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| author | Masahiro Yamada <yamada.masahiro@socionext.com> | 2018-11-30 10:05:26 +0900 |
|---|---|---|
| committer | Masahiro Yamada <yamada.masahiro@socionext.com> | 2018-12-01 23:13:14 +0900 |
| commit | bbda5ec671d3fe62faefa1cab7270aa586042a4b (patch) | |
| tree | a1d375f74ad25efd2797bffaadfb0dc5fc1f65fe /include/linux/export.h | |
| parent | ee3e46b7efd2954479f87030d31fda3c22bbc763 (diff) | |
kbuild: simplify dependency generation for CONFIG_TRIM_UNUSED_KSYMS
My main motivation of this commit is to clean up scripts/Kbuild.include
and scripts/Makefile.build.
Currently, CONFIG_TRIM_UNUSED_KSYMS works with a tricky gimmick;
possibly exported symbols are detected by letting $(CPP) replace
EXPORT_SYMBOL* with a special string '=== __KSYM_*===', which is
post-processed by sed, and passed to fixdep. The extra preprocessing
is costly, and hacking cmd_and_fixdep is ugly.
I came up with a new way to find exported symbols; insert a dummy
symbol __ksym_marker_* to each potentially exported symbol. Those
dummy symbols are picked up by $(NM), post-processed by sed, then
appended to .*.cmd files. I collected the post-process part to a
new shell script scripts/gen_ksymdeps.sh for readability. The dummy
symbols are put into the .discard.* section so that the linker
script rips them off the final vmlinux or modules.
A nice side-effect is building with CONFIG_TRIM_UNUSED_KSYMS will
be much faster.
Signed-off-by: Masahiro Yamada <yamada.masahiro@socionext.com>
Reviewed-by: Nicolas Pitre <nico@linaro.org>
Diffstat (limited to 'include/linux/export.h')
| -rw-r--r-- | include/linux/export.h | 18 |
1 files changed, 9 insertions, 9 deletions
diff --git a/include/linux/export.h b/include/linux/export.h index ce764a5d2ee4..fd8711ed9ac4 100644 --- a/include/linux/export.h +++ b/include/linux/export.h @@ -92,22 +92,22 @@ struct kernel_symbol { */ #define __EXPORT_SYMBOL(sym, sec) -#elif defined(__KSYM_DEPS__) +#elif defined(CONFIG_TRIM_UNUSED_KSYMS) + +#include <generated/autoksyms.h> /* * For fine grained build dependencies, we want to tell the build system * about each possible exported symbol even if they're not actually exported. - * We use a string pattern that is unlikely to be valid code that the build - * system filters out from the preprocessor output (see ksym_dep_filter - * in scripts/Kbuild.include). + * We use a symbol pattern __ksym_marker_<symbol> that the build system filters + * from the $(NM) output (see scripts/gen_ksymdeps.sh). These symbols are + * discarded in the final link stage. */ -#define __EXPORT_SYMBOL(sym, sec) === __KSYM_##sym === - -#elif defined(CONFIG_TRIM_UNUSED_KSYMS) - -#include <generated/autoksyms.h> +#define __ksym_marker(sym) \ + static int __ksym_marker_##sym[0] __section(".discard.ksym") __used #define __EXPORT_SYMBOL(sym, sec) \ + __ksym_marker(sym); \ __cond_export_sym(sym, sec, __is_defined(__KSYM_##sym)) #define __cond_export_sym(sym, sec, conf) \ ___cond_export_sym(sym, sec, conf) |