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| author | Nicholas Piggin <npiggin@gmail.com> | 2016-08-24 22:29:20 +1000 |
|---|---|---|
| committer | Michal Marek <mmarek@suse.com> | 2016-09-09 10:47:00 +0200 |
| commit | b67067f1176df6ee727450546b58704e4b588563 (patch) | |
| tree | 59cfd4ebc0ea13e799b9e4393740591f9e16985d /include/linux/export.h | |
| parent | a5967db9af51a84f5e181600954714a9e4c69f1f (diff) | |
| download | lwn-b67067f1176df6ee727450546b58704e4b588563.tar.gz lwn-b67067f1176df6ee727450546b58704e4b588563.zip | |
kbuild: allow archs to select link dead code/data elimination
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>
Diffstat (limited to 'include/linux/export.h')
| -rw-r--r-- | include/linux/export.h | 30 |
1 files changed, 15 insertions, 15 deletions
diff --git a/include/linux/export.h b/include/linux/export.h index c565f87f005e..337cb90f3668 100644 --- a/include/linux/export.h +++ b/include/linux/export.h @@ -1,5 +1,6 @@ #ifndef _LINUX_EXPORT_H #define _LINUX_EXPORT_H + /* * Export symbols from the kernel to modules. Forked from module.h * to reduce the amount of pointless cruft we feed to gcc when only @@ -42,27 +43,26 @@ extern struct module __this_module; #ifdef CONFIG_MODVERSIONS /* Mark the CRC weak since genksyms apparently decides not to * generate a checksums for some symbols */ -#define __CRC_SYMBOL(sym, sec) \ - extern __visible void *__crc_##sym __attribute__((weak)); \ - static const unsigned long __kcrctab_##sym \ - __used \ - __attribute__((section("___kcrctab" sec "+" #sym), unused)) \ +#define __CRC_SYMBOL(sym, sec) \ + extern __visible void *__crc_##sym __attribute__((weak)); \ + static const unsigned long __kcrctab_##sym \ + __used \ + __attribute__((section("___kcrctab" sec "+" #sym), used)) \ = (unsigned long) &__crc_##sym; #else #define __CRC_SYMBOL(sym, sec) #endif /* For every exported symbol, place a struct in the __ksymtab section */ -#define ___EXPORT_SYMBOL(sym, sec) \ - extern typeof(sym) sym; \ - __CRC_SYMBOL(sym, sec) \ - static const char __kstrtab_##sym[] \ - __attribute__((section("__ksymtab_strings"), aligned(1))) \ - = VMLINUX_SYMBOL_STR(sym); \ - extern const struct kernel_symbol __ksymtab_##sym; \ - __visible const struct kernel_symbol __ksymtab_##sym \ - __used \ - __attribute__((section("___ksymtab" sec "+" #sym), unused)) \ +#define ___EXPORT_SYMBOL(sym, sec) \ + extern typeof(sym) sym; \ + __CRC_SYMBOL(sym, sec) \ + static const char __kstrtab_##sym[] \ + __attribute__((section("__ksymtab_strings"), aligned(1))) \ + = VMLINUX_SYMBOL_STR(sym); \ + static const struct kernel_symbol __ksymtab_##sym \ + __used \ + __attribute__((section("___ksymtab" sec "+" #sym), used)) \ = { (unsigned long)&sym, __kstrtab_##sym } #if defined(__KSYM_DEPS__) |