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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