linux-kernel - Re: [PATCH 09/43] x86/entry: Move SYSENTER_stack to the beginning of struct tss

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Date:   Fri, 24 Nov 2017 12:44:36 +0100
From:   Borislav Petkov <bp@...en8.de>
To:     Ingo Molnar <mingo@...nel.org>
Cc:     linux-kernel@...r.kernel.org,
        Dave Hansen <dave.hansen@...ux.intel.com>,
        Andy Lutomirski <luto@...capital.net>,
        Thomas Gleixner <tglx@...utronix.de>,
        "H . Peter Anvin" <hpa@...or.com>,
        Peter Zijlstra <peterz@...radead.org>,
        Linus Torvalds <torvalds@...ux-foundation.org>
Subject: Re: [PATCH 09/43] x86/entry: Move SYSENTER_stack to the beginning of
 struct tss_struct

On Fri, Nov 24, 2017 at 10:14:14AM +0100, Ingo Molnar wrote:
> From: Andy Lutomirski <luto@...nel.org>
> 
> SYSENTER_stack should have reliable overflow detection, which
> means that it needs to be at the bottom of a page, not the top.
> Move it to the beginning of struct tss_struct and page-align it.
> 
> Also add an assertion to make sure that the fixed hardware TSS
> doesn't cross a page boundary.
> 
> Signed-off-by: Andy Lutomirski <luto@...nel.org>
> Reviewed-by: Thomas Gleixner <tglx@...utronix.de>
> Cc: Borislav Petkov <bp@...en8.de>
> Cc: Borislav Petkov <bpetkov@...e.de>
> Cc: Brian Gerst <brgerst@...il.com>
> Cc: Dave Hansen <dave.hansen@...el.com>
> Cc: Denys Vlasenko <dvlasenk@...hat.com>
> Cc: H. Peter Anvin <hpa@...or.com>
> Cc: Josh Poimboeuf <jpoimboe@...hat.com>
> Cc: Linus Torvalds <torvalds@...ux-foundation.org>
> Cc: Peter Zijlstra <peterz@...radead.org>
> Link: http://lkml.kernel.org/r/8de9901e7c3a6aa8fac95b37b9c7b96f1900f11a.1511497875.git.luto@kernel.org
> Signed-off-by: Ingo Molnar <mingo@...nel.org>
> ---
>  arch/x86/include/asm/processor.h | 21 ++++++++++++---------
>  arch/x86/kernel/cpu/common.c     | 21 +++++++++++++++++++++
>  2 files changed, 33 insertions(+), 9 deletions(-)

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

Thanks to tglx for clarifying the whole top and bottom meaning here for
me - I was confused.

-- 
Regards/Gruss,
    Boris.

Good mailing practices for 400: avoid top-posting and trim the reply.