kern_hhook.c

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/*-
 * Copyright (c) 2010,2013 Lawrence Stewart <lstewart@freebsd.org>
 * Copyright (c) 2010 The FreeBSD Foundation
 * All rights reserved.
 *
 * This software was developed by Lawrence Stewart while studying at the Centre
 * for Advanced Internet Architectures, Swinburne University of Technology,
 * made possible in part by grants from the FreeBSD Foundation and Cisco
 * University Research Program Fund at Community Foundation Silicon Valley.
 *
 * Portions of this software were developed at the Centre for Advanced
 * Internet Architectures, Swinburne University of Technology, Melbourne,
 * Australia by Lawrence Stewart under sponsorship from the FreeBSD Foundation.
 *
 * 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("$BSDSUniX$");

#include <sys/param.h>
#include <sys/kernel.h>
#include <sys/hhook.h>
#include <sys/khelp.h>
#include <sys/malloc.h>
#include <sys/module.h>
#include <sys/module_khelp.h>
#include <sys/osd.h>
#include <sys/queue.h>
#include <sys/refcount.h>
#include <sys/systm.h>

#include <net/vnet.h>

struct hhook {
        hhook_func_t            hhk_func;
        struct helper           *hhk_helper;
        void                    *hhk_udata;
        STAILQ_ENTRY(hhook)     hhk_next;
};

static MALLOC_DEFINE(M_HHOOK, "hhook", "Helper hooks are linked off hhook_head lists");

LIST_HEAD(hhookheadhead, hhook_head);
struct hhookheadhead hhook_head_list;
VNET_DEFINE(struct hhookheadhead, hhook_vhead_list);
#define V_hhook_vhead_list VNET(hhook_vhead_list)

static struct mtx hhook_head_list_lock;
MTX_SYSINIT(hhookheadlistlock, &hhook_head_list_lock, "hhook_head list lock",
    MTX_DEF);

/* Protected by hhook_head_list_lock. */
static uint32_t n_hhookheads;

/* Private function prototypes. */
static void hhook_head_destroy(struct hhook_head *hhh);
void khelp_new_hhook_registered(struct hhook_head *hhh, uint32_t flags);

#define HHHLIST_LOCK() mtx_lock(&hhook_head_list_lock)
#define HHHLIST_UNLOCK() mtx_unlock(&hhook_head_list_lock)
#define HHHLIST_LOCK_ASSERT() mtx_assert(&hhook_head_list_lock, MA_OWNED)

#define HHH_LOCK_INIT(hhh) rm_init(&(hhh)->hhh_lock, "hhook_head rm lock")
#define HHH_LOCK_DESTROY(hhh) rm_destroy(&(hhh)->hhh_lock)
#define HHH_WLOCK(hhh) rm_wlock(&(hhh)->hhh_lock)
#define HHH_WUNLOCK(hhh) rm_wunlock(&(hhh)->hhh_lock)
#define HHH_RLOCK(hhh, rmpt) rm_rlock(&(hhh)->hhh_lock, (rmpt))
#define HHH_RUNLOCK(hhh, rmpt) rm_runlock(&(hhh)->hhh_lock, (rmpt))

/*
 * Run all helper hook functions for a given hook point.
 */
void
hhook_run_hooks(struct hhook_head *hhh, void *ctx_data, struct osd *hosd)
{
        struct hhook *hhk;
        void *hdata;
        struct rm_priotracker rmpt;

        KASSERT(hhh->hhh_refcount > 0, ("hhook_head %p refcount is 0", hhh));

        HHH_RLOCK(hhh, &rmpt);
        STAILQ_FOREACH(hhk, &hhh->hhh_hooks, hhk_next) {
                if (hhk->hhk_helper->h_flags & HELPER_NEEDS_OSD) {
                        hdata = osd_get(OSD_KHELP, hosd, hhk->hhk_helper->h_id);
                        if (hdata == NULL)
                                continue;
                } else
                        hdata = NULL;

                /*
                 * XXXLAS: We currently ignore the int returned by the hook,
                 * but will likely want to handle it in future to allow hhook to
                 * be used like pfil and effect changes at the hhook calling
                 * site e.g. we could define a new hook type of HHOOK_TYPE_PFIL
                 * and standardise what particular return values mean and set
                 * the context data to pass exactly the same information as pfil
                 * hooks currently receive, thus replicating pfil with hhook.
                 */
                hhk->hhk_func(hhh->hhh_type, hhh->hhh_id, hhk->hhk_udata,
                    ctx_data, hdata, hosd);
        }
        HHH_RUNLOCK(hhh, &rmpt);
}

