xref: /src/sys/kern/sysv_sem.c

/*	$NetBSD: sysv_sem.c,v 1.97 2019/04/10 10:03:50 pgoyette Exp $	*/

/*-
 * Copyright (c) 1999, 2007 The NetBSD Foundation, Inc.
 * All rights reserved.
 *
 * This code is derived from software contributed to The NetBSD Foundation
 * by Jason R. Thorpe of the Numerical Aerospace Simulation Facility,
 * NASA Ames Research Center, and by Andrew Doran.
 *
 * 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 NETBSD FOUNDATION, INC. 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 FOUNDATION 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.
 */

/*
 * Implementation of SVID semaphores
 *
 * Author: Daniel Boulet
 *
 * This software is provided ``AS IS'' without any warranties of any kind.
 */

#include <sys/cdefs.h>
__KERNEL_RCSID(0, "$NetBSD: sysv_sem.c,v 1.97 2019/04/10 10:03:50 pgoyette Exp $");

#ifdef _KERNEL_OPT
#include "opt_sysv.h"
#endif

#include <sys/param.h>
#include <sys/kernel.h>
#include <sys/sem.h>
#include <sys/sysctl.h>
#include <sys/kmem.h>
#include <sys/mount.h>		/* XXX for <sys/syscallargs.h> */
#include <sys/syscallargs.h>
#include <sys/kauth.h>
#include <sys/once.h>

/*
 * Memory areas:
 *  1st: Pool of semaphore identifiers
 *  2nd: Semaphores
 *  3rd: Conditional variables
 *  4th: Undo structures
 */
struct semid_ds *	sema			__read_mostly;
static struct __sem *	sem			__read_mostly;
static kcondvar_t *	semcv			__read_mostly;
static int *		semu			__read_mostly;

static kmutex_t		semlock			__cacheline_aligned;
static bool		sem_realloc_state	__read_mostly;
static kcondvar_t	sem_realloc_cv;

/*
 * List of active undo structures, total number of semaphores,
 * and total number of semop waiters.
 */
static struct sem_undo *semu_list		__read_mostly;
static u_int		semtot			__cacheline_aligned;
static u_int		sem_waiters		__cacheline_aligned;

/* Macro to find a particular sem_undo vector */
#define SEMU(s, ix)	((struct sem_undo *)(((long)s) + ix * seminfo.semusz))

#ifdef SEM_DEBUG
#define SEM_PRINTF(a) printf a
#else
#define SEM_PRINTF(a)
#endif

void *hook;	/* cookie from exithook_establish() */

extern int kern_has_sysvsem;

SYSCTL_SETUP_PROTO(sysctl_ipc_sem_setup);

struct sem_undo *semu_alloc(struct proc *);
int semundo_adjust(struct proc *, struct sem_undo **, int, int, int);
void semundo_clear(int, int);

static ONCE_DECL(exithook_control);
static int seminit_exithook(void);

int
seminit(struct sysctllog **clog)
{
	int i, sz;
	vaddr_t v;

	mutex_init(&semlock, MUTEX_DEFAULT, IPL_NONE);
	cv_init(&sem_realloc_cv, "semrealc");
	sem_realloc_state = false;
	semtot = 0;
	sem_waiters = 0;

	/* Allocate the wired memory for our structures */
	sz = ALIGN(seminfo.semmni * sizeof(struct semid_ds)) +
	    ALIGN(seminfo.semmns * sizeof(struct __sem)) +
	    ALIGN(seminfo.semmni * sizeof(kcondvar_t)) +
	    ALIGN(seminfo.semmnu * seminfo.semusz);
	sz = round_page(sz);
	v = uvm_km_alloc(kernel_map, sz, 0, UVM_KMF_WIRED|UVM_KMF_ZERO);
	if (v == 0) {
		printf("sysv_sem: cannot allocate memory");
		return ENOMEM;
	}
	sema = (void *)v;
	sem = (void *)((uintptr_t)sema +
	    ALIGN(seminfo.semmni * sizeof(struct semid_ds)));
	semcv = (void *)((uintptr_t)sem +
	    ALIGN(seminfo.semmns * sizeof(struct __sem)));
	semu = (void *)((uintptr_t)semcv +
	    ALIGN(seminfo.semmni * sizeof(kcondvar_t)));

	for (i = 0; i < seminfo.semmni; i++) {
		sema[i]._sem_base = 0;
		sema[i].sem_perm.mode = 0;
		cv_init(&semcv[i], "semwait");
	}
	for (i = 0; i < seminfo.semmnu; i++) {
		struct sem_undo *suptr = SEMU(semu, i);
		suptr->un_proc = NULL;
	}
	semu_list = NULL;

	kern_has_sysvsem = 1;

#ifdef _MODULE
	if (clog)
		sysctl_ipc_sem_setup(clog);
#endif
	return 0;
}

static int
seminit_exithook(void)
{

	hook = exithook_establish(semexit, NULL);
	return 0;
}

int
semfini(void)
{
	int i, sz;
	vaddr_t v = (vaddr_t)sema;

	/* Don't allow module unload if we're busy */
	mutex_enter(&semlock);
	if (semtot) {
		mutex_exit(&semlock);
		return 1;
	}

