7cea01354e
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>
(cherry-pick from b67067f1176df6ee727450546b58704e4b588563)
Change-Id: I81b63489605bc2f146498d0bb0e1cc5b7adab8a0
Signed-off-by: Dan Aloni <daloni@magicleap.com>
Signed-off-by: Davide Garberi <dade.garberi@gmail.com>
99 lines
2.7 KiB
C
99 lines
2.7 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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#ifndef __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), unused)) \
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= { (unsigned long)&sym, __kstrtab_##sym }
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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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