export.h (4934B)
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/* 17 * This comment block is used by fixdep. Please do not remove. 18 * 19 * When CONFIG_MODVERSIONS is changed from n to y, all source files having 20 * EXPORT_SYMBOL variants must be re-compiled because genksyms is run as a 21 * side effect of the *.o build rule. 22 */ 23 24#ifndef __ASSEMBLY__ 25#ifdef MODULE 26extern struct module __this_module; 27#define THIS_MODULE (&__this_module) 28#else 29#define THIS_MODULE ((struct module *)0) 30#endif 31 32#ifdef CONFIG_HAVE_ARCH_PREL32_RELOCATIONS 33#include <linux/compiler.h> 34/* 35 * Emit the ksymtab entry as a pair of relative references: this reduces 36 * the size by half on 64-bit architectures, and eliminates the need for 37 * absolute relocations that require runtime processing on relocatable 38 * kernels. 39 */ 40#define __KSYMTAB_ENTRY(sym, sec) \ 41 __ADDRESSABLE(sym) \ 42 asm(" .section \"___ksymtab" sec "+" #sym "\", \"a\" \n" \ 43 " .balign 4 \n" \ 44 "__ksymtab_" #sym ": \n" \ 45 " .long " #sym "- . \n" \ 46 " .long __kstrtab_" #sym "- . \n" \ 47 " .long __kstrtabns_" #sym "- . \n" \ 48 " .previous \n") 49 50struct kernel_symbol { 51 int value_offset; 52 int name_offset; 53 int namespace_offset; 54}; 55#else 56#define __KSYMTAB_ENTRY(sym, sec) \ 57 static const struct kernel_symbol __ksymtab_##sym \ 58 __attribute__((section("___ksymtab" sec "+" #sym), used)) \ 59 __aligned(sizeof(void *)) \ 60 = { (unsigned long)&sym, __kstrtab_##sym, __kstrtabns_##sym } 61 62struct kernel_symbol { 63 unsigned long value; 64 const char *name; 65 const char *namespace; 66}; 67#endif 68 69#ifdef __GENKSYMS__ 70 71#define ___EXPORT_SYMBOL(sym, sec, ns) __GENKSYMS_EXPORT_SYMBOL(sym) 72 73#else 74 75/* 76 * For every exported symbol, do the following: 77 * 78 * - Put the name of the symbol and namespace (empty string "" for none) in 79 * __ksymtab_strings. 80 * - Place a struct kernel_symbol entry in the __ksymtab section. 81 * 82 * note on .section use: we specify progbits since usage of the "M" (SHF_MERGE) 83 * section flag requires it. Use '%progbits' instead of '@progbits' since the 84 * former apparently works on all arches according to the binutils source. 85 */ 86#define ___EXPORT_SYMBOL(sym, sec, ns) \ 87 extern typeof(sym) sym; \ 88 extern const char __kstrtab_##sym[]; \ 89 extern const char __kstrtabns_##sym[]; \ 90 asm(" .section \"__ksymtab_strings\",\"aMS\",%progbits,1 \n" \ 91 "__kstrtab_" #sym ": \n" \ 92 " .asciz \"" #sym "\" \n" \ 93 "__kstrtabns_" #sym ": \n" \ 94 " .asciz \"" ns "\" \n" \ 95 " .previous \n"); \ 96 __KSYMTAB_ENTRY(sym, sec) 97 98#endif 99 100#if !defined(CONFIG_MODULES) || defined(__DISABLE_EXPORTS) 101 102/* 103 * Allow symbol exports to be disabled completely so that C code may 104 * be reused in other execution contexts such as the UEFI stub or the 105 * decompressor. 106 */ 107#define __EXPORT_SYMBOL(sym, sec, ns) 108 109#elif defined(CONFIG_TRIM_UNUSED_KSYMS) 110 111#include <generated/autoksyms.h> 112 113/* 114 * For fine grained build dependencies, we want to tell the build system 115 * about each possible exported symbol even if they're not actually exported. 116 * We use a symbol pattern __ksym_marker_<symbol> that the build system filters 117 * from the $(NM) output (see scripts/gen_ksymdeps.sh). These symbols are 118 * discarded in the final link stage. 119 */ 120#define __ksym_marker(sym) \ 121 static int __ksym_marker_##sym[0] __section(".discard.ksym") __used 122 123#define __EXPORT_SYMBOL(sym, sec, ns) \ 124 __ksym_marker(sym); \ 125 __cond_export_sym(sym, sec, ns, __is_defined(__KSYM_##sym)) 126#define __cond_export_sym(sym, sec, ns, conf) \ 127 ___cond_export_sym(sym, sec, ns, conf) 128#define ___cond_export_sym(sym, sec, ns, enabled) \ 129 __cond_export_sym_##enabled(sym, sec, ns) 130#define __cond_export_sym_1(sym, sec, ns) ___EXPORT_SYMBOL(sym, sec, ns) 131 132#ifdef __GENKSYMS__ 133#define __cond_export_sym_0(sym, sec, ns) __GENKSYMS_EXPORT_SYMBOL(sym) 134#else 135#define __cond_export_sym_0(sym, sec, ns) /* nothing */ 136#endif 137 138#else 139 140#define __EXPORT_SYMBOL(sym, sec, ns) ___EXPORT_SYMBOL(sym, sec, ns) 141 142#endif /* CONFIG_MODULES */ 143 144#ifdef DEFAULT_SYMBOL_NAMESPACE 145#define _EXPORT_SYMBOL(sym, sec) __EXPORT_SYMBOL(sym, sec, __stringify(DEFAULT_SYMBOL_NAMESPACE)) 146#else 147#define _EXPORT_SYMBOL(sym, sec) __EXPORT_SYMBOL(sym, sec, "") 148#endif 149 150#define EXPORT_SYMBOL(sym) _EXPORT_SYMBOL(sym, "") 151#define EXPORT_SYMBOL_GPL(sym) _EXPORT_SYMBOL(sym, "_gpl") 152#define EXPORT_SYMBOL_NS(sym, ns) __EXPORT_SYMBOL(sym, "", __stringify(ns)) 153#define EXPORT_SYMBOL_NS_GPL(sym, ns) __EXPORT_SYMBOL(sym, "_gpl", __stringify(ns)) 154 155#endif /* !__ASSEMBLY__ */ 156 157#endif /* _LINUX_EXPORT_H */