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(__KSYM_DEPS__)
96 
97 /*
98  * For fine grained build dependencies, we want to tell the build system
99  * about each possible exported symbol even if they're not actually exported.
100  * We use a string pattern that is unlikely to be valid code that the build
101  * system filters out from the preprocessor output (see ksym_dep_filter
102  * in scripts/Kbuild.include).
103  */
104 #define __EXPORT_SYMBOL(sym, sec)	=== __KSYM_##sym ===
105 
106 #elif defined(CONFIG_TRIM_UNUSED_KSYMS)
107 
108 #include <generated/autoksyms.h>
109 
110 #define __EXPORT_SYMBOL(sym, sec)				\
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