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      1 /*	$Id: nmi.c,v 1.6 2022/05/15 12:45:33 riastradh Exp $	*/
      2 
      3 /*-
      4  * Copyright (c)2009,2011 YAMAMOTO Takashi,
      5  * All rights reserved.
      6  *
      7  * Redistribution and use in source and binary forms, with or without
      8  * modification, are permitted provided that the following conditions
      9  * are met:
     10  * 1. Redistributions of source code must retain the above copyright
     11  *    notice, this list of conditions and the following disclaimer.
     12  * 2. Redistributions in binary form must reproduce the above copyright
     13  *    notice, this list of conditions and the following disclaimer in the
     14  *    documentation and/or other materials provided with the distribution.
     15  *
     16  * THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
     17  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
     18  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
     19  * ARE DISCLAIMED.  IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
     20  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
     21  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
     22  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
     23  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
     24  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
     25  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
     26  * SUCH DAMAGE.
     27  */
     28 
     29 #include <sys/cdefs.h>
     30 __KERNEL_RCSID(0, "$NetBSD: nmi.c,v 1.6 2022/05/15 12:45:33 riastradh Exp $");
     31 
     32 /*
     33  * nmi dispatcher.
     34  *
     35  * XXX no need to be nmi-specific.
     36  * actual assumptions are:
     37  *	- dispatch() is called with preemption disabled.
     38  *	- handlers never block.
     39  *	- establish() and disestablish() are called within a thread context.
     40  *	  (thus can block)
     41  */
     42 
     43 #include <sys/param.h>
     44 #include <sys/kernel.h>
     45 #include <sys/systm.h>
     46 #include <sys/atomic.h>
     47 #include <sys/kmem.h>
     48 #include <sys/mutex.h>
     49 #include <sys/pserialize.h>
     50 
     51 #include <x86/nmi.h>
     52 
     53 struct nmi_handler {
     54 	int (*n_func)(const struct trapframe *, void *);
     55 	void *n_arg;
     56 	struct nmi_handler *n_next;
     57 };
     58 
     59 static kmutex_t nmi_list_lock; /* serialize establish and disestablish */
     60 static pserialize_t nmi_psz;
     61 static nmi_handler_t *nmi_handlers; /* list of handlers */
     62 
     63 /*
     64  * nmi_establish: establish an nmi handler
     65  *
     66  * => can block.
     67  * => returns an opaque handle.
     68  */
     69 
     70 nmi_handler_t *
     71 nmi_establish(int (*func)(const struct trapframe *, void *), void *arg)
     72 {
     73 	struct nmi_handler *n;
     74 
     75 	n = kmem_alloc(sizeof(*n), KM_SLEEP);
     76 	n->n_func = func;
     77 	n->n_arg = arg;
     78 
     79 	/*
     80 	 * put it into the list.
     81 	 */
     82 
     83 	mutex_enter(&nmi_list_lock);
     84 	n->n_next = nmi_handlers;
     85 	atomic_store_release(&nmi_handlers, n);
     86 	mutex_exit(&nmi_list_lock);
     87 
     88 	return n;
     89 }
     90 
     91 /*
     92  * nmi_disestablish: disestablish an nmi handler.
     93  *
     94  * => can block.
     95  * => take an opaque handle.  it must be one returned by nmi_establish.
     96  */
     97 
     98 void
     99 nmi_disestablish(nmi_handler_t *handle)
    100 {
    101 	nmi_handler_t *n;
    102 	nmi_handler_t **pp;
    103 
    104 	KASSERT(handle != NULL);
    105 
    106 	/*
    107 	 * remove the handler from the list.
    108 	 */
    109 
    110 	mutex_enter(&nmi_list_lock);
    111 	for (pp = &nmi_handlers, n = *pp; n != NULL; n = *pp) {
    112 		if (n == handle) {
    113 			break;
    114 		}
    115 		pp = &n->n_next;
    116 	}
    117 #if defined(DIAGNOSTIC)
    118 	if (n == NULL) {
    119 		mutex_exit(&nmi_list_lock);
    120 		panic("%s: invalid handle %p", __func__, handle);
    121 	}
    122 #endif /* defined(DIAGNOSTIC) */
    123 	atomic_store_relaxed(pp, n->n_next);
    124 	mutex_exit(&nmi_list_lock); /* mutex_exit implies a store fence */
    125 
    126 	/*
    127 	 * before freeing 'n', ensure that no other cpus are
    128 	 * in the middle of nmi_dispatch.
    129 	 */
    130 
    131 	pserialize_perform(nmi_psz);
    132 	kmem_free(n, sizeof(*n));
    133 }
    134 
    135 /*
    136  * nmi_dispatch: dispatch an nmi.
    137  *
    138  * => called by interrupts, thus preempt disabled.
    139  */
    140 
    141 int
    142 nmi_dispatch(const struct trapframe *tf)
    143 {
    144 	const struct nmi_handler *n;
    145 	int handled = 0;
    146 
    147 	/*
    148 	 * XXX abstraction violation
    149 	 *
    150 	 * we don't bother to call pserialize_read_enter/pserialize_read_exit
    151 	 * because they are not necessary here as we are sure our IPL is
    152 	 * higher than IPL_SOFTSERIAL.  better to avoid unnecessary calls as
    153 	 * we are in a dangerous context. (NMI)
    154 	 */
    155 
    156 	for (n = atomic_load_consume(&nmi_handlers);
    157 	     n != NULL;
    158 	     n = atomic_load_relaxed(&n->n_next)) {
    159 		handled |= (*n->n_func)(tf, n->n_arg);
    160 	}
    161 	return handled;
    162 }
    163 
    164 void
    165 nmi_init(void)
    166 {
    167 
    168 	mutex_init(&nmi_list_lock, MUTEX_DEFAULT, IPL_NONE);
    169 	nmi_psz = pserialize_create();
    170 }
    171