src/wrapper/genhd.c

   1 /* SPDX-License-Identifier: (GPL-2.0-only OR LGPL-2.1-only)
   2  *
   3  * wrapper/genhd.c
   4  *
   5  * Wrapper around disk_part_iter_(init|next|exit). Using KALLSYMS to get the
   6  * addresses when available, else we need to have a kernel that exports this
   7  * function to GPL modules. This export was removed in 5.12.
   8  *
   9  * Copyright (C) 2021 Michael Jeanson <mjeanson@efficios.com>
  10  */
  11
  12 #include <lttng/kernel-version.h>
  13 #include <linux/module.h>
  14 #include <wrapper/genhd.h>
  15
  16 #if (defined(CONFIG_KALLSYMS) && \
  17         (LTTNG_LINUX_VERSION_CODE >= LTTNG_KERNEL_VERSION(5,12,0)))
  18
  19 #include <wrapper/kallsyms.h>
  20
  21 static
  22 void (*disk_part_iter_init_sym)(struct disk_part_iter *piter, struct gendisk *disk,
  23                         unsigned int flags);
  24
  25 static
  26 LTTNG_DISK_PART_TYPE *(*disk_part_iter_next_sym)(struct disk_part_iter *piter);
  27
  28 static
  29 void (*disk_part_iter_exit_sym)(struct disk_part_iter *piter);
  30
  31 /*
  32  * This wrapper has an 'int' return type instead of the original 'void', to be
  33  * able to report the symbol lookup failure to the caller.
  34  *
  35  * Return 0 on success, -1 on error.
  36  */
  37 int wrapper_disk_part_iter_init(struct disk_part_iter *piter, struct gendisk *disk,
  38                           unsigned int flags)
  39 {
  40         if (!disk_part_iter_init_sym)
  41                 disk_part_iter_init_sym = (void *) kallsyms_lookup_funcptr("disk_part_iter_init");
  42
  43         if (disk_part_iter_init_sym) {
  44                 disk_part_iter_init_sym(piter, disk, flags);
  45         } else {
  46                 printk_once(KERN_WARNING "LTTng: disk_part_iter_init symbol lookup failed.\n");
  47                 return -1;
  48         }
  49         return 0;
  50 }
  51 EXPORT_SYMBOL_GPL(wrapper_disk_part_iter_init);
  52
  53 LTTNG_DISK_PART_TYPE *wrapper_disk_part_iter_next(struct disk_part_iter *piter)
  54 {
  55         if (!disk_part_iter_next_sym)
  56                 disk_part_iter_next_sym = (void *) kallsyms_lookup_funcptr("disk_part_iter_next");
  57
  58         if (disk_part_iter_next_sym) {
  59                 return disk_part_iter_next_sym(piter);
  60         } else {
  61                 printk_once(KERN_WARNING "LTTng: disk_part_iter_next symbol lookup failed.\n");
  62                 return NULL;
  63         }
  64 }
  65 EXPORT_SYMBOL_GPL(wrapper_disk_part_iter_next);
  66
  67 /*
  68  * We don't return an error on symbol lookup failure here because there is
  69  * nothing the caller can do to cleanup the iterator.
  70  */
  71 void wrapper_disk_part_iter_exit(struct disk_part_iter *piter)
  72 {
  73         if (!disk_part_iter_exit_sym)
  74                 disk_part_iter_exit_sym = (void *) kallsyms_lookup_funcptr("disk_part_iter_exit");
  75
  76         if (disk_part_iter_exit_sym) {
  77                 disk_part_iter_exit_sym(piter);
  78         } else {
  79                 printk_once(KERN_WARNING "LTTng: disk_part_iter_exit symbol lookup failed.\n");
  80         }
  81 }
  82 EXPORT_SYMBOL_GPL(wrapper_disk_part_iter_exit);
  83
  84 #else
  85
  86 /*
  87  * This wrapper has an 'int' return type instead of the original 'void', so the
  88  * kallsyms variant can report the symbol lookup failure to the caller.
  89  *
  90  * This variant always succeeds and returns 0.
  91  */
  92 int wrapper_disk_part_iter_init(struct disk_part_iter *piter, struct gendisk *disk,
  93                           unsigned int flags)
  94 {
  95         disk_part_iter_init(piter, disk, flags);
  96         return 0;
  97 }
  98 EXPORT_SYMBOL_GPL(wrapper_disk_part_iter_init);
  99
 100 LTTNG_DISK_PART_TYPE *wrapper_disk_part_iter_next(struct disk_part_iter *piter)
 101 {
 102         return disk_part_iter_next(piter);
 103 }
 104 EXPORT_SYMBOL_GPL(wrapper_disk_part_iter_next);
 105
 106 void wrapper_disk_part_iter_exit(struct disk_part_iter *piter)
 107 {
 108         disk_part_iter_exit(piter);
 109 }
 110 EXPORT_SYMBOL_GPL(wrapper_disk_part_iter_exit);
 111 #endif