Re: [PATCH] access gdtdesc on segment 0 unconditionally (Re: [PATCH] i386-qemu port)

[Robert Millan]

On Mon, Jun 22, 2009 at 10:52:13PM +0200, Robert Millan wrote:
> I don't think it's possible to use relative addresses
> with this particular instruction.

Uhm sorry, this was silly.  Of course you can use addresses relative to a
segment in lgdt, but this doesn't change the fact that GAS always gives
you absolute ones.

Also, I'm not sure if it's possible to use a 16-bit field in this instruction,
it could be that the field is always 32-bit, even if it's relative to a
segment.  This dump is from the i386-pc kernel.img:

    836f:       2e 67 66 0f 01 15 68    addr32 lgdtl %cs:0x8368
    8376:       83 00 00 

a little-endian 0x00008368 is seen here, indicating the field is 32-bit.

-- 
Robert Millan

  The DRM opt-in fallacy: "Your data belongs to us. We will decide when (and
  how) you may access your data; but nobody's threatening your freedom: we
  still allow you to remove your data and not access it at all."