memory - Assembler: How are segments used in 32bit systems? -

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from know, in days of 16bit pc's had segment registers contain address of each type of segment , access offset ss:[edi], take value contained in edi offset stack segment.

now know in 32bit systems, have gdt (global descriptor table) , ldt (local descriptor table), segments contain index table , offset calculated point right memory address.

is understanding correct?

push dword ptr ss:[ebp+8] ; basicbof.00401000

so statement such mean on 32bit os (xp sp2)?

segment registers contain selectors. each selector index in either global or local descriptor table, plus security level requested.

for example:

mov ds, 0x0000

will put selector 0 table 0 (gdt), level 0 access ds. (this special register, used null pointer testing).

the tables contain base + length information each selector, no longer limited 64k (but might 0 4gb).

the best way learn these reading (freely available) intel processor documents.

edit: link


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