path: root/meta/recipes-kernel/lttng/lttng-modules/0005-fix-block-add-a-disk_uevent-helper-v5.12.patch

From 17cd2dc91cb82ed342b0da699f2b1a70c1bf6a03 Mon Sep 17 00:00:00 2001
From: Michael Jeanson <mjeanson@efficios.com>
Date: Mon, 15 Mar 2021 14:54:02 -0400
Subject: [PATCH 2/4] fix: block: add a disk_uevent helper (v5.12)

See upstream commit:

  commit bc359d03c7ec1bf3b86d03bafaf6bbb21e6414fd
  Author: Christoph Hellwig <hch@lst.de>
  Date:   Sun Jan 24 11:02:39 2021 +0100

    block: add a disk_uevent helper

    Add a helper to call kobject_uevent for the disk and all partitions, and
    unexport the disk_part_iter_* helpers that are now only used in the core
    block code.

Upstream-status: Backport [2.12.6]

Change-Id: If6e8797049642ab382d5699660ee1dd734e92c90
Signed-off-by: Michael Jeanson <mjeanson@efficios.com>
Signed-off-by: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
---
 Makefile               |   1 +
 lttng-statedump-impl.c |  34 +++++++++----
 src/wrapper/genhd.c    | 111 +++++++++++++++++++++++++++++++++++++++++
 wrapper/genhd.h        |  62 +++++++++++++++++++++++
 4 files changed, 198 insertions(+), 10 deletions(-)
 create mode 100644 src/wrapper/genhd.c

diff --git a/Makefile b/Makefile
index a9aff3f1..34043cfb 100644
--- a/Makefile
+++ b/Makefile
@@ -80,6 +80,7 @@ ifneq ($(KERNELRELEASE),)
                         wrapper/kallsyms.o \
                         wrapper/irqdesc.o \
                         wrapper/fdtable.o \
+                        wrapper/genhd.o \
                         lttng-wrapper-impl.o
 
   ifneq ($(CONFIG_HAVE_SYSCALL_TRACEPOINTS),)
diff --git a/lttng-statedump-impl.c b/lttng-statedump-impl.c
index 60b937c9..5511c7e8 100644
--- a/lttng-statedump-impl.c
+++ b/lttng-statedump-impl.c
@@ -250,13 +250,17 @@ int lttng_enumerate_block_devices(struct lttng_session *session)
 	struct device_type *ptr_disk_type;
 	struct class_dev_iter iter;
 	struct device *dev;
+	int ret = 0;
 
 	ptr_block_class = wrapper_get_block_class();
-	if (!ptr_block_class)
-		return -ENOSYS;
+	if (!ptr_block_class) {
+		ret = -ENOSYS;
+		goto end;
+	}
 	ptr_disk_type = wrapper_get_disk_type();
 	if (!ptr_disk_type) {
-		return -ENOSYS;
+		ret = -ENOSYS;
+		goto end;
 	}
 	class_dev_iter_init(&iter, ptr_block_class, NULL, ptr_disk_type);
 	while ((dev = class_dev_iter_next(&iter))) {
@@ -272,22 +276,32 @@ int lttng_enumerate_block_devices(struct lttng_session *session)
 		    (disk->flags & GENHD_FL_SUPPRESS_PARTITION_INFO))
 			continue;
 
-		disk_part_iter_init(&piter, disk, DISK_PITER_INCL_PART0);
-		while ((part = disk_part_iter_next(&piter))) {
+		/*
+		 * The original 'disk_part_iter_init' returns void, but our
+		 * wrapper can fail to lookup the original symbol.
+		 */
+		if (wrapper_disk_part_iter_init(&piter, disk, DISK_PITER_INCL_PART0) < 0) {
+			ret = -ENOSYS;
+			goto iter_exit;
+		}
+
+		while ((part = wrapper_disk_part_iter_next(&piter))) {
 			char name_buf[BDEVNAME_SIZE];
 
 			if (lttng_get_part_name(disk, part, name_buf) == -ENOSYS) {
-				disk_part_iter_exit(&piter);
-				class_dev_iter_exit(&iter);
-				return -ENOSYS;
+				wrapper_disk_part_iter_exit(&piter);
+				ret = -ENOSYS;
+				goto iter_exit;
 			}
 			trace_lttng_statedump_block_device(session,
 					lttng_get_part_devt(part), name_buf);
 		}
-		disk_part_iter_exit(&piter);
+		wrapper_disk_part_iter_exit(&piter);
 	}
+iter_exit:
 	class_dev_iter_exit(&iter);
-	return 0;
+end:
+	return ret;
 }
 
 #ifdef CONFIG_INET
diff --git a/src/wrapper/genhd.c b/src/wrapper/genhd.c
new file mode 100644
index 00000000..a5a6c410
--- /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
diff --git a/wrapper/genhd.h b/wrapper/genhd.h
index 98feb57b..6bae239d 100644
--- a/wrapper/genhd.h
+++ b/wrapper/genhd.h
@@ -13,6 +13,13 @@
 #define _LTTNG_WRAPPER_GENHD_H
 
 #include <linux/genhd.h>
+#include <lttng/kernel-version.h>
+
+#if (LTTNG_LINUX_VERSION_CODE >= LTTNG_KERNEL_VERSION(5,11,0))
+#define LTTNG_DISK_PART_TYPE struct block_device
+#else
+#define LTTNG_DISK_PART_TYPE struct hd_struct
+#endif
 
 #ifdef CONFIG_KALLSYMS_ALL
 
@@ -94,4 +101,59 @@ struct device_type *wrapper_get_disk_type(void)
 
 #endif
 
+/*
+ * 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);
+LTTNG_DISK_PART_TYPE *wrapper_disk_part_iter_next(struct disk_part_iter *piter);
+void wrapper_disk_part_iter_exit(struct disk_part_iter *piter);
+
+/*
+ * Canary function to check for 'disk_part_iter_init()' at compile time.
+ *
+ * From 'include/linux/genhd.h':
+ *
+ *   extern void disk_part_iter_init(struct disk_part_iter *piter,
+ *                                   struct gendisk *disk, unsigned int flags);
+ *
+ */
+static inline
+void __canary__disk_part_iter_init(struct disk_part_iter *piter, struct gendisk *disk,
+		unsigned int flags)
+{
+	disk_part_iter_init(piter, disk, flags);
+}
+
+/*
+ * Canary function to check for 'disk_part_iter_next()' at compile time.
+ *
+ * From 'include/linux/genhd.h':
+ *
+ *   struct block_device *disk_part_iter_next(struct disk_part_iter *piter);
+ *
+ */
+static inline
+LTTNG_DISK_PART_TYPE *__canary__disk_part_iter_next(struct disk_part_iter *piter)
+{
+	return disk_part_iter_next(piter);
+}
+
+/*
+ * Canary function to check for 'disk_part_iter_exit()' at compile time.
+ *
+ * From 'include/linux/genhd.h':
+ *
+ *   extern void disk_part_iter_exit(struct disk_part_iter *piter);
+ *
+ */
+static inline
+void __canary__disk_part_iter_exit(struct disk_part_iter *piter)
+{
+	return disk_part_iter_exit(piter);
+}
+
 #endif /* _LTTNG_WRAPPER_GENHD_H */
-- 
2.25.1