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 <async_safe/log.h>
32
33 #include "private/KernelArgumentBlock.h"
34 #include "private/bionic_arc4random.h"
35 #include "private/bionic_defs.h"
36 #include "private/bionic_elf_tls.h"
37 #include "private/bionic_globals.h"
38 #include "private/bionic_ssp.h"
39 #include "pthread_internal.h"
40
41 extern "C" pid_t __getpid();
42 extern "C" int __set_tid_address(int* tid_address);
43
44 // Declared in "private/bionic_ssp.h".
45 uintptr_t __stack_chk_guard = 0;
46
47 static pthread_internal_t main_thread;
48
49 // Setup for the main thread. For dynamic executables, this is called by the
50 // linker _before_ libc is mapped in memory. This means that all writes to
51 // globals from this function will apply to linker-private copies and will not
52 // be visible from libc later on.
53 //
54 // Note: this function creates a pthread_internal_t for the initial thread and
55 // stores the pointer in TLS, but does not add it to pthread's thread list. This
56 // has to be done later from libc itself (see __libc_init_common).
57 //
58 // This is in a file by itself because it needs to be built with
59 // -fno-stack-protector because it's responsible for setting up the main
60 // thread's TLS (which stack protector relies on).
61
62 // Do enough setup to:
63 // - Let the dynamic linker invoke system calls (and access errno)
64 // - Ensure that TLS access functions (__get_{tls,thread}) never return NULL
65 // - Allow the stack protector to work (with a zero cookie)
66 // Avoid doing much more because, when this code is called within the dynamic
67 // linker, the linker binary hasn't been relocated yet, so certain kinds of code
68 // are hazardous, such as accessing non-hidden global variables.
69 __BIONIC_WEAK_FOR_NATIVE_BRIDGE
__libc_init_main_thread_early(const KernelArgumentBlock & args,bionic_tcb * temp_tcb)70 extern "C" void __libc_init_main_thread_early(const KernelArgumentBlock& args,
71 bionic_tcb* temp_tcb) {
72 __libc_shared_globals()->auxv = args.auxv;
73 #if defined(__i386__)
74 __libc_init_sysinfo(); // uses AT_SYSINFO auxv entry
75 #endif
76 __init_tcb(temp_tcb, &main_thread);
77 __init_tcb_dtv(temp_tcb);
78 __set_tls(&temp_tcb->tls_slot(0));
79 main_thread.tid = __getpid();
80 main_thread.set_cached_pid(main_thread.tid);
81 }
82
83 // Finish initializing the main thread.
84 __BIONIC_WEAK_FOR_NATIVE_BRIDGE
__libc_init_main_thread_late()85 extern "C" void __libc_init_main_thread_late() {
86 __init_bionic_tls_ptrs(__get_bionic_tcb(), __allocate_temp_bionic_tls());
87
88 // Tell the kernel to clear our tid field when we exit, so we're like any other pthread.
89 // For threads created by pthread_create, this setup happens during the clone syscall (i.e.
90 // CLONE_CHILD_CLEARTID).
91 __set_tid_address(&main_thread.tid);
92
93 pthread_attr_init(&main_thread.attr);
94 // We don't want to explicitly set the main thread's scheduler attributes (http://b/68328561).
95 pthread_attr_setinheritsched(&main_thread.attr, PTHREAD_INHERIT_SCHED);
96 // The main thread has no guard page.
97 pthread_attr_setguardsize(&main_thread.attr, 0);
98 // User code should never see this; we'll compute it when asked.
99 pthread_attr_setstacksize(&main_thread.attr, 0);
100
101 // The TLS stack guard is set from the global, so ensure that we've initialized the global
102 // before we initialize the TLS. Dynamic executables will initialize their copy of the global
103 // stack protector from the one in the main thread's TLS.
104 __libc_safe_arc4random_buf(&__stack_chk_guard, sizeof(__stack_chk_guard));
105 __init_tcb_stack_guard(__get_bionic_tcb());
106
107 __init_thread(&main_thread);
108
109 __init_additional_stacks(&main_thread);
110 }
111
112 // Once all ELF modules are loaded, allocate the final copy of the main thread's
113 // static TLS memory.
114 __BIONIC_WEAK_FOR_NATIVE_BRIDGE
__libc_init_main_thread_final()115 extern "C" void __libc_init_main_thread_final() {
116 bionic_tcb* temp_tcb = __get_bionic_tcb();
117 bionic_tls* temp_tls = &__get_bionic_tls();
118
119 // Allocate the main thread's static TLS. (This mapping doesn't include a
120 // stack.)
121 ThreadMapping mapping = __allocate_thread_mapping(0, PTHREAD_GUARD_SIZE);
122 if (mapping.mmap_base == nullptr) {
123 async_safe_fatal("failed to mmap main thread static TLS: %s", strerror(errno));
124 }
125
126 const StaticTlsLayout& layout = __libc_shared_globals()->static_tls_layout;
127 auto new_tcb = reinterpret_cast<bionic_tcb*>(mapping.static_tls + layout.offset_bionic_tcb());
128 auto new_tls = reinterpret_cast<bionic_tls*>(mapping.static_tls + layout.offset_bionic_tls());
129
130 __init_static_tls(mapping.static_tls);
131 new_tcb->copy_from_bootstrap(temp_tcb);
132 new_tls->copy_from_bootstrap(temp_tls);
133 __init_tcb(new_tcb, &main_thread);
134 __init_bionic_tls_ptrs(new_tcb, new_tls);
135
136 main_thread.mmap_base = mapping.mmap_base;
137 main_thread.mmap_size = mapping.mmap_size;
138
139 __set_tls(&new_tcb->tls_slot(0));
140
141 __free_temp_bionic_tls(temp_tls);
142 }
143