freebsd-dev/sys/kern/uipc_sem.c
John Baldwin 6bc1e9cd84 Rework the lifetime management of the kernel implementation of POSIX
semaphores.  Specifically, semaphores are now represented as new file
descriptor type that is set to close on exec.  This removes the need for
all of the manual process reference counting (and fork, exec, and exit
event handlers) as the normal file descriptor operations handle all of
that for us nicely.  It is also suggested as one possible implementation
in the spec and at least one other OS (OS X) uses this approach.

Some bugs that were fixed as a result include:
- References to a named semaphore whose name is removed still work after
  the sem_unlink() operation.  Prior to this patch, if a semaphore's name
  was removed, valid handles from sem_open() would get EINVAL errors from
  sem_getvalue(), sem_post(), etc.  This fixes that.
- Unnamed semaphores created with sem_init() were not cleaned up when a
  process exited or exec'd.  They were only cleaned up if the process
  did an explicit sem_destroy().  This could result in a leak of semaphore
  objects that could never be cleaned up.
- On the other hand, if another process guessed the id (kernel pointer to
  'struct ksem' of an unnamed semaphore (created via sem_init)) and had
  write access to the semaphore based on UID/GID checks, then that other
  process could manipulate the semaphore via sem_destroy(), sem_post(),
  sem_wait(), etc.
- As part of the permission check (UID/GID), the umask of the proces
  creating the semaphore was not honored.  Thus if your umask denied group
  read/write access but the explicit mode in the sem_init() call allowed
  it, the semaphore would be readable/writable by other users in the
  same group, for example.  This includes access via the previous bug.
- If the module refused to unload because there were active semaphores,
  then it might have deregistered one or more of the semaphore system
  calls before it noticed that there was a problem.  I'm not sure if
  this actually happened as the order that modules are discovered by the
  kernel linker depends on how the actual .ko file is linked.  One can
  make the order deterministic by using a single module with a mod_event
  handler that explicitly registers syscalls (and deregisters during
  unload after any checks).  This also fixes a race where even if the
  sem_module unloaded first it would have destroyed locks that the
  syscalls might be trying to access if they are still executing when
  they are unloaded.

  XXX: By the way, deregistering system calls doesn't do any blocking
  to drain any threads from the calls.
- Some minor fixes to errno values on error.  For example, sem_init()
  isn't documented to return ENFILE or EMFILE if we run out of semaphores
  the way that sem_open() can.  Instead, it should return ENOSPC in that
  case.

Other changes:
- Kernel semaphores now use a hash table to manage the namespace of
  named semaphores nearly in a similar fashion to the POSIX shared memory
  object file descriptors.  Kernel semaphores can now also have names
  longer than 14 chars (up to MAXPATHLEN) and can include subdirectories
  in their pathname.
- The UID/GID permission checks for access to a named semaphore are now
  done via vaccess() rather than a home-rolled set of checks.
- Now that kernel semaphores have an associated file object, the various
  MAC checks for POSIX semaphores accept both a file credential and an
  active credential.  There is also a new posixsem_check_stat() since it
  is possible to fstat() a semaphore file descriptor.
- A small set of regression tests (using the ksem API directly) is present
  in src/tools/regression/posixsem.

Reported by:	kris (1)
Tested by:	kris
Reviewed by:	rwatson (lightly)
MFC after:	1 month
2008-06-27 05:39:04 +00:00

