kern_hhook.c

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    1 /*-
    2  * Copyright (c) 2010,2013 Lawrence Stewart <lstewart@freebsd.org>
    3  * Copyright (c) 2010 The FreeBSD Foundation
    4  * All rights reserved.
    5  *
    6  * This software was developed by Lawrence Stewart while studying at the Centre
    7  * for Advanced Internet Architectures, Swinburne University of Technology,
    8  * made possible in part by grants from the FreeBSD Foundation and Cisco
    9  * University Research Program Fund at Community Foundation Silicon Valley.
   10  *
   11  * Portions of this software were developed at the Centre for Advanced
   12  * Internet Architectures, Swinburne University of Technology, Melbourne,
   13  * Australia by Lawrence Stewart under sponsorship from the FreeBSD Foundation.
   14  *
   15  * Redistribution and use in source and binary forms, with or without
   16  * modification, are permitted provided that the following conditions
   17  * are met:
   18  * 1. Redistributions of source code must retain the above copyright
   19  *    notice, this list of conditions and the following disclaimer.
   20  * 2. Redistributions in binary form must reproduce the above copyright
   21  *    notice, this list of conditions and the following disclaimer in the
   22  *    documentation and/or other materials provided with the distribution.
   23  *
   24  * THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
   25  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
   26  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
   27  * ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
   28  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
   29  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
   30  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
   31  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
   32  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
   33  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
   34  * SUCH DAMAGE.
   35  */
   36 
   37 #include <sys/cdefs.h>
   38 __FBSDID("$FreeBSD: releng/11.1/sys/kern/kern_hhook.c 302054 2016-06-21 13:48:49Z bz $");
   39 
   40 #include <sys/param.h>
   41 #include <sys/kernel.h>
   42 #include <sys/hhook.h>
   43 #include <sys/khelp.h>
   44 #include <sys/malloc.h>
   45 #include <sys/module.h>
   46 #include <sys/module_khelp.h>
   47 #include <sys/osd.h>
   48 #include <sys/queue.h>
   49 #include <sys/refcount.h>
   50 #include <sys/systm.h>
   51 
   52 #include <net/vnet.h>
   53 
   54 struct hhook {
   55         hhook_func_t            hhk_func;
   56         struct helper           *hhk_helper;
   57         void                    *hhk_udata;
   58         STAILQ_ENTRY(hhook)     hhk_next;
   59 };
   60 
   61 static MALLOC_DEFINE(M_HHOOK, "hhook", "Helper hooks are linked off hhook_head lists");
   62 
   63 LIST_HEAD(hhookheadhead, hhook_head);
   64 struct hhookheadhead hhook_head_list;
   65 VNET_DEFINE(struct hhookheadhead, hhook_vhead_list);
   66 #define V_hhook_vhead_list VNET(hhook_vhead_list)
   67 
   68 static struct mtx hhook_head_list_lock;
   69 MTX_SYSINIT(hhookheadlistlock, &hhook_head_list_lock, "hhook_head list lock",
   70     MTX_DEF);
   71 
   72 /* Protected by hhook_head_list_lock. */
   73 static uint32_t n_hhookheads;
   74 
   75 /* Private function prototypes. */
   76 static void hhook_head_destroy(struct hhook_head *hhh);
   77 void khelp_new_hhook_registered(struct hhook_head *hhh, uint32_t flags);
   78 
   79 #define HHHLIST_LOCK() mtx_lock(&hhook_head_list_lock)
   80 #define HHHLIST_UNLOCK() mtx_unlock(&hhook_head_list_lock)
   81 #define HHHLIST_LOCK_ASSERT() mtx_assert(&hhook_head_list_lock, MA_OWNED)
   82 
   83 #define HHH_LOCK_INIT(hhh) rm_init(&(hhh)->hhh_lock, "hhook_head rm lock")
   84 #define HHH_LOCK_DESTROY(hhh) rm_destroy(&(hhh)->hhh_lock)
   85 #define HHH_WLOCK(hhh) rm_wlock(&(hhh)->hhh_lock)
   86 #define HHH_WUNLOCK(hhh) rm_wunlock(&(hhh)->hhh_lock)
   87 #define HHH_RLOCK(hhh, rmpt) rm_rlock(&(hhh)->hhh_lock, (rmpt))
   88 #define HHH_RUNLOCK(hhh, rmpt) rm_runlock(&(hhh)->hhh_lock, (rmpt))
   89 
   90 /*
   91  * Run all helper hook functions for a given hook point.
