e135c46cdf
With CONFIG_CFI_CLANG, LLVM replaces function references with CFI jump table addresses to allow type checking with indirect calls. This is unnecessary in ksymtab, so this change uses inline assembly to emit ksymtab entries that point to the actual function instead when CFI is enabled. Bug: 145210207 Change-Id: I894af2c7df476eb00d656c7692a33b25de31e26d Signed-off-by: Sami Tolvanen <samitolvanen@google.com>
202 lines
6.3 KiB
C
202 lines
6.3 KiB
C
/* SPDX-License-Identifier: GPL-2.0-only */
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#ifndef _LINUX_EXPORT_H
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#define _LINUX_EXPORT_H
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/*
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* Export symbols from the kernel to modules. Forked from module.h
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* to reduce the amount of pointless cruft we feed to gcc when only
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* exporting a simple symbol or two.
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*
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* Try not to add #includes here. It slows compilation and makes kernel
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* hackers place grumpy comments in header files.
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*/
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#ifndef __ASSEMBLY__
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#ifdef MODULE
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extern struct module __this_module;
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#define THIS_MODULE (&__this_module)
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#else
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#define THIS_MODULE ((struct module *)0)
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#endif
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#ifdef CONFIG_MODVERSIONS
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/* Mark the CRC weak since genksyms apparently decides not to
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* generate a checksums for some symbols */
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#if defined(CONFIG_MODULE_REL_CRCS)
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#define __CRC_SYMBOL(sym, sec) \
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asm(" .section \"___kcrctab" sec "+" #sym "\", \"a\" \n" \
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" .weak __crc_" #sym " \n" \
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" .long __crc_" #sym " - . \n" \
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" .previous \n")
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#else
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#define __CRC_SYMBOL(sym, sec) \
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asm(" .section \"___kcrctab" sec "+" #sym "\", \"a\" \n" \
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" .weak __crc_" #sym " \n" \
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" .long __crc_" #sym " \n" \
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" .previous \n")
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#endif
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#else
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#define __CRC_SYMBOL(sym, sec)
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#endif
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#ifdef CONFIG_HAVE_ARCH_PREL32_RELOCATIONS
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#include <linux/compiler.h>
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/*
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* Emit the ksymtab entry as a pair of relative references: this reduces
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* the size by half on 64-bit architectures, and eliminates the need for
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* absolute relocations that require runtime processing on relocatable
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* kernels.
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*/
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#define __KSYMTAB_ENTRY(sym, sec) \
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__ADDRESSABLE(sym) \
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asm(" .section \"___ksymtab" sec "+" #sym "\", \"a\" \n" \
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" .balign 4 \n" \
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"__ksymtab_" #sym ": \n" \
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" .long " #sym "- . \n" \
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" .long __kstrtab_" #sym "- . \n" \
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" .long __kstrtabns_" #sym "- . \n" \
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" .previous \n")
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struct kernel_symbol {
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int value_offset;
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int name_offset;
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int namespace_offset;
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};
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#else
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#ifdef CONFIG_CFI_CLANG
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#include <linux/compiler.h>
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/*
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* With -fno-sanitize-cfi-canonical-jump-tables, the compiler replaces
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* references to functions with jump table addresses. Use inline assembly
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* to emit ksymtab entries that point to the actual function instead.
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*/
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#define ___KSYMTAB_ENTRY(sym, sec, size) \
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__ADDRESSABLE(sym) \
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asm(" .section \"___ksymtab" sec "+" #sym "\", \"a\" \n" \
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" .balign " #size " \n" \
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"__ksymtab_" #sym ": \n" \
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" ." #size "byte " #sym " \n" \
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" ." #size "byte __kstrtab_" #sym " \n" \
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" ." #size "byte __kstrtabns_" #sym " \n" \
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" .previous \n")
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#ifdef CONFIG_64BIT
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#define __KSYMTAB_ENTRY(sym, sec) ___KSYMTAB_ENTRY(sym, sec, 8)
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#else
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#define __KSYMTAB_ENTRY(sym, sec) ___KSYMTAB_ENTRY(sym, sec, 4)
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#endif
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#else /* !CONFIG_CFI_CLANG */
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#define __KSYMTAB_ENTRY(sym, sec) \
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static const struct kernel_symbol __ksymtab_##sym \
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__attribute__((section("___ksymtab" sec "+" #sym), used)) \
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__aligned(sizeof(void *)) \
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= { (unsigned long)&sym, __kstrtab_##sym, __kstrtabns_##sym }
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#endif
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struct kernel_symbol {
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unsigned long value;
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const char *name;
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const char *namespace;
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};
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#endif
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#ifdef __GENKSYMS__
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#define ___EXPORT_SYMBOL(sym, sec, ns) __GENKSYMS_EXPORT_SYMBOL(sym)
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#else
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/*
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* For every exported symbol, do the following:
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*
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* - If applicable, place a CRC entry in the __kcrctab section.
