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__
  27 struct kernel_symbol
  28 {
  29         unsigned long value;
  30         const char *name;
  31 };
  32
  33 #ifdef MODULE
  34 extern 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 */