fix: block: add a disk_uevent helper (v5.12)

[lttng-modules.git] / src / wrapper / genhd.c

diff --git a/src/wrapper/genhd.c b/src/wrapper/genhd.c
new file mode 100644 (file)
index 0000000..a5a6c41
--- /dev/null
+++ b/src/wrapper/genhd.c
@@ -0,0 +1,111 @@
+/* SPDX-License-Identifier: (GPL-2.0-only OR LGPL-2.1-only)
+ *
+ * wrapper/genhd.c
+ *
+ * Wrapper around disk_part_iter_(init|next|exit). Using KALLSYMS to get the
+ * addresses when available, else we need to have a kernel that exports this
+ * function to GPL modules. This export was removed in 5.12.
+ *
+ * Copyright (C) 2021 Michael Jeanson <mjeanson@efficios.com>
+ */
+
+#include <lttng/kernel-version.h>
+#include <linux/module.h>
+#include <wrapper/genhd.h>
+
+#if (defined(CONFIG_KALLSYMS) && \
+       (LTTNG_LINUX_VERSION_CODE >= LTTNG_KERNEL_VERSION(5,12,0)))
+
+#include <wrapper/kallsyms.h>
+
+static
+void (*disk_part_iter_init_sym)(struct disk_part_iter *piter, struct gendisk *disk,
+                       unsigned int flags);
+
+static
+LTTNG_DISK_PART_TYPE *(*disk_part_iter_next_sym)(struct disk_part_iter *piter);
+
+static
+void (*disk_part_iter_exit_sym)(struct disk_part_iter *piter);
+
+/*
+ * This wrapper has an 'int' return type instead of the original 'void', to be
+ * able to report the symbol lookup failure to the caller.
+ *
+ * Return 0 on success, -1 on error.
+ */
+int wrapper_disk_part_iter_init(struct disk_part_iter *piter, struct gendisk *disk,
+                          unsigned int flags)
+{
+       if (!disk_part_iter_init_sym)
+               disk_part_iter_init_sym = (void *) kallsyms_lookup_funcptr("disk_part_iter_init");
+
+       if (disk_part_iter_init_sym) {
+               disk_part_iter_init_sym(piter, disk, flags);
+       } else {
+               printk_once(KERN_WARNING "LTTng: disk_part_iter_init symbol lookup failed.\n");
+               return -1;
+       }
+       return 0;
+}
+EXPORT_SYMBOL_GPL(wrapper_disk_part_iter_init);
+
+LTTNG_DISK_PART_TYPE *wrapper_disk_part_iter_next(struct disk_part_iter *piter)
+{
+       if (!disk_part_iter_next_sym)
+               disk_part_iter_next_sym = (void *) kallsyms_lookup_funcptr("disk_part_iter_next");
+
+       if (disk_part_iter_next_sym) {
+               return disk_part_iter_next_sym(piter);
+       } else {
+               printk_once(KERN_WARNING "LTTng: disk_part_iter_next symbol lookup failed.\n");
+               return NULL;
+       }
+}
+EXPORT_SYMBOL_GPL(wrapper_disk_part_iter_next);
+
+/*
+ * We don't return an error on symbol lookup failure here because there is
+ * nothing the caller can do to cleanup the iterator.
+ */
+void wrapper_disk_part_iter_exit(struct disk_part_iter *piter)
+{
+       if (!disk_part_iter_exit_sym)
+               disk_part_iter_exit_sym = (void *) kallsyms_lookup_funcptr("disk_part_iter_exit");
+
+       if (disk_part_iter_exit_sym) {
+               disk_part_iter_exit_sym(piter);
+       } else {
+               printk_once(KERN_WARNING "LTTng: disk_part_iter_exit symbol lookup failed.\n");
+       }
+}
+EXPORT_SYMBOL_GPL(wrapper_disk_part_iter_exit);
+
+#else
+
+/*
+ * This wrapper has an 'int' return type instead of the original 'void', so the
+ * kallsyms variant can report the symbol lookup failure to the caller.
+ *
+ * This variant always succeeds and returns 0.
+ */
+int wrapper_disk_part_iter_init(struct disk_part_iter *piter, struct gendisk *disk,
+                          unsigned int flags)
+{
+       disk_part_iter_init(piter, disk, flags);
+       return 0;
+}
+EXPORT_SYMBOL_GPL(wrapper_disk_part_iter_init);
+
+LTTNG_DISK_PART_TYPE *wrapper_disk_part_iter_next(struct disk_part_iter *piter)
+{
+       return disk_part_iter_next(piter);
+}
+EXPORT_SYMBOL_GPL(wrapper_disk_part_iter_next);
+
+void wrapper_disk_part_iter_exit(struct disk_part_iter *piter)
+{
+       disk_part_iter_exit(piter);
+}
+EXPORT_SYMBOL_GPL(wrapper_disk_part_iter_exit);
+#endif