[lldb] Run the LLDB test suite under MTE on capable Apple HW (#185780)

This PR adds support for running the LLDB test suite under MTE. It's
enabled by default on capable hardware when asserts are enabled. It
relies on a launcher (#185921) which launches the process with the
appropriate posix_spawn attribute. One thing worth noting here is that
child processes inherit the MTE property, so binaries launched by the
test suite in this mode also run under MTE.

Besides the logic to detect the default and thread through the launcher,
I also had to make a small change to LLVM LIT's `ToolSubst` class to
support an optional launcher for the shell tests.

lldb/cmake/modules/LLDBConfig.cmake

@@ -163,6 +163,27 @@ if (LLDB_ENABLE_LIBEDIT)
   set(CMAKE_EXTRA_INCLUDE_FILES)
 endif()
 
+if (APPLE)
+  set(default_enable_mte OFF)
+
+  execute_process(
+      COMMAND sysctl -n hw.optional.arm.FEAT_MTE4
+      OUTPUT_VARIABLE SYSCTL_OUTPUT
+      ERROR_QUIET
+      RESULT_VARIABLE SYSCTL_RESULT
+      OUTPUT_STRIP_TRAILING_WHITESPACE
+  )
+  if(SYSCTL_RESULT EQUAL 0)
+    set(default_enable_mte ON)
+  endif()
+
+  option(LLDB_ENABLE_MTE "Run the LLDB test suite with MTE enabled." ${default_enable_mte})
+
+  if (LLDB_ENABLE_MTE)
+    message(STATUS "Running the LLDB test suite with MTE")
+  endif()
+endif()
+
 if (LLDB_ENABLE_PYTHON)
   if(CMAKE_SYSTEM_NAME MATCHES "Windows")
     set(default_embed_python_home ON)

lldb/test/API/lit.site.cfg.py.in

@@ -42,6 +42,7 @@ config.has_libcxx = @LLDB_HAS_LIBCXX@
 config.libcxx_libs_dir = "@LIBCXX_LIBRARY_DIR@"
 config.libcxx_include_dir = "@LIBCXX_GENERATED_INCLUDE_DIR@"
 config.libcxx_include_target_dir = "@LIBCXX_GENERATED_INCLUDE_TARGET_DIR@"
+config.lldb_launcher = "@LLDB_LAUNCHER@"
 # The API tests use their own module caches.
 config.lldb_module_cache = os.path.join("@LLDB_TEST_MODULE_CACHE_LLDB@", "lldb-api")
 config.clang_module_cache = os.path.join("@LLDB_TEST_MODULE_CACHE_CLANG@", "lldb-api")

lldb/test/API/lldbtest.py

@@ -55,6 +55,10 @@ class LLDBTest(TestFormat):
         # python exe as the first parameter of the command.
         cmd = [executable] + self.dotest_cmd + [testPath, "-p", testFile]
 
+        launcher = getattr(test.config, "lldb_launcher", None)
+        if launcher:
+            cmd = [launcher] + cmd
+
         if isLuaTest:
             cmd.extend(["--env", "LUA_EXECUTABLE=%s" % test.config.lua_executable])
             cmd.extend(["--env", "LLDB_LUA_CPATH=%s" % test.config.lldb_lua_cpath])

lldb/test/CMakeLists.txt

@@ -132,6 +132,11 @@ if(TARGET lldb-framework)
   add_lldb_test_dependency(lldb-framework)
 endif()
 
+if(TARGET darwin-mte-launcher)
+  add_lldb_test_dependency(darwin-mte-launcher)
+  set(LLDB_LAUNCHER ${LLVM_RUNTIME_OUTPUT_INTDIR}/darwin-mte-launcher${CMAKE_EXECUTABLE_SUFFIX})
+endif()
+
 if (LLDB_CAN_USE_LLDB_RPC_SERVER)
   add_lldb_test_dependency(lldb-rpc-generate-sources)
 endif()

lldb/test/Shell/helper/toolchain.py

@@ -118,24 +118,28 @@ def use_lldb_substitutions(config):
         build_script_args.append("--sysroot={0}".format(config.cmake_sysroot))
 
     lldb_init = _get_lldb_init_path(config)
+    launcher = getattr(config, "lldb_launcher", None)
 
     primary_tools = [
         ToolSubst(
             "%lldb",
             command=FindTool("lldb"),
             extra_args=get_lldb_args(config),
+            launcher=launcher,
             unresolved="fatal",
         ),
         ToolSubst(
             "%lldb-init",
             command=FindTool("lldb"),
             extra_args=["-S", lldb_init],
+            launcher=launcher,
             unresolved="fatal",
         ),
         ToolSubst(
             "%lldb-noinit",
             command=FindTool("lldb"),
             extra_args=["--no-lldbinit"],
+            launcher=launcher,
             unresolved="fatal",
         ),
         ToolSubst(

lldb/test/Shell/lit.site.cfg.py.in

@@ -35,6 +35,7 @@ config.lldb_system_debugserver = @LLDB_USE_SYSTEM_DEBUGSERVER@
 config.llvm_use_sanitizer = "@LLVM_USE_SANITIZER@"
 config.lldb_has_lldbrpc = @LLDB_BUILD_LLDBRPC@
 config.have_dia_sdk = @LLVM_ENABLE_DIA_SDK@
+config.lldb_launcher = "@LLDB_LAUNCHER@"
 # The shell tests use their own module caches.
 config.lldb_module_cache = os.path.join("@LLDB_TEST_MODULE_CACHE_LLDB@", "lldb-shell")
 config.clang_module_cache = os.path.join("@LLDB_TEST_MODULE_CACHE_CLANG@", "lldb-shell")

lldb/tools/CMakeLists.txt

@@ -20,7 +20,9 @@ endif()
 
 if (CMAKE_SYSTEM_NAME MATCHES "Darwin")
   add_lldb_tool_subdirectory(darwin-debug)
-  add_lldb_tool_subdirectory(darwin-mte-launcher)
+  if (LLDB_ENABLE_MTE)
+    add_lldb_tool_subdirectory(darwin-mte-launcher)
+  endif()
   if(NOT LLDB_USE_SYSTEM_DEBUGSERVER)
     add_lldb_tool_subdirectory(debugserver)
   endif()

llvm/utils/lit/lit/llvm/subst.py

@@ -44,6 +44,7 @@ class ToolSubst(object):
         verbatim=False,
         unresolved="warn",
         extra_args=None,
+        launcher=None,
     ):
         """Construct a ToolSubst.
 
@@ -79,6 +80,7 @@ class ToolSubst(object):
         """
         self.unresolved = unresolved
         self.extra_args = extra_args
+        self.launcher = launcher
         self.key = key
         self.command = command if command is not None else FindTool(key)
         self.was_resolved = False
@@ -120,6 +122,8 @@ class ToolSubst(object):
         if command_str:
             if self.extra_args:
                 command_str = " ".join([command_str] + self.extra_args)
+            if self.launcher:
+                command_str = self.launcher + " " + command_str
         else:
             if self.unresolved == "warn":
                 # Warn, but still provide a substitution.