drm: add DRM_SET_CLIENT_NAME ioctl

Giving the opportunity to userspace to associate a free-form
name with a drm_file struct is helpful for tracking and debugging.

This is similar to the existing DMA_BUF_SET_NAME ioctl.

Access to client_name is protected by a mutex, and the 'clients' debugfs
file has been updated to print it.

Userspace MR to use this ioctl:
   https://gitlab.freedesktop.org/virgl/virglrenderer/-/merge_requests/1428

If the string passed by userspace contains chars that would mess up output
when it's going to be printed (in dmesg, fdinfo, etc), -EINVAL is returned.

A 0-length string is a valid use, and clears the existing name.

Reviewed-by: Tvrtko Ursulin <tvrtko.ursulin@igalia.com>
Reviewed-by: Dmitry Osipenko <dmitry.osipenko@collabora.com>
Signed-off-by: Pierre-Eric Pelloux-Prayer <pierre-eric.pelloux-prayer@amd.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20241003124506.470931-2-pierre-eric.pelloux-prayer@amd.com
Reviewed-by: Christian König <christian.koenig@amd.com>
Signed-off-by: Christian König <christian.koenig@amd.com>

drivers/gpu/drm/drm_debugfs.c

@@ -78,12 +78,14 @@ static int drm_clients_info(struct seq_file *m, void *data)
 	kuid_t uid;
 
 	seq_printf(m,
-		   "%20s %5s %3s master a %5s %10s\n",
+		   "%20s %5s %3s master a %5s %10s %*s\n",
 		   "command",
 		   "tgid",
 		   "dev",
 		   "uid",
-		   "magic");
+		   "magic",
+		   DRM_CLIENT_NAME_MAX_LEN,
+		   "name");
 
 	/* dev->filelist is sorted youngest first, but we want to present
 	 * oldest first (i.e. kernel, servers, clients), so walk backwardss.
@@ -94,19 +96,23 @@ static int drm_clients_info(struct seq_file *m, void *data)
 		struct task_struct *task;
 		struct pid *pid;
 
+		mutex_lock(&priv->client_name_lock);
 		rcu_read_lock(); /* Locks priv->pid and pid_task()->comm! */
 		pid = rcu_dereference(priv->pid);
 		task = pid_task(pid, PIDTYPE_TGID);
 		uid = task ? __task_cred(task)->euid : GLOBAL_ROOT_UID;
-		seq_printf(m, "%20s %5d %3d   %c    %c %5d %10u\n",
+		seq_printf(m, "%20s %5d %3d   %c    %c %5d %10u %*s\n",
 			   task ? task->comm : "<unknown>",
 			   pid_vnr(pid),
 			   priv->minor->index,
 			   is_current_master ? 'y' : 'n',
 			   priv->authenticated ? 'y' : 'n',
 			   from_kuid_munged(seq_user_ns(m), uid),
-			   priv->magic);
+			   priv->magic,
+			   DRM_CLIENT_NAME_MAX_LEN,
+			   priv->client_name ? priv->client_name : "<unset>");
 		rcu_read_unlock();
+		mutex_unlock(&priv->client_name_lock);
 	}
 	mutex_unlock(&dev->filelist_mutex);
 	return 0;

drivers/gpu/drm/drm_file.c

@@ -157,6 +157,7 @@ struct drm_file *drm_file_alloc(struct drm_minor *minor)
 
 	spin_lock_init(&file->master_lookup_lock);
 	mutex_init(&file->event_read_lock);
+	mutex_init(&file->client_name_lock);
 
 	if (drm_core_check_feature(dev, DRIVER_GEM))
 		drm_gem_open(dev, file);
@@ -258,6 +259,10 @@ void drm_file_free(struct drm_file *file)
 	WARN_ON(!list_empty(&file->event_list));
 
 	put_pid(rcu_access_pointer(file->pid));
+
+	mutex_destroy(&file->client_name_lock);
+	kfree(file->client_name);
+
 	kfree(file);
 }
 

drivers/gpu/drm/drm_ioctl.c

@@ -540,6 +540,55 @@ int drm_version(struct drm_device *dev, void *data,
 	return err;
 }
 
