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freebsd/sys/kern/uipc_sem.c
Robert Watson e2f7a83d6b In sem_forkhook(), don't attempt to generate a copy of the process semaphore 
list on fork() if the process doesn't actually have references to any
semaphores.  This avoids extra work, as well as potentially asking to
allocate storage for 0 references.

Found by:	avatar
MFC after:	1 week
2005-06-08 07:29:22 +00:00

1054 lines
23 KiB
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("$FreeBSD$");
#include "opt_mac.h"
#include "opt_posix.h"
#include <sys/param.h>
#include <sys/systm.h>
#include <sys/sysproto.h>
#include <sys/eventhandler.h>
#include <sys/kernel.h>
#include <sys/proc.h>
#include <sys/lock.h>
#include <sys/mutex.h>
#include <sys/module.h>
#include <sys/condvar.h>
#include <sys/sem.h>
#include <sys/uio.h>
#include <sys/syscall.h>
#include <sys/stat.h>
#include <sys/sysent.h>
#include <sys/sysctl.h>
#include <sys/time.h>
#include <sys/mac.h>
#include <sys/malloc.h>
#include <sys/fcntl.h>
#include <posix4/ksem.h>
#include <posix4/posix4.h>
#include <posix4/semaphore.h>
#include <posix4/_semaphore.h>
static int sem_count_proc(struct proc *p);
static struct ksem *sem_lookup_byname(const char *name);
static int sem_create(struct thread *td, const char *name,
struct ksem **ksret, mode_t mode, unsigned int value);
static void sem_free(struct ksem *ksnew);
static int sem_perm(struct thread *td, struct ksem *ks);
static void sem_enter(struct proc *p, struct ksem *ks);
static int sem_leave(struct proc *p, struct ksem *ks);
static void sem_exithook(void *arg, struct proc *p);
static void sem_forkhook(void *arg, struct proc *p1, struct proc *p2,
int flags);
static int sem_hasopen(struct thread *td, struct ksem *ks);
static int kern_sem_close(struct thread *td, semid_t id);
static int kern_sem_post(struct thread *td, semid_t id);
static int kern_sem_wait(struct thread *td, semid_t id, int tryflag,
struct timespec *abstime);
static int kern_sem_init(struct thread *td, int dir, unsigned int value,
semid_t *idp);
static int kern_sem_open(struct thread *td, int dir, const char *name,
int oflag, mode_t mode, unsigned int value, semid_t *idp);
static int kern_sem_unlink(struct thread *td, const char *name);
#ifndef SEM_MAX
#define SEM_MAX 30
#endif
#define SEM_MAX_NAMELEN 14
#define SEM_TO_ID(x) ((intptr_t)(x))
#define ID_TO_SEM(x) id_to_sem(x)
/*
* available semaphores go here, this includes sem_init and any semaphores
* created via sem_open that have not yet been unlinked.
*/
LIST_HEAD(, ksem) ksem_head = LIST_HEAD_INITIALIZER(&ksem_head);
/*
* semaphores still in use but have been sem_unlink()'d go here.
