Re: [PATCH v2 1/3] sh: thin archives fix linking

[Nicholas Piggin <npiggin@gmail.com>]

On Fri, 23 Jun 2017 12:25:10 +0900
Masahiro Yamada <yamada.masahiro@socionext.com> wrote:

> 2017-06-22 21:39 GMT+09:00 Nicholas Piggin <npiggin@gmail.com>:
> > The VDSO symbols can't be linked into built-in.o when building with
> > thin archives, so change this to linking a new object file that is
> > included into the built-in.o.
> >
> > Cc: Yoshinori Sato <ysato@users.sourceforge.jp>
> > Cc: Rich Felker <dalias@libc.org>
> > Cc: linux-sh@vger.kernel.org
> > Signed-off-by: Nicholas Piggin <npiggin@gmail.com>
> > ---
> >  arch/sh/kernel/vsyscall/Makefile | 16 +++++++++-------
> >  1 file changed, 9 insertions(+), 7 deletions(-)
> >
> > diff --git a/arch/sh/kernel/vsyscall/Makefile b/arch/sh/kernel/vsyscall/Makefile
> > index 8f0ea5fc835c..efc7a6837ef6 100644
> > --- a/arch/sh/kernel/vsyscall/Makefile
> > +++ b/arch/sh/kernel/vsyscall/Makefile
> > @@ -1,4 +1,4 @@
> > -obj-y += vsyscall.o vsyscall-syscall.o
> > +obj-y += vsyscall.o vsyscall-syscall.o vsyscall-syms.o
> >
> >  $(obj)/vsyscall-syscall.o: \
> >         $(foreach F,trapa,$(obj)/vsyscall-$F.so)
> > @@ -26,11 +26,13 @@ $(obj)/vsyscall-%.so: $(src)/vsyscall.lds $(obj)/vsyscall-%.o FORCE
> >  # We also create a special relocatable object that should mirror the symbol
> >  # table and layout of the linked DSO.  With ld -R we can then refer to
> >  # these symbols in the kernel code rather than hand-coded addresses.
> > -extra-y += vsyscall-syms.o
> > -$(obj)/built-in.o: $(obj)/vsyscall-syms.o
> > -$(obj)/built-in.o: ld_flags += -R $(obj)/vsyscall-syms.o
> > -
> > -SYSCFLAGS_vsyscall-syms.o = -r
> > -$(obj)/vsyscall-syms.o: $(src)/vsyscall.lds \
> > +SYSCFLAGS_vsyscall-dummy.o = -r
> > +$(obj)/vsyscall-dummy.o: $(src)/vsyscall.lds \
> >                         $(obj)/vsyscall-trapa.o $(obj)/vsyscall-note.o FORCE
> >         $(call if_changed,syscall)
> > +
> > +quiet_cmd_syscall_syms = SYSCALL $@
> > +      cmd_syscall_syms = $(LD) -r -R $(obj)/vsyscall-dummy.o -o $@
> > +
> > +$(obj)/vsyscall-syms.o: $(obj)/vsyscall-dummy.o
> > +       $(call if_changed,syscall_syms)
> > --
> > 2.11.0  
> 
> I applied this, but
> I just noticed vsyscall-dummy is rebuilt every time.
> 
> 
>   SYSCALL arch/sh/kernel/vsyscall/vsyscall-dummy.o
>   SYSCALL arch/sh/kernel/vsyscall/vsyscall-syms.o
>   AR      arch/sh/kernel/vsyscall/built-in.o
>   AR      arch/sh/kernel/built-in.o
> 
> 
> 
> We can avoid the unneeded rebuild by adding "vsyscall-dummy.o" to "targets".
> 
> targets += vsyscall-note.o vsyscall.lds vsyscall-dummy.o

Thanks, good catch. The tile patch may have the same issue?