/*
 * Register a new helper hook function with a helper hook point.
 */
int
hhook_add_hook(struct hhook_head *hhh, struct hookinfo *hki, uint32_t flags)
{
        struct hhook *hhk, *tmp;
        int error;

        error = 0;

        if (hhh == NULL)
                return (ENOENT);

        hhk = malloc(sizeof(struct hhook), M_HHOOK,
            M_ZERO | ((flags & HHOOK_WAITOK) ? M_WAITOK : M_NOWAIT));

        if (hhk == NULL)
                return (ENOMEM);

        hhk->hhk_helper = hki->hook_helper;
        hhk->hhk_func = hki->hook_func;
        hhk->hhk_udata = hki->hook_udata;

        HHH_WLOCK(hhh);
        STAILQ_FOREACH(tmp, &hhh->hhh_hooks, hhk_next) {
                if (tmp->hhk_func == hki->hook_func &&
                    tmp->hhk_udata == hki->hook_udata) {
                        /* The helper hook function is already registered. */
                        error = EEXIST;
                        break;
                }
        }

        if (!error) {
                STAILQ_INSERT_TAIL(&hhh->hhh_hooks, hhk, hhk_next);
                hhh->hhh_nhooks++;
        } else
                free(hhk, M_HHOOK);

        HHH_WUNLOCK(hhh);

        return (error);
}

/*
 * Register a helper hook function with a helper hook point (including all
 * virtual instances of the hook point if it is virtualised).
 *
 * The logic is unfortunately far more complex than for
 * hhook_remove_hook_lookup() because hhook_add_hook() can call malloc() with
 * M_WAITOK and thus we cannot call hhook_add_hook() with the
 * hhook_head_list_lock held.
 *
 * The logic assembles an array of hhook_head structs that correspond to the
 * helper hook point being hooked and bumps the refcount on each (all done with
 * the hhook_head_list_lock held). The hhook_head_list_lock is then dropped, and
 * hhook_add_hook() is called and the refcount dropped for each hhook_head
 * struct in the array.
 */
int
hhook_add_hook_lookup(struct hookinfo *hki, uint32_t flags)
{
        struct hhook_head **heads_to_hook, *hhh;
        int error, i, n_heads_to_hook;

tryagain:
        error = i = 0;
        /*
         * Accessing n_hhookheads without hhook_head_list_lock held opens up a
         * race with hhook_head_register() which we are unlikely to lose, but
         * nonetheless have to cope with - hence the complex goto logic.
         */
        n_heads_to_hook = n_hhookheads;
        heads_to_hook = malloc(n_heads_to_hook * sizeof(struct hhook_head *),
            M_HHOOK, flags & HHOOK_WAITOK ? M_WAITOK : M_NOWAIT);
        if (heads_to_hook == NULL)
                return (ENOMEM);

        HHHLIST_LOCK();
        LIST_FOREACH(hhh, &hhook_head_list, hhh_next) {
                if (hhh->hhh_type == hki->hook_type &&
                    hhh->hhh_id == hki->hook_id) {
                        if (i < n_heads_to_hook) {
                                heads_to_hook[i] = hhh;
                                refcount_acquire(&heads_to_hook[i]->hhh_refcount);
                                i++;
                        } else {
                                /*
                                 * We raced with hhook_head_register() which
                                 * inserted a hhook_head that we need to hook
                                 * but did not malloc space for. Abort this run
                                 * and try again.
                                 */
                                for (i--; i >= 0; i--)
                                        refcount_release(&heads_to_hook[i]->hhh_refcount);
                                free(heads_to_hook, M_HHOOK);
                                HHHLIST_UNLOCK();
                                goto tryagain;
                        }
                }
        }
        HHHLIST_UNLOCK();

        for (i--; i >= 0; i--) {
                if (!error)
                        error = hhook_add_hook(heads_to_hook[i], hki, flags);
                refcount_release(&heads_to_hook[i]->hhh_refcount);
        }

        free(heads_to_hook, M_HHOOK);

        return (error);
}

/*
 * Remove a helper hook function from a helper hook point.
 */
int
hhook_remove_hook(struct hhook_head *hhh, struct hookinfo *hki)
{
        struct hhook *tmp;

        if (hhh == NULL)
                return (ENOENT);

