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
  15 extern 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
  69 struct 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
  87 struct 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 */