9348 mii: duplicate 'const' declaration specifier

[unleashed.git] / usr / src / uts / common / io / iwscons.c

/*
 * 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.
 */


/*
 * workstation console redirecting driver
 *
 * Redirects all I/O through a given device instance to the device designated
 * as the current target, as given by the vnode associated with the first
 * entry in the list of redirections for the given device instance.  The
 * implementation assumes that this vnode denotes a STREAMS device; this is
 * perhaps a bug.
 *
 * Supports the SRIOCSREDIR ioctl for designating a new redirection target.
 * The new target is added to the front of a list of potentially active
 * designees.  Should the device at the front of this list be closed, the new
 * front entry assumes active duty.  (Stated differently, redirection targets
 * stack, except that it's possible for entries in the interior of the stack
 * to go away.)
 *
 * Supports the SRIOCISREDIR ioctl for inquiring whether the descriptor given
 * as argument is the current front of the redirection list associated with
 * the descriptor on which the ioctl was issued.
 */

#include <sys/types.h>
#include <sys/sysmacros.h>
#include <sys/open.h>
#include <sys/param.h>
#include <sys/systm.h>
#include <sys/signal.h>
#include <sys/cred.h>
#include <sys/user.h>
#include <sys/proc.h>
#include <sys/vnode.h>
#include <sys/uio.h>
#include <sys/file.h>
#include <sys/kmem.h>
#include <sys/stat.h>
#include <sys/stream.h>
#include <sys/stropts.h>
#include <sys/strsubr.h>
#include <sys/poll.h>
#include <sys/debug.h>
#include <sys/strredir.h>
#include <sys/conf.h>
#include <sys/ddi.h>
#include <sys/sunddi.h>
#include <sys/errno.h>
#include <sys/modctl.h>
#include <sys/sunldi.h>
#include <sys/consdev.h>
#include <sys/fs/snode.h>

/*
 * Global data
 */
static dev_info_t       *iwscn_dip;

/*
 * We record the list of redirections as a linked list of iwscn_list_t
 * structures.  We need to keep track of the target's vp, so that
 * we can vector reads, writes, etc. off to the current designee.
 */
typedef struct _iwscn_list {
        struct _iwscn_list      *wl_next;       /* next entry */
        vnode_t                 *wl_vp;         /* target's vnode */
        int                     wl_ref_cnt;     /* operation in progress */
        boolean_t               wl_is_console;  /* is the real console */
} iwscn_list_t;
static iwscn_list_t     *iwscn_list;

/*
 * iwscn_list_lock serializes modifications to the global iwscn_list list.
 *
 * iwscn_list_cv is used when freeing an entry from iwscn_list to allow
 * the caller to wait till the wl_ref_cnt field is zero.
 *
 * iwscn_redirect_lock is used to serialize redirection requests.  This
 * is required to ensure that all active redirection streams have
 * the redirection streams module (redirmod) pushed on them.
 *
 * If both iwscn_redirect_lock and iwscn_list_lock must be held then
 * iwscn_redirect_lock must be acquired first.
 */
static kcondvar_t       iwscn_list_cv;
static kmutex_t         iwscn_list_lock;
static kmutex_t         iwscn_redirect_lock;

/*
 * Routines for managing iwscn_list
 */
static vnode_t *
str_vp(vnode_t *vp)
{
        /*
         * Here we switch to using the vnode that is linked
         * to from the stream queue.  (In the case of device
         * streams this will correspond to the common vnode
         * for the device.)  The reason we use this vnode
         * is that when wcmclose() calls srpop(), this is the
         * only vnode that it has access to.
         */
        ASSERT(vp->v_stream != NULL);
        return (vp->v_stream->sd_vnode);
}

/*
 * Interrupt any operations that may be outstanding against this vnode.
 * optionally, wait for them to complete.
 */
static void
srinterrupt(iwscn_list_t *lp, boolean_t wait)
{
        ASSERT(MUTEX_HELD(&iwscn_list_lock));

        while (lp->wl_ref_cnt != 0) {
                strsetrerror(lp->wl_vp, EINTR, 0, NULL);
                strsetwerror(lp->wl_vp, EINTR, 0, NULL);
                if (!wait)
                        break;
                cv_wait(&iwscn_list_cv, &iwscn_list_lock);
        }
}

