tests/tcg: better trap gdb failures

It seems older and non-multiarach aware GDBs might not fail gracefully
when faced with something they don't know. For example when faced with
a target XML for s390x the Ubuntu 18.04 gdb will generate an internal
fault and prompt for a core dump.

Work around this by invoking GDB in a more batch orientated way and
then trying to filter out between test failures and gdb failures.

Signed-off-by: Alex Bennée <alex.bennee@linaro.org>
Message-Id: <20200430190122.4592-4-alex.bennee@linaro.org>

tests/guest-debug/run-test.py

@@ -50,8 +50,25 @@ if __name__ == '__main__':
     inferior = subprocess.Popen(shlex.split(cmd))
 
     # Now launch gdb with our test and collect the result
-    gdb_cmd = "%s %s -ex 'target remote localhost:1234' -x %s" % (args.gdb, args.binary, args.test)
+    gdb_cmd = "%s %s" % (args.gdb, args.binary)
+    # run quietly and ignore .gdbinit
+    gdb_cmd += " -q -n -batch"
+    # disable prompts in case of crash
+    gdb_cmd += " -ex 'set confirm off'"
+    # connect to remote
+    gdb_cmd += " -ex 'target remote localhost:1234'"
+    # finally the test script itself
+    gdb_cmd += " -x %s" % (args.test)
+
+    print("GDB CMD: %s" % (gdb_cmd))
 
     result = subprocess.call(gdb_cmd, shell=True);
 
+    # A negative result is the result of an internal gdb failure like
+    # a crash. We force a return of 0 so we don't fail the test on
+    # account of broken external tools.
+    if result < 0:
+        print("GDB crashed? SKIPPING")
+        exit(0)
+
     exit(result)

tests/tcg/aarch64/gdbstub/test-sve-ioctl.py

@@ -70,7 +70,6 @@ except (gdb.error, AttributeError):
 try:
     # These are not very useful in scripts
     gdb.execute("set pagination off")
-    gdb.execute("set confirm off")
 
     # Run the actual tests
     run_test()

tests/tcg/aarch64/gdbstub/test-sve.py

@@ -71,7 +71,6 @@ except (gdb.error, AttributeError):
 try:
     # These are not very useful in scripts
     gdb.execute("set pagination off")
-    gdb.execute("set confirm off")
 
     # Run the actual tests
     run_test()