include/linux/export.h

   1 #ifndef _LINUX_EXPORT_H
   2 #define _LINUX_EXPORT_H
   3 /*
   4  * Export symbols from the kernel to modules.  Forked from module.h
   5  * to reduce the amount of pointless cruft we feed to gcc when only
   6  * exporting a simple symbol or two.
   7  *
   8  * If you feel the need to add #include <linux/foo.h> to this file
   9  * then you are doing something wrong and should go away silently.
  10  */
  11
  12 /* Some toolchains use a `_' prefix for all user symbols. */
  13 #ifdef CONFIG_SYMBOL_PREFIX
  14 #define MODULE_SYMBOL_PREFIX CONFIG_SYMBOL_PREFIX
  15 #else
  16 #define MODULE_SYMBOL_PREFIX ""
  17 #endif
  18
  19 struct kernel_symbol
  20 {
  21         unsigned long value;
  22         const char *name;
  23 };
  24
  25 #ifdef MODULE
  26 extern struct module __this_module;
  27 #define THIS_MODULE (&__this_module)
  28 #else
  29 #define THIS_MODULE ((struct module *)0)
  30 #endif
  31
  32 #ifdef CONFIG_MODULES
  33
  34 #ifndef __GENKSYMS__
  35 #ifdef CONFIG_MODVERSIONS
  36 /* Mark the CRC weak since genksyms apparently decides not to
  37  * generate a checksums for some symbols */
  38 #define __CRC_SYMBOL(sym, sec)                                  \
  39         extern void *__crc_##sym __attribute__((weak));         \
  40         static const unsigned long __kcrctab_##sym              \
  41         __used                                                  \
  42         __attribute__((section("___kcrctab" sec "+" #sym), unused))     \
  43         = (unsigned long) &__crc_##sym;
  44 #else
  45 #define __CRC_SYMBOL(sym, sec)
  46 #endif
  47
  48 /* For every exported symbol, place a struct in the __ksymtab section */
  49 #define __EXPORT_SYMBOL(sym, sec)                               \
  50         extern typeof(sym) sym;                                 \
  51         __CRC_SYMBOL(sym, sec)                                  \
  52         static const char __kstrtab_##sym[]                     \
  53         __attribute__((section("__ksymtab_strings"), aligned(1))) \
  54         = MODULE_SYMBOL_PREFIX #sym;                            \
  55         static const struct kernel_symbol __ksymtab_##sym       \
  56         __used                                                  \
  57         __attribute__((section("___ksymtab" sec "+" #sym), unused))     \
  58         = { (unsigned long)&sym, __kstrtab_##sym }
  59
  60 #define EXPORT_SYMBOL(sym)                                      \
  61         __EXPORT_SYMBOL(sym, "")
  62
  63 #define EXPORT_SYMBOL_GPL(sym)                                  \
  64         __EXPORT_SYMBOL(sym, "_gpl")
  65
  66 #define EXPORT_SYMBOL_GPL_FUTURE(sym)                           \
  67         __EXPORT_SYMBOL(sym, "_gpl_future")
  68
  69 #ifdef CONFIG_UNUSED_SYMBOLS
  70 #define EXPORT_UNUSED_SYMBOL(sym) __EXPORT_SYMBOL(sym, "_unused")
  71 #define EXPORT_UNUSED_SYMBOL_GPL(sym) __EXPORT_SYMBOL(sym, "_unused_gpl")
  72 #else
  73 #define EXPORT_UNUSED_SYMBOL(sym)
  74 #define EXPORT_UNUSED_SYMBOL_GPL(sym)
  75 #endif
  76
  77 #endif  /* __GENKSYMS__ */
  78
  79 #else /* !CONFIG_MODULES... */
  80
  81 #define EXPORT_SYMBOL(sym)
  82 #define EXPORT_SYMBOL_GPL(sym)
  83 #define EXPORT_SYMBOL_GPL_FUTURE(sym)
  84 #define EXPORT_UNUSED_SYMBOL(sym)
  85 #define EXPORT_UNUSED_SYMBOL_GPL(sym)
  86
  87 #endif /* CONFIG_MODULES */
  88
  89 #endif /* _LINUX_EXPORT_H */