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

From: Masahiro Yamada <masahiroy@kernel.org>
To: Kees Cook <keescook@chromium.org>
Cc: Nathan Chancellor <natechancellor@gmail.com>,
	Michal Marek <michal.lkml@markovi.net>,
	Russell King <linux@armlinux.org.uk>,
	Catalin Marinas <catalin.marinas@arm.com>,
	Will Deacon <will@kernel.org>,
	Michael Ellerman <mpe@ellerman.id.au>,
	Thomas Gleixner <tglx@linutronix.de>,
	Ingo Molnar <mingo@redhat.com>, Borislav Petkov <bp@alien8.de>,
	X86 ML <x86@kernel.org>,
	Nick Desaulniers <ndesaulniers@google.com>,
	Arvind Sankar <nivedita@alum.mit.edu>,
	Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
	Linux Kbuild mailing list <linux-kbuild@vger.kernel.org>,
	linux-arm-kernel <linux-arm-kernel@lists.infradead.org>,
	linuxppc-dev <linuxppc-dev@lists.ozlabs.org>,
	clang-built-linux <clang-built-linux@googlegroups.com>
Subject: Re: [PATCH v2 1/2] kbuild: Hoist '--orphan-handling' into Kconfig
Date: Tue, 1 Dec 2020 22:28:30 +0900	[thread overview]
Message-ID: <CAK7LNASmiWkw3+F1_AJWYDAXntcpcNQmdX0d_hVQq7oxQ_m74A@mail.gmail.com> (raw)
In-Reply-To: <202011201607.75FA476@keescook>

On Sat, Nov 21, 2020 at 9:08 AM Kees Cook <keescook@chromium.org> wrote:
>
> 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@chromium.org>
> > Acked-by: Michael Ellerman <mpe@ellerman.id.au> (powerpc)
> > Reviewed-by: Nick Desaulniers <ndesaulniers@google.com>
> > Tested-by: Nick Desaulniers <ndesaulniers@google.com>
> > Signed-off-by: Nathan Chancellor <natechancellor@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.
>

Sorry for the delay.

Applied to linux-kbuild.

> -Kees
>
> --
> Kees Cook
>
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-- 
Best Regards
Masahiro Yamada