int NaClMachThreadIsInUntrusted(mach_port_t thread_port) {
x86_thread_state_t state;
thread_state_t statep = (thread_state_t) &state;
mach_msg_type_number_t size = x86_THREAD_STATE_COUNT;
kern_return_t kr;
uint32_t nacl_thread_index;
kr = thread_get_state(thread_port, x86_THREAD_STATE, statep, &size);
if (kr != KERN_SUCCESS) {
NaClLog(LOG_FATAL, "NaClMachThreadIsInUntrusted: "
"thread_get_state() failed with error %i\n", kr);
}
CHECK(kr == KERN_SUCCESS);
#if NACL_BUILD_SUBARCH == 32
CHECK(state.tsh.flavor == x86_THREAD_STATE32);
nacl_thread_index = state.uts.ts32.__gs >> 3;
#elif NACL_BUILD_SUBARCH == 64
nacl_thread_index = NaClGetThreadIndexForMachThread(thread_port);
/*
* If the thread isn't known to Native Client, it's not untrusted (at least
* not by Native Client.)
*/
if (nacl_thread_index == NACL_TLS_INDEX_INVALID) {
return 0;
}
#endif
return NaClMachThreadStateIsInUntrusted(&state, nacl_thread_index);
}
void NaClSetCurrentMachThreadForThreadIndex(uint32_t nacl_thread_index) {
/*
* This implementation relies on the Mach port for the thread stored by the
* pthread library, and assumes that the pthread library does not close and
* re-acquire the Mach port for the thread. If that happens, Mach could
* theoretically assign the port a different number in the process' port
* table. This approach avoids having to deal with ownership of the port and
* the system call overhad to obtain and deallocate it as would be the case
* with mach_thread_self().
*
* When used by the Mach exception handler, this also assumes that the
* thread port number when received for an exception will match the port
* stored in the mach_threads table. This is guaranteed by how the kernel
* coalesces ports in a single port namespace. (A task, or process, is a
* single port namespace.)
*
* An alternative implementation that works on Mac OS X 10.6 or higher is to
* use pthread_threadid_np() to obtain a thread ID to use as the key for
* this thread map. Such thread IDs are unique system-wide. An exception
* handler can find the thread ID for a Mach thread by calling thread_info()
* with flavor THREAD_IDENTIFIER_INFO. This approach is not used here
* because of the added system call overhead at exception time.
*/
mach_port_t mach_thread = pthread_mach_thread_np(pthread_self());
CHECK(mach_thread != MACH_PORT_NULL);
DCHECK(nacl_thread_index > NACL_TLS_INDEX_INVALID &&
nacl_thread_index < NACL_THREAD_MAX);
DCHECK(mach_threads[nacl_thread_index] == MACH_PORT_NULL);
DCHECK(NaClGetThreadIndexForMachThread(mach_thread) ==
NACL_TLS_INDEX_INVALID);
mach_threads[nacl_thread_index] = mach_thread;
}
void NaClClearMachThreadForThreadIndex(uint32_t nacl_thread_index) {
mach_port_t mach_thread = mach_threads[nacl_thread_index];
DCHECK(nacl_thread_index > NACL_TLS_INDEX_INVALID &&
nacl_thread_index < NACL_THREAD_MAX);
DCHECK(mach_thread == pthread_mach_thread_np(pthread_self()));
mach_threads[nacl_thread_index] = MACH_PORT_NULL;
DCHECK(NaClGetThreadIndexForMachThread(mach_thread) ==
NACL_TLS_INDEX_INVALID);
}
