Commit 0e0345b77a ("kbuild: redo fake deps at include/config/*.h")
simplified the Kconfig/fixdep interaction a lot.
For CONFIG_FOO_BAR_BAZ, Kconfig now touches include/config/FOO_BAR_BAZ
instead of the previous include/config/foo/bar/baz.h .
This commit simplifies the TRIM_UNUSED_KSYMS feature in a similar way:
- delete .h suffix
- delete tolower()
- put everything in 1 directory
For EXPORT_SYMBOL(FOO_BAR_BAZ), scripts/adjust_autoksyms.sh now touches
include/ksym/FOO_BAR_BAZ instead of include/ksym/foo/bar/baz.h .
This is more precise, avoiding possibly unnecessary rebuilds.
EXPORT_SYMBOL(FOO_BAR_BAZ)
EXPORT_SYMBOL(_FOO_BAR_BAZ)
EXPORT_SYMBOL(__FOO_BAR_BAZ)
were previously mapped to the same header, include/ksym/foo/bar/baz.h
but now are handled separately.
Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>
When CONFIG_TRIM_UNUSED_KSYMS is enabled, I see some warnings like this:
nm: arch/x86/entry/vdso/vdso32/note.o: no symbols
$NM (both GNU nm and llvm-nm) warns when no symbol is found in the
object. Suppress the stderr.
Fangrui Song mentioned binutils>=2.37 `nm -q` can be used to suppress
"no symbols" [1], and llvm-nm>=13.0.0 supports -q as well.
We cannot use it for now, but note it as a TODO.
[1]: https://sourceware.org/bugzilla/show_bug.cgi?id=27408
Fixes: bbda5ec671 ("kbuild: simplify dependency generation for CONFIG_TRIM_UNUSED_KSYMS")
Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>
Reviewed-by: Nathan Chancellor <nathan@kernel.org>
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>
Masahiro Yamada
Masahiro Yamada