sys/kern/kern_hook.c

/*        $NetBSD: kern_hook.c,v 1.15 2024/01/17 10:18:41 hannken Exp $         */

/*-
 * Copyright (c) 1997, 1998, 1999, 2002, 2007, 2008 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 Luke Mewburn.
 *
 * 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.
 */

#include <sys/cdefs.h>
__KERNEL_RCSID(0, "$NetBSD: kern_hook.c,v 1.15 2024/01/17 10:18:41 hannken Exp $");

#include <sys/param.h>

#include <sys/condvar.h>
#include <sys/cpu.h>
#include <sys/device.h>
#include <sys/exec.h>
#include <sys/hook.h>
#include <sys/kmem.h>
#include <sys/malloc.h>
#include <sys/once.h>
#include <sys/rwlock.h>
#include <sys/systm.h>

/*
 * A generic linear hook.
 */
struct hook_desc {
          LIST_ENTRY(hook_desc) hk_list;
          void      (*hk_fn)(void *);
          void      *hk_arg;
};
typedef LIST_HEAD(, hook_desc) hook_list_t;

enum hook_list_st {
          HKLIST_IDLE,
          HKLIST_INUSE,
};

struct khook_list {
          hook_list_t          hl_list;
          kmutex_t   hl_lock;
          kmutex_t  *hl_cvlock;
          struct lwp          *hl_lwp;
          kcondvar_t           hl_cv;
          enum hook_list_st
                               hl_state;
          khook_t             *hl_active_hk;
          char                 hl_namebuf[HOOKNAMSIZ];
};

int       powerhook_debug = 0;

static ONCE_DECL(hook_control);
static krwlock_t exithook_lock;
static krwlock_t forkhook_lock;

static int
hook_init(void)
{

          rw_init(&exithook_lock);
          rw_init(&forkhook_lock);

          return 0;
}

static void *
hook_establish(hook_list_t *list, krwlock_t *lock,
    void (*fn)(void *), void *arg)
{
          struct hook_desc *hd;

          RUN_ONCE(&hook_control, hook_init);

          hd = malloc(sizeof(*hd), M_DEVBUF, M_NOWAIT);
          if (hd != NULL) {
                    if (lock)
                              rw_enter(lock, RW_WRITER);
                    hd->hk_fn = fn;
                    hd->hk_arg = arg;
                    LIST_INSERT_HEAD(list, hd, hk_list);
                    if (lock)
                              rw_exit(lock);
          }

          return (hd);
}

static void
hook_disestablish(hook_list_t *list, krwlock_t *lock, void *vhook)
{

          if (lock)
                    rw_enter(lock, RW_WRITER);
#ifdef DIAGNOSTIC
          struct hook_desc *hd;

          LIST_FOREACH(hd, list, hk_list) {
                if (hd == vhook)
                              break;
          }

          if (hd == NULL)
                    panic("hook_disestablish: hook %p not established", vhook);
#endif
          LIST_REMOVE((struct hook_desc *)vhook, hk_list);
          free(vhook, M_DEVBUF);
          if (lock)
                    rw_exit(lock);
}

static void
hook_destroy(hook_list_t *list)
{
          struct hook_desc *hd;

          while ((hd = LIST_FIRST(list)) != NULL) {
                    LIST_REMOVE(hd, hk_list);
                    free(hd, M_DEVBUF);
          }
}

static void
hook_proc_run(hook_list_t *list, krwlock_t *lock, struct proc *p)
{
          struct hook_desc *hd;

          RUN_ONCE(&hook_control, hook_init);

          if (lock)
                    rw_enter(lock, RW_READER);
          LIST_FOREACH(hd, list, hk_list) {
                    __FPTRCAST(void (*)(struct proc *, void *), *hd->hk_fn)(p,
                        hd->hk_arg);
          }
          if (lock)
                    rw_exit(lock);
}

/*
 * "Shutdown hook" types, functions, and variables.
 *
 * Should be invoked immediately before the
 * system is halted or rebooted, i.e. after file systems unmounted,
 * after crash dump done, etc.
 *
 * Each shutdown hook is removed from the list before it's run, so that
 * it won't be run again.
 */

static hook_list_t shutdownhook_list = LIST_HEAD_INITIALIZER(shutdownhook_list);

void *
shutdownhook_establish(void (*fn)(void *), void *arg)
{
          return hook_establish(&shutdownhook_list, NULL, fn, arg);
}

void
shutdownhook_disestablish(void *vhook)
{
          hook_disestablish(&shutdownhook_list, NULL, vhook);
}

