drm/vmwgfx: use core drm to extend/check vmw_execbuf_ioctl

Currently vmw_execbuf_ioctl() open-codes the permission checking, size
extending and copying that is already done in core drm.

Kill all the duplication, adding a few comments for clarity.

Cc: VMware Graphics <linux-graphics-maintainer@vmware.com>
Cc: Thomas Hellstrom <thellstrom@vmware.com>
Cc: Daniel Vetter <daniel@ffwll.ch>
Signed-off-by: Emil Velikov <emil.velikov@collabora.com>
Tested-by: Thomas Hellstrom <thellstrom@vmware.com>
Reviewed-by: Thomas Hellstrom <thellstrom@vmware.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20190522164119.24139-3-emil.l.velikov@gmail.com

drivers/gpu/drm/vmwgfx/vmwgfx_drv.c

@@ -186,7 +186,7 @@ static const struct drm_ioctl_desc vmw_ioctls[] = {
 		      DRM_RENDER_ALLOW),
 	VMW_IOCTL_DEF(VMW_REF_SURFACE, vmw_surface_reference_ioctl,
 		      DRM_AUTH | DRM_RENDER_ALLOW),
-	VMW_IOCTL_DEF(VMW_EXECBUF, NULL, DRM_AUTH |
+	VMW_IOCTL_DEF(VMW_EXECBUF, vmw_execbuf_ioctl, DRM_AUTH |
 		      DRM_RENDER_ALLOW),
 	VMW_IOCTL_DEF(VMW_FENCE_WAIT, vmw_fence_obj_wait_ioctl,
 		      DRM_RENDER_ALLOW),
@@ -1117,15 +1117,7 @@ static long vmw_generic_ioctl(struct file *filp, unsigned int cmd,
 			&vmw_ioctls[nr - DRM_COMMAND_BASE];
 
 		if (nr == DRM_COMMAND_BASE + DRM_VMW_EXECBUF) {
-			ret = (long) drm_ioctl_permit(ioctl->flags, file_priv);
-			if (unlikely(ret != 0))
-				return ret;
-
-			if (unlikely((cmd & (IOC_IN | IOC_OUT)) != IOC_IN))
-				goto out_io_encoding;
-
-			return (long) vmw_execbuf_ioctl(dev, arg, file_priv,
-							_IOC_SIZE(cmd));
+			return ioctl_func(filp, cmd, arg);
 		} else if (nr == DRM_COMMAND_BASE + DRM_VMW_UPDATE_LAYOUT) {
 			if (!drm_is_current_master(file_priv) &&
 			    !capable(CAP_SYS_ADMIN))

drivers/gpu/drm/vmwgfx/vmwgfx_drv.h

@@ -910,8 +910,8 @@ static inline struct page *vmw_piter_page(struct vmw_piter *viter)
  * Command submission - vmwgfx_execbuf.c
  */
 
-extern int vmw_execbuf_ioctl(struct drm_device *dev, unsigned long data,
-			     struct drm_file *file_priv, size_t size);
+extern int vmw_execbuf_ioctl(struct drm_device *dev, void *data,
+			     struct drm_file *file_priv);
 extern int vmw_execbuf_process(struct drm_file *file_priv,
 			       struct vmw_private *dev_priv,
 			       void __user *user_commands,

drivers/gpu/drm/vmwgfx/vmwgfx_execbuf.c

@@ -3995,54 +3995,40 @@ void vmw_execbuf_release_pinned_bo(struct vmw_private *dev_priv)
 	mutex_unlock(&dev_priv->cmdbuf_mutex);
 }
 
-int vmw_execbuf_ioctl(struct drm_device *dev, unsigned long data,
-		      struct drm_file *file_priv, size_t size)
+int vmw_execbuf_ioctl(struct drm_device *dev, void *data,
+		      struct drm_file *file_priv)
 {
 	struct vmw_private *dev_priv = vmw_priv(dev);
-	struct drm_vmw_execbuf_arg arg;
+	struct drm_vmw_execbuf_arg *arg = data;
 	int ret;
-	static const size_t copy_offset[] = {
-		offsetof(struct drm_vmw_execbuf_arg, context_handle),
-		sizeof(struct drm_vmw_execbuf_arg)};
 	struct dma_fence *in_fence = NULL;
 
-	if (unlikely(size < copy_offset[0])) {
-		VMW_DEBUG_USER("Invalid command size, ioctl %d\n",
-			       DRM_VMW_EXECBUF);
-		return -EINVAL;
-	}
-
-	if (copy_from_user(&arg, (void __user *) data, copy_offset[0]) != 0)
-		return -EFAULT;
-
 	/*
 	 * Extend the ioctl argument while maintaining backwards compatibility:
-	 * We take different code paths depending on the value of arg.version.
+	 * We take different code paths depending on the value of arg->version.
+	 *
+	 * Note: The ioctl argument is extended and zeropadded by core DRM.
 	 */
-	if (unlikely(arg.version > DRM_VMW_EXECBUF_VERSION ||
-		     arg.version == 0)) {
+	if (unlikely(arg->version > DRM_VMW_EXECBUF_VERSION ||
+		     arg->version == 0)) {
 		VMW_DEBUG_USER("Incorrect execbuf version.\n");
 		return -EINVAL;
 	}
 
-	if (arg.version > 1 &&
-	    copy_from_user(&arg.context_handle,
-			   (void __user *) (data + copy_offset[0]),
-			   copy_offset[arg.version - 1] - copy_offset[0]) != 0)
-		return -EFAULT;
-
-	switch (arg.version) {
+	switch (arg->version) {
 	case 1:
-		arg.context_handle = (uint32_t) -1;
+		/* For v1 core DRM have extended + zeropadded the data */
+		arg->context_handle = (uint32_t) -1;
 		break;
 	case 2:
 	default:
+		/* For v2 and later core DRM would have correctly copied it */
 		break;
 	}
 
 	/* If imported a fence FD from elsewhere, then wait on it */
-	if (arg.flags & DRM_VMW_EXECBUF_FLAG_IMPORT_FENCE_FD) {
-		in_fence = sync_file_get_fence(arg.imported_fence_fd);
+	if (arg->flags & DRM_VMW_EXECBUF_FLAG_IMPORT_FENCE_FD) {
+		in_fence = sync_file_get_fence(arg->imported_fence_fd);
 
 		if (!in_fence) {
 			VMW_DEBUG_USER("Cannot get imported fence\n");
@@ -4059,11 +4045,11 @@ int vmw_execbuf_ioctl(struct drm_device *dev, unsigned long data,
 		return ret;
 
 	ret = vmw_execbuf_process(file_priv, dev_priv,
-				  (void __user *)(unsigned long)arg.commands,
-				  NULL, arg.command_size, arg.throttle_us,
-				  arg.context_handle,
-				  (void __user *)(unsigned long)arg.fence_rep,
-				  NULL, arg.flags);
+				  (void __user *)(unsigned long)arg->commands,
+				  NULL, arg->command_size, arg->throttle_us,
+				  arg->context_handle,
+				  (void __user *)(unsigned long)arg->fence_rep,
+				  NULL, arg->flags);
 
 	ttm_read_unlock(&dev_priv->reservation_sem);
 	if (unlikely(ret != 0))