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TOMOYO Linux Cross Reference
Linux/include/linux/export.h

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  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_MODULES
 22 
 23 #if defined(__KERNEL__) && !defined(__GENKSYMS__)
 24 #ifdef CONFIG_MODVERSIONS
 25 /* Mark the CRC weak since genksyms apparently decides not to
 26  * generate a checksums for some symbols */
 27 #if defined(CONFIG_MODULE_REL_CRCS)
 28 #define __CRC_SYMBOL(sym, sec)                                          \
 29         asm("   .section \"___kcrctab" sec "+" #sym "\", \"a\"  \n"     \
 30             "   .weak   __crc_" #sym "                          \n"     \
 31             "   .long   __crc_" #sym " - .                      \n"     \
 32             "   .previous                                       \n");
 33 #else
 34 #define __CRC_SYMBOL(sym, sec)                                          \
 35         asm("   .section \"___kcrctab" sec "+" #sym "\", \"a\"  \n"     \
 36             "   .weak   __crc_" #sym "                          \n"     \
 37             "   .long   __crc_" #sym "                          \n"     \
 38             "   .previous                                       \n");
 39 #endif
 40 #else
 41 #define __CRC_SYMBOL(sym, sec)
 42 #endif
 43 
 44 #ifdef CONFIG_HAVE_ARCH_PREL32_RELOCATIONS
 45 #include <linux/compiler.h>
 46 /*
 47  * Emit the ksymtab entry as a pair of relative references: this reduces
 48  * the size by half on 64-bit architectures, and eliminates the need for
 49  * absolute relocations that require runtime processing on relocatable
 50  * kernels.
 51  */
 52 #define __KSYMTAB_ENTRY(sym, sec)                                       \
 53         __ADDRESSABLE(sym)                                              \
 54         asm("   .section \"___ksymtab" sec "+" #sym "\", \"a\"  \n"     \
 55             "   .balign 8                                       \n"     \
 56             "__ksymtab_" #sym ":                                \n"     \
 57             "   .long   " #sym "- .                             \n"     \
 58             "   .long   __kstrtab_" #sym "- .                   \n"     \
 59             "   .previous                                       \n")
 60 
 61 struct kernel_symbol {
 62         int value_offset;
 63         int name_offset;
 64 };
 65 #else
 66 #define __KSYMTAB_ENTRY(sym, sec)                                       \
 67         static const struct kernel_symbol __ksymtab_##sym               \
 68         __attribute__((section("___ksymtab" sec "+" #sym), used))       \
 69         = { (unsigned long)&sym, __kstrtab_##sym }
 70 
 71 struct kernel_symbol {
 72         unsigned long value;
 73         const char *name;
 74 };
 75 #endif
 76 
 77 /* For every exported symbol, place a struct in the __ksymtab section */
 78 #define ___EXPORT_SYMBOL(sym, sec)                                      \
 79         extern typeof(sym) sym;                                         \
 80         __CRC_SYMBOL(sym, sec)                                          \
 81         static const char __kstrtab_##sym[]                             \
 82         __attribute__((section("__ksymtab_strings"), used, aligned(1))) \
 83         = #sym;                                                         \
 84         __KSYMTAB_ENTRY(sym, sec)
 85 
 86 #if defined(__DISABLE_EXPORTS)
 87 
 88 /*
 89  * Allow symbol exports to be disabled completely so that C code may
 90  * be reused in other execution contexts such as the UEFI stub or the
 91  * decompressor.
 92  */
 93 #define __EXPORT_SYMBOL(sym, sec)
 94 
 95 #elif defined(CONFIG_TRIM_UNUSED_KSYMS)
 96 
 97 #include <generated/autoksyms.h>
 98 
 99 /*
100  * For fine grained build dependencies, we want to tell the build system
101  * about each possible exported symbol even if they're not actually exported.
102  * We use a symbol pattern __ksym_marker_<symbol> that the build system filters
103  * from the $(NM) output (see scripts/gen_ksymdeps.sh). These symbols are
104  * discarded in the final link stage.
105  */
106 #define __ksym_marker(sym)      \
107         static int __ksym_marker_##sym[0] __section(".discard.ksym") __used
108 
109 #define __EXPORT_SYMBOL(sym, sec)                               \
110         __ksym_marker(sym);                                     \
111         __cond_export_sym(sym, sec, __is_defined(__KSYM_##sym))
112 #define __cond_export_sym(sym, sec, conf)                       \
113         ___cond_export_sym(sym, sec, conf)
114 #define ___cond_export_sym(sym, sec, enabled)                   \
115         __cond_export_sym_##enabled(sym, sec)
116 #define __cond_export_sym_1(sym, sec) ___EXPORT_SYMBOL(sym, sec)
117 #define __cond_export_sym_0(sym, sec) /* nothing */
118 
119 #else
120 #define __EXPORT_SYMBOL ___EXPORT_SYMBOL
121 #endif
122 
123 #define EXPORT_SYMBOL(sym)                                      \
124         __EXPORT_SYMBOL(sym, "")
125 
126 #define EXPORT_SYMBOL_GPL(sym)                                  \
127         __EXPORT_SYMBOL(sym, "_gpl")
128 
129 #define EXPORT_SYMBOL_GPL_FUTURE(sym)                           \
130         __EXPORT_SYMBOL(sym, "_gpl_future")
131 
132 #ifdef CONFIG_UNUSED_SYMBOLS
133 #define EXPORT_UNUSED_SYMBOL(sym) __EXPORT_SYMBOL(sym, "_unused")
134 #define EXPORT_UNUSED_SYMBOL_GPL(sym) __EXPORT_SYMBOL(sym, "_unused_gpl")
135 #else
136 #define EXPORT_UNUSED_SYMBOL(sym)
137 #define EXPORT_UNUSED_SYMBOL_GPL(sym)
138 #endif
139 
140 #endif  /* __GENKSYMS__ */
141 
142 #else /* !CONFIG_MODULES... */
143 
144 #define EXPORT_SYMBOL(sym)
145 #define EXPORT_SYMBOL_GPL(sym)
146 #define EXPORT_SYMBOL_GPL_FUTURE(sym)
147 #define EXPORT_UNUSED_SYMBOL(sym)
148 #define EXPORT_UNUSED_SYMBOL_GPL(sym)
149 
150 #endif /* CONFIG_MODULES */
151 #endif /* !__ASSEMBLY__ */
152 
153 #endif /* _LINUX_EXPORT_H */
154 

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