diff mbox series

kbuild: add extra-y to targets-for-modules

Message ID 20201103054425.59251-1-chao.wang@ucloud.cn (mailing list archive)
State New
Headers show
Series kbuild: add extra-y to targets-for-modules | expand

Commit Message

WANG Chao Nov. 3, 2020, 5:44 a.m. UTC
extra-y target doesn't build for 'make M=...' since commit 6212804f2d78
("kbuild: do not create built-in objects for external module builds").

This especially breaks kpatch, which is using 'extra-y := kpatch.lds'
and 'make M=...' to build livepatch patch module.

Add extra-y to targets-for-modules so that such kind of build works
properly.

Signed-off-by: WANG Chao <chao.wang@ucloud.cn>
---
 scripts/Makefile.build | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

Comments

Masahiro Yamada Nov. 23, 2020, 5:23 a.m. UTC | #1
On Tue, Nov 3, 2020 at 3:23 PM WANG Chao <chao.wang@ucloud.cn> wrote:
>
> extra-y target doesn't build for 'make M=...' since commit 6212804f2d78
> ("kbuild: do not create built-in objects for external module builds").
>
> This especially breaks kpatch, which is using 'extra-y := kpatch.lds'
> and 'make M=...' to build livepatch patch module.
>
> Add extra-y to targets-for-modules so that such kind of build works
> properly.
>
> Signed-off-by: WANG Chao <chao.wang@ucloud.cn>
> ---
>  scripts/Makefile.build | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/scripts/Makefile.build b/scripts/Makefile.build
> index ae647379b579..0113a042d643 100644
> --- a/scripts/Makefile.build
> +++ b/scripts/Makefile.build
> @@ -86,7 +86,7 @@ ifdef need-builtin
>  targets-for-builtin += $(obj)/built-in.a
>  endif
>
> -targets-for-modules := $(patsubst %.o, %.mod, $(filter %.o, $(obj-m)))
> +targets-for-modules := $(extra-y) $(patsubst %.o, %.mod, $(filter %.o, $(obj-m)))
>
>  ifdef need-modorder
>  targets-for-modules += $(obj)/modules.order
> --
> 2.29.1
>

NACK.

Please fix your Makefile.

Hint:
https://patchwork.kernel.org/project/linux-kbuild/patch/20201123045403.63402-6-masahiroy@kernel.org/


Probably what you should use is 'targets'.
WANG Chao Nov. 23, 2020, 3:04 p.m. UTC | #2
On 11/23/20 at 02:23P, Masahiro Yamada wrote:
> On Tue, Nov 3, 2020 at 3:23 PM WANG Chao <chao.wang@ucloud.cn> wrote:
> >
> > extra-y target doesn't build for 'make M=...' since commit 6212804f2d78
> > ("kbuild: do not create built-in objects for external module builds").
> >
> > This especially breaks kpatch, which is using 'extra-y := kpatch.lds'
> > and 'make M=...' to build livepatch patch module.
> >
> > Add extra-y to targets-for-modules so that such kind of build works
> > properly.
> >
> > Signed-off-by: WANG Chao <chao.wang@ucloud.cn>
> > ---
> >  scripts/Makefile.build | 2 +-
> >  1 file changed, 1 insertion(+), 1 deletion(-)
> >
> > diff --git a/scripts/Makefile.build b/scripts/Makefile.build
> > index ae647379b579..0113a042d643 100644
> > --- a/scripts/Makefile.build
> > +++ b/scripts/Makefile.build
> > @@ -86,7 +86,7 @@ ifdef need-builtin
> >  targets-for-builtin += $(obj)/built-in.a
> >  endif
> >
> > -targets-for-modules := $(patsubst %.o, %.mod, $(filter %.o, $(obj-m)))
> > +targets-for-modules := $(extra-y) $(patsubst %.o, %.mod, $(filter %.o, $(obj-m)))
> >
> >  ifdef need-modorder
> >  targets-for-modules += $(obj)/modules.order
> > --
> > 2.29.1
> >
> 
> NACK.
> 
> Please fix your Makefile.
> 
> Hint:
> https://patchwork.kernel.org/project/linux-kbuild/patch/20201123045403.63402-6-masahiroy@kernel.org/
> 
> 
> Probably what you should use is 'targets'.

I tried with 'targets' and 'always-y'. Both doesn't work for me.

I narraw it down to the following example:

cat > Makefile << _EOF_
obj-m += foo.o

ldflags-y += -T $(src)/kpatch.lds
always-y += kpatch.lds

foo-objs += bar.o

all:
	make -C /lib/modules/$(shell uname -r)/build M=$(PWD)
clean:
	make -C /lib/modules/$(shell uname -r)/build M=$(PWD) clean
_EOF_

Take a look into scripts/Makefile.build:488:

__build: $(if $(KBUILD_BUILTIN), $(targets-for-builtin)) \
	 $(if $(KBUILD_MODULES), $(targets-for-modules)) \
	 $(subdir-ym) $(always-y)
	@:

'always-y' is built after 'targets-for-modules'. This makes
'targets-for-modules' fails because kpatch.lds isn't there.

For 'targets', in case of OOT, does not seem to be useful.

What change do you suggest to make to fix this kind of Makefile?

