1 /*
2 * Copyright (C) 2019 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 "linker_tls.h"
30
31 #include <vector>
32
33 #include "async_safe/CHECK.h"
34 #include "linker_globals.h"
35 #include "linker_main.h"
36 #include "linker_soinfo.h"
37 #include "private/ScopedRWLock.h"
38 #include "private/ScopedSignalBlocker.h"
39 #include "private/bionic_defs.h"
40 #include "private/bionic_elf_tls.h"
41 #include "private/bionic_globals.h"
42 #include "private/linker_native_bridge.h"
43
44 static bool g_static_tls_finished;
45 static std::vector<TlsModule> g_tls_modules;
46
get_unused_module_index()47 static size_t get_unused_module_index() {
48 for (size_t i = 0; i < g_tls_modules.size(); ++i) {
49 if (g_tls_modules[i].soinfo_ptr == nullptr) {
50 return i;
51 }
52 }
53 g_tls_modules.push_back({});
54 __libc_shared_globals()->tls_modules.module_count = g_tls_modules.size();
55 __libc_shared_globals()->tls_modules.module_table = g_tls_modules.data();
56 return g_tls_modules.size() - 1;
57 }
58
register_tls_module(soinfo * si,size_t static_offset)59 static void register_tls_module(soinfo* si, size_t static_offset) {
60 TlsModules& libc_modules = __libc_shared_globals()->tls_modules;
61
62 // The global TLS module table points at the std::vector of modules declared
63 // in this file, so acquire a write lock before modifying the std::vector.
64 ScopedSignalBlocker ssb;
65 ScopedWriteLock locker(&libc_modules.rwlock);
66
67 size_t module_idx = get_unused_module_index();
68
69 soinfo_tls* si_tls = si->get_tls();
70 si_tls->module_id = __tls_module_idx_to_id(module_idx);
71
72 const size_t new_generation = ++libc_modules.generation;
73 __libc_tls_generation_copy = new_generation;
74 if (libc_modules.generation_libc_so != nullptr) {
75 *libc_modules.generation_libc_so = new_generation;
76 }
77
78 g_tls_modules[module_idx] = {
79 .segment = si_tls->segment,
80 .static_offset = static_offset,
81 .first_generation = new_generation,
82 .soinfo_ptr = si,
83 };
84 }
85
unregister_tls_module(soinfo * si)86 static void unregister_tls_module(soinfo* si) {
87 ScopedSignalBlocker ssb;
88 ScopedWriteLock locker(&__libc_shared_globals()->tls_modules.rwlock);
89
90 soinfo_tls* si_tls = si->get_tls();
91 TlsModule& mod = g_tls_modules[__tls_module_id_to_idx(si_tls->module_id)];
92 CHECK(mod.static_offset == SIZE_MAX);
93 CHECK(mod.soinfo_ptr == si);
94 mod = {};
95 si_tls->module_id = kTlsUninitializedModuleId;
96 }
97
98 // The reference is valid until a TLS module is registered or unregistered.
get_tls_module(size_t module_id)99 const TlsModule& get_tls_module(size_t module_id) {
100 size_t module_idx = __tls_module_id_to_idx(module_id);
101 CHECK(module_idx < g_tls_modules.size());
102 return g_tls_modules[module_idx];
103 }
104
105 __BIONIC_WEAK_FOR_NATIVE_BRIDGE
__linker_reserve_bionic_tls_in_static_tls()106 extern "C" void __linker_reserve_bionic_tls_in_static_tls() {
107 __libc_shared_globals()->static_tls_layout.reserve_bionic_tls();
108 }
109
linker_setup_exe_static_tls(const char * progname)110 void linker_setup_exe_static_tls(const char* progname) {
111 soinfo* somain = solist_get_somain();
112 StaticTlsLayout& layout = __libc_shared_globals()->static_tls_layout;
113
114 // For ldd, don't add the executable's TLS segment to the static TLS layout.
115 // It is likely to trigger the underaligned TLS segment error on arm32/arm64
116 // when the ldd argument is actually a shared object.
117 if (somain->get_tls() == nullptr || g_is_ldd) {
118 layout.reserve_exe_segment_and_tcb(nullptr, progname);
119 } else {
120 register_tls_module(somain, layout.reserve_exe_segment_and_tcb(&somain->get_tls()->segment, progname));
121 }
122
123 // The pthread key data is located at the very front of bionic_tls. As a
124 // temporary workaround, allocate bionic_tls just after the thread pointer so
125 // Golang can find its pthread key, as long as the executable's TLS segment is
126 // small enough. Specifically, Golang scans forward 384 words from the TP on
127 // ARM.
128 // - http://b/118381796
129 // - https://github.com/golang/go/issues/29674
130 __linker_reserve_bionic_tls_in_static_tls();
131 }
132
linker_finalize_static_tls()133 void linker_finalize_static_tls() {
134 g_static_tls_finished = true;
135 __libc_shared_globals()->static_tls_layout.finish_layout();
136 TlsModules& modules = __libc_shared_globals()->tls_modules;
137 modules.static_module_count = modules.module_count;
138 }
139
register_soinfo_tls(soinfo * si)140 void register_soinfo_tls(soinfo* si) {
141 // ldd skips registration of the executable's TLS segment above to avoid the
142 // arm32/arm64 underalignment error. For consistency, also skip registration
143 // of TLS segments here, for shared objects.
144 if (g_is_ldd) return;
145
146 soinfo_tls* si_tls = si->get_tls();
147 if (si_tls == nullptr || si_tls->module_id != kTlsUninitializedModuleId) {
148 return;
149 }
150 size_t static_offset = SIZE_MAX;
151 if (!g_static_tls_finished) {
152 StaticTlsLayout& layout = __libc_shared_globals()->static_tls_layout;
153 static_offset = layout.reserve_solib_segment(si_tls->segment);
154 }
155 register_tls_module(si, static_offset);
156 }
157
unregister_soinfo_tls(soinfo * si)158 void unregister_soinfo_tls(soinfo* si) {
159 soinfo_tls* si_tls = si->get_tls();
160 if (si_tls == nullptr || si_tls->module_id == kTlsUninitializedModuleId) {
161 return;
162 }
163 return unregister_tls_module(si);
164 }
165