Global Descriptor Table
This commit adds a GDT. It is used to setup segmentation in memory.
What
A GDT is a table of entries which informs the CPU of the memory segments that the OS implements and their locations.
How
- Allocate some memory for the GDT structure.
- Set the first GDT entry as a null entry.
- Set entries for kernel data and code segments and
user data and code segments.
- Load the table in the CPU with
lgdt assembly command.
- After loading the gdt, the segments have to be reloaded by jumping to new code segment and reloading the data segments.
References