#ifndef _SYS_SYSPROTO_H_
struct ksem_timedwait_args {
        semid_t         id;
        const struct timespec *abstime;
};
#endif
int
sys_ksem_timedwait(struct thread *td, struct ksem_timedwait_args *uap)
{
        struct timespec abstime;
        struct timespec *ts;
        int error;

        /*
         * We allow a null timespec (wait forever).
         */
        if (uap->abstime == NULL)
                ts = NULL;
        else {
                error = copyin(uap->abstime, &abstime, sizeof(abstime));
                if (error != 0)
                        return (error);
                if (abstime.tv_nsec >= 1000000000 || abstime.tv_nsec < 0)
                        return (EINVAL);
                ts = &abstime;
        }
        return (kern_sem_wait(td, uap->id, 0, ts));
}

#ifndef _SYS_SYSPROTO_H_
struct ksem_trywait_args {
        semid_t         id;
};
#endif
int
sys_ksem_trywait(struct thread *td, struct ksem_trywait_args *uap)
{

        return (kern_sem_wait(td, uap->id, 1, NULL));
}

static int
kern_sem_wait(struct thread *td, semid_t id, int tryflag,
    struct timespec *abstime)
{
        struct timespec ts1, ts2;
        struct timeval tv;
        struct file *fp;
        struct ksem *ks;
        int error;

        DP((">>> kern_sem_wait entered! pid=%d\n", (int)td->td_proc->p_pid));
        error = ksem_get(td, id, CAP_SEM_WAIT, &fp);
        if (error)
                return (error);
        ks = fp->f_data;
        mtx_lock(&sem_lock);
        DP((">>> kern_sem_wait critical section entered! pid=%d\n",
            (int)td->td_proc->p_pid));
#ifdef MAC
        error = mac_posixsem_check_wait(td->td_ucred, fp->f_cred, ks);
        if (error) {
                DP(("kern_sem_wait mac failed\n"));
                goto err;
        }
#endif
        DP(("kern_sem_wait value = %d, tryflag %d\n", ks->ks_value, tryflag));
        vfs_timestamp(&ks->ks_atime);
        while (ks->ks_value == 0) {
                ks->ks_waiters++;
                if (tryflag != 0)
                        error = EAGAIN;
                else if (abstime == NULL)
                        error = cv_wait_sig(&ks->ks_cv, &sem_lock);
                else {
                        for (;;) {
                                ts1 = *abstime;
                                getnanotime(&ts2);
                                timespecsub(&ts1, &ts2);
                                TIMESPEC_TO_TIMEVAL(&tv, &ts1);
                                if (tv.tv_sec < 0) {
                                        error = ETIMEDOUT;
                                        break;
                                }
                                error = cv_timedwait_sig(&ks->ks_cv,
                                    &sem_lock, tvtohz(&tv));
                                if (error != EWOULDBLOCK)
                                        break;
                        }
                }
                ks->ks_waiters--;
                if (error)
                        goto err;
        }
        ks->ks_value--;
        DP(("kern_sem_wait value post-decrement = %d\n", ks->ks_value));
        error = 0;
err:
        mtx_unlock(&sem_lock);
        fdrop(fp, td);
        DP(("<<< kern_sem_wait leaving, pid=%d, error = %d\n",
            (int)td->td_proc->p_pid, error));
        return (error);
}

#ifndef _SYS_SYSPROTO_H_
struct ksem_getvalue_args {
        semid_t         id;
        int             *val;
};
#endif
int
sys_ksem_getvalue(struct thread *td, struct ksem_getvalue_args *uap)
{
        struct file *fp;
        struct ksem *ks;
        int error, val;

        error = ksem_get(td, uap->id, CAP_SEM_GETVALUE, &fp);
        if (error)
                return (error);
        ks = fp->f_data;

        mtx_lock(&sem_lock);
#ifdef MAC
        error = mac_posixsem_check_getvalue(td->td_ucred, fp->f_cred, ks);
        if (error) {
                mtx_unlock(&sem_lock);
                fdrop(fp, td);
                return (error);
        }
#endif
        val = ks->ks_value;
        vfs_timestamp(&ks->ks_atime);
        mtx_unlock(&sem_lock);
        fdrop(fp, td);
        error = copyout(&val, uap->val, sizeof(val));
        return (error);
}

#ifndef _SYS_SYSPROTO_H_
struct ksem_destroy_args {
        semid_t         id;
};
#endif
int
sys_ksem_destroy(struct thread *td, struct ksem_destroy_args *uap)
{
        struct file *fp;
        struct ksem *ks;
        int error;

        /* No capability rights required to close a semaphore. */
        error = ksem_get(td, uap->id, 0, &fp);
        if (error)
                return (error);
        ks = fp->f_data;
        if (!(ks->ks_flags & KS_ANONYMOUS)) {
                fdrop(fp, td);
                return (EINVAL);
        }
        mtx_lock(&sem_lock);
        if (ks->ks_waiters != 0) {
                mtx_unlock(&sem_lock);
                error = EBUSY;
                goto err;
        }
        ks->ks_flags |= KS_DEAD;
        mtx_unlock(&sem_lock);

        error = kern_close(td, uap->id);
err:
        fdrop(fp, td);
        return (error);
}

static struct syscall_helper_data ksem_syscalls[] = {
        SYSCALL_INIT_HELPER(ksem_init),
        SYSCALL_INIT_HELPER(ksem_open),
        SYSCALL_INIT_HELPER(ksem_unlink),
        SYSCALL_INIT_HELPER(ksem_close),
        SYSCALL_INIT_HELPER(ksem_post),
        SYSCALL_INIT_HELPER(ksem_wait),
        SYSCALL_INIT_HELPER(ksem_timedwait),
        SYSCALL_INIT_HELPER(ksem_trywait),
        SYSCALL_INIT_HELPER(ksem_getvalue),
        SYSCALL_INIT_HELPER(ksem_destroy),
        SYSCALL_INIT_LAST
};

