[PATCH 1/3] kbuild: fix false-positive need-builtin

[PATCH 1/3] kbuild: fix false-positive need-builtin

[Masahiro Yamada]

The current implementation of need-builtin is false-positive,
for example, in the following Makefile:

  obj-m := foo/
  obj-y := foo/bar/

..., where foo/built-in.a is not required.

Fixes: f7adc3124da0 ("kbuild: create built-in.o automatically if parent directory wants it")
Signed-off-by: Masahiro Yamada <yamada.masahiro@socionext.com>
---

 scripts/Makefile.build | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/scripts/Makefile.build b/scripts/Makefile.build
index 0d434d0afc0b..3fe0c73e002c 100644
--- a/scripts/Makefile.build
+++ b/scripts/Makefile.build
@@ -487,7 +487,8 @@ targets += $(call intermediate_targets, .asn1.o, .asn1.c .asn1.h) \
 
 PHONY += $(subdir-ym)
 $(subdir-ym):
-	$(Q)$(MAKE) $(build)=$@ need-builtin=$(if $(findstring $@,$(subdir-obj-y)),1)
+	$(Q)$(MAKE) $(build)=$@ \
+	need-builtin=$(if $(filter $@/built-in.a, $(subdir-obj-y)),1)
 
 # Add FORCE to the prequisites of a target to force it to be always rebuilt.
 # ---------------------------------------------------------------------------
-- 
2.17.1

[PATCH 2/3] kbuild: generate modules.order only in directories visited by obj-y/m

[Masahiro Yamada]

The modules.order files in directories visited by the chain of obj-y
or obj-m are merged to the upper-level ones, and become parts of the
top-level modules.order. On the other hand, there is no need to
generate modules.order in directories visited by subdir-y or subdir-m.
They would become orphan anyway.

Signed-off-by: Masahiro Yamada <yamada.masahiro@socionext.com>
---

 scripts/Makefile.build | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/scripts/Makefile.build b/scripts/Makefile.build
index 3fe0c73e002c..37a1d2cd49d4 100644
--- a/scripts/Makefile.build
+++ b/scripts/Makefile.build
@@ -488,7 +488,8 @@ targets += $(call intermediate_targets, .asn1.o, .asn1.c .asn1.h) \
 PHONY += $(subdir-ym)
 $(subdir-ym):
 	$(Q)$(MAKE) $(build)=$@ \
-	need-builtin=$(if $(filter $@/built-in.a, $(subdir-obj-y)),1)
+	need-builtin=$(if $(filter $@/built-in.a, $(subdir-obj-y)),1) \
+	need-modorder=$(if $(need-modorder),$(if $(filter $@/modules.order, $(modorder)),1))
 
 # Add FORCE to the prequisites of a target to force it to be always rebuilt.
 # ---------------------------------------------------------------------------
-- 
2.17.1

[PATCH 3/3] kbuild: show hint if subdir-y/m is used to visit module Makefile

[Masahiro Yamada]

Since commit ff9b45c55b26 ("kbuild: modpost: read modules.order instead
of $(MODVERDIR)/*.mod"), a module is no longer built in the following
pattern:

  [Makefile]
  subdir-y := some-module

  [some-module/Makefile]
  obj-m := some-module.o

You cannot write Makefile this way in upstream because modules.order is
not correctly generated. subdir-y is used to descend to a sub-directory
that builds tools, device trees, etc.

For external modules, the modules order does not matter. So, the
Makefile above was known to work.

I believe the Makefile should be re-written as follows:

  [Makefile]
  obj-m := some-module/

  [some-module/Makefile]
  obj-m := some-module.o

However, people will have no idea if their Makefile suddenly stops
working. In fact, I received questions from multiple people.

Show a warning if obj-m is specified in a Makefile visited by subdir-y
or subdir-m.

Cc: Jan Kiszka <jan.kiszka@siemens.com>
Cc: Tom Stonecypher <thomas.edwardx.stonecypher@intel.com>
Signed-off-by: Masahiro Yamada <yamada.masahiro@socionext.com>
---

 scripts/Makefile.build | 7 +++++++
 1 file changed, 7 insertions(+)

diff --git a/scripts/Makefile.build b/scripts/Makefile.build
index 37a1d2cd49d4..4a26c7ed9198 100644
--- a/scripts/Makefile.build
+++ b/scripts/Makefile.build
@@ -52,6 +52,13 @@ ifndef obj
 $(warning kbuild: Makefile.build is included improperly)
 endif
 
+ifeq ($(need-modorder),)
+ifneq ($(obj-m),)
+$(warning $(patsubst %.o,'%.ko',$(obj-m)) will not be built even though obj-m is specified.)
+$(warning You cannot use subdir-y/m to visit a module Makefile. Use obj-y/m instead.)
+endif
+endif
+
 # ===========================================================================
 
 ifneq ($(strip $(lib-y) $(lib-m) $(lib-)),)
-- 
2.17.1

Re: [PATCH 1/3] kbuild: fix false-positive need-builtin

[Masahiro Yamada]

On Tue, Aug 6, 2019 at 7:03 PM Masahiro Yamada
<yamada.masahiro@socionext.com> wrote:
>
> The current implementation of need-builtin is false-positive,
> for example, in the following Makefile:
>
>   obj-m := foo/
>   obj-y := foo/bar/
>
> ..., where foo/built-in.a is not required.
>
> Fixes: f7adc3124da0 ("kbuild: create built-in.o automatically if parent directory wants it")
> Signed-off-by: Masahiro Yamada <yamada.masahiro@socionext.com>
> ---

Series, applied to linux-kbuild.


