The gdt is the global descriptor table that contains entries for
segments which are determined by the kernel code. These entries are
typically filled in during early phases of the kernel startup code.
Check the file head.S in the source tree for the definitions of the gdt
"lgdt" basically loads the global descriptor table register, it takes
as arguments the size of the GDT and it's base address.
>
> The momenclature I have come across is "Global Descriptor Table"
> as used for Extended Memory. I think that "lgdt" moves data from
> the specified address to the 'standard' address for the GDT (0800H ?).
>
> "_gdt" also shows up with an '.external' statement in several files and
> is commented as an 'imported' variable.
>
> Seems like it must be defined as an exported variable somewhere.
> Darned if I can find it...
>
> -Norm
>
> On Sun, 3 Oct 1999, Baranek wrote:
>
> > I think GDT is intel's name of the pointer to the page's directory.
> >
> >
> > > In /usr/src/kernel/klib88.s in the 'real2prot' code routine
> > > is the following:
> > >
> > > "lgdt _gdt+GDT_SELECTOR"
> > >
> > > 'lgdt' loads 6 bytes from memory starting at the address represented by
> > > '_gdt+GDT_SELECTOR', as best I understand it.
> > >
> > > 'GDT_SELECTOR' is defined in protect.h .
> > >
> > > However, despite extensive searching with 'find' and 'grep',
> > > I have been totally frustrated in locating the definition of
> > > "_gdt".
> > >
> >
> >
> >
>
>
>
