/* Init TLS for the initial thread. Called by the linker _before_ libc is mapped * in memory. Beware: all writes to libc globals from this function will * apply to linker-private copies and will not be visible from libc later on. * * Note: this function creates a pthread_internal_t for the initial thread and * stores the pointer in TLS, but does not add it to pthread's thread list. This * has to be done later from libc itself (see __libc_init_common). * * This function also stores a pointer to the kernel argument block in a TLS slot to be * picked up by the libc constructor. */ void __libc_init_tls(KernelArgumentBlock& args) { __libc_auxv = args.auxv; static void* tls[BIONIC_TLS_SLOTS]; static pthread_internal_t main_thread; main_thread.tls = tls; // Tell the kernel to clear our tid field when we exit, so we're like any other pthread. // As a side-effect, this tells us our pid (which is the same as the main thread's tid). main_thread.tid = __set_tid_address(&main_thread.tid); main_thread.set_cached_pid(main_thread.tid); // Work out the extent of the main thread's stack. uintptr_t stack_top = (__get_sp() & ~(PAGE_SIZE - 1)) + PAGE_SIZE; size_t stack_size = get_main_thread_stack_size(); void* stack_bottom = reinterpret_cast<void*>(stack_top - stack_size); // We don't want to free the main thread's stack even when the main thread exits // because things like environment variables with global scope live on it. pthread_attr_init(&main_thread.attr); pthread_attr_setstack(&main_thread.attr, stack_bottom, stack_size); main_thread.attr.flags = PTHREAD_ATTR_FLAG_USER_ALLOCATED_STACK | PTHREAD_ATTR_FLAG_MAIN_THREAD; __init_thread(&main_thread, false); __init_tls(&main_thread); __set_tls(main_thread.tls); tls[TLS_SLOT_BIONIC_PREINIT] = &args; __init_alternate_signal_stack(&main_thread); }
extern "C" void __libc_init_main_thread_late() { __init_bionic_tls_ptrs(__get_bionic_tcb(), __allocate_temp_bionic_tls()); // Tell the kernel to clear our tid field when we exit, so we're like any other pthread. // For threads created by pthread_create, this setup happens during the clone syscall (i.e. // CLONE_CHILD_CLEARTID). __set_tid_address(&main_thread.tid); pthread_attr_init(&main_thread.attr); // We don't want to explicitly set the main thread's scheduler attributes (http://b/68328561). pthread_attr_setinheritsched(&main_thread.attr, PTHREAD_INHERIT_SCHED); // The main thread has no guard page. pthread_attr_setguardsize(&main_thread.attr, 0); // User code should never see this; we'll compute it when asked. pthread_attr_setstacksize(&main_thread.attr, 0); // The TLS stack guard is set from the global, so ensure that we've initialized the global // before we initialize the TLS. Dynamic executables will initialize their copy of the global // stack protector from the one in the main thread's TLS. __libc_safe_arc4random_buf(&__stack_chk_guard, sizeof(__stack_chk_guard)); __init_tcb_stack_guard(__get_bionic_tcb()); __init_thread(&main_thread); __init_additional_stacks(&main_thread); }
void pthread_exit(void* return_value) { pthread_internal_t* thread = __get_thread(); ... if ((thread->attr.flags & PTHREAD_ATTR_FLAG_DETACHED) != 0) { // The thread is detached, so we can free the pthread_internal_t. // First make sure that the kernel does not try to clear the tid field // because we'll have freed the memory before the thread actually exits. __set_tid_address(NULL); _pthread_internal_remove_locked(thread); } else { // Make sure that the pthread_internal_t doesn't have stale pointers to a stack that // will be unmapped after the exit call below. if (!user_allocated_stack) { thread->attr.stack_base = NULL; thread->attr.stack_size = 0; thread->tls = NULL; } // pthread_join is responsible for destroying the pthread_internal_t for non-detached threads. // The kernel will futex_wake on the pthread_internal_t::tid field to wake pthread_join. } pthread_mutex_unlock(&g_thread_list_lock); // Perform a second key cleanup. When using jemalloc, a call to free from // _pthread_internal_remove_locked causes the memory associated with a key // to be reallocated. // TODO: When b/16847284 is fixed this call can be removed. pthread_key_clean_all(); if (user_allocated_stack) { // Cleaning up this thread's stack is the creator's responsibility, not ours. __exit(0); } else { // We need to munmap the stack we're running on before calling exit. // That's not something we can do in C. // We don't want to take a signal after we've unmapped the stack. // That's one last thing we can handle in C. sigset_t mask; sigfillset(&mask); sigprocmask(SIG_SETMASK, &mask, NULL); _exit_with_stack_teardown(stack_base, stack_size); } }
