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#ifndef __ASSEMBLY__
  14#ifdef MODULE
  15extern struct module __this_module;
  16#define THIS_MODULE (&__this_module)
  17#else
  18#define THIS_MODULE ((struct module *)0)
  19#endif
  20
  21#ifdef CONFIG_MODULES
  22
  23#if defined(__KERNEL__) && !defined(__GENKSYMS__)
  24#ifdef CONFIG_MODVERSIONS
  25/* Mark the CRC weak since genksyms apparently decides not to
  26 * generate a checksums for some symbols */
  27#if defined(CONFIG_MODULE_REL_CRCS)
  28#define __CRC_SYMBOL(sym, sec)                                          \
  29        asm("   .section \"___kcrctab" sec "+" #sym "\", \"a\"  \n"     \
  30            "   .weak   __crc_" #sym "                          \n"     \
  31            "   .long   __crc_" #sym " - .                      \n"     \
  32            "   .previous                                       \n");
  33#else
  34#define __CRC_SYMBOL(sym, sec)                                          \
  35        asm("   .section \"___kcrctab" sec "+" #sym "\", \"a\"  \n"     \
  36            "   .weak   __crc_" #sym "                          \n"     \
  37            "   .long   __crc_" #sym "                          \n"     \
  38            "   .previous                                       \n");
  39#endif
  40#else
  41#define __CRC_SYMBOL(sym, sec)
  42#endif
  43
  44#ifdef CONFIG_HAVE_ARCH_PREL32_RELOCATIONS
  45#include <linux/compiler.h>
  46/*
  47 * Emit the ksymtab entry as a pair of relative references: this reduces
  48 * the size by half on 64-bit architectures, and eliminates the need for
  49 * absolute relocations that require runtime processing on relocatable
  50 * kernels.
  51 */
  52#define __KSYMTAB_ENTRY(sym, sec)                                       \
  53        __ADDRESSABLE(sym)                                              \
  54        asm("   .section \"___ksymtab" sec "+" #sym "\", \"a\"  \n"     \
  55            "   .balign 8                                       \n"     \
  56            "__ksymtab_" #sym ":                                \n"     \
  57            "   .long   " #sym "- .                             \n"     \
  58            "   .long   __kstrtab_" #sym "- .                   \n"     \
  59            "   .previous                                       \n")
  60
  61struct kernel_symbol {
  62        int value_offset;
  63        int name_offset;
  64};
  65#else
  66#define __KSYMTAB_ENTRY(sym, sec)                                       \
  67        static const struct kernel_symbol __ksymtab_##sym               \
  68        __attribute__((section("___ksymtab" sec "+" #sym), used))       \
  69        = { (unsigned long)&sym, __kstrtab_##sym }
  70
  71struct kernel_symbol {
  72        unsigned long value;
  73        const char *name;
  74};
  75#endif
  76
  77/* For every exported symbol, place a struct in the __ksymtab section */
  78#define ___EXPORT_SYMBOL(sym, sec)                                      \
  79        extern typeof(sym) sym;                                         \
  80        __CRC_SYMBOL(sym, sec)                                          \
  81        static const char __kstrtab_##sym[]                             \
  82        __attribute__((section("__ksymtab_strings"), used, aligned(1))) \
  83        = #sym;                                                         \
  84        __KSYMTAB_ENTRY(sym, sec)
  85
  86#if defined(__DISABLE_EXPORTS)
  87
  88/*
  89 * Allow symbol exports to be disabled completely so that C code may
  90 * be reused in other execution contexts such as the UEFI stub or the
  91 * decompressor.
  92 */
  93#define __EXPORT_SYMBOL(sym, sec)
  94
  95#elif defined(CONFIG_TRIM_UNUSED_KSYMS)
  96
  97#include <generated/autoksyms.h>
  98
  99/*
 100 * For fine grained build dependencies, we want to tell the build system
 101 * about each possible exported symbol even if they're not actually exported.
 102 * We use a symbol pattern __ksym_marker_<symbol> that the build system filters
 103 * from the $(NM) output (see scripts/gen_ksymdeps.sh). These symbols are
 104 * discarded in the final link stage.
 105 */
 106#define __ksym_marker(sym)      \
 107        static int __ksym_marker_##sym[0] __section(".discard.ksym") __used
 108
 109#define __EXPORT_SYMBOL(sym, sec)                               \
 110        __ksym_marker(sym);                                     \
 111        __cond_export_sym(sym, sec, __is_defined(__KSYM_##sym))
 112#define __cond_export_sym(sym, sec, conf)                       \
 113        ___cond_export_sym(sym, sec, conf)
 114#define ___cond_export_sym(sym, sec, enabled)                   \
 115        __cond_export_sym_##enabled(sym, sec)
 116#define __cond_export_sym_1(sym, sec) ___EXPORT_SYMBOL(sym, sec)
 117#define __cond_export_sym_0(sym, sec) /* nothing */
 118
 119#else
 120#define __EXPORT_SYMBOL ___EXPORT_SYMBOL
 121#endif
 122
 123#define EXPORT_SYMBOL(sym)                                      \
 124        __EXPORT_SYMBOL(sym, "")
 125
 126#define EXPORT_SYMBOL_GPL(sym)                                  \
 127        __EXPORT_SYMBOL(sym, "_gpl")
 128
 129#define EXPORT_SYMBOL_GPL_FUTURE(sym)                           \
 130        __EXPORT_SYMBOL(sym, "_gpl_future")
 131
 132#ifdef CONFIG_UNUSED_SYMBOLS
 133#define EXPORT_UNUSED_SYMBOL(sym) __EXPORT_SYMBOL(sym, "_unused")
 134#define EXPORT_UNUSED_SYMBOL_GPL(sym) __EXPORT_SYMBOL(sym, "_unused_gpl")
 135#else
 136#define EXPORT_UNUSED_SYMBOL(sym)
 137#define EXPORT_UNUSED_SYMBOL_GPL(sym)
 138#endif
 139
 140#endif  /* __GENKSYMS__ */
 141
 142#else /* !CONFIG_MODULES... */
 143
 144#define EXPORT_SYMBOL(sym)
 145#define EXPORT_SYMBOL_GPL(sym)
 146#define EXPORT_SYMBOL_GPL_FUTURE(sym)
 147#define EXPORT_UNUSED_SYMBOL(sym)
 148#define EXPORT_UNUSED_SYMBOL_GPL(sym)
 149
 150#endif /* CONFIG_MODULES */
 151#endif /* !__ASSEMBLY__ */
 152
 153#endif /* _LINUX_EXPORT_H */
 154