Thanks,
WANG Chao
Masahiro Yamada Nov. 25, 2020, 1:42 p.m. UTC | #3
On Tue, Nov 24, 2020 at 12:05 AM WANG Chao <chao.wang@ucloud.cn> wrote:
>
> On 11/23/20 at 02:23P, Masahiro Yamada wrote:
> > On Tue, Nov 3, 2020 at 3:23 PM WANG Chao <chao.wang@ucloud.cn> wrote:
> > >
> > > extra-y target doesn't build for 'make M=...' since commit 6212804f2d78
> > > ("kbuild: do not create built-in objects for external module builds").
> > >
> > > This especially breaks kpatch, which is using 'extra-y := kpatch.lds'
> > > and 'make M=...' to build livepatch patch module.
> > >
> > > Add extra-y to targets-for-modules so that such kind of build works
> > > properly.
> > >
> > > Signed-off-by: WANG Chao <chao.wang@ucloud.cn>
> > > ---
> > >  scripts/Makefile.build | 2 +-
> > >  1 file changed, 1 insertion(+), 1 deletion(-)
> > >
> > > diff --git a/scripts/Makefile.build b/scripts/Makefile.build
> > > index ae647379b579..0113a042d643 100644
> > > --- a/scripts/Makefile.build
> > > +++ b/scripts/Makefile.build
> > > @@ -86,7 +86,7 @@ ifdef need-builtin
> > >  targets-for-builtin += $(obj)/built-in.a
> > >  endif
> > >
> > > -targets-for-modules := $(patsubst %.o, %.mod, $(filter %.o, $(obj-m)))
> > > +targets-for-modules := $(extra-y) $(patsubst %.o, %.mod, $(filter %.o, $(obj-m)))
> > >
> > >  ifdef need-modorder
> > >  targets-for-modules += $(obj)/modules.order
> > > --
> > > 2.29.1
> > >
> >
> > NACK.
> >
> > Please fix your Makefile.
> >
> > Hint:
> > https://patchwork.kernel.org/project/linux-kbuild/patch/20201123045403.63402-6-masahiroy@kernel.org/
> >
> >
> > Probably what you should use is 'targets'.
>
> I tried with 'targets' and 'always-y'. Both doesn't work for me.
>
> I narraw it down to the following example:
>
> cat > Makefile << _EOF_
> obj-m += foo.o
>
> ldflags-y += -T $(src)/kpatch.lds
> always-y += kpatch.lds
>
> foo-objs += bar.o
>
> all:
>         make -C /lib/modules/$(shell uname -r)/build M=$(PWD)
> clean:
>         make -C /lib/modules/$(shell uname -r)/build M=$(PWD) clean
> _EOF_
>
> Take a look into scripts/Makefile.build:488:
>
> __build: $(if $(KBUILD_BUILTIN), $(targets-for-builtin)) \
>          $(if $(KBUILD_MODULES), $(targets-for-modules)) \
>          $(subdir-ym) $(always-y)
>         @:
>
> 'always-y' is built after 'targets-for-modules'. This makes
> 'targets-for-modules' fails because kpatch.lds isn't there.


Heh, you rely on the targets built from left to right,
and you have never thought Make supports the parallel option -j.


You need to specify the dependency if you expect objects
are built in the particular order.

However, in this case, using ldflags-y looks wrong
in the first place.

The linker script is used when combining the object
as well as the final link of *.ko


> For 'targets', in case of OOT, does not seem to be useful.
>
> What change do you suggest to make to fix this kind of Makefile?
>
> Thanks,
> WANG Chao
WANG Chao Dec. 8, 2020, 9:20 a.m. UTC | #4
Sorry for the late reply.

On 11/25/20 at 10:42P, Masahiro Yamada wrote:
> On Tue, Nov 24, 2020 at 12:05 AM WANG Chao <chao.wang@ucloud.cn> wrote:
> >
> > On 11/23/20 at 02:23P, Masahiro Yamada wrote:
> > > On Tue, Nov 3, 2020 at 3:23 PM WANG Chao <chao.wang@ucloud.cn> wrote:
> > > >
> > > > extra-y target doesn't build for 'make M=...' since commit 6212804f2d78
> > > > ("kbuild: do not create built-in objects for external module builds").
> > > >
> > > > This especially breaks kpatch, which is using 'extra-y := kpatch.lds'
> > > > and 'make M=...' to build livepatch patch module.
> > > >
> > > > Add extra-y to targets-for-modules so that such kind of build works
> > > > properly.
> > > >
> > > > Signed-off-by: WANG Chao <chao.wang@ucloud.cn>
> > > > ---
> > > >  scripts/Makefile.build | 2 +-
> > > >  1 file changed, 1 insertion(+), 1 deletion(-)
> > > >
> > > > diff --git a/scripts/Makefile.build b/scripts/Makefile.build
> > > > index ae647379b579..0113a042d643 100644
> > > > --- a/scripts/Makefile.build
> > > > +++ b/scripts/Makefile.build
> > > > @@ -86,7 +86,7 @@ ifdef need-builtin
> > > >  targets-for-builtin += $(obj)/built-in.a
> > > >  endif
> > > >
> > > > -targets-for-modules := $(patsubst %.o, %.mod, $(filter %.o, $(obj-m)))
> > > > +targets-for-modules := $(extra-y) $(patsubst %.o, %.mod, $(filter %.o, $(obj-m)))
> > > >
> > > >  ifdef need-modorder
> > > >  targets-for-modules += $(obj)/modules.order
> > > > --
> > > > 2.29.1
> > > >
> > >
> > > NACK.
> > >
> > > Please fix your Makefile.
> > >
> > > Hint:
> > > https://patchwork.kernel.org/project/linux-kbuild/patch/20201123045403.63402-6-masahiroy@kernel.org/
> > >
> > >
> > > Probably what you should use is 'targets'.
> >
> > I tried with 'targets' and 'always-y'. Both doesn't work for me.
> >
> > I narraw it down to the following example:
> >
> > cat > Makefile << _EOF_
> > obj-m += foo.o
> >
> > ldflags-y += -T $(src)/kpatch.lds
> > always-y += kpatch.lds
> >
> > foo-objs += bar.o
> >
> > all:
> >         make -C /lib/modules/$(shell uname -r)/build M=$(PWD)
> > clean:
> >         make -C /lib/modules/$(shell uname -r)/build M=$(PWD) clean
> > _EOF_
> >
> > Take a look into scripts/Makefile.build:488:
> >
> > __build: $(if $(KBUILD_BUILTIN), $(targets-for-builtin)) \
> >          $(if $(KBUILD_MODULES), $(targets-for-modules)) \
> >          $(subdir-ym) $(always-y)
> >         @:
> >
> > 'always-y' is built after 'targets-for-modules'. This makes
> > 'targets-for-modules' fails because kpatch.lds isn't there.
> 
> 
> Heh, you rely on the targets built from left to right,
> and you have never thought Make supports the parallel option -j.

