[PATCH] arm64: vdso: fix and clean-up Makefile

[PATCH] arm64: vdso: fix and clean-up Makefile

[Masahiro Yamada]

- $(call if_changed,...) must have FORCE as a prerequisite

- vdso.lds is a generated file, so it should be prefixed with
  $(obj)/ instead of $(src)/.

- cmd_vdsosym is a one-liner rule, so the assignment with '='
  is simpler.

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

 arch/arm64/kernel/vdso/Makefile | 8 +++-----
 1 file changed, 3 insertions(+), 5 deletions(-)

diff --git a/arch/arm64/kernel/vdso/Makefile b/arch/arm64/kernel/vdso/Makefile
index b801ee5..c9ad9aa 100644
--- a/arch/arm64/kernel/vdso/Makefile
+++ b/arch/arm64/kernel/vdso/Makefile
@@ -31,7 +31,7 @@ CPPFLAGS_vdso.lds += -P -C -U$(ARCH)
 $(obj)/vdso.o : $(obj)/vdso.so
 
 # Link rule for the .so file, .lds has to be first
-$(obj)/vdso.so.dbg: $(src)/vdso.lds $(obj-vdso)
+$(obj)/vdso.so.dbg: $(obj)/vdso.lds $(obj-vdso) FORCE
 	$(call if_changed,vdsold)
 
 # Strip rule for the .so file
@@ -42,9 +42,7 @@ $(obj)/%.so: $(obj)/%.so.dbg FORCE
 # Generate VDSO offsets using helper script
 gen-vdsosym := $(srctree)/$(src)/gen_vdso_offsets.sh
 quiet_cmd_vdsosym = VDSOSYM $@
-define cmd_vdsosym
-	$(NM) $< | $(gen-vdsosym) | LC_ALL=C sort > $@
-endef
+      cmd_vdsosym = $(NM) $< | $(gen-vdsosym) | LC_ALL=C sort > $@
 
 include/generated/vdso-offsets.h: $(obj)/vdso.so.dbg FORCE
 	$(call if_changed,vdsosym)
@@ -55,7 +53,7 @@ $(obj-vdso): %.o: %.S FORCE
 
 # Actual build commands
 quiet_cmd_vdsold = VDSOL   $@
-      cmd_vdsold = $(CC) $(c_flags) -Wl,-n -Wl,-T $^ -o $@
+      cmd_vdsold = $(CC) $(c_flags) -Wl,-n -Wl,-T $(real-prereqs) -o $@
 quiet_cmd_vdsoas = VDSOA   $@
       cmd_vdsoas = $(CC) $(a_flags) -c -o $@ $<
 
-- 
2.7.4

Re: [PATCH] arm64: vdso: fix and clean-up Makefile

[Will Deacon]

Hi Masahiro,

On Wed, Apr 03, 2019 at 05:48:22PM +0900, Masahiro Yamada wrote:
> - $(call if_changed,...) must have FORCE as a prerequisite
> 
> - vdso.lds is a generated file, so it should be prefixed with
>   $(obj)/ instead of $(src)/.

Hmm, this sounds quite alarming! How come out of tree builds seem to work
ok without this patch?

Will

Re: [PATCH] arm64: vdso: fix and clean-up Makefile

[Masahiro Yamada]

Hi Will,

On Wed, Apr 3, 2019 at 9:45 PM Will Deacon <will.deacon@arm.com> wrote:
>
> Hi Masahiro,
>
> On Wed, Apr 03, 2019 at 05:48:22PM +0900, Masahiro Yamada wrote:
> > - $(call if_changed,...) must have FORCE as a prerequisite
> >
> > - vdso.lds is a generated file, so it should be prefixed with
> >   $(obj)/ instead of $(src)/.
>
> Hmm, this sounds quite alarming! How come out of tree builds seem to work
> ok without this patch?

No, I do not mean like that.
This is just cosmetic (at least for now).
Kbuild conventionally use both $(obj) and $(src), but
they are the same in most places.
If you see the top of scripts/Makefile.build,
$(src) is the same as $(obj).


I fixed this x86 in commit 1742ed2088.
VDSO Makefiles are copied from arch to arch.

-- 
Best Regards
Masahiro Yamada

Re: [PATCH] arm64: vdso: fix and clean-up Makefile

[Will Deacon]

On Thu, Apr 04, 2019 at 02:04:23AM +0900, Masahiro Yamada wrote:
> On Wed, Apr 3, 2019 at 9:45 PM Will Deacon <will.deacon@arm.com> wrote:
> > On Wed, Apr 03, 2019 at 05:48:22PM +0900, Masahiro Yamada wrote:
> > > - $(call if_changed,...) must have FORCE as a prerequisite
> > >
> > > - vdso.lds is a generated file, so it should be prefixed with
> > >   $(obj)/ instead of $(src)/.
> >
> > Hmm, this sounds quite alarming! How come out of tree builds seem to work
> > ok without this patch?
> 
> No, I do not mean like that.
> This is just cosmetic (at least for now).
> Kbuild conventionally use both $(obj) and $(src), but
> they are the same in most places.
> If you see the top of scripts/Makefile.build,
> $(src) is the same as $(obj).

Ah thanks, that makes much more sense. I'll queue this up for 5.2.

Will