	/* Remove the exit hook */
	if (hook)
		exithook_disestablish(hook);

	/* Destroy all our condvars */
	for (i = 0; i < seminfo.semmni; i++) {
		cv_destroy(&semcv[i]);
	}

	/* Free the wired memory that we allocated */
	sz = ALIGN(seminfo.semmni * sizeof(struct semid_ds)) +
	    ALIGN(seminfo.semmns * sizeof(struct __sem)) +
	    ALIGN(seminfo.semmni * sizeof(kcondvar_t)) +
	    ALIGN(seminfo.semmnu * seminfo.semusz);
	sz = round_page(sz);
	uvm_km_free(kernel_map, v, sz, UVM_KMF_WIRED);

	/* Destroy the last cv and mutex */
	cv_destroy(&sem_realloc_cv);
	mutex_exit(&semlock);
	mutex_destroy(&semlock);

	kern_has_sysvsem = 0;

	return 0;
}

static int
semrealloc(int newsemmni, int newsemmns, int newsemmnu)
{
	struct semid_ds *new_sema, *old_sema;
	struct __sem *new_sem;
	struct sem_undo *new_semu_list, *suptr, *nsuptr;
	int *new_semu;
	kcondvar_t *new_semcv;
	vaddr_t v;
	int i, j, lsemid, nmnus, sz;

	if (newsemmni < 1 || newsemmns < 1 || newsemmnu < 1)
		return EINVAL;

	/* Allocate the wired memory for our structures */
	sz = ALIGN(newsemmni * sizeof(struct semid_ds)) +
	    ALIGN(newsemmns * sizeof(struct __sem)) +
	    ALIGN(newsemmni * sizeof(kcondvar_t)) +
	    ALIGN(newsemmnu * seminfo.semusz);
	sz = round_page(sz);
	v = uvm_km_alloc(kernel_map, sz, 0, UVM_KMF_WIRED|UVM_KMF_ZERO);
	if (v == 0)
		return ENOMEM;

	mutex_enter(&semlock);
	if (sem_realloc_state) {
		mutex_exit(&semlock);
		uvm_km_free(kernel_map, v, sz, UVM_KMF_WIRED);
		return EBUSY;
	}
	sem_realloc_state = true;
	if (sem_waiters) {
		/*
		 * Mark reallocation state, wake-up all waiters,
		 * and wait while they will all exit.
		 */
		for (i = 0; i < seminfo.semmni; i++)
			cv_broadcast(&semcv[i]);
		while (sem_waiters)
			cv_wait(&sem_realloc_cv, &semlock);
	}
	old_sema = sema;

	/* Get the number of last slot */
	lsemid = 0;
	for (i = 0; i < seminfo.semmni; i++)
		if (sema[i].sem_perm.mode & SEM_ALLOC)
			lsemid = i;

	/* Get the number of currently used undo structures */
	nmnus = 0;
	for (i = 0; i < seminfo.semmnu; i++) {
		suptr = SEMU(semu, i);
		if (suptr->un_proc == NULL)
			continue;
		nmnus++;
	}

	/* We cannot reallocate less memory than we use */
	if (lsemid >= newsemmni || semtot > newsemmns || nmnus > newsemmnu) {
		mutex_exit(&semlock);
		uvm_km_free(kernel_map, v, sz, UVM_KMF_WIRED);
		return EBUSY;
	}

	new_sema = (void *)v;
	new_sem = (void *)((uintptr_t)new_sema +
	    ALIGN(newsemmni * sizeof(struct semid_ds)));
	new_semcv = (void *)((uintptr_t)new_sem +
	    ALIGN(newsemmns * sizeof(struct __sem)));
	new_semu = (void *)((uintptr_t)new_semcv +
	    ALIGN(newsemmni * sizeof(kcondvar_t)));

	/* Initialize all semaphore identifiers and condvars */
	for (i = 0; i < newsemmni; i++) {
		new_sema[i]._sem_base = 0;
		new_sema[i].sem_perm.mode = 0;
		cv_init(&new_semcv[i], "semwait");
	}
	for (i = 0; i < newsemmnu; i++) {
		nsuptr = SEMU(new_semu, i);
		nsuptr->un_proc = NULL;
	}

	/*
	 * Copy all identifiers, semaphores and list of the
	 * undo structures to the new memory allocation.
	 */
	j = 0;
	for (i = 0; i <= lsemid; i++) {
		if ((sema[i].sem_perm.mode & SEM_ALLOC) == 0)
			continue;
		memcpy(&new_sema[i], &sema[i], sizeof(struct semid_ds));
		new_sema[i]._sem_base = &new_sem[j];
		memcpy(new_sema[i]._sem_base, sema[i]._sem_base,
		    (sizeof(struct __sem) * sema[i].sem_nsems));
		j += sema[i].sem_nsems;
	}
	KASSERT(j == semtot);

	j = 0;
	new_semu_list = NULL;
	for (suptr = semu_list; suptr != NULL; suptr = suptr->un_next) {
		KASSERT(j < newsemmnu);
		nsuptr = SEMU(new_semu, j);
		memcpy(nsuptr, suptr, SEMUSZ);
		nsuptr->un_next = new_semu_list;
		new_semu_list = nsuptr;
		j++;
	}

	for (i = 0; i < seminfo.semmni; i++) {
		KASSERT(cv_has_waiters(&semcv[i]) == false);
		cv_destroy(&semcv[i]);
	}

	sz = ALIGN(seminfo.semmni * sizeof(struct semid_ds)) +
	    ALIGN(seminfo.semmns * sizeof(struct __sem)) +
	    ALIGN(seminfo.semmni * sizeof(kcondvar_t)) +
	    ALIGN(seminfo.semmnu * seminfo.semusz);
	sz = round_page(sz);

