ddb_capture.c revision 330449 
1/*-
2 * SPDX-License-Identifier: BSD-2-Clause-FreeBSD
3 *
4 * Copyright (c) 2008 Robert N. M. Watson
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__FBSDID("$FreeBSD: stable/11/sbin/ddb/ddb_capture.c 330449 2018-03-05 07:26:05Z eadler $");
31
32#include <sys/types.h>
33#include <sys/sysctl.h>
34
35#include <err.h>
36#include <errno.h>
37#include <fcntl.h>
38#include <kvm.h>
39#include <limits.h>
40#include <stdio.h>
41#include <stdlib.h>
42#include <string.h>
43#include <sysexits.h>
44#include <unistd.h>
45
46#include "ddb.h"
47
48/*
49 * Interface with the ddb(4) capture buffer of a live kernel using sysctl, or
50 * for a crash dump using libkvm.
51 */
52#define	SYSCTL_DDB_CAPTURE_BUFOFF	"debug.ddb.capture.bufoff"
53#define	SYSCTL_DDB_CAPTURE_BUFSIZE	"debug.ddb.capture.bufsize"
54#define	SYSCTL_DDB_CAPTURE_MAXBUFSIZE	"debug.ddb.capture.maxbufsize"
55#define	SYSCTL_DDB_CAPTURE_DATA		"debug.ddb.capture.data"
56#define	SYSCTL_DDB_CAPTURE_INPROGRESS	"debug.ddb.capture.inprogress"
57
58static struct nlist namelist[] = {
59#define X_DB_CAPTURE_BUF	0
60	{ .n_name = "_db_capture_buf" },
61#define X_DB_CAPTURE_BUFSIZE	1
62	{ .n_name = "_db_capture_bufsize" },
63#define X_DB_CAPTURE_MAXBUFSIZE	2
64	{ .n_name = "_db_capture_maxbufsize" },
65#define X_DB_CAPTURE_BUFOFF	3
66	{ .n_name = "_db_capture_bufoff" },
67#define	X_DB_CAPTURE_INPROGRESS	4
68	{ .n_name = "_db_capture_inprogress" },
69	{ .n_name = "" },
70};
71
72static int
73kread(kvm_t *kvm, void *kvm_pointer, void *address, size_t size,
74    size_t offset)
75{
76	ssize_t ret;
77
78	ret = kvm_read(kvm, (unsigned long)kvm_pointer + offset, address,
79	    size);
80	if (ret < 0 || (size_t)ret != size)
81		return (-1);
82	return (0);
83}
84
85static int
86kread_symbol(kvm_t *kvm, int index, void *address, size_t size,
87    size_t offset)
88{
89	ssize_t ret;
90
91	ret = kvm_read(kvm, namelist[index].n_value + offset, address, size);
92	if (ret < 0 || (size_t)ret != size)
93		return (-1);
94	return (0);
95}
96
97static void
98ddb_capture_print_kvm(kvm_t *kvm)
99{
100	u_int db_capture_bufoff;
101	char *buffer, *db_capture_buf;
102
103	if (kread_symbol(kvm, X_DB_CAPTURE_BUF, &db_capture_buf,
104	    sizeof(db_capture_buf), 0) < 0)
105		errx(-1, "kvm: unable to read db_capture_buf");
106
107	if (kread_symbol(kvm, X_DB_CAPTURE_BUFOFF, &db_capture_bufoff,
108	    sizeof(db_capture_bufoff), 0) < 0)
109		errx(-1, "kvm: unable to read db_capture_bufoff");
110
111	buffer = malloc(db_capture_bufoff + 1);
112	if (buffer == NULL)
113		err(-1, "malloc: db_capture_bufoff (%u)",
114		    db_capture_bufoff);
115	bzero(buffer, db_capture_bufoff + 1);
116
117	if (kread(kvm, db_capture_buf, buffer, db_capture_bufoff, 0) < 0)
118		errx(-1, "kvm: unable to read buffer");
119
120	printf("%s\n", buffer);
121	free(buffer);
122}
123
124static void
125ddb_capture_print_sysctl(void)
126{
127	size_t buflen, len;
128	char *buffer;
129	int ret;
130
131repeat:
132	if (sysctlbyname(SYSCTL_DDB_CAPTURE_DATA, NULL, &buflen, NULL, 0) < 0)
133		err(EX_OSERR, "sysctl: %s", SYSCTL_DDB_CAPTURE_DATA);
134	if (buflen == 0)
135		return;
136	buffer = malloc(buflen);
137	if (buffer == NULL)
138		err(EX_OSERR, "malloc");