>
>  scripts/Makefile.build | 3 ++-
>  1 file changed, 2 insertions(+), 1 deletion(-)
>
> diff --git a/scripts/Makefile.build b/scripts/Makefile.build
> index 0d434d0afc0b..3fe0c73e002c 100644
> --- a/scripts/Makefile.build
> +++ b/scripts/Makefile.build
> @@ -487,7 +487,8 @@ targets += $(call intermediate_targets, .asn1.o, .asn1.c .asn1.h) \
>
>  PHONY += $(subdir-ym)
>  $(subdir-ym):
> -       $(Q)$(MAKE) $(build)=$@ need-builtin=$(if $(findstring $@,$(subdir-obj-y)),1)
> +       $(Q)$(MAKE) $(build)=$@ \
> +       need-builtin=$(if $(filter $@/built-in.a, $(subdir-obj-y)),1)
>
>  # Add FORCE to the prequisites of a target to force it to be always rebuilt.
>  # ---------------------------------------------------------------------------
> --
> 2.17.1
>


-- 
Best Regards
Masahiro Yamada

Re: [PATCH 3/3] kbuild: show hint if subdir-y/m is used to visit module Makefile

[Masahiro Yamada]

On Tue, Aug 6, 2019 at 7:03 PM Masahiro Yamada
<yamada.masahiro@socionext.com> wrote:
>
> Since commit ff9b45c55b26 ("kbuild: modpost: read modules.order instead
> of $(MODVERDIR)/*.mod"), a module is no longer built in the following
> pattern:
>
>   [Makefile]
>   subdir-y := some-module
>
>   [some-module/Makefile]
>   obj-m := some-module.o
>
> You cannot write Makefile this way in upstream because modules.order is
> not correctly generated. subdir-y is used to descend to a sub-directory
> that builds tools, device trees, etc.
>
> For external modules, the modules order does not matter. So, the
> Makefile above was known to work.
>
> I believe the Makefile should be re-written as follows:
>
>   [Makefile]
>   obj-m := some-module/
>
>   [some-module/Makefile]
>   obj-m := some-module.o
>
> However, people will have no idea if their Makefile suddenly stops
> working. In fact, I received questions from multiple people.
>
> Show a warning if obj-m is specified in a Makefile visited by subdir-y
> or subdir-m.
>
> Cc: Jan Kiszka <jan.kiszka@siemens.com>
> Cc: Tom Stonecypher <thomas.edwardx.stonecypher@intel.com>
> Signed-off-by: Masahiro Yamada <yamada.masahiro@socionext.com>
> ---

This produces false-positive warnings for single-targets.
I will fix up as follows:


diff --git a/Makefile b/Makefile
index 0e37ad2f77bf..fac25e279da6 100644
--- a/Makefile
+++ b/Makefile
@@ -1783,7 +1783,7 @@ PHONY += /
 /: ./

 %/: prepare FORCE
-       $(Q)$(MAKE) KBUILD_MODULES=1 $(build)=$(build-dir)
+       $(Q)$(MAKE) KBUILD_MODULES=1 $(build)=$(build-dir) need-modorder=1

 # FIXME Should go into a make.lib or something
 # ===========================================================================



>
>  scripts/Makefile.build | 7 +++++++
>  1 file changed, 7 insertions(+)
>
> diff --git a/scripts/Makefile.build b/scripts/Makefile.build
> index 37a1d2cd49d4..4a26c7ed9198 100644
> --- a/scripts/Makefile.build
> +++ b/scripts/Makefile.build
> @@ -52,6 +52,13 @@ ifndef obj
>  $(warning kbuild: Makefile.build is included improperly)
>  endif
>
> +ifeq ($(need-modorder),)
> +ifneq ($(obj-m),)
> +$(warning $(patsubst %.o,'%.ko',$(obj-m)) will not be built even though obj-m is specified.)
> +$(warning You cannot use subdir-y/m to visit a module Makefile. Use obj-y/m instead.)
> +endif
> +endif
> +
>  # ===========================================================================
>
>  ifneq ($(strip $(lib-y) $(lib-m) $(lib-)),)
> --
> 2.17.1
>


-- 
Best Regards
Masahiro Yamada