1 /* SPDX-License-Identifier: GPL-2.0-only */
2 #ifndef _LINUX_EXPORT_H
3 #define _LINUX_EXPORT_H
4
5 /*
6 * Export symbols from the kernel to modules. Forked from module.h
7 * to reduce the amount of pointless cruft we feed to gcc when only
8 * exporting a simple symbol or two.
9 *
10 * Try not to add #includes here. It slows compilation and makes kernel
11 * hackers place grumpy comments in header files.
12 */
13
14 #ifndef __ASSEMBLY__
15 #ifdef MODULE
16 extern struct module __this_module;
17 #define THIS_MODULE (&__this_module)
18 #else
19 #define THIS_MODULE ((struct module *)0)
20 #endif
21
22 #ifdef CONFIG_MODVERSIONS
23 /* Mark the CRC weak since genksyms apparently decides not to
24 * generate a checksums for some symbols */
25 #if defined(CONFIG_MODULE_REL_CRCS)
26 #define __CRC_SYMBOL(sym, sec) \
27 asm(" .section \"___kcrctab" sec "+" #sym "\", \"a\" \n" \
28 " .weak __crc_" #sym " \n" \
29 " .long __crc_" #sym " - . \n" \
30 " .previous \n")
31 #else
32 #define __CRC_SYMBOL(sym, sec) \
33 asm(" .section \"___kcrctab" sec "+" #sym "\", \"a\" \n" \
34 " .weak __crc_" #sym " \n" \
35 " .long __crc_" #sym " \n" \
36 " .previous \n")
37 #endif
38 #else
39 #define __CRC_SYMBOL(sym, sec)
40 #endif
41
42 #ifdef CONFIG_HAVE_ARCH_PREL32_RELOCATIONS
43 #include <linux/compiler.h>
44 /*
45 * Emit the ksymtab entry as a pair of relative references: this reduces
46 * the size by half on 64-bit architectures, and eliminates the need for
47 * absolute relocations that require runtime processing on relocatable
48 * kernels.
49 */
50 #define __KSYMTAB_ENTRY(sym, sec) \
51 __ADDRESSABLE(sym) \
52 asm(" .section \"___ksymtab" sec "+" #sym "\", \"a\" \n" \
53 " .balign 4 \n" \
54 "__ksymtab_" #sym ": \n" \
55 " .long " #sym "- . \n" \
56 " .long __kstrtab_" #sym "- . \n" \
57 " .long __kstrtabns_" #sym "- . \n" \
58 " .previous \n")
59
60 struct kernel_symbol {
61 int value_offset;
62 int name_offset;
63 int namespace_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 __aligned(sizeof(void *)) \
70 = { (unsigned long)&sym, __kstrtab_##sym, __kstrtabns_##sym }
71
72 struct kernel_symbol {
73 unsigned long value;
74 const char *name;
75 const char *namespace;
76 };
77 #endif
78
79 #ifdef __GENKSYMS__
80
81 #define ___EXPORT_SYMBOL(sym, sec, ns) __GENKSYMS_EXPORT_SYMBOL(sym)
82
83 #else
84
85 /*
86 * For every exported symbol, do the following:
87 *
88 * - If applicable, place a CRC entry in the __kcrctab section.
89 * - Put the name of the symbol and namespace (empty string "" for none) in
90 * __ksymtab_strings.
91 * - Place a struct kernel_symbol entry in the __ksymtab section.
92 *
93 * note on .section use: we specify progbits since usage of the "M" (SHF_MERGE)
94 * section flag requires it. Use '%progbits' instead of '@progbits' since the
95 * former apparently works on all arches according to the binutils source.
