Commit graph

3 commits

Author SHA1 Message Date
Masahiro Yamada
bc7cd2dd1f kbuild: redo fake deps at include/ksym/*.h
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>
2021-09-03 08:17:21 +09:00
Masahiro Yamada
52d83df682 kbuild: Fix 'no symbols' warning when CONFIG_TRIM_UNUSD_KSYMS=y
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>
2021-09-03 08:17:20 +09:00
Masahiro Yamada
bbda5ec671 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>
2018-12-01 23:13:14 +09:00