/* 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();
}