   92  */
   93 void
   94 hhook_run_hooks(struct hhook_head *hhh, void *ctx_data, struct osd *hosd)
   95 {
   96         struct hhook *hhk;
   97         void *hdata;
   98         struct rm_priotracker rmpt;
   99 
  100         KASSERT(hhh->hhh_refcount > 0, ("hhook_head %p refcount is 0", hhh));
  101 
  102         HHH_RLOCK(hhh, &rmpt);
  103         STAILQ_FOREACH(hhk, &hhh->hhh_hooks, hhk_next) {
  104                 if (hhk->hhk_helper != NULL &&
  105                     hhk->hhk_helper->h_flags & HELPER_NEEDS_OSD) {
  106                         hdata = osd_get(OSD_KHELP, hosd, hhk->hhk_helper->h_id);
  107                         if (hdata == NULL)
  108                                 continue;
  109                 } else
  110                         hdata = NULL;
  111 
  112                 /*
  113                  * XXXLAS: We currently ignore the int returned by the hook,
  114                  * but will likely want to handle it in future to allow hhook to
  115                  * be used like pfil and effect changes at the hhook calling
  116                  * site e.g. we could define a new hook type of HHOOK_TYPE_PFIL
  117                  * and standardise what particular return values mean and set
  118                  * the context data to pass exactly the same information as pfil
  119                  * hooks currently receive, thus replicating pfil with hhook.
  120                  */
  121                 hhk->hhk_func(hhh->hhh_type, hhh->hhh_id, hhk->hhk_udata,
  122                     ctx_data, hdata, hosd);
  123         }
  124         HHH_RUNLOCK(hhh, &rmpt);
  125 }
  126 
  127 /*
  128  * Register a new helper hook function with a helper hook point.
  129  */
  130 int
  131 hhook_add_hook(struct hhook_head *hhh, struct hookinfo *hki, uint32_t flags)
  132 {
  133         struct hhook *hhk, *tmp;
  134         int error;
  135 
  136         error = 0;
  137 
  138         if (hhh == NULL)
  139                 return (ENOENT);
  140 
  141         hhk = malloc(sizeof(struct hhook), M_HHOOK,
  142             M_ZERO | ((flags & HHOOK_WAITOK) ? M_WAITOK : M_NOWAIT));
  143 
  144         if (hhk == NULL)
  145                 return (ENOMEM);
  146 
  147         hhk->hhk_helper = hki->hook_helper;
  148         hhk->hhk_func = hki->hook_func;
  149         hhk->hhk_udata = hki->hook_udata;
  150 
  151         HHH_WLOCK(hhh);
  152         STAILQ_FOREACH(tmp, &hhh->hhh_hooks, hhk_next) {
  153                 if (tmp->hhk_func == hki->hook_func &&
  154                     tmp->hhk_udata == hki->hook_udata) {
  155                         /* The helper hook function is already registered. */
  156                         error = EEXIST;
  157                         break;
  158                 }
  159         }
  160 
  161         if (!error) {
  162                 STAILQ_INSERT_TAIL(&hhh->hhh_hooks, hhk, hhk_next);
  163                 hhh->hhh_nhooks++;
  164         } else
  165                 free(hhk, M_HHOOK);
  166 
  167         HHH_WUNLOCK(hhh);
  168 
  169         return (error);
  170 }
  171 
  172 /*
  173  * Register a helper hook function with a helper hook point (including all
  174  * virtual instances of the hook point if it is virtualised).
  175  *
  176  * The logic is unfortunately far more complex than for
  177  * hhook_remove_hook_lookup() because hhook_add_hook() can call malloc() with
  178  * M_WAITOK and thus we cannot call hhook_add_hook() with the
  179  * hhook_head_list_lock held.
  180  *
  181  * The logic assembles an array of hhook_head structs that correspond to the
  182  * helper hook point being hooked and bumps the refcount on each (all done with
  183  * the hhook_head_list_lock held). The hhook_head_list_lock is then dropped, and
  184  * hhook_add_hook() is called and the refcount dropped for each hhook_head
  185  * struct in the array.
