TEST(pthread, __bionic_clone) {
// Check that our hand-written clone assembler sets errno correctly on failure.
uintptr_t fake_child_stack[16];
errno = 0;
ASSERT_EQ(-1, __bionic_clone(CLONE_THREAD, &fake_child_stack[0], NULL, NULL, NULL, NULL, NULL));
ASSERT_EQ(EINVAL, errno);
}
TEST(pthread, __bionic_clone) {
#if defined(__BIONIC__)
// Check that our hand-written clone assembler sets errno correctly on failure.
uintptr_t fake_child_stack[16];
errno = 0;
ASSERT_EQ(-1, __bionic_clone(CLONE_THREAD, &fake_child_stack[16], NULL, NULL, NULL, NULL, NULL));
ASSERT_EQ(EINVAL, errno);
#else // __BIONIC__
GTEST_LOG_(INFO) << "This test does nothing.\n";
#endif // __BIONIC__
}
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;
}
