Chapter 40 Flashcards
1
Q
What is GDT
A
GDT is an array-formatted table of descriptors where each descriptor is an 8byte entry
2
Q
What is GDTR
A
The base and limit of GDT is stored in a 48bit register called the GDTR
3
Q
What is LGDT
A
It’s a special instruction of GDTR register
4
Q
What is null descriptor
A
The first entry of the GDT must always be zero. It is called the null descriptor.
5
Q
What is limit of GDT
A
8191 + null descriptor
6
Q
Which bit defines the limit of GDT
A
G
7
Q
What is DPL
A
descriptor privilege level
8
Q
What is role of B (big) bit
A
B (big) bit tells that if this data segment is used as stack SP or ESP.
9
Q
What is Gate A20
A
Its a work around in which, BIOS call will simply enable it to open the whole memory for us.