  186  */
  187 int
  188 hhook_add_hook_lookup(struct hookinfo *hki, uint32_t flags)
  189 {
  190         struct hhook_head **heads_to_hook, *hhh;
  191         int error, i, n_heads_to_hook;
  192 
  193 tryagain:
  194         error = i = 0;
  195         /*
  196          * Accessing n_hhookheads without hhook_head_list_lock held opens up a
  197          * race with hhook_head_register() which we are unlikely to lose, but
  198          * nonetheless have to cope with - hence the complex goto logic.
  199          */
  200         n_heads_to_hook = n_hhookheads;
  201         heads_to_hook = malloc(n_heads_to_hook * sizeof(struct hhook_head *),
  202             M_HHOOK, flags & HHOOK_WAITOK ? M_WAITOK : M_NOWAIT);
  203         if (heads_to_hook == NULL)
  204                 return (ENOMEM);
  205 
  206         HHHLIST_LOCK();
  207         LIST_FOREACH(hhh, &hhook_head_list, hhh_next) {
  208                 if (hhh->hhh_type == hki->hook_type &&
  209                     hhh->hhh_id == hki->hook_id) {
  210                         if (i < n_heads_to_hook) {
  211                                 heads_to_hook[i] = hhh;
  212                                 refcount_acquire(&heads_to_hook[i]->hhh_refcount);
  213                                 i++;
  214                         } else {
  215                                 /*
  216                                  * We raced with hhook_head_register() which
  217                                  * inserted a hhook_head that we need to hook
  218                                  * but did not malloc space for. Abort this run
  219                                  * and try again.
  220                                  */
  221                                 for (i--; i >= 0; i--)
  222                                         refcount_release(&heads_to_hook[i]->hhh_refcount);
  223                                 free(heads_to_hook, M_HHOOK);
  224                                 HHHLIST_UNLOCK();
  225                                 goto tryagain;
  226                         }
  227                 }
  228         }
  229         HHHLIST_UNLOCK();
  230 
  231         for (i--; i >= 0; i--) {
  232                 if (!error)
  233                         error = hhook_add_hook(heads_to_hook[i], hki, flags);
  234                 refcount_release(&heads_to_hook[i]->hhh_refcount);
  235         }
  236 
  237         free(heads_to_hook, M_HHOOK);
  238 
  239         return (error);
  240 }
  241 
  242 /*
  243  * Remove a helper hook function from a helper hook point.
  244  */
  245 int
  246 hhook_remove_hook(struct hhook_head *hhh, struct hookinfo *hki)
  247 {
  248         struct hhook *tmp;
  249 
  250         if (hhh == NULL)
  251                 return (ENOENT);
  252 
  253         HHH_WLOCK(hhh);
  254         STAILQ_FOREACH(tmp, &hhh->hhh_hooks, hhk_next) {
  255                 if (tmp->hhk_func == hki->hook_func &&
  256                     tmp->hhk_udata == hki->hook_udata) {
  257                         STAILQ_REMOVE(&hhh->hhh_hooks, tmp, hhook, hhk_next);
  258                         free(tmp, M_HHOOK);
  259                         hhh->hhh_nhooks--;
  260                         break;
  261                 }
  262         }
  263         HHH_WUNLOCK(hhh);
  264 
  265         return (0);
  266 }
  267 
  268 /*
  269  * Remove a helper hook function from a helper hook point (including all
  270  * virtual instances of the hook point if it is virtualised).
  271  */
  272 int
  273 hhook_remove_hook_lookup(struct hookinfo *hki)
  274 {
  275         struct hhook_head *hhh;
  276 
  277         HHHLIST_LOCK();
  278         LIST_FOREACH(hhh, &hhook_head_list, hhh_next) {
  279                 if (hhh->hhh_type == hki->hook_type &&
  280                     hhh->hhh_id == hki->hook_id)
  281                         hhook_remove_hook(hhh, hki);
  282         }
  283         HHHLIST_UNLOCK();
  284 
  285         return (0);
  286 }
  287 
  288 /*
  289  * Register a new helper hook point.
