The NX bit (no-execute) is a technology used in CPUs to segregate areas of a virtual address space to store either data or processor instructions. An operating system with support for the NX bit may mark certain areas of an address space as non-executable. The processor will then refuse to execute any code residing in these areas of the address space. The general technique, known as executable space protection, also called Write XOR Execute, is used to prevent certain types of malicious software from taking over computers by inserting their code into another program's data storage area and running their own code from within this section; one class of such attacks is known as the buffer overflow attack.
The term NX bit originated with Advanced Micro Devices (AMD), as a marketing term. Intel markets the feature as the XD bit (execute disable). The MIPS architecture refers to the feature as XI bit (execute inhibit). The ARM architecture refers to the feature, which was introduced in ARMv6, as XN (execute never).[1] The term NX bit itself is sometimes used to describe similar technologies in other processors.
^"ARM Architecture Reference Manual" (PDF). ARM Limited. pp. B4-8,B4-27. Archived from the original (PDF) on 2009-02-06. APX and XN (execute never) bits have been added in VMSAv6 [Virtual Memory System Architecture]
The NXbit (no-execute) is a technology used in CPUs to segregate areas of a virtual address space to store either data or processor instructions. An operating...
page table entry as a no-execute or "NX" bit, indicating that code cannot be executed from the associated page. The NX feature is also available in protected...
could be used by people worried about damaging the die. The No Execute bit (NXbit) supported by Windows XP Service Pack 2 and future versions of Windows...
APU features table All models support: MMX, SSE, SSE2, Enhanced 3DNow!, NXbit, AMD64 All models with OPN ending in AG support up to Registered PC2700...
controller, the HyperTransport link, and AMD's "NXbit" feature. In the second half of 2005, AMD added 64-bit support (AMD64) to the Sempron line. Some journalists...
multiprocessing multi-user pure 32-bit memory access — earlier, consumer-oriented versions, Windows 3.1x and Windows 9x, were 16-bit/32-bit hybrids Multi-architecture...
also introduced the NXbit, which offers some protection against security bugs caused by buffer overruns. As a result of AMD's 64-bit contribution to the...
XD, a user experience design software developed by Adobe Systems XD bit (or NXbit), a security-related computer technology for x86 and x64 processors...
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