linux-kernel - Re: [REGRESSION] x86/cpu fsgsbase breaks TLS in 32 bit rr tracees on a 64 bit system

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Message-ID: <6758DBF1-D707-45B3-BA10-3621674DEBF8@intel.com>
Date:   Fri, 21 Aug 2020 21:46:46 +0000
From:   "Bae, Chang Seok" <chang.seok.bae@...el.com>
To:     Kyle Huey <me@...ehuey.com>
CC:     Robert O'Callahan <rocallahan@...il.com>,
        Andy Lutomirski <luto@...nel.org>,
        Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...nel.org>,
        "H . Peter Anvin" <hpa@...or.com>, Andi Kleen <ak@...ux.intel.com>,
        "Shankar, Ravi V" <ravi.v.shankar@...el.com>,
        LKML <linux-kernel@...r.kernel.org>,
        "Hansen, Dave" <dave.hansen@...el.com>
Subject: Re: [REGRESSION] x86/cpu fsgsbase breaks TLS in 32 bit rr tracees on
 a 64 bit system


> On Aug 21, 2020, at 14:32, Kyle Huey <me@...ehuey.com> wrote:
> 
> 40c45904f818c1f6555294ca27afc5fda4f09e68 added magic for a 32 bit
> tracer tracing a 32 bit tracee on a 64 bit kernel, but it looks like a
> 64 bit tracer tracing a 32 bit tracee on a 64 bit kernel *is* now
> expected to preserve the fs/gsbase values (or die, in our case).
> 
> Is that correct?

Correct.

Thanks,
Chang