1 /* SPDX-License-Identifier: GPL-2.0-only */ 2 #ifndef _LINUX_EXPORT_H 3 #define _LINUX_EXPORT_H 4 5 #include <linux/stringify.h> 6 7 /* 8 * Export symbols from the kernel to modules. Forked from module.h 9 * to reduce the amount of pointless cruft we feed to gcc when only 10 * exporting a simple symbol or two. 11 * 12 * Try not to add #includes here. It slows compilation and makes kernel 13 * hackers place grumpy comments in header files. 14 */ 15 16 #ifndef __ASSEMBLY__ 17 #ifdef MODULE 18 extern struct module __this_module; 19 #define THIS_MODULE (&__this_module) 20 #else 21 #define THIS_MODULE ((struct module *)0) 22 #endif 23 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 4 \n" \ 56 "__ksymtab_" #sym ": \n" \ 57 " .long " #sym "- . \n" \ 58 " .long __kstrtab_" #sym "- . \n" \ 59 " .long __kstrtabns_" #sym "- . \n" \ 60 " .previous \n") 61 62 struct kernel_symbol { 63 int value_offset; 64 int name_offset; 65 int namespace_offset; 66 }; 67 #else 68 #define __KSYMTAB_ENTRY(sym, sec) \ 69 static const struct kernel_symbol __ksymtab_##sym \ 70 __attribute__((section("___ksymtab" sec "+" #sym), used)) \ 71 __aligned(sizeof(void *)) \ 72 = { (unsigned long)&sym, __kstrtab_##sym, __kstrtabns_##sym } 73 74 struct kernel_symbol { 75 unsigned long value; 76 const char *name; 77 const char *namespace; 78 }; 79 #endif 80 81 #ifdef __GENKSYMS__ 82 83 #define ___EXPORT_SYMBOL(sym, sec, ns) __GENKSYMS_EXPORT_SYMBOL(sym) 84 85 #else 86 87 /* 88 * For every exported symbol, do the following: 89 * 90 * - If applicable, place a CRC entry in the __kcrctab section. 91 * - Put the name of the symbol and namespace (empty string "" for none) in 92 * __ksymtab_strings. 93 * - Place a struct kernel_symbol entry in the __ksymtab section. 94 * 95 * note on .section use: we specify progbits since usage of the "M" (SHF_MERGE) 96 * section flag requires it. Use '%progbits' instead of '@progbits' since the 97 * former apparently works on all arches according to the binutils source. 98 */ 99 #define ___EXPORT_SYMBOL(sym, sec, ns) \ 100 extern typeof(sym) sym; \ 101 extern const char __kstrtab_##sym[]; \ 102 extern const char __kstrtabns_##sym[]; \ 103 __CRC_SYMBOL(sym, sec); \ 104 asm(" .section \"__ksymtab_strings\",\"aMS\",%progbits,1 \n" \ 105 "__kstrtab_" #sym ": \n" \ 106 " .asciz \"" #sym "\" \n" \ 107 "__kstrtabns_" #sym ": \n" \ 108 " .asciz \"" ns "\" \n" \ 109 " .previous \n"); \ 110 __KSYMTAB_ENTRY(sym, sec) 111 112 #endif 113 114 #if !defined(CONFIG_MODULES) || defined(__DISABLE_EXPORTS) 115 116 /* 117 * Allow symbol exports to be disabled completely so that C code may 118 * be reused in other execution contexts such as the UEFI stub or the 119 * decompressor. 120 */ 121 #define __EXPORT_SYMBOL(sym, sec, ns) 122 123 #elif defined(CONFIG_TRIM_UNUSED_KSYMS) && !defined(MODULE) 124 125 #include <generated/autoksyms.h> 126 127 /* 128 * For fine grained build dependencies, we want to tell the build system 129 * about each possible exported symbol even if they're not actually exported. 130 * We use a symbol pattern __ksym_marker_<symbol> that the build system filters 131 * from the $(NM) output (see scripts/gen_ksymdeps.sh). These symbols are 132 * discarded in the final link stage. 133 */ 134 #define __ksym_marker(sym) \ 135 static int __ksym_marker_##sym[0] __section(".discard.ksym") __used 136 137 #define __EXPORT_SYMBOL(sym, sec, ns) \ 138 __ksym_marker(sym); \ 139 __cond_export_sym(sym, sec, ns, __is_defined(__KSYM_##sym)) 140 #define __cond_export_sym(sym, sec, ns, conf) \ 141 ___cond_export_sym(sym, sec, ns, conf) 142 #define ___cond_export_sym(sym, sec, ns, enabled) \ 143 __cond_export_sym_##enabled(sym, sec, ns) 144 #define __cond_export_sym_1(sym, sec, ns) ___EXPORT_SYMBOL(sym, sec, ns) 145 146 #ifdef __GENKSYMS__ 147 #define __cond_export_sym_0(sym, sec, ns) __GENKSYMS_EXPORT_SYMBOL(sym) 148 #else 149 #define __cond_export_sym_0(sym, sec, ns) /* nothing */ 150 #endif 151 152 #else 153 154 #define __EXPORT_SYMBOL(sym, sec, ns) ___EXPORT_SYMBOL(sym, sec, ns) 155 156 #endif /* CONFIG_MODULES */ 157 158 #ifdef DEFAULT_SYMBOL_NAMESPACE 159 #define _EXPORT_SYMBOL(sym, sec) __EXPORT_SYMBOL(sym, sec, __stringify(DEFAULT_SYMBOL_NAMESPACE)) 160 #else 161 #define _EXPORT_SYMBOL(sym, sec) __EXPORT_SYMBOL(sym, sec, "") 162 #endif 163 164 #define EXPORT_SYMBOL(sym) _EXPORT_SYMBOL(sym, "") 165 #define EXPORT_SYMBOL_GPL(sym) _EXPORT_SYMBOL(sym, "_gpl") 166 #define EXPORT_SYMBOL_NS(sym, ns) __EXPORT_SYMBOL(sym, "", __stringify(ns)) 167 #define EXPORT_SYMBOL_NS_GPL(sym, ns) __EXPORT_SYMBOL(sym, "_gpl", __stringify(ns)) 168 169 #endif /* !__ASSEMBLY__ */ 170 171 #endif /* _LINUX_EXPORT_H */ 172