96 */
97 #define ___EXPORT_SYMBOL(sym, sec, ns) \
98 extern typeof(sym) sym; \
99 extern const char __kstrtab_##sym[]; \
100 extern const char __kstrtabns_##sym[]; \
101 __CRC_SYMBOL(sym, sec); \
102 asm(" .section \"__ksymtab_strings\",\"aMS\",%progbits,1 \n" \
103 "__kstrtab_" #sym ": \n" \
104 " .asciz \"" #sym "\" \n" \
105 "__kstrtabns_" #sym ": \n" \
106 " .asciz \"" ns "\" \n" \
107 " .previous \n"); \
108 __KSYMTAB_ENTRY(sym, sec)
109
110 #endif
111
112 #if !defined(CONFIG_MODULES) || defined(__DISABLE_EXPORTS)
113
114 /*
115 * Allow symbol exports to be disabled completely so that C code may
116 * be reused in other execution contexts such as the UEFI stub or the
117 * decompressor.
118 */
119 #define __EXPORT_SYMBOL(sym, sec, ns)
120
121 #elif defined(CONFIG_TRIM_UNUSED_KSYMS)
122
123 #include <generated/autoksyms.h>
124
125 /*
126 * For fine grained build dependencies, we want to tell the build system
127 * about each possible exported symbol even if they're not actually exported.
128 * We use a symbol pattern __ksym_marker_<symbol> that the build system filters
129 * from the $(NM) output (see scripts/gen_ksymdeps.sh). These symbols are
130 * discarded in the final link stage.
131 */
132 #define __ksym_marker(sym) \
133 static int __ksym_marker_##sym[0] __section(".discard.ksym") __used
134
135 #define __EXPORT_SYMBOL(sym, sec, ns) \
136 __ksym_marker(sym); \
137 __cond_export_sym(sym, sec, ns, __is_defined(__KSYM_##sym))
138 #define __cond_export_sym(sym, sec, ns, conf) \
139 ___cond_export_sym(sym, sec, ns, conf)
140 #define ___cond_export_sym(sym, sec, ns, enabled) \
141 __cond_export_sym_##enabled(sym, sec, ns)
142 #define __cond_export_sym_1(sym, sec, ns) ___EXPORT_SYMBOL(sym, sec, ns)
143 #define __cond_export_sym_0(sym, sec, ns) /* nothing */
144
145 #else
146
147 #define __EXPORT_SYMBOL(sym, sec, ns) ___EXPORT_SYMBOL(sym, sec, ns)
148
149 #endif /* CONFIG_MODULES */
150
151 #ifdef DEFAULT_SYMBOL_NAMESPACE
152 #include <linux/stringify.h>
153 #define _EXPORT_SYMBOL(sym, sec) __EXPORT_SYMBOL(sym, sec, __stringify(DEFAULT_SYMBOL_NAMESPACE))
154 #else
155 #define _EXPORT_SYMBOL(sym, sec) __EXPORT_SYMBOL(sym, sec, "")
156 #endif
157
158 #define EXPORT_SYMBOL(sym) _EXPORT_SYMBOL(sym, "")
159 #define EXPORT_SYMBOL_GPL(sym) _EXPORT_SYMBOL(sym, "_gpl")
160 #define EXPORT_SYMBOL_GPL_FUTURE(sym) _EXPORT_SYMBOL(sym, "_gpl_future")
161 #define EXPORT_SYMBOL_NS(sym, ns) __EXPORT_SYMBOL(sym, "", #ns)
162 #define EXPORT_SYMBOL_NS_GPL(sym, ns) __EXPORT_SYMBOL(sym, "_gpl", #ns)
163
164 #ifdef CONFIG_UNUSED_SYMBOLS
165 #define EXPORT_UNUSED_SYMBOL(sym) _EXPORT_SYMBOL(sym, "_unused")
166 #define EXPORT_UNUSED_SYMBOL_GPL(sym) _EXPORT_SYMBOL(sym, "_unused_gpl")
167 #else
168 #define EXPORT_UNUSED_SYMBOL(sym)
169 #define EXPORT_UNUSED_SYMBOL_GPL(sym)
170 #endif
171
172 #endif /* !__ASSEMBLY__ */
173
174 #endif /* _LINUX_EXPORT_H */
175
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