	/* Set the pointers and update the new values */
	sema = new_sema;
	sem = new_sem;
	semcv = new_semcv;
	semu = new_semu;
	semu_list = new_semu_list;

	seminfo.semmni = newsemmni;
	seminfo.semmns = newsemmns;
	seminfo.semmnu = newsemmnu;

	/* Reallocation completed - notify all waiters, if any */
	sem_realloc_state = false;
	cv_broadcast(&sem_realloc_cv);
	mutex_exit(&semlock);

	uvm_km_free(kernel_map, (vaddr_t)old_sema, sz, UVM_KMF_WIRED);
	return 0;
}

/*
 * Placebo.
 */

int
sys_semconfig(struct lwp *l, const struct sys_semconfig_args *uap, register_t *retval)
{

	RUN_ONCE(&exithook_control, seminit_exithook);

	*retval = 0;
	return 0;
}

/*
 * Allocate a new sem_undo structure for a process.
 * => Returns NULL on failure.
 */
struct sem_undo *
semu_alloc(struct proc *p)
{
	struct sem_undo *suptr, **supptr;
	bool attempted = false;
	int i;

	KASSERT(mutex_owned(&semlock));
again:
	/* Look for a free structure. */
	for (i = 0; i < seminfo.semmnu; i++) {
		suptr = SEMU(semu, i);
		if (suptr->un_proc == NULL) {
			/* Found.  Fill it in and return. */
			suptr->un_next = semu_list;
			semu_list = suptr;
			suptr->un_cnt = 0;
			suptr->un_proc = p;
			return suptr;
		}
	}

	/* Not found.  Attempt to free some structures. */
	if (!attempted) {
		bool freed = false;

		attempted = true;
		supptr = &semu_list;
		while ((suptr = *supptr) != NULL) {
			if (suptr->un_cnt == 0)  {
				suptr->un_proc = NULL;
				*supptr = suptr->un_next;
				freed = true;
			} else {
				supptr = &suptr->un_next;
			}
		}
		if (freed) {
			goto again;
		}
	}
	return NULL;
}

/*
 * Adjust a particular entry for a particular proc
 */

int
semundo_adjust(struct proc *p, struct sem_undo **supptr, int semid, int semnum,
    int adjval)
{
	struct sem_undo *suptr;
	struct sem_undo_entry *sunptr;
	int i;

	KASSERT(mutex_owned(&semlock));

	/*
	 * Look for and remember the sem_undo if the caller doesn't
	 * provide it
	 */

	suptr = *supptr;
	if (suptr == NULL) {
		for (suptr = semu_list; suptr != NULL; suptr = suptr->un_next)
			if (suptr->un_proc == p)
				break;

		if (suptr == NULL) {
			suptr = semu_alloc(p);
			if (suptr == NULL)
				return (ENOSPC);
		}
		*supptr = suptr;
	}

	/*
	 * Look for the requested entry and adjust it (delete if
	 * adjval becomes 0).
	 */
	sunptr = &suptr->un_ent[0];
	for (i = 0; i < suptr->un_cnt; i++, sunptr++) {
		if (sunptr->un_id != semid || sunptr->un_num != semnum)
			continue;
		sunptr->un_adjval += adjval;
		if (sunptr->un_adjval == 0) {
			suptr->un_cnt--;
			if (i < suptr->un_cnt)
				suptr->un_ent[i] =
				    suptr->un_ent[suptr->un_cnt];
		}
		return (0);
	}

	/* Didn't find the right entry - create it */
	if (suptr->un_cnt == SEMUME)
		return (EINVAL);

	sunptr = &suptr->un_ent[suptr->un_cnt];
	suptr->un_cnt++;
	sunptr->un_adjval = adjval;
	sunptr->un_id = semid;
	sunptr->un_num = semnum;
	return (0);
}

void
semundo_clear(int semid, int semnum)
{
	struct sem_undo *suptr;
	struct sem_undo_entry *sunptr, *sunend;

	KASSERT(mutex_owned(&semlock));

	for (suptr = semu_list; suptr != NULL; suptr = suptr->un_next)
		for (sunptr = &suptr->un_ent[0],
		    sunend = sunptr + suptr->un_cnt; sunptr < sunend;) {
			if (sunptr->un_id == semid) {
				if (semnum == -1 || sunptr->un_num == semnum) {
					suptr->un_cnt--;
					sunend--;
					if (sunptr != sunend)
						*sunptr = *sunend;
					if (semnum != -1)
						break;
					else
						continue;
				}
			}
			sunptr++;
		}
}

int
sys_____semctl50(struct lwp *l, const struct sys_____semctl50_args *uap,
    register_t *retval)
{
	/* {
		syscallarg(int) semid;
		syscallarg(int) semnum;
		syscallarg(int) cmd;
		syscallarg(union __semun *) arg;
	} */
	struct semid_ds sembuf;
	int cmd, error;
	void *pass_arg;
	union __semun karg;

