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 #ifdef MODULE
  22 extern struct module __this_module;
  23 #define THIS_MODULE (&__this_module)
  24 #else
  25 #define THIS_MODULE ((struct module *)0)
  26 #endif
  27
  28 #ifdef CONFIG_MODULES
  29
  30 #if defined(__KERNEL__) && !defined(__GENKSYMS__)
  31 #ifdef CONFIG_MODVERSIONS
  32 /* Mark the CRC weak since genksyms apparently decides not to
  33  * generate a checksums for some symbols */
  34 #if defined(CONFIG_MODULE_REL_CRCS)
  35 #define __CRC_SYMBOL(sym, sec)                                          \
  36         asm("   .section \"___kcrctab" sec "+" #sym "\", \"a\"  \n"     \
  37             "   .weak   __crc_" #sym "                          \n"     \
  38             "   .long   __crc_" #sym " - .                      \n"     \
  39             "   .previous                                       \n");
  40 #else
  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 #endif
  47 #else
  48 #define __CRC_SYMBOL(sym, sec)
  49 #endif
  50
  51 #ifdef CONFIG_HAVE_ARCH_PREL32_RELOCATIONS
  52 #include <linux/compiler.h>
  53 /*
  54  * Emit the ksymtab entry as a pair of relative references: this reduces
  55  * the size by half on 64-bit architectures, and eliminates the need for
  56  * absolute relocations that require runtime processing on relocatable
  57  * kernels.
  58  */
  59 #define __KSYMTAB_ENTRY(sym, sec)                                       \
  60         __ADDRESSABLE(sym)                                              \
  61         asm("   .section \"___ksymtab" sec "+" #sym "\", \"a\"  \n"     \
  62             "   .balign 8                                       \n"     \
  63             "__ksymtab_" #sym ":                                \n"     \
  64             "   .long   " #sym "- .                             \n"     \
  65             "   .long   __kstrtab_" #sym "- .                   \n"     \
  66             "   .previous                                       \n")
  67
  68 struct kernel_symbol {
  69         int value_offset;
  70         int name_offset;
  71 };
  72 #else
  73 #define __KSYMTAB_ENTRY(sym, sec)                                       \
  74         static const struct kernel_symbol __ksymtab_##sym               \
  75         __attribute__((section("___ksymtab" sec "+" #sym), used))       \
  76         = { (unsigned long)&sym, __kstrtab_##sym }
  77
  78 struct kernel_symbol {
  79         unsigned long value;
  80         const char *name;
  81 };
  82 #endif
  83
  84 /* For every exported symbol, place a struct in the __ksymtab section */
  85 #define ___EXPORT_SYMBOL(sym, sec)                                      \
  86         extern typeof(sym) sym;                                         \
  87         __CRC_SYMBOL(sym, sec)                                          \
  88         static const char __kstrtab_##sym[]                             \
  89         __attribute__((section("__ksymtab_strings"), used, aligned(1))) \
  90         = #sym;                                                         \
  91         __KSYMTAB_ENTRY(sym, sec)
  92
  93 #if defined(__DISABLE_EXPORTS)
  94
  95 /*
  96  * Allow symbol exports to be disabled completely so that C code may
  97  * be reused in other execution contexts such as the UEFI stub or the
  98  * decompressor.
  99  */
 100 #define __EXPORT_SYMBOL(sym, sec)
 101
 102 #elif defined(__KSYM_DEPS__)
 103
 104 /*
 105  * For fine grained build dependencies, we want to tell the build system
 106  * about each possible exported symbol even if they're not actually exported.
 107  * We use a string pattern that is unlikely to be valid code that the build
 108  * system filters out from the preprocessor output (see ksym_dep_filter
 109  * in scripts/Kbuild.include).
 110  */
 111 #define __EXPORT_SYMBOL(sym, sec)       === __KSYM_##sym ===
 112
 113 #elif defined(CONFIG_TRIM_UNUSED_KSYMS)
 114
 115 #include <generated/autoksyms.h>
 116
 117 #define __EXPORT_SYMBOL(sym, sec)                               \
 118         __cond_export_sym(sym, sec, __is_defined(__KSYM_##sym))
 119 #define __cond_export_sym(sym, sec, conf)                       \
 120         ___cond_export_sym(sym, sec, conf)
 121 #define ___cond_export_sym(sym, sec, enabled)                   \
 122         __cond_export_sym_##enabled(sym, sec)
 123 #define __cond_export_sym_1(sym, sec) ___EXPORT_SYMBOL(sym, sec)
 124 #define __cond_export_sym_0(sym, sec) /* nothing */
 125
 126 #else
 127 #define __EXPORT_SYMBOL ___EXPORT_SYMBOL
 128 #endif
 129
 130 #define EXPORT_SYMBOL(sym)                                      \
 131         __EXPORT_SYMBOL(sym, "")
 132
 133 #define EXPORT_SYMBOL_GPL(sym)                                  \
 134         __EXPORT_SYMBOL(sym, "_gpl")
 135
 136 #define EXPORT_SYMBOL_GPL_FUTURE(sym)                           \
 137         __EXPORT_SYMBOL(sym, "_gpl_future")
 138
 139 #ifdef CONFIG_UNUSED_SYMBOLS
 140 #define EXPORT_UNUSED_SYMBOL(sym) __EXPORT_SYMBOL(sym, "_unused")
 141 #define EXPORT_UNUSED_SYMBOL_GPL(sym) __EXPORT_SYMBOL(sym, "_unused_gpl")
 142 #else
 143 #define EXPORT_UNUSED_SYMBOL(sym)
 144 #define EXPORT_UNUSED_SYMBOL_GPL(sym)
 145 #endif
 146
 147 #endif  /* __GENKSYMS__ */
 148
 149 #else /* !CONFIG_MODULES... */
 150
 151 #define EXPORT_SYMBOL(sym)
 152 #define EXPORT_SYMBOL_GPL(sym)
 153 #define EXPORT_SYMBOL_GPL_FUTURE(sym)
 154 #define EXPORT_UNUSED_SYMBOL(sym)
 155 #define EXPORT_UNUSED_SYMBOL_GPL(sym)
 156
 157 #endif /* CONFIG_MODULES */
 158 #endif /* !__ASSEMBLY__ */
 159
 160 #endif /* _LINUX_EXPORT_H */