+/*
+ * Check if the passed string contains control char or spaces or
+ * anything that would mess up a formatted output.
+ */
+static int drm_validate_value_string(const char *value, size_t len)
+{
+	int i;
+
+	for (i = 0; i < len; i++) {
+		if (!isascii(value[i]) || !isgraph(value[i]))
+			return -EINVAL;
+	}
+	return 0;
+}
+
+static int drm_set_client_name(struct drm_device *dev, void *data,
+			       struct drm_file *file_priv)
+{
+	struct drm_set_client_name *name = data;
+	size_t len = name->name_len;
+	void __user *user_ptr;
+	char *new_name;
+
+	if (len > DRM_CLIENT_NAME_MAX_LEN) {
+		return -EINVAL;
+	} else if (len) {
+		user_ptr = u64_to_user_ptr(name->name);
+
+		new_name = memdup_user_nul(user_ptr, len);
+		if (IS_ERR(new_name))
+			return PTR_ERR(new_name);
+
+		if (strlen(new_name) != len ||
+		    drm_validate_value_string(new_name, len) < 0) {
+			kfree(new_name);
+			return -EINVAL;
+		}
+	} else {
+		new_name = NULL;
+	}
+
+	mutex_lock(&file_priv->client_name_lock);
+	kfree(file_priv->client_name);
+	file_priv->client_name = new_name;
+	mutex_unlock(&file_priv->client_name_lock);
+
+	return 0;
+}
+
 static int drm_ioctl_permit(u32 flags, struct drm_file *file_priv)
 {
 	/* ROOT_ONLY is only for CAP_SYS_ADMIN */
@@ -610,6 +659,8 @@ static const struct drm_ioctl_desc drm_ioctls[] = {
 	DRM_IOCTL_DEF(DRM_IOCTL_PRIME_HANDLE_TO_FD, drm_prime_handle_to_fd_ioctl, DRM_RENDER_ALLOW),
 	DRM_IOCTL_DEF(DRM_IOCTL_PRIME_FD_TO_HANDLE, drm_prime_fd_to_handle_ioctl, DRM_RENDER_ALLOW),
 
+	DRM_IOCTL_DEF(DRM_IOCTL_SET_CLIENT_NAME, drm_set_client_name, DRM_RENDER_ALLOW),
+
 	DRM_IOCTL_DEF(DRM_IOCTL_MODE_GETPLANERESOURCES, drm_mode_getplane_res, 0),
 	DRM_IOCTL_DEF(DRM_IOCTL_MODE_GETCRTC, drm_mode_getcrtc, 0),
 	DRM_IOCTL_DEF(DRM_IOCTL_MODE_SETCRTC, drm_mode_setcrtc, DRM_MASTER),

include/drm/drm_file.h

@@ -388,6 +388,15 @@ struct drm_file {
 	 * Per-file buffer caches used by the PRIME buffer sharing code.
 	 */
 	struct drm_prime_file_private prime;
+
+	/**
+	 * @client_name:
+	 *
+	 * Userspace-provided name; useful for accounting and debugging.
+	 */
+	const char *client_name;
+	/** @name_lock: Protects @client_name. */
+	struct mutex client_name_lock;
 };
 
 /**

include/uapi/drm/drm.h

@@ -1024,6 +1024,13 @@ struct drm_crtc_queue_sequence {
 	__u64 user_data;	/* user data passed to event */
 };
 
+#define DRM_CLIENT_NAME_MAX_LEN		64
+struct drm_set_client_name {
+	__u64 name_len;
+	__u64 name;
+};
+
+
 #if defined(__cplusplus)
 }
 #endif
@@ -1288,6 +1295,16 @@ extern "C" {
  */
 #define DRM_IOCTL_MODE_CLOSEFB		DRM_IOWR(0xD0, struct drm_mode_closefb)
 
+/**
+ * DRM_IOCTL_SET_CLIENT_NAME - Attach a name to a drm_file
+ *
+ * Having a name allows for easier tracking and debugging.
+ * The length of the name (without null ending char) must be
+ * <= DRM_CLIENT_NAME_MAX_LEN.
+ * The call will fail if the name contains whitespaces or non-printable chars.
+ */
+#define DRM_IOCTL_SET_CLIENT_NAME	DRM_IOWR(0xD1, struct drm_set_client_name)
+
 /*
  * Device specific ioctls should only be in their respective headers
  * The device specific ioctl range is from 0x40 to 0x9f.