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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 
     29 /*
     30  * This file is only used to provide backwards compatibility to property areas
     31  * created by old versions of init, which occurs when an ota runs.  The updater
     32  * binary is compiled statically against the newest bionic, but the recovery
     33  * ramdisk may be using an old version of init.  This can all be removed once
     34  * OTAs from pre-K versions are no longer supported.
     35  */
     36 
     37 #include <string.h>
     38 
     39 #include "private/bionic_futex.h"
     40 
     41 #define _REALLY_INCLUDE_SYS__SYSTEM_PROPERTIES_H_
     42 #include <sys/_system_properties.h>
     43 
     44 #define TOC_NAME_LEN(toc)       ((toc) >> 24)
     45 #define TOC_TO_INFO(area, toc)  ((prop_info_compat*) (((char*) area) + ((toc) & 0xFFFFFF)))
     46 
     47 struct prop_area_compat {
     48     unsigned volatile count;
     49     unsigned volatile serial;
     50     unsigned magic;
     51     unsigned version;
     52     unsigned reserved[4];
     53     unsigned toc[1];
     54 };
     55 
     56 typedef struct prop_area_compat prop_area_compat;
     57 
     58 struct prop_area;
     59 typedef struct prop_area prop_area;
     60 
     61 struct prop_info_compat {
     62     char name[PROP_NAME_MAX];
     63     unsigned volatile serial;
     64     char value[PROP_VALUE_MAX];
     65 };
     66 
     67 typedef struct prop_info_compat prop_info_compat;
     68 
     69 extern prop_area *__system_property_area__;
     70 
     71 __LIBC_HIDDEN__ const prop_info *__system_property_find_compat(const char *name)
     72 {
     73     prop_area_compat *pa = (prop_area_compat *)__system_property_area__;
     74     unsigned count = pa->count;
     75     unsigned *toc = pa->toc;
     76     unsigned len = strlen(name);
     77     prop_info_compat *pi;
     78 
     79     if (len >= PROP_NAME_MAX)
     80         return 0;
     81     if (len < 1)
     82         return 0;
     83 
     84     while(count--) {
     85         unsigned entry = *toc++;
     86         if(TOC_NAME_LEN(entry) != len) continue;
     87 
     88         pi = TOC_TO_INFO(pa, entry);
     89         if(memcmp(name, pi->name, len)) continue;
     90 
     91         return (const prop_info *)pi;
     92     }
     93 
     94     return 0;
     95 }
     96 
     97 __LIBC_HIDDEN__ int __system_property_read_compat(const prop_info *_pi, char *name, char *value)
     98 {
     99     unsigned serial, len;
    100     const prop_info_compat *pi = (const prop_info_compat *)_pi;
    101 
    102     for(;;) {
    103         serial = pi->serial;
    104         while(SERIAL_DIRTY(serial)) {
    105             __futex_wait((volatile void *)&pi->serial, serial, NULL);
    106             serial = pi->serial;
    107         }
    108         len = SERIAL_VALUE_LEN(serial);
    109         memcpy(value, pi->value, len + 1);
    110         if(serial == pi->serial) {
    111             if(name != 0) {
    112                 strcpy(name, pi->name);
    113             }
    114             return len;
    115         }
    116     }
    117 }
    118 
    119 __LIBC_HIDDEN__ int __system_property_foreach_compat(
    120         void (*propfn)(const prop_info *pi, void *cookie),
    121         void *cookie)
    122 {
    123     prop_area_compat *pa = (prop_area_compat *)__system_property_area__;
    124     unsigned i;
    125 
    126     for (i = 0; i < pa->count; i++) {
    127         unsigned entry = pa->toc[i];
    128         prop_info_compat *pi = TOC_TO_INFO(pa, entry);
    129         propfn((const prop_info *)pi, cookie);
    130     }
    131 
    132     return 0;
    133 }
    134