[asan] Make GetCurrentThread RTEMS-friendly

On RTEMS, system and user code all live in a single binary and address
space. There is no clean separation, and instrumented code may
execute before the ASan run-time is initialized (or after it has been
destroyed).

Currently, GetCurrentThread() may crash if it's called before ASan
run-time is initialized. Make it return nullptr instead.

Similarly, fix __asan_handle_no_return so that it gives up rather than
try something that may crash.

Differential Revision: https://reviews.llvm.org/D46459

llvm-svn: 332888

compiler-rt/lib/asan/asan_rtl.cc

@@ -536,6 +536,9 @@ void NOINLINE __asan_handle_no_return() {
   if (curr_thread) {
     top = curr_thread->stack_top();
     bottom = ((uptr)&local_stack - PageSize) & ~(PageSize - 1);
+  } else if (SANITIZER_RTEMS) {
+    // Give up On RTEMS.
+    return;
   } else {
     CHECK(!SANITIZER_FUCHSIA);
     // If we haven't seen this thread, try asking the OS for stack bounds.

compiler-rt/lib/asan/asan_thread.cc

@@ -394,6 +394,9 @@ static bool ThreadStackContainsAddress(ThreadContextBase *tctx_base,
 }
 
 AsanThread *GetCurrentThread() {
+  if (SANITIZER_RTEMS && !asan_inited)
+    return nullptr;
+
   AsanThreadContext *context =
       reinterpret_cast<AsanThreadContext *>(AsanTSDGet());
   if (!context) {