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 #define NS_SEPARATOR "."
  22
  23 #ifdef CONFIG_MODVERSIONS
  24 /* Mark the CRC weak since genksyms apparently decides not to
  25  * generate a checksums for some symbols */
  26 #if defined(CONFIG_MODULE_REL_CRCS)
  27 #define __CRC_SYMBOL(sym, sec)                                          \
  28         asm("   .section \"___kcrctab" sec "+" #sym "\", \"a\"  \n"     \
  29             "   .weak   __crc_" #sym "                          \n"     \
  30             "   .long   __crc_" #sym " - .                      \n"     \
  31             "   .previous                                       \n")
  32 #else
  33 #define __CRC_SYMBOL(sym, sec)                                          \
  34         asm("   .section \"___kcrctab" sec "+" #sym "\", \"a\"  \n"     \
  35             "   .weak   __crc_" #sym "                          \n"     \
  36             "   .long   __crc_" #sym "                          \n"     \
  37             "   .previous                                       \n")
  38 #endif
  39 #else
  40 #define __CRC_SYMBOL(sym, sec)
  41 #endif
  42
  43 #ifdef CONFIG_HAVE_ARCH_PREL32_RELOCATIONS
  44 #include <linux/compiler.h>
  45 /*
  46  * Emit the ksymtab entry as a pair of relative references: this reduces
  47  * the size by half on 64-bit architectures, and eliminates the need for
  48  * absolute relocations that require runtime processing on relocatable
  49  * kernels.
  50  */
  51 #define __KSYMTAB_ENTRY_NS(sym, sec, ns)                                \
  52         __ADDRESSABLE(sym)                                              \
  53         asm("   .section \"___ksymtab" sec "+" #sym "\", \"a\"  \n"     \
  54             "   .balign 4                                       \n"     \
  55             "__ksymtab_" #ns NS_SEPARATOR #sym ":               \n"     \
  56             "   .long   " #sym "- .                             \n"     \
  57             "   .long   __kstrtab_" #sym "- .                   \n"     \
  58             "   .long   __kstrtabns_" #sym "- .                 \n"     \
  59             "   .previous                                       \n")
  60
  61 #define __KSYMTAB_ENTRY(sym, sec)                                       \
  62         __ADDRESSABLE(sym)                                              \
  63         asm("   .section \"___ksymtab" sec "+" #sym "\", \"a\"  \n"     \
  64             "   .balign 4                                       \n"     \
  65             "__ksymtab_" #sym ":                                \n"     \
  66             "   .long   " #sym "- .                             \n"     \
  67             "   .long   __kstrtab_" #sym "- .                   \n"     \
  68             "   .long   0                                       \n"     \
  69             "   .previous                                       \n")
  70
  71 struct kernel_symbol {
  72         int value_offset;
  73         int name_offset;
  74         int namespace_offset;
  75 };
  76 #else
  77 #define __KSYMTAB_ENTRY_NS(sym, sec, ns)                                \
  78         static const struct kernel_symbol __ksymtab_##sym##__##ns       \
  79         asm("__ksymtab_" #ns NS_SEPARATOR #sym)                         \
  80         __attribute__((section("___ksymtab" sec "+" #sym), used))       \
  81         __aligned(sizeof(void *))                                       \
  82         = { (unsigned long)&sym, __kstrtab_##sym, __kstrtabns_##sym }
  83
  84 #define __KSYMTAB_ENTRY(sym, sec)                                       \
  85         static const struct kernel_symbol __ksymtab_##sym               \
  86         asm("__ksymtab_" #sym)                                          \
  87         __attribute__((section("___ksymtab" sec "+" #sym), used))       \
  88         __aligned(sizeof(void *))                                       \
  89         = { (unsigned long)&sym, __kstrtab_##sym, NULL }
  90
  91 struct kernel_symbol {
  92         unsigned long value;
  93         const char *name;
  94         const char *namespace;
  95 };
  96 #endif
  97
  98 #ifdef __GENKSYMS__
  99
 100 #define ___EXPORT_SYMBOL(sym,sec)       __GENKSYMS_EXPORT_SYMBOL(sym)
 101 #define ___EXPORT_SYMBOL_NS(sym,sec,ns) __GENKSYMS_EXPORT_SYMBOL(sym)
 102
 103 #else
 104
 105 #define ___export_symbol_common(sym, sec)                               \
 106         extern typeof(sym) sym;                                         \
 107         __CRC_SYMBOL(sym, sec);                                         \
 108         static const char __kstrtab_##sym[]                             \
 109         __attribute__((section("__ksymtab_strings"), used, aligned(1))) \
 110         = #sym                                                          \
 111
 112 /* For every exported symbol, place a struct in the __ksymtab section */
 113 #define ___EXPORT_SYMBOL_NS(sym, sec, ns)                               \
 114         ___export_symbol_common(sym, sec);                              \
 115         static const char __kstrtabns_##sym[]                           \
 116         __attribute__((section("__ksymtab_strings"), used, aligned(1))) \
 117         = #ns;                                                          \
 118         __KSYMTAB_ENTRY_NS(sym, sec, ns)
 119
 120 #define ___EXPORT_SYMBOL(sym, sec)                                      \
 121         ___export_symbol_common(sym, sec);                              \
 122         __KSYMTAB_ENTRY(sym, sec)
 123
 124 #endif
 125
 126 #if !defined(CONFIG_MODULES) || defined(__DISABLE_EXPORTS)
 127
 128 /*
 129  * Allow symbol exports to be disabled completely so that C code may
 130  * be reused in other execution contexts such as the UEFI stub or the
 131  * decompressor.
