tests: Add static drm-mock library

Add a tiny library that sabotages errors in drmMode*() API calls. This
will be used to artificially trigger arbitrary errors, e.g. cause the
next commit to fail with EBUSY.

The three mocked methods are added as they will be used in a future
commit.

Part-of: <https://gitlab.gnome.org/GNOME/mutter/-/merge_requests/2854>

4 files changed, 167 insertions, 0 deletions

diff --git a/src/tests/drm-mock/drm-mock.c b/src/tests/drm-mock/drm-mock.c
new file mode 100644
index 000000000..724596189
--- /dev/null
+++ b/src/tests/drm-mock/drm-mock.c
@@ -0,0 +1,108 @@
+/*
+ * Copyright (C) 2022 Red Hat Inc.
+ *
+ * Permission is hereby granted, free of charge, to any person
+ * obtaining a copy of this software and associated documentation
+ * files (the "Software"), to deal in the Software without
+ * restriction, including without limitation the rights to use, copy,
+ * modify, merge, publish, distribute, sublicense, and/or sell copies
+ * of the Software, and to permit persons to whom the Software is
+ * furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be
+ * included in all copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
+ * EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
+ * MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
+ * NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS
+ * BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN
+ * ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN
+ * CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+ * SOFTWARE.
+ *
+ */
+
+#include "drm-mock.h"
+
+#include <dlfcn.h>
+#include <glib.h>
+#include <stdint.h>
+#include <stdio.h>
+#include <xf86drmMode.h>
+
+static GList *queued_errors[DRM_MOCK_N_CALLS];
+
+static int
+maybe_mock_error (DrmMockCall call)
+{
+  if (queued_errors[call])
+    {
+      int error_number =
+        GPOINTER_TO_INT (queued_errors[call]->data);
+
+      queued_errors[call] = g_list_remove_link (queued_errors[call],
+                                                queued_errors[call]);
+
+      errno = error_number;
+      return -error_number;
+    }
+
+  return 0;
+}
+
+#define MOCK_FUNCTION(FunctionName, CALL_TYPE, args_type, args) \
+\
+DRM_MOCK_EXPORT int \
+FunctionName args_type \
+{ \
+  static int (* real_function) args_type; \
+  int ret; \
+  if (G_UNLIKELY (!real_function)) \
+    real_function = dlsym (RTLD_NEXT, #FunctionName); \
+\
+  ret = maybe_mock_error (CALL_TYPE); \
+  if (ret != 0) \
+    return ret; \
+\
+  return real_function args; \
+}
+
+MOCK_FUNCTION (drmModeAtomicCommit,
+               DRM_MOCK_CALL_ATOMIC_COMMIT,
+               (int                  fd,
+                drmModeAtomicReqPtr  req,
+                uint32_t             flags,
+                void                *user_data),
+               (fd, req, flags, user_data))
+
+MOCK_FUNCTION (drmModePageFlip,
+               DRM_MOCK_CALL_PAGE_FLIP,
+               (int       fd,
+                uint32_t  crtc_id,
+                uint32_t  fb_id,
+                uint32_t  flags,
+                void     *user_data),
+               (fd, crtc_id, fb_id, flags, user_data))
+
+MOCK_FUNCTION (drmModeSetCrtc,
+               DRM_MOCK_CALL_SET_CRTC,
+               (int                 fd,
+                uint32_t            crtc_id,
+                uint32_t            fb_id,
+                uint32_t            x,
+                uint32_t            y,
+                uint32_t           *connectors,
+                int                 count,
+                drmModeModeInfoPtr  mode),
+               (fd, crtc_id, fb_id, x, y, connectors, count, mode))
+
+void
+drm_mock_queue_error (DrmMockCall call,
+                      int         error_number)
+{
+  g_return_if_fail (call < DRM_MOCK_N_CALLS);
+
+  queued_errors[call] = g_list_append (queued_errors[call],
+                                       GINT_TO_POINTER (error_number));
+}
diff --git a/src/tests/drm-mock/drm-mock.h b/src/tests/drm-mock/drm-mock.h
new file mode 100644
index 000000000..ab0838c93
--- /dev/null
+++ b/src/tests/drm-mock/drm-mock.h
@@ -0,0 +1,44 @@
+/*
+ * Copyright (C) 2022 Red Hat Inc.
+ *
+ * Permission is hereby granted, free of charge, to any person
+ * obtaining a copy of this software and associated documentation
+ * files (the "Software"), to deal in the Software without
+ * restriction, including without limitation the rights to use, copy,
+ * modify, merge, publish, distribute, sublicense, and/or sell copies
+ * of the Software, and to permit persons to whom the Software is
+ * furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be
+ * included in all copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
+ * EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
+ * MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
+ * NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS
+ * BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN
+ * ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN
+ * CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+ * SOFTWARE.
+ *
+ */
+
+#ifndef DRM_MOCK_H
+#define DRM_MOCK_H
+
+#define DRM_MOCK_EXPORT __attribute__((visibility("default"))) extern
+
+typedef enum _DrmMockCall
+{
+  DRM_MOCK_CALL_ATOMIC_COMMIT,
+  DRM_MOCK_CALL_PAGE_FLIP,
+  DRM_MOCK_CALL_SET_CRTC,
+
+  DRM_MOCK_N_CALLS
+} DrmMockCall;
+
+DRM_MOCK_EXPORT
+void drm_mock_queue_error (DrmMockCall call,
+                           int         error_number);
+
+#endif /* DRM_MOCK_H */
diff --git a/src/tests/drm-mock/meson.build b/src/tests/drm-mock/meson.build
new file mode 100644
index 000000000..f3fe22a2d
--- /dev/null
+++ b/src/tests/drm-mock/meson.build
@@ -0,0 +1,14 @@
+drm_mock = shared_library('drm-mock',
+  sources: [
+    'drm-mock.c',
+  ],
+  dependencies: [
+    glib_dep,
+    libdrm_dep,
+  ],
+  install: false,
+)
+
+drm_mock_dep = declare_dependency(
+  link_with: drm_mock,
+)
diff --git a/src/tests/meson.build b/src/tests/meson.build
index 93dd7b309..25d78eaa1 100644
--- a/src/tests/meson.build
+++ b/src/tests/meson.build
@@ -124,6 +124,7 @@ if have_clutter_tests
 endif
 
 subdir('protocol')
+subdir('drm-mock')
 subdir('wayland-test-clients')
 
 if have_installed_tests