/*
 * CDDL HEADER START
 *
 * The contents of this file are subject to the terms of the
 * Common Development and Distribution License (the "License").
 * You may not use this file except in compliance with the License.
 *
 * You can obtain a copy of the license at usr/src/OPENSOLARIS.LICENSE
 * or http://www.opensolaris.org/os/licensing.
 * See the License for the specific language governing permissions
 * and limitations under the License.
 *
 * When distributing Covered Code, include this CDDL HEADER in each
 * file and include the License file at usr/src/OPENSOLARIS.LICENSE.
 * If applicable, add the following below this CDDL HEADER, with the
 * fields enclosed by brackets "[]" replaced with your own identifying
 * information: Portions Copyright [yyyy] [name of copyright owner]
 *
 * CDDL HEADER END
 */

/*
 * Copyright 2008 Sun Microsystems, Inc.  All rights reserved.
 * Use is subject to license terms.
 */

/*
 * plock - lock "segments" in physical memory.
 *
 * Supports SVID-compatible plock, taking into account dynamically linked
 * objects (such as shared libraries).
 */

#include "lint.h"
#include <mtlib.h>
#include <sys/types.h>
#include <sys/mman.h>
#include <sys/lock.h>
#include <errno.h>
#include <stddef.h>
#include <unistd.h>
#include <thread.h>
#include <synch.h>

/*
 * Module-scope variables.
 */
static  int lock_state = 0;             /* lock state */
static  pid_t state_pid = -1;           /* pid to which state belongs */
static mutex_t plock_lock = DEFAULTMUTEX;

/*
 * plock
 */
int
plock(int op)                           /* desired operation */
{
        int     e;                      /* return value */
        pid_t   pid;                    /* current pid */

        lmutex_lock(&plock_lock);

        /*
         * Validate state of lock's.  If parent has forked, then
         * the lock state needs to be reset (children do not inherit
         * memory locks, and thus do not inherit their state).
         */
        if ((pid = getpid()) != state_pid) {
                lock_state = 0;
                state_pid = pid;
        }

        /*
         * Dispatch on operation.  Note: plock and its relatives depend
         * upon "op" being bit encoded.
         */
        switch (op) {

        /*
         * UNLOCK: remove all memory locks.  Requires that some be set!
         */
        case UNLOCK:
                if (lock_state == 0) {
                        errno = EINVAL;
                        lmutex_unlock(&plock_lock);
                        return (-1);
                }
                e = munlockall();
                if (e) {
                        lmutex_unlock(&plock_lock);
                        return (-1);
                } else {
                        lock_state = 0;
                        lmutex_unlock(&plock_lock);
                        return (0);
                }
                /*NOTREACHED*/

        /*
         * TXTLOCK: locks text segments.
         */
        case TXTLOCK:

                /*
                 * If a text or process lock is already set, then fail.
                 */
                if ((lock_state & TXTLOCK) || (lock_state & PROCLOCK)) {
                        errno = EINVAL;
                        lmutex_unlock(&plock_lock);
                        return (-1);
                }

                /*
                 * Try to apply the lock(s).  If a failure occurs,
                 * memcntl backs them out automatically.
                 */
                e = memcntl(NULL, 0, MC_LOCKAS, (caddr_t)MCL_CURRENT,
                    PROC_TEXT|PRIVATE, 0);
                if (!e)
                        lock_state |= TXTLOCK;
                lmutex_unlock(&plock_lock);
                return (e);
                /*NOTREACHED*/

        /*
         * DATLOCK: locks data segment(s), including the stack and all
         * future growth in the address space.
         */
        case DATLOCK:

                /*
                 * If a data or process lock is already set, then fail.
                 */
                if ((lock_state & DATLOCK) || (lock_state & PROCLOCK)) {
                        errno = EINVAL;
                        lmutex_unlock(&plock_lock);
                        return (-1);
                }

                /*
                 * Try to lock the data and stack segments.  On failure
                 * memcntl undoes the locks internally.
                 */
                e = memcntl(NULL, 0, MC_LOCKAS, (caddr_t)MCL_CURRENT,
                    PROC_DATA|PRIVATE, 0);
                if (e) {
                        lmutex_unlock(&plock_lock);
                        return (-1);
                }

                /* try to set a lock for all future mappings. */
                e = mlockall(MCL_FUTURE);

                /*
                 * If failures have occurred, back out the locks
                 * and return failure.
                 */
                if (e) {
                        e = errno;
                        (void) memcntl(NULL, 0, MC_UNLOCKAS,
                            (caddr_t)MCL_CURRENT, PROC_DATA|PRIVATE, 0);
                        errno = e;
                        lmutex_unlock(&plock_lock);
                        return (-1);
                }

                /*
                 * Data, stack, and growth have been locked.  Set state
                 * and return success.
                 */
                lock_state |= DATLOCK;
                lmutex_unlock(&plock_lock);
                return (0);
                /*NOTREACHED*/

        /*
         * PROCLOCK: lock everything, and all future things as well.
         * There should be nothing locked when this is called.
         */
        case PROCLOCK:
                if (lock_state) {
                        errno = EINVAL;
                        lmutex_unlock(&plock_lock);
                        return (-1);
                }
                if (mlockall(MCL_CURRENT | MCL_FUTURE) == 0) {
                        lock_state |= PROCLOCK;
                        lmutex_unlock(&plock_lock);
                        return (0);
                } else {
                        lmutex_unlock(&plock_lock);
                        return (-1);
                }
                /*NOTREACHED*/

        /*
         * Invalid operation.
         */
        default:
                errno = EINVAL;
                lmutex_unlock(&plock_lock);
                return (-1);
                /*NOTREACHED*/
        }
}