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Message-Id: <20220214114927.6104-1-alexandr.lobakin@intel.com>
Date: Mon, 14 Feb 2022 12:49:27 +0100
From: Alexander Lobakin <alexandr.lobakin@...el.com>
To: Peter Zijlstra <peterz@...radead.org>
Cc: Alexander Lobakin <alexandr.lobakin@...el.com>,
linux-hardening@...r.kernel.org, x86@...nel.org,
Borislav Petkov <bp@...en8.de>,
Jesse Brandeburg <jesse.brandeburg@...el.com>,
Kristen Carlson Accardi <kristen@...ux.intel.com>,
Kees Cook <keescook@...omium.org>,
Miklos Szeredi <miklos@...redi.hu>,
Ard Biesheuvel <ardb@...nel.org>,
Tony Luck <tony.luck@...el.com>,
Bruce Schlobohm <bruce.schlobohm@...el.com>,
Jessica Yu <jeyu@...nel.org>,
kernel test robot <lkp@...el.com>,
Miroslav Benes <mbenes@...e.cz>,
Evgenii Shatokhin <eshatokhin@...tuozzo.com>,
Jonathan Corbet <corbet@....net>,
Masahiro Yamada <masahiroy@...nel.org>,
Michal Marek <michal.lkml@...kovi.net>,
Nick Desaulniers <ndesaulniers@...gle.com>,
Herbert Xu <herbert@...dor.apana.org.au>,
"David S. Miller" <davem@...emloft.net>,
Thomas Gleixner <tglx@...utronix.de>,
Will Deacon <will@...nel.org>, Ingo Molnar <mingo@...hat.com>,
Christoph Hellwig <hch@....de>,
Dave Hansen <dave.hansen@...ux.intel.com>,
"H. Peter Anvin" <hpa@...or.com>,
Andy Lutomirski <luto@...nel.org>,
Arnd Bergmann <arnd@...db.de>,
Josh Poimboeuf <jpoimboe@...hat.com>,
Nathan Chancellor <nathan@...nel.org>,
Masami Hiramatsu <mhiramat@...nel.org>,
Marios Pomonis <pomonis@...gle.com>,
Sami Tolvanen <samitolvanen@...gle.com>,
"H.J. Lu" <hjl.tools@...il.com>, Nicolas Pitre <nico@...xnic.net>,
linux-kernel@...r.kernel.org, linux-kbuild@...r.kernel.org,
linux-arch@...r.kernel.org, live-patching@...r.kernel.org,
llvm@...ts.linux.dev
Subject: Re: [PATCH v10 05/15] x86: support asm function sections
From: Peter Zijlstra <peterz@...radead.org>
Date: Fri, 11 Feb 2022 16:45:24 +0100
> On Wed, Feb 09, 2022 at 07:57:42PM +0100, Alexander Lobakin wrote:
> > Address places which need special care and enable
> > CONFIG_ARCH_SUPPORTS_ASM_FUNCTION_SECTIONS.
> >
> > Notably:
> > - propagate `--sectname-subst` to KBUILD_AFLAGS in
> > x86/boot/Makefile and x86/boot/compressed/Makefile as both
> > override them;
> > - symbols starting with a dot (like ".Lrelocated") should be
> > handled manually with SYM_*_START_SECT(.Lrelocated, relocated)
> > as "two dots" is a special (and CPP doesn't want to concatenate
> > two dots in general);
> > - some symbols explicitly need to reside in one section (like
> > kexec control code, hibernation page etc.);
> > - macros creating aliases for functions (like __memcpy() for
> > memcpy() etc.) should go after the main declaration (as
> > aliases should be declared in the same section and they
> > don't have SYM_PUSH_SECTION() inside);
> > - things like ".org", ".align" should be manually pushed to
> > the same section the next symbol goes to;
> > - expand indirect_thunk wildcards in vmlinux.lds.S to catch
> > symbols back into the "main" section;
> > - inline ASM functions like __raw_callee*() should be pushed
> > manually as well.
> >
> > With these changes and `-ffunction-sections` enabled, "plain"
> > ".text" section is empty which means that everything works
> > right as expected.
> >
> > Signed-off-by: Alexander Lobakin <alexandr.lobakin@...el.com>
> > ---
> > arch/x86/Kconfig | 1 +
> > arch/x86/boot/Makefile | 1 +
> > arch/x86/boot/compressed/Makefile | 1 +
> > arch/x86/boot/compressed/head_32.S | 2 +-
> > arch/x86/boot/compressed/head_64.S | 32 ++++++++++++-------
> > arch/x86/boot/pmjump.S | 2 +-
> > arch/x86/crypto/aesni-intel_asm.S | 4 +--
> > arch/x86/crypto/poly1305-x86_64-cryptogams.pl | 4 +++
> > arch/x86/include/asm/paravirt.h | 2 ++
> > arch/x86/include/asm/qspinlock_paravirt.h | 2 ++
> > arch/x86/kernel/head_32.S | 4 +--
> > arch/x86/kernel/head_64.S | 4 +--
> > arch/x86/kernel/kprobes/core.c | 2 ++
> > arch/x86/kernel/kvm.c | 2 ++
> > arch/x86/kernel/relocate_kernel_32.S | 10 +++---
> > arch/x86/kernel/relocate_kernel_64.S | 12 ++++---
> > arch/x86/kernel/vmlinux.lds.S | 2 +-
> > arch/x86/kvm/emulate.c | 7 +++-
> > arch/x86/lib/copy_user_64.S | 2 +-
> > arch/x86/lib/error-inject.c | 2 ++
> > arch/x86/lib/getuser.S | 5 ++-
> > arch/x86/lib/memcpy_64.S | 4 +--
> > arch/x86/lib/memmove_64.S | 5 ++-
> > arch/x86/lib/memset_64.S | 5 +--
> > arch/x86/lib/putuser.S | 2 +-
> > arch/x86/power/hibernate_asm_32.S | 10 +++---
> > arch/x86/power/hibernate_asm_64.S | 10 +++---
> > 27 files changed, 89 insertions(+), 50 deletions(-)
>
> Urgh, how much of that can you avoid by (ab)using __DISABLE_EXPORTS
> like:
>
> https://git.kernel.org/pub/scm/linux/kernel/git/peterz/queue.git/commit/?h=x86/wip.ibt&id=ab74f54f2b1f6cfeaf2b3ba6999bde7cabada9ca
Oh, never thought on that, looks like at least 3 of 27 files and
35 of 139 lines, nice!
I'll redo this one in the meantime whilst waiting for more comments
here.
Thanks!
Al
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