1/*
2 * Copyright (C) 2008 The Android Open Source Project
3 * All rights reserved.
4 *
5 * Redistribution and use in source and binary forms, with or without
6 * modification, are permitted provided that the following conditions
7 * are met:
8 *  * Redistributions of source code must retain the above copyright
9 *    notice, this list of conditions and the following disclaimer.
10 *  * Redistributions in binary form must reproduce the above copyright
11 *    notice, this list of conditions and the following disclaimer in
12 *    the documentation and/or other materials provided with the
13 *    distribution.
14 *
15 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
16 * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
17 * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
18 * FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
19 * COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
20 * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING,
21 * BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS
22 * OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED
23 * AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
24 * OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT
25 * OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
26 * SUCH DAMAGE.
27 */
28#include <stdio.h>
29#include <stdlib.h>
30#include <unistd.h>
31#include <stddef.h>
32#include <errno.h>
33#include <poll.h>
34
35#include <sys/mman.h>
36
37#include <sys/socket.h>
38#include <sys/un.h>
39#include <sys/select.h>
40#include <sys/types.h>
41#include <netinet/in.h>
42#include <unistd.h>
43
44#define _REALLY_INCLUDE_SYS__SYSTEM_PROPERTIES_H_
45#include <sys/_system_properties.h>
46
47#include <sys/atomics.h>
48
49static const char property_service_socket[] = "/dev/socket/" PROP_SERVICE_NAME;
50
51static unsigned dummy_props = 0;
52
53prop_area *__system_property_area__ = (void*) &dummy_props;
54
55int __system_properties_init(void)
56{
57    prop_area *pa;
58    int s, fd;
59    unsigned sz;
60    char *env;
61
62    if(__system_property_area__ != ((void*) &dummy_props)) {
63        return 0;
64    }
65
66    env = getenv("ANDROID_PROPERTY_WORKSPACE");
67    if (!env) {
68        return -1;
69    }
70    fd = atoi(env);
71    env = strchr(env, ',');
72    if (!env) {
73        return -1;
74    }
75    sz = atoi(env + 1);
76
77    pa = mmap(0, sz, PROT_READ, MAP_SHARED, fd, 0);
78
79    if(pa == MAP_FAILED) {
80        return -1;
81    }
82
83    if((pa->magic != PROP_AREA_MAGIC) || (pa->version != PROP_AREA_VERSION)) {
84        munmap(pa, sz);
85        return -1;
86    }
87
88    __system_property_area__ = pa;
89    return 0;
90}
91
92const prop_info *__system_property_find_nth(unsigned n)
93{
94    prop_area *pa = __system_property_area__;
95
96    if(n >= pa->count) {
97        return 0;
98    } else {
99        return TOC_TO_INFO(pa, pa->toc[n]);
100    }
101}
102
103const prop_info *__system_property_find(const char *name)
104{
105    prop_area *pa = __system_property_area__;
106    unsigned count = pa->count;
107    unsigned *toc = pa->toc;
108    unsigned len = strlen(name);
109    prop_info *pi;
110
111    while(count--) {
112        unsigned entry = *toc++;
113        if(TOC_NAME_LEN(entry) != len) continue;
114
115        pi = TOC_TO_INFO(pa, entry);
116        if(memcmp(name, pi->name, len)) continue;
117
118        return pi;
119    }
120
121    return 0;
122}
123
124int __system_property_read(const prop_info *pi, char *name, char *value)
125{
126    unsigned serial, len;
127
128    for(;;) {
129        serial = pi->serial;
130        while(SERIAL_DIRTY(serial)) {
131            __futex_wait((volatile void *)&pi->serial, serial, 0);
132            serial = pi->serial;
133        }
134        len = SERIAL_VALUE_LEN(serial);
135        memcpy(value, pi->value, len + 1);
136        if(serial == pi->serial) {