void __libc_init_main_thread(KernelArgumentBlock& args) { __libc_auxv = args.auxv; #if defined(__i386__) __libc_init_sysinfo(args); #endif static pthread_internal_t main_thread; // The -fstack-protector implementation uses TLS, so make sure that's // set up before we call any function that might get a stack check inserted. // TLS also needs to be set up before errno (and therefore syscalls) can be used. __set_tls(main_thread.tls); __init_tls(&main_thread); // Tell the kernel to clear our tid field when we exit, so we're like any other pthread. // As a side-effect, this tells us our pid (which is the same as the main thread's tid). main_thread.tid = __set_tid_address(&main_thread.tid); main_thread.set_cached_pid(main_thread.tid); // We don't want to free the main thread's stack even when the main thread exits // because things like environment variables with global scope live on it. // We also can't free the pthread_internal_t itself, since that lives on the main // thread's stack rather than on the heap. // The main thread has no mmap allocated space for stack or pthread_internal_t. main_thread.mmap_size = 0; pthread_attr_init(&main_thread.attr); main_thread.attr.guard_size = 0; // The main thread has no guard page. main_thread.attr.stack_size = 0; // User code should never see this; we'll compute it when asked. // TODO: the main thread's sched_policy and sched_priority need to be queried. // The TLS stack guard is set from the global, so ensure that we've initialized the global // before we initialize the TLS. Dynamic executables will initialize their copy of the global // stack protector from the one in the main thread's TLS. __libc_init_global_stack_chk_guard(args); __init_thread_stack_guard(&main_thread); __init_thread(&main_thread); // Store a pointer to the kernel argument block in a TLS slot to be // picked up by the libc constructor. main_thread.tls[TLS_SLOT_BIONIC_PREINIT] = &args; __init_alternate_signal_stack(&main_thread); }
void pthread_exit(void* return_value) { pthread_internal_t* thread = __get_thread(); thread->return_value = return_value; // Call the cleanup handlers first. while (thread->cleanup_stack) { __pthread_cleanup_t* c = thread->cleanup_stack; thread->cleanup_stack = c->__cleanup_prev; c->__cleanup_routine(c->__cleanup_arg); } // Call the TLS destructors. It is important to do that before removing this // thread from the global list. This will ensure that if someone else deletes // a TLS key, the corresponding value will be set to NULL in this thread's TLS // space (see pthread_key_delete). pthread_key_clean_all(); if (thread->alternate_signal_stack != NULL) { // Tell the kernel to stop using the alternate signal stack. stack_t ss; ss.ss_sp = NULL; ss.ss_flags = SS_DISABLE; sigaltstack(&ss, NULL); // Free it. munmap(thread->alternate_signal_stack, SIGSTKSZ); thread->alternate_signal_stack = NULL; } // Keep track of what we need to know about the stack before we lose the pthread_internal_t. void* stack_base = thread->attr.stack_base; size_t stack_size = thread->attr.stack_size; bool user_allocated_stack = ((thread->attr.flags & PTHREAD_ATTR_FLAG_USER_ALLOCATED_STACK) != 0); pthread_mutex_lock(&gThreadListLock); if ((thread->attr.flags & PTHREAD_ATTR_FLAG_DETACHED) != 0) { // The thread is detached, so we can free the pthread_internal_t. // First make sure that the kernel does not try to clear the tid field // because we'll have freed the memory before the thread actually exits. __set_tid_address(NULL); _pthread_internal_remove_locked(thread); } else { // Make sure that the pthread_internal_t doesn't have stale pointers to a stack that // will be unmapped after the exit call below. if (!user_allocated_stack) { thread->attr.stack_base = NULL; thread->attr.stack_size = 0; thread->tls = NULL; } // pthread_join is responsible for destroying the pthread_internal_t for non-detached threads. // The kernel will futex_wake on the pthread_internal_t::tid field to wake pthread_join. } pthread_mutex_unlock(&gThreadListLock); if (user_allocated_stack) { // Cleaning up this thread's stack is the creator's responsibility, not ours. __exit(0); } else { // We need to munmap the stack we're running on before calling exit. // That's not something we can do in C. // We don't want to take a signal after we've unmapped the stack. // That's one last thing we can handle in C. sigset_t mask; sigfillset(&mask); sigprocmask(SIG_SETMASK, &mask, NULL); _exit_with_stack_teardown(stack_base, stack_size, 0); } // NOTREACHED, but we told the compiler this function is noreturn, and it doesn't believe us. abort(); }