fs.c revision 69ce489fc3946b7b89ca837a01d3828f1af2e0a0 
1/*
2 * Copyright (C) 2012 The Android Open Source Project
3 *
4 * Licensed under the Apache License, Version 2.0 (the "License");
5 * you may not use this file except in compliance with the License.
6 * You may obtain a copy of the License at
7 *
8 *      http://www.apache.org/licenses/LICENSE-2.0
9 *
10 * Unless required by applicable law or agreed to in writing, software
11 * distributed under the License is distributed on an "AS IS" BASIS,
12 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
13 * See the License for the specific language governing permissions and
14 * limitations under the License.
15 */
16
17#define LOG_TAG "cutils"
18
19#include <cutils/fs.h>
20#include <cutils/log.h>
21
22#include <sys/types.h>
23#include <sys/stat.h>
24#include <fcntl.h>
25#include <unistd.h>
26#include <errno.h>
27#include <string.h>
28#include <limits.h>
29#include <stdlib.h>
30
31#define ALL_PERMS (S_ISUID | S_ISGID | S_ISVTX | S_IRWXU | S_IRWXG | S_IRWXO)
32#define BUF_SIZE 64
33
34int fs_prepare_dir(const char* path, mode_t mode, uid_t uid, gid_t gid) {
35    // Check if path needs to be created
36    struct stat sb;
37    if (TEMP_FAILURE_RETRY(lstat(path, &sb)) == -1) {
38        if (errno == ENOENT) {
39            goto create;
40        } else {
41            ALOGE("Failed to lstat(%s): %s", path, strerror(errno));
42            return -1;
43        }
44    }
45
46    // Exists, verify status
47    if (!S_ISDIR(sb.st_mode)) {
48        ALOGE("Not a directory: %s", path);
49        return -1;
50    }
51    if (((sb.st_mode & ALL_PERMS) == mode) && (sb.st_uid == uid) && (sb.st_gid == gid)) {
52        return 0;
53    } else {
54        goto fixup;
55    }
56
57create:
58    if (TEMP_FAILURE_RETRY(mkdir(path, mode)) == -1) {
59        if (errno != EEXIST) {
60            ALOGE("Failed to mkdir(%s): %s", path, strerror(errno));
61            return -1;
62        }
63    }
64
65fixup:
66    if (TEMP_FAILURE_RETRY(chmod(path, mode)) == -1) {
67        ALOGE("Failed to chmod(%s, %d): %s", path, mode, strerror(errno));
68        return -1;
69    }
70    if (TEMP_FAILURE_RETRY(chown(path, uid, gid)) == -1) {
71        ALOGE("Failed to chown(%s, %d, %d): %s", path, uid, gid, strerror(errno));
72        return -1;
73    }
74
75    return 0;
76}
77
78int fs_read_atomic_int(const char* path, int* out_value) {
79    int fd = TEMP_FAILURE_RETRY(open(path, O_RDONLY));
80    if (fd == -1) {
81        ALOGE("Failed to read %s: %s", path, strerror(errno));
82        return -1;
83    }
84
85    char buf[BUF_SIZE];
86    if (TEMP_FAILURE_RETRY(read(fd, buf, BUF_SIZE)) == -1) {
87        ALOGE("Failed to read %s: %s", path, strerror(errno));
88        goto fail;
89    }
90    if (sscanf(buf, "%d", out_value) != 1) {
91        ALOGE("Failed to parse %s: %s", path, strerror(errno));
92        goto fail;
93    }
94    close(fd);
95    return 0;
96
97fail:
98    close(fd);
99    *out_value = -1;
100    return -1;
101}
102
103int fs_write_atomic_int(const char* path, int value) {
104    char temp[PATH_MAX];
105    if (snprintf(temp, PATH_MAX, "%s.XXXXXX", path) >= PATH_MAX) {
106        ALOGE("Path too long");
107        return -1;
108    }
109
110    int fd = TEMP_FAILURE_RETRY(mkstemp(temp));
111    if (fd == -1) {
112        ALOGE("Failed to open %s: %s", temp, strerror(errno));
113        return -1;
114    }
115
116    char buf[BUF_SIZE];
117    int len = snprintf(buf, BUF_SIZE, "%d", value) + 1;
118    if (len > BUF_SIZE) {
119        ALOGE("Value %d too large: %s", value, strerror(errno));
120        goto fail;
121    }
122    if (TEMP_FAILURE_RETRY(write(fd, buf, len)) < len) {
123        ALOGE("Failed to write %s: %s", temp, strerror(errno));
124        goto fail;
125    }
126    if (close(fd) == -1) {
127        ALOGE("Failed to close %s: %s", temp, strerror(errno));
128        goto fail_closed;
129    }
130
131    if (rename(temp, path) == -1) {
132        ALOGE("Failed to rename %s to %s: %s", temp, path, strerror(errno));
133        goto fail_closed;
134    }
135
136    return 0;
137
138fail:
139    close(fd);
140fail_closed:
141    unlink(temp);
142    return -1;
143}
144