	RUN_ONCE(&exithook_control, seminit_exithook);

	cmd = SCARG(uap, cmd);

	pass_arg = get_semctl_arg(cmd, &sembuf, &karg);

	if (pass_arg) {
		error = copyin(SCARG(uap, arg), &karg, sizeof(karg));
		if (error)
			return error;
		if (cmd == IPC_SET) {
			error = copyin(karg.buf, &sembuf, sizeof(sembuf));
			if (error)
				return (error);
		}
	}

	error = semctl1(l, SCARG(uap, semid), SCARG(uap, semnum), cmd,
	    pass_arg, retval);

	if (error == 0 && cmd == IPC_STAT)
		error = copyout(&sembuf, karg.buf, sizeof(sembuf));

	return (error);
}

int
semctl1(struct lwp *l, int semid, int semnum, int cmd, void *v,
    register_t *retval)
{
	kauth_cred_t cred = l->l_cred;
	union __semun *arg = v;
	struct semid_ds *sembuf = v, *semaptr;
	int i, error, ix;

	SEM_PRINTF(("call to semctl(%d, %d, %d, %p)\n",
	    semid, semnum, cmd, v));

	mutex_enter(&semlock);

	ix = IPCID_TO_IX(semid);
	if (ix < 0 || ix >= seminfo.semmni) {
		mutex_exit(&semlock);
		return (EINVAL);
	}

	semaptr = &sema[ix];
	if ((semaptr->sem_perm.mode & SEM_ALLOC) == 0 ||
	    semaptr->sem_perm._seq != IPCID_TO_SEQ(semid)) {
		mutex_exit(&semlock);
		return (EINVAL);
	}

	switch (cmd) {
	case IPC_RMID:
		if ((error = ipcperm(cred, &semaptr->sem_perm, IPC_M)) != 0)
			break;
		semaptr->sem_perm.cuid = kauth_cred_geteuid(cred);
		semaptr->sem_perm.uid = kauth_cred_geteuid(cred);
		semtot -= semaptr->sem_nsems;
		for (i = semaptr->_sem_base - sem; i < semtot; i++)
			sem[i] = sem[i + semaptr->sem_nsems];
		for (i = 0; i < seminfo.semmni; i++) {
			if ((sema[i].sem_perm.mode & SEM_ALLOC) &&
			    sema[i]._sem_base > semaptr->_sem_base)
				sema[i]._sem_base -= semaptr->sem_nsems;
		}
		semaptr->sem_perm.mode = 0;
		semundo_clear(ix, -1);
		cv_broadcast(&semcv[ix]);
		break;

	case IPC_SET:
		if ((error = ipcperm(cred, &semaptr->sem_perm, IPC_M)))
			break;
		KASSERT(sembuf != NULL);
		semaptr->sem_perm.uid = sembuf->sem_perm.uid;
		semaptr->sem_perm.gid = sembuf->sem_perm.gid;
		semaptr->sem_perm.mode = (semaptr->sem_perm.mode & ~0777) |
		    (sembuf->sem_perm.mode & 0777);
		semaptr->sem_ctime = time_second;
		break;

	case IPC_STAT:
		if ((error = ipcperm(cred, &semaptr->sem_perm, IPC_R)))
			break;
		KASSERT(sembuf != NULL);
		memset(sembuf, 0, sizeof *sembuf);
		sembuf->sem_perm = semaptr->sem_perm;
		sembuf->sem_perm.mode &= 0777;
		sembuf->sem_nsems = semaptr->sem_nsems;
		sembuf->sem_otime = semaptr->sem_otime;
		sembuf->sem_ctime = semaptr->sem_ctime;
		break;

	case GETNCNT:
		if ((error = ipcperm(cred, &semaptr->sem_perm, IPC_R)))
			break;
		if (semnum < 0 || semnum >= semaptr->sem_nsems) {
			error = EINVAL;
			break;
		}
		*retval = semaptr->_sem_base[semnum].semncnt;
		break;

	case GETPID:
		if ((error = ipcperm(cred, &semaptr->sem_perm, IPC_R)))
			break;
		if (semnum < 0 || semnum >= semaptr->sem_nsems) {
			error = EINVAL;
			break;
		}
		*retval = semaptr->_sem_base[semnum].sempid;
		break;

	case GETVAL:
		if ((error = ipcperm(cred, &semaptr->sem_perm, IPC_R)))
			break;
		if (semnum < 0 || semnum >= semaptr->sem_nsems) {
			error = EINVAL;
			break;
		}
		*retval = semaptr->_sem_base[semnum].semval;
		break;