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* - Put the name of the symbol and namespace (empty string "" for none) in
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* __ksymtab_strings.
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* - Place a struct kernel_symbol entry in the __ksymtab section.
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*
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* note on .section use: we specify progbits since usage of the "M" (SHF_MERGE)
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* section flag requires it. Use '%progbits' instead of '@progbits' since the
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* former apparently works on all arches according to the binutils source.
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*/
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#define ___EXPORT_SYMBOL(sym, sec, ns) \
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extern typeof(sym) sym; \
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extern const char __kstrtab_##sym[]; \
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extern const char __kstrtabns_##sym[]; \
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__CRC_SYMBOL(sym, sec); \
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asm(" .section \"__ksymtab_strings\",\"aMS\",%progbits,1 \n" \
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"__kstrtab_" #sym ": \n" \
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" .asciz \"" #sym "\" \n" \
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"__kstrtabns_" #sym ": \n" \
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" .asciz \"" ns "\" \n" \
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" .previous \n"); \
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__KSYMTAB_ENTRY(sym, sec)
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#endif
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#if !defined(CONFIG_MODULES) || defined(__DISABLE_EXPORTS)
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/*
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* Allow symbol exports to be disabled completely so that C code may
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* be reused in other execution contexts such as the UEFI stub or the
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* decompressor.
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*/
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#define __EXPORT_SYMBOL(sym, sec, ns)
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#elif defined(CONFIG_TRIM_UNUSED_KSYMS) && !defined(MODULE)
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#include <generated/autoksyms.h>
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/*
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* For fine grained build dependencies, we want to tell the build system
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* about each possible exported symbol even if they're not actually exported.
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* We use a symbol pattern __ksym_marker_<symbol> that the build system filters
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* from the $(NM) output (see scripts/gen_ksymdeps.sh). These symbols are
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* discarded in the final link stage.
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*/
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#define __ksym_marker(sym) \
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static int __ksym_marker_##sym[0] __section(".discard.ksym") __used
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#define __EXPORT_SYMBOL(sym, sec, ns) \
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__ksym_marker(sym); \
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__cond_export_sym(sym, sec, ns, __is_defined(__KSYM_##sym))
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#define __cond_export_sym(sym, sec, ns, conf) \
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___cond_export_sym(sym, sec, ns, conf)
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#define ___cond_export_sym(sym, sec, ns, enabled) \
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__cond_export_sym_##enabled(sym, sec, ns)
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#define __cond_export_sym_1(sym, sec, ns) ___EXPORT_SYMBOL(sym, sec, ns)
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#define __cond_export_sym_0(sym, sec, ns) /* nothing */
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#else
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#define __EXPORT_SYMBOL(sym, sec, ns) ___EXPORT_SYMBOL(sym, sec, ns)
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#endif /* CONFIG_MODULES */
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#ifdef DEFAULT_SYMBOL_NAMESPACE
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#include <linux/stringify.h>
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#define _EXPORT_SYMBOL(sym, sec) __EXPORT_SYMBOL(sym, sec, __stringify(DEFAULT_SYMBOL_NAMESPACE))
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#else
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#define _EXPORT_SYMBOL(sym, sec) __EXPORT_SYMBOL(sym, sec, "")
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#endif
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#define EXPORT_SYMBOL(sym) _EXPORT_SYMBOL(sym, "")
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#define EXPORT_SYMBOL_GPL(sym) _EXPORT_SYMBOL(sym, "_gpl")
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#define EXPORT_SYMBOL_GPL_FUTURE(sym) _EXPORT_SYMBOL(sym, "_gpl_future")
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#define EXPORT_SYMBOL_NS(sym, ns) __EXPORT_SYMBOL(sym, "", #ns)
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#define EXPORT_SYMBOL_NS_GPL(sym, ns) __EXPORT_SYMBOL(sym, "_gpl", #ns)
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#ifdef CONFIG_UNUSED_SYMBOLS
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#define EXPORT_UNUSED_SYMBOL(sym) _EXPORT_SYMBOL(sym, "_unused")
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#define EXPORT_UNUSED_SYMBOL_GPL(sym) _EXPORT_SYMBOL(sym, "_unused_gpl")
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#else
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#define EXPORT_UNUSED_SYMBOL(sym)
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#define EXPORT_UNUSED_SYMBOL_GPL(sym)
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#endif
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#endif /* !__ASSEMBLY__ */
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#endif /* _LINUX_EXPORT_H */
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