/*
 * Remove vp from the redirection list rooted at iwscn_list, should it
 * be there. Return a pointer to the removed entry.
 */
static iwscn_list_t *
srrm(vnode_t *vp)
{
        iwscn_list_t    *lp, **lpp;

        ASSERT(MUTEX_HELD(&iwscn_list_lock));

        /* Get the stream vnode */
        vp = str_vp(vp);
        ASSERT(vp);

        /* Look for this vnode on the redirection list */
        for (lpp = &iwscn_list; (lp = *lpp) != NULL; lpp = &lp->wl_next) {
                if (lp->wl_vp == vp)
                        break;
        }
        if (lp != NULL)
                /* Found it, remove this entry from the redirection list */
                *lpp = lp->wl_next;

        return (lp);
}

/*
 * Push vp onto the redirection list.
 * If it's already there move it to the front position.
 */
static void
srpush(vnode_t *vp, boolean_t is_console)
{
        iwscn_list_t    *lp;

        ASSERT(MUTEX_HELD(&iwscn_list_lock));

        /* Get the stream vnode */
        vp = str_vp(vp);
        ASSERT(vp);

        /* Check if it's already on the redirection list */
        if ((lp = srrm(vp)) == NULL) {
                lp = kmem_zalloc(sizeof (*lp), KM_SLEEP);
                lp->wl_vp = vp;
                lp->wl_is_console = is_console;
        }
        /*
         * Note that if this vnode was already somewhere on the redirection
         * list then we removed it above and are now bumping it up to the
         * front of the redirection list.
         */
        lp->wl_next = iwscn_list;
        iwscn_list = lp;
}

/*
 * This vnode is no longer a valid redirection target. Terminate any current
 * operations. If closing, wait for them to complete, then free the entry.
 * If called because a hangup has occurred, just deprecate the entry to ensure
 * it won't become the target again.
 */
void
srpop(vnode_t *vp, boolean_t close)
{
        iwscn_list_t    *tlp;           /* This target's entry */
        iwscn_list_t    *lp, **lpp;

        mutex_enter(&iwscn_list_lock);

        /*
         * Ensure no further operations are directed at the target
         * by removing it from the redirection list.
         */
        if ((tlp = srrm(vp)) == NULL) {
                /* vnode wasn't in the list */
                mutex_exit(&iwscn_list_lock);
                return;
        }
        /*
         * Terminate any current operations.
         * If we're closing, wait until they complete.
         */
        srinterrupt(tlp, close);

        if (close) {
                /* We're finished with this target */
                kmem_free(tlp, sizeof (*tlp));
        } else {
                /*
                 * Deprecate the entry. There's no need for a flag to indicate
                 * this state, it just needs to be moved to the back of the list
                 * behind the underlying console device. Since the underlying
                 * device anchors the list and is never removed, this entry can
                 * never return to the front again to become the target.
                 */
                for (lpp = &iwscn_list; (lp = *lpp) != NULL; )
                        lpp = &lp->wl_next;
                tlp->wl_next = NULL;
                *lpp = tlp;
        }
        mutex_exit(&iwscn_list_lock);
}

/* Get a hold on the current target */
static iwscn_list_t *
srhold()
{
        iwscn_list_t    *lp;

        mutex_enter(&iwscn_list_lock);
        ASSERT(iwscn_list != NULL);
        lp = iwscn_list;
        ASSERT(lp->wl_ref_cnt >= 0);
        lp->wl_ref_cnt++;
        mutex_exit(&iwscn_list_lock);

        return (lp);
}

/* Release a hold on an entry from the redirection list */
static void
srrele(iwscn_list_t *lp)
{
        ASSERT(lp != NULL);
        mutex_enter(&iwscn_list_lock);
        ASSERT(lp->wl_ref_cnt > 0);
        lp->wl_ref_cnt--;
        cv_broadcast(&iwscn_list_cv);
        mutex_exit(&iwscn_list_lock);
}

static int
iwscnread(dev_t dev, uio_t *uio, cred_t *cred)
{
        iwscn_list_t    *lp;
        int             error;