        HHH_WLOCK(hhh);
        STAILQ_FOREACH(tmp, &hhh->hhh_hooks, hhk_next) {
                if (tmp->hhk_func == hki->hook_func &&
                    tmp->hhk_udata == hki->hook_udata) {
                        STAILQ_REMOVE(&hhh->hhh_hooks, tmp, hhook, hhk_next);
                        free(tmp, M_HHOOK);
                        hhh->hhh_nhooks--;
                        break;
                }
        }
        HHH_WUNLOCK(hhh);

        return (0);
}

/*
 * Remove a helper hook function from a helper hook point (including all
 * virtual instances of the hook point if it is virtualised).
 */
int
hhook_remove_hook_lookup(struct hookinfo *hki)
{
        struct hhook_head *hhh;

        HHHLIST_LOCK();
        LIST_FOREACH(hhh, &hhook_head_list, hhh_next) {
                if (hhh->hhh_type == hki->hook_type &&
                    hhh->hhh_id == hki->hook_id)
                        hhook_remove_hook(hhh, hki);
        }
        HHHLIST_UNLOCK();

        return (0);
}

/*
 * Register a new helper hook point.
 */
int
hhook_head_register(int32_t hhook_type, int32_t hhook_id, struct hhook_head **hhh,
    uint32_t flags)
{
        struct hhook_head *tmphhh;

        tmphhh = hhook_head_get(hhook_type, hhook_id);

        if (tmphhh != NULL) {
                /* Hook point previously registered. */
                hhook_head_release(tmphhh);
                return (EEXIST);
        }

        tmphhh = malloc(sizeof(struct hhook_head), M_HHOOK,
            M_ZERO | ((flags & HHOOK_WAITOK) ? M_WAITOK : M_NOWAIT));

        if (tmphhh == NULL)
                return (ENOMEM);

        tmphhh->hhh_type = hhook_type;
        tmphhh->hhh_id = hhook_id;
        tmphhh->hhh_nhooks = 0;
        STAILQ_INIT(&tmphhh->hhh_hooks);
        HHH_LOCK_INIT(tmphhh);
        refcount_init(&tmphhh->hhh_refcount, 1);

        HHHLIST_LOCK();
        if (flags & HHOOK_HEADISINVNET) {
                tmphhh->hhh_flags |= HHH_ISINVNET;
#ifdef VIMAGE
                KASSERT(curvnet != NULL, ("curvnet is NULL"));
                tmphhh->hhh_vid = (uintptr_t)curvnet;
                LIST_INSERT_HEAD(&V_hhook_vhead_list, tmphhh, hhh_vnext);
#endif
        }
        LIST_INSERT_HEAD(&hhook_head_list, tmphhh, hhh_next);
        n_hhookheads++;
        HHHLIST_UNLOCK();

        khelp_new_hhook_registered(tmphhh, flags);

        if (hhh != NULL)
                *hhh = tmphhh;
        else
                refcount_release(&tmphhh->hhh_refcount);

        return (0);
}

static void
hhook_head_destroy(struct hhook_head *hhh)
{
        struct hhook *tmp, *tmp2;

        HHHLIST_LOCK_ASSERT();
        KASSERT(n_hhookheads > 0, ("n_hhookheads should be > 0"));

        LIST_REMOVE(hhh, hhh_next);
#ifdef VIMAGE
        if (hhook_head_is_virtualised(hhh) == HHOOK_HEADISINVNET)
                LIST_REMOVE(hhh, hhh_vnext);
#endif
        HHH_WLOCK(hhh);
        STAILQ_FOREACH_SAFE(tmp, &hhh->hhh_hooks, hhk_next, tmp2)
                free(tmp, M_HHOOK);
        HHH_WUNLOCK(hhh);
        HHH_LOCK_DESTROY(hhh);
        free(hhh, M_HHOOK);
        n_hhookheads--;
}

/*
 * Remove a helper hook point.
 */
int
hhook_head_deregister(struct hhook_head *hhh)
{
        int error;

        error = 0;

