Descriptor: Difference between revisions
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! DPL |
! DPL |
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| 45,46 || Descriptor Privilege Level || Specifies which |
| 45,46 || Descriptor Privilege Level || Specifies which privilege level a process minimum must have to use this Descriptor. |
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|- |
|- |
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! P |
! P |
Revision as of 17:57, 26 June 2010
Descritors are describing System Segments, Memory Segments and Gates.
System Segment Descriptor
Name | Bit | Full Name | Description | ||||||||||||
---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
Limit | 0..15 | Limit 0..15 | Memory range. | ||||||||||||
BAddr | 16..39 | Base Address 0..23 | Physical address where the memory range begins. | ||||||||||||
Typ | 40..43 | Descriptor Type | Possible types :
| ||||||||||||
S | 44 | Storage Segment | = 0 for System Segments. | ||||||||||||
DPL | 45,46 | Descriptor Privilege Level | Specifies which privilege level a process minimum must have to use this Descriptor. | ||||||||||||
P | 47 | Present | defines if this Descriptor is "present" in memory. s. Paging. | ||||||||||||
Limit | 48..51 | Limit 16..19 | high part of the Limit. | ||||||||||||
AVL | 52 | . | |||||||||||||
0 | 53 | . | |||||||||||||
- | 54 | . | |||||||||||||
G | 55 | . | |||||||||||||
BAddr | 56..63 | Base Address 24..31 | Higher part of the Base Address. |
Memory Segment Descriptor
Name | Bit | Full Name | Description |
---|---|---|---|
Limit | 0..15 | Limit 0..15 | Memory range. |
BAddr | 16..39 | Base Address 0..23 | Physical address where the memory range begins. |
A | 40 | ||
WR | 41 | ||
CE | 42 | ||
EX | 43 | ||
S | 44 | Storage Segment | = 1 for Memory Segments. |
DPL | 45,46 | Descriptor Privilege Level | Specifies which privilege level a process minimum must have to use this Descriptor. |
P | 47 | Present | defines if this Descriptor is "present" in memory. s. Paging. |
Limit | 48..51 | Limit 16..19 | high part of the Limit. |
AVL | 52 | . | |
0 | 53 | . | |
B | 54 | . | |
G | 55 | . | |
BAddr | 56..63 | Base Address 24..31 | Higher part of the Base Address. |
Gate Descriptor
Name | Bit | Full Name | Description | ||||||||||
---|---|---|---|---|---|---|---|---|---|---|---|---|---|
Offset | 0..15 | Offset 0..15 | Lower part of the offset address (also known as pointer). | ||||||||||
Selector | 16..31 | Selector | Selector that specifies the segment of the function to call. | ||||||||||
DWC | 32..35 | Double Word Counter | . | ||||||||||
0 | 36..39 | - | Have to be 0. | ||||||||||
Typ | 40..43 | Gate Type | Possible gate types :
| ||||||||||
S | 44 | Storage Segment | = 0 for gates. | ||||||||||
DPL | 45,46 | Descriptor Privilege Level | Gate call protection. Specifies which Privileg Level the calling process minimum should have. | ||||||||||
P | 47 | Present | can be set to 0 for Paging. | ||||||||||
Offset | 48..63 | Offset 16..31 | Higher part of the offset. |