kvm_pcpu.c revision 181876 
1/*-
2 * Copyright (c) 2008 Yahoo!, Inc.
3 * All rights reserved.
4 * Written by: John Baldwin <jhb@FreeBSD.org>
5 *
6 * Redistribution and use in source and binary forms, with or without
7 * modification, are permitted provided that the following conditions
8 * are met:
9 * 1. Redistributions of source code must retain the above copyright
10 *    notice, this list of conditions and the following disclaimer.
11 * 2. Redistributions in binary form must reproduce the above copyright
12 *    notice, this list of conditions and the following disclaimer in the
13 *    documentation and/or other materials provided with the distribution.
14 * 3. Neither the name of the author nor the names of any co-contributors
15 *    may be used to endorse or promote products derived from this software
16 *    without specific prior written permission.
17 *
18 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
19 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
20 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
21 * ARE DISCLAIMED.  IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
22 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
23 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
24 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
25 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
26 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
27 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
28 * SUCH DAMAGE.
29 */
30
31#include <sys/cdefs.h>
32__FBSDID("$FreeBSD: head/lib/libkvm/kvm_pcpu.c 181876 2008-08-19 19:55:33Z jhb $");
33
34#include <sys/param.h>
35#include <sys/pcpu.h>
36#include <sys/sysctl.h>
37#include <kvm.h>
38#include <limits.h>
39#include <stdlib.h>
40
41#include "kvm_private.h"
42
43static struct nlist kvm_pcpu_nl[] = {
44	{ "_cpuid_to_pcpu" },
45	{ "_mp_maxcpus" },
46	{ NULL },
47};
48
49/*
50 * Kernel per-CPU data state.  We cache this stuff on the first
51 * access.
52 */
53static void **pcpu_data;
54static int maxcpu;
55
56#define	NL_CPUID_TO_PCPU	0
57#define	NL_MP_MAXCPUS		1
58
59static int
60_kvm_pcpu_init(kvm_t *kd)
61{
62	size_t len;
63	int max;
64	void *data;
65
66	if (kvm_nlist(kd, kvm_pcpu_nl) < 0)
67		return (-1);
68	if (kvm_pcpu_nl[NL_CPUID_TO_PCPU].n_value == 0) {
69		_kvm_err(kd, kd->program, "unable to find cpuid_to_pcpu");
70		return (-1);
71	}
72	if (kvm_pcpu_nl[NL_MP_MAXCPUS].n_value == 0) {
73		_kvm_err(kd, kd->program, "unable to find mp_maxcpus");
74		return (-1);
75	}
76	if (kvm_read(kd, kvm_pcpu_nl[NL_MP_MAXCPUS].n_value, &max,
77	    sizeof(max)) != sizeof(max)) {
78		_kvm_err(kd, kd->program, "cannot read mp_maxcpus");
79		return (-1);
80	}
81	len = max * sizeof(void *);
82	data = malloc(len);
83	if (data == NULL) {
84		_kvm_err(kd, kd->program, "out of memory");
85		return (-1);
86	}
87	if (kvm_read(kd, kvm_pcpu_nl[NL_CPUID_TO_PCPU].n_value, data, len) !=
88	    len) {
89		_kvm_err(kd, kd->program, "cannot read cpuid_to_pcpu array");
90		free(data);
91		return (-1);
92	}
93	pcpu_data = data;
94	maxcpu = max;
95	return (0);
96}
97
98static void
99_kvm_pcpu_clear(void)
100{
101
102	maxcpu = 0;
103	free(pcpu_data);
104	pcpu_data = NULL;
105}
106
107void *
108kvm_getpcpu(kvm_t *kd, int cpu)
109{
110	char *buf;
111	int i;
112
113	if (kd == NULL) {
114		_kvm_pcpu_clear();
115		return (NULL);
116	}
117
118	if (maxcpu == 0)
119		if (_kvm_pcpu_init(kd) < 0)
120			return ((void *)-1);
121
122	if (cpu >= maxcpu || pcpu_data[cpu] == NULL)
123		return (NULL);
124
125	buf = malloc(sizeof(struct pcpu));
126	if (buf == NULL) {
127		_kvm_err(kd, kd->program, "out of memory");
128		return ((void *)-1);
129	}
130	if (kvm_read(kd, (uintptr_t)pcpu_data[cpu], buf, sizeof(struct pcpu)) !=
131	    sizeof(struct pcpu)) {
132		_kvm_err(kd, kd->program, "unable to read per-CPU data");
133		free(buf);
134		return ((void *)-1);
135	}
136	return (buf);
137}
138
139int
140kvm_getmaxcpu(kvm_t *kd)
141{
142
143	if (kd == NULL) {
144		_kvm_pcpu_clear();
145		return (0);
146	}
147
148	if (maxcpu == 0)
149		if (_kvm_pcpu_init(kd) < 0)
150			return (-1);
151	return (maxcpu);
152}
153