• Masahiro Yamada's avatar
    kbuild: simplify dependency generation for CONFIG_TRIM_UNUSED_KSYMS · bbda5ec6
    Masahiro Yamada authored
    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: default avatarMasahiro Yamada <yamada.masahiro@socionext.com>
    Reviewed-by: default avatarNicolas Pitre <nico@linaro.org>
    bbda5ec6
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