  290  */
  291 int
  292 hhook_head_register(int32_t hhook_type, int32_t hhook_id, struct hhook_head **hhh,
  293     uint32_t flags)
  294 {
  295         struct hhook_head *tmphhh;
  296 
  297         tmphhh = hhook_head_get(hhook_type, hhook_id);
  298 
  299         if (tmphhh != NULL) {
  300                 /* Hook point previously registered. */
  301                 hhook_head_release(tmphhh);
  302                 return (EEXIST);
  303         }
  304 
  305         tmphhh = malloc(sizeof(struct hhook_head), M_HHOOK,
  306             M_ZERO | ((flags & HHOOK_WAITOK) ? M_WAITOK : M_NOWAIT));
  307 
  308         if (tmphhh == NULL)
  309                 return (ENOMEM);
  310 
  311         tmphhh->hhh_type = hhook_type;
  312         tmphhh->hhh_id = hhook_id;
  313         tmphhh->hhh_nhooks = 0;
  314         STAILQ_INIT(&tmphhh->hhh_hooks);
  315         HHH_LOCK_INIT(tmphhh);
  316         refcount_init(&tmphhh->hhh_refcount, 1);
  317 
  318         HHHLIST_LOCK();
  319         if (flags & HHOOK_HEADISINVNET) {
  320                 tmphhh->hhh_flags |= HHH_ISINVNET;
  321 #ifdef VIMAGE
  322                 KASSERT(curvnet != NULL, ("curvnet is NULL"));
  323                 tmphhh->hhh_vid = (uintptr_t)curvnet;
  324                 LIST_INSERT_HEAD(&V_hhook_vhead_list, tmphhh, hhh_vnext);
  325 #endif
  326         }
  327         LIST_INSERT_HEAD(&hhook_head_list, tmphhh, hhh_next);
  328         n_hhookheads++;
  329         HHHLIST_UNLOCK();
  330 
  331         khelp_new_hhook_registered(tmphhh, flags);
  332 
  333         if (hhh != NULL)
  334                 *hhh = tmphhh;
  335         else
  336                 refcount_release(&tmphhh->hhh_refcount);
  337 
  338         return (0);
  339 }
  340 
  341 static void
  342 hhook_head_destroy(struct hhook_head *hhh)
  343 {
  344         struct hhook *tmp, *tmp2;
  345 
  346         HHHLIST_LOCK_ASSERT();
  347         KASSERT(n_hhookheads > 0, ("n_hhookheads should be > 0"));
  348 
  349         LIST_REMOVE(hhh, hhh_next);
  350 #ifdef VIMAGE
  351         if (hhook_head_is_virtualised(hhh) == HHOOK_HEADISINVNET)
  352                 LIST_REMOVE(hhh, hhh_vnext);
  353 #endif
  354         HHH_WLOCK(hhh);
  355         STAILQ_FOREACH_SAFE(tmp, &hhh->hhh_hooks, hhk_next, tmp2)
  356                 free(tmp, M_HHOOK);
  357         HHH_WUNLOCK(hhh);
  358         HHH_LOCK_DESTROY(hhh);
  359         free(hhh, M_HHOOK);
  360         n_hhookheads--;
  361 }
  362 
  363 /*
  364  * Remove a helper hook point.
  365  */
  366 int
  367 hhook_head_deregister(struct hhook_head *hhh)
  368 {
  369         int error;
  370 
  371         error = 0;
  372 
  373         HHHLIST_LOCK();
  374         if (hhh == NULL)
  375                 error = ENOENT;
  376         else if (hhh->hhh_refcount > 1)
  377                 error = EBUSY;
  378         else
  379                 hhook_head_destroy(hhh);
  380         HHHLIST_UNLOCK();
  381 
  382         return (error);
  383 }
  384 
  385 /*
  386  * Remove a helper hook point via a hhook_head lookup.
  387  */
  388 int
  389 hhook_head_deregister_lookup(int32_t hhook_type, int32_t hhook_id)
  390 {
  391         struct hhook_head *hhh;
  392         int error;
  393 
  394         hhh = hhook_head_get(hhook_type, hhook_id);
  395         error = hhook_head_deregister(hhh);
  396 
  397         if (error == EBUSY)
  398                 hhook_head_release(hhh);
  399 
  400         return (error);
  401 }
  402 
  403 /*
  404  * Lookup and return the hhook_head struct associated with the specified type
  405  * and id, or NULL if not found. If found, the hhook_head's refcount is bumped.
