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    SubjectRe: [PATCH 0/5] RFC: x86: Early exception table support
    Haha,

    I was looking into that too and you beat me to it. Now isn't that great!
    :-)

    On Wed, Apr 18, 2012 at 05:16:45PM -0700, H. Peter Anvin wrote:
    > If we get an exception during early boot, walk the exception table to
    > see if we should intercept it. The main use case for this is to allow
    > rdmsr_safe()/wrmsr_safe() during CPU initialization.
    >
    > Since the exception table is currently sorted at runtime, and fairly
    > late in startup, this code walks the exception table linearly. We
    > obviously don't need to worry about modules, however: none have been
    > loaded at this point.
    >
    > In the future it would be better to have the table sorted at compile
    > time, or even better, turned into a perfect hash. At that point this
    > code should be changed out from doing a linear search.

    FWIW, I was thinking that maybe we could sort the main extable
    (i.e., no modules) before we assign the early idt handlers in
    x86_64_start_kernel() and this way use the binary search through it in
    search_extable().

    I'm sending the patches I had as a reply to this mail so that you can
    get a better idea of what I mean. They're rough and the asm is f*cked
    up so don't look at that - I was still figuring out the exception frame
    layout to do it properly.

    > This patchset also makes the early exception handling a little more
    > similar between x86-64 and i386, but a lot of unification could (and
    > should) still be done: in particular, setup done in C as in x86-64,
    > and verbose error dump as in i386.

    Yeah, I'll look through those and give them a test drive on my boxes
    here.

    --
    Regards/Gruss,
    Boris.

    Advanced Micro Devices GmbH
    Einsteinring 24, 85609 Dornach
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