linux-kernel - Re: [PATCH v10 00/18] Enable FSGSBASE instructions

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Date:   Sun, 10 May 2020 17:50:28 -0700
From:   Andi Kleen <ak@...ux.intel.com>
To:     Vegard Nossum <vegard.nossum@...cle.com>
Cc:     Sasha Levin <sashal@...nel.org>, linux-kernel@...r.kernel.org,
        tglx@...utronix.de, luto@...nel.org, tony.luck@...el.com,
        chang.seok.bae@...el.com
Subject: Re: [PATCH v10 00/18] Enable FSGSBASE instructions

> So this is a check that checks if you're running in user mode if
> you have a debug trap with single step, but somehow it triggered
> for a user segment.
> 
> Probably the regs got corrupted. 
> 
> Sasha, I suspect you're missing a mov %rsp,%rdi somewhere in the
> debug entry path that sets up the regs argument for the C code.

... Ah never mind. Thomas has a better explanation.

-Andi