*/
LIST_HEAD(, ksem) ksem_deadhead = LIST_HEAD_INITIALIZER(&ksem_deadhead);
static struct mtx sem_lock;
static MALLOC_DEFINE(M_SEM, "sems", "semaphore data");
static int nsems = 0;
SYSCTL_DECL(_p1003_1b);
SYSCTL_INT(_p1003_1b, OID_AUTO, nsems, CTLFLAG_RD, &nsems, 0, "");
static eventhandler_tag sem_exit_tag, sem_exec_tag, sem_fork_tag;
#ifdef SEM_DEBUG
#define DP(x) printf x
#else
#define DP(x)
#endif
static __inline
void
sem_ref(struct ksem *ks)
{
mtx_assert(&sem_lock, MA_OWNED);
ks->ks_ref++;
DP(("sem_ref: ks = %p, ref = %d\n", ks, ks->ks_ref));
}
static __inline
void
sem_rel(struct ksem *ks)
{
mtx_assert(&sem_lock, MA_OWNED);
DP(("sem_rel: ks = %p, ref = %d\n", ks, ks->ks_ref - 1));
if (--ks->ks_ref == 0)
sem_free(ks);
}
static __inline struct ksem *id_to_sem(semid_t id);
static __inline
struct ksem *
id_to_sem(id)
semid_t id;
{
struct ksem *ks;
mtx_assert(&sem_lock, MA_OWNED);
DP(("id_to_sem: id = %0x,%p\n", id, (struct ksem *)id));
LIST_FOREACH(ks, &ksem_head, ks_entry) {
DP(("id_to_sem: ks = %p\n", ks));
if (ks == (struct ksem *)id)
return (ks);
}
return (NULL);
}
static struct ksem *
sem_lookup_byname(name)
const char *name;
{
struct ksem *ks;
mtx_assert(&sem_lock, MA_OWNED);
LIST_FOREACH(ks, &ksem_head, ks_entry)
if (ks->ks_name != NULL && strcmp(ks->ks_name, name) == 0)
return (ks);
return (NULL);
}
static int
sem_create(td, name, ksret, mode, value)
struct thread *td;
const char *name;
struct ksem **ksret;
mode_t mode;
unsigned int value;
{
struct ksem *ret;
struct proc *p;
struct ucred *uc;
size_t len;
int error;
DP(("sem_create\n"));
p = td->td_proc;
uc = td->td_ucred;
if (value > SEM_VALUE_MAX)
return (EINVAL);
ret = malloc(sizeof(*ret), M_SEM, M_WAITOK | M_ZERO);
if (name != NULL) {
len = strlen(name);
if (len > SEM_MAX_NAMELEN) {
free(ret, M_SEM);
return (ENAMETOOLONG);
}
/* name must start with a '/' but not contain one. */
if (*name != '/' || len < 2 || index(name + 1, '/') != NULL) {
free(ret, M_SEM);
return (EINVAL);
}
ret->ks_name = malloc(len + 1, M_SEM, M_WAITOK);
strcpy(ret->ks_name, name);
} else {
ret->ks_name = NULL;
}
ret->ks_mode = mode;
ret->ks_value = value;
ret->ks_ref = 1;
ret->ks_waiters = 0;
ret->ks_uid = uc->cr_uid;
ret->ks_gid = uc->cr_gid;
ret->ks_onlist = 0;
cv_init(&ret->ks_cv, "sem");
LIST_INIT(&ret->ks_users);
#ifdef MAC
mac_init_posix_sem(ret);
mac_create_posix_sem(uc, ret);
#endif
if (name != NULL)
sem_enter(td->td_proc, ret);
*ksret = ret;
mtx_lock(&sem_lock);
if (nsems >= p31b_getcfg(CTL_P1003_1B_SEM_NSEMS_MAX)) {
sem_leave(td->td_proc, ret);
sem_free(ret);
error = ENFILE;
} else {
nsems++;
error = 0;
}
mtx_unlock(&sem_lock);
return (error);
}
#ifndef _SYS_SYSPROTO_H_
struct ksem_init_args {
unsigned int value;
semid_t *idp;
};
int ksem_init(struct thread *td, struct ksem_init_args *uap);
#endif
int
ksem_init(td, uap)
struct thread *td;
struct ksem_init_args *uap;
{
int error;
error = kern_sem_init(td, UIO_USERSPACE, uap->value, uap->idp);