137            if(name != 0) {
138                strcpy(name, pi->name);
139            }
140            return len;
141        }
142    }
143}
144
145int __system_property_get(const char *name, char *value)
146{
147    const prop_info *pi = __system_property_find(name);
148
149    if(pi != 0) {
150        return __system_property_read(pi, 0, value);
151    } else {
152        value[0] = 0;
153        return 0;
154    }
155}
156
157
158static int send_prop_msg(prop_msg *msg)
159{
160    struct pollfd pollfds[1];
161    struct sockaddr_un addr;
162    socklen_t alen;
163    size_t namelen;
164    int s;
165    int r;
166    int result = -1;
167
168    s = socket(AF_LOCAL, SOCK_STREAM, 0);
169    if(s < 0) {
170        return result;
171    }
172
173    memset(&addr, 0, sizeof(addr));
174    namelen = strlen(property_service_socket);
175    strlcpy(addr.sun_path, property_service_socket, sizeof addr.sun_path);
176    addr.sun_family = AF_LOCAL;
177    alen = namelen + offsetof(struct sockaddr_un, sun_path) + 1;
178
179    if(TEMP_FAILURE_RETRY(connect(s, (struct sockaddr *) &addr, alen) < 0)) {
180        close(s);
181        return result;
182    }
183
184    r = TEMP_FAILURE_RETRY(send(s, msg, sizeof(prop_msg), 0));
185
186    if(r == sizeof(prop_msg)) {
187        // We successfully wrote to the property server but now we
188        // wait for the property server to finish its work.  It
189        // acknowledges its completion by closing the socket so we
190        // poll here (on nothing), waiting for the socket to close.
191        // If you 'adb shell setprop foo bar' you'll see the POLLHUP
192        // once the socket closes.  Out of paranoia we cap our poll
193        // at 250 ms.
194        pollfds[0].fd = s;
195        pollfds[0].events = 0;
196        r = TEMP_FAILURE_RETRY(poll(pollfds, 1, 250 /* ms */));
197        if (r == 1 && (pollfds[0].revents & POLLHUP) != 0) {
198            result = 0;
199        } else {
200            // Ignore the timeout and treat it like a success anyway.
201            // The init process is single-threaded and its property
202            // service is sometimes slow to respond (perhaps it's off
203            // starting a child process or something) and thus this
204            // times out and the caller thinks it failed, even though
205            // it's still getting around to it.  So we fake it here,
206            // mostly for ctl.* properties, but we do try and wait 250
207            // ms so callers who do read-after-write can reliably see
208            // what they've written.  Most of the time.
209            // TODO: fix the system properties design.
210            result = 0;
211        }
212    }
213
214    close(s);
215    return result;
216}
217
218int __system_property_set(const char *key, const char *value)
219{
220    int err;
221    int tries = 0;
222    int update_seen = 0;
223    prop_msg msg;
224
225    if(key == 0) return -1;
226    if(value == 0) value = "";
227    if(strlen(key) >= PROP_NAME_MAX) return -1;
228    if(strlen(value) >= PROP_VALUE_MAX) return -1;
229
230    memset(&msg, 0, sizeof msg);
231    msg.cmd = PROP_MSG_SETPROP;
232    strlcpy(msg.name, key, sizeof msg.name);
233    strlcpy(msg.value, value, sizeof msg.value);
234
235    err = send_prop_msg(&msg);
236    if(err < 0) {
237        return err;
238    }
239
240    return 0;
241}
242
243int __system_property_wait(const prop_info *pi)
244{
245    unsigned n;
246    if(pi == 0) {
247        prop_area *pa = __system_property_area__;
248        n = pa->serial;
249        do {
250            __futex_wait(&pa->serial, n, 0);
251        } while(n == pa->serial);
252    } else {
253        n = pi->serial;
254        do {
255            __futex_wait((volatile void *)&pi->serial, n, 0);
256        } while(n == pi->serial);
257    }
258    return 0;
259}
260