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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 "libc_init_common.h"
     30 
     31 #include <elf.h>
     32 #include <errno.h>
     33 #include <stddef.h>
     34 #include <stdint.h>
     35 #include <stdio.h>
     36 #include <stdlib.h>
     37 #include <sys/auxv.h>
     38 #include <sys/time.h>
     39 #include <unistd.h>
     40 
     41 #include "private/bionic_auxv.h"
     42 #include "private/bionic_ssp.h"
     43 #include "private/bionic_tls.h"
     44 #include "private/KernelArgumentBlock.h"
     45 #include "pthread_internal.h"
     46 
     47 extern "C" abort_msg_t** __abort_message_ptr;
     48 extern "C" int __system_properties_init(void);
     49 extern "C" int __set_tls(void* ptr);
     50 extern "C" int __set_tid_address(int* tid_address);
     51 
     52 void __libc_init_vdso();
     53 
     54 // Not public, but well-known in the BSDs.
     55 const char* __progname;
     56 
     57 // Declared in <unistd.h>.
     58 char** environ;
     59 
     60 // Declared in "private/bionic_ssp.h".
     61 uintptr_t __stack_chk_guard = 0;
     62 
     63 /* Init TLS for the initial thread. Called by the linker _before_ libc is mapped
     64  * in memory. Beware: all writes to libc globals from this function will
     65  * apply to linker-private copies and will not be visible from libc later on.
     66  *
     67  * Note: this function creates a pthread_internal_t for the initial thread and
     68  * stores the pointer in TLS, but does not add it to pthread's thread list. This
     69  * has to be done later from libc itself (see __libc_init_common).
     70  *
     71  * This function also stores a pointer to the kernel argument block in a TLS slot to be
     72  * picked up by the libc constructor.
     73  */
     74 void __libc_init_tls(KernelArgumentBlock& args) {
     75   __libc_auxv = args.auxv;
     76 
     77   static void* tls[BIONIC_TLS_SLOTS];
     78   static pthread_internal_t main_thread;
     79   main_thread.tls = tls;
     80 
     81   // Tell the kernel to clear our tid field when we exit, so we're like any other pthread.
     82   // As a side-effect, this tells us our pid (which is the same as the main thread's tid).
     83   main_thread.tid = __set_tid_address(&main_thread.tid);
     84   main_thread.set_cached_pid(main_thread.tid);
     85 
     86   // We don't want to free the main thread's stack even when the main thread exits
     87   // because things like environment variables with global scope live on it.
     88   // We also can't free the pthread_internal_t itself, since that lives on the main
     89   // thread's stack rather than on the heap.
     90   pthread_attr_init(&main_thread.attr);
     91   main_thread.attr.flags = PTHREAD_ATTR_FLAG_USER_ALLOCATED_STACK | PTHREAD_ATTR_FLAG_MAIN_THREAD;
     92   main_thread.attr.guard_size = 0; // The main thread has no guard page.
     93   main_thread.attr.stack_size = 0; // User code should never see this; we'll compute it when asked.
     94   // TODO: the main thread's sched_policy and sched_priority need to be queried.
     95 
     96   __init_thread(&main_thread, false);
     97   __init_tls(&main_thread);
     98   __set_tls(main_thread.tls);
     99   tls[TLS_SLOT_BIONIC_PREINIT] = &args;
    100 
    101   __init_alternate_signal_stack(&main_thread);
    102 }
    103 
    104 void __libc_init_common(KernelArgumentBlock& args) {
    105   // Initialize various globals.
    106   environ = args.envp;
    107   errno = 0;
    108   __libc_auxv = args.auxv;
    109   __progname = args.argv[0] ? args.argv[0] : "<unknown>";
    110   __abort_message_ptr = args.abort_message_ptr;
    111 
    112   // AT_RANDOM is a pointer to 16 bytes of randomness on the stack.
    113   __stack_chk_guard = *reinterpret_cast<uintptr_t*>(getauxval(AT_RANDOM));
    114 
    115   // Get the main thread from TLS and add it to the thread list.
    116   pthread_internal_t* main_thread = __get_thread();
    117   _pthread_internal_add(main_thread);
    118 
    119   __system_properties_init(); // Requires 'environ'.
    120 
    121   __libc_init_vdso();
    122 }
    123 
    124 /* This function will be called during normal program termination
    125  * to run the destructors that are listed in the .fini_array section
    126  * of the executable, if any.
    127  *
    128  * 'fini_array' points to a list of function addresses. The first
    129  * entry in the list has value -1, the last one has value 0.
    130  */
    131 void __libc_fini(void* array) {
    132   void** fini_array = reinterpret_cast<void**>(array);
    133   const size_t minus1 = ~(size_t)0; /* ensure proper sign extension */
    134 
    135   /* Sanity check - first entry must be -1 */
    136   if (array == NULL || (size_t)fini_array[0] != minus1) {
    137     return;
    138   }
    139 
    140   /* skip over it */
    141   fini_array += 1;
    142 
    143   /* Count the number of destructors. */
    144   int count = 0;
    145   while (fini_array[count] != NULL) {
    146     ++count;
    147   }
    148 
    149   /* Now call each destructor in reverse order. */
    150   while (count > 0) {
    151     void (*func)() = (void (*)()) fini_array[--count];
    152 
    153     /* Sanity check, any -1 in the list is ignored */
    154     if ((size_t)func == minus1) {
    155       continue;
    156     }
    157 
    158     func();
    159   }
    160 
    161 #ifndef LIBC_STATIC
    162   {
    163     extern void __libc_postfini(void) __attribute__((weak));
    164     if (__libc_postfini) {
    165       __libc_postfini();
    166     }
    167   }
    168 #endif
    169 }
    170