[Mesa-dev] [PATCH] st/dri: implement the __DRI_DRIVER_VTABLE extension

[Emil Velikov]

From: Emil Velikov <emil.velikov at collabora.com>

As the comment above globalDriverAPI (in dri_util.c) says, if the loader
is unaware of createNewScreen2 there is a race condition.

In which globalDriverAPI, will be set in the driver driDriverGetExtensions*
function and used in createNewScreen(). If we call another drivers'
driDriverGetExtensions, the createNewScreen will use the latter's API
instead of the former.

To make it more convoluting, the driver _must_ also expose
__DRI_DRIVER_VTABLE, as that one exposes the correct API.

The race also occurs, for loaders which use the pre megadrivers
driDriverGetExtensions entrypoint.

Cc: mesa-stable at lists.freedesktop.org
Signed-off-by: Emil Velikov <emil.velikov at collabora.com>
---
 src/gallium/state_trackers/dri/dri2.c       | 21 +++++++++++++++++++++
 src/gallium/state_trackers/dri/dri_screen.h |  1 +
 src/gallium/state_trackers/dri/drisw.c      |  6 ++++++
 src/gallium/targets/dri/target.c            |  2 +-
 4 files changed, 29 insertions(+), 1 deletion(-)

diff --git a/src/gallium/state_trackers/dri/dri2.c b/src/gallium/state_trackers/dri/dri2.c
index 3cbca4e5dc3..b21e6815796 100644
--- a/src/gallium/state_trackers/dri/dri2.c
+++ b/src/gallium/state_trackers/dri/dri2.c
@@ -2318,11 +2318,32 @@ const struct __DriverAPIRec dri_kms_driver_api = {
    .ReleaseBuffer  = dri2_release_buffer,
 };
 
+static const struct __DRIDriverVtableExtensionRec gallium_drm_vtable = {
+   .base = { __DRI_DRIVER_VTABLE, 1 },
+   .vtable = &galliumdrm_driver_api,
+};
+
+static const struct __DRIDriverVtableExtensionRec dri_kms_vtable = {
+   .base = { __DRI_DRIVER_VTABLE, 1 },
+   .vtable = &dri_kms_driver_api,
+};
+
 /* This is the table of extensions that the loader will dlsym() for. */
 const __DRIextension *galliumdrm_driver_extensions[] = {
     &driCoreExtension.base,
     &driImageDriverExtension.base,
     &driDRI2Extension.base,
+    &gallium_drm_vtable.base,
+    &gallium_config_options.base,
+    NULL
+};
+
+/* This is the table of extensions that the loader will dlsym() for. */
+const __DRIextension *dri_kms_driver_extensions[] = {
+    &driCoreExtension.base,
+    &driImageDriverExtension.base,
+    &driDRI2Extension.base,
+    &dri_kms_vtable.base,
     &gallium_config_options.base,
     NULL
 };
diff --git a/src/gallium/state_trackers/dri/dri_screen.h b/src/gallium/state_trackers/dri/dri_screen.h
index 8d2d9c02892..fde3b4088a7 100644
--- a/src/gallium/state_trackers/dri/dri_screen.h
+++ b/src/gallium/state_trackers/dri/dri_screen.h
@@ -147,6 +147,7 @@ void
 dri_destroy_screen(__DRIscreen * sPriv);
 
 extern const struct __DriverAPIRec dri_kms_driver_api;
+extern const __DRIextension *dri_kms_driver_extensions[];
 
 extern const struct __DriverAPIRec galliumdrm_driver_api;
 extern const __DRIextension *galliumdrm_driver_extensions[];
diff --git a/src/gallium/state_trackers/dri/drisw.c b/src/gallium/state_trackers/dri/drisw.c
index 1fba71bdd97..76a06b36664 100644
--- a/src/gallium/state_trackers/dri/drisw.c
+++ b/src/gallium/state_trackers/dri/drisw.c
@@ -513,11 +513,17 @@ const struct __DriverAPIRec galliumsw_driver_api = {
    .CopySubBuffer = drisw_copy_sub_buffer,
 };
 
+static const struct __DRIDriverVtableExtensionRec galliumsw_vtable = {
+   .base = { __DRI_DRIVER_VTABLE, 1 },
+   .vtable = &galliumsw_driver_api,
+};
+
 /* This is the table of extensions that the loader will dlsym() for. */
 const __DRIextension *galliumsw_driver_extensions[] = {
     &driCoreExtension.base,
     &driSWRastExtension.base,
     &driCopySubBufferExtension.base,
+    &galliumsw_vtable.base,
     &gallium_config_options.base,
     NULL
 };
diff --git a/src/gallium/targets/dri/target.c b/src/gallium/targets/dri/target.c
index 835d125f21e..e943cae6a16 100644
--- a/src/gallium/targets/dri/target.c
+++ b/src/gallium/targets/dri/target.c
@@ -28,7 +28,7 @@ const __DRIextension **__driDriverGetExtensions_kms_swrast(void);
 PUBLIC const __DRIextension **__driDriverGetExtensions_kms_swrast(void)
 {
    globalDriverAPI = &dri_kms_driver_api;
-   return galliumdrm_driver_extensions;
+   return dri_kms_driver_extensions;
 }
 
 #endif
-- 
2.18.0