linux-kernel - Re: [PATCH 5/7] x86: Insert endbr32/endbr64 to vDSO

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Message-ID: <CALCETrVRH8LeYoo7V1VBPqg4WS0Enxtizt=T7dPvgoeWfJrdzA@mail.gmail.com>
Date:   Thu, 7 Jun 2018 13:50:26 -0700
From:   Andy Lutomirski <luto@...nel.org>
To:     Yu-cheng Yu <yu-cheng.yu@...el.com>
Cc:     LKML <linux-kernel@...r.kernel.org>, linux-doc@...r.kernel.org,
        Linux-MM <linux-mm@...ck.org>,
        linux-arch <linux-arch@...r.kernel.org>, X86 ML <x86@...nel.org>,
        "H. Peter Anvin" <hpa@...or.com>,
        Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...hat.com>,
        "H. J. Lu" <hjl.tools@...il.com>,
        "Shanbhogue, Vedvyas" <vedvyas.shanbhogue@...el.com>,
        "Ravi V. Shankar" <ravi.v.shankar@...el.com>,
        Dave Hansen <dave.hansen@...ux.intel.com>,
        Jonathan Corbet <corbet@....net>,
        Oleg Nesterov <oleg@...hat.com>, Arnd Bergmann <arnd@...db.de>,
        mike.kravetz@...cle.com
Subject: Re: [PATCH 5/7] x86: Insert endbr32/endbr64 to vDSO

On Thu, Jun 7, 2018 at 7:42 AM Yu-cheng Yu <yu-cheng.yu@...el.com> wrote:
>
> From: "H.J. Lu" <hjl.tools@...il.com>
>
> When Intel indirect branch tracking is enabled, functions in vDSO which
> may be called indirectly should have endbr32 or endbr64 as the first
> instruction.  We try to compile vDSO with -fcf-protection=branch -mibt
> if possible.  Otherwise, we insert endbr32 or endbr64 by hand to assembly
> codes generated by the compiler.

Wow, that's... a genuine abomination.  Do we really need to support
CET on kernels built with old toolchains?

--Andy