139	bzero(buffer, buflen);
140	len = buflen;
141	ret = sysctlbyname(SYSCTL_DDB_CAPTURE_DATA, buffer, &len, NULL, 0);
142	if (ret < 0 && errno != ENOMEM)
143		err(EX_OSERR, "sysctl: %s", SYSCTL_DDB_CAPTURE_DATA);
144	if (ret < 0) {
145		free(buffer);
146		goto repeat;
147	}
148
149	printf("%s\n", buffer);
150	free(buffer);
151}
152
153static void
154ddb_capture_status_kvm(kvm_t *kvm)
155{
156	u_int db_capture_bufoff, db_capture_bufsize, db_capture_inprogress;
157
158	if (kread_symbol(kvm, X_DB_CAPTURE_BUFOFF, &db_capture_bufoff,
159	    sizeof(db_capture_bufoff), 0) < 0)
160		errx(-1, "kvm: unable to read db_capture_bufoff");
161	if (kread_symbol(kvm, X_DB_CAPTURE_BUFSIZE, &db_capture_bufsize,
162	    sizeof(db_capture_bufsize), 0) < 0)
163		errx(-1, "kvm: unable to read db_capture_bufsize");
164	if (kread_symbol(kvm, X_DB_CAPTURE_INPROGRESS,
165	    &db_capture_inprogress, sizeof(db_capture_inprogress), 0) < 0)
166		err(-1, "kvm: unable to read db_capture_inprogress");
167	printf("%u/%u bytes used\n", db_capture_bufoff, db_capture_bufsize);
168	if (db_capture_inprogress)
169		printf("capture is on\n");
170	else
171		printf("capture is off\n");
172
173}
174
175static void
176ddb_capture_status_sysctl(void)
177{
178	u_int db_capture_bufoff, db_capture_bufsize, db_capture_inprogress;
179	size_t len;
180
181	len = sizeof(db_capture_bufoff);
182	if (sysctlbyname(SYSCTL_DDB_CAPTURE_BUFOFF, &db_capture_bufoff, &len,
183	    NULL, 0) < 0)
184		err(EX_OSERR, "sysctl: %s", SYSCTL_DDB_CAPTURE_BUFOFF);
185	len = sizeof(db_capture_bufoff);
186	if (sysctlbyname(SYSCTL_DDB_CAPTURE_BUFSIZE, &db_capture_bufsize,
187	    &len, NULL, 0) < 0)
188		err(EX_OSERR, "sysctl: %s", SYSCTL_DDB_CAPTURE_BUFSIZE);
189	len = sizeof(db_capture_inprogress);
190	if (sysctlbyname(SYSCTL_DDB_CAPTURE_INPROGRESS,
191	    &db_capture_inprogress, &len, NULL, 0) < 0)
192		err(EX_OSERR, "sysctl: %s", SYSCTL_DDB_CAPTURE_INPROGRESS);
193	printf("%u/%u bytes used\n", db_capture_bufoff, db_capture_bufsize);
194	if (db_capture_inprogress)
195		printf("capture is on\n");
196	else
197		printf("capture is off\n");
198}
199
200void
201ddb_capture(int argc, char *argv[])
202{
203	char *mflag, *nflag, errbuf[_POSIX2_LINE_MAX];
204	kvm_t *kvm;
205	int ch;
206
207	mflag = NULL;
208	nflag = NULL;
209	kvm = NULL;
210	while ((ch = getopt(argc, argv, "M:N:")) != -1) {
211		switch (ch) {
212		case 'M':
213			mflag = optarg;
214			break;
215
216		case 'N':
217			nflag = optarg;
218			break;
219
220		default:
221			usage();
222		}
223	}
224	argc -= optind;
225	argv += optind;
226
227	if (argc != 1)
228		usage();
229
230	if (mflag != NULL) {
231		kvm = kvm_openfiles(nflag, mflag, NULL, O_RDONLY, errbuf);
232		if (kvm == NULL)
233			errx(-1, "ddb_capture: kvm_openfiles: %s", errbuf);
234		if (kvm_nlist(kvm, namelist) != 0)
235			errx(-1, "ddb_capture: kvm_nlist");
236	} else if (nflag != NULL)
237		usage();
238	if (strcmp(argv[0], "print") == 0) {
239		if (kvm != NULL)
240			ddb_capture_print_kvm(kvm);
241		else
242			ddb_capture_print_sysctl();
243	} else if (strcmp(argv[0], "status") == 0) {
244		if (kvm != NULL)
245			ddb_capture_status_kvm(kvm);
246		else
247			ddb_capture_status_sysctl();
248	} else
249		usage();
250}
251