linux-kernel - RE: [PATCH] x86/entry/32: Fix setup of CS high bits

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Date:   Mon, 15 Oct 2018 13:14:06 +0000
From:   David Laight <David.Laight@...LAB.COM>
To:     'Jan Kiszka' <jan.kiszka@...mens.com>,
        Andy Lutomirski <luto@...nel.org>
CC:     Joerg Roedel <joro@...tes.org>,
        Thomas Gleixner <tglx@...utronix.de>,
        "Ingo Molnar" <mingo@...nel.org>, "H. Peter Anvin" <hpa@...or.com>,
        X86 ML <x86@...nel.org>, LKML <linux-kernel@...r.kernel.org>,
        Linux-MM <linux-mm@...ck.org>,
        Linus Torvalds <torvalds@...ux-foundation.org>,
        "Dave Hansen" <dave.hansen@...el.com>,
        Josh Poimboeuf <jpoimboe@...hat.com>,
        "Juergen Gross" <jgross@...e.com>,
        Peter Zijlstra <peterz@...radead.org>,
        "Borislav Petkov" <bp@...en8.de>, Jiri Kosina <jkosina@...e.cz>,
        Boris Ostrovsky <boris.ostrovsky@...cle.com>,
        Brian Gerst <brgerst@...il.com>,
        Denys Vlasenko <dvlasenk@...hat.com>,
        Eduardo Valentin <eduval@...zon.com>,
        Greg KH <gregkh@...uxfoundation.org>,
        Will Deacon <will.deacon@....com>,
        "Liguori, Anthony" <aliguori@...zon.com>,
        Daniel Gruss <daniel.gruss@...k.tugraz.at>,
        Hugh Dickins <hughd@...gle.com>,
        Kees Cook <keescook@...gle.com>,
        "Andrea Arcangeli" <aarcange@...hat.com>
Subject: RE: [PATCH] x86/entry/32: Fix setup of CS high bits

From: Jan Kiszka
> Sent: 15 October 2018 14:09
...
> > Those fields are genuinely 16 bit.  So the comment should say
> > something like "Those high bits are used for CS_FROM_ENTRY_STACK and
> > CS_FROM_USER_CR3".
> 
> /*
>   * The high bits of the CS dword (__csh) are used for
>   * CS_FROM_ENTRY_STACK and CS_FROM_USER_CR3. Clear them in case
>   * hardware didn't do this for us.
>   */

What's a 'dword' ? :-)

On a 32bit processor a 'word' will be 32 bits to a 'double-word'
would be 64 bits.
One of the worst names to use.

	David

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