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_MODVERSIONS
  22/* Mark the CRC weak since genksyms apparently decides not to
  23 * generate a checksums for some symbols */
  24#if defined(CONFIG_MODULE_REL_CRCS)
  25#define __CRC_SYMBOL(sym, sec)                                          \
  26        asm("   .section \"___kcrctab" sec "+" #sym "\", \"a\"  \n"     \
  27            "   .weak   __crc_" #sym "                          \n"     \
  28            "   .long   __crc_" #sym " - .                      \n"     \
  29            "   .previous                                       \n")
  30#else
  31#define __CRC_SYMBOL(sym, sec)                                          \
  32        asm("   .section \"___kcrctab" sec "+" #sym "\", \"a\"  \n"     \
  33            "   .weak   __crc_" #sym "                          \n"     \
  34            "   .long   __crc_" #sym "                          \n"     \
  35            "   .previous                                       \n")
  36#endif
  37#else
  38#define __CRC_SYMBOL(sym, sec)
  39#endif
  40
  41#ifdef CONFIG_HAVE_ARCH_PREL32_RELOCATIONS
  42#include <linux/compiler.h>
  43/*
  44 * Emit the ksymtab entry as a pair of relative references: this reduces
  45 * the size by half on 64-bit architectures, and eliminates the need for
  46 * absolute relocations that require runtime processing on relocatable
  47 * kernels.
  48 */
  49#define __KSYMTAB_ENTRY_NS(sym, sec)                                    \
  50        __ADDRESSABLE(sym)                                              \
  51        asm("   .section \"___ksymtab" sec "+" #sym "\", \"a\"  \n"     \
  52            "   .balign 4                                       \n"     \
  53            "__ksymtab_" #sym ":                                \n"     \
  54            "   .long   " #sym "- .                             \n"     \
  55            "   .long   __kstrtab_" #sym "- .                   \n"     \
  56            "   .long   __kstrtabns_" #sym "- .                 \n"     \
  57            "   .previous                                       \n")
  58
  59#define __KSYMTAB_ENTRY(sym, sec)                                       \
  60        __ADDRESSABLE(sym)                                              \
  61        asm("   .section \"___ksymtab" sec "+" #sym "\", \"a\"  \n"     \
  62            "   .balign 4                                       \n"     \
  63            "__ksymtab_" #sym ":                                \n"     \
  64            "   .long   " #sym "- .                             \n"     \
  65            "   .long   __kstrtab_" #sym "- .                   \n"     \
  66            "   .long   0                                       \n"     \
  67            "   .previous                                       \n")
  68
  69struct kernel_symbol {
  70        int value_offset;
  71        int name_offset;
  72        int namespace_offset;
  73};
  74#else
  75#define __KSYMTAB_ENTRY_NS(sym, sec)                                    \
  76        static const struct kernel_symbol __ksymtab_##sym               \
  77        __attribute__((section("___ksymtab" sec "+" #sym), used))       \
  78        __aligned(sizeof(void *))                                       \
  79        = { (unsigned long)&sym, __kstrtab_##sym, __kstrtabns_##sym }
  80
  81#define __KSYMTAB_ENTRY(sym, sec)                                       \
  82        static const struct kernel_symbol __ksymtab_##sym               \
  83        __attribute__((section("___ksymtab" sec "+" #sym), used))       \
  84        __aligned(sizeof(void *))                                       \
  85        = { (unsigned long)&sym, __kstrtab_##sym, NULL }
  86
  87struct kernel_symbol {
  88        unsigned long value;
  89        const char *name;
  90        const char *namespace;
  91};
  92#endif
  93
  94#ifdef __GENKSYMS__
  95
  96#define ___EXPORT_SYMBOL(sym,sec)       __GENKSYMS_EXPORT_SYMBOL(sym)
  97#define ___EXPORT_SYMBOL_NS(sym,sec,ns) __GENKSYMS_EXPORT_SYMBOL(sym)
  98
  99#else
 100
 101#define ___export_symbol_common(sym, sec)                               \
 102        extern typeof(sym) sym;                                         \
 103        __CRC_SYMBOL(sym, sec);                                         \
 104        static const char __kstrtab_##sym[]                             \
 105        __attribute__((section("__ksymtab_strings"), used, aligned(1))) \
 106        = #sym                                                          \
 107
 108/* For every exported symbol, place a struct in the __ksymtab section */
 109#define ___EXPORT_SYMBOL_NS(sym, sec, ns)                               \
 110        ___export_symbol_common(sym, sec);                              \
 111        static const char __kstrtabns_##sym[]                           \
 112        __attribute__((section("__ksymtab_strings"), used, aligned(1))) \
 113        = #ns;                                                          \
 114        __KSYMTAB_ENTRY_NS(sym, sec)
 115
 116#define ___EXPORT_SYMBOL(sym, sec)                                      \
 117        ___export_symbol_common(sym, sec);                              \
 118        __KSYMTAB_ENTRY(sym, sec)
 119
 120#endif
 121
 122#if !defined(CONFIG_MODULES) || defined(__DISABLE_EXPORTS)
 123
 124/*
 125 * Allow symbol exports to be disabled completely so that C code may
 126 * be reused in other execution contexts such as the UEFI stub or the
 127 * decompressor.