/*
 * Run shutdown hooks.  Should be invoked immediately before the
 * system is halted or rebooted, i.e. after file systems unmounted,
 * after crash dump done, etc.
 *
 * Each shutdown hook is removed from the list before it's run, so that
 * it won't be run again.
 */
void
doshutdownhooks(void)
{
          struct hook_desc *dp;

          while ((dp = LIST_FIRST(&shutdownhook_list)) != NULL) {
                    LIST_REMOVE(dp, hk_list);
                    (*dp->hk_fn)(dp->hk_arg);
#if 0
                    /*
                     * Don't bother freeing the hook structure,, since we may
                     * be rebooting because of a memory corruption problem,
                     * and this might only make things worse.  It doesn't
                     * matter, anyway, since the system is just about to
                     * reboot.
                     */
                    free(dp, M_DEVBUF);
#endif
          }
}

/*
 * "Mountroot hook" types, functions, and variables.
 */

static hook_list_t mountroothook_list=LIST_HEAD_INITIALIZER(mountroothook_list);

void *
mountroothook_establish(void (*fn)(device_t), device_t dev)
{
          return hook_establish(&mountroothook_list, NULL,
              __FPTRCAST(void (*), fn), dev);
}

void
mountroothook_disestablish(void *vhook)
{
          hook_disestablish(&mountroothook_list, NULL, vhook);
}

void
mountroothook_destroy(void)
{
          hook_destroy(&mountroothook_list);
}

void
domountroothook(device_t therootdev)
{
          struct hook_desc *hd;

          LIST_FOREACH(hd, &mountroothook_list, hk_list) {
                    if (hd->hk_arg == therootdev) {
                              (*hd->hk_fn)(hd->hk_arg);
                              return;
                    }
          }
}

static hook_list_t exechook_list = LIST_HEAD_INITIALIZER(exechook_list);

void *
exechook_establish(void (*fn)(struct proc *, void *), void *arg)
{
          return hook_establish(&exechook_list, &exec_lock,
                    __FPTRCAST(void (*)(void *), fn), arg);
}

void
exechook_disestablish(void *vhook)
{
          hook_disestablish(&exechook_list, &exec_lock, vhook);
}

/*
 * Run exec hooks.
 */
void
doexechooks(struct proc *p)
{
          KASSERT(rw_lock_held(&exec_lock));

          hook_proc_run(&exechook_list, NULL, p);
}

static hook_list_t exithook_list = LIST_HEAD_INITIALIZER(exithook_list);

void *
exithook_establish(void (*fn)(struct proc *, void *), void *arg)
{

          return hook_establish(&exithook_list, &exithook_lock,
              __FPTRCAST(void (*)(void *), fn), arg);
}

void
exithook_disestablish(void *vhook)
{

          hook_disestablish(&exithook_list, &exithook_lock, vhook);
}

/*
 * Run exit hooks.
 */
void
doexithooks(struct proc *p)
{
          hook_proc_run(&exithook_list, &exithook_lock, p);
}

static hook_list_t forkhook_list = LIST_HEAD_INITIALIZER(forkhook_list);

void *
forkhook_establish(void (*fn)(struct proc *, struct proc *))
{
          return hook_establish(&forkhook_list, &forkhook_lock,
              __FPTRCAST(void (*)(void *), fn), NULL);
}

void
forkhook_disestablish(void *vhook)
{
          hook_disestablish(&forkhook_list, &forkhook_lock, vhook);
}

/*
 * Run fork hooks.
 */
void
doforkhooks(struct proc *p2, struct proc *p1)
{
          struct hook_desc *hd;

          RUN_ONCE(&hook_control, hook_init);

          rw_enter(&forkhook_lock, RW_READER);
          LIST_FOREACH(hd, &forkhook_list, hk_list) {
                    __FPTRCAST(void (*)(struct proc *, struct proc *), *hd->hk_fn)
                        (p2, p1);
          }
          rw_exit(&forkhook_lock);
}

static hook_list_t critpollhook_list = LIST_HEAD_INITIALIZER(critpollhook_list);

void *
critpollhook_establish(void (*fn)(void *), void *arg)
{
          return hook_establish(&critpollhook_list, NULL, fn, arg);
}

void
critpollhook_disestablish(void *vhook)
{
          hook_disestablish(&critpollhook_list, NULL, vhook);
}

