/* 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); }
static int __pthread_start(void* arg) { pthread_internal_t* thread = reinterpret_cast<pthread_internal_t*>(arg); // Wait for our creating thread to release us. This lets it have time to // notify gdb about this thread before we start doing anything. // This also provides the memory barrier needed to ensure that all memory // accesses previously made by the creating thread are visible to us. thread->startup_handshake_lock.lock(); __init_alternate_signal_stack(thread); void* result = thread->start_routine(thread->start_routine_arg); pthread_exit(result); return 0; }
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); }
static int __pthread_start(void* arg) { pthread_internal_t* thread = reinterpret_cast<pthread_internal_t*>(arg); // Wait for our creating thread to release us. This lets it have time to // notify gdb about this thread before we start doing anything. // This also provides the memory barrier needed to ensure that all memory // accesses previously made by the creating thread are visible to us. pthread_mutex_t* start_mutex = (pthread_mutex_t*) &thread->tls[TLS_SLOT_START_MUTEX]; pthread_mutex_lock(start_mutex); pthread_mutex_destroy(start_mutex); __init_tls(thread); __init_alternate_signal_stack(thread); void* result = thread->start_routine(thread->start_routine_arg); pthread_exit(result); return 0; }