linux-kernel - Re: [RFC][PATCH v2 11/21] x86/pti: Extend PTI user mappings

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Message-ID: <CALCETrXoykRjRPYPfZr6gBKoMnHuRYiJTDOcFYMq8GLef00j1A@mail.gmail.com>
Date:   Mon, 16 Nov 2020 11:48:06 -0800
From:   Andy Lutomirski <luto@...nel.org>
To:     Alexandre Chartre <alexandre.chartre@...cle.com>
Cc:     Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...hat.com>, Borislav Petkov <bp@...en8.de>,
        "H. Peter Anvin" <hpa@...or.com>, X86 ML <x86@...nel.org>,
        Dave Hansen <dave.hansen@...ux.intel.com>,
        Andrew Lutomirski <luto@...nel.org>,
        Peter Zijlstra <peterz@...radead.org>,
        LKML <linux-kernel@...r.kernel.org>,
        Tom Lendacky <thomas.lendacky@....com>,
        Joerg Roedel <jroedel@...e.de>,
        Konrad Rzeszutek Wilk <konrad.wilk@...cle.com>,
        jan.setjeeilers@...cle.com, Junaid Shahid <junaids@...gle.com>,
        oweisse@...gle.com, Mike Rapoport <rppt@...ux.vnet.ibm.com>,
        Alexander Graf <graf@...zon.de>, mgross@...ux.intel.com,
        kuzuno@...il.com
Subject: Re: [RFC][PATCH v2 11/21] x86/pti: Extend PTI user mappings

On Mon, Nov 16, 2020 at 6:49 AM Alexandre Chartre
<alexandre.chartre@...cle.com> wrote:
>
> Extend PTI user mappings so that more kernel entry code can be executed
> with the user page-table. To do so, we need to map syscall and interrupt
> entry code, per cpu offsets (__per_cpu_offset, which is used some in
> entry code), the stack canary, and the PTI stack (which is defined per
> task).

Does anything unmap the PTI stack?  Mapping is easy, and unmapping
could be a pretty big mess.

--Andy