 128 */
 129#define __EXPORT_SYMBOL_NS(sym, sec, ns)
 130#define __EXPORT_SYMBOL(sym, sec)
 131
 132#elif defined(CONFIG_TRIM_UNUSED_KSYMS)
 133
 134#include <generated/autoksyms.h>
 135
 136/*
 137 * For fine grained build dependencies, we want to tell the build system
 138 * about each possible exported symbol even if they're not actually exported.
 139 * We use a symbol pattern __ksym_marker_<symbol> that the build system filters
 140 * from the $(NM) output (see scripts/gen_ksymdeps.sh). These symbols are
 141 * discarded in the final link stage.
 142 */
 143#define __ksym_marker(sym)      \
 144        static int __ksym_marker_##sym[0] __section(".discard.ksym") __used
 145
 146#define __EXPORT_SYMBOL(sym, sec)                               \
 147        __ksym_marker(sym);                                     \
 148        __cond_export_sym(sym, sec, __is_defined(__KSYM_##sym))
 149#define __cond_export_sym(sym, sec, conf)                       \
 150        ___cond_export_sym(sym, sec, conf)
 151#define ___cond_export_sym(sym, sec, enabled)                   \
 152        __cond_export_sym_##enabled(sym, sec)
 153#define __cond_export_sym_1(sym, sec) ___EXPORT_SYMBOL(sym, sec)
 154#define __cond_export_sym_0(sym, sec) /* nothing */
 155
 156#define __EXPORT_SYMBOL_NS(sym, sec, ns)                                \
 157        __ksym_marker(sym);                                             \
 158        __cond_export_ns_sym(sym, sec, ns, __is_defined(__KSYM_##sym))
 159#define __cond_export_ns_sym(sym, sec, ns, conf)                        \
 160        ___cond_export_ns_sym(sym, sec, ns, conf)
 161#define ___cond_export_ns_sym(sym, sec, ns, enabled)                    \
 162        __cond_export_ns_sym_##enabled(sym, sec, ns)
 163#define __cond_export_ns_sym_1(sym, sec, ns) ___EXPORT_SYMBOL_NS(sym, sec, ns)
 164#define __cond_export_ns_sym_0(sym, sec, ns) /* nothing */
 165
 166#else
 167
 168#define __EXPORT_SYMBOL_NS(sym,sec,ns)  ___EXPORT_SYMBOL_NS(sym,sec,ns)
 169#define __EXPORT_SYMBOL(sym,sec)        ___EXPORT_SYMBOL(sym,sec)
 170
 171#endif /* CONFIG_MODULES */
 172
 173#ifdef DEFAULT_SYMBOL_NAMESPACE
 174#undef __EXPORT_SYMBOL
 175#define __EXPORT_SYMBOL(sym, sec)                               \
 176        __EXPORT_SYMBOL_NS(sym, sec, DEFAULT_SYMBOL_NAMESPACE)
 177#endif
 178
 179#define EXPORT_SYMBOL(sym)              __EXPORT_SYMBOL(sym, "")
 180#define EXPORT_SYMBOL_GPL(sym)          __EXPORT_SYMBOL(sym, "_gpl")
 181#define EXPORT_SYMBOL_GPL_FUTURE(sym)   __EXPORT_SYMBOL(sym, "_gpl_future")
 182#define EXPORT_SYMBOL_NS(sym, ns)       __EXPORT_SYMBOL_NS(sym, "", ns)
 183#define EXPORT_SYMBOL_NS_GPL(sym, ns)   __EXPORT_SYMBOL_NS(sym, "_gpl", ns)
 184
 185#ifdef CONFIG_UNUSED_SYMBOLS
 186#define EXPORT_UNUSED_SYMBOL(sym)       __EXPORT_SYMBOL(sym, "_unused")
 187#define EXPORT_UNUSED_SYMBOL_GPL(sym)   __EXPORT_SYMBOL(sym, "_unused_gpl")
 188#else
 189#define EXPORT_UNUSED_SYMBOL(sym)
 190#define EXPORT_UNUSED_SYMBOL_GPL(sym)
 191#endif
 192
 193#endif /* !__ASSEMBLY__ */
 194
 195#endif /* _LINUX_EXPORT_H */
 196