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    SubjectRe: [PATCH 17/30] x86, kaiser: map debug IDT tables
    On Mon, 20 Nov 2017, Andy Lutomirski wrote:

    > On Fri, Nov 10, 2017 at 11:31 AM, Dave Hansen
    > <dave.hansen@linux.intel.com> wrote:
    > >
    > > From: Dave Hansen <dave.hansen@linux.intel.com>
    > >
    > > The IDT is another structure which the CPU references via a
    > > virtual address. It also obviously needs these to handle an
    > > interrupt in userspace, so these need to be mapped into the user
    > > copy of the page tables.
    >
    > Why would the debug IDT ever be used in user mode? IIRC it's a total
    > turd related to avoiding crap nesting inside NMI. Or am I wrong?

    No. It's called from the TRACE_IRQS macros in the ASM entry code and from
    do_nmi().

    > If it *is* used in user mode, then we have a bug and it should be in
    > the IDT to avoid address leaks just like the normal IDT.

    It's not so this can go away. Good catch.

    Thanks,

    tglx

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