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    SubjectRe: [PATCH] shorten the x86_64 boot setup GDT to what the comment says


    On Thu, 9 Nov 2006, Alexander van Heukelum wrote:

    > > gdt_48:
    > > - .word 0x8000 # gdt limit=2048,
    > > + .word 0x800 # gdt limit=2048,
    > > # 256 GDT entries
    > >
    > > .word 0, 0 # gdt base (filled in later)
    >
    > The limit should be the offset of the last byte of the gdt table. So
    > I think what was meant was really 0x7ff. Comparing this code with the
    > i386-version, why does x86_64 need 256 entries here, while i386 is happy
    > with just the code-segment and data-segment descriptors?
    >


    Hmm, Andi,

    Should this be more like what is done in x86? Although this isn't a major
    bug or anything, would it be cleaner. For example doing:

    @@ -836,11 +836,15 @@ gdt:
    .word 0x9200 # data read/write
    .word 0x00CF # granularity = 4096, 386
    # (+5th nibble of limit)
    +gdt_end:
    + .align 4
    +
    + .word 0 # alignment byte
    idt_48:
    .word 0 # idt limit = 0
    .word 0, 0 # idt base = 0L
    gdt_48:
    - .word 0x8000 # gdt limit=2048,
    + .word gdt_end - gdt - 1 # gdt limit=2048,
    # 256 GDT entries

    .word 0, 0 # gdt base (filled in

    instead?

    If so, I can send you another patch that does this. Will need to test it
    first.

    -- Steve

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