return (error);
}
static int
kern_sem_init(td, dir, value, idp)
struct thread *td;
int dir;
unsigned int value;
semid_t *idp;
{
struct ksem *ks;
semid_t id;
int error;
error = sem_create(td, NULL, &ks, S_IRWXU | S_IRWXG, value);
if (error)
return (error);
id = SEM_TO_ID(ks);
if (dir == UIO_USERSPACE) {
error = copyout(&id, idp, sizeof(id));
if (error) {
mtx_lock(&sem_lock);
sem_rel(ks);
mtx_unlock(&sem_lock);
return (error);
}
} else {
*idp = id;
}
mtx_lock(&sem_lock);
LIST_INSERT_HEAD(&ksem_head, ks, ks_entry);
ks->ks_onlist = 1;
mtx_unlock(&sem_lock);
return (error);
}
#ifndef _SYS_SYSPROTO_H_
struct ksem_open_args {
char *name;
int oflag;
mode_t mode;
unsigned int value;
semid_t *idp;
};
int ksem_open(struct thread *td, struct ksem_open_args *uap);
#endif
int
ksem_open(td, uap)
struct thread *td;
struct ksem_open_args *uap;
{
char name[SEM_MAX_NAMELEN + 1];
size_t done;
int error;
error = copyinstr(uap->name, name, SEM_MAX_NAMELEN + 1, &done);
if (error)
return (error);
DP((">>> sem_open start\n"));
error = kern_sem_open(td, UIO_USERSPACE,
name, uap->oflag, uap->mode, uap->value, uap->idp);
DP(("<<< sem_open end\n"));
return (error);
}
static int
kern_sem_open(td, dir, name, oflag, mode, value, idp)
struct thread *td;
int dir;
const char *name;
int oflag;
mode_t mode;
unsigned int value;
semid_t *idp;
{
struct ksem *ksnew, *ks;
int error;
semid_t id;
ksnew = NULL;
mtx_lock(&sem_lock);
ks = sem_lookup_byname(name);
/*
* If we found it but O_EXCL is set, error.
*/
if (ks != NULL && (oflag & O_EXCL) != 0) {
mtx_unlock(&sem_lock);
return (EEXIST);
}
/*
* If we didn't find it...
*/
if (ks == NULL) {
/*
* didn't ask for creation? error.
*/
if ((oflag & O_CREAT) == 0) {
mtx_unlock(&sem_lock);
return (ENOENT);
}
/*
* We may block during creation, so drop the lock.
*/
mtx_unlock(&sem_lock);
error = sem_create(td, name, &ksnew, mode, value);
if (error != 0)
return (error);
id = SEM_TO_ID(ksnew);
if (dir == UIO_USERSPACE) {
DP(("about to copyout! %d to %p\n", id, idp));
error = copyout(&id, idp, sizeof(id));
if (error) {
mtx_lock(&sem_lock);
sem_leave(td->td_proc, ksnew);
sem_rel(ksnew);
mtx_unlock(&sem_lock);
return (error);
}
} else {
DP(("about to set! %d to %p\n", id, idp));
*idp = id;
}
/*
* We need to make sure we haven't lost a race while
* allocating during creation.
*/
mtx_lock(&sem_lock);
ks = sem_lookup_byname(name);
if (ks != NULL) {
/* we lost... */
sem_leave(td->td_proc, ksnew);
sem_rel(ksnew);
/* we lost and we can't loose... */
if ((oflag & O_EXCL) != 0) {
mtx_unlock(&sem_lock);
return (EEXIST);
}
} else {
DP(("sem_create: about to add to list...\n"));
LIST_INSERT_HEAD(&ksem_head, ksnew, ks_entry);
DP(("sem_create: setting list bit...\n"));
ksnew->ks_onlist = 1;
DP(("sem_create: done, about to unlock...\n"));
}
} else {
#ifdef MAC
error = mac_check_posix_sem_open(td->td_ucred, ks);
if (error)
goto err_open;
#endif
/*
* if we aren't the creator, then enforce permissions.
