LXR linux/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/* Some toolchains use a `_' prefix for all user symbols. */
  14#ifdef CONFIG_HAVE_UNDERSCORE_SYMBOL_PREFIX
  15#define __VMLINUX_SYMBOL(x) _##x
  16#define __VMLINUX_SYMBOL_STR(x) "_" #x
  17#else
  18#define __VMLINUX_SYMBOL(x) x
  19#define __VMLINUX_SYMBOL_STR(x) #x
  20#endif
  21
  22/* Indirect, so macros are expanded before pasting. */
  23#define VMLINUX_SYMBOL(x) __VMLINUX_SYMBOL(x)
  24#define VMLINUX_SYMBOL_STR(x) __VMLINUX_SYMBOL_STR(x)
  25
  26#ifndef __ASSEMBLY__
  27struct kernel_symbol
  28{
  29        unsigned long value;
  30        const char *name;
  31};
  32
  33#ifdef MODULE
  34extern struct module __this_module;
  35#define THIS_MODULE (&__this_module)
  36#else
  37#define THIS_MODULE ((struct module *)0)
  38#endif
  39
  40#ifdef CONFIG_MODULES
  41
  42#if defined(__KERNEL__) && !defined(__GENKSYMS__)
  43#ifdef CONFIG_MODVERSIONS
  44/* Mark the CRC weak since genksyms apparently decides not to
  45 * generate a checksums for some symbols */
  46#if defined(CONFIG_MODULE_REL_CRCS)
  47#define __CRC_SYMBOL(sym, sec)                                          \
  48        asm("   .section \"___kcrctab" sec "+" #sym "\", \"a\"  \n"     \
  49            "   .weak   " VMLINUX_SYMBOL_STR(__crc_##sym) "     \n"     \
  50            "   .long   " VMLINUX_SYMBOL_STR(__crc_##sym) " - . \n"     \
  51            "   .previous                                       \n");
  52#else
  53#define __CRC_SYMBOL(sym, sec)                                          \
  54        asm("   .section \"___kcrctab" sec "+" #sym "\", \"a\"  \n"     \
  55            "   .weak   " VMLINUX_SYMBOL_STR(__crc_##sym) "     \n"     \
  56            "   .long   " VMLINUX_SYMBOL_STR(__crc_##sym) "     \n"     \
  57            "   .previous                                       \n");
  58#endif
  59#else
  60#define __CRC_SYMBOL(sym, sec)
  61#endif
  62
  63/* For every exported symbol, place a struct in the __ksymtab section */
  64#define ___EXPORT_SYMBOL(sym, sec)                                      \
  65        extern typeof(sym) sym;                                         \
  66        __CRC_SYMBOL(sym, sec)                                          \
  67        static const char __kstrtab_##sym[]                             \
  68        __attribute__((section("__ksymtab_strings"), aligned(1)))       \
  69        = VMLINUX_SYMBOL_STR(sym);                                      \
  70        static const struct kernel_symbol __ksymtab_##sym               \
  71        __used                                                          \
  72        __attribute__((section("___ksymtab" sec "+" #sym), used))       \
  73        = { (unsigned long)&sym, __kstrtab_##sym }
  74
  75#if defined(__KSYM_DEPS__)
  76
  77/*
  78 * For fine grained build dependencies, we want to tell the build system
  79 * about each possible exported symbol even if they're not actually exported.
  80 * We use a string pattern that is unlikely to be valid code that the build
  81 * system filters out from the preprocessor output (see ksym_dep_filter
  82 * in scripts/Kbuild.include).
  83 */
  84#define __EXPORT_SYMBOL(sym, sec)       === __KSYM_##sym ===
  85
  86#elif defined(CONFIG_TRIM_UNUSED_KSYMS)
  87
  88#include <generated/autoksyms.h>
  89
  90#define __EXPORT_SYMBOL(sym, sec)                               \
  91        __cond_export_sym(sym, sec, __is_defined(__KSYM_##sym))
  92#define __cond_export_sym(sym, sec, conf)                       \
  93        ___cond_export_sym(sym, sec, conf)
  94#define ___cond_export_sym(sym, sec, enabled)                   \
  95        __cond_export_sym_##enabled(sym, sec)
  96#define __cond_export_sym_1(sym, sec) ___EXPORT_SYMBOL(sym, sec)
  97#define __cond_export_sym_0(sym, sec) /* nothing */
  98
  99#else
 100#define __EXPORT_SYMBOL ___EXPORT_SYMBOL
 101#endif
 102
 103#define EXPORT_SYMBOL(sym)                                      \
 104        __EXPORT_SYMBOL(sym, "")
 105
 106#define EXPORT_SYMBOL_GPL(sym)                                  \
 107        __EXPORT_SYMBOL(sym, "_gpl")
 108
 109#define EXPORT_SYMBOL_GPL_FUTURE(sym)                           \
 110        __EXPORT_SYMBOL(sym, "_gpl_future")
 111
 112#ifdef CONFIG_UNUSED_SYMBOLS
 113#define EXPORT_UNUSED_SYMBOL(sym) __EXPORT_SYMBOL(sym, "_unused")
 114#define EXPORT_UNUSED_SYMBOL_GPL(sym) __EXPORT_SYMBOL(sym, "_unused_gpl")
 115#else
 116#define EXPORT_UNUSED_SYMBOL(sym)
 117#define EXPORT_UNUSED_SYMBOL_GPL(sym)
 118#endif
 119
 120#endif  /* __GENKSYMS__ */
 121
 122#else /* !CONFIG_MODULES... */
 123
 124#define EXPORT_SYMBOL(sym)
 125#define EXPORT_SYMBOL_GPL(sym)
 126#define EXPORT_SYMBOL_GPL_FUTURE(sym)
 127#define EXPORT_UNUSED_SYMBOL(sym)
 128#define EXPORT_UNUSED_SYMBOL_GPL(sym)
 129
 130#endif /* CONFIG_MODULES */
 131#endif /* !__ASSEMBLY__ */
 132
 133#endif /* _LINUX_EXPORT_H */
 134