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SubjectRe: x86: asm doubt
Avi Kivity wrote:
> Jeremy Fitzhardinge wrote:
>> In 32-bit mode, moving to a segment register can fault if the
>> underlying GDT/LDT entry is invalid. In 64-bit mode, segment
>> registers are mostly decorative and have no function, and moving
>> arbitrary values into them doesn't fault, making the exception
>> catching unnecessary.
>
> 64-bit mode will in fact fault if an access is made outside the
> GDT/LDT, or of the descriptor is invalid.

Oh, I didn't think it bothered. I guess I'm conflating that with the
fact that it doesn't apply any of the segment properties to memory
accesses. Anyway, in that case the 64-bit code should definitely be
using the standard segment accessors.

J



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