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22 Oct 2013 In the last section (part 7) of this tutorial for writing your own bootloader for a toy operating system, we looked at protected mode. In particular, we examined the global descriptor table (GDT), which is a structure the CPU uses to determine access to memory and to allow a flat memory model, rathe
The Global Descriptor Table is a construct used by the x86 processor to configure segmented virtual memory. It came long before paging was added to the architecture and as such is a legacy piece of configuration. Very few protected-mode operating systems (which most are) use segmentation. Instead paging is favoured.
21 Nov 2017 Intel defined 3 types of tables: the Interrupt Descriptor Table (which supplants the IVT), the Global Descriptor Table (GDT) and the Local Descriptor Table. Each table is defined as a (size, linear address) to the CPU through the LIDT, LGDT, LLDT instructions respectively. In most cases, the OS simply tells
There are three different type of tables in system: GDT (global descriptor table), LDT (local descriptor table), IDT (interrupt descriptor table). Once the processor is in protected mode, all memory accesses pass through GDT or LDT. We are going to use GDT in this tutorial, GDT can be shared by all tasks as its name implied.
Tutorial about Global Descriptor Table (GDT). How to create entries in GDT and load a GDT table in memory for memory management.
As you know, protected mode is supposed to offer memory protection. By defining how the memory is used, we can insure certain memory locations cannot be modified, or executed as code. The 80x86 processor maps the memory regions based off the Global Descriptor Table (GDT).. The processor will generate a General
The GDT ("Global Descriptor Table") is a data structure used to define the different memory areas: the base address, the size and access privileges like execute and write. These memory areas are called "segments". We are going to use the GDT to define different memory segments: "code": kernel code, used to stored the
23 Jul 2017 The offset is the linear address of the table itself, which means that paging applies. The size is the size of the table subtracted by 1. This is because the maximum value of size is 65535, while the GDT can be up to 65536 bytes (a maximum of 8192 entries). Further no GDT can have a size of 0. The table
6 Mar 2016
The Global Descriptor Table or GDT is a data structure used by Intel x86-family processors starting with the 80286 in order to define the characteristics of the various memory areas used during program execution, including the base address, the size and access privileges like executability and writability. These memory

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