[v2,09/29] kbuild: disallow multi-word in M= or KBUILD_EXTMOD
diff mbox series

Message ID 20200524154235.380482-10-masahiroy@kernel.org
State New
Headers show
Series
  • modpost: various fixes, cleanups, optimizations
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Commit Message

Masahiro Yamada May 24, 2020, 3:42 p.m. UTC
$(firstword ...) in scripts/Makefile.modpost was added by commit
3f3fd3c05585 ("[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 0d96fb20b7ed ("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>
---

Changes in v2:
  - Add more commit log

 Makefile                 | 3 +++
 scripts/Makefile.modpost | 2 +-
 2 files changed, 4 insertions(+), 1 deletion(-)

Comments

Masahiro Yamada May 31, 2020, 6:31 p.m. UTC | #1
On Mon, May 25, 2020 at 12:43 AM Masahiro Yamada <masahiroy@kernel.org> wrote:
>
> $(firstword ...) in scripts/Makefile.modpost was added by commit
> 3f3fd3c05585 ("[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 0d96fb20b7ed ("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 patch, applied to linux-kbuild.



> ---
>
> Changes in v2:
>   - Add more commit log
>
>  Makefile                 | 3 +++
>  scripts/Makefile.modpost | 2 +-
>  2 files changed, 4 insertions(+), 1 deletion(-)
>
> diff --git a/Makefile b/Makefile
> index 72eb55a36545..48a2dfaf3bf3 100644
> --- a/Makefile
> +++ b/Makefile
> @@ -218,6 +218,9 @@ ifeq ("$(origin M)", "command line")
>    KBUILD_EXTMOD := $(M)
>  endif
>
> +$(if $(word 2, $(KBUILD_EXTMOD)), \
> +       $(error building multiple external modules is not supported))
> +
>  export KBUILD_CHECKSRC KBUILD_EXTMOD
>
>  extmod-prefix = $(if $(KBUILD_EXTMOD),$(KBUILD_EXTMOD)/)
> diff --git a/scripts/Makefile.modpost b/scripts/Makefile.modpost
> index 957eed6a17a5..b79bf0e30d32 100644
> --- a/scripts/Makefile.modpost
> +++ b/scripts/Makefile.modpost
> @@ -44,7 +44,7 @@ include include/config/auto.conf
>  include scripts/Kbuild.include
>
>  kernelsymfile := $(objtree)/Module.symvers
> -modulesymfile := $(firstword $(KBUILD_EXTMOD))/Module.symvers
> +modulesymfile := $(KBUILD_EXTMOD)/Module.symvers
>
>  MODPOST = scripts/mod/modpost                                                          \
>         $(if $(CONFIG_MODVERSIONS),-m)                                                  \
> --
> 2.25.1
>

Patch
diff mbox series

diff --git a/Makefile b/Makefile
index 72eb55a36545..48a2dfaf3bf3 100644
--- a/Makefile
+++ b/Makefile
@@ -218,6 +218,9 @@  ifeq ("$(origin M)", "command line")
   KBUILD_EXTMOD := $(M)
 endif
 
+$(if $(word 2, $(KBUILD_EXTMOD)), \
+	$(error building multiple external modules is not supported))
+
 export KBUILD_CHECKSRC KBUILD_EXTMOD
 
 extmod-prefix = $(if $(KBUILD_EXTMOD),$(KBUILD_EXTMOD)/)
diff --git a/scripts/Makefile.modpost b/scripts/Makefile.modpost
index 957eed6a17a5..b79bf0e30d32 100644
--- a/scripts/Makefile.modpost
+++ b/scripts/Makefile.modpost
@@ -44,7 +44,7 @@  include include/config/auto.conf
 include scripts/Kbuild.include
 
 kernelsymfile := $(objtree)/Module.symvers
-modulesymfile := $(firstword $(KBUILD_EXTMOD))/Module.symvers
+modulesymfile := $(KBUILD_EXTMOD)/Module.symvers
 
 MODPOST = scripts/mod/modpost								\
 	$(if $(CONFIG_MODVERSIONS),-m)							\