        ASSERT(getminor(dev) == 0);

        lp = srhold();
        error = strread(lp->wl_vp, uio, cred);
        srrele(lp);

        return (error);
}

static int
iwscnwrite(dev_t dev, uio_t *uio, cred_t *cred)
{
        iwscn_list_t    *lp;
        int             error;

        ASSERT(getminor(dev) == 0);

        lp = srhold();
        error = strwrite(lp->wl_vp, uio, cred);
        srrele(lp);

        return (error);
}

static int
iwscnpoll(dev_t dev, short events, int anyyet, short *reventsp,
    struct pollhead **phpp)
{
        iwscn_list_t    *lp;
        int             error;

        ASSERT(getminor(dev) == 0);

        lp = srhold();
        error = VOP_POLL(lp->wl_vp, events, anyyet, reventsp, phpp, NULL);
        srrele(lp);

        return (error);
}

static int
iwscnioctl(dev_t dev, int cmd, intptr_t arg, int flag,
    cred_t *cred, int *rvalp)
{
        iwscn_list_t    *lp;
        file_t          *f;
        char            modname[FMNAMESZ + 1] = " ";
        int             error = 0;

        ASSERT(getminor(dev) == 0);

        switch (cmd) {
        case SRIOCSREDIR:
                /* Serialize all pushes of the redirection module */
                mutex_enter(&iwscn_redirect_lock);

                /*
                 * Find the vnode corresponding to the file descriptor
                 * argument and verify that it names a stream.
                 */
                if ((f = getf((int)arg)) == NULL) {
                        mutex_exit(&iwscn_redirect_lock);
                        return (EBADF);
                }
                if (f->f_vnode->v_stream == NULL) {
                        releasef((int)arg);
                        mutex_exit(&iwscn_redirect_lock);
                        return (ENOSTR);
                }

                /*
                 * If the user is trying to redirect console output
                 * back to the underlying console via SRIOCSREDIR
                 * then they are evil and we'll stop them here.
                 */
                if (str_vp(f->f_vnode) == str_vp(rwsconsvp)) {
                        releasef((int)arg);
                        mutex_exit(&iwscn_redirect_lock);
                        return (EINVAL);
                }

                /*
                 * Check if this stream already has the redirection
                 * module pushed onto it.  I_LOOK returns an error
                 * if there are no modules pushed onto the stream.
                 */
                (void) strioctl(f->f_vnode, I_LOOK, (intptr_t)modname,
                    FKIOCTL, K_TO_K, cred, rvalp);
                if (strcmp(modname, STRREDIR_MOD) != 0) {

                        /*
                         * Push a new instance of the redirecting module onto
                         * the stream, so that its close routine can notify
                         * us when the overall stream is closed.  (In turn,
                         * we'll then remove it from the redirection list.)
                         */
                        error = strioctl(f->f_vnode, I_PUSH,
                            (intptr_t)STRREDIR_MOD, FKIOCTL, K_TO_K,
                            cred, rvalp);

                        if (error != 0) {
                                releasef((int)arg);
                                mutex_exit(&iwscn_redirect_lock);
                                return (error);
                        }
                }

                /* Push it onto the redirection stack */
                mutex_enter(&iwscn_list_lock);
                srpush(f->f_vnode, B_FALSE);
                mutex_exit(&iwscn_list_lock);

                releasef((int)arg);
                mutex_exit(&iwscn_redirect_lock);
                return (0);

        case SRIOCISREDIR:
                /*
                 * Find the vnode corresponding to the file descriptor
                 * argument and verify that it names a stream.
                 */
                if ((f = getf((int)arg)) == NULL) {
                        return (EBADF);
                }
                if (f->f_vnode->v_stream == NULL) {
                        releasef((int)arg);
                        return (ENOSTR);
                }

                lp = srhold();
                *rvalp = (str_vp(f->f_vnode) == lp->wl_vp);
                srrele(lp);
                releasef((int)arg);
                return (0);

        case I_POP:
                /*
                 * We need to serialize I_POP operations with
                 * SRIOCSREDIR operations so we don't accidently
                 * remove the redirection module from a stream.
                 */
                mutex_enter(&iwscn_redirect_lock);
                lp = srhold();

