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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  */
__libc_init_tls(KernelArgumentBlock & args)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 
__libc_init_common(KernelArgumentBlock & args)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  */
__libc_fini(void * array)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