*/
error = sem_perm(td, ks);
if (error)
goto err_open;
sem_ref(ks);
mtx_unlock(&sem_lock);
id = SEM_TO_ID(ks);
if (dir == UIO_USERSPACE) {
error = copyout(&id, idp, sizeof(id));
if (error) {
mtx_lock(&sem_lock);
sem_rel(ks);
mtx_unlock(&sem_lock);
return (error);
}
} else {
*idp = id;
}
sem_enter(td->td_proc, ks);
mtx_lock(&sem_lock);
sem_rel(ks);
}
err_open:
mtx_unlock(&sem_lock);
return (error);
}
static int
sem_perm(td, ks)
struct thread *td;
struct ksem *ks;
{
struct ucred *uc;
uc = td->td_ucred;
DP(("sem_perm: uc(%d,%d) ks(%d,%d,%o)\n",
uc->cr_uid, uc->cr_gid,
ks->ks_uid, ks->ks_gid, ks->ks_mode));
if ((uc->cr_uid == ks->ks_uid && (ks->ks_mode & S_IWUSR) != 0) ||
(uc->cr_gid == ks->ks_gid && (ks->ks_mode & S_IWGRP) != 0) ||
(ks->ks_mode & S_IWOTH) != 0 || suser(td) == 0)
return (0);
return (EPERM);
}
static void
sem_free(struct ksem *ks)
{
nsems--;
if (ks->ks_onlist)
LIST_REMOVE(ks, ks_entry);
if (ks->ks_name != NULL)
free(ks->ks_name, M_SEM);
cv_destroy(&ks->ks_cv);
free(ks, M_SEM);
}
static __inline struct kuser *sem_getuser(struct proc *p, struct ksem *ks);
static __inline struct kuser *
sem_getuser(p, ks)
struct proc *p;
struct ksem *ks;
{
struct kuser *k;
LIST_FOREACH(k, &ks->ks_users, ku_next)
if (k->ku_pid == p->p_pid)
return (k);
return (NULL);
}
static int
sem_hasopen(td, ks)
struct thread *td;
struct ksem *ks;
{
return ((ks->ks_name == NULL && sem_perm(td, ks) == 0)
|| sem_getuser(td->td_proc, ks) != NULL);
}
static int
sem_leave(p, ks)
struct proc *p;
struct ksem *ks;
{
struct kuser *k;
DP(("sem_leave: ks = %p\n", ks));
k = sem_getuser(p, ks);
DP(("sem_leave: ks = %p, k = %p\n", ks, k));
if (k != NULL) {
LIST_REMOVE(k, ku_next);
sem_rel(ks);
DP(("sem_leave: about to free k\n"));
free(k, M_SEM);
DP(("sem_leave: returning\n"));
return (0);
}
return (EINVAL);
}
static void
sem_enter(p, ks)
struct proc *p;
struct ksem *ks;
{
struct kuser *ku, *k;
ku = malloc(sizeof(*ku), M_SEM, M_WAITOK);
ku->ku_pid = p->p_pid;
mtx_lock(&sem_lock);
k = sem_getuser(p, ks);
if (k != NULL) {
mtx_unlock(&sem_lock);
free(ku, M_TEMP);
return;
}
LIST_INSERT_HEAD(&ks->ks_users, ku, ku_next);
sem_ref(ks);
mtx_unlock(&sem_lock);
}
#ifndef _SYS_SYSPROTO_H_
struct ksem_unlink_args {
char *name;
};
int ksem_unlink(struct thread *td, struct ksem_unlink_args *uap);
#endif
int
ksem_unlink(td, uap)
struct thread *td;
struct ksem_unlink_args *uap;
{
char name[SEM_MAX_NAMELEN + 1];
size_t done;
int error;
error = copyinstr(uap->name, name, SEM_MAX_NAMELEN + 1, &done);
return (error ? error :
kern_sem_unlink(td, name));
}
static int
kern_sem_unlink(td, name)
struct thread *td;
const char *name;
{
struct ksem *ks;
int error;
mtx_lock(&sem_lock);
ks = sem_lookup_byname(name);
if (ks != NULL) {
#ifdef MAC
error = mac_check_posix_sem_unlink(td->td_ucred, ks);
if (error) {
mtx_unlock(&sem_lock);
return (error);
}
#endif
error = sem_perm(td, ks);
} else
error = ENOENT;
