+/* SPDX-License-Identifier: (GPL-2.0-only or LGPL-2.1-only)
+ *
+ * wrapper/blkdev.h
+ *
+ * wrapper around block layer functions and data structures. Using
+ * KALLSYMS to get its address when available, else we need to have a
+ * kernel that exports this function to GPL modules.
+ *
+ * Copyright (C) 2011-2014 Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
+ */
+
+#ifndef _LTTNG_WRAPPER_BLKDEV_H
+#define _LTTNG_WRAPPER_BLKDEV_H
+
+#if (LTTNG_LINUX_VERSION_CODE >= LTTNG_KERNEL_VERSION(5,18,0))
+#include <linux/blkdev.h>
+#else
+#include <linux/genhd.h>
+#endif
+
+#if (LTTNG_LINUX_VERSION_CODE >= LTTNG_KERNEL_VERSION(5,17,0))
+#define LTTNG_GENHD_FL_HIDDEN GENHD_FL_HIDDEN
+#else
+#define LTTNG_GENHD_FL_HIDDEN GENHD_FL_SUPPRESS_PARTITION_INFO
+#endif
+
+#ifdef CONFIG_KALLSYMS_ALL
+
+#include <linux/kallsyms.h>
+#include <wrapper/kallsyms.h>
+
+static inline
+struct class *wrapper_get_block_class(void)
+{
+ struct class *ptr_block_class;
+
+ ptr_block_class = (struct class *) kallsyms_lookup_dataptr("block_class");
+ if (!ptr_block_class) {
+ printk_once(KERN_WARNING "LTTng: block_class symbol lookup failed.\n");
+ return NULL;
+ }
+ return ptr_block_class;
+}
+
+/*
+ * Canary function to check for 'block_class' at compile time.
+ *
+ * From 'include/linux/blkdev.h':
+ *
+ * extern struct class block_class;
+ */
+static inline
+struct class *__canary__get_block_class(void)
+{
+ return &block_class;
+}
+
+static inline
+struct device_type *wrapper_get_disk_type(void)
+{
+ struct device_type *ptr_disk_type;
+
+ ptr_disk_type = (struct device_type *) kallsyms_lookup_dataptr("disk_type");
+ if (!ptr_disk_type) {
+ printk_once(KERN_WARNING "LTTng: disk_type symbol lookup failed.\n");
+ return NULL;
+ }
+ return ptr_disk_type;
+}
+
+/*
+ * No canary for 'disk_type', it's only defined in 'block/genhd.c'.
+ *
+ * static inline
+ * struct device_type *__canary__get_disk_type(void)
+ * {
+ * return &disk_type;
+ * }
+ */
+
+#else
+
+static inline
+struct class *wrapper_get_block_class(void)
+{
+ /*
+ * Symbol block_class is not exported.
+ * TODO: return &block_class;
+ */
+ /* Feature currently unavailable without KALLSYMS_ALL */
+ return NULL;
+}
+
+static inline
+struct device_type *wrapper_get_disk_type(void)
+{
+ /*
+ * Symbol disk_type is not exported.
+ * TODO: return &disk_type;
+ */
+ /* Feature currently unavailable without KALLSYMS_ALL */
+ return NULL;
+}
+
+#endif
+
+#endif /* _LTTNG_WRAPPER_BLKDEV_H */