fs.c revision 9685194fc94510a33201aee9b80c23f206ccfe67 
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#include <cutils/fs.h>
18#include <cutils/log.h>
19
20#include <sys/types.h>
21#include <sys/stat.h>
22#include <fcntl.h>
23#include <unistd.h>
24#include <errno.h>
25#include <string.h>
26#include <limits.h>
27
28#define ALL_PERMS (S_ISUID | S_ISGID | S_ISVTX | S_IRWXU | S_IRWXG | S_IRWXO)
29#define BUF_SIZE 64
30
31int fs_prepare_dir(const char* path, mode_t mode, uid_t uid, gid_t gid) {
32    // Check if path needs to be created
33    struct stat sb;
34    if (lstat(path, &sb) == -1) {
35        if (errno == ENOENT) {
36            goto create;
37        } else {
38            ALOGE("Failed to stat(%s): %s", path, strerror(errno));
39            return -1;
40        }
41    }
42
43    // Exists, verify status
44    if (!S_ISDIR(sb.st_mode)) {
45        ALOGE("Not a directory: %s", path);
46        return -1;
47    }
48    if (((sb.st_mode & ALL_PERMS) == mode) && (sb.st_uid == uid) && (sb.st_gid == gid)) {
49        return 0;
50    } else {
51        goto fixup;
52    }
53
54create:
55    if (mkdir(path, mode) == -1) {
56        ALOGE("Failed to mkdir(%s): %s", path, strerror(errno));
57        return -1;
58    }
59
60fixup:
61    if (chmod(path, mode) == -1) {
62        ALOGE("Failed to chown(%s, %d): %s", path, mode, strerror(errno));
63        return -1;
64    }
65    if (chown(path, uid, gid) == -1) {
66        ALOGE("Failed to chown(%s, %d, %d): %s", path, uid, gid, strerror(errno));
67        return -1;
68    }
69
70    return 0;
71}
72
73int fs_read_atomic_int(const char* path, int* out_value) {
74    int fd = open(path, O_RDONLY);
75    if (fd == -1) {
76        ALOGE("Failed to read %s: %s", path, strerror(errno));
77        return -1;
78    }
79
80    char buf[BUF_SIZE];
81    if (read(fd, buf, BUF_SIZE) == -1) {
82        ALOGE("Failed to read %s: %s", path, strerror(errno));
83        goto fail;
84    }
85    if (sscanf(buf, "%d", out_value) != 1) {
86        ALOGE("Failed to parse %s: %s", path, strerror(errno));
87        goto fail;
88    }
89    close(fd);
90    return 0;
91
92fail:
93    close(fd);
94    *out_value = -1;
95    return -1;
96}
97
98int fs_write_atomic_int(const char* path, int value) {
99    char temp[PATH_MAX];
100    if (snprintf(temp, PATH_MAX, "%s.XXXXXX", path) >= PATH_MAX) {
101        ALOGE("Path too long");
102        return -1;
103    }
104
105    int fd = mkstemp(temp);
106    if (fd == -1) {
107        ALOGE("Failed to open %s: %s", temp, strerror(errno));
108        return -1;
109    }
110
111    char buf[BUF_SIZE];
112    int len = snprintf(buf, BUF_SIZE, "%d", value) + 1;
113    if (len > BUF_SIZE) {
114        ALOGE("Value %d too large: %s", value, strerror(errno));
115        goto fail;
116    }
117    if (write(fd, buf, len) < len) {
118        ALOGE("Failed to write %s: %s", temp, strerror(errno));
119        goto fail;
120    }
121    if (close(fd) == -1) {
122        ALOGE("Failed to close %s: %s", temp, strerror(errno));
123        goto fail_closed;
124    }
125
126    if (rename(temp, path) == -1) {
127        ALOGE("Failed to rename %s to %s: %s", temp, path, strerror(errno));
128        goto fail_closed;
129    }
130
131    return 0;
132
133fail:
134    close(fd);
135fail_closed:
136    unlink(temp);
137    return -1;
138}
139