linux-kernel - Re: [PATCH v2 3/6] x86/cpu: Remove CONFIG_X86

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Date:   Tue, 8 Feb 2022 16:06:52 +0100
From:   Borislav Petkov <bp@...en8.de>
To:     Kees Cook <keescook@...omium.org>,
        Peter Zijlstra <peterz@...radead.org>
Cc:     X86 ML <x86@...nel.org>, LKML <linux-kernel@...r.kernel.org>,
        Lai Jiangshan <jiangshanlai@...il.com>
Subject: Re: [PATCH v2 3/6] x86/cpu: Remove CONFIG_X86_SMAP and "nosmap"

On Mon, Feb 07, 2022 at 02:07:27PM -0800, Kees Cook wrote:
> On Thu, Jan 27, 2022 at 12:56:23PM +0100, Borislav Petkov wrote:
> > From: Borislav Petkov <bp@...e.de>
> > 
> > Those were added as part of the SMAP enablement but SMAP is currently
> > an integral part of kernel proper and there's no need to disable it
> > anymore.
> > 
> > Rip out that functionality.
> > 
> > If still needed - clearcpuid=smap.
> > 
> > Signed-off-by: Borislav Petkov <bp@...e.de>
> > Reviewed-by: Lai Jiangshan <jiangshanlai@...il.com>
> > ---
> >  .../admin-guide/kernel-parameters.txt         |  2 +-
> >  Documentation/x86/cpuinfo.rst                 |  5 ++--
> >  arch/x86/Kconfig                              | 11 ---------
> >  arch/x86/include/asm/disabled-features.h      |  8 +------
> >  arch/x86/include/asm/smap.h                   | 24 -------------------
> >  arch/x86/kernel/cpu/common.c                  | 15 +-----------
> >  scripts/Makefile.build                        |  1 -
> >  scripts/link-vmlinux.sh                       |  3 ---
> >  .../arch/x86/include/asm/disabled-features.h  |  8 +------
> >  9 files changed, 6 insertions(+), 71 deletions(-)
> > [...]
> > diff --git a/scripts/Makefile.build b/scripts/Makefile.build
> > index a4b89b757287..9b37902607ed 100644
> > --- a/scripts/Makefile.build
> > +++ b/scripts/Makefile.build
> > @@ -233,7 +233,6 @@ objtool_args =								\
> >  	$(if $(CONFIG_FRAME_POINTER),, --no-fp)				\
> >  	$(if $(CONFIG_GCOV_KERNEL)$(CONFIG_LTO_CLANG), --no-unreachable)\
> >  	$(if $(CONFIG_RETPOLINE), --retpoline)				\
> > -	$(if $(CONFIG_X86_SMAP), --uaccess)				\
> >  	$(if $(CONFIG_FTRACE_MCOUNT_USE_OBJTOOL), --mcount)		\
> >  	$(if $(CONFIG_SLS), --sls)
> >  
> > diff --git a/scripts/link-vmlinux.sh b/scripts/link-vmlinux.sh
> > index 666f7bbc13eb..8547aaa1a630 100755
> > --- a/scripts/link-vmlinux.sh
> > +++ b/scripts/link-vmlinux.sh
> > @@ -140,9 +140,6 @@ objtool_link()
> >  		if is_enabled CONFIG_RETPOLINE; then
> >  			objtoolopt="${objtoolopt} --retpoline"
> >  		fi
> > -		if is_enabled CONFIG_X86_SMAP; then
> > -			objtoolopt="${objtoolopt} --uaccess"
> > -		fi
> >  		if is_enabled CONFIG_SLS; then
> >  			objtoolopt="${objtoolopt} --sls"
> >  		fi
> 
> I was expecting to see --uaccess unconditionally added to objtool
> arguments. I think that needs to happen?

Hmm, I think you're right.

Mr. Z?

-- 
Regards/Gruss,
    Boris.

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