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 #ifdef CONFIG_CFI_CLANG 67 #include <linux/compiler.h> 68 /* 69 * With -fno-sanitize-cfi-canonical-jump-tables, the compiler replaces 70 * references to functions with jump table addresses. Use inline assembly 71 * to emit ksymtab entries that point to the actual function instead. 72 */ 73 #define ___KSYMTAB_ENTRY(sym, sec, size) \ 74 __ADDRESSABLE(sym) \ 75 asm(" .section \"___ksymtab" sec "+" #sym "\", \"a\" \n" \ 76 " .balign " #size " \n" \ 77 "__ksymtab_" #sym ": \n" \ 78 " ." #size "byte " #sym " \n" \ 79 " ." #size "byte __kstrtab_" #sym " \n" \ 80 " ." #size "byte __kstrtabns_" #sym " \n" \ 81 " .previous \n") 82 83 #ifdef CONFIG_64BIT 84 #define __KSYMTAB_ENTRY(sym, sec) ___KSYMTAB_ENTRY(sym, sec, 8) 85 #else 86 #define __KSYMTAB_ENTRY(sym, sec) ___KSYMTAB_ENTRY(sym, sec, 4) 87 #endif 88 89 #else /* !CONFIG_CFI_CLANG */ 90 91 #define __KSYMTAB_ENTRY(sym, sec) \ 92 static const struct kernel_symbol __ksymtab_##sym \ 93 __attribute__((section("___ksymtab" sec "+" #sym), used)) \ 94 __aligned(sizeof(void *)) \ 95 = { (unsigned long)&sym, __kstrtab_##sym, __kstrtabns_##sym } 96 97 #endif 98 99 struct kernel_symbol { 100 unsigned long value; 101 const char *name; 102 const char *namespace; 103 }; 104 #endif 105 106 #ifdef __GENKSYMS__ 107 108 #define ___EXPORT_SYMBOL(sym, sec, ns) __GENKSYMS_EXPORT_SYMBOL(sym) 109 110 #else 111 112 /* 113 * For every exported symbol, do the following: 114 * 115 * - If applicable, place a CRC entry in the __kcrctab section. 116 * - Put the name of the symbol and namespace (empty string "" for none) in 117 * __ksymtab_strings. 118 * - Place a struct kernel_symbol entry in the __ksymtab section. 119 * 120 * note on .section use: we specify progbits since usage of the "M" (SHF_MERGE) 121 * section flag requires it. Use '%progbits' instead of '@progbits' since the 122 * former apparently works on all arches according to the binutils source. 123 */ 124 #define ___EXPORT_SYMBOL(sym, sec, ns) \ 125 extern typeof(sym) sym; \ 126 extern const char __kstrtab_##sym[]; \ 127 extern const char __kstrtabns_##sym[]; \ 128 __CRC_SYMBOL(sym, sec); \ 129 asm(" .section \"__ksymtab_strings\",\"aMS\",%progbits,1 \n" \ 130 "__kstrtab_" #sym ": \n" \ 131 " .asciz \"" #sym "\" \n" \ 132 "__kstrtabns_" #sym ": \n" \ 133 " .asciz \"" ns "\" \n" \ 134 " .previous \n"); \ 135 __KSYMTAB_ENTRY(sym, sec) 136 137 #endif 138 139 #if !defined(CONFIG_MODULES) || defined(__DISABLE_EXPORTS) 140 141 /* 142 * Allow symbol exports to be disabled completely so that C code may 143 * be reused in other execution contexts such as the UEFI stub or the 144 * decompressor. 145 */ 146 #define __EXPORT_SYMBOL(sym, sec, ns) 147 148 #elif defined(CONFIG_TRIM_UNUSED_KSYMS) && !defined(MODULE) 149 150 #include <generated/autoksyms.h> 151 152 /* 153 * For fine grained build dependencies, we want to tell the build system 154 * about each possible exported symbol even if they're not actually exported. 155 * We use a symbol pattern __ksym_marker_<symbol> that the build system filters 156 * from the $(NM) output (see scripts/gen_ksymdeps.sh). These symbols are 157 * discarded in the final link stage. 158 */ 159 #define __ksym_marker(sym) \ 160 static int __ksym_marker_##sym[0] __section(".discard.ksym") __used 161 162 #define __EXPORT_SYMBOL(sym, sec, ns) \ 163 __ksym_marker(sym); \ 164 __cond_export_sym(sym, sec, ns, __is_defined(__KSYM_##sym)) 165 #define __cond_export_sym(sym, sec, ns, conf) \ 166 ___cond_export_sym(sym, sec, ns, conf) 167 #define ___cond_export_sym(sym, sec, ns, enabled) \ 168 __cond_export_sym_##enabled(sym, sec, ns) 169 #define __cond_export_sym_1(sym, sec, ns) ___EXPORT_SYMBOL(sym, sec, ns) 170 171 #ifdef __GENKSYMS__ 172 #define __cond_export_sym_0(sym, sec, ns) __GENKSYMS_EXPORT_SYMBOL(sym) 173 #else 174 #define __cond_export_sym_0(sym, sec, ns) /* nothing */ 175 #endif 176 177 #else 178 179 #define __EXPORT_SYMBOL(sym, sec, ns) ___EXPORT_SYMBOL(sym, sec, ns) 180 181 #endif /* CONFIG_MODULES */ 182 183 #ifdef DEFAULT_SYMBOL_NAMESPACE 184 #include <linux/stringify.h> 185 #define _EXPORT_SYMBOL(sym, sec) __EXPORT_SYMBOL(sym, sec, __stringify(DEFAULT_SYMBOL_NAMESPACE)) 186 #else 187 #define _EXPORT_SYMBOL(sym, sec) __EXPORT_SYMBOL(sym, sec, "") 188 #endif 189 190 #define EXPORT_SYMBOL(sym) _EXPORT_SYMBOL(sym, "") 191 #define EXPORT_SYMBOL_GPL(sym) _EXPORT_SYMBOL(sym, "_gpl") 192 #define EXPORT_SYMBOL_GPL_FUTURE(sym) _EXPORT_SYMBOL(sym, "_gpl_future") 193 #define _EXPORT_SYMBOL_NS(sym, ns) __EXPORT_SYMBOL(sym, "", #ns) 194 #define _EXPORT_SYMBOL_NS_GPL(sym, ns) __EXPORT_SYMBOL(sym, "_gpl", #ns) 195 #define EXPORT_SYMBOL_NS(sym, ns) _EXPORT_SYMBOL_NS(sym, ns) 196 #define EXPORT_SYMBOL_NS_GPL(sym, ns) _EXPORT_SYMBOL_NS_GPL(sym, ns) 197 198 #ifdef CONFIG_UNUSED_SYMBOLS 199 #define EXPORT_UNUSED_SYMBOL(sym) _EXPORT_SYMBOL(sym, "_unused") 200 #define EXPORT_UNUSED_SYMBOL_GPL(sym) _EXPORT_SYMBOL(sym, "_unused_gpl") 201 #else 202 #define EXPORT_UNUSED_SYMBOL(sym) 203 #define EXPORT_UNUSED_SYMBOL_GPL(sym) 204 #endif 205 206 #endif /* !__ASSEMBLY__ */ 207 208 #endif /* _LINUX_EXPORT_H */ 209