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

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Message-ID: <CA+icZUUq9Wtut702su0HQ5qALkDvR+cdW7bczdj_mv=p-U3w4g@mail.gmail.com>
Date:   Tue, 14 Jul 2020 21:21:10 +0200
From:   Sedat Dilek <sedat.dilek@...il.com>
To:     Arvind Sankar <nivedita@...m.mit.edu>
Cc:     Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...hat.com>, Borislav Petkov <bp@...en8.de>,
        "H. Peter Anvin" <hpa@...or.com>, x86@...nel.org,
        Nick Desaulniers <ndesaulniers@...gle.com>,
        Fangrui Song <maskray@...gle.com>,
        Dmitry Golovin <dima@...ovin.in>,
        Clang-Built-Linux ML <clang-built-linux@...glegroups.com>,
        Ard Biesheuvel <ardb@...nel.org>,
        Masahiro Yamada <masahiroy@...nel.org>,
        Daniel Kiper <daniel.kiper@...cle.com>,
        Kees Cook <keescook@...omium.org>,
        Nathan Chancellor <natechancellor@...il.com>,
        Arnd Bergmann <arnd@...db.de>,
        "H . J . Lu" <hjl@...rceware.org>, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v4 0/7] x86/boot: Remove runtime relocations from
 compressed kernel

On Tue, Jul 14, 2020 at 8:33 PM Sedat Dilek <sedat.dilek@...il.com> wrote:
>
> On Tue, Jul 14, 2020 at 8:30 PM Sedat Dilek <sedat.dilek@...il.com> 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/*.
> >
>
> I checked my last succesfull build without your patchset:
>
> $ grep no-dynamic-linker build-log_5.8.0-rc5-1-amd64-llvm11-ias.txt
> [ EMPTY ]
>

I was able to boot on bare metal.

Feel free to add my...

Tested-by: Sedat Dilek <sedat.dilek@...il.com>

...when you restore "old" behaviour when CONFIG_LD_IS_LLD=y (apply or
fold-in my diff with comment)...

...and use one "runtime" in your subject-line:

$ git log --oneline
v5.8-rc5..for-5.8/x86-boot-compressed-remove-runtime-relocations-nivedita-v4
| egrep 'runtime|run-time'
9547f8f08689 x86/boot: Check that there are no runtime relocations
ede02a307b30 x86/boot: Remove runtime relocations from head_{32,64}.S
525a67ac7ea9 x86/boot: Remove run-time relocations from .head.text code

Thanks.

- Sedat -