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kbuild: disallow multi-word in M= or KBUILD_EXTMOD

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$(firstword ...) in scripts/Makefile.modpost was added by commit
3f3fd3c055 ("[PATCH] kbuild: allow multi-word $M in Makefile.modpost")
to build multiple external module directories.

It was a solution to resolve symbol dependencies when an external
module depends on another external module.

Commit 0d96fb20b7 ("kbuild: Add new Kbuild variable
KBUILD_EXTRA_SYMBOLS") introduced another solution by passing symbol
info via KBUILD_EXTRA_SYMBOLS, then broke the multi-word M= support.

  include $(if $(wildcard $(KBUILD_EXTMOD)/Kbuild), \
               $(KBUILD_EXTMOD)/Kbuild, $(KBUILD_EXTMOD)/Makefile)

... does not work if KBUILD_EXTMOD contains multiple words.

This feature has been broken for more than a decade. Remove the
bitrotten code, and stop parsing if M or KBUILD_EXTMOD contains
multiple words.

As Documentation/kbuild/modules.rst explains, if your module depends
on another one, there are two solutions:
  - add a common top-level Kbuild file
  - use KBUILD_EXTRA_SYMBOLS

Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>
This commit is contained in:
Masahiro Yamada 2020-05-25 00:42:15 +09:00
parent 454753d9f6
commit e9e81b6343
2 changed files with 4 additions and 1 deletions
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3
Makefile
View File

@ -218,6 +218,9 @@ ifeq ("$(origin M)", "command line")
KBUILD_EXTMOD := $(M) KBUILD_EXTMOD := $(M)
endif endif
$(if $(word 2, $(KBUILD_EXTMOD)), \
$(error building multiple external modules is not supported))
export KBUILD_CHECKSRC KBUILD_EXTMOD export KBUILD_CHECKSRC KBUILD_EXTMOD
extmod-prefix = $(if $(KBUILD_EXTMOD),$(KBUILD_EXTMOD)/) extmod-prefix = $(if $(KBUILD_EXTMOD),$(KBUILD_EXTMOD)/)

2
scripts/Makefile.modpost
View File

@ -44,7 +44,7 @@ include include/config/auto.conf
include scripts/Kbuild.include include scripts/Kbuild.include
kernelsymfile := $(objtree)/Module.symvers kernelsymfile := $(objtree)/Module.symvers
modulesymfile := $(firstword $(KBUILD_EXTMOD))/Module.symvers modulesymfile := $(KBUILD_EXTMOD)/Module.symvers
MODPOST = scripts/mod/modpost \ MODPOST = scripts/mod/modpost \
$(if $(CONFIG_MODVERSIONS),-m) \ $(if $(CONFIG_MODVERSIONS),-m) \