xref: /freebsd/usr.bin/systat/fetch.c (revision 5e3190f700637fcfc1a52daeaa4a031fdd2557c7)
1 /*-
2  * SPDX-License-Identifier: BSD-3-Clause
3  *
4  * Copyright (c) 1980, 1992, 1993
5  *	The Regents of the University of California.  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  * 3. Neither the name of the University nor the names of its contributors
16  *    may be used to endorse or promote products derived from this software
17  *    without specific prior written permission.
18  *
19  * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
20  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
21  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
22  * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
23  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
24  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
25  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
26  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
27  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
28  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
29  * SUCH DAMAGE.
30  */
31 
32 
33 #ifdef lint
34 static const char sccsid[] = "@(#)fetch.c	8.1 (Berkeley) 6/6/93";
35 #endif
36 
37 #include <sys/types.h>
38 #include <sys/sysctl.h>
39 
40 #include <err.h>
41 #include <errno.h>
42 #include <stdlib.h>
43 #include <string.h>
44 
45 #include "systat.h"
46 #include "extern.h"
47 
48 int
49 kvm_ckread(void *a, void *b, int l)
50 {
51 	if (kvm_read(kd, (u_long)a, b, l) != l) {
52 		if (verbose)
53 			error("error reading kmem at %p", a);
54 		return (0);
55 	}
56 	else
57 		return (1);
58 }
59 
60 void
61 getsysctl(const char *name, void *ptr, size_t len)
62 {
63 	size_t nlen = len;
64 
65 	if (sysctlbyname(name, ptr, &nlen, NULL, 0) != 0) {
66 		error("sysctl(%s...) failed: %s", name,
67 		    strerror(errno));
68 	}
69 	if (nlen != len) {
70 		error("sysctl(%s...) expected %zu, got %zu", name, len, nlen);
71 	}
72 }
73 
74 /*
75  * Read sysctl data with variable size. Try some times (with increasing
76  * buffers), fail if still too small.
77  * This is needed sysctls with possibly raplidly increasing data sizes,
78  * but imposes little overhead in the case of constant sizes.
79  * Returns NULL on error, or a pointer to freshly malloc()'ed memory that holds
80  * the requested data.
81  * If szp is not NULL, the size of the returned data will be written into *szp.
82  */
83 
84 /* Some defines: Number of tries. */
85 #define SD_NTRIES  10
86 /* Percent of over-allocation (initial) */
87 #define SD_MARGIN  10
88 /*
89  * Factor for over-allocation in percent (the margin is increased by this on
90  * any failed try).
91  */
92 #define SD_FACTOR  50
93 /* Maximum supported MIB depth */
94 #define SD_MAXMIB  16
95 
96 char *
97 sysctl_dynread(const char *n, size_t *szp)
98 {
99 	char   *rv = NULL;
100 	int    mib[SD_MAXMIB];
101 	size_t mibsz = SD_MAXMIB;
102 	size_t mrg = SD_MARGIN;
103 	size_t sz;
104 	int i;
105 
106 	/* cache the MIB */
107 	if (sysctlnametomib(n, mib, &mibsz) == -1) {
108 		if (errno == ENOMEM) {
109 			error("XXX: SD_MAXMIB too small, please bump!");
110 		}
111 		return NULL;
112 	}
113 	for (i = 0; i < SD_NTRIES; i++) {
114 		/* get needed buffer size */
115 		if (sysctl(mib, mibsz, NULL, &sz, NULL, 0) == -1)
116 			break;
117 		sz += sz * mrg / 100;
118 		if ((rv = (char *)malloc(sz)) == NULL) {
119 			error("Out of memory!");
120 			return NULL;
121 		}
122 		if (sysctl(mib, mibsz, rv, &sz, NULL, 0) == -1) {
123 			free(rv);
124 			rv = NULL;
125 			if (errno == ENOMEM) {
126 				mrg += mrg * SD_FACTOR / 100;
127 			} else
128 				break;
129 		} else {
130 			/* success */
131 			if (szp != NULL)
132 				*szp = sz;
133 			break;
134 		}
135 	}
136 
137 	return rv;
138 }
139