You're right. I missed that.

> 
> 
> You need to specify the dependency if you expect objects
> are built in the particular order.
> 
> However, in this case, using ldflags-y looks wrong
> in the first place.
> 
> The linker script is used when combining the object
> as well as the final link of *.ko

I don't have a clean fix to kpatch right now.

I'm looping kpatch forks in. They're also looking at this right now:

https://github.com/dynup/kpatch/pull/1149

Thanks
WANG Chao

> 
> 
> > For 'targets', in case of OOT, does not seem to be useful.
> >
> > What change do you suggest to make to fix this kind of Makefile?
> >
> > Thanks,
> > WANG Chao
> 
> 
> 
> -- 
> Best Regards
> Masahiro Yamada
>
Artem Savkov Dec. 8, 2020, 2:31 p.m. UTC | #5
On Tue, Dec 08, 2020 at 05:20:35PM +0800, WANG Chao wrote:
> Sorry for the late reply.
> 
> On 11/25/20 at 10:42P, Masahiro Yamada wrote:
> > On Tue, Nov 24, 2020 at 12:05 AM WANG Chao <chao.wang@ucloud.cn> wrote:
> > >
> > > On 11/23/20 at 02:23P, Masahiro Yamada wrote:
> > > > On Tue, Nov 3, 2020 at 3:23 PM WANG Chao <chao.wang@ucloud.cn> wrote:
> > > > >
> > > > > extra-y target doesn't build for 'make M=...' since commit 6212804f2d78
> > > > > ("kbuild: do not create built-in objects for external module builds").
> > > > >
> > > > > This especially breaks kpatch, which is using 'extra-y := kpatch.lds'
> > > > > and 'make M=...' to build livepatch patch module.
> > > > >
> > > > > Add extra-y to targets-for-modules so that such kind of build works
> > > > > properly.
> > > > >
> > > > > Signed-off-by: WANG Chao <chao.wang@ucloud.cn>
> > > > > ---
> > > > >  scripts/Makefile.build | 2 +-
> > > > >  1 file changed, 1 insertion(+), 1 deletion(-)
> > > > >
> > > > > diff --git a/scripts/Makefile.build b/scripts/Makefile.build
> > > > > index ae647379b579..0113a042d643 100644
> > > > > --- a/scripts/Makefile.build
> > > > > +++ b/scripts/Makefile.build
> > > > > @@ -86,7 +86,7 @@ ifdef need-builtin
> > > > >  targets-for-builtin += $(obj)/built-in.a
> > > > >  endif
> > > > >
> > > > > -targets-for-modules := $(patsubst %.o, %.mod, $(filter %.o, $(obj-m)))
> > > > > +targets-for-modules := $(extra-y) $(patsubst %.o, %.mod, $(filter %.o, $(obj-m)))
> > > > >
> > > > >  ifdef need-modorder
> > > > >  targets-for-modules += $(obj)/modules.order
> > > > > --
> > > > > 2.29.1
> > > > >
> > > >
> > > > NACK.
> > > >
> > > > Please fix your Makefile.
> > > >
> > > > Hint:
> > > > https://patchwork.kernel.org/project/linux-kbuild/patch/20201123045403.63402-6-masahiroy@kernel.org/
> > > >
> > > >
> > > > Probably what you should use is 'targets'.
> > >
> > > I tried with 'targets' and 'always-y'. Both doesn't work for me.
> > >
> > > I narraw it down to the following example:
> > >
> > > cat > Makefile << _EOF_
> > > obj-m += foo.o
> > >
> > > ldflags-y += -T $(src)/kpatch.lds
> > > always-y += kpatch.lds
> > >
> > > foo-objs += bar.o
> > >
> > > all:
> > >         make -C /lib/modules/$(shell uname -r)/build M=$(PWD)
> > > clean:
> > >         make -C /lib/modules/$(shell uname -r)/build M=$(PWD) clean
> > > _EOF_
> > >
> > > Take a look into scripts/Makefile.build:488:
> > >
> > > __build: $(if $(KBUILD_BUILTIN), $(targets-for-builtin)) \
> > >          $(if $(KBUILD_MODULES), $(targets-for-modules)) \
> > >          $(subdir-ym) $(always-y)
> > >         @:
> > >
> > > 'always-y' is built after 'targets-for-modules'. This makes
> > > 'targets-for-modules' fails because kpatch.lds isn't there.
> > 
> > 
> > Heh, you rely on the targets built from left to right,
> > and you have never thought Make supports the parallel option -j.
> 
> You're right. I missed that.
> 
> > 
> > 
> > You need to specify the dependency if you expect objects
> > are built in the particular order.
> > 
> > However, in this case, using ldflags-y looks wrong
> > in the first place.
> > 
> > The linker script is used when combining the object
> > as well as the final link of *.ko

We want linker script to be used on both those steps, otherwise modpost
fails.