/*
 * Run critical polling hooks.
 */
void
docritpollhooks(void)
{
          struct hook_desc *hd;

          LIST_FOREACH(hd, &critpollhook_list, hk_list) {
                    (*hd->hk_fn)(hd->hk_arg);
          }
}

/*
 * "Power hook" types, functions, and variables.
 * The list of power hooks is kept ordered with the last registered hook
 * first.
 * When running the hooks on power down the hooks are called in reverse
 * registration order, when powering up in registration order.
 */
struct powerhook_desc {
          TAILQ_ENTRY(powerhook_desc) sfd_list;
          void      (*sfd_fn)(int, void *);
          void      *sfd_arg;
          char      sfd_name[16];
};

static TAILQ_HEAD(powerhook_head, powerhook_desc) powerhook_list =
    TAILQ_HEAD_INITIALIZER(powerhook_list);

void *
powerhook_establish(const char *name, void (*fn)(int, void *), void *arg)
{
          struct powerhook_desc *ndp;

          ndp = (struct powerhook_desc *)
              malloc(sizeof(*ndp), M_DEVBUF, M_NOWAIT);
          if (ndp == NULL)
                    return (NULL);

          ndp->sfd_fn = fn;
          ndp->sfd_arg = arg;
          strlcpy(ndp->sfd_name, name, sizeof(ndp->sfd_name));
          TAILQ_INSERT_HEAD(&powerhook_list, ndp, sfd_list);

          aprint_error("%s: WARNING: powerhook_establish is deprecated\n", name);
          return (ndp);
}

void
powerhook_disestablish(void *vhook)
{
#ifdef DIAGNOSTIC
          struct powerhook_desc *dp;

          TAILQ_FOREACH(dp, &powerhook_list, sfd_list)
                if (dp == vhook)
                              goto found;
          panic("powerhook_disestablish: hook %p not established", vhook);
 found:
#endif

          TAILQ_REMOVE(&powerhook_list, (struct powerhook_desc *)vhook,
              sfd_list);
          free(vhook, M_DEVBUF);
}

/*
 * Run power hooks.
 */
void
dopowerhooks(int why)
{
          struct powerhook_desc *dp;
          const char *why_name;
          static const char * pwr_names[] = {PWR_NAMES};
          why_name = why < __arraycount(pwr_names) ? pwr_names[why] : "???";

          if (why == PWR_RESUME || why == PWR_SOFTRESUME) {
                    TAILQ_FOREACH_REVERSE(dp, &powerhook_list, powerhook_head,
                        sfd_list)
                    {
                              if (powerhook_debug)
                                        printf("dopowerhooks %s: %s (%p)\n",
                                            why_name, dp->sfd_name, dp);
                              (*dp->sfd_fn)(why, dp->sfd_arg);
                    }
          } else {
                    TAILQ_FOREACH(dp, &powerhook_list, sfd_list) {
                              if (powerhook_debug)
                                        printf("dopowerhooks %s: %s (%p)\n",
                                            why_name, dp->sfd_name, dp);
                              (*dp->sfd_fn)(why, dp->sfd_arg);
                    }
          }

          if (powerhook_debug)
                    printf("dopowerhooks: %s done\n", why_name);
}

/*
 * A simple linear hook.
 */

khook_list_t *
simplehook_create(int ipl, const char *wmsg)
{
          khook_list_t *l;

          l = kmem_zalloc(sizeof(*l), KM_SLEEP);

          mutex_init(&l->hl_lock, MUTEX_DEFAULT, ipl);
          strlcpy(l->hl_namebuf, wmsg, sizeof(l->hl_namebuf));
          cv_init(&l->hl_cv, l->hl_namebuf);
          LIST_INIT(&l->hl_list);
          l->hl_state = HKLIST_IDLE;

          return l;
}

void
simplehook_destroy(khook_list_t *l)
{
          struct hook_desc *hd;

