mirror of
https://gitee.com/bianbu-linux/linux-6.6
synced 2025-04-24 14:07:52 -04:00
b67067f117
Introduce LD_DEAD_CODE_DATA_ELIMINATION option for architectures to
select to build with -ffunction-sections, -fdata-sections, and link
with --gc-sections. It requires some work (documented) to ensure all
unreferenced entrypoints are live, and requires toolchain and build
verification, so it is made a per-arch option for now.
On a random powerpc64le build, this yelds a significant size saving,
it boots and runs fine, but there is a lot I haven't tested as yet, so
these savings may be reduced if there are bugs in the link.
text data bss dec filename
11169741 1180744 1923176 14273661 vmlinux
10445269 1004127 1919707 13369103 vmlinux.dce
~700K text, ~170K data, 6% removed from kernel image size.
Signed-off-by: Nicholas Piggin <npiggin@gmail.com>
Signed-off-by: Michal Marek <mmarek@suse.com>
127 lines
3.7 KiB
C
127 lines
3.7 KiB
C
#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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/* Some toolchains use a `_' prefix for all user symbols. */
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#ifdef CONFIG_HAVE_UNDERSCORE_SYMBOL_PREFIX
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#define __VMLINUX_SYMBOL(x) _##x
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#define __VMLINUX_SYMBOL_STR(x) "_" #x
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#else
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#define __VMLINUX_SYMBOL(x) x
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#define __VMLINUX_SYMBOL_STR(x) #x
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#endif
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/* Indirect, so macros are expanded before pasting. */
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#define VMLINUX_SYMBOL(x) __VMLINUX_SYMBOL(x)
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#define VMLINUX_SYMBOL_STR(x) __VMLINUX_SYMBOL_STR(x)
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#ifndef __ASSEMBLY__
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struct kernel_symbol
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{
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unsigned long value;
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const char *name;
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};
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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_MODULES
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#if defined(__KERNEL__) && !defined(__GENKSYMS__)
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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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#define __CRC_SYMBOL(sym, sec) \
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extern __visible void *__crc_##sym __attribute__((weak)); \
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static const unsigned long __kcrctab_##sym \
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__used \
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__attribute__((section("___kcrctab" sec "+" #sym), used)) \
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= (unsigned long) &__crc_##sym;
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#else
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#define __CRC_SYMBOL(sym, sec)
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#endif
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/* For every exported symbol, place a struct in the __ksymtab section */
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#define ___EXPORT_SYMBOL(sym, sec) \
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extern typeof(sym) sym; \
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__CRC_SYMBOL(sym, sec) \
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static const char __kstrtab_##sym[] \
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__attribute__((section("__ksymtab_strings"), aligned(1))) \
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= VMLINUX_SYMBOL_STR(sym); \
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static const struct kernel_symbol __ksymtab_##sym \
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__used \
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__attribute__((section("___ksymtab" sec "+" #sym), used)) \
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= { (unsigned long)&sym, __kstrtab_##sym }
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#if defined(__KSYM_DEPS__)
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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 string pattern that is unlikely to be valid code that the build
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* system filters out from the preprocessor output (see ksym_dep_filter
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* in scripts/Kbuild.include).
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*/
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#define __EXPORT_SYMBOL(sym, sec) === __KSYM_##sym ===
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#elif defined(CONFIG_TRIM_UNUSED_KSYMS)
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#include <linux/kconfig.h>
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#include <generated/autoksyms.h>
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#define __EXPORT_SYMBOL(sym, sec) \
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__cond_export_sym(sym, sec, __is_defined(__KSYM_##sym))
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#define __cond_export_sym(sym, sec, conf) \
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___cond_export_sym(sym, sec, conf)
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#define ___cond_export_sym(sym, sec, enabled) \
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__cond_export_sym_##enabled(sym, sec)
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#define __cond_export_sym_1(sym, sec) ___EXPORT_SYMBOL(sym, sec)
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#define __cond_export_sym_0(sym, sec) /* nothing */
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#else
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#define __EXPORT_SYMBOL ___EXPORT_SYMBOL
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#endif
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#define EXPORT_SYMBOL(sym) \
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__EXPORT_SYMBOL(sym, "")
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#define EXPORT_SYMBOL_GPL(sym) \
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__EXPORT_SYMBOL(sym, "_gpl")
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#define EXPORT_SYMBOL_GPL_FUTURE(sym) \
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__EXPORT_SYMBOL(sym, "_gpl_future")
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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 /* __GENKSYMS__ */
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#else /* !CONFIG_MODULES... */
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#define EXPORT_SYMBOL(sym)
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#define EXPORT_SYMBOL_GPL(sym)
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#define EXPORT_SYMBOL_GPL_FUTURE(sym)
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#define EXPORT_UNUSED_SYMBOL(sym)
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#define EXPORT_UNUSED_SYMBOL_GPL(sym)
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#endif /* CONFIG_MODULES */
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#endif /* !__ASSEMBLY__ */
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#endif /* _LINUX_EXPORT_H */
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