It looks like the right thing to do here is leave ldflags-y in, get rid
of always-y/extra-y altogether and specify our linker script as a
dependency for the object.

> I don't have a clean fix to kpatch right now.
> 
> I'm looping kpatch forks in. They're also looking at this right now:
> 
> https://github.com/dynup/kpatch/pull/1149
> 
> Thanks
> WANG Chao
> 
> > 
> > 
> > > For 'targets', in case of OOT, does not seem to be useful.
> > >
> > > What change do you suggest to make to fix this kind of Makefile?
> > >
> > > Thanks,
> > > WANG Chao
> > 
> > 
> > 
> > -- 
> > Best Regards
> > Masahiro Yamada
> > 
>
Masahiro Yamada Dec. 16, 2020, 6:14 a.m. UTC | #6
On Tue, Dec 8, 2020 at 11:31 PM Artem Savkov <artem.savkov@gmail.com> wrote:
>
> On Tue, Dec 08, 2020 at 05:20:35PM +0800, WANG Chao wrote:
> > Sorry for the late reply.
> >
> > On 11/25/20 at 10:42P, Masahiro Yamada wrote:
> > > On Tue, Nov 24, 2020 at 12:05 AM WANG Chao <chao.wang@ucloud.cn> wrote:
> > > >
> > > > On 11/23/20 at 02:23P, Masahiro Yamada wrote:
> > > > > On Tue, Nov 3, 2020 at 3:23 PM WANG Chao <chao.wang@ucloud.cn> wrote:
> > > > > >
> > > > > > extra-y target doesn't build for 'make M=...' since commit 6212804f2d78
> > > > > > ("kbuild: do not create built-in objects for external module builds").
> > > > > >
> > > > > > This especially breaks kpatch, which is using 'extra-y := kpatch.lds'
> > > > > > and 'make M=...' to build livepatch patch module.
> > > > > >
> > > > > > Add extra-y to targets-for-modules so that such kind of build works
> > > > > > properly.
> > > > > >
> > > > > > Signed-off-by: WANG Chao <chao.wang@ucloud.cn>
> > > > > > ---
> > > > > >  scripts/Makefile.build | 2 +-
> > > > > >  1 file changed, 1 insertion(+), 1 deletion(-)
> > > > > >
> > > > > > diff --git a/scripts/Makefile.build b/scripts/Makefile.build
> > > > > > index ae647379b579..0113a042d643 100644
> > > > > > --- a/scripts/Makefile.build
> > > > > > +++ b/scripts/Makefile.build
> > > > > > @@ -86,7 +86,7 @@ ifdef need-builtin
> > > > > >  targets-for-builtin += $(obj)/built-in.a
> > > > > >  endif
> > > > > >
> > > > > > -targets-for-modules := $(patsubst %.o, %.mod, $(filter %.o, $(obj-m)))
> > > > > > +targets-for-modules := $(extra-y) $(patsubst %.o, %.mod, $(filter %.o, $(obj-m)))
> > > > > >
> > > > > >  ifdef need-modorder
> > > > > >  targets-for-modules += $(obj)/modules.order
> > > > > > --
> > > > > > 2.29.1
> > > > > >
> > > > >
> > > > > NACK.
> > > > >
> > > > > Please fix your Makefile.
> > > > >
> > > > > Hint:
> > > > > https://patchwork.kernel.org/project/linux-kbuild/patch/20201123045403.63402-6-masahiroy@kernel.org/
> > > > >
> > > > >
> > > > > Probably what you should use is 'targets'.
> > > >
> > > > I tried with 'targets' and 'always-y'. Both doesn't work for me.
> > > >
> > > > I narraw it down to the following example:
> > > >
> > > > cat > Makefile << _EOF_
> > > > obj-m += foo.o
> > > >
> > > > ldflags-y += -T $(src)/kpatch.lds
> > > > always-y += kpatch.lds
> > > >
> > > > foo-objs += bar.o
> > > >
> > > > all:
> > > >         make -C /lib/modules/$(shell uname -r)/build M=$(PWD)
> > > > clean:
> > > >         make -C /lib/modules/$(shell uname -r)/build M=$(PWD) clean
> > > > _EOF_
> > > >
> > > > Take a look into scripts/Makefile.build:488:
> > > >
> > > > __build: $(if $(KBUILD_BUILTIN), $(targets-for-builtin)) \
> > > >          $(if $(KBUILD_MODULES), $(targets-for-modules)) \
> > > >          $(subdir-ym) $(always-y)
> > > >         @:
> > > >
> > > > 'always-y' is built after 'targets-for-modules'. This makes
> > > > 'targets-for-modules' fails because kpatch.lds isn't there.
> > >
> > >
> > > Heh, you rely on the targets built from left to right,
> > > and you have never thought Make supports the parallel option -j.
> >
> > You're right. I missed that.
> >
> > >
> > >
> > > You need to specify the dependency if you expect objects
> > > are built in the particular order.
> > >
> > > However, in this case, using ldflags-y looks wrong
> > > in the first place.
> > >
> > > The linker script is used when combining the object
> > > as well as the final link of *.ko
>
> We want linker script to be used on both those steps, otherwise modpost
> fails.


