include/wrapper/genhd.h

   1 /* SPDX-License-Identifier: (GPL-2.0-only or LGPL-2.1-only)
   2  *
   3  * wrapper/genhd.h
   4  *
   5  * wrapper around block layer functions and data structures. Using
   6  * KALLSYMS to get its address when available, else we need to have a
   7  * kernel that exports this function to GPL modules.
   8  *
   9  * Copyright (C) 2011-2014 Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
  10  */
  11
  12 #ifndef _LTTNG_WRAPPER_GENHD_H
  13 #define _LTTNG_WRAPPER_GENHD_H
  14
  15 #include <linux/genhd.h>
  16
  17 #ifdef CONFIG_KALLSYMS_ALL
  18
  19 #include <linux/kallsyms.h>
  20 #include <wrapper/kallsyms.h>
  21
  22 static inline
  23 struct class *wrapper_get_block_class(void)
  24 {
  25         struct class *ptr_block_class;
  26
  27         ptr_block_class = (struct class *) kallsyms_lookup_dataptr("block_class");
  28         if (!ptr_block_class) {
  29                 printk_once(KERN_WARNING "LTTng: block_class symbol lookup failed.\n");
  30                 return NULL;
  31         }
  32         return ptr_block_class;
  33 }
  34
  35 /*
  36  * Canary function to check for 'block_class' at compile time.
  37  *
  38  * From 'include/linux/genhd.h':
  39  *
  40  *   extern struct class block_class;
  41  */
  42 static inline
  43 struct class *__canary__get_block_class(void)
  44 {
  45         return &block_class;
  46 }
  47
  48 static inline
  49 struct device_type *wrapper_get_disk_type(void)
  50 {
  51         struct device_type *ptr_disk_type;
  52
  53         ptr_disk_type = (struct device_type *) kallsyms_lookup_dataptr("disk_type");
  54         if (!ptr_disk_type) {
  55                 printk_once(KERN_WARNING "LTTng: disk_type symbol lookup failed.\n");
  56                 return NULL;
  57         }
  58         return ptr_disk_type;
  59 }
  60
  61 /*
  62  * No canary for 'disk_type', it's only defined in 'block/genhd.c'.
  63  *
  64  * static inline
  65  * struct device_type *__canary__get_disk_type(void)
  66  * {
  67  *      return &disk_type;
  68  * }
  69  */
  70
  71 #else
  72
  73 static inline
  74 struct class *wrapper_get_block_class(void)
  75 {
  76         /*
  77          * Symbol block_class is not exported.
  78          * TODO: return &block_class;
  79          */
  80         /* Feature currently unavailable without KALLSYMS_ALL */
  81         return NULL;
  82 }
  83
  84 static inline
  85 struct device_type *wrapper_get_disk_type(void)
  86 {
  87         /*
  88          * Symbol disk_type is not exported.
  89          * TODO: return &disk_type;
  90          */
  91         /* Feature currently unavailable without KALLSYMS_ALL */
  92         return NULL;
  93 }
  94
  95 #endif
  96
  97 #endif /* _LTTNG_WRAPPER_GENHD_H */