	case GETALL:
		if ((error = ipcperm(cred, &semaptr->sem_perm, IPC_R)))
			break;
		KASSERT(arg != NULL);
		for (i = 0; i < semaptr->sem_nsems; i++) {
			error = copyout(&semaptr->_sem_base[i].semval,
			    &arg->array[i], sizeof(arg->array[i]));
			if (error != 0)
				break;
		}
		break;

	case GETZCNT:
		if ((error = ipcperm(cred, &semaptr->sem_perm, IPC_R)))
			break;
		if (semnum < 0 || semnum >= semaptr->sem_nsems) {
			error = EINVAL;
			break;
		}
		*retval = semaptr->_sem_base[semnum].semzcnt;
		break;

	case SETVAL:
		if ((error = ipcperm(cred, &semaptr->sem_perm, IPC_W)))
			break;
		if (semnum < 0 || semnum >= semaptr->sem_nsems) {
			error = EINVAL;
			break;
		}
		KASSERT(arg != NULL);
		if ((unsigned int)arg->val > seminfo.semvmx) {
			error = ERANGE;
			break;
		}
		semaptr->_sem_base[semnum].semval = arg->val;
		semundo_clear(ix, semnum);
		cv_broadcast(&semcv[ix]);
		break;

	case SETALL:
		if ((error = ipcperm(cred, &semaptr->sem_perm, IPC_W)))
			break;
		KASSERT(arg != NULL);
		for (i = 0; i < semaptr->sem_nsems; i++) {
			unsigned short semval;
			error = copyin(&arg->array[i], &semval,
			    sizeof(arg->array[i]));
			if (error != 0)
				break;
			if ((unsigned int)semval > seminfo.semvmx) {
				error = ERANGE;
				break;
			}
			semaptr->_sem_base[i].semval = semval;
		}
		semundo_clear(ix, -1);
		cv_broadcast(&semcv[ix]);
		break;

	default:
		error = EINVAL;
		break;
	}

	mutex_exit(&semlock);
	return (error);
}

int
sys_semget(struct lwp *l, const struct sys_semget_args *uap, register_t *retval)
{
	/* {
		syscallarg(key_t) key;
		syscallarg(int) nsems;
		syscallarg(int) semflg;
	} */
	int semid, error = 0;
	int key = SCARG(uap, key);
	int nsems = SCARG(uap, nsems);
	int semflg = SCARG(uap, semflg);
	kauth_cred_t cred = l->l_cred;

	RUN_ONCE(&exithook_control, seminit_exithook);

	SEM_PRINTF(("semget(0x%x, %d, 0%o)\n", key, nsems, semflg));

	mutex_enter(&semlock);

	if (key != IPC_PRIVATE) {
		for (semid = 0; semid < seminfo.semmni; semid++) {
			if ((sema[semid].sem_perm.mode & SEM_ALLOC) &&
			    sema[semid].sem_perm._key == key)
				break;
		}
		if (semid < seminfo.semmni) {
			SEM_PRINTF(("found public key\n"));
			if ((error = ipcperm(cred, &sema[semid].sem_perm,
			    semflg & 0700)))
			    	goto out;
			if (nsems > 0 && sema[semid].sem_nsems < nsems) {
				SEM_PRINTF(("too small\n"));
				error = EINVAL;
				goto out;
			}
			if ((semflg & IPC_CREAT) && (semflg & IPC_EXCL)) {
				SEM_PRINTF(("not exclusive\n"));
				error = EEXIST;
				goto out;
			}
			goto found;
		}
	}

	SEM_PRINTF(("need to allocate the semid_ds\n"));
	if (key == IPC_PRIVATE || (semflg & IPC_CREAT)) {
		if (nsems <= 0 || nsems > seminfo.semmsl) {
			SEM_PRINTF(("nsems out of range (0<%d<=%d)\n", nsems,
			    seminfo.semmsl));
			error = EINVAL;
			goto out;
		}
		if (nsems > seminfo.semmns - semtot) {
			SEM_PRINTF(("not enough semaphores left "
			    "(need %d, got %d)\n",
			    nsems, seminfo.semmns - semtot));
			error = ENOSPC;
			goto out;
		}
		for (semid = 0; semid < seminfo.semmni; semid++) {
			if ((sema[semid].sem_perm.mode & SEM_ALLOC) == 0)
				break;
		}
		if (semid == seminfo.semmni) {
			SEM_PRINTF(("no more semid_ds's available\n"));
			error = ENOSPC;
			goto out;
		}
		SEM_PRINTF(("semid %d is available\n", semid));
		sema[semid].sem_perm._key = key;
		sema[semid].sem_perm.cuid = kauth_cred_geteuid(cred);
		sema[semid].sem_perm.uid = kauth_cred_geteuid(cred);
		sema[semid].sem_perm.cgid = kauth_cred_getegid(cred);
		sema[semid].sem_perm.gid = kauth_cred_getegid(cred);
		sema[semid].sem_perm.mode = (semflg & 0777) | SEM_ALLOC;
		sema[semid].sem_perm._seq =
		    (sema[semid].sem_perm._seq + 1) & 0x7fff;
		sema[semid].sem_nsems = nsems;
		sema[semid].sem_otime = 0;
		sema[semid].sem_ctime = time_second;
		sema[semid]._sem_base = &sem[semtot];
		semtot += nsems;
		memset(sema[semid]._sem_base, 0,
		    sizeof(sema[semid]._sem_base[0]) * nsems);
		SEM_PRINTF(("sembase = %p, next = %p\n", sema[semid]._sem_base,
		    &sem[semtot]));
	} else {
		SEM_PRINTF(("didn't find it and wasn't asked to create it\n"));
		error = ENOENT;
		goto out;
	}

 found:
	*retval = IXSEQ_TO_IPCID(semid, sema[semid].sem_perm);
 out:
	mutex_exit(&semlock);
	return (error);
}