In that case, does the following work?
(untested)



diff --git a/kmod/patch/Makefile b/kmod/patch/Makefile
index e017b17..02d4c66 100644
--- a/kmod/patch/Makefile
+++ b/kmod/patch/Makefile
@@ -12,7 +12,9 @@ endif

 obj-m += $(KPATCH_NAME).o
 ldflags-y += -T $(src)/kpatch.lds
-extra-y := kpatch.lds
+targets += kpatch.lds
+
+$(obj)/$(KPATCH_NAME).o: $(obj)/kpatch.lds

 $(KPATCH_NAME)-objs += patch-hook.o output.o





>
> It looks like the right thing to do here is leave ldflags-y in, get rid
> of always-y/extra-y altogether and specify our linker script as a
> dependency for the object.
>
> > I don't have a clean fix to kpatch right now.
> >
> > I'm looping kpatch forks in. They're also looking at this right now:
> >
> > https://github.com/dynup/kpatch/pull/1149
> >
> > Thanks
> > WANG Chao
> >
> > >
> > >
> > > > For 'targets', in case of OOT, does not seem to be useful.
> > > >
> > > > What change do you suggest to make to fix this kind of Makefile?
> > > >
> > > > Thanks,
> > > > WANG Chao
> > >
> > >
> > >
> > > --
> > > Best Regards
> > > Masahiro Yamada
> > >
> >
>
> --
> Regards,
>   Artem Savkov
Joe Lawrence Dec. 16, 2020, 11:04 p.m. UTC | #7
On 12/16/20 1:14 AM, Masahiro Yamada wrote:
> On Tue, Dec 8, 2020 at 11:31 PM Artem Savkov <artem.savkov@gmail.com> wrote:
>>
>> On Tue, Dec 08, 2020 at 05:20:35PM +0800, WANG Chao wrote:
>>> Sorry for the late reply.
>>>
>>> On 11/25/20 at 10:42P, Masahiro Yamada wrote:
>>>> On Tue, Nov 24, 2020 at 12:05 AM WANG Chao <chao.wang@ucloud.cn> wrote:
>>>>>
>>>>> On 11/23/20 at 02:23P, Masahiro Yamada wrote:
>>>>>> On Tue, Nov 3, 2020 at 3:23 PM WANG Chao <chao.wang@ucloud.cn> wrote:
>>>>>>>
>>>>>>> extra-y target doesn't build for 'make M=...' since commit 6212804f2d78
>>>>>>> ("kbuild: do not create built-in objects for external module builds").
>>>>>>>
>>>>>>> This especially breaks kpatch, which is using 'extra-y := kpatch.lds'
>>>>>>> and 'make M=...' to build livepatch patch module.
>>>>>>>
>>>>>>> Add extra-y to targets-for-modules so that such kind of build works
>>>>>>> properly.
>>>>>>>
>>>>>>> Signed-off-by: WANG Chao <chao.wang@ucloud.cn>
>>>>>>> ---
>>>>>>>   scripts/Makefile.build | 2 +-
>>>>>>>   1 file changed, 1 insertion(+), 1 deletion(-)
>>>>>>>
>>>>>>> diff --git a/scripts/Makefile.build b/scripts/Makefile.build
>>>>>>> index ae647379b579..0113a042d643 100644
>>>>>>> --- a/scripts/Makefile.build
>>>>>>> +++ b/scripts/Makefile.build
>>>>>>> @@ -86,7 +86,7 @@ ifdef need-builtin
>>>>>>>   targets-for-builtin += $(obj)/built-in.a
>>>>>>>   endif
>>>>>>>
>>>>>>> -targets-for-modules := $(patsubst %.o, %.mod, $(filter %.o, $(obj-m)))
>>>>>>> +targets-for-modules := $(extra-y) $(patsubst %.o, %.mod, $(filter %.o, $(obj-m)))
>>>>>>>
>>>>>>>   ifdef need-modorder
>>>>>>>   targets-for-modules += $(obj)/modules.order
>>>>>>> --
>>>>>>> 2.29.1
>>>>>>>
>>>>>>
>>>>>> NACK.
>>>>>>
>>>>>> Please fix your Makefile.
>>>>>>
>>>>>> Hint:
>>>>>> https://patchwork.kernel.org/project/linux-kbuild/patch/20201123045403.63402-6-masahiroy@kernel.org/
>>>>>>
>>>>>>
>>>>>> Probably what you should use is 'targets'.
>>>>>
>>>>> I tried with 'targets' and 'always-y'. Both doesn't work for me.
>>>>>
>>>>> I narraw it down to the following example:
>>>>>
>>>>> cat > Makefile << _EOF_
>>>>> obj-m += foo.o
>>>>>
>>>>> ldflags-y += -T $(src)/kpatch.lds
>>>>> always-y += kpatch.lds
>>>>>
>>>>> foo-objs += bar.o
>>>>>
>>>>> all:
>>>>>          make -C /lib/modules/$(shell uname -r)/build M=$(PWD)
>>>>> clean:
>>>>>          make -C /lib/modules/$(shell uname -r)/build M=$(PWD) clean
>>>>> _EOF_
>>>>>
>>>>> Take a look into scripts/Makefile.build:488:
>>>>>
>>>>> __build: $(if $(KBUILD_BUILTIN), $(targets-for-builtin)) \
>>>>>           $(if $(KBUILD_MODULES), $(targets-for-modules)) \
>>>>>           $(subdir-ym) $(always-y)
>>>>>          @:
>>>>>
>>>>> 'always-y' is built after 'targets-for-modules'. This makes
>>>>> 'targets-for-modules' fails because kpatch.lds isn't there.
>>>>
>>>>
>>>> Heh, you rely on the targets built from left to right,
>>>> and you have never thought Make supports the parallel option -j.
>>>
>>> You're right. I missed that.
>>>
>>>>
>>>>
>>>> You need to specify the dependency if you expect objects
>>>> are built in the particular order.
>>>>
>>>> However, in this case, using ldflags-y looks wrong
>>>> in the first place.
>>>>
>>>> The linker script is used when combining the object
>>>> as well as the final link of *.ko
>>
>> We want linker script to be used on both those steps, otherwise modpost
>> fails.
> 
> 
> In that case, does the following work?
> (untested)
> 
> 
> 
> diff --git a/kmod/patch/Makefile b/kmod/patch/Makefile
> index e017b17..02d4c66 100644
> --- a/kmod/patch/Makefile
> +++ b/kmod/patch/Makefile
> @@ -12,7 +12,9 @@ endif
> 
>   obj-m += $(KPATCH_NAME).o
>   ldflags-y += -T $(src)/kpatch.lds
> -extra-y := kpatch.lds
> +targets += kpatch.lds
> +
> +$(obj)/$(KPATCH_NAME).o: $(obj)/kpatch.lds
> 
>   $(KPATCH_NAME)-objs += patch-hook.o output.o
> 

