include/wrapper/writeback.h

   1 /* SPDX-License-Identifier: (GPL-2.0-only or LGPL-2.1-only)
   2  *
   3  * wrapper/writeback.h
   4  *
   5  * wrapper around global_dirty_limit read. Using KALLSYMS with KALLSYMS_ALL
   6  * to get its address when available, else we need to have a kernel that
   7  * exports this variable to GPL modules.
   8  *
   9  * Copyright (C) 2013 Mentor Graphics Corp.
  10  */
  11
  12 #ifndef _LTTNG_WRAPPER_WRITEBACK_H
  13 #define _LTTNG_WRAPPER_WRITEBACK_H
  14
  15 #include <lttng/kernel-version.h>
  16
  17 #ifdef CONFIG_KALLSYMS_ALL
  18 #include <linux/kallsyms.h>
  19 #include <wrapper/kallsyms.h>
  20
  21
  22
  23 #if LINUX_VERSION_CODE >= KERNEL_VERSION(4,2,0)
  24
  25 static struct wb_domain *global_wb_domain_sym;
  26
  27 static inline
  28 unsigned long wrapper_global_dirty_limit(void)
  29 {
  30         if (!global_wb_domain_sym)
  31                 global_wb_domain_sym =
  32                         (void *) kallsyms_lookup_dataptr("global_wb_domain");
  33         if (global_wb_domain_sym) {
  34                 return global_wb_domain_sym->dirty_limit;
  35         } else {
  36                 printk_once(KERN_WARNING "LTTng: global_wb_domain symbol lookup failed.\n");
  37                 return 0;
  38         }
  39 }
  40
  41 /*
  42  * Canary function to check for 'global_wb_domain' at compile time.
  43  *
  44  * From 'include/linux/writeback.h':
  45  *
  46  *   extern struct wb_domain global_wb_domain;
  47  */
  48 static inline
  49 unsigned long __canary__global_wb_domain(void)
  50 {
  51         return global_wb_domain.dirty_limit;
  52 }
  53
  54 #elif LINUX_VERSION_CODE >= KERNEL_VERSION(3,1,0)
  55
  56 static unsigned long *global_dirty_limit_sym;
  57
  58 static inline
  59 unsigned long wrapper_global_dirty_limit(void)
  60 {
  61         if (!global_dirty_limit_sym)
  62                 global_dirty_limit_sym =
  63                         (void *) kallsyms_lookup_dataptr("global_dirty_limit");
  64         if (global_dirty_limit_sym) {
  65                 return *global_dirty_limit_sym;
  66         } else {
  67                 printk_once(KERN_WARNING "LTTng: global_dirty_limit symbol lookup failed.\n");
  68                 return 0;
  69         }
  70 }
  71
  72 /*
  73  * Canary function to check for 'global_dirty_limit' at compile time.
  74  *
  75  * From 'include/linux/writeback.h':
  76  *
  77  *   extern unsigned long global_dirty_limit;
  78  */
  79 static inline
  80 unsigned long __canary__global_dirty_limit(void)
  81 {
  82         return global_dirty_limit;
  83 }
  84
  85 #endif
  86
  87 #else /* CONFIG_KALLSYMS_ALL */
  88
  89 #include <linux/writeback.h>
  90
  91 #if LINUX_VERSION_CODE >= KERNEL_VERSION(3,1,0)
  92 static inline
  93 unsigned long wrapper_global_dirty_limit(void)
  94 {
  95         return global_dirty_limit;
  96 }
  97 #endif
  98
  99 #endif
 100
 101 #endif /* _LTTNG_WRAPPER_WRITEBACK_H */