runfvp: pass-through environment variables need for GUI applications

Since 820a55d3 the environment that the FVPs run in is limited, however
this broke the use of GUI applications for the terminals.

Passthrough DISPLAY and WAYLAND_DISPLAY automatically so these continue
to work.

Signed-off-by: Ross Burton <ross.burton@arm.com>
Signed-off-by: Jon Mason <jon.mason@arm.com>

meta-arm/lib/fvp/runner.py

@@ -59,11 +59,19 @@ class FVPRunner:
     async def start(self, config, extra_args=[], terminal_choice="none"):
         cli = cli_from_config(config, terminal_choice)
         cli += extra_args
+
+        # Pass through environment variables needed for GUI applications, such
+        # as xterm, to work.
+        env = config['env']
+        for name in ('DISPLAY', 'WAYLAND_DISPLAY'):
+            if name in os.environ:
+                env[name] = os.environ[name]
+
         self._logger.debug(f"Constructed FVP call: {cli}")
         self._fvp_process = await asyncio.create_subprocess_exec(
             *cli,
             stdin=subprocess.DEVNULL, stdout=subprocess.PIPE, stderr=subprocess.STDOUT,
-            env=config['env'])
+            env=env)
 
         def detect_terminals(line):
             m = re.match(r"^(\S+): Listening for serial connection on port (\d+)$", line)

meta-arm/lib/oeqa/selftest/cases/runfvp.py

@@ -107,3 +107,25 @@ class RunnerTests(OESelftestTestCase):
                 stdout=unittest.mock.ANY,
                 stderr=unittest.mock.ANY,
                 env={"FOO":"BAR"})
+
+    @unittest.mock.patch.dict(os.environ, {"DISPLAY": ":42", "WAYLAND_DISPLAY": "wayland-42"})
+    def test_env_passthrough(self):
+        from fvp import runner
+        with self.create_mock() as m:
+            fvp = runner.FVPRunner(self.logger)
+            asyncio.run(fvp.start({
+                "fvp-bindir": "/usr/bin",
+                "exe": "FVP_Binary",
+                "parameters": {},
+                "data": [],
+                "applications": {},
+                "terminals": {},
+                "args": [],
+                "env": {"FOO": "BAR"}
+            }))
+
+            m.assert_called_once_with('/usr/bin/FVP_Binary',
+                stdin=unittest.mock.ANY,
+                stdout=unittest.mock.ANY,
+                stderr=unittest.mock.ANY,
+                env={"DISPLAY":":42", "FOO": "BAR", "WAYLAND_DISPLAY": "wayland-42"})