16455b5100
Initialize a thread's DTV to an empty zeroed DTV. Allocate the DTV and any ELF module's TLS segment on-demand in __tls_get_addr. Use a generation counter, incremented in the linker, to signal when threads should update/reallocate their DTV objects. A generation count of 0 always indicates the constant zero DTV. Once a DTV is allocated, it isn't freed until the thread exits, because a signal handler could interrupt the fast path of __tls_get_addr between accessing the DTV slot and reading a field of the DTV. Bionic keeps a linked list of DTV objects so it can free them at thread-exit. Dynamic TLS memory is allocated using a BionicAllocator instance in libc_shared_globals. For async-signal safety, access to the linker/libc-shared state is protected by first blocking signals, then by acquiring the reader-writer lock, TlsModules::rwlock. A write lock is needed to allocate or free memory. In pthread_exit, unconditionally block signals before freeing dynamic TLS memory or freeing the shadow call stack. ndk_cruft.cpp: Avoid including pthread_internal.h inside an extern "C". (The header now includes a C++ template that doesn't compile inside extern "C".) Bug: http://b/78026329 Bug: http://b/123094171 Test: bionic unit tests Change-Id: I3c9b12921c9e68b33dcc1d1dd276bff364eff5d7
142 lines
5.9 KiB
C++
142 lines
5.9 KiB
C++
/*
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* Copyright (C) 2008 The Android Open Source Project
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* All rights reserved.
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*
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* Redistribution and use in source and binary forms, with or without
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* modification, are permitted provided that the following conditions
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* are met:
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* * Redistributions of source code must retain the above copyright
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* notice, this list of conditions and the following disclaimer.
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* * Redistributions in binary form must reproduce the above copyright
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* notice, this list of conditions and the following disclaimer in
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* the documentation and/or other materials provided with the
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* distribution.
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*
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* THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
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* "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
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* LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
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* FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
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* COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
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* INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING,
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* BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS
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* OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED
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* AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
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* OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT
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* OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
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* SUCH DAMAGE.
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*/
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#include "libc_init_common.h"
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#include <async_safe/log.h>
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#include "private/KernelArgumentBlock.h"
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#include "private/bionic_arc4random.h"
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#include "private/bionic_defs.h"
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#include "private/bionic_elf_tls.h"
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#include "private/bionic_globals.h"
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#include "private/bionic_ssp.h"
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#include "pthread_internal.h"
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extern "C" pid_t __getpid();
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extern "C" int __set_tid_address(int* tid_address);
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// Declared in "private/bionic_ssp.h".
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uintptr_t __stack_chk_guard = 0;
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static pthread_internal_t main_thread;
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// Setup for the main thread. For dynamic executables, this is called by the
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// linker _before_ libc is mapped in memory. This means that all writes to
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// globals from this function will apply to linker-private copies and will not
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// be visible from libc later on.
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//
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// Note: this function creates a pthread_internal_t for the initial thread and
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// stores the pointer in TLS, but does not add it to pthread's thread list. This
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// has to be done later from libc itself (see __libc_init_common).
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//
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// This is in a file by itself because it needs to be built with
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// -fno-stack-protector because it's responsible for setting up the main
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// thread's TLS (which stack protector relies on).
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// Do enough setup to:
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// - Let the dynamic linker invoke system calls (and access errno)
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// - Ensure that TLS access functions (__get_{tls,thread}) never return NULL
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// - Allow the stack protector to work (with a zero cookie)
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// Avoid doing much more because, when this code is called within the dynamic
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// linker, the linker binary hasn't been relocated yet, so certain kinds of code
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// are hazardous, such as accessing non-hidden global variables.
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__BIONIC_WEAK_FOR_NATIVE_BRIDGE
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extern "C" void __libc_init_main_thread_early(const KernelArgumentBlock& args,
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bionic_tcb* temp_tcb) {
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__libc_shared_globals()->auxv = args.auxv;
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#if defined(__i386__)
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__libc_init_sysinfo(); // uses AT_SYSINFO auxv entry
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#endif
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__init_tcb(temp_tcb, &main_thread);
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__init_tcb_dtv(temp_tcb);
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__set_tls(&temp_tcb->tls_slot(0));
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main_thread.tid = __getpid();
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main_thread.set_cached_pid(main_thread.tid);
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}
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// Finish initializing the main thread.
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__BIONIC_WEAK_FOR_NATIVE_BRIDGE
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extern "C" void __libc_init_main_thread_late() {
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__init_bionic_tls_ptrs(__get_bionic_tcb(), __allocate_temp_bionic_tls());
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// Tell the kernel to clear our tid field when we exit, so we're like any other pthread.
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// For threads created by pthread_create, this setup happens during the clone syscall (i.e.
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// CLONE_CHILD_CLEARTID).
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__set_tid_address(&main_thread.tid);
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pthread_attr_init(&main_thread.attr);
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// We don't want to explicitly set the main thread's scheduler attributes (http://b/68328561).
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pthread_attr_setinheritsched(&main_thread.attr, PTHREAD_INHERIT_SCHED);
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// The main thread has no guard page.
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pthread_attr_setguardsize(&main_thread.attr, 0);
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// User code should never see this; we'll compute it when asked.
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pthread_attr_setstacksize(&main_thread.attr, 0);
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// The TLS stack guard is set from the global, so ensure that we've initialized the global
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// before we initialize the TLS. Dynamic executables will initialize their copy of the global
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// stack protector from the one in the main thread's TLS.
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__libc_safe_arc4random_buf(&__stack_chk_guard, sizeof(__stack_chk_guard));
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__init_tcb_stack_guard(__get_bionic_tcb());
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__init_thread(&main_thread);
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__init_additional_stacks(&main_thread);
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}
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// Once all ELF modules are loaded, allocate the final copy of the main thread's
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// static TLS memory.
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__BIONIC_WEAK_FOR_NATIVE_BRIDGE
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extern "C" void __libc_init_main_thread_final() {
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bionic_tcb* temp_tcb = __get_bionic_tcb();
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bionic_tls* temp_tls = &__get_bionic_tls();
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// Allocate the main thread's static TLS. (This mapping doesn't include a
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// stack.)
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ThreadMapping mapping = __allocate_thread_mapping(0, PTHREAD_GUARD_SIZE);
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if (mapping.mmap_base == nullptr) {
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async_safe_fatal("failed to mmap main thread static TLS: %s", strerror(errno));
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}
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const StaticTlsLayout& layout = __libc_shared_globals()->static_tls_layout;
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auto new_tcb = reinterpret_cast<bionic_tcb*>(mapping.static_tls + layout.offset_bionic_tcb());
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auto new_tls = reinterpret_cast<bionic_tls*>(mapping.static_tls + layout.offset_bionic_tls());
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__init_static_tls(mapping.static_tls);
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new_tcb->copy_from_bootstrap(temp_tcb);
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new_tls->copy_from_bootstrap(temp_tls);
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__init_tcb(new_tcb, &main_thread);
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__init_bionic_tls_ptrs(new_tcb, new_tls);
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main_thread.mmap_base = mapping.mmap_base;
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main_thread.mmap_size = mapping.mmap_size;
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__set_tls(&new_tcb->tls_slot(0));
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__free_temp_bionic_tls(temp_tls);
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}
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