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      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 
     49 static const char property_service_socket[] = "/dev/socket/" PROP_SERVICE_NAME;
     50 
     51 static unsigned dummy_props = 0;
     52 
     53 prop_area *__system_property_area__ = (void*) &dummy_props;
     54 
     55 int __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 
     92 const 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 
    103 const 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 
    124 int __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 
    145 int __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 
    158 static 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 
    218 int __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 
    243 int __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