#define SMALL_SOPS 8

int
sys_semop(struct lwp *l, const struct sys_semop_args *uap, register_t *retval)
{
	/* {
		syscallarg(int) semid;
		syscallarg(struct sembuf *) sops;
		syscallarg(size_t) nsops;
	} */
	struct proc *p = l->l_proc;
	int semid = SCARG(uap, semid), seq;
	size_t nsops = SCARG(uap, nsops);
	struct sembuf small_sops[SMALL_SOPS];
	struct sembuf *sops;
	struct semid_ds *semaptr;
	struct sembuf *sopptr = NULL;
	struct __sem *semptr = NULL;
	struct sem_undo *suptr = NULL;
	kauth_cred_t cred = l->l_cred;
	int i, error;
	int do_wakeup, do_undos;

	RUN_ONCE(&exithook_control, seminit_exithook);

	SEM_PRINTF(("call to semop(%d, %p, %zd)\n", semid, SCARG(uap,sops), nsops));

	if (__predict_false((p->p_flag & PK_SYSVSEM) == 0)) {
		mutex_enter(p->p_lock);
		p->p_flag |= PK_SYSVSEM;
		mutex_exit(p->p_lock);
	}

restart:
	if (nsops <= SMALL_SOPS) {
		sops = small_sops;
	} else if (nsops <= seminfo.semopm) {
		sops = kmem_alloc(nsops * sizeof(*sops), KM_SLEEP);
	} else {
		SEM_PRINTF(("too many sops (max=%d, nsops=%zd)\n",
		    seminfo.semopm, nsops));
		return (E2BIG);
	}

	error = copyin(SCARG(uap, sops), sops, nsops * sizeof(sops[0]));
	if (error) {
		SEM_PRINTF(("error = %d from copyin(%p, %p, %zd)\n", error,
		    SCARG(uap, sops), &sops, nsops * sizeof(sops[0])));
		if (sops != small_sops)
			kmem_free(sops, nsops * sizeof(*sops));
		return error;
	}

	mutex_enter(&semlock);
	/* In case of reallocation, we will wait for completion */
	while (__predict_false(sem_realloc_state))
		cv_wait(&sem_realloc_cv, &semlock);

	semid = IPCID_TO_IX(semid);	/* Convert back to zero origin */
	if (semid < 0 || semid >= seminfo.semmni) {
		error = EINVAL;
		goto out;
	}

	semaptr = &sema[semid];
	seq = IPCID_TO_SEQ(SCARG(uap, semid));
	if ((semaptr->sem_perm.mode & SEM_ALLOC) == 0 ||
	    semaptr->sem_perm._seq != seq) {
		error = EINVAL;
		goto out;
	}

	if ((error = ipcperm(cred, &semaptr->sem_perm, IPC_W))) {
		SEM_PRINTF(("error = %d from ipaccess\n", error));
		goto out;
	}

	for (i = 0; i < nsops; i++)
		if (sops[i].sem_num >= semaptr->sem_nsems) {
			error = EFBIG;
			goto out;
		}

	/*
	 * Loop trying to satisfy the vector of requests.
	 * If we reach a point where we must wait, any requests already
	 * performed are rolled back and we go to sleep until some other
	 * process wakes us up.  At this point, we start all over again.
	 *
	 * This ensures that from the perspective of other tasks, a set
	 * of requests is atomic (never partially satisfied).
	 */
	do_undos = 0;

	for (;;) {
		do_wakeup = 0;

		for (i = 0; i < nsops; i++) {
			sopptr = &sops[i];
			semptr = &semaptr->_sem_base[sopptr->sem_num];

			SEM_PRINTF(("semop:  semaptr=%p, sem_base=%p, "
			    "semptr=%p, sem[%d]=%d : op=%d, flag=%s\n",
			    semaptr, semaptr->_sem_base, semptr,
			    sopptr->sem_num, semptr->semval, sopptr->sem_op,
			    (sopptr->sem_flg & IPC_NOWAIT) ?
			    "nowait" : "wait"));

			if (sopptr->sem_op < 0) {
				if ((int)(semptr->semval +
				    sopptr->sem_op) < 0) {
					SEM_PRINTF(("semop:  "
					    "can't do it now\n"));
					break;
				} else {
					semptr->semval += sopptr->sem_op;
					if (semptr->semval == 0 &&
					    semptr->semzcnt > 0)
						do_wakeup = 1;
				}
				if (sopptr->sem_flg & SEM_UNDO)
					do_undos = 1;
			} else if (sopptr->sem_op == 0) {
				if (semptr->semval > 0) {
					SEM_PRINTF(("semop:  not zero now\n"));
					break;
				}
			} else {
				if (semptr->semncnt > 0)
					do_wakeup = 1;
				semptr->semval += sopptr->sem_op;
				if (sopptr->sem_flg & SEM_UNDO)
					do_undos = 1;
			}
		}