  406  */
  407 struct hhook_head *
  408 hhook_head_get(int32_t hhook_type, int32_t hhook_id)
  409 {
  410         struct hhook_head *hhh;
  411 
  412         HHHLIST_LOCK();
  413         LIST_FOREACH(hhh, &hhook_head_list, hhh_next) {
  414                 if (hhh->hhh_type == hhook_type && hhh->hhh_id == hhook_id) {
  415 #ifdef VIMAGE
  416                         if (hhook_head_is_virtualised(hhh) ==
  417                             HHOOK_HEADISINVNET) {
  418                                 KASSERT(curvnet != NULL, ("curvnet is NULL"));
  419                                 if (hhh->hhh_vid != (uintptr_t)curvnet)
  420                                         continue;
  421                         }
  422 #endif
  423                         refcount_acquire(&hhh->hhh_refcount);
  424                         break;
  425                 }
  426         }
  427         HHHLIST_UNLOCK();
  428 
  429         return (hhh);
  430 }
  431 
  432 void
  433 hhook_head_release(struct hhook_head *hhh)
  434 {
  435 
  436         refcount_release(&hhh->hhh_refcount);
  437 }
  438 
  439 /*
  440  * Check the hhook_head private flags and return the appropriate public
  441  * representation of the flag to the caller. The function is implemented in a
  442  * way that allows us to cope with other subsystems becoming virtualised in the
  443  * future.
  444  */
  445 uint32_t
  446 hhook_head_is_virtualised(struct hhook_head *hhh)
  447 {
  448         uint32_t ret;
  449 
  450         ret = 0;
  451 
  452         if (hhh != NULL) {
  453                 if (hhh->hhh_flags & HHH_ISINVNET)
  454                         ret = HHOOK_HEADISINVNET;
  455         }
  456 
  457         return (ret);
  458 }
  459 
  460 uint32_t
  461 hhook_head_is_virtualised_lookup(int32_t hook_type, int32_t hook_id)
  462 {
  463         struct hhook_head *hhh;
  464         uint32_t ret;
  465 
  466         hhh = hhook_head_get(hook_type, hook_id);
  467 
  468         if (hhh == NULL)
  469                 return (0);
  470 
  471         ret = hhook_head_is_virtualised(hhh);
  472         hhook_head_release(hhh);
  473 
  474         return (ret);
  475 }
  476 
  477 /*
  478  * Vnet created and being initialised.
  479  */
  480 static void
  481 hhook_vnet_init(const void *unused __unused)
  482 {
  483 
  484         LIST_INIT(&V_hhook_vhead_list);
  485 }
  486 
  487 /*
  488  * Vnet being torn down and destroyed.
  489  */
  490 static void
  491 hhook_vnet_uninit(const void *unused __unused)
  492 {
  493         struct hhook_head *hhh, *tmphhh;
  494 
  495         /*
  496          * If subsystems which export helper hook points use the hhook KPI
  497          * correctly, the loop below should have no work to do because the
  498          * subsystem should have already called hhook_head_deregister().
  499          */
  500         HHHLIST_LOCK();
  501         LIST_FOREACH_SAFE(hhh, &V_hhook_vhead_list, hhh_vnext, tmphhh) {
  502                 printf("%s: hhook_head type=%d, id=%d cleanup required\n",
  503                     __func__, hhh->hhh_type, hhh->hhh_id);
  504                 hhook_head_destroy(hhh);
  505         }
  506         HHHLIST_UNLOCK();
  507 }
  508 
  509 
  510 /*
  511  * When a vnet is created and being initialised, init the V_hhook_vhead_list.
  512  */
  513 VNET_SYSINIT(hhook_vnet_init, SI_SUB_INIT_IF, SI_ORDER_FIRST,
  514     hhook_vnet_init, NULL);
  515 
  516 /*
  517  * The hhook KPI provides a mechanism for subsystems which export helper hook
  518  * points to clean up on vnet tear down, but in case the KPI is misused,
  519  * provide a function to clean up and free memory for a vnet being destroyed.
  520  */
  521 VNET_SYSUNINIT(hhook_vnet_uninit, SI_SUB_INIT_IF, SI_ORDER_FIRST,
  522     hhook_vnet_uninit, NULL);
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FreeBSD/Linux Kernel Cross Reference sys/kern/kern_hhook.c

FreeBSD/Linux Kernel Cross Reference
sys/kern/kern_hhook.c