DP(("sem_unlink: '%s' ks = %p, error = %d\n", name, ks, error));
if (error == 0) {
LIST_REMOVE(ks, ks_entry);
LIST_INSERT_HEAD(&ksem_deadhead, ks, ks_entry);
sem_rel(ks);
}
mtx_unlock(&sem_lock);
return (error);
}
#ifndef _SYS_SYSPROTO_H_
struct ksem_close_args {
semid_t id;
};
int ksem_close(struct thread *td, struct ksem_close_args *uap);
#endif
int
ksem_close(struct thread *td, struct ksem_close_args *uap)
{
return (kern_sem_close(td, uap->id));
}
static int
kern_sem_close(td, id)
struct thread *td;
semid_t id;
{
struct ksem *ks;
int error;
error = EINVAL;
mtx_lock(&sem_lock);
ks = ID_TO_SEM(id);
/* this is not a valid operation for unnamed sems */
if (ks != NULL && ks->ks_name != NULL)
error = sem_leave(td->td_proc, ks);
mtx_unlock(&sem_lock);
return (error);
}
#ifndef _SYS_SYSPROTO_H_
struct ksem_post_args {
semid_t id;
};
int ksem_post(struct thread *td, struct ksem_post_args *uap);
#endif
int
ksem_post(td, uap)
struct thread *td;
struct ksem_post_args *uap;
{
return (kern_sem_post(td, uap->id));
}
static int
kern_sem_post(td, id)
struct thread *td;
semid_t id;
{
struct ksem *ks;
int error;
mtx_lock(&sem_lock);
ks = ID_TO_SEM(id);
if (ks == NULL || !sem_hasopen(td, ks)) {
error = EINVAL;
goto err;
}
#ifdef MAC
error = mac_check_posix_sem_post(td->td_ucred, 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;
err:
mtx_unlock(&sem_lock);
return (error);
}
#ifndef _SYS_SYSPROTO_H_
struct ksem_wait_args {
semid_t id;
};
int ksem_wait(struct thread *td, struct ksem_wait_args *uap);
#endif
int
ksem_wait(td, uap)
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;
struct timespec *abstime;
};
int ksem_timedwait(struct thread *td, struct ksem_timedwait_args *uap);
#endif
int
ksem_timedwait(td, uap)
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;
};
int ksem_trywait(struct thread *td, struct ksem_trywait_args *uap);
#endif
int
ksem_trywait(td, uap)
struct thread *td;
struct ksem_trywait_args *uap;
{
return (kern_sem_wait(td, uap->id, 1, NULL));
}
static int
kern_sem_wait(td, id, tryflag, abstime)
struct thread *td;
semid_t id;
int tryflag;
struct timespec *abstime;
{
struct timespec ts1, ts2;
struct timeval tv;
struct ksem *ks;
int error;
DP((">>> kern_sem_wait entered!\n"));
mtx_lock(&sem_lock);
ks = ID_TO_SEM(id);
if (ks == NULL) {
DP(("kern_sem_wait ks == NULL\n"));
error = EINVAL;
goto err;
}
sem_ref(ks);
if (!sem_hasopen(td, ks)) {
DP(("kern_sem_wait hasopen failed\n"));
error = EINVAL;
goto err;
}
#ifdef MAC
error = mac_check_posix_sem_wait(td->td_ucred, 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));
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:
if (ks != NULL)
sem_rel(ks);
mtx_unlock(&sem_lock);
DP(("<<< kern_sem_wait leaving, error = %d\n", error));
return (error);
}
#ifndef _SYS_SYSPROTO_H_
struct ksem_getvalue_args {
semid_t id;
int *val;
};
int ksem_getvalue(struct thread *td, struct ksem_getvalue_args *uap);
#endif
int
