From: Nicolin Chen <nicoleotsuka@gmail.com>
To: Marc Zyngier <marc.zyngier@arm.com>
Cc: mark.rutland@arm.com, catalin.marinas@arm.com,
will.deacon@arm.com, oleg@redhat.com, cdall@linaro.org,
tbaicar@codeaurora.org, julien.thierry@arm.com,
Dave.Martin@arm.com, robin.murphy@arm.com, james.morse@arm.com,
ard.biesheuvel@linaro.org, xiexiuqi@huawei.com, mingo@kernel.org,
linux-arm-kernel@lists.infradead.org,
linux-kernel@vger.kernel.org
Subject: Re: [PATCH RFC v1] arm64: Handle traps from accessing CNTVCT/CNTFRQ for CONFIG_COMPAT
Date: Tue, 16 Jan 2018 13:37:46 -0800 [thread overview]
Message-ID: <20180116213745.GA9545@Asurada-Nvidia> (raw)
In-Reply-To: <86r2qpec32.wl-marc.zyngier@arm.com>
On Tue, Jan 16, 2018 at 09:19:13PM +0000, Marc Zyngier wrote:
> > I understand that it should take care of the condition field as
> > a general instruction handler. Just for curiosity: If we confine
> > the topic to read access of CNTVCT/CNTFRQ, what'd be the penalty
> > by ignoring the condition field and executing it anyway?
>
> Do you mean, apart from severely corrupting userspace execution?
> That's a rhetorical question, right?
I don't quite understand the corrupting userspace execution part.
What I see for a conditional CNTVCT read is more likely:
if (condition) { // in this case, if (true)
r1 = lower32(cntvct);
r2 = higher32(cntvct);
}
Could you please elaborate a bit? Thank you.
next prev parent reply other threads:[~2018-01-16 21:37 UTC|newest]
Thread overview: 17+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-01-11 4:43 [PATCH RFC v1] arm64: Handle traps from accessing CNTVCT/CNTFRQ for CONFIG_COMPAT Nicolin Chen
2018-01-11 4:43 ` Nicolin Chen
2018-01-11 8:51 ` Marc Zyngier
2018-01-11 8:51 ` Marc Zyngier
2018-01-16 20:32 ` Nicolin Chen
2018-01-16 21:19 ` Marc Zyngier
2018-01-16 21:37 ` Nicolin Chen [this message]
2018-01-17 2:13 ` Nicolin Chen
2018-01-17 2:13 ` Nicolin Chen
2018-01-17 9:03 ` Marc Zyngier
2018-01-17 9:03 ` Marc Zyngier
2018-01-17 20:41 ` Nicolin Chen
2018-01-17 20:41 ` Nicolin Chen
2018-01-17 23:35 ` Robin Murphy
2018-01-17 23:35 ` Robin Murphy
2018-01-17 23:39 ` Nicolin Chen
2018-01-17 23:39 ` Nicolin Chen
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