		/*
		 * Did we get through the entire vector?
		 */
		if (i >= nsops)
			goto done;

		/*
		 * No ... rollback anything that we've already done
		 */
		SEM_PRINTF(("semop:  rollback 0 through %d\n", i - 1));
		while (i-- > 0)
			semaptr->_sem_base[sops[i].sem_num].semval -=
			    sops[i].sem_op;

		/*
		 * If the request that we couldn't satisfy has the
		 * NOWAIT flag set then return with EAGAIN.
		 */
		if (sopptr->sem_flg & IPC_NOWAIT) {
			error = EAGAIN;
			goto out;
		}

		if (sopptr->sem_op == 0)
			semptr->semzcnt++;
		else
			semptr->semncnt++;

		sem_waiters++;
		SEM_PRINTF(("semop:  good night!\n"));
		error = cv_wait_sig(&semcv[semid], &semlock);
		SEM_PRINTF(("semop:  good morning (error=%d)!\n", error));
		sem_waiters--;

		/* Notify reallocator, if it is waiting */
		cv_broadcast(&sem_realloc_cv);

		/*
		 * Make sure that the semaphore still exists
		 */
		if ((semaptr->sem_perm.mode & SEM_ALLOC) == 0 ||
		    semaptr->sem_perm._seq != seq) {
			error = EIDRM;
			goto out;
		}

		/*
		 * The semaphore is still alive.  Readjust the count of
		 * waiting processes.
		 */
		semptr = &semaptr->_sem_base[sopptr->sem_num];
		if (sopptr->sem_op == 0)
			semptr->semzcnt--;
		else
			semptr->semncnt--;

		/* In case of such state, restart the call */
		if (sem_realloc_state) {
			mutex_exit(&semlock);
			goto restart;
		}

		/* Is it really morning, or was our sleep interrupted? */
		if (error != 0) {
			error = EINTR;
			goto out;
		}
		SEM_PRINTF(("semop:  good morning!\n"));
	}

done:
	/*
	 * Process any SEM_UNDO requests.
	 */
	if (do_undos) {
		for (i = 0; i < nsops; i++) {
			/*
			 * We only need to deal with SEM_UNDO's for non-zero
			 * op's.
			 */
			int adjval;

			if ((sops[i].sem_flg & SEM_UNDO) == 0)
				continue;
			adjval = sops[i].sem_op;
			if (adjval == 0)
				continue;
			error = semundo_adjust(p, &suptr, semid,
			    sops[i].sem_num, -adjval);
			if (error == 0)
				continue;

			/*
			 * Oh-Oh!  We ran out of either sem_undo's or undo's.
			 * Rollback the adjustments to this point and then
			 * rollback the semaphore ups and down so we can return
			 * with an error with all structures restored.  We
			 * rollback the undo's in the exact reverse order that
			 * we applied them.  This guarantees that we won't run
			 * out of space as we roll things back out.
			 */
			while (i-- > 0) {
				if ((sops[i].sem_flg & SEM_UNDO) == 0)
					continue;
				adjval = sops[i].sem_op;
				if (adjval == 0)
					continue;
				if (semundo_adjust(p, &suptr, semid,
				    sops[i].sem_num, adjval) != 0)
					panic("semop - can't undo undos");
			}

			for (i = 0; i < nsops; i++)
				semaptr->_sem_base[sops[i].sem_num].semval -=
				    sops[i].sem_op;

			SEM_PRINTF(("error = %d from semundo_adjust\n", error));
			goto out;
		} /* loop through the sops */
	} /* if (do_undos) */

	/* We're definitely done - set the sempid's */
	for (i = 0; i < nsops; i++) {
		sopptr = &sops[i];
		semptr = &semaptr->_sem_base[sopptr->sem_num];
		semptr->sempid = p->p_pid;
	}

	/* Update sem_otime */
	semaptr->sem_otime = time_second;

	/* Do a wakeup if any semaphore was up'd. */
	if (do_wakeup) {
		SEM_PRINTF(("semop:  doing wakeup\n"));
		cv_broadcast(&semcv[semid]);
		SEM_PRINTF(("semop:  back from wakeup\n"));
	}
	SEM_PRINTF(("semop:  done\n"));
	*retval = 0;

 out:
	mutex_exit(&semlock);
	if (sops != small_sops)
		kmem_free(sops, nsops * sizeof(*sops));
	return error;
}

/*
 * Go through the undo structures for this process and apply the
 * adjustments to semaphores.
 */
/*ARGSUSED*/
void
semexit(struct proc *p, void *v)
{
	struct sem_undo *suptr;
	struct sem_undo **supptr;

	if ((p->p_flag & PK_SYSVSEM) == 0)
		return;

	mutex_enter(&semlock);

