[PATCH v2 1/2] kbuild: Hoist '--orphan-handling' into Kconfig

[Kees Cook]

On Thu, Nov 19, 2020 at 01:46:56PM -0700, Nathan Chancellor wrote:
> Currently, '--orphan-handling=warn' is spread out across four different
> architectures in their respective Makefiles, which makes it a little
> unruly to deal with in case it needs to be disabled for a specific
> linker version (in this case, ld.lld 10.0.1).
> 
> To make it easier to control this, hoist this warning into Kconfig and
> the main Makefile so that disabling it is simpler, as the warning will
> only be enabled in a couple places (main Makefile and a couple of
> compressed boot folders that blow away LDFLAGS_vmlinx) and making it
> conditional is easier due to Kconfig syntax. One small additional
> benefit of this is saving a call to ld-option on incremental builds
> because we will have already evaluated it for CONFIG_LD_ORPHAN_WARN.
> 
> To keep the list of supported architectures the same, introduce
> CONFIG_ARCH_WANT_LD_ORPHAN_WARN, which an architecture can select to
> gain this automatically after all of the sections are specified and size
> asserted. A special thanks to Kees Cook for the help text on this
> config.
> 
> Link: https://github.com/ClangBuiltLinux/linux/issues/1187
> Acked-by: Kees Cook <keescook at chromium.org>
> Acked-by: Michael Ellerman <mpe at ellerman.id.au> (powerpc)
> Reviewed-by: Nick Desaulniers <ndesaulniers at google.com>
> Tested-by: Nick Desaulniers <ndesaulniers at google.com>
> Signed-off-by: Nathan Chancellor <natechancellor at gmail.com>

Masahiro, do you want to take these to get them to Linus for v5.10? I
can send them if you'd prefer.

-Kees

-- 
Kees Cook