Messages in this thread | | | Date | Thu, 20 Sep 2018 23:33:20 +0100 | From | Marc Zyngier <> | Subject | Re: [PATCH] arm64: Trap WFI executed in userspace |
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On Thu, 20 Sep 2018 23:04:30 +0100, Pavel Machek <pavel@ucw.cz> wrote: > > On Tue 2018-08-07 10:33:26, Marc Zyngier wrote: > > It recently came to light that userspace can execute WFI, and that > > the arm64 kernel doesn trap this event. This sounds rather benign, > > but the kernel should decide when it wants to wait for an interrupt, > > and not userspace. > > > > Let's trap WFI and treat it as a way to yield the CPU to another > > process. > > I don't think that's reasonable. Userspace should not be doing that, > and we do not want to encourage it. SIGILL would be reasonable, I'd > say.
This ship has already sailed. Sending SIGILL changes the ABI in an incompatible way. Immediately returning to userspace without doing anything else (see v2 [1]) is the best we can do without changing the behaviour of userspace.
Thanks,
M.
[1] https://patchwork.kernel.org/patch/10562517/
-- Jazz is not dead, it just smell funny.
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