Segmentation in long mode?

Question

reverse engineering

Written in Russian and English. Segment registers in x64 except for GS and FS are not used and are forced to 0.
Open the first application in x64dbg.

why is that ?

Answer 1

Written in Russian and English. Segment registers in x64 except GS and FS are not used and are forced to 0.

This is some kind of ambiguous and inaccurate quote. Here is what Intel Software Developer Manual 3.7.4.1 "Segmentat..." writes :
Those. the base address of the segments accessed via cs/ds/es/ss is zero, but not the selector values ​​themselves. The base address, remember, is a field in the GDT/LDT records. The selector (the value in the segment register) selects the requested privileges (lower two bits), the table type (GDT/LDT, the third bit from the end), and the table entry number (all other bits).
Agree, this is not at all what you expected?
Looking at your picture, it can be said that the code from the segment in the sixth entry in the GDT is executed with the privileges of the third protection ring, and the data access through ds / es / ss / gs is carried out through the segment in the fifth entry in the GDT with the privileges of the third ring.