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