Hi Vincenzo, We also are having issues building the cross vDSO with Clang: https://github.com/ClangBuiltLinux/linux/issues/595
It seems that `LINUXINCLUDE` in arch/arm64/kernel/vdso32/Makefile is including arm64 headers in the arm part of the vdso32 build, which causes Clang to error on the arm64 inline asm constraints being used in arm64. I think if the issue Will described is fixed, it will be simpler for us to fix the rest to get it to build w/ Clang. https://github.com/ClangBuiltLinux/linux/issues/595#issuecomment-509874891 is the basis of such a patch. Clang ships with all backends on by default, and uses a `-target <triple>` to cross compile; so the idea of passing two cross compiler binaries for a compat vDSO build doesn't really apply to Clang.