#ifdef COMPAT_32BIT
#include <compat/compat32bit/compat32bit.h>
#include <compat/compat32bit/compat32bit_proto.h>
#include <compat/compat32bit/compat32bit_signal.h>
#include <compat/compat32bit/compat32bit_syscall.h>
#include <compat/compat32bit/compat32bit_util.h>

int
compat32bit_ksem_init(struct thread *td, struct compat32bit_ksem_init_args *uap)
{

        return (ksem_create(td, NULL, uap->idp, S_IRWXU | S_IRWXG, uap->value,
            0, 1));
}

int
compat32bit_ksem_open(struct thread *td, struct compat32bit_ksem_open_args *uap)
{

        if ((uap->oflag & ~(O_CREAT | O_EXCL)) != 0)
                return (EINVAL);
        return (ksem_create(td, uap->name, uap->idp, uap->mode, uap->value,
            uap->oflag, 1));
}

int
compat32bit_ksem_timedwait(struct thread *td,
    struct compat32bit_ksem_timedwait_args *uap)
{
        struct timespec32 abstime32;
        struct timespec *ts, abstime;
        int error;

        /*
         * We allow a null timespec (wait forever).
         */
        if (uap->abstime == NULL)
                ts = NULL;
        else {
                error = copyin(uap->abstime, &abstime32, sizeof(abstime32));
                if (error != 0)
                        return (error);
                CP(abstime32, abstime, tv_sec);
                CP(abstime32, abstime, tv_nsec);
                if (abstime.tv_nsec >= 1000000000 || abstime.tv_nsec < 0)
                        return (EINVAL);
                ts = &abstime;
        }
        return (kern_sem_wait(td, uap->id, 0, ts));
}

static struct syscall_helper_data ksem32_syscalls[] = {
        SYSCALL32_INIT_HELPER(compat32bit_ksem_init),
        SYSCALL32_INIT_HELPER(compat32bit_ksem_open),
        SYSCALL32_INIT_HELPER_COMPAT(ksem_unlink),
        SYSCALL32_INIT_HELPER_COMPAT(ksem_close),
        SYSCALL32_INIT_HELPER_COMPAT(ksem_post),
        SYSCALL32_INIT_HELPER_COMPAT(ksem_wait),
        SYSCALL32_INIT_HELPER(compat32bit_ksem_timedwait),
        SYSCALL32_INIT_HELPER_COMPAT(ksem_trywait),
        SYSCALL32_INIT_HELPER_COMPAT(ksem_getvalue),
        SYSCALL32_INIT_HELPER_COMPAT(ksem_destroy),
        SYSCALL_INIT_LAST
};
#endif

static int
ksem_module_init(void)
{
        int error;

        mtx_init(&sem_lock, "sem", NULL, MTX_DEF);
        mtx_init(&ksem_count_lock, "ksem count", NULL, MTX_DEF);
        sx_init(&ksem_dict_lock, "ksem dictionary");
        ksem_dictionary = hashinit(1024, M_KSEM, &ksem_hash);
        p31b_setcfg(CTL_P1003_1B_SEMAPHORES, 200112L);
        p31b_setcfg(CTL_P1003_1B_SEM_NSEMS_MAX, SEM_MAX);
        p31b_setcfg(CTL_P1003_1B_SEM_VALUE_MAX, SEM_VALUE_MAX);
        ksem_info = ksem_info_impl;

        error = syscall_helper_register(ksem_syscalls);
        if (error)
                return (error);
#ifdef COMPAT_32BIT
        error = syscall32_helper_register(ksem32_syscalls);
        if (error)
                return (error);
#endif
        return (0);
}

static void
ksem_module_destroy(void)
{

#ifdef COMPAT_32BIT
        syscall32_helper_unregister(ksem32_syscalls);
#endif
        syscall_helper_unregister(ksem_syscalls);

        ksem_info = NULL;
        p31b_setcfg(CTL_P1003_1B_SEMAPHORES, 0);
        hashdestroy(ksem_dictionary, M_KSEM, ksem_hash);
        sx_destroy(&ksem_dict_lock);
        mtx_destroy(&ksem_count_lock);
        mtx_destroy(&sem_lock);
        p31b_unsetcfg(CTL_P1003_1B_SEM_VALUE_MAX);
        p31b_unsetcfg(CTL_P1003_1B_SEM_NSEMS_MAX);
}

static int
sem_modload(struct module *module, int cmd, void *arg)
{
        int error = 0;

        switch (cmd) {
        case MOD_LOAD:
                error = ksem_module_init();
                if (error)
                        ksem_module_destroy();
                break;

        case MOD_UNLOAD:
                mtx_lock(&ksem_count_lock);
                if (nsems != 0) {
                        error = EOPNOTSUPP;
                        mtx_unlock(&ksem_count_lock);
                        break;
                }
                ksem_dead = 1;
                mtx_unlock(&ksem_count_lock);
                ksem_module_destroy();
                break;

        case MOD_SHUTDOWN:
                break;
        default:
                error = EINVAL;
                break;
        }
        return (error);
}

static moduledata_t sem_mod = {
        "sem",
        &sem_modload,
        NULL
};

DECLARE_MODULE(sem, sem_mod, SI_SUB_SYSV_SEM, SI_ORDER_FIRST);
MODULE_VERSION(sem, 1);