Hi Masahiro,

Yeah this is more or less what Artem came up with:
https://github.com/dynup/kpatch/pull/1149

though we hadn't added kpatch.lds to targets.  Is there documentation 
somewhere on what effect "targets" has for out-of-tree builds?

Thanks,

-- Joe
Masahiro Yamada Dec. 17, 2020, 8:26 a.m. UTC | #8
On Thu, Dec 17, 2020 at 8:04 AM Joe Lawrence <joe.lawrence@redhat.com> wrote:
>
> On 12/16/20 1:14 AM, Masahiro Yamada wrote:
> > On Tue, Dec 8, 2020 at 11:31 PM Artem Savkov <artem.savkov@gmail.com> wrote:
> >>
> >> On Tue, Dec 08, 2020 at 05:20:35PM +0800, WANG Chao wrote:
> >>> Sorry for the late reply.
> >>>
> >>> On 11/25/20 at 10:42P, Masahiro Yamada wrote:
> >>>> On Tue, Nov 24, 2020 at 12:05 AM WANG Chao <chao.wang@ucloud.cn> wrote:
> >>>>>
> >>>>> On 11/23/20 at 02:23P, Masahiro Yamada wrote:
> >>>>>> On Tue, Nov 3, 2020 at 3:23 PM WANG Chao <chao.wang@ucloud.cn> wrote:
> >>>>>>>
> >>>>>>> extra-y target doesn't build for 'make M=...' since commit 6212804f2d78
> >>>>>>> ("kbuild: do not create built-in objects for external module builds").
> >>>>>>>
> >>>>>>> This especially breaks kpatch, which is using 'extra-y := kpatch.lds'
> >>>>>>> and 'make M=...' to build livepatch patch module.
> >>>>>>>
> >>>>>>> Add extra-y to targets-for-modules so that such kind of build works
> >>>>>>> properly.
> >>>>>>>
> >>>>>>> Signed-off-by: WANG Chao <chao.wang@ucloud.cn>
> >>>>>>> ---
> >>>>>>>   scripts/Makefile.build | 2 +-
> >>>>>>>   1 file changed, 1 insertion(+), 1 deletion(-)
> >>>>>>>
> >>>>>>> diff --git a/scripts/Makefile.build b/scripts/Makefile.build
> >>>>>>> index ae647379b579..0113a042d643 100644
> >>>>>>> --- a/scripts/Makefile.build
> >>>>>>> +++ b/scripts/Makefile.build
> >>>>>>> @@ -86,7 +86,7 @@ ifdef need-builtin
> >>>>>>>   targets-for-builtin += $(obj)/built-in.a
> >>>>>>>   endif
> >>>>>>>
> >>>>>>> -targets-for-modules := $(patsubst %.o, %.mod, $(filter %.o, $(obj-m)))
> >>>>>>> +targets-for-modules := $(extra-y) $(patsubst %.o, %.mod, $(filter %.o, $(obj-m)))
> >>>>>>>
> >>>>>>>   ifdef need-modorder
> >>>>>>>   targets-for-modules += $(obj)/modules.order
> >>>>>>> --
> >>>>>>> 2.29.1
> >>>>>>>
> >>>>>>
> >>>>>> NACK.
> >>>>>>
> >>>>>> Please fix your Makefile.
> >>>>>>
> >>>>>> Hint:
> >>>>>> https://patchwork.kernel.org/project/linux-kbuild/patch/20201123045403.63402-6-masahiroy@kernel.org/
> >>>>>>
> >>>>>>
> >>>>>> Probably what you should use is 'targets'.
> >>>>>
> >>>>> I tried with 'targets' and 'always-y'. Both doesn't work for me.
> >>>>>
> >>>>> I narraw it down to the following example:
> >>>>>
> >>>>> cat > Makefile << _EOF_
> >>>>> obj-m += foo.o
> >>>>>
> >>>>> ldflags-y += -T $(src)/kpatch.lds
> >>>>> always-y += kpatch.lds
> >>>>>
> >>>>> foo-objs += bar.o
> >>>>>
> >>>>> all:
> >>>>>          make -C /lib/modules/$(shell uname -r)/build M=$(PWD)
> >>>>> clean:
> >>>>>          make -C /lib/modules/$(shell uname -r)/build M=$(PWD) clean
> >>>>> _EOF_
> >>>>>
> >>>>> Take a look into scripts/Makefile.build:488:
> >>>>>
> >>>>> __build: $(if $(KBUILD_BUILTIN), $(targets-for-builtin)) \
> >>>>>           $(if $(KBUILD_MODULES), $(targets-for-modules)) \
> >>>>>           $(subdir-ym) $(always-y)
> >>>>>          @:
> >>>>>
> >>>>> 'always-y' is built after 'targets-for-modules'. This makes
> >>>>> 'targets-for-modules' fails because kpatch.lds isn't there.
> >>>>
> >>>>
> >>>> Heh, you rely on the targets built from left to right,
> >>>> and you have never thought Make supports the parallel option -j.
> >>>
> >>> You're right. I missed that.
> >>>
> >>>>
> >>>>
> >>>> You need to specify the dependency if you expect objects
> >>>> are built in the particular order.
> >>>>
> >>>> However, in this case, using ldflags-y looks wrong
> >>>> in the first place.
> >>>>
> >>>> The linker script is used when combining the object
> >>>> as well as the final link of *.ko
> >>
> >> We want linker script to be used on both those steps, otherwise modpost
> >> fails.
> >
> >
> > In that case, does the following work?
> > (untested)
> >
> >
> >
> > diff --git a/kmod/patch/Makefile b/kmod/patch/Makefile
> > index e017b17..02d4c66 100644
> > --- a/kmod/patch/Makefile
> > +++ b/kmod/patch/Makefile
> > @@ -12,7 +12,9 @@ endif
> >
> >   obj-m += $(KPATCH_NAME).o
> >   ldflags-y += -T $(src)/kpatch.lds
> > -extra-y := kpatch.lds
> > +targets += kpatch.lds
> > +
> > +$(obj)/$(KPATCH_NAME).o: $(obj)/kpatch.lds
> >
> >   $(KPATCH_NAME)-objs += patch-hook.o output.o
> >
>
> Hi Masahiro,
>
> Yeah this is more or less what Artem came up with:
> https://github.com/dynup/kpatch/pull/1149
>
> though we hadn't added kpatch.lds to targets.  Is there documentation
> somewhere on what effect "targets" has for out-of-tree builds?
>
> Thanks,
>
> -- Joe
>


