include/linux/export.h

   1 #ifndef _LINUX_EXPORT_H
   2 #define _LINUX_EXPORT_H
   3
   4 /*
   5  * Export symbols from the kernel to modules.  Forked from module.h
   6  * to reduce the amount of pointless cruft we feed to gcc when only
   7  * exporting a simple symbol or two.
   8  *
   9  * Try not to add #includes here.  It slows compilation and makes kernel
  10  * hackers place grumpy comments in header files.
  11  */
  12
  13 #define __VMLINUX_SYMBOL(x) x
  14 #define __VMLINUX_SYMBOL_STR(x) #x
  15
  16 /* Indirect, so macros are expanded before pasting. */
  17 #define VMLINUX_SYMBOL(x) __VMLINUX_SYMBOL(x)
  18 #define VMLINUX_SYMBOL_STR(x) __VMLINUX_SYMBOL_STR(x)
  19
  20 #ifndef __ASSEMBLY__
  21 struct kernel_symbol
  22 {
  23         unsigned long value;
  24         const char *name;
  25 };
  26
  27 #ifdef MODULE
  28 extern struct module __this_module;
  29 #define THIS_MODULE (&__this_module)
  30 #else
  31 #define THIS_MODULE ((struct module *)0)
  32 #endif
  33
  34 #ifdef CONFIG_MODULES
  35
  36 #if defined(__KERNEL__) && !defined(__GENKSYMS__)
  37 #ifdef CONFIG_MODVERSIONS
  38 /* Mark the CRC weak since genksyms apparently decides not to
  39  * generate a checksums for some symbols */
  40 #if defined(CONFIG_MODULE_REL_CRCS)
  41 #define __CRC_SYMBOL(sym, sec)                                          \
  42         asm("   .section \"___kcrctab" sec "+" #sym "\", \"a\"  \n"     \
  43             "   .weak   __crc_" #sym "                          \n"     \
  44             "   .long   __crc_" #sym " - .                      \n"     \
  45             "   .previous                                       \n");
  46 #else
  47 #define __CRC_SYMBOL(sym, sec)                                          \
  48         asm("   .section \"___kcrctab" sec "+" #sym "\", \"a\"  \n"     \
  49             "   .weak   __crc_" #sym "                          \n"     \
  50             "   .long   __crc_" #sym "                          \n"     \
  51             "   .previous                                       \n");
  52 #endif
  53 #else
  54 #define __CRC_SYMBOL(sym, sec)
  55 #endif
  56
  57 /* For every exported symbol, place a struct in the __ksymtab section */
  58 #define ___EXPORT_SYMBOL(sym, sec)                                      \
  59         extern typeof(sym) sym;                                         \
  60         __CRC_SYMBOL(sym, sec)                                          \
  61         static const char __kstrtab_##sym[]                             \
  62         __attribute__((section("__ksymtab_strings"), aligned(1)))       \
  63         = #sym;                                                         \
  64         static const struct kernel_symbol __ksymtab_##sym               \
  65         __used                                                          \
  66         __attribute__((section("___ksymtab" sec "+" #sym), used))       \
  67         = { (unsigned long)&sym, __kstrtab_##sym }
  68
  69 #if defined(__KSYM_DEPS__)
  70
  71 /*
  72  * For fine grained build dependencies, we want to tell the build system
  73  * about each possible exported symbol even if they're not actually exported.
  74  * We use a string pattern that is unlikely to be valid code that the build
  75  * system filters out from the preprocessor output (see ksym_dep_filter
  76  * in scripts/Kbuild.include).
  77  */
  78 #define __EXPORT_SYMBOL(sym, sec)       === __KSYM_##sym ===
  79
  80 #elif defined(CONFIG_TRIM_UNUSED_KSYMS)
  81
  82 #include <generated/autoksyms.h>
  83
  84 #define __EXPORT_SYMBOL(sym, sec)                               \
  85         __cond_export_sym(sym, sec, __is_defined(__KSYM_##sym))
  86 #define __cond_export_sym(sym, sec, conf)                       \
  87         ___cond_export_sym(sym, sec, conf)
  88 #define ___cond_export_sym(sym, sec, enabled)                   \
  89         __cond_export_sym_##enabled(sym, sec)
  90 #define __cond_export_sym_1(sym, sec) ___EXPORT_SYMBOL(sym, sec)
  91 #define __cond_export_sym_0(sym, sec) /* nothing */
  92
  93 #else
  94 #define __EXPORT_SYMBOL ___EXPORT_SYMBOL
  95 #endif
  96
  97 #define EXPORT_SYMBOL(sym)                                      \
  98         __EXPORT_SYMBOL(sym, "")
  99
 100 #define EXPORT_SYMBOL_GPL(sym)                                  \
 101         __EXPORT_SYMBOL(sym, "_gpl")
 102
 103 #define EXPORT_SYMBOL_GPL_FUTURE(sym)                           \
 104         __EXPORT_SYMBOL(sym, "_gpl_future")
 105
 106 #ifdef CONFIG_UNUSED_SYMBOLS
 107 #define EXPORT_UNUSED_SYMBOL(sym) __EXPORT_SYMBOL(sym, "_unused")
 108 #define EXPORT_UNUSED_SYMBOL_GPL(sym) __EXPORT_SYMBOL(sym, "_unused_gpl")
 109 #else
 110 #define EXPORT_UNUSED_SYMBOL(sym)
 111 #define EXPORT_UNUSED_SYMBOL_GPL(sym)
 112 #endif
 113
 114 #endif  /* __GENKSYMS__ */
 115
 116 #else /* !CONFIG_MODULES... */
 117
 118 #define EXPORT_SYMBOL(sym)
 119 #define EXPORT_SYMBOL_GPL(sym)
 120 #define EXPORT_SYMBOL_GPL_FUTURE(sym)
 121 #define EXPORT_UNUSED_SYMBOL(sym)
 122 #define EXPORT_UNUSED_SYMBOL_GPL(sym)
 123
 124 #endif /* CONFIG_MODULES */
 125 #endif /* !__ASSEMBLY__ */
 126
 127 #endif /* _LINUX_EXPORT_H */