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freebsd-skq/sys/kern/uipc_sem.c
Robert Watson 873fbcd776 Further system call comment cleanup: 
- Remove also "MP SAFE" after prior "MPSAFE" pass. (suggested by bde)
- Remove extra blank lines in some cases.
- Add extra blank lines in some cases.
- Remove no-op comments consisting solely of the function name, the word
  "syscall", or the system call name.
- Add punctuation.
- Re-wrap some comments.
2007-03-05 13:10:58 +00:00

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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/ksem.h>
#include <sys/priv.h>
#include <sys/proc.h>
#include <sys/posix4.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/semaphore.h>
#include <sys/syscall.h>
#include <sys/stat.h>
#include <sys/sysent.h>
#include <sys/sysctl.h>
#include <sys/time.h>
#include <sys/malloc.h>
#include <sys/fcntl.h>
#include <sys/_semaphore.h>
#include <security/mac/mac_framework.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_exechook(void *arg, struct proc *p, struct image_params *imgp);
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(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(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(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(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(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(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(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(struct thread *td, struct ksem *ks)
{
struct ucred *uc;
/*
* XXXRW: This permission routine appears to be incorrect. If the
* user matches, we shouldn't go on to the group if the user
* permissions don't allow the action? Not changed for now. To fix,
* change from a series of if (); if (); to if () else if () else...
*/
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)
return (0);
if ((uc->cr_gid == ks->ks_gid) && (ks->ks_mode & S_IWGRP) != 0)
return (0);
if ((ks->ks_mode & S_IWOTH) != 0)
return (0);
return (priv_check(td, PRIV_SEM_WRITE));
}
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(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(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(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(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(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(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(struct thread *td, struct ksem_post_args *uap)
{
return (kern_sem_post(td, uap->id));
}
static int
kern_sem_post(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(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;
};
int ksem_timedwait(struct thread *td, struct ksem_timedwait_args *uap);
#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;
};
int ksem_trywait(struct thread *td, struct ksem_trywait_args *uap);
#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 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(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(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(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(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_exechook(void *arg, struct proc *p, struct image_params *imgp __unused)
{
sem_exithook(arg, p);
}
static void
sem_exithook(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_exechook,
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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