 132  */
 133 #define __EXPORT_SYMBOL_NS(sym, sec, ns)
 134 #define __EXPORT_SYMBOL(sym, sec)
 135
 136 #elif defined(CONFIG_TRIM_UNUSED_KSYMS)
 137
 138 #include <generated/autoksyms.h>
 139
 140 /*
 141  * For fine grained build dependencies, we want to tell the build system
 142  * about each possible exported symbol even if they're not actually exported.
 143  * We use a symbol pattern __ksym_marker_<symbol> that the build system filters
 144  * from the $(NM) output (see scripts/gen_ksymdeps.sh). These symbols are
 145  * discarded in the final link stage.
 146  */
 147 #define __ksym_marker(sym)      \
 148         static int __ksym_marker_##sym[0] __section(".discard.ksym") __used
 149
 150 #define __EXPORT_SYMBOL(sym, sec)                               \
 151         __ksym_marker(sym);                                     \
 152         __cond_export_sym(sym, sec, __is_defined(__KSYM_##sym))
 153 #define __cond_export_sym(sym, sec, conf)                       \
 154         ___cond_export_sym(sym, sec, conf)
 155 #define ___cond_export_sym(sym, sec, enabled)                   \
 156         __cond_export_sym_##enabled(sym, sec)
 157 #define __cond_export_sym_1(sym, sec) ___EXPORT_SYMBOL(sym, sec)
 158 #define __cond_export_sym_0(sym, sec) /* nothing */
 159
 160 #define __EXPORT_SYMBOL_NS(sym, sec, ns)                                \
 161         __ksym_marker(sym);                                             \
 162         __cond_export_ns_sym(sym, sec, ns, __is_defined(__KSYM_##sym))
 163 #define __cond_export_ns_sym(sym, sec, ns, conf)                        \
 164         ___cond_export_ns_sym(sym, sec, ns, conf)
 165 #define ___cond_export_ns_sym(sym, sec, ns, enabled)                    \
 166         __cond_export_ns_sym_##enabled(sym, sec, ns)
 167 #define __cond_export_ns_sym_1(sym, sec, ns) ___EXPORT_SYMBOL_NS(sym, sec, ns)
 168 #define __cond_export_ns_sym_0(sym, sec, ns) /* nothing */
 169
 170 #else
 171
 172 #define __EXPORT_SYMBOL_NS(sym,sec,ns)  ___EXPORT_SYMBOL_NS(sym,sec,ns)
 173 #define __EXPORT_SYMBOL(sym,sec)        ___EXPORT_SYMBOL(sym,sec)
 174
 175 #endif /* CONFIG_MODULES */
 176
 177 #ifdef DEFAULT_SYMBOL_NAMESPACE
 178 #undef __EXPORT_SYMBOL
 179 #define __EXPORT_SYMBOL(sym, sec)                               \
 180         __EXPORT_SYMBOL_NS(sym, sec, DEFAULT_SYMBOL_NAMESPACE)
 181 #endif
 182
 183 #define EXPORT_SYMBOL(sym)              __EXPORT_SYMBOL(sym, "")
 184 #define EXPORT_SYMBOL_GPL(sym)          __EXPORT_SYMBOL(sym, "_gpl")
 185 #define EXPORT_SYMBOL_GPL_FUTURE(sym)   __EXPORT_SYMBOL(sym, "_gpl_future")
 186 #define EXPORT_SYMBOL_NS(sym, ns)       __EXPORT_SYMBOL_NS(sym, "", ns)
 187 #define EXPORT_SYMBOL_NS_GPL(sym, ns)   __EXPORT_SYMBOL_NS(sym, "_gpl", ns)
 188
 189 #ifdef CONFIG_UNUSED_SYMBOLS
 190 #define EXPORT_UNUSED_SYMBOL(sym)       __EXPORT_SYMBOL(sym, "_unused")
 191 #define EXPORT_UNUSED_SYMBOL_GPL(sym)   __EXPORT_SYMBOL(sym, "_unused_gpl")
 192 #else
 193 #define EXPORT_UNUSED_SYMBOL(sym)
 194 #define EXPORT_UNUSED_SYMBOL_GPL(sym)
 195 #endif
 196
 197 #endif /* !__ASSEMBLY__ */
 198
 199 #endif /* _LINUX_EXPORT_H */