Suvarna Garge (Editor)

Segment descriptor

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In memory addressing for Intel x86 computer architectures, segment descriptors are a part of the segmentation unit, used for translating a logical address to a linear address. Segment descriptors describe the memory segment referred to in the logical address. The segment descriptor (8 bytes long in 80286) contains the following fields:

  1. A segment base address
  2. The segment limit which specifies the segment size
  3. Access rights byte containing the protection mechanism information
  4. Control bits

x86-64

In X86-64, the code segment descriptor has the following form:

Where the fields stand for:

Base Address 
32 bit starting memory address of the segment
Segment Limit 
20 bit length of the segment. How exactly this should be interpreted depends on other bits of the segment descriptor.
DPL 
descriptor-privilege level

References

Segment descriptor Wikipedia
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