static
#endif
void __init_libc(char **envp, char *pn)
{
size_t i, *auxv, aux[AUX_CNT] = { 0 };
__environ = envp;
for (i=0; envp[i]; i++);
libc.auxv = auxv = (void *)(envp+i+1);
for (i=0; auxv[i]; i+=2) if (auxv[i]<AUX_CNT) aux[auxv[i]] = auxv[i+1];
__hwcap = aux[AT_HWCAP];
__sysinfo = aux[AT_SYSINFO];
libc.page_size = aux[AT_PAGESZ];
if (pn) {
__progname = __progname_full = pn;
for (i=0; pn[i]; i++) if (pn[i]=='/') __progname = pn+i+1;
}
__init_tls(aux);
__init_ssp((void *)aux[AT_RANDOM]);
if (aux[AT_UID]==aux[AT_EUID] && aux[AT_GID]==aux[AT_EGID]
&& !aux[AT_SECURE]) return;
struct pollfd pfd[3] = { {.fd=0}, {.fd=1}, {.fd=2} };
/* 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);
}
void __libc_init_common(uintptr_t *elfdata)
{
int argc = *elfdata;
char** argv = (char**)(elfdata + 1);
char** envp = argv + argc + 1;
pthread_attr_t thread_attr;
static pthread_internal_t thread;
static void* tls_area[BIONIC_TLS_SLOTS];
/* setup pthread runtime and maint thread descriptor */
unsigned stacktop = (__get_sp() & ~(PAGE_SIZE - 1)) + PAGE_SIZE;
unsigned stacksize = 128 * 1024;
unsigned stackbottom = stacktop - stacksize;
pthread_attr_init(&thread_attr);
pthread_attr_setstack(&thread_attr, (void*)stackbottom, stacksize);
_init_thread(&thread, gettid(), &thread_attr, (void*)stackbottom);
__init_tls(tls_area, &thread);
/* clear errno - requires TLS area */
errno = 0;
/* set program name */
__progname = argv[0] ? argv[0] : "<unknown>";
/* setup environment pointer */
environ = envp;
/* setup system properties - requires environment */
__system_properties_init();
}
/* 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 gThreadList. This
* has to be done later from libc itself (see __libc_init_common).
*
* This function also stores the elf_data argument in a specific TLS slot to be later
* picked up by the libc constructor.
*/
void __libc_init_tls(unsigned** elf_data) {
unsigned stack_top = (__get_sp() & ~(PAGE_SIZE - 1)) + PAGE_SIZE;
unsigned stack_size = 128 * 1024;
unsigned stack_bottom = stack_top - stack_size;
pthread_attr_t thread_attr;
pthread_attr_init(&thread_attr);
pthread_attr_setstack(&thread_attr, (void*) stack_bottom, stack_size);
static pthread_internal_t thread;
_init_thread(&thread, gettid(), &thread_attr, (void*) stack_bottom, false);
static void* tls_area[BIONIC_TLS_SLOTS];
__init_tls(tls_area, &thread);
tls_area[TLS_SLOT_BIONIC_PREINIT] = elf_data;
}
/* 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 gThreadList. 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;
uintptr_t stack_top = (__get_sp() & ~(PAGE_SIZE - 1)) + PAGE_SIZE;
size_t stack_size = get_main_thread_stack_size();
uintptr_t stack_bottom = stack_top - stack_size;
static void* tls[BIONIC_TLS_SLOTS];
static pthread_internal_t thread;
thread.tid = gettid();
thread.tls = tls;
pthread_attr_init(&thread.attr);
pthread_attr_setstack(&thread.attr, (void*) stack_bottom, stack_size);
_init_thread(&thread, false);
__init_tls(&thread);
tls[TLS_SLOT_BIONIC_PREINIT] = &args;
}
void __init_libc(char **envp, char *pn)
{
size_t i, *auxv, aux[AUX_CNT] = { 0 };
__environ = envp;
for (i=0; envp[i]; i++);
libc.auxv = auxv = (void *)(envp+i+1);
for (i=0; auxv[i]; i+=2) if (auxv[i]<AUX_CNT) aux[auxv[i]] = auxv[i+1];
__hwcap = aux[AT_HWCAP];
__sysinfo = aux[AT_SYSINFO];
if (pn) {
__progname = __progname_full = pn;
for (i=0; pn[i]; i++) if (pn[i]=='/') __progname = pn+i+1;
}
__init_tls(aux);
__init_security(aux);
}
static int __allocate_thread(pthread_attr_t* attr, pthread_internal_t** threadp, void** child_stack) {
size_t mmap_size;
uint8_t* stack_top;
if (attr->stack_base == NULL) {
// The caller didn't provide a stack, so allocate one.
// Make sure the stack size and guard size are multiples of PAGE_SIZE.
mmap_size = BIONIC_ALIGN(attr->stack_size + sizeof(pthread_internal_t), PAGE_SIZE);
attr->guard_size = BIONIC_ALIGN(attr->guard_size, PAGE_SIZE);
attr->stack_base = __create_thread_mapped_space(mmap_size, attr->guard_size);
if (attr->stack_base == NULL) {
return EAGAIN;
}
stack_top = reinterpret_cast<uint8_t*>(attr->stack_base) + mmap_size;
} else {
// Remember the mmap size is zero and we don't need to free it.
mmap_size = 0;
stack_top = reinterpret_cast<uint8_t*>(attr->stack_base) + attr->stack_size;
}
// Mapped space(or user allocated stack) is used for:
// pthread_internal_t
// thread stack (including guard page)
// To safely access the pthread_internal_t and thread stack, we need to find a 16-byte aligned boundary.
stack_top = reinterpret_cast<uint8_t*>(
(reinterpret_cast<uintptr_t>(stack_top) - sizeof(pthread_internal_t)) & ~0xf);
pthread_internal_t* thread = reinterpret_cast<pthread_internal_t*>(stack_top);
if (mmap_size == 0) {
// If thread was not allocated by mmap(), it may not have been cleared to zero.
// So assume the worst and zero it.
memset(thread, 0, sizeof(pthread_internal_t));
}
attr->stack_size = stack_top - reinterpret_cast<uint8_t*>(attr->stack_base);
thread->mmap_size = mmap_size;
thread->attr = *attr;
__init_tls(thread);
*threadp = thread;
*child_stack = stack_top;
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);
}
// This trampoline is called from the assembly _pthread_clone() function.
extern "C" void __thread_entry(void* (*func)(void*), void* arg, void** tls) {
// 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*) &tls[TLS_SLOT_SELF];
pthread_mutex_lock(start_mutex);
pthread_mutex_destroy(start_mutex);
pthread_internal_t* thread = (pthread_internal_t*) tls[TLS_SLOT_THREAD_ID];
thread->tls = tls;
__init_tls(thread);
if ((thread->internal_flags & kPthreadInitFailed) != 0) {
pthread_exit(NULL);
}
void* result = func(arg);
pthread_exit(result);
}
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;
}
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;
}
