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 "private/KernelArgumentBlock.h"
32 #include "private/bionic_arc4random.h"
33 #include "private/bionic_auxv.h"
34 #include "private/bionic_globals.h"
35 #include "private/bionic_ssp.h"
36 #include "pthread_internal.h"
37
38 extern "C" int __set_tls(void* ptr);
39 extern "C" int __set_tid_address(int* tid_address);
40
41 // Declared in "private/bionic_ssp.h".
42 uintptr_t __stack_chk_guard = 0;
43
__libc_init_global_stack_chk_guard(KernelArgumentBlock & args)44 void __libc_init_global_stack_chk_guard(KernelArgumentBlock& args) {
45 __libc_safe_arc4random_buf(&__stack_chk_guard, sizeof(__stack_chk_guard), args);
46 }
47
48 // Setup for the main thread. For dynamic executables, this is called by the
49 // linker _before_ libc is mapped in memory. This means that all writes to
50 // globals from this function will apply to linker-private copies and will not
51 // be visible from libc later on.
52 //
53 // Note: this function creates a pthread_internal_t for the initial thread and
54 // stores the pointer in TLS, but does not add it to pthread's thread list. This
55 // has to be done later from libc itself (see __libc_init_common).
56 //
57 // This is in a file by itself because it needs to be built with
58 // -fno-stack-protector because it's responsible for setting up the main
59 // thread's TLS (which stack protector relies on).
60
__libc_init_main_thread(KernelArgumentBlock & args)61 void __libc_init_main_thread(KernelArgumentBlock& args) {
62 __libc_auxv = args.auxv;
63 #if defined(__i386__)
64 __libc_init_sysinfo(args);
65 #endif
66
67 static pthread_internal_t main_thread;
68
69 // The -fstack-protector implementation uses TLS, so make sure that's
70 // set up before we call any function that might get a stack check inserted.
71 // TLS also needs to be set up before errno (and therefore syscalls) can be used.
72 __set_tls(main_thread.tls);
73 if (!__init_tls(&main_thread)) async_safe_fatal("failed to initialize TLS: %s", strerror(errno));
74
75 // Tell the kernel to clear our tid field when we exit, so we're like any other pthread.
76 // As a side-effect, this tells us our pid (which is the same as the main thread's tid).
77 main_thread.tid = __set_tid_address(&main_thread.tid);
78 main_thread.set_cached_pid(main_thread.tid);
79
80 // We don't want to free the main thread's stack even when the main thread exits
81 // because things like environment variables with global scope live on it.
82 // We also can't free the pthread_internal_t itself, since that lives on the main
83 // thread's stack rather than on the heap.
84 // The main thread has no mmap allocated space for stack or pthread_internal_t.
85 main_thread.mmap_size = 0;
86 pthread_attr_init(&main_thread.attr);
87 main_thread.attr.guard_size = 0; // The main thread has no guard page.
88 main_thread.attr.stack_size = 0; // User code should never see this; we'll compute it when asked.
89 // TODO: the main thread's sched_policy and sched_priority need to be queried.
90
91 // The TLS stack guard is set from the global, so ensure that we've initialized the global
92 // before we initialize the TLS. Dynamic executables will initialize their copy of the global
93 // stack protector from the one in the main thread's TLS.
94 __libc_init_global_stack_chk_guard(args);
95 __init_thread_stack_guard(&main_thread);
96
97 __init_thread(&main_thread);
98
99 // Store a pointer to the kernel argument block in a TLS slot to be
100 // picked up by the libc constructor.
101 main_thread.tls[TLS_SLOT_BIONIC_PREINIT] = &args;
102
103 __init_alternate_signal_stack(&main_thread);
104 }
105