ksem_getvalue(td, uap)
struct thread *td;
struct ksem_getvalue_args *uap;
{
struct ksem *ks;
int error, val;
mtx_lock(&sem_lock);
ks = ID_TO_SEM(uap->id);
if (ks == NULL || !sem_hasopen(td, ks)) {
mtx_unlock(&sem_lock);
return (EINVAL);
}
#ifdef MAC
error = mac_check_posix_sem_getvalue(td->td_ucred, ks);
if (error) {
mtx_unlock(&sem_lock);
return (error);
}
#endif
val = ks->ks_value;
mtx_unlock(&sem_lock);
error = copyout(&val, uap->val, sizeof(val));
return (error);
}
#ifndef _SYS_SYSPROTO_H_
struct ksem_destroy_args {
semid_t id;
};
int ksem_destroy(struct thread *td, struct ksem_destroy_args *uap);
#endif
int
ksem_destroy(td, uap)
struct thread *td;
struct ksem_destroy_args *uap;
{
struct ksem *ks;
int error;
mtx_lock(&sem_lock);
ks = ID_TO_SEM(uap->id);
if (ks == NULL || !sem_hasopen(td, ks) ||
ks->ks_name != NULL) {
error = EINVAL;
goto err;
}
#ifdef MAC
error = mac_check_posix_sem_destroy(td->td_ucred, ks);
if (error)
goto err;
#endif
if (ks->ks_waiters != 0) {
error = EBUSY;
goto err;
}
sem_rel(ks);
error = 0;
err:
mtx_unlock(&sem_lock);
return (error);
}
/*
* Count the number of kusers associated with a proc, so as to guess at how
* many to allocate when forking.
*/
static int
sem_count_proc(p)
struct proc *p;
{
struct ksem *ks;
struct kuser *ku;
int count;
mtx_assert(&sem_lock, MA_OWNED);
count = 0;
LIST_FOREACH(ks, &ksem_head, ks_entry) {
LIST_FOREACH(ku, &ks->ks_users, ku_next) {
if (ku->ku_pid == p->p_pid)
count++;
}
}
LIST_FOREACH(ks, &ksem_deadhead, ks_entry) {
LIST_FOREACH(ku, &ks->ks_users, ku_next) {
if (ku->ku_pid == p->p_pid)
count++;
}
}
return (count);
}
/*
* When a process forks, the child process must gain a reference to each open
* semaphore in the parent process, whether it is unlinked or not. This
* requires allocating a kuser structure for each semaphore reference in the
* new process. Because the set of semaphores in the parent can change while
* the fork is in progress, we have to handle races -- first we attempt to
* allocate enough storage to acquire references to each of the semaphores,
* then we enter the semaphores and release the temporary references.
*/
static void
sem_forkhook(arg, p1, p2, flags)
void *arg;
struct proc *p1;
struct proc *p2;
int flags;
{
struct ksem *ks, **sem_array;
int count, i, new_count;
struct kuser *ku;
mtx_lock(&sem_lock);
count = sem_count_proc(p1);
if (count == 0) {
mtx_unlock(&sem_lock);
return;
}
race_lost:
mtx_assert(&sem_lock, MA_OWNED);
mtx_unlock(&sem_lock);
sem_array = malloc(sizeof(struct ksem *) * count, M_TEMP, M_WAITOK);
mtx_lock(&sem_lock);
new_count = sem_count_proc(p1);
if (count < new_count) {
/* Lost race, repeat and allocate more storage. */
free(sem_array, M_TEMP);
count = new_count;
goto race_lost;
}
/*
* Given an array capable of storing an adequate number of semaphore
* references, now walk the list of semaphores and acquire a new
* reference for any semaphore opened by p1.
