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.

Change-Id: If6e8797049642ab382d5699660ee1dd734e92c90
Signed-off-by: Michael Jeanson <mjeanson@efficios.com>
Signed-off-by: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>

diff --git a/include/wrapper/genhd.h b/include/wrapper/genhd.h
index 689803881dbb0f9a950c651d48aa4b9a11e83564..c28a52e343dfe730d1a98ecc2395080c04cb1910 100644 (file)
--- a/include/wrapper/genhd.h
+++ b/include/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 */

diff --git a/src/Kbuild b/src/Kbuild
index 616c1ddee1e0572f2669e2557bc2f2ee5b8a288f..e7593fd8db10d08c31d6e7675739f6680388730a 100644 (file)
--- a/src/Kbuild
+++ b/src/Kbuild
@@ -65,6 +65,7 @@ lttng-wrapper-objs := wrapper/page_alloc.o \
                       wrapper/kallsyms.o \
                       wrapper/irqdesc.o \
                       wrapper/fdtable.o \
+                      wrapper/genhd.o \
                       lttng-wrapper-impl.o
 
 ifneq ($(CONFIG_HAVE_SYSCALL_TRACEPOINTS),)

diff --git a/src/lttng-statedump-impl.c b/src/lttng-statedump-impl.c
index b3453bf5a8f21891c5ba4b75bd271317c96d3af4..846706e33a691d4af483a220411d701969013054 100644 (file)
--- a/src/lttng-statedump-impl.c
+++ b/src/lttng-statedump-impl.c
@@ -256,13 +256,17 @@ 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))) {
@@ -278,22 +282,32 @@ 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 (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