x86-64: Segment Overrides in 64-Bit Mode

Segment Overrides in 64-Bit Mode. In 64-bit mode, the CS, DS, ES,

and SS segment-override prefixes have no effect. These four

prefixes are not treated as segment-override prefixes for the

purposes of multiple-prefix rules. Instead, they are treated as

null prefixes.

The FS and GS segment-override prefixes are treated as true

segment-override prefixes in 64-bit mode. Use of the FS or GS

prefix causes their respective segment bases to be added to the

effective address calculation. See “FS and GS Registers in 64-

Bit Mode” in Volume 2 for details.





Правильно ли я понял, что если написать

Код (Text):

1. SEGFS
2. SEGCS
3. MOV RAX,[RAX]

то префикс CS не отменит действие префикса FS и эффективный адрес будет rax+fs.base?

 

Правильно это или нет, но я понял точно так же