[PATCH 4/5] kbuild: unify vdso_install rules

[Sven Schnelle]

Masahiro Yamada <masahiroy at kernel.org> writes:

> Currently, there is no standard implementation for vdso_install,
> leading to various issues:
>
>  1. Code duplication
>
>     Many architectures duplicate similar code just for copying files
>     to the install destination.
>
>     Some architectures (arm, sparc, x86) create build-id symlinks,
>     introducing more code duplication.
>
>  2. Accidental updates of in-tree build artifacts
>
>     The vdso_install rule depends on the vdso files to install.
>     It may update in-tree build artifacts. This can be problematic,
>     as explained in commit 19514fc665ff ("arm, kbuild: make
>     "make install" not depend on vmlinux").
>
>  3. Broken code in some architectures
>
>     Makefile code is often copied from one architecture to another
>     without proper adaptation or testing.
>
>     The previous commits removed broken code from csky, UML, and parisc.
>
>     Another issue is that 'make vdso_install' for ARCH=s390 installs
>     vdso64, but not vdso32.
>
> To address these problems, this commit introduces the generic vdso_install.
>
> Architectures that support vdso_install need to define vdso-install-y
> in arch/*/Makefile.
>
> vdso-install-y lists the files to install. For example, arch/x86/Makefile
> looks like this:
>
>   vdso-install-$(CONFIG_X86_64)           += arch/x86/entry/vdso/vdso64.so.dbg
>   vdso-install-$(CONFIG_X86_X32_ABI)      += arch/x86/entry/vdso/vdsox32.so.dbg
>   vdso-install-$(CONFIG_X86_32)           += arch/x86/entry/vdso/vdso32.so.dbg
>   vdso-install-$(CONFIG_IA32_EMULATION)   += arch/x86/entry/vdso/vdso32.so.dbg
>
> These files will be installed to $(MODLIB)/vdso/ with the .dbg suffix,
> if exists, stripped away.
>
> vdso-install-y can optionally take the second field after the colon
> separator. This is needed because some architectures install vdso
> files as a different base name.
>
> The following is a snippet from arch/arm64/Makefile.
>
>   vdso-install-$(CONFIG_COMPAT_VDSO)      += arch/arm64/kernel/vdso32/vdso.so.dbg:vdso32.so
>
> This will rename vdso.so.dbg to vdso32.so during installation. If such
> architectures change their implementation so that the file names match,
> this workaround will go away.
>
> Signed-off-by: Masahiro Yamada <masahiroy at kernel.org>
> ---

Acked-by: Sven Schnelle <svens at linux.ibm.com> # s390