	/*
	 * Go through the chain of undo vectors looking for one
	 * associated with this process.
	 */

	for (supptr = &semu_list; (suptr = *supptr) != NULL;
	    supptr = &suptr->un_next) {
		if (suptr->un_proc == p)
			break;
	}

	/*
	 * If there is no undo vector, skip to the end.
	 */

	if (suptr == NULL) {
		mutex_exit(&semlock);
		return;
	}

	/*
	 * We now have an undo vector for this process.
	 */

	SEM_PRINTF(("proc @%p has undo structure with %d entries\n", p,
	    suptr->un_cnt));

	/*
	 * If there are any active undo elements then process them.
	 */
	if (suptr->un_cnt > 0) {
		int ix;

		for (ix = 0; ix < suptr->un_cnt; ix++) {
			int semid = suptr->un_ent[ix].un_id;
			int semnum = suptr->un_ent[ix].un_num;
			int adjval = suptr->un_ent[ix].un_adjval;
			struct semid_ds *semaptr;

			semaptr = &sema[semid];
			if ((semaptr->sem_perm.mode & SEM_ALLOC) == 0)
			if (semnum >= semaptr->sem_nsems)
				panic("semexit - semnum out of range");

			SEM_PRINTF(("semexit:  %p id=%d num=%d(adj=%d) ; "
			    "sem=%d\n",
			    suptr->un_proc, suptr->un_ent[ix].un_id,
			    suptr->un_ent[ix].un_num,
			    suptr->un_ent[ix].un_adjval,
			    semaptr->_sem_base[semnum].semval));

			if (adjval < 0 &&
			    semaptr->_sem_base[semnum].semval < -adjval)
				semaptr->_sem_base[semnum].semval = 0;
			else
				semaptr->_sem_base[semnum].semval += adjval;

			cv_broadcast(&semcv[semid]);
			SEM_PRINTF(("semexit:  back from wakeup\n"));
		}
	}

	/*
	 * Deallocate the undo vector.
	 */
	SEM_PRINTF(("removing vector\n"));
	suptr->un_proc = NULL;
	*supptr = suptr->un_next;
	mutex_exit(&semlock);
}

/*
 * Sysctl initialization and nodes.
 */

static int
sysctl_ipc_semmni(SYSCTLFN_ARGS)
{
	int newsize, error;
	struct sysctlnode node;
	node = *rnode;
	node.sysctl_data = &newsize;

	newsize = seminfo.semmni;
	error = sysctl_lookup(SYSCTLFN_CALL(&node));
	if (error || newp == NULL)
		return error;

	return semrealloc(newsize, seminfo.semmns, seminfo.semmnu);
}

static int
sysctl_ipc_semmns(SYSCTLFN_ARGS)
{
	int newsize, error;
	struct sysctlnode node;
	node = *rnode;
	node.sysctl_data = &newsize;

	newsize = seminfo.semmns;
	error = sysctl_lookup(SYSCTLFN_CALL(&node));
	if (error || newp == NULL)
		return error;

	return semrealloc(seminfo.semmni, newsize, seminfo.semmnu);
}

static int
sysctl_ipc_semmnu(SYSCTLFN_ARGS)
{
	int newsize, error;
	struct sysctlnode node;
	node = *rnode;
	node.sysctl_data = &newsize;

	newsize = seminfo.semmnu;
	error = sysctl_lookup(SYSCTLFN_CALL(&node));
	if (error || newp == NULL)
		return error;

	return semrealloc(seminfo.semmni, seminfo.semmns, newsize);
}

SYSCTL_SETUP(sysctl_ipc_sem_setup, "sysctl kern.ipc subtree setup")
{
	const struct sysctlnode *node = NULL;

	sysctl_createv(clog, 0, NULL, &node,
		CTLFLAG_PERMANENT,
		CTLTYPE_NODE, "ipc",
		SYSCTL_DESCR("SysV IPC options"),
		NULL, 0, NULL, 0,
		CTL_KERN, KERN_SYSVIPC, CTL_EOL);

	if (node == NULL)
		return;

	sysctl_createv(clog, 0, &node, NULL,
		CTLFLAG_PERMANENT | CTLFLAG_READWRITE,
		CTLTYPE_INT, "semmni",
		SYSCTL_DESCR("Max number of number of semaphore identifiers"),
		sysctl_ipc_semmni, 0, &seminfo.semmni, 0,
		CTL_CREATE, CTL_EOL);
	sysctl_createv(clog, 0, &node, NULL,
		CTLFLAG_PERMANENT | CTLFLAG_READWRITE,
		CTLTYPE_INT, "semmns",
		SYSCTL_DESCR("Max number of number of semaphores in system"),
		sysctl_ipc_semmns, 0, &seminfo.semmns, 0,
		CTL_CREATE, CTL_EOL);
	sysctl_createv(clog, 0, &node, NULL,
		CTLFLAG_PERMANENT | CTLFLAG_READWRITE,
		CTLTYPE_INT, "semmnu",
		SYSCTL_DESCR("Max number of undo structures in system"),
		sysctl_ipc_semmnu, 0, &seminfo.semmnu, 0,
		CTL_CREATE, CTL_EOL);
}