[lldb/qemu] Add emulator-env-vars setting

This setting is for variables we want to pass to the emulator only --
then will be automatically removed from the target environment by our
environment diffing code. This variable can be used to pass various
QEMU_*** variables (although most of these can be passed through
emulator-args as well), as well as any other variables that can affect
the operation of the emulator (e.g. LD_LIBRARY_PATH).

lldb/source/Plugins/Platform/QemuUser/PlatformQemuUser.cpp

@@ -55,6 +55,13 @@ public:
     return result;
   }
 
+  Environment GetEmulatorEnvVars() {
+    Args args;
+    m_collection_sp->GetPropertyAtIndexAsArgs(nullptr, ePropertyEmulatorEnvVars,
+                                              args);
+    return Environment(args);
+  }
+
   Environment GetTargetEnvVars() {
     Args args;
     m_collection_sp->GetPropertyAtIndexAsArgs(nullptr, ePropertyTargetEnvVars,
@@ -175,8 +182,13 @@ lldb::ProcessSP PlatformQemuUser::DebugProcess(ProcessLaunchInfo &launch_info,
            get_arg_range(args));
 
   launch_info.SetArguments(args, true);
+
+  Environment emulator_env = Host::GetEnvironment();
+  for (const auto &KV : GetGlobalProperties().GetEmulatorEnvVars())
+    emulator_env[KV.first()] = KV.second;
   launch_info.GetEnvironment() = ComputeLaunchEnvironment(
-      std::move(launch_info.GetEnvironment()), Host::GetEnvironment());
+      std::move(launch_info.GetEnvironment()), std::move(emulator_env));
+
   launch_info.SetLaunchInSeparateProcessGroup(true);
   launch_info.GetFlags().Clear(eLaunchFlagDebug);
   launch_info.SetMonitorProcessCallback(ProcessLaunchInfo::NoOpMonitorCallback,

lldb/source/Plugins/Platform/QemuUser/PlatformQemuUserProperties.td

@@ -13,7 +13,12 @@ let Definition = "platformqemuuser" in {
     Global,
     DefaultStringValue<"">,
     Desc<"Extra arguments to pass to the emulator.">;
+  def EmulatorEnvVars: Property<"emulator-env-vars", "Dictionary">,
+    Global,
+    ElementType<"String">,
+    Desc<"Extra variables to add to the emulator environment.">;
   def TargetEnvVars: Property<"target-env-vars", "Dictionary">,
+    Global,
     ElementType<"String">,
     Desc<"Extra variables to add to emulated target environment.">;
 }

lldb/test/API/qemu/TestQemuLaunch.py

@@ -171,7 +171,7 @@ class TestQemuLaunch(TestBase):
 
         self.assertEqual(state["fake-arg"], "fake-value")
 
-    def test_target_env_vars(self):
+    def test_env_vars(self):
         # First clear any global environment to have a clean slate for this test
         self.runCmd("settings clear target.env-vars")
         self.runCmd("settings clear target.unset-env-vars")
@@ -187,6 +187,10 @@ class TestQemuLaunch(TestBase):
                 del os.environ[var(i)]
         self.addTearDownHook(cleanup)
 
+        # Set some emulator-only variables.
+        self.set_emulator_setting("emulator-env-vars",
+                "%s='emulator only'"%var(4))
+
         # And through the platform setting.
         self.set_emulator_setting("target-env-vars",
                 "%s='from platform' %s='from platform'" % (var(1), var(2)))
@@ -195,11 +199,13 @@ class TestQemuLaunch(TestBase):
         info = target.GetLaunchInfo()
         env = info.GetEnvironment()
 
-        # Platform settings should trump host values.
+        # Platform settings should trump host values. Emulator-only variables
+        # should not be visible.
         self.assertEqual(env.Get(var(0)), "from host")
         self.assertEqual(env.Get(var(1)), "from platform")
         self.assertEqual(env.Get(var(2)), "from platform")
         self.assertEqual(env.Get(var(3)), "from host")
+        self.assertIsNone(env.Get(var(4)))
 
         # Finally, make some launch_info specific changes.
         env.Set(var(2), "from target", True)
@@ -212,7 +218,8 @@ class TestQemuLaunch(TestBase):
         state = self._run_and_get_state(target, info)
         for i in range(4):
             self.assertEqual(state["environ"][var(i)], "from host")
+        self.assertEqual(state["environ"][var(4)], "emulator only")
         self.assertEqual(state["environ"]["QEMU_SET_ENV"],
                 "%s=from platform,%s=from target" % (var(1), var(2)))
         self.assertEqual(state["environ"]["QEMU_UNSET_ENV"],
-                "%s,QEMU_SET_ENV,QEMU_UNSET_ENV" % var(3))
+                "%s,%s,QEMU_SET_ENV,QEMU_UNSET_ENV" % (var(3), var(4)))