Re: [PATCH v4 0/7] x86/boot: Remove runtime relocations from compressed kernel

From: Arvind Sankar <nivedita@alum.mit.edu>
To: Sedat Dilek <sedat.dilek@gmail.com>
Cc: Arvind Sankar <nivedita@alum.mit.edu>,
	Thomas Gleixner <tglx@linutronix.de>,
	Ingo Molnar <mingo@redhat.com>, Borislav Petkov <bp@alien8.de>,
	"H. Peter Anvin" <hpa@zytor.com>,
	x86@kernel.org, Nick Desaulniers <ndesaulniers@google.com>,
	Fangrui Song <maskray@google.com>,
	Dmitry Golovin <dima@golovin.in>,
	Clang-Built-Linux ML <clang-built-linux@googlegroups.com>,
	Ard Biesheuvel <ardb@kernel.org>,
	Masahiro Yamada <masahiroy@kernel.org>,
	Daniel Kiper <daniel.kiper@oracle.com>,
	Kees Cook <keescook@chromium.org>,
	Nathan Chancellor <natechancellor@gmail.com>,
	Arnd Bergmann <arnd@arndb.de>, "H . J . Lu" <hjl@sourceware.org>,
	linux-kernel@vger.kernel.org
Subject: Re: [PATCH v4 0/7] x86/boot: Remove runtime relocations from compressed kernel
Date: Tue, 14 Jul 2020 15:29:56 -0400	[thread overview]
Message-ID: <20200714192956.GA689174@rani.riverdale.lan> (raw)
In-Reply-To: <CA+icZUWHdsk9+wkTZOdDghM7pRZyk2vHgxpYx62vPooqohzbYw@mail.gmail.com>

On Tue, Jul 14, 2020 at 08:30:14PM +0200, Sedat Dilek wrote:
> > I did a full new build...
> >
> > ...and it fails with ld.lld-11 as linker:
> >
> > ld.lld-11 -m elf_x86_64 -pie  --no-dynamic-linker -r -o
> > arch/x86/boot/compressed/.tmp_misc.o arch/x86/boot/compressed/misc.o
> > -T arch/x86/boot/compressed/.tmp_misc.ver; mv -f
> > arch/x86/boot/compressed/.tmp_misc.o arch/x86/boot/compressed/misc.o;
> > rm -f arch/x86/boot/compressed/.tmp_misc.ver; fi
> > *** ld.lld-11: error: -r and -pie may not be used together ***
> > make[5]: *** [scripts/Makefile.build:281:
> > arch/x86/boot/compressed/misc.o] Error 1
> >
> > It's annoying to fail on the last minutes of a build.
> > Sorry for being very honest.
> >
> 
> I applied this diff...
> 
> $ git diff arch/x86/boot/compressed/Makefile
> diff --git a/arch/x86/boot/compressed/Makefile
> b/arch/x86/boot/compressed/Makefile
> index 789d5d14d8b0..9ba52a656838 100644
> --- a/arch/x86/boot/compressed/Makefile
> +++ b/arch/x86/boot/compressed/Makefile
> @@ -51,7 +51,10 @@ UBSAN_SANITIZE :=n
>  KBUILD_LDFLAGS := -m elf_$(UTS_MACHINE)
>  # Compressed kernel should be built as PIE since it may be loaded at any
>  # address by the bootloader.
> +# LLD linker does not allow -r and -pie options to be used together.
> +ifndef CONFIG_LD_IS_LLD
>  KBUILD_LDFLAGS += -pie $(call ld-option, --no-dynamic-linker)
> +endif
>  LDFLAGS_vmlinux := -T
> 
>  hostprogs      := mkpiggy
> 
> ...and was able to build, assemble, link arch/x86/boot/compressed/*.
> 
> - Sedat -

Thanks for the test.

Can you share your .config? The error messages look like they're coming
from running modversions on misc.o, which is unexpected as it shouldn't
have any exported symbols, and it doesn't in my builds.

In any case, I think the right fix here would be to add -pie and
--no-dynamic-linker to LDFLAGS_vmlinux instead of KBUILD_LDFLAGS.