Please try the rebuild without changing any source code.

If kpatch.lds is needlessly rebuilt, you need to add
it to 'targets'.


In linux-next, this is documented.

Documentation/kbuild/makefile.rst:

        Any target that utilizes if_changed must be listed in $(targets),
        otherwise the command line check will fail, and the target will
        always be built.
Artem Savkov Dec. 17, 2020, 12:04 p.m. UTC | #9
On Thu, Dec 17, 2020 at 05:26:07PM +0900, Masahiro Yamada wrote:
> On Thu, Dec 17, 2020 at 8:04 AM Joe Lawrence <joe.lawrence@redhat.com> wrote:
> >
> > On 12/16/20 1:14 AM, Masahiro Yamada wrote:
> > > On Tue, Dec 8, 2020 at 11:31 PM Artem Savkov <artem.savkov@gmail.com> wrote:
> > >>
> > >> On Tue, Dec 08, 2020 at 05:20:35PM +0800, WANG Chao wrote:
> > >>> Sorry for the late reply.
> > >>>
> > >>> On 11/25/20 at 10:42P, Masahiro Yamada wrote:
> > >>>> On Tue, Nov 24, 2020 at 12:05 AM WANG Chao <chao.wang@ucloud.cn> wrote:
> > >>>>>
> > >>>>> On 11/23/20 at 02:23P, Masahiro Yamada wrote:
> > >>>>>> On Tue, Nov 3, 2020 at 3:23 PM WANG Chao <chao.wang@ucloud.cn> wrote:
> > >>>>>>>
> > >>>>>>> extra-y target doesn't build for 'make M=...' since commit 6212804f2d78
> > >>>>>>> ("kbuild: do not create built-in objects for external module builds").
> > >>>>>>>
> > >>>>>>> This especially breaks kpatch, which is using 'extra-y := kpatch.lds'
> > >>>>>>> and 'make M=...' to build livepatch patch module.
> > >>>>>>>
> > >>>>>>> Add extra-y to targets-for-modules so that such kind of build works
> > >>>>>>> properly.
> > >>>>>>>
> > >>>>>>> Signed-off-by: WANG Chao <chao.wang@ucloud.cn>
> > >>>>>>> ---
> > >>>>>>>   scripts/Makefile.build | 2 +-
> > >>>>>>>   1 file changed, 1 insertion(+), 1 deletion(-)
> > >>>>>>>
> > >>>>>>> diff --git a/scripts/Makefile.build b/scripts/Makefile.build
> > >>>>>>> index ae647379b579..0113a042d643 100644
> > >>>>>>> --- a/scripts/Makefile.build
> > >>>>>>> +++ b/scripts/Makefile.build
> > >>>>>>> @@ -86,7 +86,7 @@ ifdef need-builtin
> > >>>>>>>   targets-for-builtin += $(obj)/built-in.a
> > >>>>>>>   endif
> > >>>>>>>
> > >>>>>>> -targets-for-modules := $(patsubst %.o, %.mod, $(filter %.o, $(obj-m)))
> > >>>>>>> +targets-for-modules := $(extra-y) $(patsubst %.o, %.mod, $(filter %.o, $(obj-m)))
> > >>>>>>>
> > >>>>>>>   ifdef need-modorder
> > >>>>>>>   targets-for-modules += $(obj)/modules.order
> > >>>>>>> --
> > >>>>>>> 2.29.1
> > >>>>>>>
> > >>>>>>
> > >>>>>> NACK.
> > >>>>>>
> > >>>>>> Please fix your Makefile.
> > >>>>>>
> > >>>>>> Hint:
> > >>>>>> https://patchwork.kernel.org/project/linux-kbuild/patch/20201123045403.63402-6-masahiroy@kernel.org/
> > >>>>>>
> > >>>>>>
> > >>>>>> Probably what you should use is 'targets'.
> > >>>>>
> > >>>>> I tried with 'targets' and 'always-y'. Both doesn't work for me.
> > >>>>>
> > >>>>> I narraw it down to the following example:
> > >>>>>
> > >>>>> cat > Makefile << _EOF_
> > >>>>> obj-m += foo.o
> > >>>>>
> > >>>>> ldflags-y += -T $(src)/kpatch.lds
> > >>>>> always-y += kpatch.lds
> > >>>>>
> > >>>>> foo-objs += bar.o
> > >>>>>
> > >>>>> all:
