debug: CeaseRunTest -> UnavailableRunTest

Use new spike mechanism to test OpenOCD behavior when the current hart
becomes unavailable while running.

Create ThreadTerminated exception.

Author: timsifive

debug/gdbserver.py

@@ -20,6 +20,7 @@
 from testlib import TestNotApplicable, CompileError
 from testlib import UnknownThread
 from testlib import CouldNotReadRegisters, CommandException
+from testlib import ThreadTerminated
 
 MSTATUS_UIE = 0x00000001
 MSTATUS_SIE = 0x00000002
@@ -1879,22 +1880,36 @@ def test(self):
         except CouldNotReadRegisters:
             pass
 
-class CeaseRunTest(ProgramTest):
+class UnavailableRunTest(ProgramTest):
     """Test that we work correctly when the hart we're debugging ceases to
     respond."""
     def early_applicable(self):
-        return self.hart.support_cease
+        return self.hart.support_cease or \
+            self.target.support_unavailable_control
 
     def test(self):
         self.gdb.b("main")
         output = self.gdb.c()
         assertIn("Breakpoint", output)
         assertIn("main", output)
 
-        self.gdb.p("$pc=precease")
+        if self.target.support_unavailable_control:
+            self.gdb.p("$pc=loop_forever")
+        else:
+            self.gdb.p("$pc=cease")
         self.gdb.c(wait=False)
+        if self.target.support_unavailable_control:
+            self.server.wait_until_running([self.hart])
+            self.server.command(
+                    f"riscv dmi_write 0x1f 0x{(~(1<<self.hart.id))&0x3:x}")
         self.gdb.expect(r"\S+ became unavailable.")
         self.gdb.interrupt()
+        # gdb might automatically switch to the available hart.
+        try:
+            self.gdb.select_hart(self.hart)
+        except ThreadTerminated:
+            # GDB sees that the thread is gone. Count this as success.
+            return
         try:
             self.gdb.p("$pc")
             assert False, ("Registers shouldn't be accessible when the hart is "

debug/testlib.py

@@ -555,6 +555,9 @@ class UnknownThread(Exception):
     def __init__(self, explanation):
         Exception.__init__(self, explanation)
 
+class ThreadTerminated(Exception):
+    pass
+
 Thread = collections.namedtuple('Thread', ('id', 'description', 'target_id',
     'name', 'frame'))
 
@@ -762,6 +765,8 @@ def select_hart(self, hart):
             output = self.command(f"thread {h['thread'].id}", ops=5)
             if "Unknown" in output:
                 raise UnknownThread(output)
+            if f"Thread ID {h['thread'].id} has terminated" in output:
+                raise ThreadTerminated(output)
 
     def push_state(self):
         self.stack.append({