sysfs.c revision 331769 
1/*
2 * Copyright (c) 2006 Cisco Systems, Inc.  All rights reserved.
3 *
4 * This software is available to you under a choice of one of two
5 * licenses.  You may choose to be licensed under the terms of the GNU
6 * General Public License (GPL) Version 2, available from the file
7 * COPYING in the main directory of this source tree, or the
8 * OpenIB.org BSD license below:
9 *
10 *     Redistribution and use in source and binary forms, with or
11 *     without modification, are permitted provided that the following
12 *     conditions are met:
13 *
14 *      - Redistributions of source code must retain the above
15 *        copyright notice, this list of conditions and the following
16 *        disclaimer.
17 *
18 *      - Redistributions in binary form must reproduce the above
19 *        copyright notice, this list of conditions and the following
20 *        disclaimer in the documentation and/or other materials
21 *        provided with the distribution.
22 *
23 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
24 * EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
25 * MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
26 * NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS
27 * BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN
28 * ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN
29 * CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
30 * SOFTWARE.
31 */
32#define _GNU_SOURCE
33#include <config.h>
34
35#include <stdio.h>
36#include <stdlib.h>
37#include <unistd.h>
38#include <sys/types.h>
39#include <sys/stat.h>
40#include <fcntl.h>
41#include <string.h>
42#include <sys/sysctl.h>
43
44#include "ibverbs.h"
45
46static const char *sysfs_path;
47
48const char *ibv_get_sysfs_path(void)
49{
50	const char *env = NULL;
51
52	if (sysfs_path)
53		return sysfs_path;
54
55	/*
56	 * Only follow use path passed in through the calling user's
57	 * environment if we're not running SUID.
58	 */
59	if (getuid() == geteuid())
60		env = getenv("SYSFS_PATH");
61
62	if (env) {
63		int len;
64		char *dup;
65
66		sysfs_path = dup = strndup(env, IBV_SYSFS_PATH_MAX);
67		len = strlen(dup);
68		while (len > 0 && dup[len - 1] == '/') {
69			--len;
70			dup[len] = '\0';
71		}
72	} else
73		sysfs_path = "/sys";
74
75	return sysfs_path;
76}
77
78int ibv_read_sysfs_file(const char *dir, const char *file,
79			char *buf, size_t size)
80{
81	char *path, *s;
82	int fd;
83	size_t len;
84
85	if (asprintf(&path, "%s/%s", dir, file) < 0)
86		return -1;
87
88	for (s = &path[0]; *s != '\0'; s++)
89		if (*s == '/')
90			*s = '.';
91
92        len = size;
93        if (sysctlbyname(&path[1], buf, &len, NULL, 0) == -1)
94		return -1;
95
96	free(path);
97
98	if (len > 0 && buf[len - 1] == '\n')
99		buf[--len] = '\0';
100
101	return len;
102}
103