Editing General protection fault (section)

{{Short description|Fault initiated by x86 processors due to an access violation}}
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{{technical|date=June 2015}}
{{refimprove|date=January 2017}}
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{{multiple image
 | align = right
 | direction = vertical
 | width = 220
 | image1 = Unrecoverable Application Error.png
 | alt1 = Error message in a white dialog box stating "UNRECOVERABLE APPLICATION ERROR: Terminating current application."
 | caption1 = Generic error message for a general protection fault (Unrecoverable Application Error) in [[Windows 3.0]]
 | image2 = General Protection Fault example in Windows 3.1.png
 | alt2 = Error message for a general protection fault in Windows 3.1x
 | caption2 = Example error message for a general protection fault in [[Windows 3.1x]]
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A '''general protection fault''' ('''GPF''') in the [[x86]] [[instruction set architecture]]s (ISAs) is a [[Fault (computing)|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 (operating system)|kernel]] or a user program. The mechanism is first described in Intel manuals and datasheets for the [[Intel 80286]] CPU, which was introduced in 1983; it is also described in section 9.8.13 in the [[Intel 80386]] programmer's reference manual from 1986. A general protection fault is implemented as an interrupt ([[interrupt vector|vector]] number 13 (0Dh)). Some [[operating system]]s may also classify some exceptions not related to access violations, such as illegal [[opcode]] exceptions, as general protection faults, even though they have nothing to do with memory protection. If a CPU detects a protection violation, it stops executing the code and sends a GPF interrupt. In most cases, the operating system removes the failing [[Process (computing)|process]] from the execution queue, signals the user, and continues executing other processes. If, however, the operating system fails to catch the general protection fault, i.e. another protection violation occurs before the operating system returns from the previous GPF interrupt, the CPU signals a [[double fault]], stopping the operating system. If yet another failure ([[triple fault]]) occurs, the CPU is unable to recover; since 80286, the CPU enters a special halt state called "Shutdown", which can only be exited through a [[hardware reset]]. The [[IBM Personal Computer AT|IBM PC AT]], the first [[PC-compatible]] system to contain an 80286, has hardware that detects the Shutdown state and automatically resets the CPU when it occurs. All descendants of the PC AT do the same, so in a PC, a triple fault causes an immediate system reset.