Commit b7dab24b authored by Philipp Stephani's avatar Philipp Stephani
Browse files

Module assertions: check for garbage collections

It's technically possible to write a user pointer finalizer that calls
into Emacs module functions.  This would be disastrous because it
would allow arbitrary Lisp code to run during garbage collection.
Therefore extend the module assertions to check for this case.

* src/emacs-module.c (module_assert_thread): Also check whether a
garbage collection is in progress.

* test/data/emacs-module/mod-test.c (invalid_finalizer)
(Fmod_test_invalid_finalizer): New test module functions.
(emacs_module_init): Register new test function.

* test/src/emacs-module-tests.el (module--test-assertion)
(module--with-temp-directory): New helper macros.
(module--test-assertions--load-non-live-object): Rename existing
unit test, use helper macros.
(module--test-assertions--call-emacs-from-gc): New unit test.
parent a87d767c
......@@ -817,9 +817,11 @@ in_current_thread (void)
static void
module_assert_thread (void)
if (! module_assertions || in_current_thread ())
if (! module_assertions || (in_current_thread () && ! gc_in_progress))
module_abort ("Module function called from outside the current Lisp thread");
module_abort (gc_in_progress ?
"Module function called during garbage collection" :
"Module function called from outside the current Lisp thread");
static void
......@@ -235,6 +235,27 @@ Fmod_test_invalid_load (emacs_env *env, ptrdiff_t nargs, emacs_value *args,
return invalid_stored_value;
/* An invalid finalizer: Finalizers are run during garbage collection,
where Lisp code can’t be executed. -module-assertions tests for
this case. */
static emacs_env *current_env;
static void
invalid_finalizer (void *ptr)
current_env->intern (current_env, "nil");
static emacs_value
Fmod_test_invalid_finalizer (emacs_env *env, ptrdiff_t nargs, emacs_value *args,
void *data)
current_env = env;
env->make_user_ptr (env, invalid_finalizer, NULL);
return env->funcall (env, env->intern (env, "garbage-collect"), 0, NULL);
/* Lisp utilities for easier readability (simple wrappers). */
......@@ -300,6 +321,8 @@ emacs_module_init (struct emacs_runtime *ert)
DEFUN ("mod-test-vector-eq", Fmod_test_vector_eq, 2, 2, NULL, NULL);
DEFUN ("mod-test-invalid-store", Fmod_test_invalid_store, 0, 0, NULL, NULL);
DEFUN ("mod-test-invalid-load", Fmod_test_invalid_load, 0, 0, NULL, NULL);
DEFUN ("mod-test-invalid-finalizer", Fmod_test_invalid_finalizer, 0, 0,
#undef DEFUN
......@@ -182,37 +182,66 @@ changes."
(should (equal (help-function-arglist #'mod-test-sum)
'(arg1 arg2))))
(ert-deftest module--test-assertions ()
"Check that -module-assertions work."
(defmacro module--with-temp-directory (name &rest body)
"Bind NAME to the name of a temporary directory and evaluate BODY.
NAME must be a symbol. Delete the temporary directory after BODY
exits normally or non-locally. NAME will be bound to the
directory name (not the directory file name) of the temporary
(declare (indent 1))
(cl-check-type name symbol)
`(let ((,name (file-name-as-directory
(make-temp-file "emacs-module-test" :directory))))
(progn ,@body)
(delete-directory ,name :recursive))))
(defmacro module--test-assertion (pattern &rest body)
"Test that PATTERN matches the assertion triggered by BODY.
Run Emacs as a subprocess, load the test module `mod-test-file',
and evaluate BODY. Verify that Emacs aborts and prints a module
assertion message that matches PATTERN. PATTERN is evaluated and
must evaluate to a regular expression string."
(declare (indent 1))
;; To contain any core dumps.
`(module--with-temp-directory tempdir
(let* ((default-directory tempdir)
(status (call-process mod-test-emacs nil t nil
"-batch" "-Q" "-module-assertions" "-eval"
(require 'mod-test ,mod-test-file)
(should (stringp status))
;; eg "Aborted" or "Abort trap: 6"
(should (string-prefix-p "Abort" status))
(search-backward "Emacs module assertion: ")
(goto-char (match-end 0))
(should (string-match-p ,pattern
(point) (point-max))))))))
(ert-deftest module--test-assertions--load-non-live-object ()
"Check that -module-assertions verify that non-live objects
aren’t accessed."
(skip-unless (file-executable-p mod-test-emacs))
;; This doesn’t yet cause undefined behavior.
(should (eq (mod-test-invalid-store) 123))
;; To contain any core dumps.
(let ((tempdir (make-temp-file "emacs-module-test" t)))
(should (string-match-p
"Abort" ; eg "Aborted" or "Abort trap: 6"
(let ((default-directory tempdir))
(call-process mod-test-emacs nil t nil
"-batch" "-Q" "-module-assertions" "-eval"
(require 'mod-test ,mod-test-file)
;; Storing and reloading a local
;; value causes undefined behavior,
;; which should be detected by the
;; module assertions.
(search-backward "Emacs module assertion:")
(should (string-match-p (rx bos "Emacs module assertion: "
"Emacs value not found in "
(+ digit) " values of "
(+ digit) " environments" eos)
(delete-directory tempdir t))))
(module--test-assertion (rx "Emacs value not found in "
(+ digit) " values of "
(+ digit) " environments\n" eos)
;; Storing and reloading a local value causes undefined behavior,
;; which should be detected by the module assertions.
(ert-deftest module--test-assertions--call-emacs-from-gc ()
"Check that -module-assertions prevents calling Emacs functions
during garbage collection."
(skip-unless (file-executable-p mod-test-emacs))
(rx "Module function called during garbage collection\n" eos)
;;; emacs-module-tests.el ends here
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