Describes the structure of segment descriptors. More...
#include <gdt.h>
Public Member Functions | |
| constexpr | SegmentDescriptor (uint64_t val=0) |
| !< Merged value; useful for debugging | |
| constexpr | SegmentDescriptor (uintptr_t base, uint32_t limit, bool code, int ring, Size size) |
| Constructor for a code/data GDT entry. | |
Public Attributes | ||
| struct { | ||
| uint64_t : 40 | ||
Ignored (set via limit_low and base_low ) | ||
| bool code_accessed: 1 | ||
| If set, the code segment was used since the last reset of this value. | ||
| bool readable: 1 | ||
| If set, the code is readable (otherwise only executable) | ||
| bool conforming: 1 | ||
If set, the execution of code from this segment is only allowed when running at a privilege of numerically less than or equal to privilege_level (i.e. the executor has the same or higher privileges). However, the executor's privileges remain unchanged. For nonconforming code segments (i.e., conforming is set to 0), execution is allowed only if the privileges are equal. Execution will cause a GPF in case of privilege violation. | ||
| bool code: 1 | ||
Has to be set to true | ||
| uint64_t : 9 | ||
Ignored (set via privilege_level ... available) | ||
| Size operation_size: 2 | ||
Default address width (custom field bit) | ||
| uint64_t : 0 | ||
Remainder ignored (set via base_high) | ||
| }; | ||
| Fields specific for Code Segment (for debugging purposes) | ||
| struct { | ||
| uint64_t : 40 | ||
Ignored (set via limit_low and base_low) | ||
| bool data_accessed: 1 | ||
| If set, the data segment was used since the last reset of this value. | ||
| bool writeable: 1 | ||
| If set, data is writable (otherwise read only) | ||
| bool expand_down: 1 | ||
| Growing direction for dynamically growing segments. | ||
| bool notData: 1 | ||
Has to be cleared (false) | ||
| uint64_t : 9 | ||
Ignored (set via privilege_level ... available) | ||
| uint64_t reserved: 1 | ||
Reserved, always set to 0! | ||
| bool big: 1 | ||
Size of the stack pointer (false = 16 bit, true = 32 bit) More... | ||
| uint64_t : 0 | ||
| Remainder ignored. | ||
| }; | ||
| Fields specific for Data Segment (for debugging purposes) | ||
| struct { | ||
| uint64_t : 40 | ||
Ignored (set voa limit_low and base_low) | ||
| enum Gate gate: 3 | ||
| TSS or LDT entry. | ||
| bool not16bit: 1 | ||
false for 16-bit, true for 32-bit/64-bit | ||
| uint64_t : 0 | ||
| Remainder ignored. | ||
| }; | ||
| Fields specific to the Task State Segment. | ||
Detailed Description
Describes the structure of segment descriptors.
A data structure that contains size, position, access rights, and purpose of any segment. Segment descriptors are used in both the GDT, as well as in LDTs.
Constructor & Destructor Documentation
◆ SegmentDescriptor() [1/2]
|
inlineconstexpr |
!< Merged value; useful for debugging
Constructor for a specific value
◆ SegmentDescriptor() [2/2]
|
inlineconstexpr |
Constructor for a code/data GDT entry.
- Parameters
-
base Base Address of segment limit Size of segment code Code or data segment ring Privilege level size Address width
Member Data Documentation
◆ [struct]
| struct { ... } GDT::SegmentDescriptor |
Fields specific for Code Segment (for debugging purposes)
◆ [struct]
| struct { ... } GDT::SegmentDescriptor |
Fields specific for Data Segment (for debugging purposes)
◆ [struct]
| struct { ... } GDT::SegmentDescriptor |
Fields specific to the Task State Segment.
- See also
- ISDMv3, 7.2.2; TSS Descriptor
◆ __pad0__
| uint64_t GDT::SegmentDescriptor::__pad0__ |
Ignored (set via limit_low and base_low )
Ignored (set voa limit_low and base_low)
Ignored (set via limit_low and base_low)
◆ __pad1__
| uint64_t GDT::SegmentDescriptor::__pad1__ |
Ignored (set via privilege_level ... available)
Remainder ignored.
◆ __pad2__
| uint64_t GDT::SegmentDescriptor::__pad2__ |
Remainder ignored (set via base_high)
Remainder ignored.
◆ big
| bool GDT::SegmentDescriptor::big |
Size of the stack pointer (false = 16 bit, true = 32 bit)
- Warning
- Has a different meaning in case expand_down is set to
1.
The documentation for this union was generated from the following file:
- machine/gdt.h
