Re: [PATCH 2/2] powerpc/vdso32: link vdso64 with linker

Christophe Leroy
2020-09-02T10:17:12Z

On 9/1/20 10:25 PM, Nick Desaulniers wrote:
> Rather than invoke the compiler as the driver, use the linker. That way
> we can check --orphan-handling=warn support correctly, as cc-ldoption
> was removed in
> commit 055efab3120b ("kbuild: drop support for cc-ldoption").
>
> Requires dropping the .got section. I couldn't find how it was used in
> the vdso32.
>
> Fixes: commit f2af201002a8 ("powerpc/build: vdso linker warning for orphan sections")
> Link: https://lore.kernel.org/lkml/CAKwvOdnn3wxYdJomvnveyD_njwRku3fABWT_bS92duihhywLJQ@mail.gmail.com/
> Signed-off-by: Nick Desaulniers <ndesaulniers@google.com>
> ---
> Not sure removing .got is a good idea or not. Otherwise I observe the
> following link error:
> powerpc-linux-gnu-ld: warning: orphan section `.got' from `arch/powerpc/kernel/vdso32/sigtramp.o' being placed in section `.got'
> powerpc-linux-gnu-ld: _GLOBAL_OFFSET_TABLE_ not defined in linker created .got
> powerpc-linux-gnu-ld: final link failed: bad value

Finally I spotted it I think:

make arch/powerpc/kernel/vdso32/ V=1

powerpc64-linux-ld -EB -m elf64ppc -shared -soname linux-vdso32.so.1
--eh-frame-hdr --orphan-handling=warn -T
arch/powerpc/kernel/vdso32/vdso32.lds
arch/powerpc/kernel/vdso32/sigtramp.o
arch/powerpc/kernel/vdso32/gettimeofday.o
arch/powerpc/kernel/vdso32/datapage.o
arch/powerpc/kernel/vdso32/cacheflush.o
arch/powerpc/kernel/vdso32/note.o arch/powerpc/kernel/vdso32/getcpu.o -o
arch/powerpc/kernel/vdso32/vdso32.so.dbg

If I do the same manually but with -m elf32ppc instead of -m elf64ppc,
there is no failure.

Adding -m elf32ppc to ldflags-y also works, allthough I don't like too
much having "-m elf64ppc -m elf32ppc" on the line.

Christophe