/* 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 __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); }
int pthread_create(pthread_t* thread_out, pthread_attr_t const* attr, void* (*start_routine)(void*), void* arg) { ErrnoRestorer errno_restorer; // Inform the rest of the C library that at least one thread was created. __isthreaded = 1; pthread_internal_t* thread = reinterpret_cast<pthread_internal_t*>(calloc(sizeof(*thread), 1)); if (thread == NULL) { __libc_format_log(ANDROID_LOG_WARN, "libc", "pthread_create failed: couldn't allocate thread"); return EAGAIN; } if (attr == NULL) { pthread_attr_init(&thread->attr); } else { thread->attr = *attr; attr = NULL; // Prevent misuse below. } // Make sure the stack size and guard size are multiples of PAGE_SIZE. thread->attr.stack_size = BIONIC_ALIGN(thread->attr.stack_size, PAGE_SIZE); thread->attr.guard_size = BIONIC_ALIGN(thread->attr.guard_size, PAGE_SIZE); if (thread->attr.stack_base == NULL) { // The caller didn't provide a stack, so allocate one. thread->attr.stack_base = __create_thread_stack(thread); if (thread->attr.stack_base == NULL) { free(thread); return EAGAIN; } } else { // The caller did provide a stack, so remember we're not supposed to free it. thread->attr.flags |= PTHREAD_ATTR_FLAG_USER_ALLOCATED_STACK; } // Make room for the TLS area. // The child stack is the same address, just growing in the opposite direction. // At offsets >= 0, we have the TLS slots. // At offsets < 0, we have the child stack. thread->tls = reinterpret_cast<void**>(reinterpret_cast<uint8_t*>(thread->attr.stack_base) + thread->attr.stack_size - BIONIC_TLS_SLOTS * sizeof(void*)); void* child_stack = thread->tls; __init_tls(thread); // Create a mutex for the thread in TLS to wait on once it starts so we can keep // it from doing anything until after we notify the debugger about it // // This also provides the memory barrier we need to ensure that all // memory accesses previously performed by this thread are visible to // the new thread. pthread_mutex_init(&thread->startup_handshake_mutex, NULL); pthread_mutex_lock(&thread->startup_handshake_mutex); thread->start_routine = start_routine; thread->start_routine_arg = arg; thread->set_cached_pid(getpid()); int flags = CLONE_VM | CLONE_FS | CLONE_FILES | CLONE_SIGHAND | CLONE_THREAD | CLONE_SYSVSEM | CLONE_SETTLS | CLONE_PARENT_SETTID | CLONE_CHILD_CLEARTID; void* tls = thread->tls; #if defined(__i386__) // On x86 (but not x86-64), CLONE_SETTLS takes a pointer to a struct user_desc rather than // a pointer to the TLS itself. user_desc tls_descriptor; __init_user_desc(&tls_descriptor, false, tls); tls = &tls_descriptor; #endif int rc = clone(__pthread_start, child_stack, flags, thread, &(thread->tid), tls, &(thread->tid)); if (rc == -1) { int clone_errno = errno; // We don't have to unlock the mutex at all because clone(2) failed so there's no child waiting to // be unblocked, but we're about to unmap the memory the mutex is stored in, so this serves as a // reminder that you can't rewrite this function to use a ScopedPthreadMutexLocker. pthread_mutex_unlock(&thread->startup_handshake_mutex); if ((thread->attr.flags & PTHREAD_ATTR_FLAG_USER_ALLOCATED_STACK) == 0) { munmap(thread->attr.stack_base, thread->attr.stack_size); } free(thread); __libc_format_log(ANDROID_LOG_WARN, "libc", "pthread_create failed: clone failed: %s", strerror(errno)); return clone_errno; } int init_errno = __init_thread(thread, true); if (init_errno != 0) { // Mark the thread detached and replace its start_routine with a no-op. // Letting the thread run is the easiest way to clean up its resources. thread->attr.flags |= PTHREAD_ATTR_FLAG_DETACHED; thread->start_routine = __do_nothing; pthread_mutex_unlock(&thread->startup_handshake_mutex); return init_errno; } // Publish the pthread_t and unlock the mutex to let the new thread start running. *thread_out = reinterpret_cast<pthread_t>(thread); pthread_mutex_unlock(&thread->startup_handshake_mutex); return 0; }