                /*
                 * Here we need to protect against process that might
                 * try to pop off the redirection module from the
                 * redirected stream.  Popping other modules is allowed.
                 *
                 * It's ok to hold iwscn_list_lock while doing the
                 * I_LOOK since it's such a simple operation.
                 */
                (void) strioctl(lp->wl_vp, I_LOOK, (intptr_t)modname,
                    FKIOCTL, K_TO_K, cred, rvalp);

                if (strcmp(STRREDIR_MOD, modname) == 0) {
                        srrele(lp);
                        mutex_exit(&iwscn_redirect_lock);
                        return (EINVAL);
                }

                /* Process the ioctl normally */
                error = VOP_IOCTL(lp->wl_vp, cmd, arg, flag, cred, rvalp, NULL);

                srrele(lp);
                mutex_exit(&iwscn_redirect_lock);
                return (error);
        }

        /* Process the ioctl normally */
        lp = srhold();
        error = VOP_IOCTL(lp->wl_vp, cmd, arg, flag, cred, rvalp, NULL);
        srrele(lp);
        return (error);
}

/* ARGSUSED */
static int
iwscnopen(dev_t *devp, int flag, int state, cred_t *cred)
{
        iwscn_list_t    *lp;
        vnode_t         *vp = rwsconsvp;

        if (state != OTYP_CHR)
                return (ENXIO);

        if (getminor(*devp) != 0)
                return (ENXIO);

        /*
         * You can't really open us until the console subsystem
         * has been configured.
         */
        if (rwsconsvp == NULL)
                return (ENXIO);

        /*
         * Check if this is the first open of this device or if
         * there is currently no redirection going on.  (Ie, we're
         * sending output to underlying console device.)
         */
        mutex_enter(&iwscn_list_lock);
        if ((iwscn_list == NULL) || (iwscn_list->wl_vp == str_vp(vp))) {
                int             error = 0;

                /* Don't hold the list lock across an VOP_OPEN */
                mutex_exit(&iwscn_list_lock);

                /*
                 * There is currently no redirection going on.
                 * pass this open request onto the console driver
                 */
                error = VOP_OPEN(&vp, flag, cred, NULL);
                if (error != 0)
                        return (error);

                /* Re-acquire the list lock */
                mutex_enter(&iwscn_list_lock);

                if (iwscn_list == NULL) {
                        /* Save this vnode on the redirection list */
                        srpush(vp, B_TRUE);
                } else {
                        /*
                         * In this case there must already be a copy of
                         * this vnode on the list, so we can free up this one.
                         */
                        (void) VOP_CLOSE(vp, flag, 1, (offset_t)0, cred, NULL);
                }
        }

        /*
         * XXX This is an ugly legacy hack that has been around
         * forever.  This code is here because this driver (the
         * iwscn driver) is a character driver layered over a
         * streams driver.
         *
         * Normally streams recieve notification whenever a process
         * closes its last reference to that stream so that it can
         * clean up any signal handling related configuration.  (Ie,
         * when a stream is configured to deliver a signal to a
         * process upon certain events.)  This is a feature supported
         * by the streams framework.
         *
         * But character/block drivers don't recieve this type
         * of notification.  A character/block driver's close routine
         * is only invoked upon the last close of the device.  This
         * is an artifact of the multiple open/single close driver
         * model currently supported by solaris.
         *
         * So a problem occurs when a character driver layers itself
         * on top of a streams driver.  Since this driver doesn't always
         * receive a close notification when a process closes its
         * last reference to it, this driver can't tell the stream
         * it's layered upon to clean up any signal handling
         * configuration for that process.
         *
         * So here we hack around that by manually cleaning up the
         * signal handling list upon each open.  It doesn't guarantee
         * that the signaling handling data stored in the stream will
         * always be up to date, but it'll be more up to date than
         * it would be if we didn't do this.
         *
         * The real way to solve this problem would be to change
         * the device framework from an multiple open/single close
         * model to a multiple open/multiple close model.  Then
         * character/block drivers could pass on close requests
         * to streams layered underneath.
         */
        str_cn_clean(VTOS(rwsconsvp)->s_commonvp);
        for (lp = iwscn_list; lp != NULL; lp = lp->wl_next) {
                ASSERT(lp->wl_vp->v_stream != NULL);
                str_cn_clean(lp->wl_vp);
        }

        mutex_exit(&iwscn_list_lock);
        return (0);
}

/* ARGSUSED */
static int
iwscnclose(dev_t dev, int flag, int state, cred_t *cred)
{
        iwscn_list_t    *lp;

