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
53struct nmi_handler {
54	int (*n_func)(const struct trapframe *, void *);
55	void *n_arg;
56	struct nmi_handler *n_next;
57};
58
59static kmutex_t nmi_list_lock; /* serialize establish and disestablish */
60static pserialize_t nmi_psz;
61static 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
70nmi_handler_t *
71nmi_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
98void
99nmi_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
141int
142nmi_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
164void
165nmi_init(void)
166{
167
168	mutex_init(&nmi_list_lock, MUTEX_DEFAULT, IPL_NONE);
169	nmi_psz = pserialize_create();
170}
171