linux-kernel - Re: [PATCH] x86/mm/sme: Disable stack protection for mem_encrypt

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Message-ID: <20180227092810.GA26097@pd.tnic>
Date:   Tue, 27 Feb 2018 10:28:10 +0100
From:   Borislav Petkov <bp@...en8.de>
To:     Tom Lendacky <thomas.lendacky@....com>
Cc:     x86@...nel.org, linux-kernel@...r.kernel.org,
        "H. Peter Anvin" <hpa@...or.com>,
        Thomas Gleixner <tglx@...utronix.de>,
        Linus Torvalds <torvalds@...ux-foundation.org>,
        Ingo Molnar <mingo@...nel.org>,
        "Kirill A. Shutemov" <kirill.shutemov@...ux.intel.com>
Subject: Re: [PATCH] x86/mm/sme: Disable stack protection for
 mem_encrypt_identity.c

On Mon, Feb 26, 2018 at 05:25:54PM -0600, Tom Lendacky wrote:
> Stack protection is not compatible with early boot code.  All of the early
> SME boot code is now isolated in a separate file, mem_encrypt_identity.c,
> so arch/x86/mm/Makefile can be updated to turn off stack protection for
> the entire file.  This eliminates the need to worry about other functions
> within the file being instrumented with stack protection (as was seen
> when a newer version of GCC instrumented sme_encrypt_kernel() where an
> older version hadn't).  It also allows removal of the __nostackprotector
> attribute from individual functions.
> 
> Signed-off-by: Tom Lendacky <thomas.lendacky@....com>
> ---
>  arch/x86/mm/Makefile               |    1 +
>  arch/x86/mm/mem_encrypt_identity.c |    4 ++--
>  2 files changed, 3 insertions(+), 2 deletions(-)

Reviewed-by: Borislav Petkov <bp@...e.de>

-- 
Regards/Gruss,
    Boris.

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