        ASSERT(getminor(dev) == 0);

        if (state != OTYP_CHR)
                return (ENXIO);

        mutex_enter(&iwscn_list_lock);
        /*
         * Remove each entry from the redirection list, terminate any
         * current operations, wait for them to finish, then free the entry.
         */
        while (iwscn_list != NULL) {
                lp = srrm(iwscn_list->wl_vp);
                ASSERT(lp != NULL);
                srinterrupt(lp, B_TRUE);

                if (lp->wl_is_console == B_TRUE)
                        /* Close the underlying console device. */
                        (void) VOP_CLOSE(lp->wl_vp, 0, 1, (offset_t)0, kcred,
                            NULL);

                kmem_free(lp, sizeof (*lp));
        }
        mutex_exit(&iwscn_list_lock);
        return (0);
}

/*ARGSUSED*/
static int
iwscnattach(dev_info_t *devi, ddi_attach_cmd_t cmd)
{
        /*
         * This is a pseudo device so there will never be more than
         * one instance attached at a time
         */
        ASSERT(iwscn_dip == NULL);

        if (ddi_create_minor_node(devi, "iwscn", S_IFCHR,
            0, DDI_PSEUDO, NULL) == DDI_FAILURE) {
                return (DDI_FAILURE);
        }

        iwscn_dip = devi;
        mutex_init(&iwscn_list_lock, NULL, MUTEX_DRIVER, NULL);
        mutex_init(&iwscn_redirect_lock, NULL, MUTEX_DRIVER, NULL);
        cv_init(&iwscn_list_cv, NULL, CV_DRIVER, NULL);

        return (DDI_SUCCESS);
}

/* ARGSUSED */
static int
iwscninfo(dev_info_t *dip, ddi_info_cmd_t infocmd, void *arg, void **result)
{
        int error;

        switch (infocmd) {
        case DDI_INFO_DEVT2DEVINFO:
                if (iwscn_dip == NULL) {
                        error = DDI_FAILURE;
                } else {
                        *result = (void *)iwscn_dip;
                        error = DDI_SUCCESS;
                }
                break;
        case DDI_INFO_DEVT2INSTANCE:
                *result = (void *)0;
                error = DDI_SUCCESS;
                break;
        default:
                error = DDI_FAILURE;
        }
        return (error);
}

struct cb_ops   iwscn_cb_ops = {
        iwscnopen,              /* open */
        iwscnclose,             /* close */
        nodev,                  /* strategy */
        nodev,                  /* print */
        nodev,                  /* dump */
        iwscnread,              /* read */
        iwscnwrite,             /* write */
        iwscnioctl,             /* ioctl */
        nodev,                  /* devmap */
        nodev,                  /* mmap */
        nodev,                  /* segmap */
        iwscnpoll,              /* poll */
        ddi_prop_op,            /* cb_prop_op */
        NULL,                   /* streamtab  */
        D_MP                    /* Driver compatibility flag */
};

struct dev_ops  iwscn_ops = {
        DEVO_REV,               /* devo_rev, */
        0,                      /* refcnt  */
        iwscninfo,              /* info */
        nulldev,                /* identify */
        nulldev,                /* probe */
        iwscnattach,            /* attach */
        nodev,                  /* detach */
        nodev,                  /* reset */
        &iwscn_cb_ops,          /* driver operations */
        NULL,                   /* bus operations */
        NULL,                   /* power */
        ddi_quiesce_not_needed,         /* quiesce */
};

/*
 * Module linkage information for the kernel.
 */
static struct modldrv modldrv = {
        &mod_driverops, /* Type of module.  This one is a pseudo driver */
        "Workstation Redirection driver",
        &iwscn_ops,     /* driver ops */
};

static struct modlinkage modlinkage = {
        MODREV_1,
        &modldrv,
        NULL
};

int
_init(void)
{
        return (mod_install(&modlinkage));
}

int
_fini(void)
{
        return (EBUSY);
}

int
_info(struct modinfo *modinfop)
{
        return (mod_info(&modlinkage, modinfop));
}