fs.c revision 6de702679089fab13ec2d4d435054f68688df545 
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
30#define ALL_PERMS (S_ISUID | S_ISGID | S_ISVTX | S_IRWXU | S_IRWXG | S_IRWXO)
31#define BUF_SIZE 64
32
33int fs_prepare_dir(const char* path, mode_t mode, uid_t uid, gid_t gid) {
34    // Check if path needs to be created
35    struct stat sb;
36    if (TEMP_FAILURE_RETRY(lstat(path, &sb)) == -1) {
37        if (errno == ENOENT) {
38            goto create;
39        } else {
40            ALOGE("Failed to lstat(%s): %s", path, strerror(errno));
41            return -1;
42        }
43    }
44
45    // Exists, verify status
46    if (!S_ISDIR(sb.st_mode)) {
47        ALOGE("Not a directory: %s", path);
48        return -1;
49    }
50    if (((sb.st_mode & ALL_PERMS) == mode) && (sb.st_uid == uid) && (sb.st_gid == gid)) {
51        return 0;
52    } else {
53        goto fixup;
54    }
55
56create:
57    if (TEMP_FAILURE_RETRY(mkdir(path, mode)) == -1) {
58        ALOGE("Failed to mkdir(%s): %s", path, strerror(errno));
59        return -1;
60    }
61
62fixup:
63    if (TEMP_FAILURE_RETRY(chmod(path, mode)) == -1) {
64        ALOGE("Failed to chmod(%s, %d): %s", path, mode, strerror(errno));
65        return -1;
66    }
67    if (TEMP_FAILURE_RETRY(chown(path, uid, gid)) == -1) {
68        ALOGE("Failed to chown(%s, %d, %d): %s", path, uid, gid, strerror(errno));
69        return -1;
70    }
71
72    return 0;
73}
74
75int fs_read_atomic_int(const char* path, int* out_value) {
76    int fd = TEMP_FAILURE_RETRY(open(path, O_RDONLY));
77    if (fd == -1) {
78        ALOGE("Failed to read %s: %s", path, strerror(errno));
79        return -1;
80    }
81
82    char buf[BUF_SIZE];
83    if (TEMP_FAILURE_RETRY(read(fd, buf, BUF_SIZE)) == -1) {
84        ALOGE("Failed to read %s: %s", path, strerror(errno));
85        goto fail;
86    }
87    if (sscanf(buf, "%d", out_value) != 1) {
88        ALOGE("Failed to parse %s: %s", path, strerror(errno));
89        goto fail;
90    }
91    close(fd);
92    return 0;
93
94fail:
95    close(fd);
96    *out_value = -1;
97    return -1;
98}
99
100int fs_write_atomic_int(const char* path, int value) {
101    char temp[PATH_MAX];
102    if (snprintf(temp, PATH_MAX, "%s.XXXXXX", path) >= PATH_MAX) {
103        ALOGE("Path too long");
104        return -1;
105    }
106
107    int fd = TEMP_FAILURE_RETRY(mkstemp(temp));
108    if (fd == -1) {
109        ALOGE("Failed to open %s: %s", temp, strerror(errno));
110        return -1;
111    }
112
113    char buf[BUF_SIZE];
114    int len = snprintf(buf, BUF_SIZE, "%d", value) + 1;
115    if (len > BUF_SIZE) {
116        ALOGE("Value %d too large: %s", value, strerror(errno));
117        goto fail;
118    }
119    if (TEMP_FAILURE_RETRY(write(fd, buf, len)) < len) {
120        ALOGE("Failed to write %s: %s", temp, strerror(errno));
121        goto fail;
122    }
123    if (close(fd) == -1) {
124        ALOGE("Failed to close %s: %s", temp, strerror(errno));
125        goto fail_closed;
126    }
127
128    if (rename(temp, path) == -1) {
129        ALOGE("Failed to rename %s to %s: %s", temp, path, strerror(errno));
130        goto fail_closed;
131    }
132
133    return 0;
134
135fail:
136    close(fd);
137fail_closed:
138    unlink(temp);
139    return -1;
140}
141