> > >>>>>          make -C /lib/modules/$(shell uname -r)/build M=$(PWD)
> > >>>>> clean:
> > >>>>>          make -C /lib/modules/$(shell uname -r)/build M=$(PWD) clean
> > >>>>> _EOF_
> > >>>>>
> > >>>>> Take a look into scripts/Makefile.build:488:
> > >>>>>
> > >>>>> __build: $(if $(KBUILD_BUILTIN), $(targets-for-builtin)) \
> > >>>>>           $(if $(KBUILD_MODULES), $(targets-for-modules)) \
> > >>>>>           $(subdir-ym) $(always-y)
> > >>>>>          @:
> > >>>>>
> > >>>>> 'always-y' is built after 'targets-for-modules'. This makes
> > >>>>> 'targets-for-modules' fails because kpatch.lds isn't there.
> > >>>>
> > >>>>
> > >>>> Heh, you rely on the targets built from left to right,
> > >>>> and you have never thought Make supports the parallel option -j.
> > >>>
> > >>> You're right. I missed that.
> > >>>
> > >>>>
> > >>>>
> > >>>> You need to specify the dependency if you expect objects
> > >>>> are built in the particular order.
> > >>>>
> > >>>> However, in this case, using ldflags-y looks wrong
> > >>>> in the first place.
> > >>>>
> > >>>> The linker script is used when combining the object
> > >>>> as well as the final link of *.ko
> > >>
> > >> We want linker script to be used on both those steps, otherwise modpost
> > >> fails.
> > >
> > >
> > > In that case, does the following work?
> > > (untested)
> > >
> > >
> > >
> > > diff --git a/kmod/patch/Makefile b/kmod/patch/Makefile
> > > index e017b17..02d4c66 100644
> > > --- a/kmod/patch/Makefile
> > > +++ b/kmod/patch/Makefile
> > > @@ -12,7 +12,9 @@ endif
> > >
> > >   obj-m += $(KPATCH_NAME).o
> > >   ldflags-y += -T $(src)/kpatch.lds
> > > -extra-y := kpatch.lds
> > > +targets += kpatch.lds
> > > +
> > > +$(obj)/$(KPATCH_NAME).o: $(obj)/kpatch.lds
> > >
> > >   $(KPATCH_NAME)-objs += patch-hook.o output.o
> > >
> >
> > Hi Masahiro,
> >
> > Yeah this is more or less what Artem came up with:
> > https://github.com/dynup/kpatch/pull/1149
> >
> > though we hadn't added kpatch.lds to targets.  Is there documentation
> > somewhere on what effect "targets" has for out-of-tree builds?
> >
> > Thanks,
> >
> > -- Joe
> >
> 
> 
> Please try the rebuild without changing any source code.
> 
> If kpatch.lds is needlessly rebuilt, you need to add
> it to 'targets'.
> 
> 
> In linux-next, this is documented.
> 
> Documentation/kbuild/makefile.rst:
> 
>         Any target that utilizes if_changed must be listed in $(targets),
>         otherwise the command line check will fail, and the target will
>         always be built.

Ah yes, it did rebuild every time. Thank you for the pointer.
diff mbox series

Patch

diff --git a/scripts/Makefile.build b/scripts/Makefile.build
index ae647379b579..0113a042d643 100644
--- a/scripts/Makefile.build
+++ b/scripts/Makefile.build
@@ -86,7 +86,7 @@  ifdef need-builtin
 targets-for-builtin += $(obj)/built-in.a
 endif
 
-targets-for-modules := $(patsubst %.o, %.mod, $(filter %.o, $(obj-m)))
+targets-for-modules := $(extra-y) $(patsubst %.o, %.mod, $(filter %.o, $(obj-m)))
 
 ifdef need-modorder
 targets-for-modules += $(obj)/modules.order