Adam Sulmicki <[EMAIL PROTECTED]> writes: > FWIW, here's summary what I was able to gather so far > > > And the format of the GDT is: > > dummy > > GDT location > > source GDT entry > > target GDT entry > > BIOS CS > > BIOS SS > > ok, I think I got it nailed down, how about the way it is below? > > I'm not quite sure of your interpretation of #2 (GDT location), can you > elaborate? Ie what would it be used for by BIOS. It seems to me like I > already get this info from ES:SI. > > CX = counter of 2-byte words > ES:SI = pointer to to a structure of size of 0x30 which > contains 6 GDT entries. > > 1 0x00 Reserved GDT (all 0's) > 2 0x08 FS & GS GDT (I think this is actually for the indirect link) > 3 0x10 DS (src) GDT > 4 0x18 ES (dst) GDT > 5 0x20 CS (bios) GDT > 6 0x28 SS (bios) GDT > > of all those caller of the interrupt is required to only fill out > #3 and #4 and leave all other blank. > > Because we are not passed indirect link with (size of GDT,ptr to GDT) we > can't use it directly in our LGDT call (after filling out missing info). > We have to either copy it over or add another level of indirection.
I would put the indirect link in table entry 0x00. That way you can trivially call lgdt with the address of the gdt... Table entry 0x01 would do as well, and I think that is what my documentation was suggesting. Eric _______________________________________________ Linuxbios mailing list [EMAIL PROTECTED] http://www.clustermatic.org/mailman/listinfo/linuxbios