951 lines
20 KiB
C

/*-
* 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("$FreeBSD$");
#include "opt_mac.h"
#include "opt_posix.h"
#include <sys/param.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/_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>
/*
* TODO
*
* - Resource limits?
* - Update fstat(1)
* - 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);
static void ksem_drop(struct ksem *ks);
static int ksem_get(struct thread *td, semid_t id, 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;
/* 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_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));
sb->st_mode = S_IFREG | ks->ks_mode; /* XXX */
sb->st_atimespec = ks->ks_atime;
sb->st_ctimespec = ks->ks_ctime;
sb->st_mtimespec = ks->ks_mtime;
sb->st_birthtimespec = ks->ks_birthtime;
sb->st_uid = ks->ks_uid;
sb->st_gid = ks->ks_gid;
return (0);
}
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);
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);
LIST_REMOVE(map, km_link);
ksem_drop(map->km_ksem);
free(map->km_path, M_KSEM);
free(map, M_KSEM);
return (0);
}
}
return (ENOENT);
}
/* Other helper routines. */
static int
ksem_create(struct thread *td, const char *name, semid_t *semidp, mode_t mode,
unsigned int value, int flags)
{
struct filedesc *fdp;
struct ksem *ks;
struct file *fp;
char *path;
semid_t semid;
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);
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.
*/
semid = fd;
error = copyout(&semid, semidp, sizeof(semid));
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);
FILEDESC_XLOCK(fdp);
if (fdp->fd_ofiles[fd] == fp)
fdp->fd_ofileflags[fd] |= UF_EXCLOSE;
FILEDESC_XUNLOCK(fdp);
fdrop(fp, td);
return (0);
}
static int
ksem_get(struct thread *td, semid_t id, struct file **fpp)
{
struct ksem *ks;
struct file *fp;
int error;
error = fget(td, id, &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
ksem_init(struct thread *td, struct ksem_init_args *uap)
{
return (ksem_create(td, NULL, uap->idp, S_IRWXU | S_IRWXG, uap->value,
0));
}
#ifndef _SYS_SYSPROTO_H_
struct ksem_open_args {
char *name;
int oflag;
mode_t mode;
unsigned int value;
semid_t *idp;
};
#endif
int
ksem_open(struct thread *td, struct 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));
}
#ifndef _SYS_SYSPROTO_H_
struct ksem_unlink_args {
char *name;
};
#endif
int
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
ksem_close(struct thread *td, struct ksem_close_args *uap)
{
struct ksem *ks;
struct file *fp;
int error;
error = ksem_get(td, uap->id, &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
ksem_post(struct thread *td, struct ksem_post_args *uap)
{
struct file *fp;
struct ksem *ks;
int error;
error = ksem_get(td, uap->id, &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
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
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
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!\n"));
error = ksem_get(td, id, &fp);
if (error)
return (error);
ks = fp->f_data;
mtx_lock(&sem_lock);
#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);
if (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--;
error = 0;
err:
mtx_unlock(&sem_lock);
fdrop(fp, td);
DP(("<<< kern_sem_wait leaving, error = %d\n", error));
return (error);
}
#ifndef _SYS_SYSPROTO_H_
struct ksem_getvalue_args {
semid_t id;
int *val;
};
#endif
int
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, &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
ksem_destroy(struct thread *td, struct ksem_destroy_args *uap)
{
struct file *fp;
struct ksem *ks;
int error;
error = ksem_get(td, uap->id, &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);
}
#define SYSCALL_DATA(syscallname) \
static int syscallname##_syscall = SYS_##syscallname; \
static int syscallname##_registered; \
static struct sysent syscallname##_old_sysent; \
MAKE_SYSENT(syscallname);
#define SYSCALL_REGISTER(syscallname) do { \
error = syscall_register(& syscallname##_syscall, \
& syscallname##_sysent, & syscallname##_old_sysent); \
if (error) \
return (error); \
syscallname##_registered = 1; \
} while(0)
#define SYSCALL_DEREGISTER(syscallname) do { \
if (syscallname##_registered) { \
syscallname##_registered = 0; \
syscall_deregister(& syscallname##_syscall, \
& syscallname##_old_sysent); \
} \
} while(0)
SYSCALL_DATA(ksem_init);
SYSCALL_DATA(ksem_open);
SYSCALL_DATA(ksem_unlink);
SYSCALL_DATA(ksem_close);
SYSCALL_DATA(ksem_post);
SYSCALL_DATA(ksem_wait);
SYSCALL_DATA(ksem_timedwait);
SYSCALL_DATA(ksem_trywait);
SYSCALL_DATA(ksem_getvalue);
SYSCALL_DATA(ksem_destroy);
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_SEM_NSEMS_MAX, SEM_MAX);
p31b_setcfg(CTL_P1003_1B_SEM_VALUE_MAX, SEM_VALUE_MAX);
SYSCALL_REGISTER(ksem_init);
SYSCALL_REGISTER(ksem_open);
SYSCALL_REGISTER(ksem_unlink);
SYSCALL_REGISTER(ksem_close);
SYSCALL_REGISTER(ksem_post);
SYSCALL_REGISTER(ksem_wait);
SYSCALL_REGISTER(ksem_timedwait);
SYSCALL_REGISTER(ksem_trywait);
SYSCALL_REGISTER(ksem_getvalue);
SYSCALL_REGISTER(ksem_destroy);
return (0);
}
static void
ksem_module_destroy(void)
{
SYSCALL_DEREGISTER(ksem_init);
SYSCALL_DEREGISTER(ksem_open);
SYSCALL_DEREGISTER(ksem_unlink);
SYSCALL_DEREGISTER(ksem_close);
SYSCALL_DEREGISTER(ksem_post);
SYSCALL_DEREGISTER(ksem_wait);
SYSCALL_DEREGISTER(ksem_timedwait);
SYSCALL_DEREGISTER(ksem_trywait);
SYSCALL_DEREGISTER(ksem_getvalue);
SYSCALL_DEREGISTER(ksem_destroy);
hashdestroy(ksem_dictionary, M_KSEM, ksem_hash);
sx_destroy(&ksem_dict_lock);
mtx_destroy(&ksem_count_lock);
mtx_destroy(&sem_lock);
}
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);