*/
count = new_count;
i = 0;
LIST_FOREACH(ks, &ksem_head, ks_entry) {
LIST_FOREACH(ku, &ks->ks_users, ku_next) {
if (ku->ku_pid == p1->p_pid) {
sem_ref(ks);
sem_array[i] = ks;
i++;
break;
}
}
}
LIST_FOREACH(ks, &ksem_deadhead, ks_entry) {
LIST_FOREACH(ku, &ks->ks_users, ku_next) {
if (ku->ku_pid == p1->p_pid) {
sem_ref(ks);
sem_array[i] = ks;
i++;
break;
}
}
}
mtx_unlock(&sem_lock);
KASSERT(i == count, ("sem_forkhook: i != count (%d, %d)", i, count));
/*
* Now cause p2 to enter each of the referenced semaphores, then
* release our temporary reference. This is pretty inefficient.
* Finally, free our temporary array.
*/
for (i = 0; i < count; i++) {
sem_enter(p2, sem_array[i]);
mtx_lock(&sem_lock);
sem_rel(sem_array[i]);
mtx_unlock(&sem_lock);
}
free(sem_array, M_TEMP);
}
static void
sem_exithook(arg, p)
void *arg;
struct proc *p;
{
struct ksem *ks, *ksnext;
mtx_lock(&sem_lock);
ks = LIST_FIRST(&ksem_head);
while (ks != NULL) {
ksnext = LIST_NEXT(ks, ks_entry);
sem_leave(p, ks);
ks = ksnext;
}
ks = LIST_FIRST(&ksem_deadhead);
while (ks != NULL) {
ksnext = LIST_NEXT(ks, ks_entry);
sem_leave(p, ks);
ks = ksnext;
}
mtx_unlock(&sem_lock);
}
static int
sem_modload(struct module *module, int cmd, void *arg)
{
int error = 0;
switch (cmd) {
case MOD_LOAD:
mtx_init(&sem_lock, "sem", "semaphore", MTX_DEF);
p31b_setcfg(CTL_P1003_1B_SEM_NSEMS_MAX, SEM_MAX);
p31b_setcfg(CTL_P1003_1B_SEM_VALUE_MAX, SEM_VALUE_MAX);
sem_exit_tag = EVENTHANDLER_REGISTER(process_exit, sem_exithook,
NULL, EVENTHANDLER_PRI_ANY);
sem_exec_tag = EVENTHANDLER_REGISTER(process_exec, sem_exithook,
NULL, EVENTHANDLER_PRI_ANY);
sem_fork_tag = EVENTHANDLER_REGISTER(process_fork, sem_forkhook, NULL, EVENTHANDLER_PRI_ANY);
break;
case MOD_UNLOAD:
if (nsems != 0) {
error = EOPNOTSUPP;
break;
}
EVENTHANDLER_DEREGISTER(process_exit, sem_exit_tag);
EVENTHANDLER_DEREGISTER(process_exec, sem_exec_tag);
EVENTHANDLER_DEREGISTER(process_fork, sem_fork_tag);
mtx_destroy(&sem_lock);
break;
case MOD_SHUTDOWN:
break;
default:
error = EINVAL;
break;
}
return (error);
}
static moduledata_t sem_mod = {
"sem",
&sem_modload,
NULL
};
SYSCALL_MODULE_HELPER(ksem_init);
SYSCALL_MODULE_HELPER(ksem_open);
SYSCALL_MODULE_HELPER(ksem_unlink);
SYSCALL_MODULE_HELPER(ksem_close);
SYSCALL_MODULE_HELPER(ksem_post);
SYSCALL_MODULE_HELPER(ksem_wait);
SYSCALL_MODULE_HELPER(ksem_timedwait);
SYSCALL_MODULE_HELPER(ksem_trywait);
SYSCALL_MODULE_HELPER(ksem_getvalue);
SYSCALL_MODULE_HELPER(ksem_destroy);
DECLARE_MODULE(sem, sem_mod, SI_SUB_SYSV_SEM, SI_ORDER_FIRST);
MODULE_VERSION(sem, 1);
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