          KASSERT(l->hl_state == HKLIST_IDLE);

          while ((hd = LIST_FIRST(&l->hl_list)) != NULL) {
                    LIST_REMOVE(hd, hk_list);
                    kmem_free(hd, sizeof(*hd));
          }

          cv_destroy(&l->hl_cv);
          mutex_destroy(&l->hl_lock);
          kmem_free(l, sizeof(*l));
}

int
simplehook_dohooks(khook_list_t *l)
{
          struct hook_desc *hd, *nexthd;
          kmutex_t *cv_lock;
          void (*fn)(void *);
          void *arg;

          mutex_enter(&l->hl_lock);
          if (l->hl_state != HKLIST_IDLE) {
                    mutex_exit(&l->hl_lock);
                    return EBUSY;
          }

          /* stop removing hooks */
          l->hl_state = HKLIST_INUSE;
          l->hl_lwp = curlwp;

          LIST_FOREACH(hd, &l->hl_list, hk_list) {
                    if (hd->hk_fn == NULL)
                              continue;

                    fn = hd->hk_fn;
                    arg = hd->hk_arg;
                    l->hl_active_hk = hd;
                    l->hl_cvlock = NULL;

                    mutex_exit(&l->hl_lock);

                    /* do callback without l->hl_lock */
                    (*fn)(arg);

                    mutex_enter(&l->hl_lock);
                    l->hl_active_hk = NULL;
                    cv_lock = l->hl_cvlock;

                    if (hd->hk_fn == NULL) {
                              if (cv_lock != NULL) {
                                        mutex_exit(&l->hl_lock);
                                        mutex_enter(cv_lock);
                              }

                              cv_broadcast(&l->hl_cv);

                              if (cv_lock != NULL) {
                                        mutex_exit(cv_lock);
                                        mutex_enter(&l->hl_lock);
                              }
                    }
          }

          /* remove marked node while running hooks */
          LIST_FOREACH_SAFE(hd, &l->hl_list, hk_list, nexthd) {
                    if (hd->hk_fn == NULL) {
                              LIST_REMOVE(hd, hk_list);
                              kmem_free(hd, sizeof(*hd));
                    }
          }

          l->hl_lwp = NULL;
          l->hl_state = HKLIST_IDLE;
          mutex_exit(&l->hl_lock);

          return 0;
}

khook_t *
simplehook_establish(khook_list_t *l, void (*fn)(void *), void *arg)
{
          struct hook_desc *hd;

          hd = kmem_zalloc(sizeof(*hd), KM_SLEEP);
          hd->hk_fn = fn;
          hd->hk_arg = arg;

          mutex_enter(&l->hl_lock);
          LIST_INSERT_HEAD(&l->hl_list, hd, hk_list);
          mutex_exit(&l->hl_lock);

          return hd;
}

void
simplehook_disestablish(khook_list_t *l, khook_t *hd, kmutex_t *lock)
{
          struct hook_desc *hd0 __diagused;
          kmutex_t *cv_lock;

          KASSERT(lock == NULL || mutex_owned(lock));
          mutex_enter(&l->hl_lock);

#ifdef DIAGNOSTIC
          LIST_FOREACH(hd0, &l->hl_list, hk_list) {
                    if (hd == hd0)
                              break;
          }

          if (hd0 == NULL)
                    panic("hook_disestablish: hook %p not established", hd);
#endif

          /* The hook is not referred, remove immediately */
          if (l->hl_state == HKLIST_IDLE) {
                    LIST_REMOVE(hd, hk_list);
                    kmem_free(hd, sizeof(*hd));
                    mutex_exit(&l->hl_lock);
                    return;
          }

          /* remove callback. hd will be removed in dohooks */
          hd->hk_fn = NULL;
          hd->hk_arg = NULL;

          /* If the hook is running, wait for the completion */
          if (l->hl_active_hk == hd &&
              l->hl_lwp != curlwp) {
                    if (lock != NULL) {
                              cv_lock = lock;
                              KASSERT(l->hl_cvlock == NULL);
                              l->hl_cvlock = lock;
                              mutex_exit(&l->hl_lock);
                    } else {
                              cv_lock = &l->hl_lock;
                    }

                    cv_wait(&l->hl_cv, cv_lock);

                    if (lock == NULL)
                              mutex_exit(&l->hl_lock);
          } else {
                    mutex_exit(&l->hl_lock);
          }
}

bool
simplehook_has_hooks(khook_list_t *l)
{
          bool empty;

          mutex_enter(&l->hl_lock);
          empty = LIST_EMPTY(&l->hl_list);
          mutex_exit(&l->hl_lock);

          return !empty;
}