int pthread_create(pthread_t* thread_out, pthread_attr_t const* attr, void* (*start_routine)(void*), void* arg) { ErrnoRestorer errno_restorer; // Inform the rest of the C library that at least one thread was created. __isthreaded = 1; pthread_attr_t thread_attr; if (attr == NULL) { pthread_attr_init(&thread_attr); } else { thread_attr = *attr; attr = NULL; // Prevent misuse below. } pthread_internal_t* thread = NULL; void* child_stack = NULL; int result = __allocate_thread(&thread_attr, &thread, &child_stack); if (result != 0) { return result; } // Create a lock for the thread to wait on once it starts so we can keep // it from doing anything until after we notify the debugger about it // // This also provides the memory barrier we need to ensure that all // memory accesses previously performed by this thread are visible to // the new thread. thread->startup_handshake_lock.init(false); thread->startup_handshake_lock.lock(); thread->start_routine = start_routine; thread->start_routine_arg = arg; thread->set_cached_pid(getpid()); int flags = CLONE_VM | CLONE_FS | CLONE_FILES | CLONE_SIGHAND | CLONE_THREAD | CLONE_SYSVSEM | CLONE_SETTLS | CLONE_PARENT_SETTID | CLONE_CHILD_CLEARTID; void* tls = reinterpret_cast<void*>(thread->tls); #if defined(__i386__) // On x86 (but not x86-64), CLONE_SETTLS takes a pointer to a struct user_desc rather than // a pointer to the TLS itself. user_desc tls_descriptor; __init_user_desc(&tls_descriptor, false, tls); tls = &tls_descriptor; #endif int rc = clone(__pthread_start, child_stack, flags, thread, &(thread->tid), tls, &(thread->tid)); if (rc == -1) { int clone_errno = errno; // We don't have to unlock the mutex at all because clone(2) failed so there's no child waiting to // be unblocked, but we're about to unmap the memory the mutex is stored in, so this serves as a // reminder that you can't rewrite this function to use a ScopedPthreadMutexLocker. thread->startup_handshake_lock.unlock(); if (thread->mmap_size != 0) { munmap(thread->attr.stack_base, thread->mmap_size); } __libc_format_log(ANDROID_LOG_WARN, "libc", "pthread_create failed: clone failed: %s", strerror(errno)); return clone_errno; } int init_errno = __init_thread(thread); if (init_errno != 0) { // Mark the thread detached and replace its start_routine with a no-op. // Letting the thread run is the easiest way to clean up its resources. atomic_store(&thread->join_state, THREAD_DETACHED); __pthread_internal_add(thread); thread->start_routine = __do_nothing; thread->startup_handshake_lock.unlock(); return init_errno; } // Publish the pthread_t and unlock the mutex to let the new thread start running. *thread_out = __pthread_internal_add(thread); thread->startup_handshake_lock.unlock(); return 0; }
int pthread_create(pthread_t* thread_out, pthread_attr_t const* attr, void* (*start_routine)(void*), void* arg) { ErrnoRestorer errno_restorer; // Inform the rest of the C library that at least one thread // was created. This will enforce certain functions to acquire/release // locks (e.g. atexit()) to protect shared global structures. // This works because pthread_create() is not called by the C library // initialization routine that sets up the main thread's data structures. __isthreaded = 1; pthread_internal_t* thread = reinterpret_cast<pthread_internal_t*>(calloc(sizeof(*thread), 1)); if (thread == NULL) { __libc_format_log(ANDROID_LOG_WARN, "libc", "pthread_create failed: couldn't allocate thread"); return EAGAIN; } if (attr == NULL) { pthread_attr_init(&thread->attr); } else { thread->attr = *attr; attr = NULL; // Prevent misuse below. } // Make sure the stack size and guard size are multiples of PAGE_SIZE. thread->attr.stack_size = (thread->attr.stack_size + (PAGE_SIZE-1)) & ~(PAGE_SIZE-1); thread->attr.guard_size = (thread->attr.guard_size + (PAGE_SIZE-1)) & ~(PAGE_SIZE-1); if (thread->attr.stack_base == NULL) { // The caller didn't provide a stack, so allocate one. thread->attr.stack_base = __create_thread_stack(thread); if (thread->attr.stack_base == NULL) { free(thread); return EAGAIN; } } else { // The caller did provide a stack, so remember we're not supposed to free it. thread->attr.flags |= PTHREAD_ATTR_FLAG_USER_ALLOCATED_STACK; } // Make room for the TLS area. // The child stack is the same address, just growing in the opposite direction. // At offsets >= 0, we have the TLS slots. // At offsets < 0, we have the child stack. thread->tls = (void**)((uint8_t*)(thread->attr.stack_base) + thread->attr.stack_size - BIONIC_TLS_SLOTS * sizeof(void*)); void* child_stack = thread->tls; // Create a mutex for the thread in TLS to wait on once it starts so we can keep // it from doing anything until after we notify the debugger about it // // This also provides the memory barrier we need to ensure that all // memory accesses previously performed by this thread are visible to // the new thread. pthread_mutex_t* start_mutex = (pthread_mutex_t*) &thread->tls[TLS_SLOT_START_MUTEX]; pthread_mutex_init(start_mutex, NULL); pthread_mutex_lock(start_mutex); thread->tls[TLS_SLOT_THREAD_ID] = thread; thread->start_routine = start_routine; thread->start_routine_arg = arg; int flags = CLONE_VM | CLONE_FS | CLONE_FILES | CLONE_SIGHAND | CLONE_THREAD | CLONE_SYSVSEM | CLONE_SETTLS | CLONE_PARENT_SETTID | CLONE_CHILD_CLEARTID; #if defined(__i386__) // On x86 (but not x86-64), CLONE_SETTLS takes a pointer to a struct user_desc rather than // a pointer to the TLS itself. Rather than try to deal with that here, we just let x86 set // the TLS manually in __init_tls, like all architectures used to. flags &= ~CLONE_SETTLS; #endif int rc = __bionic_clone(flags, child_stack, &(thread->tid), thread->tls, &(thread->tid), __pthread_start, thread); if (rc == -1) { int clone_errno = errno; // We don't have to unlock the mutex at all because clone(2) failed so there's no child waiting to // be unblocked, but we're about to unmap the memory the mutex is stored in, so this serves as a // reminder that you can't rewrite this function to use a ScopedPthreadMutexLocker. pthread_mutex_unlock(start_mutex); if ((thread->attr.flags & PTHREAD_ATTR_FLAG_USER_ALLOCATED_STACK) == 0) { munmap(thread->attr.stack_base, thread->attr.stack_size); } free(thread); __libc_format_log(ANDROID_LOG_WARN, "libc", "pthread_create failed: clone failed: %s", strerror(errno)); return clone_errno; } int init_errno = __init_thread(thread, true); if (init_errno != 0) { // Mark the thread detached and replace its start_routine with a no-op. // Letting the thread run is the easiest way to clean up its resources. thread->attr.flags |= PTHREAD_ATTR_FLAG_DETACHED; thread->start_routine = __do_nothing; pthread_mutex_unlock(start_mutex); return init_errno; } // Notify any debuggers about the new thread. { ScopedPthreadMutexLocker debugger_locker(&gDebuggerNotificationLock); _thread_created_hook(thread->tid); } // Publish the pthread_t and unlock the mutex to let the new thread start running. *thread_out = reinterpret_cast<pthread_t>(thread); pthread_mutex_unlock(start_mutex); return 0; }