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 #ifdef CONFIG_KALLSYMS_ALL
  16
  17 #include <linux/kallsyms.h>
  18 #include <wrapper/kallsyms.h>
  19
  20 static struct wb_domain *global_wb_domain_sym;
  21
  22 static inline
  23 unsigned long wrapper_global_dirty_limit(void)
  24 {
  25         if (!global_wb_domain_sym)
  26                 global_wb_domain_sym =
  27                         (void *) kallsyms_lookup_dataptr("global_wb_domain");
  28         if (global_wb_domain_sym) {
  29                 return global_wb_domain_sym->dirty_limit;
  30         } else {
  31                 printk_once(KERN_WARNING "LTTng: global_wb_domain symbol lookup failed.\n");
  32                 return 0;
  33         }
  34 }
  35
  36 /*
  37  * Canary function to check for 'global_wb_domain' at compile time.
  38  *
  39  * From 'include/linux/writeback.h':
  40  *
  41  *   extern struct wb_domain global_wb_domain;
  42  */
  43 static inline
  44 unsigned long __canary__global_wb_domain(void)
  45 {
  46         return global_wb_domain.dirty_limit;
  47 }
  48
  49 #else /* CONFIG_KALLSYMS_ALL */
  50
  51 #include <linux/writeback.h>
  52
  53 static inline
  54 unsigned long wrapper_global_dirty_limit(void)
  55 {
  56         return global_dirty_limit;
  57 }
  58
  59 #endif /* CONFIG_KALLSYMS_ALL */
  60
  61 #endif /* _LTTNG_WRAPPER_WRITEBACK_H */