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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 #include <android/api-level.h>
     30 #include <elf.h>
     31 #include <errno.h>
     32 #include <stddef.h>
     33 #include <stdint.h>
     34 #include <stdio.h>
     35 #include <stdlib.h>
     36 #include <sys/auxv.h>
     37 #include <sys/mman.h>
     38 
     39 #include "libc_init_common.h"
     40 #include "pthread_internal.h"
     41 
     42 #include "private/bionic_globals.h"
     43 #include "private/bionic_macros.h"
     44 #include "private/bionic_page.h"
     45 #include "private/bionic_tls.h"
     46 #include "private/KernelArgumentBlock.h"
     47 
     48 extern "C" int __cxa_atexit(void (*)(void *), void *, void *);
     49 
     50 static void call_array(void(**list)()) {
     51   // First element is -1, list is null-terminated
     52   while (*++list) {
     53     (*list)();
     54   }
     55 }
     56 
     57 static void apply_gnu_relro() {
     58   ElfW(Phdr)* phdr_start = reinterpret_cast<ElfW(Phdr)*>(getauxval(AT_PHDR));
     59   unsigned long int phdr_ct = getauxval(AT_PHNUM);
     60 
     61   for (ElfW(Phdr)* phdr = phdr_start; phdr < (phdr_start + phdr_ct); phdr++) {
     62     if (phdr->p_type != PT_GNU_RELRO) {
     63       continue;
     64     }
     65 
     66     ElfW(Addr) seg_page_start = PAGE_START(phdr->p_vaddr);
     67     ElfW(Addr) seg_page_end = PAGE_END(phdr->p_vaddr + phdr->p_memsz);
     68 
     69     // Check return value here? What do we do if we fail?
     70     mprotect(reinterpret_cast<void*>(seg_page_start), seg_page_end - seg_page_start, PROT_READ);
     71   }
     72 }
     73 
     74 // The program startup function __libc_init() defined here is
     75 // used for static executables only (i.e. those that don't depend
     76 // on shared libraries). It is called from arch-$ARCH/bionic/crtbegin_static.S
     77 // which is directly invoked by the kernel when the program is launched.
     78 //
     79 // The 'structors' parameter contains pointers to various initializer
     80 // arrays that must be run before the program's 'main' routine is launched.
     81 
     82 __noreturn void __libc_init(void* raw_args,
     83                             void (*onexit)(void) __unused,
     84                             int (*slingshot)(int, char**, char**),
     85                             structors_array_t const * const structors) {
     86   BIONIC_STOP_UNWIND;
     87 
     88   KernelArgumentBlock args(raw_args);
     89   __libc_init_main_thread(args);
     90 
     91   // Initializing the globals requires TLS to be available for errno.
     92   __init_thread_stack_guard(__get_thread());
     93   __libc_init_globals(args);
     94 
     95   __libc_init_AT_SECURE(args);
     96   __libc_init_common(args);
     97 
     98   apply_gnu_relro();
     99 
    100   // Several Linux ABIs don't pass the onexit pointer, and the ones that
    101   // do never use it.  Therefore, we ignore it.
    102 
    103   call_array(structors->preinit_array);
    104   call_array(structors->init_array);
    105 
    106   // The executable may have its own destructors listed in its .fini_array
    107   // so we need to ensure that these are called when the program exits
    108   // normally.
    109   if (structors->fini_array != NULL) {
    110     __cxa_atexit(__libc_fini,structors->fini_array,NULL);
    111   }
    112 
    113   exit(slingshot(args.argc, args.argv, args.envp));
    114 }
    115 
    116 uint32_t bionic_get_application_target_sdk_version() {
    117   return __ANDROID_API__;
    118 }
    119