GDT Namespace Reference
Abstracts the GDT that, primarily, contains descriptors to memory segments. More...
Classes | |
| union | SegmentDescriptor |
| Describes the structure of segment descriptors. More... | |
Structs | |
| struct | Pointer |
| Structure that describes a GDT Pointer (aka GDT Descriptor) More... | |
| struct | SegmentDescriptor.__unnamed__ |
Enumerations | |
| enum | Segments { SEGMENT_NULL = 0, SEGMENT_KERNEL_CODE, SEGMENT_KERNEL_DATA } |
| enum | Granularity { GRANULARITY_BYTES = 0, GRANULARITY_4KBLOCK = 1 } |
| Unit of the segment limit. More... | |
| enum | DescriptorType { DESCRIPTOR_SYSTEM = 0, DESCRIPTOR_CODEDATA = 1 } |
| Descriptor type. More... | |
| enum | Size { SIZE_16BIT = 0, SIZE_32BIT = 2, SIZE_64BIT = 1 } |
| Address width. More... | |
Functions | |
| constexpr Pointer | gdt_protected_mode_pointer (protected_mode) |
| constexpr Pointer | gdt_long_mode_pointer (long_mode) |
Detailed Description
Abstracts the GDT that, primarily, contains descriptors to memory segments.
The GDT is a table that primarily contains segment descriptors. Segment descriptors has a size of 8 Bytes and contains the size, position, access rights, and purpose of such a segment. Unlike the LDT, the GDT is shared between all processes and may contain TSS and LDT descriptors. For the kernel, the first entry is required to be a null descriptor and the code and data segments. To support user-mode processes, additional TSS, code, and data segments for ring 3 must be added.
The base address and size of the GDT are written to the GDTR register during boot (via. lgdt).
Enumeration Type Documentation
| enum GDT::Granularity |
| enum GDT::DescriptorType |
| enum GDT::Size |