        HHHLIST_LOCK();
        if (hhh == NULL)
                error = ENOENT;
        else if (hhh->hhh_refcount > 1)
                error = EBUSY;
        else
                hhook_head_destroy(hhh);
        HHHLIST_UNLOCK();

        return (error);
}

/*
 * Remove a helper hook point via a hhook_head lookup.
 */
int
hhook_head_deregister_lookup(int32_t hhook_type, int32_t hhook_id)
{
        struct hhook_head *hhh;
        int error;

        hhh = hhook_head_get(hhook_type, hhook_id);
        error = hhook_head_deregister(hhh);

        if (error == EBUSY)
                hhook_head_release(hhh);

        return (error);
}

/*
 * Lookup and return the hhook_head struct associated with the specified type
 * and id, or NULL if not found. If found, the hhook_head's refcount is bumped.
 */
struct hhook_head *
hhook_head_get(int32_t hhook_type, int32_t hhook_id)
{
        struct hhook_head *hhh;

        HHHLIST_LOCK();
        LIST_FOREACH(hhh, &hhook_head_list, hhh_next) {
                if (hhh->hhh_type == hhook_type && hhh->hhh_id == hhook_id) {
#ifdef VIMAGE
                        if (hhook_head_is_virtualised(hhh) ==
                            HHOOK_HEADISINVNET) {
                                KASSERT(curvnet != NULL, ("curvnet is NULL"));
                                if (hhh->hhh_vid != (uintptr_t)curvnet)
                                        continue;
                        }
#endif
                        refcount_acquire(&hhh->hhh_refcount);
                        break;
                }
        }
        HHHLIST_UNLOCK();

        return (hhh);
}

void
hhook_head_release(struct hhook_head *hhh)
{

        refcount_release(&hhh->hhh_refcount);
}

/*
 * Check the hhook_head private flags and return the appropriate public
 * representation of the flag to the caller. The function is implemented in a
 * way that allows us to cope with other subsystems becoming virtualised in the
 * future.
 */
uint32_t
hhook_head_is_virtualised(struct hhook_head *hhh)
{
        uint32_t ret;

        ret = 0;

        if (hhh != NULL) {
                if (hhh->hhh_flags & HHH_ISINVNET)
                        ret = HHOOK_HEADISINVNET;
        }

        return (ret);
}

uint32_t
hhook_head_is_virtualised_lookup(int32_t hook_type, int32_t hook_id)
{
        struct hhook_head *hhh;
        uint32_t ret;

        hhh = hhook_head_get(hook_type, hook_id);

        if (hhh == NULL)
                return (0);

        ret = hhook_head_is_virtualised(hhh);
        hhook_head_release(hhh);

        return (ret);
}

/*
 * Vnet created and being initialised.
 */
static void
hhook_vnet_init(const void *unused __unused)
{

        LIST_INIT(&V_hhook_vhead_list);
}

/*
 * Vnet being torn down and destroyed.
 */
static void
hhook_vnet_uninit(const void *unused __unused)
{
        struct hhook_head *hhh, *tmphhh;

        /*
         * If subsystems which export helper hook points use the hhook KPI
         * correctly, the loop below should have no work to do because the
         * subsystem should have already called hhook_head_deregister().
         */
        HHHLIST_LOCK();
        LIST_FOREACH_SAFE(hhh, &V_hhook_vhead_list, hhh_vnext, tmphhh) {
                printf("%s: hhook_head type=%d, id=%d cleanup required\n",
                    __func__, hhh->hhh_type, hhh->hhh_id);
                hhook_head_destroy(hhh);
        }
        HHHLIST_UNLOCK();
}


/*
 * When a vnet is created and being initialised, init the V_hhook_vhead_list.
 */
VNET_SYSINIT(hhook_vnet_init, SI_SUB_MBUF, SI_ORDER_FIRST,
    hhook_vnet_init, NULL);

/*
 * The hhook KPI provides a mechanism for subsystems which export helper hook
 * points to clean up on vnet tear down, but in case the KPI is misused,
 * provide a function to clean up and free memory for a vnet being destroyed.
 */
VNET_SYSUNINIT(hhook_vnet_uninit, SI_SUB_MBUF, SI_ORDER_ANY,
    hhook_vnet_uninit, NULL);