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      1 /*
      2  * Copyright (C) 2016 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 typedef struct
     30 {
     31     void (**preinit_array)(void);
     32     void (**init_array)(void);
     33     void (**fini_array)(void);
     34     void (**ctor_list)(void);
     35 } structors_array_t;
     36 
     37 extern int main(int argc, char **argv, char **env);
     38 
     39 extern void __libc_init(
     40   unsigned int *elfdata,
     41   void (*onexit)(void),
     42   int (*slingshot)(int, char**, char**),
     43   structors_array_t const * const structors
     44 );
     45 
     46 __attribute__ ((section (".preinit_array")))
     47 void (*__PREINIT_ARRAY__)(void) = (void (*)(void)) -1;
     48 
     49 __attribute__ ((section (".init_array")))
     50 void (*__INIT_ARRAY__)(void) = (void (*)(void)) -1;
     51 
     52 __attribute__ ((section (".fini_array")))
     53 void (*__FINI_ARRAY__)(void) = (void (*)(void)) -1;
     54 
     55 __attribute__ ((section (".ctors")))
     56 void (*__CTOR_LIST__)(void) = (void (*)(void)) -1;
     57 
     58 /*
     59  * This is the small startup code that is first run when any executable runs.
     60  *
     61  * Its purpose is to call __libc_init with appropriate arguments, which are:
     62  *
     63  * - The address of the raw data block setup by the Linux kernel ELF loader.
     64  *
     65  * - The address of an "onexit" function, not used on any platform supported by
     66  *   Bionic.
     67  *
     68  * - The address of the "main" function of the program.
     69  *
     70  * - The address of the constructor list.
     71  */
     72 __attribute__((visibility("hidden")))
     73 void _start() {
     74   structors_array_t array;
     75   void *elfdata;
     76 
     77   array.preinit_array = &__PREINIT_ARRAY__;
     78   array.init_array =    &__INIT_ARRAY__;
     79   array.fini_array =    &__FINI_ARRAY__;
     80   array.ctor_list =    &__CTOR_LIST__;
     81 
     82   elfdata = __builtin_frame_address(0) + sizeof(void *);
     83   __libc_init(elfdata, (void *) 0, &main, &array);
     84 }
     85 
     86 #include "__dso_handle.h"
     87 #include "atexit.h"
     88