Search results
Results from the WOW.Com Content Network
Global Descriptor Table. The Global Descriptor Table (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.
A segment descriptor may limit access rights, e.g., read only, only from certain rings. The x86 architecture has multiple segmentation features, which are helpful for using protected memory on this architecture. [1] On the x86 architecture, the Global Descriptor Table and Local Descriptor Tables can be used to reference segments in the computer ...
The segment address inside the descriptor table entry has a length of 24 bits so every byte of the physical memory can be defined as bound of the segment. The limit value inside the descriptor table entry has a length of 16 bits so segment length can be between 1 byte and 2 16 byte. The calculated linear address equals the physical memory address.
This allows operating systems to use these segments for special purposes. Unlike the global descriptor table mechanism used by legacy modes, the base address of these segments is stored in a model-specific register. The x86-64 architecture further provides the special SWAPGS instruction, which allows swapping the kernel mode and user mode base ...
Interrupt descriptor table. The interrupt descriptor table (IDT) is a data structure used by the x86 architecture to implement an interrupt vector table. The IDT is used by the processor to determine the memory addresses of the handlers to be executed on interrupts and exceptions. The details in the description below apply specifically to the ...
Cryptographic (e.g. RDRAND, AES-NI) Discontinued (e.g. 3DNow!, MPX, XOP) v. t. e. The x86 instruction set refers to the set of instructions that x86 -compatible microprocessors support. The instructions are usually part of an executable program, often stored as a computer file and executed on the processor.
A general protection fault (GPF) in the x86 instruction set architectures (ISAs) is a fault (a type of interrupt) initiated by ISA-defined protection mechanisms in response to an access violation caused by some running code, either in the kernel or a user program. The mechanism is first described in Intel manuals and datasheets for the Intel ...
There are two such tables, the Global Descriptor Table (GDT) and the Local Descriptor Table (LDT), each holding up to 8192 segment descriptors, each segment giving access to 64 KB of memory. In the 80286, a segment descriptor provides a 24-bit base address , and this base address is added to a 16-bit offset to create an absolute address.